548 Abstracts

can lead to serious disagreement between the calculated and real L. values if strain is not considered to modify the scattering profiles.

ture range studied which differ with respect. to their microstructure as determined by TEM studies and with respect to their micropore spectra, density, inner surface, degree of order, crystallite size and oxidation rate.

52. Structural parameters and molecular sieve properties of carbons prepared from metal carbides 56. Influence of low-order material on the irradiation

H. P. Boehm and H. H. Warnecke (Institutf anorgan. Chemie d. Universitat, Munchen, Germany). Carbon was prepared by chlorination of TaC at 500°C. This carbon gives an extremely weak X-ray diffractogram. It graphit- izes quite well at 28OO”C, however. With increasing heat-treatment, the L, dimension grows preferentially, while L, increases only above 1700°C. The microporous carbons show pronounced molecular sieve properties after HT from 1500 to 1700°C.

behavior of pyrocarbon coatings?

53. Void growth in glassy carbon M. Biswal and R. H. Bragg (University of California,

Berkeley, CA 94720, U.S.A.). Isochronal heat treatment data in the range lOOO-2500°C indicate a monotonic increase in l,, (l,,,) and S/V, and a decrease in bulk density p. Kinetic data of (I,,,,) and S/V at 2000 and 2500°C HTT indicate a factor of four increase in rate over this range.

P. Krautwasser (Kemforschungsanlage Julich GmbH, D-5170 Julich) and C. S. Yust (Oak Ridge National Laboratory, Oak Ridge, Term 37830, U.S.A.). The changes in the percentages of a porous, low-order component and two dense, high-order components in pyrocarbon coatings of fuel particles have been studied as a function of deposition temperature and compared to the irradiation behavior. The components can be identified by their different porosity distributions, inner surface and degree of order by means of small-angle X-ray scattering and by their different microstructure in TEM microg- raphs. A correlation was found between the percentage of the low-order component and the irradiation behavior of the coatings.

tResearch sponsored by the Energy Research Development Administration under contract with the Union Carbide Corpora- tion, and by the Kernforschungsanlage Jtilich GmbH.

54. Influence of deposition gas and gas mixtures on the micropore spectra of pyrocarbon coatings, and pre- diction of irradiation behavior

P. Krautwasser and H. Nickel (Kernforschungsanluge

57. The new method for determining softening points of pitches

Julich GmbH, D-5170 Julich). The pore size distribution, inner surface and degree of order of coatings derived from propene, acetylene, methane and propene-acetylene mixtures have been compared. The deposition tempera- ture varied between 1200 and 2000°C. The changes in the percentages of the material components as a function of deposition temperature are by and large similar in the pyrocarbons deposited from the different gases. How- ever, in the case of individual deposition temperatures, considerable differences may result in the percentages of the components which allows the conclusion of different irradiation behavior.

E. R. McHenry (Union Carbide Corporation, Cleve- land, OH 44101, U.S.A.). The softening point is the primary specification for pitches. A more rapid, accurate, and precise method for measuring the softening point of pitches has been developed through a modification of the Mettler FP 3/31 automatic melting point determination unit. This new technique covers a wider range of softening points then any other presently-used standard method. This report discusses the instrument modifica- tion, the ASTM round robin evaluation, the acceptance of the new test, and the possible application for measuring asphalt softening point.

55. Identification of three components in pyrocarbon coatings by transmission electron microscopy (TEM) and measurements of microporisity, inner surface, degree of order and crystallite size?

P. Krautwasser, H. Luhleich, H. Nickel and E. Pollmann (Kemforschungsanlage Julich GmbH, D-5170 Julich) and C. S. Yust (Oak Ridge National Laboratory, Oak Ridge, Tennessee, U.S.A.). The microstructure of pyrocarbon coatings, derived from propene in the temperature range between 1100 and 2000°C was investigated by TEM and compared to the properties, microporosity, inner surface and density fluctuation determined through small-angle X-ray scattering as well as the density and apparent crystallite size, L,. Three different material components were found in the tempera-

58. Grain growth of the stress-annealed pyrolytic graphite N. Okuyama and K. Takeya (The University of

Electra-Communications, Chofu-shi, Tokyo 182, Japan). The effect of temperature and time of subsequent annealing on the microstructure, grain growth and dislocation density is investigated of the stress-annealed pyrolytic graphite using an oxygen etch technique. Two types of grain growth are observed. The dependence on annealing time is experimentally obtained for the grain size and the density of non-basal dislocations.

59. Optical image analysis of graphite pore structure

tResearch sponsored by the Energy Research Development Administration under contract with the Union Carbide Corpora- tion, and by the Kernforschungsanlage Julich GmbH.

R. E. Smith and S. L. Strong (Union Carbide Corporation, Cleveland, OH 44101, U.S.A.). An optical image analysis system (OIAS) has been used to measure the pore structure of several line-grain commercial graphites. Pore shape information, not usually available with other techniques, has been measured. This informa- tion includes apparent cross-sectional area, longest chord, aspect ratio, and orientation of each pore.