platinum metals review

UK ISSN 0032-1400

PLATINUM METALS REVIEW

A quarterly survey of research on the platinum metals and of developments in their application in industry

VOL. 32 JULY 1988

Contents

Shape Memory Effects in Iron-Platinum Alloys

Wiring Up Microelectronic Implants

Platinum 1988

Cathodic Protection in the Arctic

Homogeneous Catalyst Research Kit

Car Exhaust Pollution Control

Monitoring Impurities in Water

Oxidation Resistant Iridium Alloys

Palladium-Rare Earth Alloys

Viacheslav Vasil’evich Lebedinskii

Abstracts

New Patents

NO. 3

Communications should be addressed to The Editor, Platinum Metals Review

Johnson Matthey Public Limited Company, Hatton Garden, London ECl N 8 E E

118

I I 0

119

118

122

123

129

129

130

141

148

160

Shape Memory Effects in Iron-Platinum Alloys THEIR ASSOCIATION WITH MARTENSITE TRANS FORMATIONS

By R. Oshima and S. Muto

and T. Hamada

Faculty of Engineering Science, Osaka University, Toyonaka. Japan

Tanaka Kikinzoku Kogyo K.K., 26 Suzukawa. Isehara Kanagawa. Japan

The mode of martensite transformation in iron-platinum alloys near the stoichiometric Fe,Pt composition depends on the degree of ordering in the austenite phase, which has a LI type structure (I -4). Disordered alloys quenched from high temperatures transform non-thermoelastically from face-centred-cubic (f.c . c .) austenite to body-centred-cubic (b .c .c .) martensite, as do many other ferrous alloys which undergo martensite transformation. With increasing order, however, the transformation becomes thermoelastic, and the alloys begin to show the shape memory effect. That is to say, a plastically deformed martensite crystal returns to the original shape of the parent phase upon heating to a temperature above the Af at which the reverse transformation completes.

A demonstration of the shape memory effect

in a Fe, Pt alloy is shown in Figure I. A ribbon of an ordered iron-24 atomic per cent platinum alloy was deformed at room temperature into a symbol approximating to the form of the script “Pt”. This was then roughly straightened in a liquid nitrogen bath, as seen in Figure Ib, before being warmed to room temperature. With increasing temperature the symbol gradually reverted to its original shape; the sequence being shown by the series of photo- graphs in Figure I. Some other characteristics such as transformation temperature, volume change on transformation, the tetragonality of the martensite and the mechanical strength of the austenite are also influenced by the degree of ordering.

In 1978 a face-centred-tetragonal (f.c.t.) phase was found in an ordered Fe,Pt alloy before the transformation to body-centred-

Fig. 1 The shape memory effect of an ordered iron-24 atomic per cent platinum alloy is demonstrated by this sequence which shows (a) original shape at room temperature, (b) deformation at 77K, and (c)-(f) continuing shape recovery upon heating to 300K

Platinum Merals Rev., 1988, 32, (3), 110-118 110

tetragonal (b.c.t.) martensite took place (5). This f.c.t. phase was interpreted as being a transitional phase leading to the b.c.t. phase. More recently one of the present authors found similar successive martensite transformations from f.c.c. through f.c.t. to b.c.t. in iron- palladium alloys containing approximately 30 atomic per cent palladium (6). However, it is now concluded that the f.c.t. phase is not a transitional phase in the f.c.c.-b.c.t. martensite transformation but a stable low temperature phase, since in the composition range 30.6 to 32.0 atomic per cent palladium it never trans- forms to b.c.t. martensite on further cooling (7).

In iron-platinum and iron-palladium alloys the f.c.c.-f.c.t. transition, unlike the f.c.c.- b.c.t. transformation, is nearly always second order because of the small volume change occurring on transformation and the gradual development of tetragonality with decreasing temperature. Furthermore, an anomalous contrast effect, the so called “tweed (contrast) pattern”, appears as a precursor phenomenon in the austenite, when examined in an electron microscope (8). The tweed pattern is observed as linear contrast variations which lie nearly parallel to the traces of {I 10) planes and obey extinction rules consistent with the shear dis- placements on {I 10) planes in the < I To> direction. In this case the tweed is interpreted as the assembly of small nuclei of the f.c.t. phase. Hence, an Fe,Pt alloy is also an interesting material from the viewpoint of the premarten- site effect.

In this review we report on several characteristics of Fe Pt shape memory alloys obtained so far, which are associated with the martensite transformations.

Experimental Conditions Iron-platinum alloys containing from 22.6 to

26.5 atomic per cent platinum were prepared by melting in an induction furnace. After homogenisation at 1373K for b k s , they were cold-rolled to the required thickness. Ordering treatments were carried out at 923K for selected periods of time and specimens with

various degrees of ordering were obtained. Specimens for optical and transmission electron microscopy were made by a jet electropolishing technique, using a mixed solution of 90 per cent acetic acid and 10 per cent perchloric acid. The progress of the martensite transformation was followed by observing the surface relief of the martensite under an optical microscope equipped with a cooling stage. X-ray diffractometry was used to determine the long range order parameter, “S”, by comparing the intensity of the {220} fundamental peak with that of the {I 10) superlattice, and also to verify the appearance of a f.c.t. phase. The transformation temperatures of b.c.t. martensite were determined by electrical resistance measurements.

Results and Discussion Summarised data obtained during the present

study by X-ray diffraction, optical microscopy and electrical measurements are given in the Table. The variations in resistivity of the specimens during temperature cycling are shown in Figures 2(a)-(g). The sharp drop in resistance corresponds to the temperature M S ~ . ~ , ~ . , at which transformation to b.c.t. com- mences, while no detectable changes appeared during the transformation to f.c.t. However, a recent precise examination of electrical resistance of an Fe,Pt alloy indicated a slight change at the f.c.c.-f.c.t. transition. Figures 2(a)-(d) indicate that the resistance change at M s ~ , ~ , ~ , becomes less precipitous with ordering of the austenite, that is to say the “burst effect” is reduced and the width of the transformation hysteresis loop is decreased considerably.

A thermoelastic martensite transformation is generally accepted as a transition in which the chemical driving force can be balanced by the elastic strain energy generated by the transformation. These facts indicate that the ordering is responsible for the thermoelasticity of the transformation in these alloys. On the other hand, the f.c.c.-b.c.t. martensite transformation of an ordered iron-22.6 atomic per cent platinum alloy was rather “burst-like”, as seen in Figure 2(g), but it still exhibited a good shape memory effect, presumably due to the

Platinum Metals Rev., 1988, 32, (3) 111

small temperature hysteresis of the forward and reverse martensite transformation. This suggests that the suppression of the “burst effect” is not an essential factor for thermoelasticity.

Although the shape memory effect in the

iron-platinum system has been reported to be associated with the f.c.c.-b.c.t. thermoelastic martensite transformation of the ordered alloys, the f.c.c.-f.c.t. transition is also found to relate to the shape memory effect in this alloy system

100 150 200 250 300

( c ) 923K for Bh

. . *: . * . . * . * *

100 150 200 250 300

1.

..a+ . . 100 150 2 0 0 250 300

TEMPERATURE I K

(e) Fe-25.9rt :/.Pt disorder *..*-

100 150 200 250 300

( f 1 Fe-26.2at:I.Pt disorder

100 150 200 250 300

( g ) Fe-22.6at:I.Pt 923K for 16Bh *..*

.* + ..::”. I .* . .

. ,.*:*** 1. f

100 150 200 250 300 TEMPERATURE K

Fig. 2 Electrical resistance-temperature curves for various iron-platinum alloys; the electrical resistance being in arbitrary unite. The arrows indicate the M s temperature


Fig. 3 X-ray diffractometer traces showing changes in the { l l O } and {220} anstenite peaks of specimen No. 6 (S = 0.78) with temperature: (a) at 300K, (b) 77K and (c) at 300K after being cooled to 77K

II CoKa

I ( C )

( b )

38 4 0 4 2 8 2 84 86

201(rr1180) rod

(9). Figure 3 shows X-ray diffraction results obtained on an ordered iron-24.9 atomic per cent platinum alloy (S=0.78). Both the {IIO} and {220} peaks split into two components at 77K, and then return to the original peaks on heating to 3wK. It was found that the peak splitting corresponded to the f.c.c.-f.c.t. martensite transformation, and that the transition showed thermoelastic behaviour.

Figures 4(a) and (b) are optical micrographs

showing the surface relief of f.c.t. and b.c.t. martensite, respectively. Besides the difference in morphology, the appearance of the surface reliefs is also characteristic of f.c.t. and b.c.t. martensite. The surface relief bands of f.c.t. martensite gradually appeared over the whole area of a crystal grain with decreasing temperature, which indicates a second order like feature of the transition, whereas the surface features on the b.c.t. martensite were


formed intermittently, and the temperature intervals between the successive nucleations of b.c.t. martensite were sometimes more than ten degrees.

The Table records that a f.c.t. phase was found in a disordered alloy, specimen No. 7. This alloy shows the shape memory effect associated with the f.c.c.-f.c.t. transition. The information in the Table suggests that the f.c.t. phase is observed only in specimens with low M s ~ , ~ , ~ . , irrespective of the ordering of the austenite.

Tensile tests were carried out on polycrystalline specimens containing from 24.0 to 26.5 atomic per cent platinum, and with grain sizes of several tens of a micrometre. It was im- possible to prepare tensile test pieces containing less than 24 atomic per cent platinum, because of their hardness and brittleness. Examples of stress-strain curves are shown in Figure 5 . Most

Fig. 4 The surface morphologies of (a) above, f.c.t. martensite (Specimen No. 6 at 77K), and (b) below, b.c.1. martensite (specimen No. 3 at 77K), showing characteristic differences

of the specimens containing less than 25 atomic per cent platinum fractured before yielding, but those with more than 25 atomic per cent did not rupture until they had reached an elongation of about 20 per cent. In the former, transmission electron micro-

scopy showed the presence of numerous microcracks along the grain boundaries. These were possibly caused by processing, indicating that strengthening of the grain boundaries would be indispensable if the materials were to be used industrially.

The recovery force caused by the reverse martensite transformation from f.c.t. to f.c.c. was examined for an as-quenched and slightly ordered iron-26.5 atomic per cent platinum alloy, as shown in Figure ~ (c ) . When the specimen was unloaded after an elongation of 3 per cent at 77K, about 1.3 per cent strain remained at the same temperature. On heating to 3ooK, a stress of nearly 2ooMPa was generated, and the strain was completely restored by subsequent unloading.

In-situ observation of the martensite transformation in iron-platinum alloys was carried out using a double tilting cooling stage of a


1 2 3 5 10 15 20 25

TENSILE STRAIN, pcr cent

1 2 3 4

Fig. 5 Stress-strain curves of iron-platinum alloys show that: (a) a specimen (No. 3) containing less than 25 atomic per cent platinum fractured before yielding, while (b) one containing more (No. 7) did not rupture until an elongation of more than 20 per cent was reached. The recovery of an asquenched and slightly ordered specimen (No. 7) is shown as (c), the conditions being: (i) loaded at 77K, (ii) unloaded at 77K, (ii) heated to 300K, and (iv) unloaded at 300K

transmission electron microscope. A characteristic precursor effect, the tweed pattern, appeared at a certain temperature range immediately before the f.c.c.-f.c.t. martensite transformation. The tweed pattern was observed under dynamical reflection conditions with especially strong contrast near extinction contours.

An example of the tweed pattern near a <002> extinction contour is shown in Figure 6, where the two directional striations occur along the traces of the {oIT} and {IoT} planes. In the selected area diffraction patterns appear diffuse streaks perpendicular to the striations. It was found that the tweed pattern in iron-platinum alloys is associated with the f.c.c.-f.c.t. martensite transformation, irrespective of the ordering

of the austenite, and is due to differences in the amounts of strain resulting from the formation of fine tetragonally distorted f.c.t. martensite embryos in the f.c.c. austenite. In some specimens a b.c.t. martensite transformation was also observed in-situ. It is well-known that the b.c.t. martensite transformation of ordered Fe,Pt alloys is thermoelastic, and that the martensite is made up of thin plates. In the present experiment, however, the austenite- martensite interface was not straight, but curved presumably due to a thin foil effect. Occasionally, the b.c.t. martensite Transforma- tion took place prior to the f.c.c.-f.c.t. martensite transformation, strongly suggesting that the f.c.t. martensite is not a transitional phase to b.c.t. martensite. In such a case, it was


observed that the f.c.t. martensite nucleated and grew at the f.c.c.-b.c.t. interfaces, and the tweed pattern appeared in the untransformed austenite, as shown in Figure 7. With decreasing temperatures an increasing number of (01 I)

internal twins were introduced in the f.c.t. martensite. It seemed that the appearance of the f.c.t. martensite suppressed the growth of b.c.t. martensite. It was also found that the (112) internal twins of b.c.t. martensite were not always inherited from (011) internal twins of f.c.t. martensite, which was expected from the crystallography, as shown in Figure 8.

Fig. 6 Dark field image and diffraction pattern of an area of specimen No. 4 at 130K. The former ehowe the typical tweed pattern, with striations in two direc- tions. near a <002> extinction contour

These facts indicate that f.c.t. martensite is not an intermediate phase to b.c.t. martensite.

Prospects for the Use of the Shape Memory Effect

No practical use of the shape memory effect of the iron-platinum alloy system has been reported so far.

When compared with commercial shape memory alloys such as titanium-nickel and copper-based beta alloys which are used at above room temperature, one of the dis- advantages of the iron-platinum alloys is that

Summary of the Experimental Results

thermoelastic


I Summary of the Experimental Results

Composition Appearance Mode of Specimen (atomic per Ordering time, of f.c.t., transformation I number lcent platinum) 1 at 923K I M s ~ , ~ . ~ , I by X-ray 1 of f .c.c. -b.c. t .

18ks 190K no I 1

l?i 24.2 11 260ks 163K

600ks 110K at 114K

thermoelastic

5 1 Oks 154K ? thermoelastic

6 43ks <77K at 110K -

7 disordered 123K at 130K non-thermoelastic

8 28ks <77K no

25.0

26.5 -

28ks I 183K I no

Fig. 7 The stress-induced f.c.1. phase observed near the austenite- b.c.t. martensite interface at 130K is shown (specimen No. 3)

the characteristic transformation temperatures are too low. As long as the intention is to utilise the shape memory effect associated with the LI -b.c.t. thermoelastic martensite transformation, it is difficult to raise the transformation temperature significantly. Any treatment to increase the transformation temperature will cause the destruction of the ordered structure, which results in degradation of the shape memory effect. From another point of view, however, the transformation temperatures, that is, the shape recovery temperatures of the alloys, are variable, depending on the degree of ordering in the austenite, as shown in Figure 2.

Accordingly, the required shape recovery

Fig. 8 Both f.c.t. and b.c.t. martensite was observed at 130K. on specimen No. 3, indicating that the former is not an intermediate phase to the latter

temperature can only be controlled by varying the heat treatment of the alloy if large amounts of the shape recovery are not needed. Since the ordered Fe F’t alloys possess high mechanical strengths and also high resistance to corrosion they may be applicable to actuators, especially those required to operate in corrosive environments at low temperatures.

Another problem could result from inter- granular fracture of the material during fabrication. However, this might be solved by grain refining, although the rate of shape recovery could be sacrificed. On the other hand, M S ~ , ~ , ~ , temperatures are not greatly influenced by the degree of ordering, suggesting the possibility of raising the transformation temperature. Actually, Msr,,,,, temperatures of iron- palladium alloys containing about 30 atomic per cent palladium are close to room temperature. Nevertheless, the shape recovery associated with the f.c .c. -f.c. t. thermoelastic martensite transformation is smaller than that for the LI b.c. t. transformation.

Conclusions The shape memory effect of the iron-

platinum alloys is by no means inferior to that of the commercially available titanium-nickel and copper-based alloys, although the range of use is limited to low temperatures, as shown in Figure I. Accordingly, the development of special applications for these alloys will be the subject of future investigations.


References I D. P. DunneandC. M. Wayman, Metall. Trans., 6 R. Oshima, Scr. Metall., 1981, 15, 829 1973, 4, I37 7 M. Sugiyama, R. Oshima and F. E. Fujita, Trans.

2 M. Umemoto and C . M. Wayman, Metall. Trans., JIM., 1984, 25 , 585 1978, 9A, 891 8 M. Sugiyama, R. Oshima and F. E. Fuiita,3.Jp.

3 T. Tadakiand K. S h e , Scr. Metall., 1975,9,771 Inst. Met., 1984, 48, 881 4 G. Hausch, 3. PhYS. 3fJn.9 1974, 37, 819 9 R. Oshima, S. Sugimoto, M. Sugiyama, T. 5 M. Foos, C. Frantz and M. Gantois, Scr. Metall., Hamada and F. E. Fuiita, Trans. J IM. , 1985, 26, 1978, 12, 795 523

Wiring Up Microelectronic Implants Fine platinum and platinum-iridium wires,

when insulated with silicone rubber, PTFE or a synthetic enamel, are suitable conductor materials for wiring up microelectronic implants, being neutral with regard to body tissues and the fluids they come into contact with. Of the possible ways of making connec- tions to such wires, mechanical clamping is too clumsy, soldering is generally mechanically weak, while welding is inconvenient and may damage the wire; fortunately, a recent technical

Neurological Prosthesis Unit describes a microbrazing process which enables strong bonds to be made (“Technical Note: Microbrazing Fine Platinum Wires”, P. E. K. Donaldson, J. Med. Eng. Technol., 1988, 12, (I), 24-25).

Pure gold, in the form of a helix of 75pm diameter wire, is threaded over the platinum wires to be joined and is then heated to a temperature between 1063 and 1755OC. This may be done in a variety of ways, and the circuit of a suitable micro-arc generator for form-

note %om the - Medical Research Council’s ing the braze is given.

Platinum The latest annual survey of platinum,

palladium and the other four metals of the platinum group was published by Johnson Matthey during May. Compiled with the co-operation of many people in the platinum industry throughout the world, “Platinum 1988” summarises events that affected the supply, demand and usage of the platinum group metals during 1987, and considers the outlook for 1988, and beyond.

Supplies of primary platinum were above 3 million ounces troy for the first time, aided by higher than usual exports from the U.S.S.R. Nonetheless these were insufficient to meet a record demand, which resulted, in the main, from increased use by the autocatalyst and jewellery industries. The demand for palladium was also at a record level, due to increased consumption by the electronics and dental sectors of the market. As with platinum, a deficit in the supply was met by withdrawal from world-wide stocks.

A review of exploration and mining

developments is included. In South Africa expansion programmes and new mines have been announced, based on the vast reserves of the Bushveld Complex, where the UG2 Reef is of increasing importance. However, as far as is known, none of the projects outside that country are located on geological formations of comparable plati- niferous potential.

Acknowledging the importance of Japan as a major platinum importing country, “Platinum 1988” devotes a chapter to the demand for platinum within that country. While the requirement for platinum has grown with industrial expansion in Japan, the associated creation of wealth has led to a situation where the amount of platinum being used for investment, jewellery and decorative purposes now exceeds that taken by the industrial sector.

Requests for copies of “Platinum 1988” should be sent to the compilers: Messrs. G. G. Robson and F. J. Smith, Johnson Matthey P.L.C., New Garden House, 78 Hatton Garden, London ECIN 8JP.


Platinum 1988

Cathodic Protection in the Arctic IMPRESSED CURRENT SFSTEMS USE PLATINISED ANODES

Corrosion of steel structures in Arctic waters can be even more severe than in warmer environments. I t has now been reported that with careful attention to detail during all stages of design, fabrication, installation and operation, impressed current cathodic protection systems, incorporating platinised anodes, can provide an economic and effective means of preventing corrosion on both ships and off-shore structures.

Steel structures partially submerged in sea water may suffer from localised preferential corrosion due to a variety of factors including the joining together of metals with different electrochemical characteristics, non-uniform protection by paint coatings and variable composition of the surrounding water. An appropriate cathodic protection system using either sacrificial anodes or an impressed current can

overcome such difficulties. While sacrificial anodes corrode in preference to the structure to which they are attached, in an impressed current system the current produced by the natural electrochemical corrosion process is suppressed by a current from an external power source, which is dissipated over the surface of the structure by means of strategically positioned electrodes made from inert materials such as

The ice-breaking ship “Terry Fox” is one of several vessels operated by BeauDril Ltd. in the Beaufort Sea to be protected against corrosion by an Aquamatic impressed current system, employing platinised titanium anodes. The anodes and the reference electrodes are all recessed into the hull to avoid mechanical damage. To provide proper protection for the propeller, the shaft and the bearings, it is necessary to ensure that there is adequate electrical connection between the propeller shaft and the hull

Platinum Metals Rev., 1988, 32, (3), 119-122 119

platinum or iridium supported on titanium or niobium.

The use of impressed current cathodic protection systems to prevent corrosion damage to the underwater hulls of ships was pioneered by the Bureau of Ships of the U.S. Navy Depart- ment in the 1950s (I, 2) , and since that time such systems have found growing application for the protection of steel hulls of ships (3, 4). The ever-increasing capital and maintenance costs of both ships and marine structures have encouraged the development of sophisticated cathodic protection systems which can econ- omically and effectively protect bare, or partially coated, steel structures under a wide variety of climatic and operating conditions.

Arctic Ice-Breakers One such system is the Wilson Walton Inter-

national Aquamatic system, which was selected for installation on the ice-breaking vessel “Can- mar Kigoriak” which is operated in the Arctic Ocean by Canadian Marine Drilling, a division of Dome Petroleum. Traditionally, paint and sacrificial zinc anodes have been used to protect the external surface of ice-breaker hulls, but these have not been totally successful, due, in part, to the abrasive action of the ice. The Wilson Walton Aquamatic system incorporates platinised anodes. These are fed with a continually variable electric current, the power being determined by signals from a number of zinc reference electrodes which are used to monitor the electrochemical conditions on the hull. Thus optimum protection of the steel can be achieved however the electrochemical conditions vary.

Following successful trials, the Aquamatic system has now been fitted to several other vessels engaged on ice-breaking and oil exploration work in the Beaufort Sea.

There is a major structural difference between ships’ hulls and conventional off-shore oil drilling and production rigs. While the outer surfaces of the former are made up of flat plates, a conventional rig consists of a complex lattice of tubular components, and this adds to the difficulty of designing, engineering and in-

stalling impressed current systems to protect them against corrosion. However, the more recent development of semi-submersible drilling rigs and tension-leg production platforms, which are of plate rather than tubular construc- tion, provides an opportunity for the advan- tageous use of impressed current cathodic protection systems.

The Movable Rig “Molikpaq” What is believed to be the first impressed

current system to be used to protect an off- shore rig working in ice-covered Arctic waters was fitted to the caisson drilling unit “Molik- paq” during August and September 1987. Designed to drill in water I 5 to 40 metres deep, the flat-bottomed caisson is floated to location and then sunk onto a prepared base on the sea- bed, where it is filled with sand or gravel aggre- gate to enable it to withstand the sideways force of the winter sea ice flow ( 5 ) .

In plan, the caisson takes the form of a square with 111 metre sides, but with the corners chamfered off. When it was constructed, all external steel surfaces below the water line were coated with a 250 micrometre thick layer of coaltar epoxy paint. However, when the rig was moved after only two years of operation, the steel was bare at and below the water line, and overall some 50 per cent of the coating had been lost due to the abrasive action of ice. With the rig expected to have a life of 20 years, the de- cision was then taken to fit a Wilson Walton International cathodic protection system.

A particular advantage of an impressed cathodic protection system is that the current can be adjusted automatically in response to any changing environmental or operational condition, due to factors such as variations in sea water temperature and salinity, or changes in the area of the exposed steel resulting from deterioration of painted surfaces, and thus the level of cathodic protection can be continually optimised.

Platinum electrodeposited on titanium was selected as the anode material because of its known properties in the environmental conditions expected (6), which included sea water


The stationary caisson rig “Molikpaq” has horizontal loads of up to 500 pounds per square inch exerted on the hull as ice, four metres or more in thickness, attempting to flow past-due to the rotation of the earth-piles up above and below sea level. To prevent comaion of the steel hull, twenty- four anode assemblies are employed, each of which earriea two anode mounting plates which also act as primary dielectric shields Reproduced by rour(r.y or Gulf C.N& Rr-me. Lld.

The anode assembly shown here consists of two anode mounting plates arranged aide by side and surrounded by an ice fender. The four active anode strips of platinised titanium are clearly visible. At this stage the platinum is covered by protective coatings hut when the rig is ballasted down for drilling operations, the unprotected anodes are some 9 metres below the normal water line. Each platinised titanium strip is supplied with DC power through a dedicated cable. If necessary the anodes can be unbolted and replaced by a diver, but are expected to have a life of twenty years


temperatures of - 3 to + I o O C , air temperatures of -50 to +20°C and scouring by sea ice. A proprietary thermosetting plastic incorporating a glass filler was to serve as a combined anode mounting and primary dielectric shield. Two platinised titanium strips were arranged on each anode mounting plate, the current density in the strip being about 200 Alm’ and the system capacity being in excess of 2000 A. Two anode mounting plates were used for each assembly and four assemblies were used on each of the four major faces of the rig, with another two on each of the four corner faces. This distribution provided a uniform level of protection on all parts of the submerged steel structure, including the central filled core. High purity zinc was used for the twenty-four reference electrodes and the necessary DC elec- tricity was provided by twelve power supplies.

Summary and Conclusions Following many years of proven success in

preventing the corrosion of ships’ hulls, an impressed current system employing platinised

titanium anodes has now been used to protect cathodically a steel caisson rig working in the Arctic Ocean, north of Canada. The experience gained during the installation and running of this system can be expected to result in further use of similar systems as the search for oil and gas deposits extends into even more hostile environments.

Acknowledgement The account given here is based largely upon infor-

mation provided by Wilson Walton International

References I Anon., Platinum Metals Rev., 1957, I , (I) , 26 2 Anon., Platinum Metals Rev., 1957, I , (3), 82 3 L. L. Shreir, Platinum Metals Rev., 1977, 21, (4),

110; 1978, 22, (I), 14 4 J. 8. Jensen, “Ships and Semi-Submersibles”, in

“Cathodic Protection: Theory and Practice”, ed. V. Ashworth and C. J. L. Booker, Ellis Honvood Ltd., Chichester, 1986, pp. 128-142

5 A. D. Willis and D. G. Lingnau, Paper 28, NACE Meeting, Corrosion/88, St. Louis, 21 -25 March, 1988 M. A. Warne and P. C. S. Hayfield, Mater. Per-

(UK) Ltd. I.E.C.

6 form., 1976, 15, (3), 39

Homogeneous Catalyst Research Kit Homogeneous catalysts play an impor-

tant part in many industrial processes, and contribute to the production of over 21 million tonnes of organic products. Their industrial use is mainly related to large volume commodity chemicals where the activity and selectivity achieved with rhodium catalysts is notable in, for example, hydroformylation and carbonylation reactions. Homogeneous platinum group metal catalysts are now finding increasing application in industrial research and development laboratories for the synthesis of fine chemicals and pharmaceuticals.

In order to assist organic chemists to select catalysts which are amenable to process scale-up, Johnson Matthey are now offering a Homogeneous Catalyst Kit which comprises ten platinum group metal complexes and five phosphines. The use of

these enables a variety of catalytic transformations to be carried out on a laboratory scale, including: allylic alkylation, aryl-alkene coupling, carbonylation, heterocycle formation, hydrogenation and isomerisation.

The kit includes traditional catalysts, such as Wilkinson’s Catalyst, which have been widely utilised in research laboratories, together with newer catalysts which enable more selective hydrogenations to be carried out and which also permit carbon- carbon coupling reactions. The catalysts are reasonably robust and are stable under normal laboratory conditions.

The Johnson Matthey Homogeneous Catalyst Kit is now available and further information about it can be obtained by writing to the Johnson Matthey office at Orchard Road, Royston, England, or to the European Associate Houses.


Car Exhaust Pollution Control LEAN BURN ENGINES AND THE CONTINUING REQUIREMENT FOR PLATINUM-CONTAINING AUTOCATALY STS

By R. A. Searles Johnson Matthey, Catalytic Systems Division, Royston

Over the past twenty years catalysts containing platinum group metals have become the preferred means of limiting the polluting emissions of carbon monoxide, hydrocarbons and nitrogen oxides from motor vehicles. However, from time to time methods of exhaust control are proposed which appear to off.. a viable alternative to autocatalysts. Europe has been slow to adopt emission control standards for vehicles which is, perhaps, surprising bearing in mind that European catalyst manu- facturers have been producing autocatalysts and European car producers have been fitting them to vehicles destined for the U.S. and Japanese markets for over fourteen years. This article gives the background to the suggested alternatives, which are in the main different approaches to lean burn operation, and to other engine based controls. It explains why, for the foreseeable future, a platinum-containing autocatalyst will still be required to ensure that the cleanest possible exhaust is emitted under all driving conditions.

Following a lead set by the state of California in the 1960s~ automobile emission controls have been progressively tightened throughout the Western World, as the damage caused by pollutants from the exhausts of engines has become more widely understood. At present the most stringent limits are in the U.S.A. and Japan where they have been applied for over 14 years, and in Australia where they have been mandatory for some two years. During this period autocatalysts based upon the platinum group metals have been the established technology employed by the world’s motor industry, and this development has been recorded here from time to time (I) . To date some zoo million cars have been equipped with such catalysts. The benefits derived from their use in the U.S.A. have been summarised here recently (2).

Following their successful implementation in these countries, similar stringent emission control standards have recently been, or are about to be, implemented in Switzerland, Austria,

Sweden, Norway and Finland. In the European Community pollution control standards are governed by a Community directive published in February 1988, which is based upon the assumption that autocatalysts, perhaps in conjunction with lean burn engines, will be used to achieve the proposed standards. However, a number of non-catalyst solutions have been suggested for European use, and some of these are considered here.

All exhaust emission standards set in the world are based on the principle that they are acceptable if the weight of each pollutant emitted does not exceed a stipulated level as the engine is taken through a standard test cycle. The car is “driven” on a laboratory rolling road against an equivalent load to that which it would experience on the open road. The driver follows a strict speed-time protocol using a chart against which he can match the speed of the car. Since road conditions and traffic regulations vary from country to country so do the driving cycles against which the regulations

Platinum Metals Rev., 1988, 32, (3), 123-129 12t

A LEAN BURN

ENGINE MISFIRE REGION

AIR . FUEL RATIO, by weight

Fig. 1 The four curves shown here only indicate trends, but they apply to any petrol engine. It is apparent that the air:fuel ratio is a most important factor influencing exhaust emissions. When fuel is in excess, at low or rich air:fuel ratios, engine power is high but combustion is poor and high levels of hydrocarbons and carbon monoxide are emitted. Peak combustion temperatures occur just on the lean side of the stoichiometric composition, and result in the highest emissions of nitrogen oxides. In the lean burn region engine power is moderate, carbon monoxide emissions are at a minimum, nitrogen oxides are reduced, but the hydrocarbons are significant

are based. In the European Community the existing test procedure equates to a theoretical drive through a congested city centre, such as Paris, the maximum speed being only 50 k.p.h. (31 m.p.h.) and the average speed 19 k.p.h. (12 m.p.h.). However, a more realistic test procedure incorporating a high-speed element up to 120 k.p.h. (75 m.p.h.) is being considered.

An internal combustion engine produces motive power as the hydrocarbon fuel is com- busted, but also varying amounts of unwanted carbon monoxide, hydrocarbons and nitrogen oxides emissions. In the case of a spark ignition engine, the fuel comprises a range of hydrocarbons formulated to give the best compromise for performance. For lead-free fuel the octane rating may be increased by the addition of alcohols or aromatic hydrocarbons. Sulphur, left behind during the refining process, will also be present. As the fuel : air mixture is reacted carbon dioxide and water are produced. Addi-

tionally, during combustion, some of the hydrocarbon fuel is only partially burned, resulting in the production of carbon monoxide, while a small amount of this is caught in crevices in the engine and so does not get com- busted at all. Some of these emitted unburned hydrocarbons are known carcinogens. At the reaction temperature, nitrogen and oxygen from the air combine to form nitrogen oxides. Thus as well as natural constituents of the atmosphere, several harmful emissions are formed. Emitted hydrocarbons and nitrogen oxides can react in the atmosphere to produce photochemical smog and ozone. Both of these contribute to the pollution of our atmosphere and to the damage of vegetation and health.

Combustion Emissions The emissions from an engine can be in-

fluenced by several factors, but mainly by the air : fuel ratio, Figure I . Here the mechanical


and chemical boundaries of engine operation are defined, and the options available for modi- fying these parameters are limited (3).

At low air : fuel ratios, when fuel is in excess, combustion is poor and emissions of hydrocarbons and carbon monoxide are high. As the fuelling strategy moves towards stoichiometry, the point at which there is exactly the right amount of oxygen from the air to burn the fuel, and which corresponds to an air : fuel ratio of 14.7 : I , hydrocarbon and carbon monoxide emissions fall but nitrogen oxide emissions rise. Peak engine power occurs just rich of stoichiometry; however, for a conventional engine, peak economy is achieved lean of stoichiometry. Peak combustion temperatures occur just lean of stoichiometry and give rise to the highest emissions of nitrogen oxides. In practice most conventional engines tend to be tuned to operate in the stoichiometric region in order to achieve the best compromise between economy and power.

As the fuelling moves further into the lean burn region, nitrogen oxide emissions fall sharply and carbon monoxide emissions are at a minimum. However, hydrocarbon emissions increase and engine power falls. Ultimately the lean misfire and flame out regions are reached, where hydrocarbon emissions are very high, and the power drops sharply.

In terms of improving engine emissions, therefore, it is possible to tune lean of stoichiometry (IS : I to 21 : I) to obtain low nitrogen oxides and carbon monoxide emissions, moderate engine power and good fuel economy. However, all of these apparent gains are achieved at the expense of increased hydrocarbon emissions to levels that can exceed the emission standard. Thus, from what has been said already it must be apparent that to achieve an acceptable balance of all the features required from an engine, namely, maximum fuel economy, immediate engine response to the driver and minimum production of noxious emissions both engine and catalytic technology must be used; the autocatalyst being used to control the excess hydrocarbon emissions.

Developments in engineering technology have considered both modification of the internal combustion engine and the addition of “bolt-on” devices external to the engine. These include idle mixture adjustment and ignition timing optimisation, such as exhaust gas re- circulation (EGR). Within the engine, piston design, sophisticated means for monitoring and mixing the air : fuel charge, and advanced fuel injection systems have all something to offer.

Lean Burn Engines Lean burn engines have several advantages;

such engines are strictly defined as those which run at air : fuel ratios between 18 : I to 21 : I ,

but this range may be extended somewhat. Operating at leaner air : fuel ratios offers the

advantage of improved fuel economy, which is the chief reason for developing such systems. In addition, as shown in Figure I , lower nitrogen oxide emissions from the engine are obtained. In contrast, higher hydrocarbon emissions occur if the engine is operated in too lean a range when there is not enough fuel for the mixture to bum properly and the engine begins to misfire and run roughly.

Methods of Achieving Lean Burn To burn a very lean mixture properly, the

fuel and air have to be mixed very thoroughly and burned very evenly. As there is so little fuel compared with a conventional engine, there is a greater chance of the flame missing some of the fuel droplets. This causes either a partial burn (misfire) or a “flame out” when no burning occurs and the engine loses power.

To achieve this good mixing and burning, it is necessary to employ sophisticated methods to control the fuel and air metering into the engine, the ignition timing and the spark to ignite the fuel. If any of these are not controlled precisely, the fuel economy and engine performance will suffer and the emissions from the engine will increase.

Air and Fuel Mixing Most methods attempt to improve mixing of

the air and fuel by using devices to make the

Platinum Metals Rev., 1988, 32, (3 ) 125

mixture “swirl” as it enters the combustion chamber. By doing this the mixture is made more homogeneous, and when ignited the swirling motion helps the flame to move across the whole width of the chamber quickly so that more even burning results. This swirl can be caused by changing the shape of the inlet port so that the mixture is forced to take a more tor- tuous path into the cylinder than normal.

Air and Fuel Metering To help in controlling the lean conditions

closely, the air and fuel have to be metered into the engine very precisely. This is done by an electronic control unit or microcomputer which measures the volume of air passing a fured point and calculates the amount of fuel needed. Fuel is then metered via injectors (one for each cylinder) into the engine. The microcomputer ensures that each cylinder is fed in turn so that maximum accuracy is obtained.

Ignition Current lean burn engines use standard spark

plugs, sometimes two per cylinder, to ignite the air : fuel mixture. However, a number of new developments are being investigated. For example, these include installing twelve small spark plugs or igniters per cylinder which, it is claimed, allow the engine to run even leaner. Another development is plasma ignition, where a stream of highly charged, high energy particles is injected into the flame to help it burn faster and therefore more efficiently. At present it is too early to say how successful such devices are, but the engines using them are expected to be limited, as are other lean burn engines, by the constraints of chemistry and thermodynamics, and they will produce increased nitrogen oxides as power increases.

Lean Sensors To improve the control of a lean burn system,

a lean sensor can be used which feeds a signal to the microcomputer which in turn controls the amount of fuel metered into the engine. This enables the engine to keep as clean as possible while avoiding lean misfire and allow-

ing rich operation to take place when power is needed.

Thus, the way in which emissions are produced in an engine is the key to realising that total elimination of all pollutants at source is not technically possible at present.

It must be emphasised that, while an engine can cruise under lean burn conditions, when maximum power is needed for acceleration or high speed or high load conditions an increase in power is needed. This results in a reversion to near stoichiometric fuelling with a concomi- tant increase in nitrogen oxide emissions. A lean burn engine will therefore perform less im- pressively, in pollution terms, on a test cycle which includes acceleration to high speeds than it will on a low-speed cycle. There will always be a hydrocarbonlnitrogen oxides/power trade- off unless another method of emission control is used to complement the lean burn engine. The new high-speed (up to 120 k.p.h.) addition to the European City Test Cycle provides just such a challenge to lean burn engineers.

Catalysts and Lean Burn Engines The accurate control of the air : fuel ratio for

lean burn engines requires a sophisticated and expensive control strategy. If any of this sophistication is relaxed control will be lost and the air : fuel ratio will drift, and emissions and fuel consumption will both increase. Examples would be the use of single rather than multi- point injection or the use of carburettors.

Even with the sophistication of devices to promote in-cylinder turbulence, better ignition and a lean sensor, hydrocarbon emissions from the engine are still a problem. It is therefore necessary to use an oxidation catalyst, such as platinum-palladium, both with simple and sophisticated lean burn engines to control hydrocarbons to proposed European standards on medium cars and in all probability for the Stage 2 directive proposed for small cars, see Table I. The oxidation catalysts convert hydrocarbons and carbon monoxide to carbon dioxide and water. Thus, when lean burn engines are used in combination with autocatalysts the advantage of better fuel economy can then be


Dates of Introduction

Hydrocarbons 1 Carbon I + nitrogen Nitrogen

Emissions, grams per test

Engine capacity

Cars over 2 litres

New models All new cars monoxide oxides oxides

October 1988 October 1989 25 6.5 3.5

combined with low polluting exhaust emissions. Because of the power limitations of lean burn

engines, they are unlikely to be used as power units for cars of engine capacity greater than z litres, but in this case experience accumulated, particularly in the U.S.A. over the last decade, demonstrates that the three-way catalyst of platinum, palladium and rhodium provides a very satisfactory solution to the control of the three noxious exhaust emissions.

The difference between the oxidation and three-way catalysts is simply in the combination of active components with which the honeycomb substrate is coated. While platinum, palladium and rhodium are required for three-

Cars 1.4-2 litres

Cars less than 1.4 litres

Stage 1

Stage 2

way catalysts, only platinum and palladium are required for oxidation catalysts, and the difference in cost is solely due to the material cost differences.

In the U.S.A. and other countries that have accepted the U. S. standards three-way catalytic emission control in combination with stoichiometric engines is likely to remain the system of choice for the foreseeable future.

Elsewhere in Europe vehicles in the >z litre and 1.4 to z litre range, whether powered by conventional or lean burn engines, will require catalysts to meet emission standards, Table 11. Stage I legislation in the <1.4 litre category does not yet demand the application of tight

- October 1991 October 1993 30 8

October 1990 October 1991 45 15 6

October 1992 October 1993 30 8 -

(proposed levels)

Table II

Possible Ways of Achieving Emission Control Standards

Engine capacity

>2 litres

1.4 to 2 litres

Engine and emission control

conventional engine + three-way catalyst (as in U.S.A.)

some vehicles as above or lean burn + oxidation catalyst or lean burn + EGR + oxidation catalyst or lean burn + EGR + three-wav catalvst

<1.4 litres Stage 1

Stage 2


lean tuned conventional engines lean burn

as Stage 1 + oxidation catalysts as Stage 1 + three-way catalysts

Table I

European Community Emission Standards

emission control. It can be argued, however, that this class of vehicle should not escape stricter controls since it represents 50 per cent of the car pool. When legislation is tightened to the Stage 2 limits for small cars, it is likely that oxidation catalysts will be used in conjunction with lean tuned or lean burn engines.

In the 1.4 to 2 litre class, exhaust gas re- circulation (EGR) is mentioned in combination with the lean burn engine and an oxidation catalyst. EGR is used to control the nitrogen oxide emissions from the engine while the catalyst controls hydrocarbons and carbon monoxide. It is shown above that, during acceleration, the fuelling of lean burn engines moves towards stoichiometry, thus it can be possible to take advantage of this situation by using a “clever” oxidation catalyst which can convert some of the nitrogen oxides under these conditions.

Lean burn systems offer the possibility of good fuel economy under part load (city driving) conditions, with acceptably low levels of nitrogen oxides emissions but with high hydrocarbon levels necessitating an oxidation catalyst for their destruction. However, under real driving conditions, transient response and

Fig. 2 Johnson Matthey has been a major manufacturer of autocatalysts since 1974, with manufacturing facilities in the U.K., U.S.A. and Australia. Autocatalysts are subject to the most rigorous engine testing, and catalyst performance is monitored day and night on computer controlled facilities

drivability are poor if the system is running too lean. Overall real fuel economy gains have been estimated to be approximately 5 per cent, compared to the 20 per cent sometimes quoted. Also, under real driving conditions nitrogen oxide emissions will increase, as has been shown by results obtained during a proposed high-speed cycle test.

Although some cars can be tuned to meet the proposed limits on the European City Test Cycle without a catalyst this is done at some cost to drivability and fuel economy. It is not expected that this technique will succeed when the new high-speed cycle is introduced into the European test procedure.

Conclusions The impossibility of keeping the emissions

from the internal combustion engine clean under all operating conditions of speed and power means that platinum group metal catalysts have an important role to play in cleaning up emissions after they leave the engine. No matter what type of fossil fuelled engine is developed, its emissions will be cleaner if a catalyst is employed in conjunction with devices to improve combustion or limit

Platinum Metals Rev . , 1988, 32, ( 3 ) 128

nitrogen oxide formation. From an environmental point of view it is now clear that the performance of an engine must be evaluated for all the emissions it produces under all operating conditions. Acknowledgements

I acknowledge and thank my colleagues Mr. A. J. J. Wilkins of Johnson Matthey Catalytic Systems Division and Dr. B. Harrison of Johnson Matthey Technology Centre for their assistance in preparing this paper.

Monitoring Impurities in

References I For example: G. J. K. Acres and B. J. Cooper,

Platinum Metals Rev., 1972, 16, (3, 74; G. J. K. Acres, B. S. Cooper and G. L. Matlack, ibid., 1973, 17, (3), 82; M. Shelef and H. S. Gandhi, ibid., 1974, IS, (I), 2; B. J . Cooper, E. Shutt and P. Oser, ibid., 1976,20, (2), 38; A. F. Diwell and B. Harrison, ibid., 1981, 25, (4), 142

2 M. P. Wdsh, Plarinum Metals Rev. , 1986,30, (3), 106

3 House of Lords Select Committee on the Euro- pean Communities, “Lead in Petrol and Vehicle Emissions”, February 1985

Water A TECHNIQUE BASED UPON THE HIGH ADSORPTIVITY OF PLATINUM

The widespread pollution of water, be it in the form of rain, groundwater, rivers, lakes, coastal waters or the oceans, is one of the most important environmental challenges facing the world today. A complete solution will only come about when major changes are made to the many contributing factors, which include: mineral extraction and processing, energy conversion and use, industrial manufacturing, intensive methods of farming and sewage dis- posal. In the meantime many immediate problems must be faced and none, perhaps, is more urgent than the need to analyse accurately and rapidly the impurities in reservoirs, to determine if the water is fit to drink.

A recent communication from researchers at the A. N. Frumkin Institute of Electro- chemistry, of the Academy of Sciences of the U.S.S.R., considers in some detail three electrochemical methods of determining impurities in water, and compares them with established methods (V. E. Kazarinov, V. S. Bagotzky, Yu. B. Vassiliev and 0. A. Khazova, J. Appl. Electrochem., 1988, 18, (3), 347-356).

The most suitable of the methods tested is based upon the fact that platinum readily adsorbs organic and toxic metals. Thus the amount of such impurities can be calculated from the degree of poisoning they cause, as determined from the decrease in the hydrogen adsorption capability of a platinum micro- electrode. Measurements were made using a conventional three-electrode cell, the working electrode being 2 to 3 mm of 0 .5 mm diameter platinum wire and the auxiliary electrode a I cm square of platinum gauze. In acid solutions a mercuric sulphate reference electrode may be used. Quantitative determination of individual substances is only possible in limited instances, but organic impurities may be differentiated

according to their oxidisability into easy-, medium- and difficult-to-oxidise categories.

The proposed electrochemical method of impurity determination is highly suitable for automatic water monitoring systems, and a number of analysers have been devised.

Oxidation Resistant Iridium Alloys A requirement for aerospace components

which are capable of serving for sustained periods of time at high temperatures has con- tinued to focus attention on the need for suitable materials, and a recently reported study by K. N. Lee and W. L. Worrell of the University of Pennsylvania has identified iridium- containing alloys as promising high temperature oxidation resistant materials. (“The Oxidation of Iridium-Aluminum and Iridium- Hafnium Alloys at 155oOC and 164ooC”, Extended Abstracts, Electrochemical Society, Spring Meeting 1988, Vol. 88-1, Abstr. No. 281, P. 423)

It has long been known that iridium loses weight at a significant rate when it is heated to temperatures in excess of about 11oooC. Now the oxidation behaviour of arc melted iridium alloys containing 5 to 80 atomic per cent aluminium or hafnium has been examined and it has been shown that the formation of gaseous iridium oxides can be restricted on appropriate alloys by the development of a protective oxide scale on the surface. However, if the amount of the second element is too low, any oxide scale which forms is porous and permits the passage of both oxygen and gaseous iridium oxides.

Iridium-aluminium alloys containing 60 to 80 atomic per cent aluminium form a continuous non-porous oxide layer which shows protective oxidation behaviour even when the alloy is exposed to oxygen at a temperature of :55ooC.

Platinum Metals Rev. , 1988, 32, (3) I29

Palladium-Rare Earth Alloys THEIR ORDER-DISORDER TRANSFORMATIONS AND BEHAVIOUR WITH HYDROGEN

By M. L. Doyle and I. R. Harris Department of Metallurgy and Materials. University of Birmingham

Despite considerable research activity, palladium-based alloys still represent the only known metallic systems which show appreciable permeability to hydrogen gas at moderate temperatures, without forming a discrete second phase. Solutions of rare-earth metals such as yttrium, cerium, and gadolinium in palladium permeate hydrogen readily and are of interest as possible alternatives to the palladium-silver alloys currently used as hydrogen diffusion membranes.

The unusual alloying behaviour of the rare- earth metals with palladium, that is their unexpected solid solubility, their structural changes and their very open lattice structures have made these systems of great physical and metallurgical interest.

These materials also offer the opportunity of studying the equilibrium and kinetic behaviour of hydrogen in very expanded metal environments and thus provide useful tests of thermodynamic and diffusion models.

The Metallurgy of Palladium-Rare Earth Alloys

The solid solubilities of rare-earth (R) metals in palladium were first investigated by Harris and Norman (I, 2) and Thompson (3) for the rare-earth metals lanthanum, cerium, praseodymium, yttrium, gadolinium and the actinide thorium. They found that, while lanthanum and praseodymium were virtually insoluble in palladium, cerium, yttrium, gadolinium and thorium were soluble up to about 12, 12, X I and 16 per cent solute content, respectively. (Later Speight found praseodymium soluble up to 2 per cent in palladium (4).) (All compositions given in this paper are in atomic per cent.) This solid solubility is despite the fact that the nominal size factor of these

atoms with respect to palladium is considerably in excess of the Hume-Rothery size limit of 15 per cent. In fact, cerium, yttrium and gadolinium are all approximately 30 per cent larger than the palladium atom and, on solution, expand the palladium lattice to a far greater extent than do noble metal substitutional additions.

The variation of room temperature lattice spacings of some palladium-rare earth solid solution alloys with increasing solute content are compared to the increase produced by corresponding silver and thorium additions in Figure I. It was noted that the expansion of the palladium lattice occurred to a larger extent for additions of thorium than for yttrium and gadolinium, despite the closely similar atomic diameters of these metals, which are 3.596 (thorium), 3.602 (yttrium) and 3.589

“02 1 / Th

0 2 4 6 8 1 0

SOLUTE, atomic per cent

Fig. 1 The increases in the room temperature lattice spacing of palladium- rare earth solid solution alloys with increasing solute concentration are compared here to the corresponding increase produced by silver and actinide thorium


(gadolinium) (2). In the same way, despite having a substantially smaller atomic diameter 3.422 8, cerium produced a larger lattice expansion than did yttrium or gadolinium. This value of 3.422 8, refers to cerium with an effective valency of close to four, as suggested by Harris and Norman for cerium in palladium-cerium solid solutions (I). These effects were attributed by Harris and Norman to an additional expansion due to the more rapid filling of va- cant Pd 4d states by the tetravalent thorium and cerium atoms as compared to the trivalent yttrium and gadolinium atoms ( 5 ) .

Hardness measurements of palladium- cerium, palladium-yttrium, palladium- gadolinium and palladium-europium solid solutions up to their solubility limits showed that the hardness did not vary with increasing rare- earth concentration in a simple way (6, 7). In- flections appeared in the hardness versus composition variations at cerium contents around 6 per cent and at yttrium, gadolinium and europium contents around 8 per cent. It was shown subsequently that these plateau regions in the hardness measurements were sensitive to the thermal history of the alloys, and a quenching procedure increased substantially the hardness values of the alloys in these regions, as seen in Figure 2 for the palladium-cerium alloys (8). In the quenched condition the hardness data exhibited the normal C” dependence, where C is the solute concentration. These observations were attributed to a degree of short range order (S.R.O.) in these alloys which was removed by the quenching process. The large atomic mismatch in palladium-rare earth binary alloys makes them good candidates for S.R.O., with the strain energy associated with two widely different sized atoms being relieved by forming an ordered or a partly ordered structure. The presence of order in these alloys was also suggested by the further observations that all these palladium-rare earth solid solutions are succeeded by a stable, congruent, Pd, R ordered phase with the LI (Cu, Au type) structure (9, 10).

Electrical resistivity measurements on a quenched palladium-6.5 per cent cerium alloy

- 200

i n‘ Al z

< I

g 100

Quenched

2 4 6 0 1 0 1 2 CERIUM, atomic per cent

Fig. 2 In palladium-cerium alloys hardness does not vary simply with the solute content in the alloys. Plateau regions occur within which the hardness is sensitive to the thermal history of the alloy, and quenching substantially increases the hardness in these regions

showed a large decrease at an annealing temperature of about 3moC (I I) consistent with there being appreciable S.R.O. present in the alloy. Electron microscope observations of planar slip in a lightly deformed palladium-9.4 per cent cerium alloy also suggested S.R.O. in this material (11).

The thermal expansion and magnetic susceptibility behaviours of some palladium-cerium and palladium-yttrium alloys have been examined (12). It was found that palladium- cerium alloys, with cerium contents greater than 3 per cent, and all of the palladium- yttrium alloys, showed anomalous thermal expansion behaviour in the temperature range 20

to 700OC. The plots of thermal expansion as a function of temperature showed two distinct linear regions with a much greater expansion rate in the higher temperature range. The temperature at which these changes in expansion behaviour occurred were 31of10OC for the palladium-cerium and 360e 1o0C for the palladium-yttrium alloys. Magnetic susceptibility measurements on a quenched palladium-6.5 per cent cerium alloy subjected to a series of isochronal anneals showed a dip in


o Palladium atoms Cerium atoms

C*Pd, Pd

~ y p e s of (111) plane

Fig. 3 The proposed structure of the Pd,Ce (Pd,Y) phase, showing the two different atomic arrangements that occur on (111) type planes

susceptibility at an annealing temperature of 30o0C, analogous to the dip in resistivity previously observed for the same alloy (I I).

Room temperature magnetic susceptibility measurements were performed on palladium- 5.75 per cent cerium alloys subjected to three different treatments: (i) vacuum annealed at 450°C and slow cooled, (ii) vacuum annealed and quenched from 450°C and (iii) slow cooled in hydrogen from 450°C. This study revealed that slow cooling of the alloy in hydrogen and subsequent removal of the hydrogen at low temperatures produced a susceptibility higher than could be achieved by slow cooling in a

vacuum, and close to the “quenched” value. This result suggested that the hydrogen absorbed into the palladium-cerium alloy inhibited the proposed ordering process on cooling from

The evidence obtained in this laboratory for ordering in these palladium-rare earth systems was all rather indirect until electron micro- scopical examinations were made on the palladium-cerium system close to the solubility limit at palladium-12.5 per cent cerium (13, 14). Bright superlattice spots, situated halfway between the fundamental reflections, in their diffraction patterns were observed, indicating

45O0C.

7

6

2 0 0 400 600 800 1 TEMPERATURE, *C

Fig. 4 Resistance ratios versuu temperature for two palladium alloys both containing 12.5 atomic per cent solute demonstrate their quite different behaviours: (a) for a slow cooled palladium-12.5 atomic per cent cerium alloy extrapolation of the disordered phase shows a room temperature resistance ratio of 5.5

1.4

1.3

1.2 0 K

K -

1.1

1.0

0.9 0 1 0 0 200 300 400 500 600 700

TEMPERATURE, *C

(b) a quenched palladium-12.5 atomic per cent yttrium alloy when extrapolated from the disordered phase gives a resistance ratio of 1.06

Plarinum Metals Rev., 1988, 32, (3) 132

Fig. 5(a) The (001) type electron diffraction Fig. 5(b) The ordered domains and antiphase pattern for a palladium-12.5 atomic per cent yt- domain boundaries in a palladium-12.5 atomic trium alloy aged for one week at 475OC shows per cent yttrium alloy aged for four weeks at the superlattice reflections corresponding to a 475 O C

highly ordered structure magnification x 68,000 approx.

the presence of a long-range ordered Pd,Ce structure. It was proposed that the Pd,Ce structure, shown in Figure 3, is a derivative of the Cu,Au-type, Pd,Ce phase (14). The order- disorder transformation was followed by measuring the resistance changes with temperature of palladium-12.5 per cent cerium up to 800OC and it was found that, at a temperature of 735*5OC, the alloy disordered producing a substantial rise in electrical resistance, as shown in Figure 4(a). When examined in the electron microscope, material “quenched” from above this order-disorder temperature showed diffraction patterns with split spots in the superlattice positions. This pointed to the fact that, even after fast cooling, the alloy exhibited extensive short range order.

Similar observations of the palladium- yttrium alloy system close to the solubility limit at palladium-12.5 per cent yttrium also revealed reflections corresponding to the formation of a Pd,Y superlattice structure (IS), which is isomorphous with Pd,Ce, though in this case the extra spots were quite faint (I 5 , I 6). Elec- trical resistance measurements showed that the alloy disorders at a temperature of around 5m°C ( I S , 16), as seen in Figure 4(b). The resistance plots (R/Ro) of Figures 4(a) and (b)

for palladium-12.5 per cent cerium and palladium- I 2.5 per cent yttrium alloys, respectively, show their strikingly different behaviours. The extrapolated resistance of the disordered palladium-I 2.5 per cent cerium alloy shows that, at room temperature, R disordered/R ordered is approximately equal to 5.5, while the experimental “quenched” value for disordered palladium-12.5 per cent yttrium shows that R disordered/R ordered = I .06. The very large increase in the resistivity of palladium- 12.5 per cent cerium on disordering cannot be attributed simply to the large strain energy associated with the cerium atoms because, as mentioned previously, the yttrium atoms are significantly larger than the cerium atoms, whereas the resistivity increase on disordering palladium-12.5 per cent yttrium is very small. One explanation might be a change in the effective valency of the cerium atoms on disordering, that is a change in the degree of 4f hybridisation.

The faint superlattice reflections observed on slow cooling Pd , Y, as compared to Pd , Ce, indicates less order in the former alloy. Work in this laboratory has shown that if the Pd,Y material is aged at a temperature just below the order-disorder temperature, the superlattice

Plarinum Metals Rev., 1988, 32, (3) 133

p -min

4 : O l - 3 9 9

d w I-

f P 2 3 g 7 1 3 - 9 5

w I! : 3.93

1

0.0 0.1 0.2 (

t / a

Fig. 6 Plotting the lattice parameters versus electron:atom ratio for three isoelectronic alloys shows that one of the major factors controlling hydrogen solubility is closure of the hydrogen miscibility gap at e:a= 2.4

Pd-Y-H rn Pd-Ce-H o Pd-Ag-H

reflections become more intense (I 6). This corresponds to a growth in the size of ordered domains, rendered visible by imaging with the superlattice spots. Figures 5(a) and (b) show the (001) diffraction pattern of a palladium-12.5 per cent yttrium alloy aged at 475OC for one week, and the antiphase domain structure of a similar sample aged at 475OC for four weeks. Longer ageing times were necessary to raise the diffracted intensities to the point where the ordered domains of Figure 5(b) could be suc- cessfully imaged. The light areas are the ordered domains and the dark contrast are the antiphase domain boundaries, which are areas of high strain involving Y-Y and Pd-Pd nearest neighbours.

Hydrogen Absorption Behaviour The first equilibrium studies of the absorp-

tion of hydrogen by palladium-rare earth alloys were carried out to ascertain the rare-earth concentrations necessary to suppress the formation of a discrete R-phase hydride from the a-phase in these alloys (6, 17). This work was later confirmed by Sakamoto and colleagues ( I 8). These studies were a necessary precursor to research on the use of these alloys as hydrogen diffusion membranes, where the precipitation of a second phase hydride must be avoided at all costs. It

was found that, under operating conditions, a continuous metal-hydrogen phase could be guaranteed for palladium dloys containing 8 per cent yttrium, gadolinium or europium, 6 per cent cerium or 24 per cent silver. These alloys are isoelectronic with an electron to atom (e/a) ratio of 0.24, and the closure of the hydrogen miscibility gap at this value, see Figure 6, indicates one of the major factors controlling hydrogen solubility in these alloys. In- deed, it is widely acknowledged that changes in the hole populations of the Pd qd-band, by both substitutional alloying elements and interstitial hydrogen, are a major factor in determining the hydrogen absorbing ability of these alloys. The saturated hydrogen contents of several palladium-cerium alloys have been plotted as a function of cerium content, and demonstrate a correlation between e/a and the extent of hydrogen solution, such that increasing cerium concentrations caused a decrease in the terminal hydrogen solubility (19). Thus Pd,Ce has only a small hydrogen absorption capacity (20). Data by McFall, Witherspoon and Lewis (21) indicating the change in hydrogen solubility in palladium with progressive cerium additions are shown in Figure 7.

The hydrogen solubility in ordered and disordered forms of palladium-12.5 per cent


cerium has been explained in the pressure range 1.7 to 7.7 bar and temperature range 160 to 250OC (20). The results are plotted in Figure 8(a) and show that, at a given temperature and pressure, the disordered material absorbs significantly more hydrogen than does the ordered material, though in both cases the hydrogen solubility is small. Although the thermodynamic data were limited the results indicate very similar values of the relative partial molar enthalpy at infinite dilution ARE for both the quenched and the ordered forms of the material. The investigators also claimed that there was evidence to suggest a minimum in the variation of An: with cerium concentration at around 8-9 per cent cerium. Both of these indi- cations were later confmed by others who examined the hydrogen solubility across the whole solid solution range of palladium-cerium (22). They found that A% values for the disordered and ordered palladium-12.5 per cent

a b c d e

1 . 5 -

rn I E E 1 . 0 -

w’ a 3 UI u) W d a rn 0 . 5 - 0 -

0.1 0.2 0.3 0.4

H /(Pd. C C )

Fig. 7 Change in hydrogen solubility with progressive cerium additions aRer McFaU, Witherspoon and Lewis (21)

a =Pd-10.1 atomic per cent Ce b=Pd-8.0 atomic per cent Ce c =Pd-7.5 atomic per cent Ce d = Pd-5.9 atomic per cent Ce e =Pd-5.3 atomic per cent Ce

001 002 003 004 HIM

0.1 0.2 0.3 HIM

Fig. 8 Hydrogen solubility of two palladium alloys in the quenched and slow cooled states (a) palladium-12.5 atomic per cent cerium (b) palladium-12.5 atomic per cent yttrium

(a) . T=230°C (quenched) T=230°C (ordered)

0 T = 16OOC (quenched) T= 1 6 O O C (ordered)

(b) 0 T = 220 O C (ordered) T=220°C (quenched) T=160°C (ordered)

o T = 16OOC (quenched)

cerium alloy were very similar, at -17.4 and -16.8 kJ/mol, respectively. They also observed a minimum in An: values for a cerium content around 10 per cent. However, despite the good general agreement between the trends observed by the two groups, their actual thermodynamic values show discrepancies which, at this juncture, cannot be explained.

Sakamoto, Flanagan and Kuji analysed their data for the whole range of palladium-cerium alloys in terms of a model which assumed the preferential occupation by hydrogen of sites surrounded only by palladium atoms (22).


They obtained good agreement with the experimental data and therefore postulated cerium atoms as being anti-trapping sites for hydrogen. They also plotted values for the relative chemical potential of hydrogen against the degree of order, calculated from resistance measurements, for Pd,Ce and found that the changes in the chemical potential were directly related to the state of order of the material.

Similar isothermal solubility studies were performed on ordered and disordered forms of W , Y in the pressure range o to 4 bar (16); these results are shown in Figure 8(b). As with Pd , Ce, the disordered palladium- I 2.5 per cent yttrium material absorbs more hydrogen than does the ordered material. However, in both the ordered and disordered forms, this alloy absorbs much more hydrogen than palladium-12.5 per cent cerium due to the trivalent nature of the yttrium atom (and thus more holes in the 4d band).

Values of the relative partial enthalpies and entropies of solution (AnH,AsH) of hydrogen in palladium-12.5 per cent yttrium were calculated for the ordered and disordered material, for the H/M range 0.19 to 0.26 (16). As with palladium-12.5 per cent cerium, the values of A R H and AS, are more negative for the quenched alloys, the A% values being con- sistently 5 kJ/mol more negative than for the ordered alloy. A comparison of the solubility of hydrogen in palladium-8 per cent yttrium and palladium-12.5 per cent yttrium shows that, at any temperature below 450°C, palladium-8 per cent yttrium has a higher terminal hydrogen solubility than palladium-12.5 per cent yttrium. However, at low enough pressures palladium-12.5 per cent yttrium will dissolve more hydrogen than palladium-8 per cent yttrium. The fact that, at low pressures and high temperatures, palladium-12.5 per cent yttrium can absorb more hydrogen than palladium-8 per cent yttrium is unexpected. In the low pressure region the hydrogen content of the material is low (<o. I HIM) and trapping of hydrogen by yttrium atoms may account for most of the hydrogen solubility. At higher hydrogen concentrations traps can no longer ac-

count for the greatest proportion of the hydrogen solubility and the palladium-12.5 per cent yttrium then shows a lower solubility for hydrogen than palladium-8 per cent yttrium. Modified Sieverts plots for palladium-12.5 per cent yttrium show that there is a strong hydrogen-metal interaction in this alloy at pressures below 0.25 bar.

In a paper on the thermodynamics of hydrogen in palladium-yttrium solid solution alloys Yoshihara and McLellan found very large decreases in the partial enthalpy of solution with increasing solute content which they attributed to the trapping of hydrogen by the yttrium atoms (23). They determined that the large contribution to the enthalpy term resulting from yttrium additions was due to the large lattice expansion it caused and not to any strong chemical affinity between yttrium and hydrogen. Hydrogen trapping by substitutional impurities in transition metals has been examined, based on a model of impurity atoms forming metal-hydrogen complexes (24). The perturbation of hydrogen atoms in transition metals, including palladium, was evaluated in terms of a volume and an electronic contribution, and good agreement with experimental data was found. This group of investigators predict that in solution with palladium, yttrium will have a trapping efect.

Kinetic Behaviour of the Hydrogen

It has been shown that the diffusion coefficients of the palladium-rare earth alloys: palladium-8 per cent yttrium, palladium-8 per cent gadolinium, palladium-5.75 per cent cerium and the palladium-noble metal alloy, palladium-25 per cent silver, were closely similar in the temperature range 100 to 50o0C, despite their different lattice spacings (25, 26).

Recent studies of the diffusivities of a range of palladium-yttrium and palladium-cerium alloys have been made using an electrochemical technique, in the temperature range 10 to 5ooC, and found that the activation energies of diffusion for both systems decreased as the rare-earth solute concentration increased (27).


The activation energies of palladium-cerium alloys were lower than those of the palladium- yttrium alloys and exhibited a shallow minimum at around 6 or 7 per cent cerium.

Ishikawa and McLellan also studied the diffusivities of hydrogen in a range of palladium- yttrium solution alloys in the same temperature range and using a similar technique (28).

Comparison of the two sets of data shows that, at yttrium concentrations below about 7 per cent, there is broad agreement as to the effect of increasing yttrium content on the diffusivities (D) of hydrogen at 298 K; Sakamoto detected a small increase in D while Ishikawa detected a small decrease, compared to pure palladium. However, at yttrium compositions of 8 and 10 per cent, the latter found a very large decrease in diffusivity which was attributed to large trapping contributions at the higher yttrium contents (28). The activation energies (Ea) and frequency factors (Do) determined by Ishikawa were considerably greater than the corresponding values found by Saka- moto, across the whole range of yttrium concentrations studied.

A proposed explanation for the discrepancies between these two groups of workers is based on the work of Hughes (29), Wileman (30) and their colleagues on the diffusivity of hydrogen in a palladium-8 per cent yttrium alloy. Figure 9 shows the data for a palladium-8 per cent yttrium alloy which has been annealed at 6m°C for two hours and slowly cooled to room temperature in a vacuum prior to any diffusion measurements taking place (30). Clearly the initial behaviour of the material on heating in hydrogen is quite different to the data collected on subsequent runs, after the material had been cooled in hydrogen. The activation energies and frequency factors for the material which had been cooled in hydrogen are far higher than those for the material cooled in a vacuum. The activation energies (Ea) are summarised in the Table.

The measurements given by Sakamoto were obtained for samples heated at 85oOC for 2

hours and then vacuum cooled at a rate of 5-6OC/min (27). This material should be in the

First heating run

1 2

1 /T(ld')

Fig. 9 Diffusion coefficients versus temperature for a vacuum annealed and slow cooled palladium-8 atomic per cent yttrium alloy show the different behaviours of the material on a first heating run in hydrogen and after subsequent runs (after Ref. 30)

low activation energy state determined by Wile- man (30)~ and the activation energy value of 19.2~1.0 kJ/mol of Sakamoto (27) is quite close to the value of 22.5+0.4 kJ/mol obtained by Wileman.

On the other hand, the sample preparation procedure of Ishikawa and McLellan involved annealing at 627OC for 4 hours in hydrogen gas followed by cooling at 30°C/min again in hydrogen gas (28). This, in our experience, should result in samples being in the second, high, activation energy state described by Wileman (30). The value of the activation energy for this state as determined by Wileman is 30.5 kJ/mol(30), compared to the value of 42 kJ/mol determined by Ishikawa (28); although there is some difference between these values, they are both well in excess of the values for the initial heating state, determined by Sakamoto (27) and Wileman (30).

Wileman (30) and Hughes (29) attributed their observations of anomalous diffusion behaviour to the ordering of the palladium-8 per cent yttrium alloy on cooling in a vacuum, which produced a smaller activation energy for hydrogen diffusion when the material was first heated in hydrogen. The general shape of the curve supports this suggestion as it resembles

Platinum Metals Rev., 1988, 32, ( 3 ) 137

1.2

1 - 0 a E ” 0 8 2- 2

-

2 0-6 w I

0 . 4

0 . 2

Fig. 10 Hydrogen permeation date versus temperature for palladium-8 atomic per cent yttrium and palladium-25 atomic per cent silver alloys at a differential pressure of 6.8 bars indicates that the former is superior over a wide temperature range (after Ref. 30)

100 200 300 400

TEMPERATURE, ‘C

those of Goltsov and colleagues (31, 32) who studied hydrogen diffusion in ordered and disordered Cu, Au and palladium-silver alloys. The fact that the lower activation energy state only persists up to 35Ooc, that is close to the proposed (I 2) order-disorder temperature in this material, also supported an explanation based on order-disorder.

Earlier magnetic susceptibility measurements indicated that subsequent cooling of the material in hydrogen did not allow re-ordering to occur and hence produced a higher activation energy and lower diffusivity for hydrogen (12).

The fact that both Sakamoto (27) and Ishikawa (28) performed their measurements in the temperature range o to 5o°C, well below the critical temperature of 350°C, means that both groups would find their data reproducible and consistent even after a large number of temperature cycles. Indeed, work in this laboratory has shown the initial ordered state is stable up to about 300OC for numerous temperature cycles in hydrogen gas. Sakamoto interpreted his resistivity measurements in terms of the material showing no sign of order (27), but work in this laboratory has shown that hydrogen diffusion and solubility are much more sensitive to order than is the electrical resistivity.

Whether or not this material actually under- goes an order-disorder transformation as described is very difficult to prove un- equivocably, however, it is certain that these materials when cooled in vacuum or in hydro-

gen produce very different diffusion behaviours at up to 35oOC. While the data of Wileman (30) do not extrapolate exactly to the data of Saka- mot0 (27) or of Ishikawa (28) (this may be due to the very small hydrogen concentrations used by Sakamoto and Ishikawa compared to those of Wileman), the observed increases in activation energy and frequency factor of Ishikawa over those of Sakamoto are clearly predicted. This shows that great care is necessary when selecting a particular bulk pretreatment for this material prior to making observations.

Diffusion Membrane Technology The successful employment of an alloy as a

hydrogen diffusion membrane requires that: (i) the alloy permeates a considerable amount of hydrogen at moderate temperatures and pressures, (ii) the material is mechanically stable and does not degrade appreciably with use, and (iii) the membrane is resistant to poisons which may “block” the membrane surface during its operation.

At present these criteria are best satisfied by the commercially used palladium-25 per cent silver membranes.

Work by Wise suggested that the palladium- rare earth alloy membranes containing 6 per cent cerium and 8 per cent yttrium (both approximately isoelectronic with palladium-25 per cent silver) showed permeabilities in excess of those displayed by palladium-25 per cent silver under the same conditions of temperature


I Activation Energies of Palladium-Yttrium I

Pd-8% Y (30)

Pd-8% Y (27) Pd-8.1% Y 128)

I Material

22.5 2 0.4 kJ/mol

19.2 & 1 .O kJlmol

30.3 & 0.4 kJ/mol

42.0 kJ/mol

Initial run, after cooling in vacuum

Runs, after cooling in hydrogen

and differential pressure (6). Further work by Fort, Farr and Harris confirmed that both a palladium-6.6 per cent yttrium and a palladium-ro per cent yttrium membrane were capable of allowing more hydrogen to permeate than was possible with palladium-25 per cent silver (33). In addition they noted that, after heavy surface oxidation, palladium-yttrium samples were more permeable than similarly treated palladium-25 per cent silver. This was due to the incomplete nature of the surface oxide formed on palladium-yttrium alloys (which exposes an active palladium-rich sub- layer) compared to the impervious tenacious oxide associated with the palladium-25 per cent silver alloy. They also commented on the appreciable solid solution hardening in the palladium-rare earth alloys, due to the large atom size differences, and the consequent possibility of maximising the permeabilities of these materials by the use of thinner membranes and/or larger gas differential pressures.

Hughes and colleagues established further the improvements in permeation afforded by the use of palladium-rare earth diffusion membranes, and also studied the effects of S.R.O. on the permeation characteristics of these materials (25, 26, 29). They found considerably enhanced permeabilities for palladium-8 per cent yttrium and palladium-5.75 per cent cerium membranes on initial heating in hydrogen, as compared to values obtained on subsequent heating and cooling runs. This enhancement of permeability was attributed to the alloy being “ordered” in its initial condition with the presence of hydrogen suppressing the ordering on subsequent runs. Electron microscope observations on the effect of hydro-

gen in a palladium-12.5 per cent yttrium alloy, which is the only system that can be easily studied in this way, indicate that in this alloy at least, ordering occurs normally in the presence of hydrogen (16), although at this composition we would expect the order to be more stable than in the non-stoichiometric palladium-8 per cent yttrium alloy. Nonetheless, recent measurements have confirmed both the very large enhancements of permeation which are available on initial heating of a palladium-8 per cent yttrium diffusion membrane up to 35Ooc (compared to subsequent heating and cooling) and its superiority over a wide range of temperatures and differential pressures when compared with palladium-25 per cent silver (30), see Figure 10. Wileman and Harris (34) have demonstrated the quite different rates of permeation of the hydrogen isotopes, protium and deuterium through a palladium-8 per cent yttrium membrane over a wide range of temperatures and pressures. The possibility of using this material in a cascade system for the large scale separation of hydrogen isotopes has been discussed (35).

Difficulties in working these materials have so far prohibited their use as diffusion membrane materials. The reported hydrogen soften- ing of palladium-rare earths alloys may help overcome these problems (7). It is also worth noting that a number of researchers have acknowledged the superior mechanical stabilities, longer working lifetimes and resistance to carbon embrittlement of palladium-8 per cent yttrium compared to palladium-25 per cent silver membranes (30, 33, 36). Indeed the permeability behaviour of palladium-8 per cent yttrium has been compared with a wide range


of palladium-based membrane materials in a review published here previously (37).

Concluding Remarks Solid solutions formed by the dissolution of

rare-earth atoms in palladium are surprisingly extensive possibly due to a d-band filling contribution to the large lattice expansion observed in these alloys.

Palladium-rare earth solid solution alloys display order-disorder transformations.

Palladium-rare earth alloys are able to absorb hydrogen exothermically at moderate temperatures and pressures. The amount of hydrogen absorbed decreases with increasing rare-earth content.

The hydrogen solubilities in these materials are affected by the order-disorder transformations in such a way that the disordered alloys absorb more hydrogen than the ordered alloys under identical conditions of temperature and pressure.

The kinetic behaviour of hydrogen in these alloys is also influenced strongly by the state of order, and thus may only be described ade- quately by taking into account the differences between sample pretreatments.

Palladium-rare earth alloys are good candidates for use as hydrogen purification and isotope separation membranes and exhibit considerably improved permeability over conventional palladium-silver materials.

References

I I. R. Harris and M. Norman, 3. Less-Common

2 M. Norman and I. R. Harris, 3. Less-Common

3 J. R. Thompson,J. Less-Common Met., 1964,6,94 4 J. D. Speight, 3. Less-Common Met., 1973, 30,

I59 5 I. R. Harris and M. Norman, 3. Less-Common

Met., 1970, 22, 127 6 M. L. H. Wise, J. P. G. Farr, I. R. Harris and

J. R. Him, Congrks Int. L’Hydrogene dans les Metaux, Paris, 29 May-2 June, 1972, 72

7 J. R. Hirst, M. L. H. Wise, D. Fort, J. P. G. Farr and I. R. Harris, 3. Less-Common Met.,

8 D. T. Hughes, Ph.D. Thesis, University of Birm-

9 J. R. Thompson, 3. Less-Common Met., 1967, 13,

10 0. Loebich and E. Raub, 3. Less-Common Met.,

X I J. W. Brooks, M. H. Loretto and I. R. Harris, Met. Sci., 1976, 397

12 D. T. Hughes, J. Evans and I. R. Harris, 3. Less- Common Met., 1980, 76, 119

13 N. Kuwano, T. Shiwaku, Y. Tornokiyo and T. Eguchi, Jpn. J . Appl. Phys., 1981, 20, 1603

14 D. A. Smith, I. P. Jones and I. R. Harris, 3. Muter. Sci., Lett., 1982, I, 463

I 5 Y. Sakamoto, M. Yoshida and T. B. Flanagan, 3. Muter. Res., preprint

16 M. Doyle and I. R. Harris, to be published 17 M. L. H. Wise, J. P. G. Farr and I. R. Harris,

18 Y. Sakamoto, K. Yuwasa and K. Hirayama, 3 .

19 J . Evans, 1. R. Harris and P. F. Martin, 3. Less-

Met., 1968, 15, 285

Met., 1969, 18, 333

1976, 49, I93

ingham, 1978

307

1973, 309 47

3. Less-Common Met., 1975, 41, 1x5

Less-Common Met., 1982, 88, 115

Common Met., 1980, 75, 49

20

21

22

23

24

25

26

27

28

D. A. Smith, I. P. Jones and I. R. Harris, 3. Less- Common Met., 1984, 103, 33 W. D. McFal1,T. C. WitherspoonandF. A. Lewis, 3. Chem. Soc., Chem. Commun., 1973, (4), 102

Y. Sakarnoto, T. B. Flanagan and T. Kuji, Z. Phys. Chem., 1985, 143, 61 M. Yoshihara and R. B. McLellan, Acta. Metall.,

P. Vargas, H. Kronmuller and M. C. Bohm, Z. Phys. Chem., 1985, 143, 229 D. T. Hughes and I. R. Harris, 3. Less-Common Met., 1978, 61, 9-21 D. T . Hughes and I. R. Harris, Z. Phys. Chem., 1979, 1x7, S185 Y. Sakamoto, H. Kaneko, T. Tsukahara and S. Hirata, Scr. Metall., 1987, 21, 415 T. Ishikawa and R. B. McLellan, Acta Metall., 1987, 353, 781

1988, 36, (21, 385

~~- 29 D. T. Hughes, J. Evans and I. R. Harris, 3. Less-

Common Met., 1980, 74, 255 30 R. Wilernan and I. R. Harris, 3. Less-Common

Met., to be published 31 V. A. Goltsov and G. E. Kagan, Congrks Int.

L’Hydrogene dans les Metaux, Paris, 29 May- 2 June, 1972, 249

32 V. A. Goltsov, V. B. Vykhodets, P. V. Gel’d and T. A. Krylova, Fiz. Met. Metalloved, 1970, 30, (3), 657

33 D. Fort, J. P. G. Farr and I. R. Harris, 3. Less-

34 R. Wilernan and I. R. Harris, 3. Less-Common

35 J. Evans, I. R. Harris and D. K. Ross, 3. Less-

36 D. Fort and I. R. Harris, 3. Less-Common Met.,

37 G. J . Grashoff, C. E. Pdkington and C. W. Corti,

Common Met., 1975, 39, 293

Met., 1985, 109, 367

Common Met., 1983, 89, 407

19759 41, 313

Platinum Metals Rev. , 1983, 27, (4), 157

Platinurn Metals Rev. , 1988, 32, (3) 140

Viacheslav Vasil’evich Lebedinskii CENTENARY OF THE BIRTH OF A RHODIUM CHEMIST

By Professor George B. Kauffman Department of Chemistry, California State University, Fresno, U.S.A.

One of the lesser known members of the Chugaev school of inorganic chemists, Lebedinskii devoted more than four decades to the synthesis and analysis of co-ordination compounds of the platinum group metals, particularly those of rhodium, iridium, and platinum. He developed a new industrial method for purifying rhodium, and he carried out studies of the extraction and refining of the platinum metals and their separation from dilute solutions and salts.

Prerevolutionary Russia was the most important source of platinum, supplying about 95 per cent of the world’s needs, and, despite the later discovery of extensive deposits of this noble metal elsewhere, the U.S.S.R. remains the leading producer of the platinum group metals - 3.7 million troy ounces compared to the 3.2 million ounces produced in the Republic of South Africa during 1985 (I). In

1828 the Russian government authorised the coinage of large amounts of Siberian platinum (2), and by 1846, when platinum coins were withdrawn from circulation, a total of 14,600 kilograms (39,117 troy pounds) of platinum had been coined in 3-, 6-, and 12-rouble denominations (3). Furthermore, ruthenium, the last of the platinum metals to be discovered, was isolated in 1 8 4 by Karl Karlovich Klaus (I 796- I 864) from platinum residues obtained from Count Egor Frantsevich Kankrin (1775-1845) and named in honour of Russia (2bj 3, 4). Russia was also the home of the world-famous Platinum Institute of the U.S.S.R. and of the world’s first platinum metals journal, Zzvestiia Sektora Platiny i Dmgikh Blagorodnykh Metallov (Annals of the Sector for Platinum and Other Noble Metals, hereafter called Zzvesriia for the sake of

Viaeheslav Vasil’evich Lebedinekii 1888- 1956

Being one of the school of platinum metal chemists which formed around Chugaev, Lebedinskii was an acclaimed investigator and prolific writer on the platinum metals, with more than eighty papers on them to his credit. He also presented popular scientific lectures to soldiers, students and industrial workers. A Correspond- ing Member of the Academy of Sciences of the U.S.S.R. since 1946, by his work he contributed much to the knowledge of the platinum metals. He died on December 12th 1956 in Moscow


simplicity) (5). Thus it is not surprising that Russian chemists have been in the forefront of platinum metals research. Raleigh Gilchrist estimated that of the 800 articles on this subject published from 1915 to 1940, 28 per cent were contributed by Russians, with the Germans in second place, contributing 24 per cent (6).

Lev Aleksandrovich Chugaev (1873-1922) (7), founder and first director of the Platinum Institute and first editor of its Zzvesriia, was the foremost figure and leader of a group of Rus- sian chemists who systematically explored the chemistry and metallurgy of the platinum metals, and Gilchrist stated that “the character of practically the entire Russian output of researches on the chemistry of the platinum metals reflects the influence of Chugaev” (6). Chugaev created around himself a school of prominent platinum metal chemists, of whom Il’ya Il’ich Chernyaev (1893-1966), of trans effect fame, is the best known (8). Although another member of this group, Viacheslav Vasil’evich Lebedinskii, ranks second only to Chernyaev in the number of contributions published in the Zzvestiia - 49 compared to 65 by Chernyaev - his name and work are little known in the West. The centenary of his birth seems an appropriate time to bring his work to the attention of a wider scientific audience.

Lebedinskii’s Academic Life Viacheslav Vasil’evich Lebedinskii was born

on 1st September 1888 in St. Petersburg (now Leningrad) @).Upon his graduation from high school in 1907, he matriculated at the Petersburg University, graduating in 1913 with a First Degree Diploma. His thesis on the influence of optical superposition on anomalous rotatory dispersion was carried out under the direction of his teacher, Chugaev (10). He then remained at the university, working with Chugaev and preparing for a teaching career.

From 1916 Lebedinskii worked in the Platinum Section of the newly organised Com- mission for the Study of Russian Natural Pro- ductive Sources (KEPS). Beginning in 1918 he worked at the newly created Institute for the Study of Platinum and Other Noble Metals at

the Academy of Sciences of the U.S.S.R., in Leningrad, and he moved to Moscow in 1934 when the Platinum Institute merged with the Institute of Physicochemical Analysis and the General Chemistry Laboratory of the Academy of Sciences to become the Institute of General and Inorganic Chemistry, under the director- ship of Nikolai Semenovich Kurnakov (1860-1941) (11) . Lebedinskii became a member of the Scientific Council of the In- stitute and the Director of its Laboratory for the Synthesis of Complex Compounds.

From 1920 to 1935 Lebedinskii was Professor at Petrograd (later Leningrad) University, the Leningrad Chemico-Technological Institute, and the Second Leningrad Medical Institute. After he moved to Moscow in 1935 he was Pro- fessor at the M. V. Lomonosov Institute of Fine Chemical Technology and the Moscow In- stitute for Nonferrous Metals and Gold, both until 1952. He trained more than a score of Bachelors of Science candidates and several Doctors of Chemical Science.

Work on the Platinum Metals Lebedinskii was the first to prepare stable ca-

tionic complexes of rhenium ( I I ~ , 12b), and he investigated compounds of cadmium halides with pyridine (I 3a) and aniline (I 3b). He also wrote articles on Stalin Prize winners (14a) and the life and work of Chugaev (14b) and of Chernyaev (14c). Except for an article on a palladium complex [PdCl,(CH,CN),I (IS), the majority of his more than eighty papers on the platinum metals involved rhodium, iridium, and platinum, for the first two of which he achieved international recognition.

Rhodium Dmethylglyoxime Complexes. Lebedin-

skii’s mentor, Chugaev, is best known for his discovery in 1905 of the scarlet precipitate formed by the reaction of the nickel(I1) ion with dimethylglyoxime, the first organic spot test reagent used to detect a metal ion (7, 16). Although a single oxime group shows little tendency toward co-ordination, when it can form part of a chelate ring, as in a dioxime, the


nitrogen atom becomes a good electron donor and hence a good ligand.

Lebedinskii’s first postdoctoral research involved co-ordination compounds of rhodium(II1) with dimethylglyoxime and is a continuation of Chugaev’s classical work on dioyimines (dioxime complexes). Together with Chugaev, he showed that hexa- covalent rhodium(II1) formed two series of compounds with dimethylglyoxime (CH,C(NOH)C(NOH)CH,, DH,), these being [a] [Rh(DH),(NH,),lX(where X = C1, I, OH, NO,, CIO,, ClO,, 1/2[PtCl,], and 1/2[PtBr,l) and [bl R[RhCI,(DH),l (where R = H, NH,, or (NH,),CNH, (guanidinium) ( I 7). The chloride of series [a] was prepared from [RhCl(NH,),]CI, and DH,, and the parent acid of series [bl from Na,[RhCl,I and DH, . Each bidentate DH- group is bonded to the rhodium atom by a co-ordinate covalent bond (through the oxygen atom) and a covalent bond (through the NOH group).

Twenty-five years later Lebedinskii and Fedorov obtained the compound NH, trans-[Rh(DH),(NO,),l .aH,O by boiling Na,[RhCI,l solution with DH, and precipitating the resulting solution with NH,Cl (18). By metathesis they obtained the corresponding guanidinium and tetra- ammineplatinum(I1) salts. In 1948 they boiled solutions of NH,[RhCl,(DH),l with NH,I, NH,Br, NH,SCN, and thiourea (tu) and obtained NH,[RhClI(DH),I.1/2H2O, NH,[RhBrCl(DH),I .2H,O, and also NH, [RhClSCN(DH),], and the nonelectrolyte [RhCI(DH),(tu)l, respectively (19a). Boiling the ClI complex with thiourea results in substitution of the Cl atom but not the I atom, while similar treatment of the ClSCN complex causes substitution of the SCN group by thiourea. They also obtained (19b) the non- electrolytes [Rh(DH),NO,NH,I* 1/3H20, [RhCl(DH),NH,l -H,O, and [Rh(DH),Clpyl (where py = C,H,N) by boiling DH, with K[Rh(NOZ), (NH,) , 1 or [Rh(NO, 1 , (NH ,) , I ; [ RhCl (NH , ) , 1 ; or [ RhCl , py , ICI, respectively.

Ammines. Lebedinskii applied Alfred Werner’s co-ordination theory to rhodium(II1)

and predicted that all the members of the transition series (Obergangsreihe) between the hexa- ammines and the double salts must exist, namely [il [Rh(NH,),lX,, [iil [RhX(NH,) , IX, , [iiil [RhX, (NH,), IX, [ivl [RhX,(NH,),l, [vl M[RhX,(NH,),l, Ivil M,[RhX,NH,l, and [viil M,[RhX,l (where X = a uninegative anion and M = a monopositive cation). Therefore he set about devising syntheses for compounds of the unknown series [iiil, [ivl, [vl, and [vil. In 1933 he obtained (NH,),[RhCl,NH,I (series [vil) by boiling a Na,[RhCl,l solution with NH,CI and NH,C,H,O,, and he prepared the corresponding K+, Rb+, CS+, and [Pt(NH,),l’+ salts by metathesis (20). In 1935, together with Fedorov, he prepared compounds of the corresponding acetonitrile series M,[RhCl,CH,CNI (where M = NH,, K, Rb, Cs, Ag, or I / ~ [ P ~ ( N H , ) , I ~ +) (21).

In the same year Lebedinskii prepared [RhCl,(NH,),], a compound of the triammine series (series [ivl), by treating Na,[RhCl,I with NH,C,H,O, in the presence of HC,H,O, and NH,Cl(22). In this work he showed how, by varying the ratios of the reactants, the corresponding mono-, tetra-, and pentaammines could be obtained. In this way he obtained for the first time [RhCl,(NH,),lNO, .H,O (series [iiil). He concluded that rhodium(II1) ammines containing an odd number of ammonia molecules are much more stable and more easily synthesised than those containing an even number of ammonia molecules, probably because of the labilising action of anions in the trans position (Chernyaev’s trans effect) (7, 23). He also found that this relationship was true for iridium(II1) complexes.

Together with V. S. Volkov, Lebedinskii also prepared another triammine compound (series [ivl), namely [RhCl,(tu),l as well as the additional thiourea complexes [Rh(tu) 6 lC1 , and [RhCl(tu),]Cl, (24). In 1955, together with E. V. Shenderetskaya, he synthesised another triammine, [Rh(NO,),(NH,),I, by the reaction of ammonia with M,[RhCI,(NO,),I. In this reaction all three chlorine atoms, which are trans to the nitro groups are labilised by them


since the nitro groups exert a strong cram effect. In this and numerous other reactions, Lebedin- skii showed that Chernyaev’s trans effect, first developed for platinum complexes, also applies to rhodium complexes. Lebedinskii also prepared the nitroammine complexes “IN02 (NH3) j 1x2 (series bib, M[Rh(NO,),(NH,),l (series [vl, and M,[Rh(NO,),NH,l (series [vil) (25). He also prepared the compounds (NH,),Na[M(NO,),I (where M = Rh, Ir, or Co) (26).

Of the tetraammine series (series %I) only the [RhCl,py,lX series was known (27) until, as mentioned above, Lebedinskii obtained compounds of the [RhCl,py,lX series (22). He also synthesised the pyridine compounds M[Rh(NO,),py,l (where M = Na, NH,, (NH,),CNH,, or I/z[P~(NH,),I) (28), M[RhCl,NH,pyI (where M = pyH, Ag, or 1/2[Pt(NH3),I), reference (29a), and [RhCl,NH,py,] .1/2H,0 (29b). In contrast to the ammonia complexes, he found that the most stable and most easily synthesised of the pyridine complexes are those with an even number of ammonia molecules, a relationship that he also discovered for iridium(II1) complexes.

Lebedinskii and his co-workers also synthesised and characterised a large number of rhodium(II1) complexes containing the sulphito group or the NaS0,- ion in the first co- ordination sphere, such as the complexes M, [Rh(SO,) ,NaSO, (NH,) , 1 (where M = Na, 1/2Zn, 1/2Ba, I/zHg, or I/zFe) (30),

bc,de-[Rh(SO , Na) , (SO, 1 (NH , 1 1 (3 I d ,

Na [Rh( SO ,) , SO , Na(NH ,) , 1 * 6H 0 (3ra), M[Rh(SO,),(NH,),I (series G I ) (where M = K, NH,, or Na) (31b). (In solution, the Na salt is in equilibrium with [RhSO , (SO, NaXNH,), I , M , [Rh(SO,) , 1 (M = NH, or K) ( ~ I c ) , and M[Rh(SO,),(NH,),l (where M = K or (NH,),CNH,) (31c). Lebedinskii also devised a procedure for separating rhodium from iridium with KI (32a) and developed a high- yield synthesis for [RhCl(NH,),lCl, (32b). His research on the sulphito complexes of

A~,[R~(SO,),(NH,),I.I/~H~O (301, Na3 4

rhodium(III), specifically (NH,) , [Rh(SO,) , I ( ~ I c ) , was used as the basis for the industrial preparation of spectroscopically pure rhodium metal, a method widely used in Russian refineries (33).

Iridium Dimethylglyoxime Complexes. Lebedinskii

and Fedorov synthesised dimethylglyoxime complexes of iridium(II1) similar to those obtained with rhodium(II1) and cobalt(II1). These include M[IrCl,(DH),l(M = H, NH,, K,

M[Ir(NO,),(DH),I(M = H or NH,) (34b), H[IrNO,X(DH),I(X = Cl or SCN) (34b), [Ir(DH),(NH,),lX (X = I or picrate) (34c), and [Ir(DH),(tu),lI (34c). They deduced the configurations of the compounds on the basis of Chernyaev’s trans effect, which is valid for iridium compounds. For example, since the NH, molecule exhibits a higher degree of lability in the [Ir(DH) (NH,) , 1 + ion as compared with that of the C1 atom in the [Ir(DH) , C1 I - ion, they concluded that the two NH, molecules are in cis positions relative to each other and in tram positions relative to the =NO groups of the DH- groups (34c).

Amine and Ammine Complexes. In 1926 Lebedinskii prepared the first reported tris(ethy1enediamine) complexes of iridium(III), namely [Ir(en),lX, (where x = I, 1/2[PtCl,l, 1/2~PtCl,I, 1/2[Pt(CN),I, 1/2[PtBr I , 1/2IOsCl I , 1/4[Fe(CN) 1, or 1/3[Fe(CN),l, and en = ethylenediamine) (35). In 1938 he and N. A. Balitskaya prepared the first compounds of the monoammine series, M,[IrCl,NH,l (where M = K, NH,, Rb, or I/Z[P~(NH,),I) (36). The compounds are less susceptible to hydrolysis than the corresponding rhodium(II1) compounds (series [vil).

This monoammine series is analogous to the corresponding acetonitrile series M,[IrCl,CH,CNI (where M = NH,, K, (NH,),CNH,, or I /~[P~(NH,) , I ) (37). With thiourea (tu) Lebedinskii obtained (24) the compounds [IrCl, (tu) , I, [IrCl,(tu), ICl, [Ir- Cl(tu),ICl,, and [Ir(tu),ICl, (38), analogous to the corresponding rhodium(II1) compounds.

(NH,)zCNHz, or 1/2[WNH,),I) (341,


Sulphito Complexes. As in the case of rhodium(III), Lebedinskii and his colleagues made extensive studies of complexes of iridium(II1) with the sulphito and NaSO, - groups as ligands, using Chernyaev’s trans effect to elucidate the configurations (7, 23). With M. M. Gurin, he synthesised and characterised Na, [Ir( SO, Na)( SO ,) , (NH,) , I .7H , 0 (with NH, molecules cis to each other) (394; Na, [Ifll, (SO , 1 , 1 - 7H2 0 (39b), M[IrCl,(S0,)21~6H20 (M = NaRb, or K,) (39b), and Na,[IrCl,(SO,),l (3%). They also synthesised complexes in which the sulphito groups are mono- and bidentate in the same compound, for example, M,[IrCl,(S0,)21, M = K or NH, (if M = K the compound is Claus’ salt) (39d), and M[Ir(SO,),(NH,),l (M = K or 1/2Zn) (39d). The configurations for the two anions are:

so i so 1

Platinum The chemistry of platinum has been more

extensively investigated than that of any other of the platinum metals, and it played a prominent role in Werner’s development of his co- ordination theory from its very inception (41). As is well known, dipositive platinum has a co- ordination number of four and a square planar configuration, whereas tetrapositive platinum has a co-ordination number of six and an octa- hedral configuration.

Acetonitrile Complexes. In opposition to this generalisation, Lebedinskii and his mentor

Chugaev reported the preparation of two platinum(I1) complexes, which they claimed to be hexaco-ordinate, that is, to have a co-ordination number of six. They treated cis- and trans-[PtCl , (ac) , 1 (where ac = CH, CN, acetonitrile) with ammonia and obtained water- soluble, colourless chlorides, a- and P-[Pt(ac) , (NH,), lC1 , , which contained chlorine atoms, both of which were ionised in solution and replaceable by [PtCl,l’- and (C,H,0,N,)2- (picrate ions) (42a). Since the ammonia molecules were strongly combined in the new compounds, not being titratable with mineral acids, and since the ammonia could only be removed by boiling with hydrochloric acid, whereupon two molecules of ammonia and two molecules of acetonitrile were eliminated, the a-complex yielding czs-[PtCl,(NH,),I and the P-complex yielding trans-[PtCl,(NH,),], Chugaev and Lebedinskii assigned to these complexes the structures:

Although these compounds have been cited in the literature, for instance (43, M), as examples of hexaco-ordinate platinum(II), Lebedinskii and Golovnya later showed that these compounds, as well as the corresponding compounds that they had obtained with propionitrile, pn = C,H,CN, are better formulated as containing tetracovalent platinum(I1) in which two ammonia molecules are bonded to the nitrile molecules, for example, cis- or trans-[Pt(ac* . *NH,),(NH,),IX, (45a,b). As evidence against a co-ordination number of six, they cited the facts that excess ammonia reacts with compounds such as:

(containing only one molecule of acetonitrile)

Platinum Metals Rev., 1988, 32, ( 3 ) 145

to yield neither a tetraammine nor a hexa- ammine but a pseudopentaammine, [Pt(ac)(NH,),ICl? (which is actually [Pt(ac. * .NH,)(NH,),ICl,) (45a,b). They also cited the action of boiling hydrochloric acid solution on both [Pt(ac),(NH,),ICl, and [Pt(ac)(NH,),ICl, in splitting off, for each molecule of acetonitrile, one molecule of ammonia, whereby cis-[PtCl,(NH,),] or [PtCI(NH J ) ,lC1 is formed, respectively.

In addition, Chugaev and Lebedinskii prepared the compounds M[PtCI, (ac)] (where M = Kor I /~[R(NH,) , I ) , showing that acetonitrile reacts with soluble tetrachloroplati- nates(I1) just as ammonia and organic amines do (45b). Lebedinskii and Golovnya also prepared numerous complexes of platinum with acetonitrile or propionitrile, including cis-[PtCI (pn) , I, cis-[ PtCl (pn)NH , 1, [PtCl(pn)(NH,),lX (X = C1 or I), M[PtCI,pnl (M = Kor I/Z[R(NH,),I), [Pt(ac)(NH,),lX, (X = C1 or 112 picrate), [Pt(pn)(NH,),]X, (X = C1 or I/Z picrate), and [Pt(pn),(NH,),lCI,, and they found that propionitrile is less strongly bonded to platinum than is acetonitrile (45b). They also prepared “pseudohexaco-ordinate” complexes such as [PtX,A,l[PtCI,l (where X = ac or pn and A = methylamine, CH,NH,, or ethylamine, C,H,NH,) (45d, e) and devised new syntheses for known compounds such as K[PtCI , NH 1 and [ PtcI , (NH J ) , 1 (49).

Sulphito Complexes. In addition to their research on sulphito compounds of iridium, Lebedinskii and Novozhenyuk carried out similar studies with platinum, synthesising K4 [Pt(SO, ) 2 (SO 3 H) 1 1, M, [ PtCl2 SO 1 (SO 3 H)l

(where M = K or r/2IPt(NH3),1), and also [Pt(NH, 1 , 1 [PtW,) (NH, ) 1 ( 4 W K, Pt( so J ) J NH J 1, K, cis-[ R(S0 3 ) 2 py 1 , and [PtSO,(NH,),pyl (46b). They demonstrated that the bond between the sulphito group and the central atom is stronger when the group occupies one co-ordination position instead of two (46a), and that the sulphito group exerts a strong trans effect (46c). Together with R. K. Korabel’nik, Lebedinskii synthesised new platinum complexes with aminosulphonic acid, namely, and

Extraction and Analysis of Ores. Lebe- dinskii and Khlopin developed a method for preparing pure platinum by boiling the ore with aqua regia and then precipitating the platinum as ammonium hexachloroplatinate(IV), (NH,),[PtCI,I, by the addition of ammonium chloride (48). As a member of the Analytical Commission of the Platinum Institute, Lebe- dinskii was involved in the development of several methods for analysing platinum ores (49, 50) as well as the extraction, separation and refining of the platinum metals. He also developed a spectroscopic method for detecting the presence of platinum in sulphur ores (51).

For some forty years Viacheslav Vasil’evich Lebedinskii was involved in research on the chemistry of the platinum metals. Although he is credited with the development of new industrial processes, much of his work was of a highly academic nature, so reinforcing the position of Russians at the forefront of platinum metals research. By his teaching he contributed to the continuation of this great tradition.

K[ Pt(NH , SO ,)C1 , NH , 1 [ W N H , SO, )Cl(NH,) 11 (47).

References

I “Metal Statistics 1986”, 79th Edn., Fairchild Publications, New York, 1986, p. 125

2 (a) Anon., Philos. Mag., 1828, (2), 4, 458; (b) D. McDonald and L. B. Hunt, “A History of Platinum and its Allied Metals”, Johnson Matthey, London, 1982, Ch. 13

3 B. N. Menshutkin, lev. Sektora Platiny i Drug. Blagomdn. Metal., Inst. Obshch. i Neorg. Khim., Akad. Nauk S . S . S . R . (hereafter abbreviated I zv . ) , 1928, 6 , I - I O ; ~ . Chem. Educ., 1934, XI, 226-229

4 M. E. Weeks, rev. by H. M. Leicester, “Dis- covery of the Elements”, ;rth Edn., Journal of Chemical Education, Easton, PA, 1968, pp. 418-425

5 G. B. Kauffman, Platinum Metals Rev. , 1974,18, (4), 142-149; V. V. Lebedinskii, Izv., 1924, 3, 81-84

6 R. Gilchrist, Chem. Rev. , 1943, 32, 277-372 7 G. B. Kauffman, 3. Chem. Educ., 1963, 40,

656-665; Platinum Metals Rev. , 1973, 17, (4), 144-148

Platinum Metals Rev. , 1988, 32, (3) 146

8 G. B. Kauffman, Platinum Metals Rev., 1976, 20, (4), 126-130; 3. Chem. Educ., 1977, 54, 86-89; V. A. Golovnya, T. N. Leonova, W. Craig and G. B. Kauffman, Ambix, 1976, 23, 187-198

9 0. E. Zvyagintsev, Zh. Neorg. Khim., 1957, 2,

1713-1719 10 L. A. Chugaev and V. V. Lebedinskii, Zh. Russ.

Fiz. Khim. Obshch., 1913, 45, 648 11 G. B. Kauffman and A. Beck, 3. Chem. Educ.,

1962, 39, 44-49; G. B. Kauffman, Platinum Metals Rev. , 1982, 26, (3), 129-133; Polyhedron, 1983, 2, 855-863

12 V. V. Lebedinskii and B. N. Ivanov-Emin, (a) Zh. Obshch. Khim., 1943, 13, 253-265; (b) Zh. Neorg. Khim., 1959, 4, 1762-1767

13 (a) V. V. Lebedinskii, I. S. Rassonskaya and S. N. Avakyan, Dokl. Akad. Nuuk S.S.S.R., 1954, 94,245-248; V. V. Lebedinskiiand S. N. Avakyan, Izv. Akad. Nauk Annyan. S.S.R., Khim. Nauki, 1958, 11, 321-325; (b) 1959, 1% 91-93

14 V. V. Lebedinskii, (a) Usp. Khim., 1943, 12, 245-255; (b) Izv., 1948, 21, 18-26; (c) V. V. Lebedinskii and A. M. Rubenshtein, Usp. Khim.,

15 V. V. Lebedinskii, P. V. Simanovskii and 0. D. Slutsker, Izv., 1948, 21, 43-53

16 L. A. Chugaev, Z . anorg. Chem., 1905, 46, 144-169; Ber., 1905, 38, 2520-2522

17 L. Tschugaeff and W. Lebedinskii, Z . anorg. Chem., 1913, 83, 1-7

18 V. V. Lebedinskii and I. A. Fedorov, Izv., 1938,

19 V. V. Lebedinskii and I. A. Fedorov, Izv., (a)

20 V. V. Lebedinskii, Izv., 1933, 11, 5-12

21 V. V. Lebedinskii and I. A. Fedorov, Izv., 1935,

22 V. V. Lebedinskii, Izv., 1935, 12, 67-77 23 1. I. Chernyaev, Izv., 1927, 5 , 118-156; for an

annotated English trans]. see G. B. Kauffman, “Classics in Coordination Chemistry, Part 3; Twentieth-Century Papers (1904-1935)”, Dover Publications, New York, 1978, pp. 151-195

24 V. V. Lebedinskii and V. S. Volkov, Izv., 1935,

25 V. V. Lebedinskii and E. V. Shenderetskaya,


27 S. M. Jqirgensen, 3. prakt. Chem., 1883, [21, 27, 433-489

28 V. V. Lebedinskii and S. F. Silm, Izv., 1937,14, 33-39

29 N. A. Vargunin, N. S. Kurnakova and V. V. Lebedinskii, Sb. Nauch. Trudou.Kramoyarsk.Med. Inst., (a) 1958, ( 5 ) , 97-101; (b) ibid., 101-IOZ

30 V. V. Lebedinskii and N. N. Myasoedov, Izv., 1939, 1.6, 65-76


1953, 22, 241-252

15, 19-25

1948, 21, 157-163; (b) 1948, 21, 158-167

12, 87-92

12, 79-86

Izv., (a) 1945, 18, 19-22; (b) 1955, 31, 53-55

Im., 1955, 29, 61-65

Izv., (a) 1948,21,!64-174; (b) 1955,30,99-105; (c) Zh. Neorg. Khtm., 1957, 2, 1768-1774

32 V. V. Lebedinskii, Izv., (a) 1927, 5 , 364; (b)

33 V. V. Lebedinskii, E. V. Shenderetskaya and A. G. Maiorova, Chist. Metal. i Polupmod. , Tr. 1-oi [Pewoil Mezhvuz. Konf., Moscow, 1957,235-238 (published in 1959); Zh. Prikl. Khim., 1959, 32, 928-929

34 V. V. Lebedinskii and I. A. Fedorov, Izv., (a) 1938, 15, 27-34; (b) 1945, 18, 23-30; (c) ibid., 31-37

1936, 13, 9-17

35 V. V. Lebedinskii, Izv., 1926, 4, 235-242 36 V. V. Lebedinskii and N. A. Balitskaya, Izv.,

37 V. V. Lebedinskii and P. V. Simanovskii, Izv., 1939, 16, 53-56

38 V. V. Lebedinskii, E. S. Shapiro and N. P. Kasatkina, I.., 1935, 12, 93-102

39 V. V. LebedinskiiandM. M. Gurin, Compt. rend. acad. sci. U.R.S.S., (a) 1941, 33, 241-243; (b)

40, 322-325 (all III English) 40 V. V. Lebedinskii and Z. M. Novozhenyuk, Izv.,

(a) 1955, 29, 66-76; (b) 1956, 30, 106-108; (c) Zh. Neorg. Khim., 1957, 2, 249--2491; (d) 1958, 3, 286-291; (e) 1958, 3, 2462-2466

41 A. Werner, Z . anorg. Chem., 1893, 3, 267-330; for an annotated English translation see G. B. Kauffman, “Classics in Coordination Chemistry, Part I: The Selected Papers of Alfred Werner”, Dover Publications, New York, 1968, pp. 5-88

42 L. Chugaev and W. Lebedinski, Compt. rend., (a) 1915, 161, 563-564; (b) 1916, 162, 43-45

43 A. Werner, “Neuere Anschauungen auf dem Gebiete der anorganischen Chemie”, rev. and ed. by P. Pfeiffer, Friedrich Vieweg, Braunschweig,

4 P. Pfeiffer, in “Stereochemie”, ed. K. Freuden- berg, Franz Deuticke, Leipzig, Vienna, 1933, p. 1252

45 V. V. Lebedinskii and V. A. Golovnya, I . . , (a) 1939, 16, 57-64; (b) 1945, 18, 38-49; (c) 1947, 20, 95-98; (d) 1948, 21, 32-42; (e) 1948, 22,

46 V. V. Lebedinskii and Z. M. Novozhenyuk, (a) Izv., 1951, 26, 83-94; (b) 1952, 27, 80-88; (c) 1952, 273 89-98

47 V. V. Lebedinskii and R. K. Korabel’nik, Izv., 1947, 20, 99-106

48 V. V. Lebedinskii and V. G. Khlopin, Izv., 1926, 4, 317-323

49 S. F. Zhemchuzhnii, 0. E. Zvyagintsev, B. G. Karpov, V. V. Lebedinskii and N. I. Podkopaev, Im.9 1926, 4, 339; 1926, 4, 340-343; 1926, 4, 355-359

50 A. T. Grigoriev, S. F. Zhemchuzhnii, 0. E. Zvyagintsev, B. G. Karpov, N. S. Kurnakov, V. V. Lebedinskii and N. I. Podkopaev, Izv., 1926, 4, 343-355

51 0. E. Zvyagintsev, V. V. Lebedinskii and A. N. Fdippov, Compt. rend. acad. sci. U.R.S.S., 1933,

1938, 15, 13-18

I942,36, 21-25; (0 1943,383 128-130; (4 1943,

1923, p. I 8 1

168- I 74

I 65 -I 69


ABSTRACTS of current literature on the platinum metals

PROPERTIES Metal Substrates Wetting by Indium. 11. In-Pt System J . JANDOVA and J . D U ~ N , Kovovi Mater., 1988, 26, (I), 71-75 Studies of Pt wettability by liquid In at 4w°C showed that after 30 min In fully dissolved in Pt forming In,Pt intermetallic compound. The wetting angle during the starting period (the first 30 mh) was determined as 86k3 rad.

Thermally and Ion-Induced Reaction between Si and Binary Metallic Alloys L. S. HUNG, Q. 2. HONC and J. W . MAYER, J . Appl. phyx., 1988, 63, ( 5 ) , 1749-1753 Thermally and ion-induced reactions between Si and binary alloys PtV (solid solution), PtTi (intermetallic compound) and NiTa (amorphous phase), of approximately equiatomic compositions, were investigated. Thermal annealing was performed at ~w-700°C. Separated binary silicides were formed in the Pt-V and Ni-Ta systems, while ternary compound PtTiSi was observed in the Pt-Ti system. Ion irradiation was performed at 2w-4w°C. Uniform mixed amorphous layers were produced in all three systems upon irradiation at relatively low temperatures. Mixtures PtVSi, and NiTaSi, were transformed to separated binary silicides by post-annealing, but the PtTiSi, underwent an amorphous-metastable phase transformation. Thus the dominance of Si motion with the non-equilibrium nature of ion mixing can be used to produce metastable phases in the ternary system.

The Influence of Oxygen on the Selectivi- ty of Alcohol Conversion on the Pd( 11 1) Surface J. L. DAVIS and M. A. BARTEAU, surf. SCl., 1988, 197, (1/2), 123-152 The reactions of methanol, ethanol, I-propanol and 2-propanol were studied on a Pd(11x) surface containing one-quarter monolayer of adsorbed 0 atoms. Methanol was oxidised on the 0-dosed Pd( I I I) surface to formaldehyde and surface formate species. The adsorption of ethanol on the 0-dosed Pd( I I I) surface resulted in the desorption of acetaldehyde at 220K and the formation of surface acetate species. Adsorbed acetate species reacted, via either decomposition at 41oK or hydrogenation, to acetic acid at 280K. The relative importance of the two acetate reaction channels was found to depend on the availability of surface H. Similarly, the adsorption of 1-propanol on O/Pd(x 11) produced both propanal and adsorbed propanoate species. The roles of 0 adatoms in these reactions were discussed.

The the

and their alloys

Effect of Nitrogen Implantation on Tribolodcal Properties of Gold-

Based AlGys and Electroplated Palladium P. w. LEECH, IEEE Trans. Components, Hybrids, Manuf. Technol., 1988, 11, (I), 16-21 The effect of N , + ion implantation on the friction and wear behaviour of 30%Pd-29.~~/oAg-1 .s%Sn-Au, 26%Ag-3%Ni-Au and B%Ag-Au alloys and electroplated Pd was studied. Rider-on-flat experiments showed that N , + implantation in either the rider in B%Ag-Au or the flat in the remaining alloys produced a significant reduction in the coefficient of friction and in the extent of surface wear sustained during sliding. Layers of electroplated Pd showed only minor changes in friction and in sliding damage to the flat following N , + implantation of both surfaces.

Change of Structure and Properties during Annealing of Cold Worked Pd-Fe Alloy E. I. TEITEL’ and G. M. GUSHCHIN, Fiz.Met.Metallov- ed., 1988, 65, (21, 332-340 Structural changes and their effect on elec- troresistance, magnetic and mechanical properties were studied during annealing of cold worked Pd-Fe alloys at 5 0 0 O C . The results showed formation of dispersed ordered domains, recovery and recrystallisation, forming super-fine dispersed grains with a high level of tensile order. Recrystallised grains showed an increased density, dislocation and twin deformation due to interaction with the ordered matrix which appeared in the elastic-tension state. The mechanism of the kinetics of changes in elec- troresistance, coercive force and mechanical properties connected with the structural state of the alloys were discussed.

Hydrogen Solubility and the Equilibrium Pressure-Composition Isotherm for Pd- Eu Alloys s. T. AL-ASHAB and I , R. HARRIS, Int.J.Hydrogen E n e w , 1988, 13, (3), 191-194 The H, solubility and the equilibrium pressure of Pd-Eu alloys were studied. The microbalance-H system was used to determine the pressure- composition isotherm curves of the Pd-Eu-H alloy system containing 1.3 and 5%Eu in a range o to 7 atmospheric pressure and at room temperature up to 400OC. The hysteresis phenomena became smaller as the Eu content increased. The effect of Eu content on the partial molar enthalpy and entropy of absorption of mole of H(AH,,AS,) and the miscibility gap were discussed. The strain energy of Pd-Eu-H was less than that of Pd-Ce-H and more than of Pd-Pb-H.

Platinum Metals Rev. , 1988, 32, (3), 148-159 148

Growth Kinetics of Palladium Silicides Formed by Rapid Thermal Annealing

Electmchem. SOC., 1988, 135, (2), 446-451 Pd,Si is formed through direct reaction of an electron-evaporated Pd thin fdm and single-crystal <roo> Si substrate by rapid thermal annealing. The sample temperatures were measured by a variety of means, and the maximum sample temperatures, were 310-460OC. Pd,Si is the first and only phase in this range and forms at 320OC. The activation energy for the diffusion-controlled silicide growth is I .420.2eV. Thus the growth mechanism of Pd ! Si is the same in both rapid thermal annealing and conventional furnace annealing.

Reordering of Polycrystalline Pd2 Si on Epitaxial Pd Si

J.Appl.Phys., 1988, 63, (7), 2402-2405 Polycrystalline Pd , Si was found to reorder on top of epitaxial Pd, Si during silicide growth. The interface between polycrystalline Pd , Si and epitaxial Pd , Si was thus not immobile with respect to the silicide lattice during silicide formation. It was not, therefore, possible to use this interface as a structural marker in order to monitor diffusion in epitaxial Pd, Si. The use of Ti as an inert marker showed that Si was the domi- nant diffusing species in epitaxial Pd,Si during silicide formation.

Ultrasonic Study of Mechanically Alloyed Amorphous PdSiCu A. HIKATA, M. 1. MCKENNA and c . ELBAUM, 3. Appl.Phys., 1988, 63, (6), 1910-1913 An amorphous alloy Pd,,,, Sio,,6sCuo.a has been produced by a mechanical alloying process which involves repeatedly deforming, fragmenting and cold welding appropriate amounts of the constituent powders by milling with steel balls in an argon atmosphere, at around room temperature. X-ray diffraction indicates that amorphisation proceeds rapidly with time; no further changes are apparent after milling for 8 hours. This alloy has ultrasonic characteristics typical of an amorphous alloy of similar composition produced by rapid solidification, indicating that a very fast diffusion mechanism has taken place.

Heavy-Fermion Mixed-Valent Behaviour in YbPdSb and YbPdBi s. K. DHAR, N. NAMBUDRIPAD and R. VIJAYARAGHAVAN, J.Phys.F, 1988, 3, (IS), h 1 - U Measurements were made at low temperatures of the heat capacity at 2-20K and magnetic susceptibility at 4.2-300K in the cubic compounds YbPdSb and YbPdBi. From the linear portion of plots of C/T against T,, a y value of 470 and z40mJ/molKz was obtained for YbPdBi and YbPdSb, respectively. The magnetic susceptibility results reflected the fluc- tuating nature of the valence of Yb ions in both compounds.

C. S. WEI, J. VAN DER SPIEGEL and J. J . SANTIAGO, J .

C. M. COMRIE, 1. C. LIU, L. S. HUNG and J. W. MAYER,

A Comparison of the Desorption of CO from Pt and Rh Particles on a- A1,0,{0001} E. I. ALTMAN and R. J. GORTE, surf. sci . , 1988, 195, (3), 392-402 The adsorption of CO on Rh particles supported on (Y-AI, O,{ooor} was studied using temperature pro- grammed desorption. The Rh was evaporated onto the non-porous a-AI,O, substrate in ultra-high vacuum and metal coverage was measured using a quartz-crystal, fdm thickness monitor. Spectroscopic studies showed that Rh grew as three-dimensional particles on the alumina substrate at 3ooK. For all Rh particle sizes studied, CO desorbed in peaks at 500 and 425K, which were the same temperatures observed on Rh foils and single crystals.

Kinetics of CO Oxidation by O 2 or NO on Rh( 11 1) and Rh( 100) Single Crystals

BERLOWITZ, G. B. FISHER and s. H. OH, J. Phys. Chem., 1988, 92, (6), 1563-1567 The oxidation of CO by 0, or NO over Rh( I I I ) and R h ( 1 o o ) single crystals was studied in a high-pressure reaction high-vacuum surface analysis apparatus. Steady-state catalytic activity as a function of temperature and partial pressures of CO, 0, and NO was measured. The CO-0, reaction was insensitive to the structure of the surface as shown by the identical rates, activation energies, and partial pressure dependencies measured on the two single-crystal surfaces. Deactivation occurred at a slightly lower 0, partial pressure on Rh(~oo), which was possibly due to the relative ease of formation of the bulk oxide via diffusion of oxygen through this surface. In contrast to the CO-0, reaction, the rate of CO oxidation by NO is dramatically different on the two single-crystal surfaces studied.

Paramagnetic Rhodium Species in Zeolites. Part I. RhNa-X and RhNa-Y A. SAYARI, J . R. MORTON and K. F. PRESTON, 3. Chem. SOC., Faraday Trans. I , 1988, 84, (2), 4 1 3 - 4 3 1

Five different paramagnetic Rh"species were stabilis- ed following activation by flowing 0, at 2oo-475OC in ion-exchanged RhNa-Y samples prepared either from [Rh(NH,),ClICI, (sample I) or from Rhcl, .3H, 0 (sample 11). The condition of formation of these species, their stability and their possible loca- tions were studied.

X-Ray Investigations in the Systems Ruthenium-Silicon and Ruthenium- Silicon-Nitrogen F. WEITZER, P. ROGL and J . c. SCHUSTER, Z . Metallkd., 1988, 79, (3), 154-156 X-ray studies of the ternary system Ru-Si-N and its binary system Ru-Si showed that no ternary phase was found to exist at temperatures of 1 o o o - 1 2 5 o o C in the absence of external nitrogen pressure. Isothermal sections for the ternary system were given. A new phase diagram for the binary Ru-Si is proposed.

C. H. F. PEDEN, D. W. GOODMAN, D. S. BLAIR, P. J.


Thermochemistry of the Intermetallic Compounds RuTi, RuZr, and RuHf L. TOPOR and 0. J . KLEPPA, Meiall. Trans. A, 1988, 19A, (4), 1061-1066 The standard enthalpies of formation of RuTi, RuZr and RuHf have been determined by high temperature mixing calorimetry at 1400K, as - 153.9k7.4,-137.326.8 and -183.5210.4 kJ/mol, respectively. These are the first experimentally measured enthalpies of formation for these in- termetallics that have been reported; and they are compared with calculated values and values of equiatomic alloys of Pd and Rh with Ti, Zr and Hf.

CHEMICAL COMPOUNDS Mixed Platinum-Gold Clusters. Synthesis, Structure and Properties of

J . J . BOUR, R. P. F. KANTERS, P. P . J. SCHLEBOS and J . J . STEGGERDA, Recl. Trav. Chim. Pays-Bas, 1988, 107, (3), 211-215 The mixed Pt-Au cluster P ~ A u , ( P P ~ , ) ~ ( N O , ) , was formed by the reaction of H, with Au(PPh,)NO, and either Pt(PPh j ) , or Pt(COD)(NO ,) ,. The metal frame is a centred crown with a phosphine bonded to each peripheral metal atom. Spectroscopic studies showed that Pt is in the centre and that the 8 Au atoms are on the crown. An electrochemical study showed that the cluster could be reduced in two reversible one-electron steps at - 1.14 and - 1.29V.

The Reaction of a Zwitterionic Diphosphorus Compound with the Platinum(0) Complex, (C H,)Pt(PPh3)2

RAY and D. SCHOMBURG, Polyhedron, 1988, 7, (7), 505-512 The oxidation-reduction reaction between a zwitterionic diphos horus compound, involving the grouping Cl-@-eP( +)-NEt with the Pt(o) complex, (C,H,)Pt(PPh,), , produced a novel Pt(I1) complex with a Pt-P four-membered ring. The identity and structure of this Pt complex was determined by NMR and by single-crystal X-ray study.

Na2PdH,, A Hydride with a Novel Linear [PdH 1 Complex

PtAu 8 (PPh3) 8 (NO 3 ) 2

P. LOOK, R. SCHMUTZLER, R. GOODFELLOW, M. MUR-

D. NOREUS, K. W. TbRNROOS, A. BbRJE, T. SZABO, W. BRONGER, H. SPITTANK, G. AUFFERMANN and P. MOLLER, J. Less-Common Met., 1988, 139, (2), 233-239 The ternary hydride Na,PdH, was prepared by the reaction of Na hydride with Pd in a hydrogen at- mospere at 37oOC. The structure was derived from X-ray studies on powdered samples and on a single crystal as well as from neutron diffraction experiments on the deuterated compound. Na,PdH, crystallised in the tetragonal space group I4/mmm and was isotypic with Na,HgO,. The atomic arrangement was a novel linear [PdH,l complex.

Novel Reaction of an Iridium Carbonyl Complex with Xenon Difluoride: the First Metal Fluoroacyl Complex A. J. BLAKE, R. w . COCKMAN, E. A . v. EBSWORTH and J. H. HOLLOWAY, J . Chem. SOC., Chem. Commun.,

The cation [Ir(CO) ,(PEt ,)] 1 + reacted smoothly with XeF, at 273K in CH,CI, to give the novel species [Ir(CO),F(COF)(PEt,),l+ (I) in high yields. The product (I) is the first fluoroacyl complex described and is stable at room temperature in the absence of air and moisture. It was isolated as BF,- and PF,- salts and was characterised spectroscopically, crystallographically and by partial elemental analysis. The product (I) has considerable potential as a synthetic intermediate.

Surface-Mediated Organometallic Syn- thesis: Formation of [Os, C(C0) I - from [OS~(CO),~] on MgO

GATES, 3. Chem. soc., Chem. Commun., 1988, ( 5 ) , 371-372 A simple one-step high yield synthesis of [Os,C(CO),,lz- from [Os,(CO),,l conversion on the surface of partially dehydroxylated MgO under I bar of flowing CO at 550 K is reported. This synthesis is far simpler and gives much higher yields of about 65% than the conventional synthesis. Previous- ly the production was multistep and required tedious separations. Surface mediated synthesis may find wide application in organometallic chemistry.

Energy Transfer and Highly Resolved Emission of [Ru, -xOs,(bpy)31(PF,)2 H. YERSIN, G . HENSLER and E. GALLHUBER, 9. Lumin., 1988, (40 i? 411, 676-677 The emission properties of the title compound were studied at T=2K and high magnetic fields. The radiationless energy transfer from the [Rul-host to the IOsl-guest was governed by a fast process and a slow one, which showed a relatively ineffective transfer in the host material.

19889 (8), 529-530

A. S. FUNG, P. A. TOOLEY, M. J . KELLEY and B. C.

ELECTROCHEMISTRY Effect of Tin Adatoms on the Electro- oxidation of Ethylene Glycol on a Platinum Electrode 0. A. PETRII and N. v. SMIRNOVA, Electrokhimiya, 1988, 24, (4, 522-526 Electro-oxidation of ethylene glycol was studied on a platinised Pt electrode modified by Sn adatoms, in acid and alkaline media under stationary conditions. The results showed that electro-oxidation of ethylene glycol greatly increased in the presence of Sn adatoms which was due to the oxide-absorbing character of Sn adatoms. It is shown, that adatoms affect changes in the character of oxidation of chemisorbed ethylene glycol products and cause the disappearance of high charge effect.

Platinum Metals Rev. , 1988, 32, ( 3 ) 150

Metal Electrodes Bonded on Solid Polymer Electrolyte Membranes (SPE). V. Methanol Oxidation on Pt-SPE Electrode H. NAKAJIMA and H. KITA, Electrochim. Acta, 1988, 33, (4, S~I -526 Direct methanol oxidation from the gas phase was studied on a Pt-SPE electrode. The voltammogram and Tafel plots showed that a Pt metal electrode in electrolyte solution and the present Pt-SPE electrode both behave in the same way for methanol oxidation. However, the Pt-SPE electrode produces a 10’ times larger oxidation current, and does not deactivate after a few hours polarisation. The burning efficiency of methanol was studied as functions of the potential and the partial pressures of methanol and water. An excess supply of methanol resulted in the production of HCOOCH, in an amount almost equal to CO, . At a low methanol pressure, complete combustion took place independent of the potential.

Interfacial Electron-Transfer Reactions between Platinum Colloids and Reducing Radicals in Aqueous Solution

RICHOUX and J. M. THOMAS, 3. Phys. Chem., 1 9 8 8 , 9 2 , ( 5 ) , 1286-1290

Cyclic voltammetry was used to evaluate redox poten- tials, diffusion coefficients and heterogeneous electrochemical rate constants for reducing radicals derived from various N-methylbipyridinium ions, N- methylpyridinium ions, aryl ketones and p- nitrobenzoate ion in aqueous solution. The absorption spectra, rates of formation and stabilities of the radicals were found by pulse radiolytic techniques. All these radicals transfer an electron to colloidal Pt particles and the bimolecular rate constants were measured. The size of these rate constants depends upon a number of factors related to mass-transfer and surface processes. The orientation of the support on the metal surface could play a crucial role in the rate of interfacial electron transfer.

A. HARRIMAN, G. R. MILLWARD, P. NETA, M. C.

Permeation of Gases through Po- ly(Ethy1ene Terephthalate) Membranes Metallized with Palladium

URSU, 3. Membrane Sci., 1988, 35, (3), 2 9 1 - 3 0 0

Studies were made of the permeations of He, H,, CO,, Ar and N, at 5o°C through poly(ethy1ene terephthalate) (PET) membranes metallised with Pd layers of I z S - I o o o h thickness. It was shown that the Pd layers act as gas barriers which reduce the rate of gas transfer through the polymer by over one order of magnitude. The fact that the Pd layers failed to be perfect gas barriers was attributed to the presence of defects in the structure.

Auger Electron Spectroscopy and Elec- trochemical Characterization of Au-Pd System in 1 M H 2 S 0 ,

SurJCoat. Technol., 1988 , 34, (z), 1 4 1 - 1 4 4

An electrochemical study of the Au-Pd system was performed by measuring the 0 electrosorption properties of Pd surfaces coated with Au by vacuum deposition, in I M H,SO, at 25OC. The properties differed from those of Pd-Au alloy. The crater edge profiles showed an interface a few hgstroms thick of a Pd enriched layer, very close to the surface. Bet- ween this interface and the bulk of the electrode, Au was predominant, but with a great amount of Pd forming a mixture with the Au.

Electrochemical Studies of Hydrogen in Ordered and Disordered Pd,Mn Alloy K. BABA, Y. SAKAMOTO and T. B. FLANAGAN, 3. Chem. SOC., Faraday Trans. I , 1988, 84, (z), 459-466 The solubility of H in ordered and disordered forms of Pd,Mn was studied by electrode potential and electrical resistance measurements following electrochemical introduction of H. The solubility of H in the ordered state was higher than in the disordered state. Diffusion constants were measured, and it was found that the diffusion constant in the disordered

P. MERCEA, L. MURESAN, V. MECEA, D. SILIPAS and I.

1. GENESCd, M. E. GAMBOA and L. COTA-ARAIZA,

Methanol Oxidation on Unsupported and Carbon Supported Pt + Ru Anodes

form was about a factor of four greater than that for the ordered form at 312K.

J. B. COODENOUGH, A. HAMNETT, B. 1. KENNEDY, R. MANOHARAN and s. A. WEEKS, 3. Electroanal. Chem. Interfacial Electrochem., 1988, 240, (I/z), 133-145 A novel Pt+Ru electrode material was shown to be highly active for the direct electro-oxidation of methanol in H, SO, solutions, and had little tendency to poison. Spectroscopic study of this material before use as an anode showed that the Ru was oxidised and that there was an important surface concentration of oxidised Pt. After prolonged use as a methanol-oxidation anode, the concentration of oxidised Pt was somewhat increased and there was no evidence for any Pt-CO or Pt, =CO species; rather adsorbed formate was present. Dispersion of the Pt-Ru on a pure C support showed a much greater performance per gram of precious metal. The initial increase in over- potential was, however, greater by over IoomV.

Change in the Catalytic Activity and Hydrogen Permeability of the Membrane Catalyst from Palladium-Ruthenium Alloy Induced by Reagents

and v. M. GRYAZNOV, Im, Akad. Nauk SSSR, Ser. Khim., 1988, (4), 750-755 Studies of catalytic activity and H, permeability in 9.8OhRu-Pd membrane catalysts made during the hydrogenations of cyclopentadiene, cyclooctadiene, isoprene and the hydrogenolysis of propane at 373-573K showed catalytic corrosion of Pd-Ru membrane catalyst determined by nature of reagants. Oxidative-reductive treatment changed in much smaller degree the surface structure, catalytic activity and H , permeability than alternative treatment.

M. M. ERMILOVA, N. V. OREKHOVA, E. V. SKAKUNOVA


The Kinetics of Charging and Discharg- ing of Iridium Oxide Films in Aqueous and Non-Aqueous Media P. G . PICKUP and v. I . B I R S S , ~ . Elecrroanal. Chem. In- terfacial. Electrochem., 1988, 240, ( ~ h ) , 185-199 The kinetics of oxidation and reduction of electrochemically generated Ir oxide fdms in H,SO,, basic aqueous LiCIO, solutions and LiCIO, + acetonitrile solutions were studied by cyclic voltammetry and chronocoulometry. In acidic and basic aqueous solutions, chronocoulometric measurements showed that electron transport through the oxide was rate limiting for the main redox wave, whereas ion transport probably limits the charging/discharging kinetics in LiClO, + CH, CN solution.

Characterisation of Oxygen Evolving DSA Type Electrode. 1. TilIrO -Ta 0 Electrode

HINDEN, Electrochim. Acta, 1988, 33, (4), 573-580 Morphological and crystal structure studies of 0, evolving DSA electrodes Ti/IrO,-Ta,O, showed ag- glomerates of epitaxial crystals of IrO, in the deposits. The catalytic activity and efficiency of the electrodes were a maximum for a composition containing 7o%IrO, and 3o%Ta,O,. An increase in catalytic activity and efficiency was due to Ta,O, addition to the deposit, which resulted in an increase in the number of electrochemically active sites formed.

Electrochemical Reduction of Carbon Dioxide. Characterization of the Forma- tion of Methane at Ru Electrodes in Car- bon Dioxide Saturated Aqueous Solution

R. ROLEWICZ, CH. COMNINELLIS, E. PLATINER and J .

D. P . SUMMERS and K. W. FRESE, Langmuir, 1988, 4, (I), 51-57 The electrochemical reduction of CO, to CH, on electroplated Ru electrodes was studied. Scanning electron micrographs showed that the surface of such an electrode was made up of fused spheroids of Ru divided by a network of cracks. The variations of the CH, formation rate with pH showed that the rate increase with decreasing pH was due to an increasing H coverage on the electrode, until the coverage became so high that sites for CH, formation were blocked.

Formation of Bromates at a RuO /Ti0 Titanium Anode 0. f. PAVLOVIC, N. v. KRSTAJIC and M. D. SPASOJEVIC, Surf. Coat. Technol., 1988, 34, (2), 177-179 The production of Na bromate by electrolysis of con- centrated Na bromide solution in a cell without a diaphragm using a RuO,/TiO, Ti anode was studied. The RuO,/TiO, active coating for the Ti anode was obtained by thermal decomposition of a salt mixture of RuCl, .3H,O and TiCI, in isopropanol. The current efficiency was high at 98-99Oh when the pH of the solution was maintained at 8.5-9.5 in the presence of Na , Cr , 0 , .

PHOTOCONVERSION A Model of Photon-Induced Self-Driven Electrochemical Cell for Water Splitting to Hydrogen

Int. J . Hydrogen Energy, 1988, 13, (4), 225-230 An equation for the cell current in a self-driven photon-induced electrochemical cell, with semiconducting photoelectrodes as the electrodes, has been derived and applied to H 0 splitting to H, . The cell current and cell potential depend on semiconductor properties and the properties of ions in solution. Computed results show the same trends as experiments. Calculations suggest that an efficiency in the conversion of light up to 18% for H , 0 splitting to H, may be possible for p-InP(Pt-electrocatalyst)/n- Si(electrocata1yst).

Effect of Microscopic Discontinuity of Metal Overlayers on the Photovoltages in Metal-Coated Semiconductor-Liquid Junction Photoelectrochemical Cells for Efficient Solar Energy Conversion

J.Phys.Chem., 1988, 92, (8), 2316-2324 The open circuit photovoltage of a photoelectrochemical cell with a Pt-coated n-Si semiconductor electrode remarkably increased when the Pt layer was made microscopically discontinuous. An open circuit voltage of 0.685 V was obtained for an alkali-etched n-Si electrode with Pt islands 5-2onm,wide.

Exciplexee of Ruthenium(I1) a-Diimine Complexes with Silver(1) N. P. AYALA, J . N. DEW and v . A. DEGRAFF, J.Am.Chem.Soc., 1988, 110, ( 5 ) , 1523-1529 Luminescence “quenching” of RuL,?+, where L=s,i’-bipyridine and 4,7-dimethyI-1,1o-phenanthroline, photosensitisers by Ag + in aqueous solutions proceeds not by oxidative transfer quenching, but predominantly by formation of luminescent ex- ciplexes. The photochemih formation of Ago(aq) is (0.02 in H,O and (0.05 in acetonitrile. Both form a normal bimolecular exciplex, *(RuL, /Ag) )+, and a rare termolecular *(RuL, /Ag,)‘+ exciplex is seen.

Photochemical C 0 2 Reduction by an NADH Model Compound in the Presence of [Ru(bpy) I 2+ and [Ru(bpy) (CO) I 2+

(bpy= 2,2 ’-bipyridine) in H20/DMF H. ISHIDA, K. TANAKA and T. TANAKA, Chem. Lerr.Jpn., 1988, (2), 339-342 Photochemical conversion of CO, to CO and HCOO- was carried out by using nicotinamide adenine dinucleotide model compound, I -benzyl- 1,4-dihydronicotinamide, as an electron donor in the presence of [Ru(bpy)31’+ and [Ru(bpy),(CO),I’+ in H,O/DMF. The quantum yields for the CO and HCOO- formation attained 14.8 and 2.7%, respectively, in H,O/DMF (1:9 v/v).

S. U . M. KHAN, R. C. KAINTHLA and J. O’M. BOCKRIS,

Y. NAKATO, K. UEDA, H. YANO and H. TSUBOMURA,


Energy Redistribution and Localization in the Excited States of Ruthenium(I1) Polypyridyl Complexes

and 1. VAN HOUTEN, Inorg. Chem., 1988, 17, (4),

Excited state absorption and resonance Raman spectra of the mixed ligand complexes Ru(bpy),phen, +

and Ru(bpy),DIP’ +, where DIP = 4,7-diphenyl- phenanthroline, are reported. The spectra show that the excited state electron is localised on individual ligands, but show non-statistical contributions from states corresponding to each of the ligands present in the co-ordination sphere. For these complexes the excited state energy is localised on the ligands in the lowest metal-to-ligand charge transfer state, and is funnelled into the energetically favoured ligand after initial excitation. Thus it becomes possible to design systematically complexes with specific ligands which would absorb at the wavelength of choice, but that would funnel the energy onto a different ligand.

Photosensitized Dissociation of Water Using the System Ru(bipy)32+/TiOz R. M. QUINT and N. GETOFF, Int. 3. Hydrogen Energv, 1988, 13, (5), 269-276 The Ru(bipy) , +/H, SO, /n-TiO, system was investigated to discover its water splitting ability. The effects of initial Ru(bipy) , + concentration, preparation grain size and amount of TiO, powder used in suspension were examined. Conditions during system illumination and the pH of the solution were also examined. At prolonged illumination and/or at higher illumination temperatures, <4ooC, a relatively strong decomposition of the sensitiser is seen. Yields of 0, and H, were determined and possible reaction mechanisms are presented.

C. V. KUMAR, 1. K. BARTON, I. R. GOULD, N. J. TURRO

648-651

ELECTRODEPOSITION AND SURFACE COATINGS Structural and Protective Properties of Rhodium Coatings Obtained by Pro- grammed Pulse Current

KOSTIN, Zushch. Metal., 1988, 24, (2), 255-257 Structural and physicochemical properties were studied of Rh coatings deposited by alternating cathodic and anodic impulse currents from an acidic sulphate electrolyte (containing, in gA electrolyte): Rh sulphate ratio of 8-10 (calculated on metal) in go-~oo% H,SO,, pH-I , at 20-25OC using Pt anodes and achieving coatings of thickness of 1-20 pm. The results showed that during cyclic Rh electrodeposition by bipolar-impulse current the microhardness of the Rh coatings increased to goooMPa and at the same time internal tension decreased to 2ooMPa. This method also prevented cracking, decreased porosity and increased the rate of Rh coatings deposition. The reliability and durability of electroapparatus contacts were increased.

V. A. ZABLUDOVSKII, V. I. KAPTANOVSKII and N. A.

Surface Study of Ruthenium Dioxide Coatings Stabilized with Valve-Metal Oxides

and C. BATTAGLIN, Extended Abstracts, Vol. 88-1, Electrochem. Soc., Spring Meeting, Atlanta, Georgia, May 15-20, 1988, 777-778 Depth profiling of RuO,/TiO, coatings containing 30, 40, 50, 60, 70 and 80 at.% Ru was performed to find the extent to which surface segregation is a real physical feature. Coatings were obtained either by pyrolysis of RuCl,.xH,O/TiCI, mixtures or of Ru(NO)(NO,) ,/TiCI,. Various techniques of assess- ment were used.

A. DE BATTISTI, M. CAPPADONIA, G. LODI, R. AMEDELLI

APPARATUS AND TECHNIQUE Nernstian Behaviour of Zirconia Oxygen Sensors Incorporating Composite Elec- trodes s. P. s. BADWAL, F. T. CIACCHI and J. w. HAYLOCK, J.Appl.Electrochem., 1988, 18, (2), 232-239 The Nernstian behaviour of ZrO, 0, sensors incorporating composite electrodes has been examined in the range < h 0 C . These electrodes consist of a semiconducting metal oxide and Pt and lower the operating temperature of 0, sensors to - 3oo-350°C, which is well below that conventional- ly used. Impedance measurements show that the electrode resistance and the time constant go through a minimum when plotted against Pt content in the composite.

Formation of Whiskers on the Electrode Surface by the Electrolysis of 3,3 ’,5,5 ‘-Te tramethylbenzidine A. WATANABE, K. MORI, M. MIKUNI, Y. NAKAMURA and 0. ITO, J. Chem.Soc., Chem.Commun., 1988, (7), 452-453 A fme Pt wire electrode was used in the electrolysis of 3,3’,5,5’-tetramethylbenzidine (TMB), at 60OC; cyclic voltammograms showed two anodic peaks, but no corresponding cathodic peak. By increasing the number of sweeps, needle-like whiskers appeared on the Pt electrode surface, of > I cm in length.

A New Staining Technique of RuO, Solu- tion in Organic Solvents for Resolving the Lamella Structure in Polymers T. CAO, s. CHEN and Y. ]IN, Polymer Commun., 1988,

A solution of RuO, in CCI, was used as a staining medium for resolving the lamella structure in both polyethylene and polypropylene with the transmission electron microscope. Staining in the organic medium was more efficient than in the vapour phase of an aqueous solution of RuO, and was more conve- nient than in the vapour of solid crystalline RuO, for both polymers. The organic solution of RuO, appears to be a universal staining medium for revealing the fine morphology in hydrophobic polymers.

29, (31, 66-67


HETEROGENEOUS CATALYSIS Another Strong Metal-Support Interac- tion: High Intrinsic Methanation Activity of an Alumina-Supported Platinum Catalyst after High Temperature Reduc- tion without Loss of Chemisorption Ability s. TANIGUCHI, T. MOM, Y. MORI, T. HATTORI and Y. MURAKAMI, 3. Chem. SOC., Chem. Commun., 1988,

Pulse surface reaction rate analysis measurements showed that the intrinsic methanation activity of 0.5%Pt/A120, catalyst was increased by high temperature reduction (HTR) without a marked reduction in its chemisorption ability. The rate constant for methanation after HTR was about five times as large as that after reduction at 523K (low temperature reduction, LTR). Heating the catalyst with high methanation activity in flowing 0, followed by LTR caused the rate constant to decrease to near the original value. The rate constant determined by these analyses was not affected by the number of active sites on the catalyst. The changes in methanation activity caused by HTR were reversible but not permanent.

Study of Catalytic Activity in the Reaction of Complete Oxidation of Butane and State of Platinum in PlatinumlAlumina Catalysts Modified by Lanthanum and Cerium

( 10) , 630-63 I

V. A. DROZWV, P. G. TSYRUL’NIKOV, A. N. PESTRYAKOV, A. A. DAWDOV and V. V. POPOVSKII, Kinet. Katal., 1988, 29, (2), 484-488 A study of the effect of the addition of La and CX oxides to 2.53Wt.0/oPt/~~01 catalysts at 523-623K on the catalytic activity during complete oxidation of butane showed that this addition greatly increased the dispersion and stability of the deposited Pt during superheating. The electronic state of Pt surface atoms and of studied samples after various treatments was established spectroscopically. The results showed that adding Ce oxide to Pt depresses reduction in favour of oxidation, compared to unmodified Pt.

Mass-Spectroscopy Study of Products of Thermodesorption with 0.3%Pt/y-Al2 0, Catalyst A. A. IVKO and s. v. WKEVICH, Vesm. Akad. Navuk BSSR, Ser. Khim. Navuk, 1988, (I) , 18-21 Mass-spectroscopy studies were performed of the gassing and thermodesorbed products formed during benzene hydrogenation to cyclohexane over o.3%Pt17-Al,01 catalyst, which is the primary reaction stage of the industrial production of caprolac- tams. A temperature dependence of the yields was also studied. Cyclohexane dehydrogenation to benzene occurred at low temperatures. The results showed that coal formation goes on in spent catalysts if they are heat treated in vacuum.

On the Influence of Sulphur on the Activi- ty and Selectivity of Reforming Catalysts in the Conversion of Methylcyclopentane M. WILDE, T. STOLZ, R. FELDHAUS and K. ANDERS, Chem. Tech.(Leipzig), 1988, 40, (4), 166-169 The conversion of methylcyclopentane at atmospheric pressure was investigated for Pt/Al ,O ] , Pt-Re/Al,O, and Pt-Re-Cr/Al,O, as a function of their pretreatments. Presulphidation caused very high conversions, high yields of cyclenes, aromatics and H , , and hence enhanced coke formation. With self-poisoning, S stabilises the hydrogenation/ dehydrogenation reactions of the catalysts. Reactiva- tion with CCI, in air increases the total conversions; and the cracking activity increases. For best results, the reaction should be performed after presulphidation when the catalysts contain high C1 contents.

Skeletal Catalysts on Supports. 11. For- mation and Structure of Pt-Cu/A12 0 Raney Catalysts

FASMAN, Kinet.Katal., 1988, 29, (I), 180-184 The porous structure of Pt-Cu/Al,O, Raney catalysts was studied by a low-temperature adsorption method and by capillary condensation of Ar. The treatment of the catalyst with 5% HNO, increased specific surface and porosity at the expense of dissolving part of the 7-Al ,O and Cu. The rest of the Cu was redispersed in the pores of the catalyst, stabilising and forming 0- CuAlO, . During the catalyst preparation highly dispersed surfaces were formed. It is suggested that Cu ions fixed in the lattice of 7-Al 0 become centres of stability for migrating Pt atoms.

The Adsorption of Oxygen and the Oxida- tion of Methanol on Silver-Platinum Alloys S. DONG, F. XIAO and J . DENG, J.Catal., 1988, 109, ( I ) , 170-179 The effects on the adsorption and oxidation of methanol on Ag of alloying Pt with Ag were examined spectroscopically. Ag-Pt alloys containing (9.7 at.% Pt were prepared. Two kinds of adsorption states of 0 were found on the surface of the alloys by XPS and TDS techniques. The catalytic activity and selectivity for oxidising methanol were measured.

Selective Hydrogenation of CO into C , and C, Alcohols by Si0,-Supported RhFe, PtFe, and PdFe Bimetallic Cluster- Derived Catalysts

3. Chem.Soc., Chem.Commun., 1988, (6), 428-430 Evidence for the potential benefits of SO,-supported Rh,Fe, Rh,Fe,, F’tlFel, PtFe,, Pd,Fe, and PdFe, carbonyl clusters as precursors for the preparation of tailored bimetallic catalysts is presented. The derived catalysts exhibit high catalytic activities and selec- tivities for the formation of oxygenates, consisting mainly of methanol and ethanol from CO + H, .

G. M. KHUTORETSKAYA, V. N. ERMOLAEV and A. B.

A. FUKUOKA, T. KIMURA and M. ICHIKAWA,

154 Plarinum Metals Rev., 1988, 32, (3)

The Effect of the Carrier Modification by y-Alumina on Palladium Catalyst Pro- perties v. M. VLASENKO, v. A. KUZNETSOV, I. A. MAL’CHEVSKII, L. V. PALAMARCHUK and G. V. FILONENKo, Dokl. Akad. Nauk USSR, Ser. B, 1988, (3), 40-43 Studies were made of the effect of modification of o.q%Pd/a-Al, 0 catalyst by y- Al 0, on its properties. The results showed the existence of an optimal concentration of y-Al,OJ at which the maximum dispersity of Pd particles and the highest value of its specific catalytic activity were observed.

Syntheses and Characterization of Mercapto-Hydroxyl-Palladium Macro- molecular Chelates and Their Catalytic Properties Y. WANG and H. LIU, 3. Mol. Catal., 1988, 45, (I),

A Pd complex with an unusual macromolecular mercapto-hydroxyl bidentate ligand was prepared by the reaction of epoxy-phenolic oligomer with H,S and was then characterised spectroscopically. The catalytic behaviour of macromolecular Pd chelate complexes absorbed on a S O , support was studied

127-142

by the Heck reaction. The activity of the chelates The Conversion of Pobaccharides to depended on the molar ratio of S:Pd, and an active Hydrogen Gas. Part 1: The Palladium catalyst was obtained at a S:Pd ratio of 2. The catalyst Catalysed Decomposition of Formic was inactive at ratios of 6 or greater. The catalyst had AcidISodium Formate Solutions better stability than other polymeric Pd catalysts. s. P. HILL and 1. M. WINTERBOTTOM, J . Chem. Tech. Biotechnol., 1988, 41, (2), 121-133 Studies of catalytic decomposition of solutions containing formic acid and Na formate to H , + CO , over 5% w/w Pd/charcoal catalyst was studied in a stirred reactor at 60-go°C. The production of H, gas was optimum in the pH range 3.8-6.5 and the order of reaction varied with the solution composition from 0.33(1oomol% formic acid) to 1.07(1oomol% formate ion). Energies of activation were in the range 20.9&5 to 41.8qkJ/mol, the larger values occurring at the ends of the composition range.

Study of Dealkylation of meta-Cresol on Alumina-Supported Rhodium, Nickel and Palladium Catalysts M. ASSAFI and D. DUPREZ, Bull. Soc. Chim. Fr., 1988, (I), 106-112 The meta-cresol steam dealkylation on Al , 0 - supported Rh (0.6wt.%), Pd(0.6wt.%) and Ni(r1.4wt.%) catalysts was performed in a dynamic reactor at 4o0C, at atmospheric pressure and weight hourly space velocity of 2 to 20h. The results were compared to the performance of the same catalysts in toluene steam reforming. The formation of acid-like reaction products was observed in significant propor- tions, even on the bare support. This was explained as being due to the ability of the cresol molecule to be protonated on the aromatic ring. The relative activity order was: Rhroo>Pd25>Ni13.

Catalytic Activity of Supported Liquid- Phase Lithium-Palladium Acetate Catalysts in the Oxidation of Ethylene to Vinyl Acetate s. A. H. ZAIDI, Appl. catal., 1988, 38, (2), 353-358 The effect of different liquid loadings in catalysts containing solutions of Li-Pd acetates on C was studied in the selective oxidation of ethylene to vinyl acetate at 428-463K. The oxidation reaction appeared to take place in an acetic acid fdm on the periphery of the C particles and the site of activity of these supported solutions seems to lie in between the micro- and macropores of the C support.

Iron or Lanthanum Promoters on the Selectivity of Palladium Zeolites in Methanol Synthesis B. M. CHOUDARY, K. LAZAR, K. MATUSEK, and L. GuczI, J. Chem. Soc., Chem. Commun., 1988, (9), 592-594 The first example showing a distinct shift in selectivity towards methanol formation during CO hydrogenation on addition of Fe or La to Pd zeolite catalysts, and giving enhanced activity is reported.

Catalytic Oxidation of CO on RhlSiO? : A Rapid-Response Fourier Transform In- frared Transient Study Y. -E. LI and R. D. GONZALEZ, 3. Phys. chem., 1988,

The catalytic oxidation of CO was studied over Rh/SiO, by using a FTIR-mass spectrometric technique. The reactivity of linearly adsorbed CO was considerably greater than that of the dicarbonyl species at both 85 and 2ooOC. The oxidation of CO over Rh/SiO, proceeded through a mixed 0-CO adlayer. Induction times required for the formation of gas- phase CO, were nearly 2 orders of magnitude lower than those observed for Pt/SiO, and Pd/SiO,. Self- sustained CO-0, oscillations reinforced the greater reactivity of linearly adsorbed CO. H,-CO-0, transient studies also suggest the formation of mixed H- CO adlayers.

Selective Formation of Lower Alkenes and Alcohols in CO + H2 Reaction Catalysed on NaY Zeolite-Encapsulated Rh, and RhFe Bimetallic Cluster-Derived Catalysts L. -F. RAO, A. NKUOKA and M. ICHIKAWA, 3. Chem. SOC., Chem. Commun., 1988, (7), 458-460 Rh,, Fe, and bimetallic RhFe clusters encapsulated in NaY zeolite were characterised and examined in the CO + H, reaction under atmospheric pressure. The Rh, clusters led to the formation of C,-C, alkenes, whereas the entrapped RhFe clusters had a higher selectivity for C, -C, alcohol formation.

92, (61, 1589-1595


Design of Fischer-Tropsch Catalysts by Pulse Surface Reaction Rate Analysis. 11. Selective Production of Liquid Fuel Frac- tion on RutheniumIAlumina Catalyst Pro- moted by Rare Earth Oxides N. TAKAHASHI, T. MORI, A. MIYAMOTO, T. HATTORI and Y. MURAKAMI, Appl. coral., 1988, 38, ( I ) , 61-69 Different rare earth oxides were tried as promoters of Ru/AI,O Fischer-Tropsch catalysts for the selective production of liquid fuels via the hydrogenation of CO. Rare earth oxide additions resulted in an increase in the turnover frequency, and an increase in the selectivity for the production of higher hydrocarbons.

Direct Synthesis of Alcohols from Syngas on Ru-Mo-Na2 O/Al, 0 Catalysts: Synergistic Effect of Ru and Mo

Y. TAKEGAMI and T. INUI, 3. Mol. catal., 1988, 45, ( I ) , 1 1 1 - 1 2 6

Direct synthesis of alcohols from syngas on Ru-Mo- Na,O/AI,O, catalysts was studied at 25s°C under 86kg/cm1 pressure. The results showed that close contact between Ru and Mo particles was essential for the formation of alcohols. Combining Na,O with the Ru-Mo catalyst decreased the catalytic activity but increased the selectivity for alcohols, together with a slight increase in propagation probability for alcohol products.

Wet Oxidation Catalyzed by Ruthenium Supported on Cerium(1V) Oxides

Chem. Res., 1988, 27, (4), 7 1 8 - 7 2 1

The activity of various noble metal catalysts was investigated for the wet oxidation of organic compounds, in order that a more effective way of treating highly contaminated waste waters could be found. Ru was the most effective catalyst tried, and Ce(1V) oxide the most effective support. The Ru/Ce catalyst rivall- ed homogeneous Cu catalyst which is used for waste water treatment, for the oxidation of n-propyl alcohol, n-butyl alcohol, phenol, acetamide, etc. It was especially effective for the oxidation of some high 0-containing compounds, such as poly(ethy1ene glycol), ethylene glycol, etc.

Hydrogenation and Acetalization of Cyclohexanone over Platinum Group Metal Catalysts in the Presence of Ethylene Glycol

AIZUMI, Nippon Kagaku Kuishi, 1988, ( I ) , 126-128 The hydrogenation of cyclohexanone was performed under atmospheric or high H, pressure (Iookg/cm,) at 7ooC over platinum group metal catalysts in the presence of ethylene glycol. Although only hydrogenated product (cyclohexanol) was detected over Os, Ir, and Pt catalysts, the rapid formation of acetal was observed over Ru, Rh and especially Pd catalysts under H conditions.

M. INOUE, T. MIYAKE, S. YONEZAWA, D. MEDHANAWN,

S. IMAMURA, I . FUKUDA and S. ISHIDA, Ind. Eng.

J.-I. ISHIYAMA, K. ESASHIKA, Y. SENDA and S. IM-

HOMOGENEOUS CATALYSIS Homogeneous Catalysis of the Water-Gas Shift Reaction R. M. LAINE and E. 1. CRAWFORD, J . Mol. Catal., 1 9 8 8 , 44, (3L 357-387 A review is given of the advances in homogeneous catalysis of the water-gas shift reaction (WGSR) in the presence of platinum group metals published during the last 10 years. Topics discussed include transition metal catalysis of the WGSR under both acidic and basic conditions, as well as areas of special interest such as mixed-metal catalysis and catalyst tolerance toward S contaminants. ( 9 6 Refs.)

Reversible Homogeneous Catalysis of Carbon Dioxide Hydrogenation/Reduc- tion at Room Temperature and Low Pressures

Chem. Commun., 1988, (9) , 602-603 The Pt complex, IPt,(p-dppm),l, where dppm = Ph,PCH,PPh,, is an effective catalyst under un- precedented mild conditions in toluene solution for the reaction between CO,, H , and Me,NH to yield dimethyl formamide and H, 0. The catalysis is readily reversible, which is unusual.

Allylation of Active Methylene Com- pounds with Ally1 Oxime Carbonates Catalyzed by Pd(0) 0. SUZUKI, Y. HASHIGUCHI, s. INOUE and K . SATO, Chem. Lett. Jpn., 1988, (2), 291-294 Allylation of active methylene compounds catalysed by a Pd(o)-phosphine system using Pd(dba) (dba = dibenzylideneacetone) catalyst and diphenylphosphinoethane was performed with high stereoselectivity by employing ally1 oxime carbonates as the allylating reagent. Higher stereoselectivity was obtained by using triphenylphosphine as an additive ligand, but regioselectivity was lowered.

Highly Efficient Total Synthesis of Manoalide and Seco-Manoalide via Pd(0) Catalyzed Coupling of Allylhalide with CO and 2-SilyI-4-Stannylfuran S. KATSUMURA, S. FUJIWARA and S. ISOE, Tetrahedron Lett., 1988, 29, (IO), 1 1 7 3 - 1 1 7 6

Improved and highly efficient total synthesis of manoalide and seco-manoalide from an allylchloride derivative was achieved by 6 steps in 56.4% overall yield by Pd(o) catalysed coupling with CO and 2-trimethylsilyl-4-tributylstannylfuran followed by chemoselective oxidation of 2-trimethylsilylfuran with singlet 0. This synthesis of these unique sesterterpenoids promises not only to supply enough quantities of these biologically important pen- taprenoids but also to make possible the synthesis of various analogs of manoalide. The seco-manoalide inhibits both phospholipase A2 and aldose reductase more strongly than manoalide in vitro.

S. SCHREINER, J. Y. YU and L. VASKA, 3. Chem. SOC.,


Substitute Carbonylation of Organic Compounds Catalysed by Palladium Complexes YU. v. GULEVICH, N. A. BUMACHIN and I. P. BELET- SKAYA, Usp. Khim., 1988, 57, (4), 529-561 A review is given of substitute carbonylation of element-organic compounds, organic halides and other substrates of the type RX, in which X converted to CO during reaction catalysed by Pd complexes. The mechanism of the reaction behaviour of Pd complexes during carbonylation was discussed. The use of the substitute carbonylation reaction in organic synthesis was emphasised. (141 Refs.)

Study of Kinetics and Mechanism of Oxidative Acetoxylation of Propylene Catalysed by Pd(I1) v. I. EMEL’YANOV, s. D. ASRIEV, A. s. SOBOLOV, B. v. FAL’KOVSKII, B. YA. STUL’, A. v. BORISOV and B. B. CHESHOKOV, Kinet. Katal., 1988, 29, ( I ) , 103-109 A kinetic study of oxidative acetoxylation of propylene, by O 2 in acetic acid in the presence of PdCI, catalyst and nitrate ions at 50-85OC and various NO,-:Pd(II) and propylene:O, ratios, showed the formation of monoacetate propylene glycols. The reaction of propylene and Pd(I1) was found to be first order. The obtained kinetic data agree with a mechanical reaction forming intermediate Pd nitrite complexes with propylene.

Palladium(0)-Catalyzed Isomerization o,P-Epoxy Ketones to @-Diketones M. SUZUKI, A. WATANABE and R. NOYORI, Red. Trav. Chim. Pays-Bas, 1988, 107, (3), 230-236 Studies of the isomerisation of cY,&epoxy ketones in the presence of catalytic amounts of tetrakis(triphenylphosphine)Pd(o) and 1,2,- bis(dipheny1phosphino)ethane showed the formation of the corresponding &diketones in high yields. Both open-chain and cyclic substrates could be used. Possi- ble reaction mechanisms were discussed.

Highly Catalytic Dehydrogenation of Alkanes to Olefins via C-H Activation in the Presence of RhCl(CO)(PMe,), under Irradiation

TANAKA, Chem. Lett. ypn., 1988, (2), 263-264 Olefins and H , were catalytically formed from alkanes in the presence of RhCI(CO)(PMe,), under irradiation by a IOOW high pressure Hg lamp at am- bient temperature for 16.5h. The irradiation was performed under N, atmosphere in a closed system. The results showed the,formation of cyclohexene (138 turnovers) and benzene (3 turnovers). A nearly theoretical amount of H, (132 turnovers) was detected in the gas phase. The article gives the first example of a practical productive dehydrogenation of alkanes via the transition metal complex catalysed C-H activation. The system does not require a H ac- ceptor and shows high catalytic activity.

T. SAKAKURA, T. SODEYAMA, Y. TOKUNACA and M.

Remarkable Effect of the Wavelength in the Photoassisted Carbonylation of the C- H Bond of Decane in the Presence of RhCI(CO)(PR,), as the Catalyst

M. TANAKA, Chem. Lett. Jpn.,1988, (I), 155-158 Studies of the carbonylation of the C-H bond of decane performed in the presence of RhCI(CO)(PR,), catalyst under irradiation by a 500w high pressure Hg lamp showed the formation of C,, aldehydes andlor I-nonene, depending on the wavelength. Irradiation with X>29gnm was essential to the formation of I-nonene and undecanal. By cut- ting off X<325nm, I-nonene formation was completely suppressed and a series of isomeric C,, aldehydes was obtained.

High Deoxygenation Ability of Rh Car- bony1 Clusters toward Oximes Leading to Nitrile Formation

Jpn., 1988, (2), 285-286 Nitriles were selectively prepared by the reaction of aldoximes with CO and H ? O in the presence of Rh,(CO) ,b cluster catalysts. The i.r. spectra studies of the condensed reaction mixture showed the formation of Rh,, and Rh,, carbonyl cluster anions.

Iridium-Catalysed Hydrosilylation of Hex-1-yne: The Unusual Formation of 1 -Triethylsilylhex- 1 -yne M. J . FERNANDEZ, L. A. ORO and B. R. MANZANO, 3. Mol. Catal, 1988, 45, (I), 7-15 Hex-I-yne reacted with triethylsilane in the presence of IrH, (SiEt,)(COD)(AsPh ,) or Ir catalysts formed by adding triarylarsines (L) or triarylphosphines (L) to [Ir(OMe)(diolefin)ll. The catalytic products were the expected trans- and cis-1-triethylsilylhex-1 -enes, as well as significant amounts of I-triethylsilylhex-I-yne and hex-I-ene. The formation of alkynyltriethylsilanes from alkynes, and alkenyltriethylsilanes from alkenes is a characteristic of the [Ir(OMe)(diolefin)l, + nL systems. Mechanistic pathways for the observed hydrosilylation reaction were discussed.

Selective Hydrogenation of PhCH = CHCOMe to the Unsaturated Alcohol Catalysed by [IrH,(PR,),] (R = Alkyl or

E. FARNETTI, J . KASPAR, R. SPOGLIARICH and M. GRA- ZIANI, 3. Chem. SOC., Dalton Trans., 1988, (4), 947-952 The selective hydrogenation of (PhCH = CHCOMe) catalysed by Ir-phosphine systems prepared in situ is reported. Different species are formed depending on the P I r ratio and on the steric properties of the phosphine. [IrH,(PR,)?l (R = alkyl or aryl) is a catalyst for the hydrogenation of the C = C bond, whereas [IrH,(PR,),l catalyses the reduction of the carbonyl group with a selectivity up to IOO%.

T. SAKAKURA, K. SASAKI, Y. TOKUNAGA, K. WADA and

K. KANEDA, K. DOKEN and T. IMANAKA, Chem. Letf.

Aryl)


Asymmetric Dihydroxylation via Ligand- Accelerated Catalysis

SCHRISDER and K. B. SHARPLESS, 3. Am. Chem. soc., 1988, 1x0, (6), 1968-1970 A new catalytic asymmetric dihydroxylation between olefins and OsO, which gives substantially improved rates of reaction and turnover numbers and useful levels of asymmetric induction, is reported. When the process is performed in the presence of alkaloid an OsO,-alkaloid complex is formed, which is far more reactive than OsO, alone. The alkaloid acts as an ac- celerator of the dihydroxylation catalysis by binding strongly enough to accelerate addition to olefins.

Ruthenium Carbonyl Catalysed Reduc- tive Carbonylation of Aromatic Nitro Compounds. A Selective Route to Car- bamates

Org. Chem., 1988, 53, (6) , 1243--1250 Ru,(CO),, and Ru(CO),(PPh,), catalysed the reductive carbonylation of nitrobenzene and substituted aromatic mononitro compounds to give the corresponding methylcarbamates, in toluene- methanol, at 160-17ooC and batm, with high selectivity in the presence of NEt,+Cl- as co-catalyst. This catalytic system works in relatively mild conditions, and it is one of the most selective reported. The effects of CO pressure, reaction temperature, and amount and nature of the added alcohol and co- catalyst were studied.

Homogeneous Catalytic Hydrogenation of the Esters of Bicarboxylic Acids. Part 111. Ethylene Glycol from Dimethyl Oxalate

TI, 3. Mol. Catal., 1988, 44, (3h 347-355

E. N. JACOBSEN, I . MARK^, W. S. MUNGALL, C.

S. CENINI, C. CROTTI, M. PIZZOTTI and F. PORTA, 7.

U. MATTEOLI, G. MENCHI, M. BIANCHI and F. PIACEN-

Dimethyl oxalate was hydrogenated in the presence of Ru(C0) , (CHI COO) , (PBu,) to methyl glycolate, which was subsequently reduced at a much slower rate to ethylene glycol. This reduction was affected by high H, pressure and pretreatment of the catalytic system with a hydroxylated reactant, such as methyl glycolate or ethylene glycol itself. Under optimum conditions a 95% conversion of dimethyl oxalate to the corresponding glycol was achieved.

The Photochemical Carbonylation of Benzene, and Hydrogenation and Hydrosilation of Benzaldehyde Catalyzed by Ruthenium(0) Complexes E. M. GORDON and R. EISENBERG, 3. MOl. catal . , 1988, 45, (I) , 57-71 The activation and functionalisation of an arene C-H bond was achieved in the photochemical carbonylation of benzene catalysed by the Ru(o) complexes RuU(CO)(NO)(PP~,),(I), Ru(C0) ,(PPh,) , (2 ) and Ru(CO),(PPh,)(3). Under the carbonylation conditions, both (I) and (2) converted to Ru(CO),(PPh,).

Oxygen Evolution by Means of Water Ox- idation Catalyzed by Mononuclear Ruthenium-Ammine Complexes M. KANEKO, R . RAMARAJ and A. KIRA, Bull. Chem. SOC. 3Pn., 1988, 61, (4, 417-421 Oxidation of H,O was achieved catalytically by the use of mononuclear Ru-ammine complexes [Ru(NH,),C1I2+ and [Ru(NH,),(H,O)l’+, with Ce(IV) as an oxidant. Cyclic voltammetric studies of the mononuclear Ru-ammine complexes were performed using Basal Plane Pyrolytic Graphite (BE) coated with poly(p-styrenesulphonate), Nafion or kaolin clay. The electrochemical properties of these Ru-ammine complexes show that they can be used as two-electron oxidants for H,O oxidation. The H,O oxidation depended on the ionic strength of the media; higher acidic conditions gave higher 0, yields. However, heterogeneous catalysis with the Ru complex in kaolin was as effective as homogeneous.

FUEL CELLS Platinum Supported on Silicon Carbide as Fuel Cell Electrocatalyst

Electrochem. SOC., 1988, 135, (4), 917-918 Sic was evaluated as the support in phosphoric acid fuel cells to see if it prevents Pt particle agglomera- tion. C black was incorporated into the catalyst layer to achieve electrical conduction. Electrodes were fabricated, 0, was reduced, Pt particle dispersion was examined by TEM and Pt particle diameter was measured by X-ray diffraction. Results indicate that Pt/SiC could be a potential support for phosphoric acid fuel cells, but that the method of preparation and electrode fabrication need to be optimised.

Methods to Attain High Power Densities in Solid Polymer Electrolyte Fuel Cells Using Low Platinum Loading Electrodes

SRINIVASAN, Extended Abstracts, Vol. 88-1, Elec- trochem. Soc., Spring Meeting, Atlanta, Georgia, May 15-20, 1988, 2-3 Methods of attaining high power densities in SPE fuel cells are discussed. The optimisation of the Nafion film impregnated into the electrode and the optimal hot pressing conditions between Nafion and electrode are considered. For stable long term performance, 0, or air should be humidified at IO-ISOC, and H, at IO-IS~C, above the cell temperature. Localisation of Pt near the front surface of the electrode, which is most effective for high power densities, is achieved by two methods, giving total Pt loadings <0.5 mg/cmz. Sputtering Pt onto a standard electrode enhanced the power density by IOO-I~OYO; and cells with 20-40 wt.% R/C electrodes had a better performance than those with 10 wt.% Pt/C. However, sputtering a Pt film onto 20 wt.% Pt/C gave the highest power densities. A stable performance of x m h occurred at 300 and 500 mA/cm’.

A. HONJI, T. MORI, Y. HISHINUMA and K. KURITA, 7.

E. A. TICIANELLI, C. R. DEROUIN, W.-K. PAIK and S.


Change of Pt Distribution in the Active Components of Phosphoric Acid Fuel Cell 1. ARAGANE, T. MURAHASHI and T. ODAKA, J. Elec- trochem. SOC., 1988, 135, (4), 844-850 The changes in Pt distributions in the active components, in phosphoric acid fuel cells were investigated after long term use. Electron probe microanalysis shows Pt loss in the cathode and also Pt migration to the anode during operation and iden- tifies Pt in the matrix.

CORROSION PROTECTION Passivating Ability and Corrosion Stabili- ty of Stainless Steel Surface-Alloyed by Palladium by Vacuum Condensation Method

TOMASHOV, Zashch. Met., 1988, 24, (2), 199-203 Studies of the electrochemical and corrosion behaviours of stainless steel after surface alloying with Pd applied by a vacuum condensation method and then followed by diffusion annealing of the sample, were performed in 10 and 20%H2S0, at 25-100°C. The results showed an increase in corrosion stability by several orders of magnitude in the stainless steel after surface modification by Pd.

G. P. CHERNOVA, T. A. FEDOSEEVA and N. D.

CHEMICAL TECHNOLOGY The Preparation of Chloroplatinic Acid Labelled with Platinum Radioisotopes A. B. MALININ, N. v. KURENKOV, M. D. KOZLOVA and A, s. SEVASTYANOVA, 3, Radwanal. Nucl. Chem.,

After the extraction of ‘“Au impurities, natural metallic Pt, which has been irradiated in a nuclear reactor, may be used for the preparation of labelled hexachloroplatinic acid, which is then utilised for the synthesis of various anti-tumour compounds.

“Tailored” Organometallics as Precur- sors for the Chemical Vapor Deposition of High-Purity Palladium and Platinum Thin Films

GIROLAMI, J. Am. Chem. SOC., 1988, 1x0, (8), 2688-2689 The synthesis of high-quality Pd and Pt thin films by metal-organic chemical vapour deposition (MOCVD), from ‘‘tailored’’ organometallic precursors under mild conditions, for use in electronic devices, is reported. Three organo-Pd compounds were studied as potential precursors for Pd thin films. CVD was conducted at 250OC and Io-‘torr, and bright silvery metallic films up to 21m thick were grown on a variety of substrates. Electrical conductivity measurements were performed.

Lett . , 1988, 126, (I), 17-25

J. E. GOZUM, D. M. F’OLLINA, 1. A. JENSEN and G. S.

ELECTRICAL AND ELECTRONIC ENGINEERING Contact Voltage Drop and Wear of Self- Lubricating Ag-Pd Alloy Base Composite Materials K. OKADA and M. YOSHIDA, IEEE Trans. Components, Hybrids, Manuf. Technol., 1988, XI, (I), 116-123 New wrought self-lubricating Ag-Pd alloy base composite materials containing graphite are described and the contact voltage drop, wear and friction of the new self-lubricating brushes and the metal alloy slip rings were studied. The results showed that since a thin graphite film of about 10ohi existed on the contact boundary surface for the Io%Pd-5%C-Ag brush and the Cu-Io0hAg slip ring, both the friction coefficient and the specific wear rate became small.

Low Dielectric Constant Multilayer Glass- Ceramic Substrate with Ag-Pd Wiring for VLSI Package

IEEE Trans. Components, Hybnds., Manuf. Technol., 1988, XI, (I), 163-170 New glass-ceramic materials, with low dielectric constant, which could be sintered at about w 0 C in air, have been developed by means of green sheet technologies using Ag-Pd wiring.

Phase Transitions in Ru Based Thick- Film (Cermet) Resistors B. MORTEN, M. PRUDENZIATI, M. SACCHI and F. SIROT- TI, 3. Appl. Phys., 1988, 63, (7), 2267-2271 Thick-film resistive inks were prepared starting from powders obtained by precipitation of RucI, on two different lead-containing glasses. The structural and electrical properties of the films were studied after heat treatment at various temperatures. The evolution of the microstructure involved phase transformations from Pb-rich (Ru-deficient) pyrochlores to RU pyrochlores and f d l y to RuO, .

Y. SHIMADA, Y. YAMASHITA and H. TAKAMIZAWA,

TEMPERATURE MEASUREMENT Forehearth Temperature Gradient Measurements with Thermocouples D. A. TOENSHOFF and C. J. STEER, Glass, 1988,65, (4), 135-1369 I39 The effective use of thermocouples in the glass con- tainer industry is briefly reviewed. The problem of the short life of thermocouples immersed in amber glass has been investigated, and a solution found. In- tergranular fracture of Pt-~oYoRh thermocouple sheaths was associated with Rh-S formation at the grain boundaries. This compound dissolves readily in the glass, producing voids which connect together and cause grains to fall off. The use of a R-Au alloy or Pt strengthened by the dispersion of an oxide avoids premature failures from Rh.


NEW PA TENTS METALS AND ALLOYS Contact Material DEGUSSA A.G. European Appl. 250,958A A matrix material containing Ir, Os, Ru and/or Rh and Zn particles has low contact resistance, good corrosion resistance and excellent wear-resistance. It can be recrystallised at 70o0C, allowing it to be futed to a Cu substrate. It is used for low current applications.

Precious Metal Powder Production GTE PRODUCTS CORP. U. S. Patent 4,71 I ,660 Production of spherical precious metal powders less than 20 pm in diameter is effected by high temperature plasma treatment of mechanically reduced particles. Fine spherical powders of for example Pt, Pd, Ru, Os, Au, Ag, and their alloys are useful in electronics, electrical contacts and parts, brazing alloys, and dental alloy applications.

Composite for Absorbing Electronic Waves

A composite for absorbing electronic waves has a substrate with a metallised layer containing metals and/or rare earth elements, and one or more of Pt, Pd, Ru, Rh, Au, Ag, Fe, Cr, W, etc. Metal alloy parts are brazed to the surface using a brazing fdler containing Pd, Au, Ag, Cu, Ni or Co. The composite has high thermal conductivity, and is used in magnetrons, klystrons and travelling-wave tubes.

NIPPON HYBRID TEC. Japanese Appl. 621232,198

CHEMICAL COMPOUNDS Combustion Resistant Compositions UNION CARBIDE CORP. U.S. Patent 4,701,488 Heat-curable amino organo-polysiloxanes contain as combustion inhibitors: Ir, Rh, Cr or Mo compounds or mixtures containing Pt compounds and preferably Ce compounds. The material can be used in thermal and electrical insulators, gaskets, etc. Coated materials can be used as roofs of sports arenas. The material is stable indefinitely in air.

ELECTROCHEMISTRY Bipolar Electrolytic Cell with Platinum Anodes

Immobilised Enzyme Electrode CAMBRIDGE LIFE SCI. European Appl. 247,850A An enzyme electrode consists of an enzyme immobilised or adsorbed on resin-bonded carbon or graphite particles with platinum group metal particles dispersed throughout the substrate layer. The electrode shows fast response to glucose.

Metal Deposition Using Platinum Electrode TOSHIBA K.K. U.S. Patent 4,696,721 Electron deposition of a metal onto a conductive matrix of Ag coated glass uses an insoluble electrode, preferably of Pt, to set up the voltage potential. Deposition occurs from a sulphamate solution, generating azodisulphonate, which is decomposed by exposure to U.V. irradiation. The process is used in electroforming of Ni stampers.

Corrosion Resistant Oxygen Anodes STANDARD OIL CO. (OHIO) U.S. Patent 4,696,731 Composite 0 anodes with high corrosion resistance consist of a substrate with an amorphous alloy layer of Pt and P, As, Si, B, Ge, Al or Sb; fused to which is a mixed metal oxide layer containing Ir and Ru. The 0 anodes are used in electroplating, electrowin- ning, etching, fuel cells, and organic reactions such as pinacol formation.

Insoluble Electrode for Electrolytic Refining NIPPON STEEL CORP. Japanese Appl. 62/21 8,592 An insoluble electrode has a surface treated by irradiation of ions mixed with corrosion resistant electroconductive material, and coated with a platinum group metal or alloy. Such electrodes can be used in the production of soda, electrolytic refining, plating, electrolysis of sea water, etc.

Durable Electrode for Electrolytic Cells OSAKA SODA K.K. Japanese Appls. 621240,780 and

A valve metal substrate has a first coating layer of 20-80 mol.% Pt and 20-80 mol.% Ir oxide, and a second coating of 3-15 mol.% Ir oxide, 5-25 mol.% Ru oxide, and 60-92 mol.% Sn oxide or TI oxide. It is used as an electrode in electrolytic cells for Cl] andlor alkali production, or sea water electrolysa- tion, and shows good durability.

62f243,79O

PLENTY LTD. British Appl. 2,191,508A A bipolar electrolytic cell has a sealed stack of bipolar electrodes with a thin layer of Pt as the anode, and a

Anode for E1ectroosmosis Dehydrator FUJI ELECTRIC MFG. K.K. Japanese APPl. 621254,817

thin disc of Ti as the cathode. The cell is flexible and reliable, with electrolyte cross-flow through alternating ports to inhibit scale formation. It is used particularly for the electrolysis of brine or seawater to produce Na hypochlorite.

An anode is prepared by applying a surface coating layer containing platinum group metals or their oxides, preferably Ir oxide, to a metal plate of Ti or Ta bent into the required shape. The anode is used in an electroosmosis dehydrator to dehydrate sludge.


Metallised Membrane System BAYER A.G. German Appl. 3,615,831 A membrane system has a thin permeable metal layer obtained by electroless wet chemical metallisation of organic polymer membranes after activation with organometallic complex compounds of Pt, Pd, Ag and/or Au. It can be used as cathodes for separating cations or as anodes for separating anions; for the separation of gases or liquids using a heated membrane, for separating biogases, gases, liquids, ions, colloids, for clinical diagnostics and for producing very pure H , 0.

Platinum Electrode for Generation of Oxide Ions PERM. POLY. Russian Patent 1,291,863 Oxide ions are generated by electrochemical reduction of cleaned gaseous 0, passed over a Pt electrode in a quartz tube. The oxide ions arc used for coulometric titrations, and determination of metals in melts, such as MgCI, in a eutectic of K, Na and Li chlorides. The process has improved effectiveness, giving a yield on current of IOO-CI%.

PHOTOCONVERSION Chloride Catalysts for Dehydrogenation and Hydrogenation AGENCY OF IND. XI. TECH. Japanese Appl. 62/215,544 Saturated hydrocarbons are readily prepared by hydrogenation of C-C unsaturated bonds using 2-propanol as the H source. Dehydrogenation of 2-propanol is effected by light irradiation in the presence of Group VIII metal chloride catalyst, especially Ru, 0s or Ir. Chlorides of Rh, Ru, 0s or Pt are used for dehydrogenation-hydrogenation.

Polymer Catalyst Containing Platinum AGENCY OF IND. SCI. TECH. Japanese Appl. 621269,752 A polymer catalyst for the production of reductants and oxidants includes a polymer consisting of Pt, Ni, Zr, 0, and alkoxyl groups. A mixture of the catalyst and an electron-donating substance is radiated with visible light, and photoexcited electrons are conducted to the active metal parts such as Pt or Ni, where H, is produced from H+ ions in the water.

ELECTBODEPOSITION AND SURFACE COATINGS Thin Metal Film Production

An organometallic compound of Rh, Pd, Ru or Co is evaporated at 0. I tom or lower and at 3woC or lower temperature; and this vapour is acted upon by heat, plasma and light. The vapour is condensed onto a base. The method is used for forming a Group VIII metal thin f h for electronic parts. High deposition rates can be obtained and easily controlled.

NIPPON ENGELHARD K.K. JapaneSe Appl. 62/207,868

Metallised Inorganic Particles with Palladium Layer AGENCY OF IND. SCI. TECH. Japanese Appl. 62/207,875 A surface Pd colloid adsorption layer is applied to inorganic particles by agitating a mixture of the particles with a Pd hydrosol containing surfactant(s). After separation, a surface electroless plating layer is applied which has excellent adhesion strength. The metallised inorganic particles are used as an elec- tromagnetic wave shield, electroconductive ink, etc.

Anodes with a Platinum Group Metal Film H. KONISHI Japanese Appl. 62 /218 ,591

A platinum group metal fdm is formed on the surface of a metal electrode substrate by coating it with a slurry substance containing the platinum group metal compound, and then heating it by far i.r. Generation of pin holes on fdm formation and peeling of the coatings during use can be prevented using this method. The electrodes are used as anodes for NaCl electrolysis.

Electroless Metal Plating of Polyamide Fibres or Plastic HITACHI CHEMICAL K.K.

Japanese Appls. 62/230,984/85 Surface-roughened plastic or polyamide fibres are immersed in a catalyst liquid of Pd chloride dissolved in solvent, at 1 5 - 3 5 O C , for 2-10 minues, followed by an optional washing stage and electroless plating. The applied Pd chloride may be reduced to Pd metal.

Activating Solution Containing Palladium

An alkali catalyst solution for non-electrolytic plating contains a water soluble Pd compound, a water soluble Sn compound, and a stabilising agent, and has a pH of 1 1 or more. The solution will not corrode the treating facility, which can be used for activation of any board plate which can be oxidised.

Vacuum Vapour Deposition Source Material

NIPPON MINING K.K. Japanese Appl. 62/235,473

TANAKA KIKINZOKU KOGYO Japanese Appl. 62/238,362

A source material for vacuum vapour deposition, such as Pt, is coated on the surface of a high melting point metal wire or tape heater. Good adherence to the heater is achieved, and a high quality vapour deposition fdm is obtained.

Autocatalytic Palladium Plating Solution

East German Patent 247,926 A solution suitable for autocatalytic deposition of Pd on metallic and nonmetallic materials contains a Pd compound, a reducing agent, a complexing agent, stabilisers, and organic oxime compound(s). The solution does not decompose spontaneously, and gives dense, f d y adherent metallisation.

V.E.B. BERGBAU FUNK A.


APPARATUS AND TECHNIQUE Liquid Metal Ion Source HUGHES AIRCRAFT CO. World Appl . 8716,407A A liquid metal ion source consists of an emitter of positively charged elemental ions, and a source for supplying the species to the emitter in the form of a congruently vaporising alloy: preferably As, supplied as an alloy with Pd. The ion source is used especially in ion implantation of semiconductor circuits.

Measuring Total Nitrogen Content in Water MITSUBISHI CHEM. IND. K.K.

Japanese Appl . 621198 ,758

An oxidation catalyst such as Cu-Ni-Pt is used in a reaction tube, in a heating furnace, preferably with a temperature gradient of 100-3w~C at the upper section of the catalyst layer. The catalyst converts N compounds in a sample to NO, which provides a method of determining total N content in water.

Heater for Diamond Growth with Anti- Corrosion Layer TOSHIBA K.K. Japanese A ppl. 621 202,896 A heater for the gas-phase growth of pure diamond by pyrolysis of an organic reaction gas, has a surface layer which is corrosion resistant to the organic en- vironment at high temperatures. The anti-corrosion layer consists of Pt, Ir, Os, Pd, Rh, Ru, Pt-Rh alloy, Ir-Ru alloy, SIC, TIN, graphite, etc. The heater is stable and has long service life.

Reliable Sensor Film

A sensor fdm consists of an oxide matrix with 3-90 vol.% of a single metal or alloy of at least one of Pt, Pd, Ir, Os, Rh, Ru, Au, Ag, Pb, In, Sn, Fe, etc., dispersed in the matrix. The sensor film is 0.1-100 pm thick, and can be produced by magnetron sputtering. It is used as a temperature or magnetic sensor, and has good measuring accuracy and reliability.

Gas Sensor with Low Alcohol Sensitivity

A gas sensor with low sensitivity to alcohol is made by moulding SnO, system gas sensitive matter, and adding a Rh-Pt complex catalyst to the surface part of the moulding. The total amount of Rh and Pt added is 2.5-250 micromoles/g SnO,, with a preferred molar ratio of Rh:Pt of 0.4-5. The sensor is useful for detection of H I , isobutane, CH, and CO.

Polymer Combustible Gas Sensor NIKKO RIKA K.K. Japanese Appl . 62/269,05 I

A polymer gas sensor is obtained by mixing polyimide resin with I-Iowt.% SnCI, and 0.5-7wt.Yo benzonitrile-Pd complex, and heat treating. The polymer gas sensor can accurately detect the presence of combustible gases such as H , , CH,, etc., even at high temperatures.

TANAKA DENSHI KOGYO Japanese Appl . 621214,601

EIGARO GIKEN K.K. Japanese Appl . 621254,047

Polymer Humidity Sensor NIKKO RIKA K.K. Japanese Appl. 621269,053 An Al 0, baseplate with a comb-shaped electrode of Pt-Pd screen printing is coated with a treated copolymer, and subjected to an ageing process. The polymer sensor so formed exhibits good sensitivity for humidity, even in wide high temperature regions, owing to its high heat resistance.

Measuring Head for Glucose Deter- mination CIE GEN. ELECTRICITE French Appl . 2,596,155 A measuring head for an electrode is produced easily and reproducibly by successive serigrapic deposition of porous Pt onto an inert support, and then a mixture of SiO , with amine functions and PTFE fibres, followed by activation and grafting of an enzyme. The measuring head has good response time, and is used to measure glucose in solution by enzymatic oxidation to H , 0 , . Platinum Catalyst for Oxygen Measuring Cell E. STEINMETZ

An 0 ion conducting solid electrolyte has both surfaces covered with a gas permeable catalyst such as Pt wool, at the thermocouple contact points. Reference and measuring chambers are positioned on opposite sides of the solid electrolyte, forming a measuring cell for determination of free 0, content of furnace flue gases.

Microelectrochemical Corrosion Tester

G e m a n Am/. 3,71 1,497

MOSCOW GUBKIN PETROCHEM. Russian Patent I ,296,920

An AC resistance meter and Pt electrodes form part of a microelectrochemical tester, which measures the voltage and resistance across part of the test material. The tester is used to measure corrosion in electrolytes, for developing new corrosion-proof materials, and gives improved precision and simplified measurements.

Sensitive Pressure Converter with Platinum Electrode CHERNOVITS A.S. UKR. Russian Patent 1,303,860 A pressure converter consists of a cell with one electrode of Pt wire, and the other of a monocrystalline selenide or telluride, intercalated with an alkali salt. The converter has improved sensitivity, since the structure ensures highly anisotropic mechanical properties, and high sensitivity to internal mechanical forces.

Voltammetric Analysing Electrode MOSCOW LOMONOSOV UNIV. Russian Patent I ,315,884 A voltammetric analysing electrode has a Pt tube containing C paste, and uses a piston to remove the surface layer of paste from the tube after each measurement. The electrode is used for analysis of electrical properties with improved accuracy.

Platinum Metals R e v . , 1988, 32, (3) 162

JOINING Multi-Purpose Brazing Filler Alloy

A brazing fdler alloy comprises 30-92 wt.% Pt, 0.5-10 wt.% of at least one of Re, Ti, Zr, Hf, V, Y, Cr, etc., and 0.5-69.5 wt.% of at least one of Pd, Au, Ag, Cu and Ni. The alloy is used for joining ceramic to ceramic, graphite, or metal, graphite to metal, and metal to metal, giving high brazing joint strength.

TANAKA KIKINZOKU KOGYO JapaneseAppl. 621275,596

Ruthenium Fischer-Tropsch Catalyst

A catalyst for use in Fischer-Tropsch hydrocarbon synthesis reactions consists of 0.2-2wt.% Ru supported on a TiO, support surface-modified with 2-10wt.% of an oxide of Nb, V or Ta.

Catalytic Composite for Dehydrogenating Paraffins UOP INC. U.S. Patent 4 , 7 1 6 , 1 4 3

EXXON RES. & ENG. CO. U.S. Patent 4,711,871

A platinum group metal and a Sn, Ge or Re component as modifier are surface impregnated on a refrac- HETEROGENEOUS CATALYSIS tory support so that most of the metal is in the outer

Three-Way Catalyst with Nickel to Iwpm layer of the catalyst particle. The catalyst has Reduce Hydrogen Sulphide Emissions improved selectivity for dehydrogenating paraffins to

, E ~ ~ ~ ~ ~ ~ Appl. 244,127~ olefms compared with a similar catalyst with uniform A three-way catalyst for controlling NOx, CO and

INc. distribution.

hydrocarbon emi&ions in automoiive exhaust gas consists of a supported platinum group metal and Ni, with a Ni:platinum group metal ratio of I : I - ~ o : I . The amount of Ni present is sufficient to reduce H, S emissions when used under fuel-rich conditions.

Catalyst for Deoxygenation of Aqueous Media BAYER A.C. European Appl. 246,533A Removal of 0 from aqueous media is effected by catalytic reduction using a catalyst of Pt or Pd on a macroporous weakly basic anion-exchange resin, based on crosslinked polystyrene. The catalysts have improved catalytic metal retention and stability.

Thermally Stable Fluorosilicone Gel DOW CORNING CORP. European Appl. 252,665A A fluorinated polyorganosiloxane composition containing a Pt catalyst cures to a thermally stable, clear fluorosilicone gel, used to coat PCBs and other sub- trates on which electronic components are mounted. These gels are resistant to discoloration and hardening at above IOOOC, so can be used in vehicle engine compartments.

Higher Activity Naphtha Reforming Catalysts STANDARD OIL c o . (IND.) U.S. Patent 4,703,031 Naphtha reforming catalysts for gasoline production consist of one of Pd andlor Pt, optionally together with Sn or Re, deposited on a porous support. The catalysts have a surface area greater than 300 mzlg, and a defined pore volume distribution. Activity IS higher than for prior art catalysts, with equal selectivity for C5 + gasoline.

Gas Turbine Catalyst with Reduced NOx Generation TOKYO ELEC. POWER CO. INC.

Japanese Appl. 621216 ,642

A catalyst for a gas turbine is made by coating a cor- dierite honeycomb support with 7-Al , 0, containing a rare earth element, followed by impregnation with Pt, Pd, Rh, Ru, etc., so that the weight ratio of noble metal:rare earth element is at least unity. The catalyst has excellent low temperature ignition and high temperature durability, and generation of NOx is reduced.

Catalyst for Carbon Monoxide Removal from Waste Air T. KAGITANI Japanese Appl. 62/221,424 A catalyst of Pd, Rh, Ru, Ag, or their mixtures supported on TiO, Ti(0H) , or Zn(0H) , can be used in the treatment of 0-containing waste gas containing CO, by a process of U.V. irradiation in the presence of ozone. The method is useful for removal of CO by oxidation from 0-containing waste gases such as air or combustion gas.

Selective Hydrogenation Catalyst K. SAITO Japanese Appl. 621221 ,447

A selective catalyst for a H adding reaction to a chain unsaturated hydrocarbon contains at least one of Ru, Rh, Pd, Pt, Os, or Ir, at least one of Y or a rare earth element, and B. The catalyst has excellent ability at low and normal temperatures, is stable in air, tolerant to 0,, and is reproducible.

Selective Hydrogenation Catalyst Con- - - taining Palladium

Durable Palladium-Ferroborosilicate NIPPON ZEON K.K. Japanese Appl. 621230,733 Catalyst Composition Selective hvdroaenation of diolefins to monoolefins is NATIONAL DISTILLERS CORP. U.S. Patent 4,707,500 A long life catalyst consists of Pd ion exchanged or impregnated onto a crystalline ferroborosilicate composition. Synthesis gas is converted with high selectivity to low molecular weight (2-4C) alkanes.

achieved a; O-I-SO~C using a supported catalyst containing Pd and possibly Pt, Rh, Ru, Ir, W, or alkali metals, which has been treated with hydrocarbons at o-15o0C prior to use. This pretreatment gives better control over product formation.


IOHNSON MATTHEY

Catalyst for Lower Paraffinic Hydrocar- bon Production MITSUBISHI HEAVY IND. K.K.

Japanese Appl. 621246,993 A solid super acid catalyst is prepared by im- pregnating a metal hydroxide or oxide carrier with Pt, Ru, Rh, Pd, Os, Ir, Ni, etc., treating with H,SO,, and calcining. The catalyst is used in the production of paraffinic hydrocarbons containing a maximum of 10c by heat treating high boiliig hydrocarbons such as shale oil at 150-35oOC and at least 50 atm H,.

Tritium Leakage Prevention Device TOSHIBA K.K. Japanese Appl. 621247,294 A T oxidation catalyst consisting of alumina ceramics carried by Pd or Pt is positioned on the outside surface of apparatus containing T. Leakage is prevented perfectly by conversion of monomer penetrating the apparatus to T steam.

One-Step Trifluoroethylene Preparation NIPPON HARON K.K. Japanese Appl. 621252,736 Trifluorwthylene is produced inexpensively in one- step by reacting chlorotrifluoroethylene and H, in the presence of a platinum group metal catalyst, at 50-3OOoc. The catalyst consists of compounds of Pt, Pd, Rh, Ir, Ru or 0 s supported on active C or AI,O, at o.r-gwt.% metal; with Pd or Ru catalysts being preferred to give high yields of product.

Exhaust Gas Purification Catalyst

A monolith catalyst for exhaust gas purification is produced by immersing a substrate with a support layer in a noble metal solution containing Pt, Rh or Pd salts, and applying direct voltage between electrodes inserted in the metal substrate. The noble metal deposits in the deeper parts of the support layer where it is protected from poisons, so high activity is maintained for a long time.

Ruthenium-Copper Partial Hydrogena- tion Catalyst FUJI KAGAKU KOGYO Japanese Appl. 621255,438 A catalyst of o.o1-5owt.% Ru:carrier and Cu:Ru = 2-20wt.% dispersed in solid obtained from a metal hydroxide colloid is used for partial hydrogenation of aromatic hydrocarbons. The catalyst can be prepared readily and cheaply, and is used to produce cyclomonoolefis in about 30-40% yield.

Catalyst for Preparation of Phenolic Compounds

TOYOTA JIDOSHA K.K. Japanese Appl. 621254,848

DAICEL CHEM. IND. K.K. Japanese Appls. 621255,443144

Phenolic compounds are produced by hydrogenating or dehydrogenating cyclic ketones in the presence of a 0.05-1gwt.% Pd andlor Pt catalyst, at 150-4oo~C. The process can give phenolic compounds with high selectivity useful as pharmaceuticals, etc.

Trichlorosilane Production MITSUBISHI METAL K.K. Japanese Appl. 621256,713 Trichlorosilane is produced by passing a gaseous mixture of SiCI, and H, through a Si layer containing 0.001-20 mol.% of Pd, Ru, Rh, Ir, or their compounds. The yield of trichlorosilane is 2-3 times higher than from conventional methods, and it is produced at the relatively low temperature of 3oo-700°C, at a pressure above atmospheric.

One-Step Preparation of Methyl Isobutyl Ketone SUMITOMO CHEM. IND. K.K. JapaneseAppl. 62/258,335 A catalyst consisting of 0.01-5.0wt.% Pd on a support of y-AII 0, and one or more of Ca oxide, Mg oxide, and Sr oxide, is used in the preparation of methyl isobutyl ketone from acetone and H, at 8o-25o0C. The catalyst gives high activity and selectivity for a long time, and facilitates preparation of the product by a one-step reaction.

Catalytic Burner with Improved Heat Resistance MATSUSHITA ELEC. IND. K.K.

Japanese AppI. 621266,307 A heat resistant catalytic burner selectively carries a catalyst including Pd, Rh, etc., on a heat resistant semiconductor such as Ti oxide, which is on the surface of carrier materials such as SiO, and Al , 0,. The life of the catalytic burner is improved.

Palladium Catalyst for Tritium Removal TOSHIBA K.K. Japanese Appl. 621268,931 A ventilation air conditioner contains a catalyst of Pd or PtlAI, 0, in the air conditioner or circulation flow piping, to remove atomic T by conversion to the oxide as steam. A separate T cleaning plant is not required, which saves cost and space.

Oxidation Catalysts Containing Platinum Group Elements KAO CORP. Japanese Appls. 621269,745146 A catalyst contains 0.1-20wt.% of Pd, Pt, Ru, or Rh, 0.001-20wt.% of a second component which may be Sn, Bi, etc., and 0.01-20wt.% of one or more rare earth elements, on an inorganic support. The catalysts have high activity and selectivity, and are used to produce carboxyl compounds or ketones by oxidising hydroxy compounds or aldehydes, or to produce oxides of saccharide.

Durable Palladium Catalyst for Exhaust Gas Purification

An exhaust gas purification catalyst consists of 0.06-0.185wt.% Pd in a defective perovskite complex oxide, with I O - ~ O % solid-soluble Pd, and the rest present as PdO or Pd. The catalyst is used for purifying CO, HC and NOx in the exhaust, has good high temperature durability, and inhibits NH , .

TOYOTA CENT. RES. & DEV.JapaneSe Appl. 621269,747


Catalyst Composite to Oxidise Saccharides KAO CORP. Japanese Appl. 621269,748 A catalyst composite consists of an inorganic support with 0.1-20wt.% of (i) Pt, Ru, Rh or Pd, (ii) Sn, Bi or Sb, and (iii) Se, Sn or Te. The catalyst is used to produce a higher yield of oxidised saccharides.

Perovskite Complex Oxide Catalyst

A new catalyst consisting of a perovskite complex oxide with structure ABO j, can contain Pt as a skeletal atom, or Pd or a mixture of Pd and Ce as the B-site ion. The catalyst is used for removing CO, hydrocarbons and NOx from I.C.E. exhaust.

TOYOTA JIDOSHA K.K. Japanese Appl. 621282,642

Hydrocarbon Conversion Catalyst with Improved Activity INST. FRANCAIS DU PETROLE French Appl. 2,594,71 I A supported hydrocarbon conversion catalyst with improved activity and life contains 0.01-2wt.~/o of platinum metals, one of these being Pt, one or more of Sn, Ge, Pb, Ga, In, and TI, and halogen(s). The metals are introduced as organometallic compounds, which give uniform distribution. The catalyst is useful for reforming for gasoline production, isomerisation, hydrodealkylation, etc.

Naphtha Reforming to Naphthene-Rich Products V.E.B. LEUNA-WERK ULBRICHT

East German Patent 246,486 A reforming catalyst mixture consists of 0.1-1 .OWL% Pt with additional metals such as Re, Ir, Sn, and G, on shaped support particles of zeolite mixed with hydrous Al oxide and optionally Al , 0,. The catalyst is used for production of naphthene-rich engine fuel components with reduced aromatics content.

Fluorine-Modified Platinum Reforming Catalysts V.E.B. LEUNA-WERK ULBRICHT

East German Patent 247,792 Catalysts for reforming gasoline-range hydrocarbons consist of Y-shaped profde Al , 0, extrusions containing 0.1-1.0wt.Yo Pt, Q and F, with specified physical characteristics. The catalysts are especially useful in the presence of high water concentrations, for selective production of aromatics-rich fractions, useful as high-octane gasoline components.

Platinum Catalyst for Production of Anthraquinone Derivatives KAZA UNIV. Russian Patent 1,310,387 Alpha-sulphonic acids of methyl andlor hydroxy- anthraquinone derivatives are obtained more simply, and without using an autoclave, by treating the corresponding anthraquinone with oleum, at 70-90OC for 6-8 hours, using o.o~-o.~wt.% PtO, as catalyst.

HOMOGENEOUS CATALYSIS Aldehyde Recovery DAW MCKEE LONDON British Appl. 2,192,182A An optionally substituted 7-17C aldehyde can be recovered from production by hydroformylation using a Rh catalyst, by degassing, evaporating the aldehyde and recycling the catalyst containing liquid stream. By this method the catalyst deactivation is substantially eliminated.

Preparation of Aromatic Carboxylic Acids EASTMAN KODAK CO. U.S. Patent 4,70589~ Aromatic carboxylic acids are prepared with high selectivity by carbonylation of aromatic iodides in the presence of CO, a Ru catalyst, a metal iodide, and a base. High yields are obtained under mild reaction conditions. The process is useful for preparation of certain dicarboxylic acids, which are used in the preparation of polyesters.

Preparation of Hydrogen Peroxide from Water BOC GROUP P.L.C. US. Patent 4,711,772 An improved preparation of H, 0, by reaction of CO, 0, and H,O is effected in the presence of a soluble Pd compound, an mine or phosphine ligand, a non- co-ordinating acid and a solvent. Use of the ligands allows direct oxidation of H,O to be effected without using additional chemical reactions to trap H,O,.

Palladium Catalyst for Aromatic Ester Preparation ASAHI CHEMICAL IND. K.K. Japanese Appl. 621201,847 Diphenyl ether carboxylic acid esters are prepared by reacting iodinated diphenyl ethers with CO and aromatic alcohols in the presence of 0.01-10 mol.% of a Pd catalyst, and a base. The esters are prepared in high yield without using triphenylphosphine.

Monohydric Alcohol Preparation with Improved Selectivity AGENCY OF IND. SCI. TECH.

Japanese Appls. 621209,031132 Monohydric alcohols are prepared by reacting CO with H, using a catalyst system of Ru compounds, H halides, phosphine oxides, and Ti, Al or V compounds. The reaction is carried out in aprotic polar solvents, under elevated pressure, at I 50-35oOC. Adding Ti, Al or V compounds markedly improves production and selectivity of methanol and ethanol.

Organic Peroxide Preparation SUMITOMO CHEM. IND. K.K. Japanese Appl. 62/212,360 Preparation of an organic peroxide in good yield involves reacting a specified tertiary amine with a hydroperoxide in the presence of a Ru or Rh catalyst, such as RuCI,(PPh,),. The organic peroxide produced is useful as an intermediate for medicines.

Platinum Metals Rev. , 1988, 32, ( 3 ) 165

Palladium Catalyst for Aldehyde and Ketone Production BASF A.G. German Appl. I ,643,623 Production of aldehydes and ketones in high yield from olefins with one or more double bonds is effected by oxidation with HNO , in the presence of a Pd compound. Reaction occurs at 90-20o0C in an aqueous medium containing 0.5-1% HNO,, 0.8-1.5% Pd(NO,),,and 5-1o%ofa Agcompound. The products are useful for production of solvents, pharmaceuticals and plastics.

Glycol Aldehyde Preparation Using Rhodium Catalyst TOPCHIEV. PETROCHEM. SYNTH.

Russian Patent 1,310,383 A catalyst consisting of Rh chloride and triphenyl phosphine in a ratio of PPh ,:Rh of 2-10 mollg-atom is used in the hydroformylation of formaldehyde. The method is used to prepare glycol aldehyde. The process is simple, and gives both increased productivity and significantly increased selectivity.

FUEL CELLS Platinum-Copper Electrocatalyst and Fuel Cell Electrode NIPPON ENGELHARD LTD. British Appl. 2,rgo,537A An electrocatalyst of enhanced stability and activity comprises a €4-Cu alloy containing 15-~oat.% Cu on a carrier of C black, acetylene black, graphite or WC. The electrode is used in an acid electrolyte fuel cell.

Gas Diffusion Electrode with Improved Performance TANAKA KIKINZQKU KCGYO

Japanese Appl. 621208,554 A gas diffusion electrode used for fuel cells, secon- dary cells, and anodes for plating has a reaction layer with alternately disposed hydrophilic and water repellant parts. The hydrophilic part consists of platinum group metals and/or their oxides, graphite, and F'TFE, and the water repellant part consists of C black and PTFE. Greater catalyst-electrolyte contact gives improved performance.

GLASS TECHNOLOGY Bushing with Coating to Improve Fibre Drawing Properties

Platinum Crucible for Glass Production T o s n m A GLASS K.K. Japanese Appl. 621212,227 During glass production in a Pt crucible, Mg, Ba, Ca, and Sr nitrates are added to the starting materials to prevent dissolution of Pt into the molten glass and to allow crucible use over long periods.

Platinum Crucible for Single Crystal Pro- duction TOHOKU METAL IND. LTD Japanese Appl. 621230,692 A vertically movable crucible used for single crystal production is made of Pt or Pt alloy, and has an outer wall forming a sealed space around the crucible body. The crucible is heated, and the temperature of the inner wall can be lowered.

Platinum Crucible for Crystalline Oxide Production SUMITOMO ELEC. IND. K.K. Japanese Appl. 621246,895 The inner surface of a Pt or Pt-Rh alloy crucible is lined with a high melting point material comprising one of the constituents of the oxide crystal to be produced. Crystals of good quality are produced, without discoloration by impurity inclusion from the crucible material.

ELECTRICAL AND ELECTRONIC ENGINEERING Spark Plug with Noble Metal Spark Tip NGK SPARK PLUG K.K. European Appl. 243,529A A spark plug has a 0.1-1.0 mm thin layer of ultrasonically bonded noble metal powder on at least one of the electrode discharge surfaces. Preferably the noble metal powder is Pt, Pd, Ru, Ir, Rh, Au, or alloys, or an alloy with Ni, W or WSi, with a particle size of 10-5ca pm. High bond strength between the noble metal tip and electrode is achieved; and noble metal wastage is avoided.

Multilayered Vertical Magnetic Record- ing Medium IBM CORP. European Appl. 243,860A A magnetic recording medium with enhanced vertical magnetic recording consists of a substrate with multiple magnetic layers, each comprising a non- magnetisable nucleating fdm, and a magnetisable alloy fdm. The non-magnetisable fdm is preferably COW, and the magnetisable fdm consists of an alloy of Co and Pt, Pd, Re or Ni, preferably Copt.

NIPPON G i S S SEN-I. Japanese Appls. 621207,736-38 Pt alloy bushing is used for drawing of glass fibres, and has a glass outflow part coated with a substance of immoved wettabilitv. contact anale or reduced

Palladium-Based Layers for Switch 'Ontact'

SIEMENS European Appl. 247,541A volatiity than the bushing material: The coating substance can be Pt-Au alloy, Pt-Rh-Au alloy, Rh, Au, TiN, AIN, etc. The coating improves fibre drawing properties, and prevents loss of the bushing material by volatilisation.

A non-noble metal contact spring is galvanically coated with a 3-5 pm thick baselayer of Pd with 10-5owt.% of at least one of Ni, Cu and Co, followed by a 0.1-1 pm thick top layer of Pd with 10-40wt.% Ag or Au. The Pd-based layers form contacts.


Palladium Plated Integrated Circuit Lead Frame TEXAS INSTRUMENTS INC. European Appl. 250,146A A lead frame comprises Pd or Pd-Ni d o y plated leads and lead ends for connection to a component, and a semiconductor support for contacting an I.C. The lead frame does not require Ag spot plating or solder dipping, and strong thermosonic bonds to the Au wires are formed.

Spark Plug Centre Electrode Manu- facture ALLIED CORP. U.S. Patent 4,705,486 Making the central electrode for a spark plug involves striking an Inconel wire having a Pt tip with a force which extends the cylindrical bore, while the Pt flows along the chamfer to completely cover the weld. This method prevents deterioration of the electrical flow path by corrosion, and improves the fuel efficiency and longevity of the spark plug.

Platinum-Manganese-Antimony Magnetic Thin Film MITSUBISHI CHEM. IND. K.K.

Japanese Appls. 62/230,010 and 621231,440 A magnetic thin fdm is formed on a substrate and consists of either Pt-Ni-Mn-Sb, or a Pt-Mn-Sb material with a perpendicular magnetisation film perferably made from MnCuBi, or MnBi, on its base. The magnetic film is used in (i) photomagnetic recording media, giving large coercive force and improved Kerr-rotation angle, or (ii) magnetic optical mirrors to polarised beams.

Palladium-Silver Thick Film Paste TDK CORP. Japanese Appl. 621237,605 A paste for a thick film contains Pd and Ag as major components, a glass component, and a metal hydroxide. The paste can be applied to an Al nitride sintered body substrate, then dried and sintered to metallise the substrate surface.

~ ~ l ~ i ~ l ~ ~ ~ ~ i ~ ~ i ~ ~ L~~~~~ for %-Film Microcircuits

Multiple resistive layers are on a dielectric substrate by depositing successive layers of Ta,N, Ti and Pd, plating a thin Au layer on selected portions

The resistors produced are temperature stable and

thin-fdm microcircuits.

Ion Exchange Film for Electrochromic Display Element

An electrochromic display element includes a bipolar ion exchange film containing and anion- exchange layers and a Pt as

layers, or in each layer. In the electrochromic display

displayed.

U.S. DEFT. OF ENERGY U.S. Patent Appl. 061894,145 SODA "" Japanese 62'238y536

Or

of the pd, and then selectively masking and etching. catalyst tto o the

laser-t-ble for precise deffition, and me used in the character Or image can be

Thermionic Cathode with Osmium Coated Surface

A thermionic cathode comprises an impregnated porous W matrix body having an electron-emitting surface coated with a thin layer of refractory material such as Os, deposited by CVD. The cathode provides high electron emission density, long life and high substrate adhesion, and is used in high power electron tube devices such as microwave generators.

Long Life Tungsten-Iridium Cathode

U.S. SEC. OF NAVY U.S. Patent Appl. 07/029,514

U.S. SEC. OF THE ARMY U.S. Patent Appl. 071046,343

A cathode consisting of a 65134 by weight mixture of W and Ir powder, with ~ w t . % Zr hydride, is impregnated with Ba,Ir,O, to enhance cathode life and current density. The cathode is used especially in microwave devices.

Opto-Magnetic Recording Medium HITACHI MAXELL Japanese Appl. 621200,552 An opto-magnetic recording medium is produced by sputtering a target d o y consisting of a rare earth metal, a transition metal and a corrosion resistant element. The latter may be Pt, Ru, Rh, Pd, Ir, Nb, Hf, W, Zr, Cr, etc. The sputtering target is easily pro- cessed, and production efficiency is improved.

Magnetic Recording Medium Containing Platinum FUJI ELECTRIC MFG. K.K.

Japanese Appls. 62/239,420l21 A magnetic recording medium includes a magnetic layer of a Co-Ni alloy containing I-Iqat.% Pt, and 4-12at.Oh Sm or 2-7 at.% Gd. Adding Pt and Sm or Gd increases the coercive force of the magnetic layer. The medium is produced with high efficiency, and is used for magnetic discs for magnetic recording devices; giving high output and long life.

Radiation Image Conversion Panel

A radiation image conversion panel consists of a support, a fluorescent layer, and a stimulative fluorescent substance, such as Ru(I1)-activated alkaline earth metal halide dispersed in a binder, and a protective resin layer. The material can be used in medical X- ray photodiagnosis, etc.

Cobalt-Platinum Magnetic Thin Film SEIKO EPSON K.K. Japanese Appl. 621262,414 A multilayer fdm for use in magnetic recorders is produced by laminating a Co-Pt magnetic thin f h with 40-6awt.% Pt, on a Cr thin film on a base plate, and heat treating at 450°C or above. The coercive force of the Co-Pt magnetic thin fdm can be increased, with reduced variance, by this method.

FUJI PHOTO FILM K.K. Japanese Appl. 621247,298

Platinum Metals Rev., 1988, 32, (3 ) 167

containing containing

containing

the character Or Compound

Amorphous Alloy for Magnetic Heads ALPS ELECTRIC K.K. Japanese Appl. 62/270,741 UNIW. WARSZAWSKI European Appl. 252,324A An amorphous alloy containing 1.5-4.0Yo Ru, and The preparation of metal cis-dichloro- Fe, Co, Cr, Si and B, is used for magnetic heads, hav- dimethionineplatinate involves addition of a metal ing improved corrosion resistance, wear resistance salt to the Pt component, where the metal is especial- and saturation magnetic flux density. ly Yb-169. The product has low toxicity, good

radionuclide parameters for scintigraphic examina- Ignition Plug with Noble Metal Catalyst tions and for diagnosis of neoplasm. R. BOSCH c.m.b.H. German Appl. 3,616,641

Bis-Platinum Anti-Tumour Complexes A noble metal, preferably Pt and/or Pd, is doped into the surface of the insulating body of an ignition plug, A”UJLIS RES. CORP. U.S. Patent 4,720,504 at least on the side facing the combustion region. The Pt complexes such as benzene pentacarboxylato bis- noble metal catalyses the ignition of the fuel andlor (I ,2-diaminocyclohexane Pt(I1)) are used in the treat- the propagation of ignition. The ignition plug is used ment of malignant tumours such as myeloma, for a combustion engine. leukaemia and carcinoma. The bis-Pt complexes can

be tailored to deliver 2 doses of diaminoplatinum ions

Low Toxicity Cis-Platinum Compound

TEMPERATURE MEASUREMENT Accurate Temperature Measurement Using Neutron Transmission ROLLS-ROYCE LTD. British Appl. 2,192,055A The temperature of an object such as a gas turbine engine component is measured by (i) plating various surfaces with a different element, such as Pt, Ir, Re, and (ii) monitoring for each element the thermal Doppler broadening of resonances in the neutron transmission characteristics. Using this method accurate temperature measurements in a number of areas of the object can be made.

Gamma-Thermometer with Platinum Section SIEMENS A.C. European Appl. 243,579A A gamma-thermometer with high sensitivity and short time constant consists of a rod fitted with an en- casing tube and a thermocouple arrangement. The rod has a Pt section fitted as gamma-absorber and thermal link. The gamma-thermometer is used to measure temperature rise from which the absorbed gamma radiation can be derived.

Measuring Resin Temperature for Injec- tion Moulder

The resin temperature in a mould for an injection moulder is detected by a low cost temperature sensor

DAIWA KOGYO K.K. Japanese Appl. 621204,915

at a chosen rate and are readily water soluble and suitable for oral administration.

Electrode for Heart Pacemaker TANAKA KIKINZOKU KOCYO

Japanese Appls. 62/204,765-67 Manufacture of an electrode for a heart pacemaker involves applying a surface coating of Pt and IrO, or a mixture of Pt and a platinum group metal oxide, to a substrate of Pt, Pt alloy, Ti, or Ti alloy. A coating membrane layer is formed, 0.5 pm or more thick. The properties of the electrode result in prolonged battery life.

Generating Oxygen Gas for a First-Aid Respirator N . UENO Japanese Appl. 621216,903 A suitable amount of colloidal Pt is added to an aqueous solution of Na,CO, and H,O, adduct, or the solution is added to colloidal Pt, to generate 0, gas immediately for a fmt-aid respirator. The colloidal Pt is enclosed in a capsule which is broken to generate a given amount of 0, when used.

Blood Glucose Sensor SHINGIJUTSU KAIHATSU Japanese Appl. 621261,341 A glucose sensor for use in the body consists of a cylindrical Ag-AgC1 cathode system and a Pt anode inserted into the cylindrical cathode. On the anode tip are several fdms and a fwed glucose oxydase film. The sensor can precisely measure the blood glucose concentration with high sensitivity, for a long time.

such as Pt, buried in the tip of an insertion part, an ejector pin, a dummy pin, a core pin, or a sleeve. F h h x d Toxicity Platinum Anti-Tumour

Preparation

A Pt complex medical preparation contains a Pt com- NIPPON KAYAKU K.K. Japanese Appl. 621292,722 MEDICAL USES

Implantable Cochlear Prosthesis plex suchas cisplatin, A d a water-soluble magnesium salt such as MgC12. The medical preparation is effective as an anti-tumour agent, with lower toxicity to COMMONWEALTH AUSTRALIA

APP1. 2473649A the kidneys. An implantable cochlear prosthesis comprises an electrode array consisting of thirty-two Pt bands moulded with a flexible carrier. Power and data are supplied to the implanted cochlea stimulator across the skin.

The New Patents abstracts have been prepared from material published by Dement Publications Limited.


platinum metals review

Documents