M A T E R I A L S R E S E A R C H S O C I E T Y S Y M P O S I U M P R O C E E D I N G S V O L U M E 180

^Better Ceramics T h r o u g h Chemistry I V

Symposium held Apri l 16-20 , 1990, San Francisco, California, U .S .A .

EDITORS:

B r i a n J J . Z e l i n s k i University of Arizona, Tucson, Arizona, U .SA.

C . Jeffrey B r i n k e r Sandia National Laboratories, Albuquerque, New Mexico, U.SA.

D a v i d E . C l a r k University of Florida, Gainesville, Florida, U .SA.

Donald R. U l r i c h Air Force Office of Scientific Research, Washington, D.C., U.S.A.

I M I T ? 1^1 M A T E R I A L S R E S E A R C H S O C I E T Y |1V1|1\| J I pjttsbuj-gh, Pennsylvania

Contents

DEDICATION x v i i i PREFACE x i x ACKNOWLEDGMENTS x x i MATERIALS RESEARCH SOCIETY SYMPOSIUM PROCEEDINGS x x i i

PART I : REACTION MECHANISMS AND KINETICS

•SOL-GEL CHEMISTRY OF HYDROGENOSILICONATES: THE ROLE OF HYPERVALENT SILICON SPECIES 3

V. B e l o t , R. C o r r i u , C. Guerin, B. Henner, D. L e c l e r c q , H. Mutin, A. Vioux, and Q. Wang

HIGH PRESSURE RAMAN STUDY OF THE HYDROLYSIS REACTION OF TMOS AND TEOS 15

G. Hoang, J. Watson, and T.W. Zerda

•CURRENT ISSUES IN SOL-GEL REACTION KINETICS 21 Roger A. Assink and Bruce D. Kay

•MOLECULAR ARCHITECTURE AND ITS ROLE IN SILICA SOL-GEL POLYMERIZATION 29

P.C. Cagle, W.G. Klemperer, and C.A. Simmons

SYNTHETIC AND STRUCTURAL STUDIES OF BISMUTH/COPPER ALKOXIDES 39

W i l l i a m J. Evans and John H. Hain, J r .

PART I I : PRECURSOR EFFECTS AND AQUEOUS CHEMISTRY

•MOLECULAR STRUCTURE OF METAL ALKOXIDE PRECURSORS 47 C. Sanchez, P. Toledano, and F. Ribo t

•MOLECULAR ROUTES TO TIN OXIDES 61 T.A. Wark, E.A. G u l l i v e r , L.C. Jones, M.J. Hampden-Smith, A.L. Rheingold, and J.C. Huffman

TAILORED MOLECULAR PRECURSORS OF YTTRIUM OXIDE USING FUNCTIONAL ALCOHOLS AND ACETYLACETONE AS MODIFIERS 7 3

L i l i a n e G. H u b e r t - P f a l z g r a f , O l i v i e r Poncelet, and Jean-Claude Daran

NMR SPECTROSCOPIC INVESTIGATIONS OF PbTi0 3 SOL-GEL PROCESSING 79

S.D. Ramamurthi and D.A. Payne

• I n v i t e d Paper

•REVIEW OF HYDROLYSIS BEHAVIOR OF IONS IN AQUEOUS SOLUTIONS

R.E. Mesmer and C.F. Baes, J r . •HYDROLYSIS OF ALUMINUM - ARE ALL GELS CREATED EQUAL?

T.E. Wood, A.R. S i e d l e , J.R. H i l l , R.P. Skarjune, and C.J. Goodbrake

SMALL-ANGLE NEUTRON SCATTERING AND 27AL NMR STUDIES ON THE MICROSTRUCTURE AND COMPOSITION OF ALUMINA SOL-GELS

L.F. Nazar, D.G. Napier, D. Lapham, and E. Epperson

SMALL ANGLE X-RAY SCATTERING STUDIES OF POLYMERIC ZIRCONIUM SPECIES IN AQUEOUS SOLUTION

J.A. Jutson, R.M. Richardson, S.L. Jones, and C. Norman

PART I I I : PROCESSING SCIENCE I : AGGREGATION, PARTICLE GROWTH AND CONCENTRATED DISPERSION

•PRECIPITATION OF UNIFORM PARTICLES: THE ROLE OF AGGREGATION

C.F. Zukoski, M.K. Chow, G.H. Bogush, and J-L. Look •SIMPLE MODELS FOR PARTICLE AGGREGATION, DEPOSITION AND SEGREGATION

Paul Meakin MECHANISMS OF SILICA AND ΤΙΤΑΝΙΑ COLLOIDAL PARTICLE FORMATION FROM METAL ALKOXIDES

Joseph K. B a i l e y and Martha L. Mecartney

•SHEAR INDUCED ORDER OF CONCENTRATED DISPERSIONS Bruce J. Ackerson and T.A. M o r r i s

CONSOLIDATION OF COLLOIDAL SUSPENSIONS Wei-Heng Shih, Seong I I Kim, Wan Y. Shih, Chris t o p h e r H. S c h i l l i n g , and I l h a n A. Aksay

•RHEOLOGY AND MICROSTRUCTURE OF CONCENTRATED SUSPENSIONS Lis a A. Mondy and Alan L. Graham

RHEOLOGICAL AND RELATED COLLOIDAL ASPECTS OF AQUEOUS PROCESSING THAT AFFECT THE DEVELOPMENT OF MICROSTRUCTURE

Alan B l e i e r and C. Gary Westmoreland

PREPARATION OF MULTICOMPONENT CERAMIC POWDERS BY SOL-GEL PROCESSING

J.R. B a r t l e t t and J.L. Woolfrey

PART IV: PROCESSING SCIENCE I I : GELATION, AGING AND DRYING

•FRACTAL STRUCTURE AND FRACTAL TIME IN SILICA SOL-GELS James Ε. M a r t i n and Jess Wilcoxon

• I n v i t e d Paper

vi

2 9 S i NMR STUDY OF SILICON ALKOXIDES: FROM THE CONDENSATION KINETICS IN SOLUTION TO THE DETERMINATION OF THE FRACTAL DIMENSION IN AEROGELS 211

F. Devreux, J.P. B o i l o t , F. Chaput, and A. Lecomte

LOW WAVENUMBER RAMAN SCATTERING IN SILICA AND SILICOPHOSPHATE AEROGELS 217

Barbara L. Waiden, Else B r e v a l , and W i l l i a m B. White

BASE-CATALYZED SILICA GELS: STRUCTURE AND CHEMISTRY 223 Garry J. Garvey and Bruce E. Smith

SOLUTION CHEMISTRY IN THE A l ? 0 3 - S i 0 2 SYSTEM 229 W.G. Fahrenholtz, S.L. H i e t a l a , D.M. Smith, A.J. Hurd, C.J. B r i n k e r , and W.L. E a r l

*IN-SITU PORE STRUCTURE ANALYSIS DURING AGING AND DRYING OF GELS 23 5

Douglas M. Smith, Pamela J. Davis, and C. J e f f r e y B r i n k e r

RELATIONSHIP BETWEEN STRAINED SILICON-OXYGEN BONDS AND RADIATION INDUCED PARAMAGNETIC POINT DEFECTS IN SILICON DIOXIDE 247

W.L. Warren, P.M. Lenahan, C.J. B r i n k e r , and C.S. Ashley

MOLECULAR ORBITAL MODELING OF WATER ADSORPTION ON A TETRASILOXANE RING 255

J.K. West and S. Wallace

PART V: POSTER SESSION: SOLUTION CHEMISTRY, PROCESSING SCIENCE, ELECTRICAL AND OPTICAL PROPERTIES,

THIN FILMS AND FIBERS

CATALYTIC CONTROL OF S i 0 2 SOL-GEL KINETICS - A MECHANISTIC STUDY OF BASES 263

Jorge Sanchez, Mary Reese, and Alon McCormick ORGANIC CATALYSTS IN THE SILICA SOL-GEL SYSTEM 269

T.A. G a l l o , B.L. Simms, and V.T. B r i c e

THE INFLUENCE OF CATIONS ON GROWTH KINETICS OF SILICA AGGREGATES 27 3

Theo P.M. Beelen, Peter W.J.G. Wijnen, Kees P.J. Rummens, and Rutger A. van Santen

SOLVENT SELECTION AND THE CONTROL OF SOL-GEL REACTIONS 277 K. Jones, J.M. Boulton, and H.G. Emblem

INVESTIGATION OF THE SILICA NETWORK DURING THE SOL TO GEL TRANSITION AND FINAL XEROGEL PROPERTIES 283

Paul R. Soskey, Randall E. N i k l e s , George F. Fattman, Robert M. M i n i n n i , and Deborah A. Gerenza

• I n v i t e d Paper

vii

FORMATION OF SPINEL IRON OXIDE IN SOLUTION Jean P i e r r e J o l i v e t , E l i s a b e t h Tronc, P h i l i p p e B e l l e v i l l e , and Jacques Livage

RELIABLE ELECTROKINETIC CHARACTERIZATION PROCEDURES FOR CERAMIC POWDERS

Jiun-Fang Wang, Richard E. Riman, and Dan i e l J. S h a n e f i e l d

FRACTAL CONCEPTS AND AGGREGATION OF IRON OXIDES R. Amal, J.A. Raper, and T.D. Waite

S.A.N.S. STUDY OF FRACTAL ALUMINO-SILICATE AEROGELS F. Chaput, J.P. B o i l o t , A. Dauger, F. Devreux, and A. de Geyer

CHARACTERIZATION OF PARTIALLY CONDENSED SILICA FORMED FROM THE PARTIAL HYDROLYSIS OF TMOS

T.M. T i l l o t s o n and L.W. Hrubesh

CHARACTERIZATION OF ULTRALOW-DENSITY SILICA AEROGELS MADE FROM A CONDENSED SILICA PRECURSOR

Lawrence W. Hrubesh, Thomas M. T i l l o t s o n , and John F. Poco

MICROSTRUCTURAL DEPENDENCE OF AEROGEL MECHANICAL PROPERTIES

J.D. LeMay, T.M. T i l l o t s o n , L.W. Hrubesh, and R.W. Pekala

POSITRONIUM DECAY IN SILICA SOL-GELS B. Hopkins, C.A. Quarles, and T.W. Zerda

A COMPARISON OF TiOj-SiO^ AEROGELS AND XEROGELS G. C o g l i a t i , M. G u g l i e l m i , T.M. Che, and T.J. Cl a r k

THE EFFECTS OF HYDROLYSIS CONDITIONS, AND ACID AND BASE ADDITIONS, ON THE GEL-TO-CERAMIC CONVERSION IN SOL-GEL DERIVED PbTi0 3

Robert W. Schwartz, C.D.E. Lakeman, and D.A. Payne

EFFECTS OF TRIOXANE ON SILICA GEL Xiaoming L i and P.F. Johnson

EFFECT OF DOPANTS ON THE CRYSTALLIZATION OF ZIRCON FROM ZIRCONIUM SILICATE GELS

J.D. B a r r i e and M.J. Meshishnek

EFFECT OF Sn0 2 ON THE MECHANICAL PROPERTIES OF Si0 2/Sn0 2 GEL-DERIVED COMPOSITES

R. Dal Maschio, S. D i r e ' , R. Campostrini, G.D. Soraru, and G. Carturan

CRYSTALLIZATION AND PHASE TRANSFORMATION OF Z r 0 2 - S i 0 2

GELS Xiaoming L i and P.F. Johnson

viii

PREPARATION OF THE POROUS SUPPORTS WITH Si0 2-Zr0 2-Na 20 COMPOSITION

Y. T s u r i t a and K. Wada

STUDIES IN THE Ba-Ca-Al-0 SYSTEM CHEMICAL MODIFICATION OF ALUMINUM ALKOXIDE BY PROPIONIC ACID

V. Hebert, S. V i l m i n o t , and D. B r i o n

SOL-GEL SYNTHESIS OF THIN FILMS FOR USE AS PLANAR WAVEGUIDES

G.W. Dale, H.H. Fox, B r i a n J.J. Z e l i n s k i , and Laura Weller-Brophy

PROCESSING OF S i 0 2 ~ T i 0 2 THIN FILM WAVEGUIDES L. Weisenbach, T.L. Davis, B.J.J. Z e l i n s k i , R.L. Roncone, and L.A. Weller-Brophy

OPTICAL INTERFERENCE FILTERS BY SOL-GEL PROCESSING J.L. Keddie and E.P. G i a n n e l i s

ΤΙΤΑΝΙΑ/SILICA SOL-GEL FILMS: COMPARISON OF TECHNIQUES FOR THIN FILM THICKNESS MEASUREMENT

S.M. Melpolder, A.W. West, M.P. Cunningham, and R. Sharma

HETEROMETALLIC ALKOXIDES AS PRECURSORS TO MULTICOMPONENT OXIDES

L i l i a n e G. H u b e r t - P f a l z g r a f , Renee P a p i e r n i k , M a r i e - C e c i l e Massiani, and Bernard Septe

STABILIZATION, CHARACTERIZATION AND OPTICAL APPLICATIONS OF NIOBIUM AND TANTALUM OXIDE SOLS PREPARED VIA ALKOXIDE ROUTES

Stephen Parraud, L i l i a n e G. H u b e r t - P f a l z g r a f , and Herve Floch

MICROWAVE PROCESSING OF SOL-GEL DERIVED POTASSIUM NIOBATE

Z. F a t h i , I . Ahmad, and D.E. Cla r k DIELECTRIC CHARACTERIZATION OF POLYCERAM FILMS

G. Teowee, J.M. Boulton, H.H. Fox, A. Koussa, T. Gudgel, and D.R. Uhlmann

SOL-GEL THIN FILM ELECTRONIC PROPERTIES W.L. Warren, P.M. Lenahan, C.J. B r i n k e r , G. R. S h a f f e r , CS. Ashley, and S.T. Reed

SOL-GEL SYNTHESIS OF LEAD TITANATE FIBRES FOR USE IN THE FABRICATION OF PIEZOCERAMIC-POLYMER COMPOSITES

H. Janusson, C.E. M i l l a r , and S.J. Mi l n e

MICROSTRUCTURAL EVOLUTION OF TiO ? SOL-GEL THIN FILMS J.L. Keddie and E.P. G i a n n e l i s

ELECTRON DIFFRACTION ANALYSIS OF THE STRUCTURE OF S i 0 2 GEL-FILM

H i s a s h i Ohsaki, Michel A. Aegerter, and Takaki S h i c h i r i

ix

PROPERTIES OF FILMS PREPARED FROM LOW SURFACE AREA/ DENSITY ALUMINA-SILICA 43 3

S.L. H i e t a l a , D.M. Smith, V.M. H i e t a l a , G.C. Frye, A.J. Hurd, and C.J. B r i n k e r

THIN ANISOTROPIC COATINGS BASED ON SOL-GEL TECHNOLOGY 439 S. Randall Holmes-Farley and Lynn C. Yanyo

PARTICLE GROWTH AND DEVELOPMENT DURING THE IN-SITU PRECIPITATION OF SILICA IN A POLYMERIC MATRIX 445

Ping Xu, Shuhong Wang, and James E. Mark

SOL-GEL DEPOSITION OF ELECTRONIC CERAMIC FILMS 453 J.M. B e l l , B. Ben-Nissan, M. Anast, B.O. West, L. S p i c c i a , J. C u l l e n , I . Watkins, D. d e V i l l i e r s , and G. Johnston

THE FORMATION OF THIN FILMS AND FIBERS OF TiC FROM A POLYMERIC TITANATE PRECURSOR 457

S-J. T i n g , C-J. Chu, E. L i m a t t a , J.D. Mackenzie, T. Getman, and M.F. Hawthorne

CERAMIC FIBER COATING BY A NON-AQUEOUS SOL-GEL PROCESS 461 F.C. Montgomery, H.H. S t r e c k e r t , R.O. H a r r i n g t o n , J.L. Kaae, S.P. Paguio, and D.R. Wall

IMPROVEMENT OF BUILDING MATERIALS PERFORMANCE BY SOL-GEL DERIVED COATINGS 4 67

Wolfram Beier and Ivan Odler

GLASSES AND MULTI-COMPONENT SOL-GELS FOR USE AS HIGH-TEMPERATURE PROTECTIVE COATINGS 473

L a u r i J. DeVore and Nora R. Osborne CHARACTERIZATION OF CERIA STABILIZED ZIRCONIA COATINGS ON METAL SUBSTRATES 481

Rosa Di Maggio, Paolo S c a r d i , and Andrea Tomasi

SOL-GEL PROCESSING OF PbTi0 3 FIBERS 485 S.I. A o k i , S.C. Choi, D.A. Payne, and H. Yanagida

EVOLUTION OF SURFACE AREA DURING THE CONTROLLED GROWTH OF SILICA SPHERES 491

Gregory H. Bogush, C.J. B r i n k e r , P.D. Majors, and D.M. Smith

PART V I : PROCESSING SCIENCE I I I : DRYING, DENSIFICATION AND CRYSTALLIZATION

THE CRACKING OF SOL-GEL FILMS DURING DRYING 497 Terry J. Garino

•EFFECT OF INCLUSIONS ON SHRINKAGE 503 George W. Scherer

• I n v i t e d Paper

χ

•HYBRID GELS DESIGNED FOR MULLITE NUCLEATION AND CRYSTALLIZATION CONTROL

J e f f r e y C. H u l i n g and Gary L. Messing 515

MOLECULARLY MODIFIED ALKOXIDE PRECURSORS FOR SYNTHESIS OF DIELECTRIC CERAMICS 527

Pradeep P. Phule and Farida K h a i r u l l a

EFFECT OF PRECURSORS ON LITHIUM INFILTRATED SILICA GELS STUDIED BY XPS 53 3

S.F. Ho and L.C. K l e i n PHASE TRANSFORMATIONS IN Z r 0 2 ~ S i 0 2 GELS 541

J. Campaniello, E.M. Rabmovich, P. B e r t h e t , A. Revcolevschi, and Nonna A. Kopylov

CRYSTALLIZATION OF IN-SITU SiC-MULLITE COMPOSITES FROM MULTICOMPONENT ALUMINA-SILICA GELS 547

S. Jagota and A. P a r v i z i - M a j i d i

PART V I I : THIN FILMS AND FIBERS •RHEOLOGY FOR BETTER SOL-GEL FIBER AND FILM FORMATION 555

C.W. Macosko, M.L. Mecartney, and L.E. Scr i v e n THE PROCESS OF GEL FIBER FORMATION 569

N. Taneda, T. Kawaguchi, D. A r a i , and Κ. Matsuzaki

•SOL-GEL FILM FORMATION BY DIP COATING 575 Alan J. Hurd and C. J e f f r e y B r i n k e r

•SOL-GEL COATINGS ON ACOUSTIC WAVE DEVICES: THIN FILM CHARACTERIZATION AND CHEMICAL SENSOR DEVELOPMENT 583

Gregory C. Frye, C. J e f f r e y B r i n k e r , A n t o n i o J. Ricco, Stephen J. M a r t i n , J a n i c e H i l l i a r d , and Daniel H. Doughty

•OXOMETALATE-GLASS COMPOSITES AND THIN FILMS 595 K a r i n M o l l e r , Thomas Bein, and C. J e f f r e y B r i n k e r

INHOMOGENEITIES IN SOL-GEL COATINGS 605 B.D. Fabes, D.L. K l e i n , and L.J. Raymond

DENSIFICATION AND CRYSTALLIZATION OF THIN TRANSITION METAL OXIDE COATINGS FROM METAL ALKOXIDES 611

Η. Hirashima, R. Muratake, T. Yamashita, and T. Chiba

PART V I I I : CERAMIC PROCESSING OF NATURAL SYSTEMS •BIOMIMETIC CERAMICS 619

Paul C a l v e r t •BIOMIMETIC PROCESSING OF CERAMICS AND CERAMIC-METAL COMPOSITES 625

M. Yasrebi, G.H. Kim, K.E. Gunnison, D.L. M i l i u s , M. Sarikaya, and I.A. Aksay

• I n v i t e d Paper

xi

•SYNTHESIS OF NANOCERAMIC PARTICLES BY INTRAVESICULAR PRECIPITATION

Suhas Bhandarkar, Iskandar Yaacob, and A r i j i t Bose

PART IX: STRUCTURE/PROPERTIES I : ELECTRICAL

*WET CHEMICAL DERIVED FILMS FOR ELECTRICAL APPLICATIONS D. R. Uhlmann, G. Teowee, J.M. Boulton, and B.J.J. Z e l i n s k i

CRYSTALLIZATION KINETICS OF METALLO-ORGANICS DERIVED PZT THIN FILM

K.C. Chen and J.D. Mackenzie EVOLUTION OF MOLECULAR STRUCTURE IN ALKOXIDE-DERIVED LITHIUM NIOBATE

Dennis J. E i c h o r s t and D.A. Payne

PREPARATION OF SINGLE-PHASE KNb03 USING BIMETALLIC ALKOXIDES

Mostafa M. Amini and Michael D. Sacks

•INTERCALATION CHEMISTRY: A NOVEL APPROACH TO MATERIALS DESIGN

E. P. G i a n n e l i s , V. Mehrotra, and M.W. R u s s e l l

PREPARATION OF COPPER AND COPPER-BARIUM-YTTRIUM SOLS FROM METAL 2-(2-ETHOXYETHOXY)ETHOXIDES AND CONVERSION OF COPPER-BARIUM-YTTRIUM ALKOXIDE PRECURSORS TO Ba 2YCu 30 7_ 6

Mary Rose Scozzafava, Wendell E. Rhine, and Michael J. Cima

ION-IMPLANTATION EFFECTS ON SPIN-ON-GLASS (SOL-GEL) S i 0 2 FILMS

Y. Shacham-Diamand, N. Moriya, and R. K a l i s h

CHEMICAL SYNTHESIS OF ALUMINUM NITRIDE POWDERS P h i l l i p R. Coffman, W i l l i a m T. Petuskey, and Sandwip K. Dey

PART X: STRUCTURE/PROPERTIES I I : OPTICAL

•GRIN ROD OF LARGE DIAMETER AND LARGE DELTA-N Masayuki Yamane, Atsuo Yasumori, Mitsunobu I w a s a k i , and Kazutaka Hayashi

STUDIES ON THE REPRODUCIBLE PRODUCTION OF GRIN (GRADIENT INDEX) GLASS RODS BY A SOL-GEL PROCESS

J. B r i a n C a l d w e l l , Tessie M. Che, Richard W. Cruse, Robert M. M i n i n n i , Randall E. N i k l e s , V i c t o r N. Warden, and Mark A. Banash

• I n v i t e d Paper

xii

LIGHT HARVESTING MOLECULAR ASSEMBLIES IN THE DESIGN OF HIGHLY LUMINESCENT SOL-GEL DERIVED GLASSES 733

J o e l I . Dulebohn, B e a t r i c e Van V l i e r b e r g e , K r i s A. Berglund, Ronald B. Lessard, Jeong-a Yu, and D a n i e l G. Nocera

*SOL-GEL PROCESSED INORGANIC AND ORGANICALLY MODIFIED COMPOSITES FOR NONLINEAR OPTICS AND PHOTONICS 741

Paras N. Prasad INCORPORATION OF POLYANILINE INTO A SILICA GEL VIA THE SOL-GEL TECHNIQUE 747

F. N i s h i d a , B. Dunn, E.T. Knobbe, P.D. Fuqua, R.B. Kaner, and B.R. Mattes

OPTICAL SWITCHES BASED ON VANADIUM DIOXIDE FILMS GROWN BY THE SOL-GEL PROCESS 753

Rich a r d S. Potember and Kenneth R. Speck

VANADIUM PENTOXIDE GELS: STRUCTURAL DEVELOPMENT AND RHEOLOGICAL PROPERTIES 759

J.K. B a i l e y , T. Nagase, G.A. Pozarnsky, and M.L. Mecartney

PART X I : POSTER SESSION: NOVEL PROCESSING, SUPERCONDUCTORS PREPARATION OF PHENYLSILOXANE FILMS VIA SOLUTION DEPOSITION TECHNIQUES 767

E.W. Burkhardt, R.R. B u r f o r d , and J.H. Deatcher

SYNTHESIS AND STRUCTURAL CHARACTERISTICS OF POLYCERAMS 773

J.M. Boulton, H.H. Fox, G.F. N e i l s o n , and D.R. Uhlmann

POLYMERIZATIONS OF ALKENYLSILANES USING EARLY TRANSITION METAL CATALYSTS 779

John Masnovi, X i n Y. Bu, Paula Conroy, A. Harry A n d r i s t , Frances I . H u r w i t z , and Doug M i l l e r

HIGH RESOLUTION TEM OF ORGANIC AEROGELS AND INORGANIC AEROGELS 785

George C. Ruben and Richard W. Pekala

A NEW SYNTHETIC ROUTE TO ORGANIC AEROGELS 791 R.W. Pekala and C.T. A l v i s o

CRYSTALLIZATION OF PYROLYZED POLYSILAZANES 797 Roger L.K. Matsumoto

PRE-RESONANCE RAMAN CHARACTERIZATION OF METAL-ORGANIC FILMS FROM TITANIUM ALKOXIDE CARBOXYLATE COMPLEXES 801

Charles D. G a g l i a r d i , Dilum Dunuwila, and K r i s A. Berglund

• I n v i t e d Paper

xiii

STABILITY OF BORON NITRIDE COATINGS ON CERAMIC SUBSTRATES

Abhaya K. Datye, Xiaomei Qui, Theodore T. Borek, Robert T. Paine, and Lawrence F. A l l a r d

807

XPS CHARACTERIZATION OF MIXED CARBIDES OBTAINED FROM POLYMER PRECURSORS

Gaetano Granozzi, A n t o n e l l a G l i s e n t i , and Gian D. Soraru

811

MIXED CARBIDES VIA POLYMER ROUTE Gian D. Soraru, Florence Babonneau, and John D. Mackenzie

815

LASER DENSIFICATION MODELING 819 Taipau Chia, L.L. Hench, Chaobin Qin, and C.K. Hsieh

THE USE OF SOLUBLE METAL-POLYSELENIDE COMPLEXES AS PRECURSORS TO BINARY AND TERNARY SOLID METAL SELENIDES 825

S. Dhingra and M.G. K a n a t z i d i s CHEMICALLY DERIVED YTTRIA-STABILIZED ZIRCONIA FOR PLASMA-SPRAYING 831

Fawzy G. S h e r i f and H. Herman EMULSION PRECIPITATION AND CHARACTERIZATION OF ZIRCONIA 837

L i e h - J i u n Shyu and Frank M. Cambria TRANSPIRATION COOLED POROUS TYPE V I SILICA ROCKET WINDOWS 843

A l b e r t G. Fosmoe I I and L a r r y L. Hench

PLASMA SYNTHESIS OF FINE CERAMIC POWDERS BY A NOVEL COUNTER-FLOW LIQUID INJECTION METHOD 849

P. Kong, T.W. Or, L. Stachowicz, and E. Pfender

MORPHOLOGY CONTROL IN PRECURSOR CERAMIC POWDER PRODUCTION BY THE ELECTRICAL DISPERSION REACTOR 853

Michael T. H a r r i s , Timothy C. S c o t t , Osman A. Basaran, and Charles H. Byers

DC PLASMA SYNTHESIS OF ALUMINUM NITRIDE CERAMIC POWDERS 857 Z.P. Lu and E. Pfender

EFFECT OF NITROUS OXIDE GAS ON CVD DIAMOND FILM DEPOSITION 861

H. Koinuma, M. Yoshimoto, Y. Takagi, A.B. Sawaoka, T. Hashimoto, T. Nagai, and T. S h i r a i s h i

SUPERCONDUCTING FIBERS FROM ANHYDROUS METAL CARBOXYLATES 8 65

Richard M. Laine, Kay A. Youngdahl, Richard A. Kennish, M a r t i n L. Hoppe, Zhi-Fan Zhang, and D. Jean Ray

FABRICATION OF SUPERCONDUCTING Bi-Sr-Ca-Cu-0 OXIDE FILMS USING THE METAL ALKOXIDE METHOD 87 3

Shingo Katayama and Masahiro Sekine

xiv

POLYFUNCTIONAL CARBOXYLIC ACIDS AS COPRECIPITATING AGENTS FOR BARIUM, YTTRIUM, AND COPPER 877

Robert B. H a l l o c k , P.O. Rexer, M.S. J o l l y , W.E. Rhine, and M.J. Cima

SYNTHESIS OF SUPERCONDUCTING THIN FILMS BY ORGANOMETALLIC DECOMPOSITION 883

Christophe Barbe and T e r r y A. Ring CHEMICAL PREPARATION OF SUPERCONDUCTING OXIDES USING CONVENTIONAL CHELATING AGENTS 889

C y r i l Chiang and C.Y. Shei SYNTHESIS OF SUPERCONDUCTING PEROVSKITE BY COPRECIPITATION OF HYDROXIDES 893

I . Valente-Campion, P. Barboux, L. Mazero l l e s , D. M i c h e l , R. Morineau, and J. Livage

SUPERCONDUCTING YBa 2Cu 30 7_ x FIBERS FABRICATED BY THE SOL-GEL METHOD USING METAL ALKOXIDES 897

Shingo Katayama and Masahiro Sekine

SOL-GEL PROCESSING OF THE Tl 2Ca 1Ba 2Cu 20 8 + x HIGH Tc SUPERCONDUCTING PHASE 901

M.R. Teepe, D.S. Kenzer, G.A. Moore, and G. Kordas

PREPARATION OF SUPERCONDUCTING YBa 2Cu 30 ?_ x COMPOUNDS BY WATER EXTRACTION VARIANT OF SOL-GEL PROCESS 907

A. Deptu^a, W. £ada, T. Olczak, T. Z d j t o w s k i , and A. Di Bartolomeo

METALLO-ORGANICS DERIVED TRACTABLE RESINS FOR YBCO SUPERCONDUCTING FIBER FABRICATION 913

K.C. Chen, A.Y. Chen, and K.S. Mazdiyasni

PREPARATION OF Bi-Pb-Sr-Ca-Cu-0 SUPERCONDUCTOR BY THERMAL DECOMPOSITION OF AN EDTA COLLOID 917

H.S. Koo, C.K. Chiang, Y.T. Huang, and G.C. Tu

SOLUBLE AND VOLATILE PRECURSORS FOR THE PREPARATION OF SUPERCONDUCTING FILMS 921

Nancy N. Sauer, Eduardo Garcia, and Robert R. Ryan KINETIC STUDY OF HIGH Tc Bi-Pb-Sr-Ca-Cu-0 SYSTEM 925

W.-M. Hurng, Y.T. Huang, C.Y. Shei, C. Chiang, H.S. Koo, S.F. Wu, and P.T. Wu

SOLUTION-DERIVED YBa 2Cu 30 7_ f i THIN FILMS AND BARRIER LAYERS " 929

G.E. W h i t w e l l , J.H. Wandass, F.M. Cambria, and M.F. Antezzo

PREPARATION, THERMAL PROCESSING BEHAVIOR AND CHARACTERIZATION OF POWDERED AND BULK YBa 2Cu 30 ?_ x

FROM FREEZE DRIED NITRATE SOLUTIONS " 935 N. Coppa, A. Bura, J.W. Schwegler, R.E. Salomon, G.H. Myer, and J.E. Crow

xv

TEN MINUTE PREPARATION OF YBa 2Cu 30 7_ x USING BARIUM HYDROXIDE

Ν. Coppa, Α. Kebede, J.W. Schwegler, I . Perez, R.E. Salomon, G.H. Myer, and J.E. Crow

EVALUATION OF YBa 2Cu 30 7_ 5 SOL-GEL DERIVED FILMS ON SAPPHIRE SUBSTRATES PRODUCED FROM DIFFERENT C u ( I I ) ALKOXIDE GROUPS

D.S. Kenzer, M.R. Teepe, G.A. Moore, and G. Kordas CHARACTERIZATION OF AMORPHOUS GEL TO SUPERCONDUCTING OXIDE CONVERSION FOR SOL-GEL PRODUCED Y 1Ba 2Cu 30 7_ x

G.A. Moore, D. Kenzer, M. Teepe, and G. Kordas

PART X I I : NOVEL PROCESSING I •ASPECTS OF CHEMISTRY AND CHEMICAL PROCESSING OF ORGANICALLY MODIFIED CERAMICS

Helmut K. Schmidt ARYL-BRIDGED POLYSILSESQUIOXANES - NEW MICROPOROUS MATERIALS

Kenneth J. Shea, Owen Webster, and Douglas A. Loy RUBBERY ORMOSILS

Young J. Chung, Su-Jen Ting, and John D. Mackenzie NON-LINEAR ORGANIC DYES IN POLYCERAM HOSTS

J.M. Boulton, J. Thompson, H.H. Fox, I . Gorodisher, G. Teowee, P.D. C a l v e r t , and D.R. Uhlmann

INORGANIC-ORGANIC COMPOSITES (ORMOCERs) AS STRUCTURED LAYERS FOR MICROELECTRONICS

Michael P o p a l l , Henning Meyer, Helmut Schmidt, and Jochen Schulz

RAPID THERMAL PROCESSING OF HIGH TEMPERATURE SUPERCONDUCTING FIBER

J.W. H a l l o r a n , M.J. Neal, D.S. Ginle y , E.L. V e n t u r i n i , J.F. Kwak, R.J. Baughman, M.A. M i t c h e l l , B. Morosin, S.N. Basu, and T.E. M i t c h e l l

PREPARATION OF POROUS OXIDE BEADS USING POLYMERIC BEADS TO CONTROL BEAD SIZE AND SHAPE

Anne B. Hardy, Wendell E. Rhine, and H. Kent Bowen

PART X I I I : NOVEL PROCESSING I I *NEW CHEMICAL ROUTES TO METAL NITRIDES

Wayne L. G l a d f e l t e r , Jen-Wei Hwang, John F. Evans, S c o t t A. Hanson, Klavs F. Jensen, and Kwok-Lun Ho

* I n v i t e d Paper

xvi

BORON NITRIDE AND COMPOSITE AEROGELS FROM BORAZINE BASED POLYMERS

David A. L i n d q u i s t , Douglas M. Smith, Abhaya K. Datye, Gregory P. Johnston, Theodore T. Borek, R i l e y Schaeffer, and Robert T. Paine

SPECTROSCOPIC CHARACTERIZATION OF A PRE-CERAMIC POLYMER FOR SiC/TiC SYSTEM

Florence Babonneau, P a t r i c e Barre, Jacques Livage, and M i c h e l Verdaguer

CHEMICAL REACTIONS DURING THE THERMAL PROCESSING OF BORAZENE POLYMERS

R.R. Rye, T.T. Borek, D.A. L i n d q u i s t , and R.T. Paine

LASER DENSIFICATION OF SOL-GEL COATINGS D.J. T a y l o r , B.D. Fabes, and M.G. S t e i n t h a l

*ELECTRODEPOSITION OF NANOMODULATED CERAMIC THIN FILMS Jay A. Sw i t z e r , Michael J. Shane, and Ric h a r d J. P h i l l i p s

*THE CHEMICAL PROCESSING OF SILICATES FOR BIOLOGICAL APPLICATIONS - A REVIEW

L.L. Hench and June Wilson

PART XIV: LATE PAPERS ACCEPTED

MAGNETIC RESONANCE AS A STRUCTURAL PROBE OF A URANIUM (VI) SOL-GEL PROCESS

Charles M. King, R. Bruce King, A. Ronald Garber, Major C. Thompson, and Bruce R. Buchanan

OXYGEN-17 NMR STUDIES OF URANIUM (VI) HYDROLYSIS AND GELATION

R. Bruce King, Charles M. King, and A. Ronald Garber

•MECHANICAL PROPERTIES OF SILICA ALCOGELS AND AEROGELS T. Woignier, J. Phalippou, H. Hdach, and G.W. Scherer

AUTHOR INDEX

SUBJECT INDEX

MATERIALS RESEARCH SOCIETY SYMPOSIUM PROCEEDINGS

• I n v i t e d Paper

xvii

595

OXOMETALATE-GLASS COMPOSITES AND THIN FILMS

Kar in Mol ler* , T h o m a s Bein* and C. Jef f rey Br inker** ' D e p a r t m e n t of Chemist ry and Center for Micro-Engineered Ceramics , Universi ty of New Mexico, A lbuquerque, N M 87131 **Sandia Nat ional Laborator ies, P. 0 . Box 5800, A lbuquerque, N M 87185

ABSTRACT

New g lass-compos i tes wi th ion exchange propert ies have been deve loped . A m m o n i u m 1 2 - m o l y b d o p h o s p h a t e (AMP) (ΝΗ4)3ΡΜοΐ2θ4ο, and a m m o n i u m 12-t u n g s t o p h o s p h a t e ( A W P ) ( N h U ^ P W i 2 O 4 0 , k n o w n for the i r ion e x c h a n g e capabi l i t ies, are inc luded either in pre formed aerogels with def ined pore s ize, or are added to sol-gel mix tures dur ing the process of gel fo rmat ion . Character izat ion is carr ied out by FTIR, Raman and EXAFS spectroscopy. Ion exchange capacit ies for the oxometa la te precursors are de te rmined for silver and rubidium and are compared to those of the glass composi tes. Glass composi tes show high ion exchange capacity, but some port ion of the metalate complexes leaches f rom the g lass dur ing the procedure. This is in contrast to thin composi te f i lms, which have almost no porosity and do not s h o w loss of meta la te . E X A F S spec t roscopy demos t ra tes that the oxometa la te micros t ruc ture is ma in ta ined in g lass compos i tes a n d that rub id ium ions after ion exchange in glasses occupy similar cation posit ions as in the precursor compounds .

INTRODUCTION

The combinat ion of di f ferent funct ional propert ies in g lass-based composi tes of fers great potent ial for the des ign of tai lored mater ia ls. Examples include sol-gel der ived g lass-organic composi tes , g lass- inc luded laser dyes, catalysts, and nonl inear opt ica l mater ia ls .

In v iew of the increasing d e m a n d for s table, ion-select ive sensors we have in i t iated a p r o g r a m a imed at the des ign of ta i lored thin f i lms wi th se lect ive ion exchange capabi l i t ies . In combina t ion wi th highly sensi t ive acoust ic dev ices , it is env is ioned that inexpens ive , rugged ion sensors for p rocess and env i ronmenta l mon i to r ing c a n be d e s i g n e d . The concept is b a s e d upon the encapsu la t ion of oxometa la te c lus ters in porous , sol -gel der ived g lasses . The resul t ing mater ia ls c o m b i n e se lect ive ion e x c h a n g e s i tes wi th ta i lored poros i ty , such that u l t imately large f ract ions of unwanted spec ies (e.g. , o rgan ics , b io logical matter) are screened from the ion exchange sites. The fol lowing benefi ts are expected f rom this approach: The des ign of ion exchange composites a l lows independent ad justment of both ion select iv i ty th rough the cho ice of d i f ferent oxometa la tes , a n d porosi ty th rough the c h o i c e of so l -ge l c h e m i s t r y . F u r t h e r m o r e , the resu l t ing ino rgan ic f i lms are temperature stable up to at least 3 0 0 ° C and not subject to foul ing.

Heteropoly oxometa la tes such as anions with the Keggin structure are known s ince the last cen tu ry , but their c rys ta l s t ruc ture w a s first so lved by Kegg in in 1934. Figure 1 depicts the Keggin anion structure and a defect structure wi th one M 0 6 oc tahedron miss ing. These mater ials f ind numerous appl icat ions in catalysis, analyt ical chemis t ry and b iochemica l or medica l a reas . Thei r abil i ty to exchange their counter cat ion for alkali ions was first recognized by Smi t 1 and has since been used in co lumn chromatography and in paper chromatography. Keggin ions have been used to exchange alkali cat ions as well as radioactive pol lutants. General reviews are a v a i l a b l e . 2 - 3 · 4 » 5

Mat. Res. Soc. Symp. Proc. Vol. 180. ©1990 Materials Research Society

596

Figure 1: Ideal ized Keggin structure XM12 (a) and defect Keggin structure X M n (b). The central XO4 te t rahedron is not shown . O a = oxygen shared by 3 ΜΟβ and the central XO4 tetrahedron, Ob and O c * oxygen shared by corner and edge linked ΜΟβ. 0<j = terminal unshared oxygen

Th is c o m m u n i c a t i o n repor ts on the des ign of 1 2 - m o l y b d o p h o s p h a t e and 12-tungstophosphate ions encapsula ted in si l icate g lass bodies in bulk fo rm. FTIR, FT-Raman , EXAFS, and ion exchange data demonst ra te the feasibi l i ty of creat ing intact intra-glass oxometa la te ions that are accessib le for ion exchange th rough the pore system of the matr ix.

EXPERIMENTAL:

1. Sample Preparation

a) A m m o n i u m 12-mo lvbdophosphate (AMP) ( N H 4 ) 3 P M o i 2 0 4 o . Highest yield (82 -9 5 % after work -up) is ob ta ined by s tepwise comb in ing s to ich iometr ic a m o u n t s of N a 2 M o 0 4 , H 3 P O 4 , and N H 4 N O 3 (in 0.1 Μ HNO3) under ac id condi t ions. 1 molar aqueous solut ions were added in a vo lume ratio 12:1:3 after acidi fy ing the sod ium mo lybda te so lu t ion wi th 13 Μ H N O 3 to pH 1.6. The sl ightly ye l low color of the mo lybda te tu rned to s t rong ye l low immedia te ly after addi t ion of phosphor i c ac id . Precipi tat ion of the a m m o n i u m salt occured prompt ly.

b) A m m o n i u m 12-phosphotungsta te (AWP) ( N H 4 ) 3 P W 1 2 0 4 o . Sod ium tungstate is insoluble in ac id solut ions and forms a thick whi te precip i tate w h e n acid i f ied with H N O 3 . T h u s , 10 ml W O 4 2 - and 0.9 ml 1 Μ N a O H and 0.9 ml of 1 Μ H 3 P O 4 are comb ined , fo l lowed by addit ion of 2.5 ml ΝΗ4ΝΟ3 at pH 7 and acidif ication to pH 1.5. A W P precip i tates as a whi te sol id (yield 92%) . The cor responding whi te silver salt is prepared by adding A g N 0 3 before acidif ication (Yield 5 0 % ) .

c) Assembly of A M P within pores of aerogels . To a slurry of 1g TEOS-der ived B2-Aerogel (pore size 10-500 A) in 10 ml H2O, 4 ml of 1 Μ N a 2 M o 0 4 and 2 ml of 13 Μ Η Ν 0 3 are added . The slurry is st irred for 10 minutes before adding 0.33 ml of 1 Μ H 3 P O 4 , a n d finally, 1 ml of 1 Μ Ν Η 4 Ν Ο 3 . A green color result ing f rom reduct ion of the A M P was reversed to yel low upon add ing 2 ml 3 0 % H 2 O 2 . After f i l tration the yel low sol id was dr ied at 8 5 ° C .

597

d) Preparat ion of g lasses containing oxometalates

H M P - G l a s s . 3 g of crystal l ine 12-molybdophosphor ic acid (H3PM012O40; HMP) and 7.3 ml E tOH and 1 ml 0.1 Μ HNO3 and 7.3 ml T E O S and 2 ml 0.05 Μ N a O H are c o m b i n e d in this sequence (molar ratio of H M P : S i 0 2 = 1:20). The suspension was sonicated for 3 minutes and left at room temperature. After two days a greenish gel had formed.

A M P - G l a s s . Synthetic A M P + T E O S + EtOH in a molar ratio of A M P : S i 0 2 = 1:20: S to i ch iome t r i c a m o u n t s of 1 Μ N a 2 M o 0 4 (40 ml) a n d 1 Μ H3PO4 (3 .33 ml) solut ions (at pH = 1.5, 6 ml 13 Μ HNO3) were comb ined . Water w a s evaporated at 75 C to about half the vo lume (25 ml) until a yel low c loudiness indicated the start ing point for precipi tat ion. 14.6 ml T E O S were added to the w a r m , clear solut ion under s t rong st i r r ing, and immediate ly sto ichiometr ic amounts of NH4NO3 in ethanol were a d d e d (1.1 g in 1 ml 0.1 Μ HNO3 plus 14.6 ml E tOH) . A c loudy ye l low co lor appeared . Stirr ing was cont inued under slow cool ing of the slurry. A thick paste was fo rmed after 2 hours. After 1 day ethanol w a s part ial ly r e m o v e d by heat ing in a water bath. A hard, yel low glass formed.

2, Characterization

Metal contents of g lasses were determined by atomic absorpt ion. The samples were analyzed as-synthesized and after each subsequent t reatment by FT-IR in the form of KBr pel lets. For FT-Raman exper iments , a Spec t rum SL301 NdrYAG laser (1064 n m , c a . 1.0 W) was focused on a 1-mm capi l lary conta in ing the powdered sample. Light col lect ion w a s done with a modi f ied Mat tson Polar is in ter ferometer , detect ion wi th an InGaAs detector (EPITAXX) . EXAFS measurements were peformed at the X-11A beaml ine at NSLS (Brookhaven National Laborator ies) wi th an electron energy of 2.5 G e V and ring currents be tween 90 and 180 mA. Data were co l lec ted wi th a Si (400) crysta l pair monochromato r at the Mo K-edge (20,000 eV) and at the W L| | | -edge (10 ,207 eV) at c a . 100 K. R u b i d i u m - e x c h a n g e d s a m p l e s were also e x a m i n e d at the Rb Κ edge (15,200 eV) . Data analys is w a s per fo rmed fo l lowing s tandard p r o c e d u r e s . 6

3. Ion exchange

Ion exchange was per formed on bulk oxometalates as well as on glass composi tes by adding stoichiometr ic or excess amounts of A g N 0 3 or R b N 0 3 in acid solut ions (e.g., 500 mg A W P and 50 ml of 0.01 Μ R b N 0 3 in 0.1 Μ HNO3). Samples were st irred for c a . two hours in exchange solut ions, f i l tered and fur ther ana lyzed . Back-exchange capabi l i t ies w e r e e x a m i n e d on bulk oxometa la tes by add ing vary ing amoun ts of NH4NO3 in acid solution.

598

RESULTS AND DISCUSSION

Bulk oxometa la tes

Character ist ic modes of the M - 0 and P -0 vibrat ions appear between 200 and 1100

c m - 1 in the IR and Raman spect ra . The main IR v ibrat ions at 1064, 964, 875, 795

a n d 595 cnr r 1 of the molybdate ions, or, 1 0 8 1 , 990 /982 , 890, 805 and 535 c m " 1

of the tungsta te ions are ass igned as the asymmet r i c P-O, M-Od ( O d - terminal

o x y g e n s ) , a n d M-O-M v ib ra t ions acco rd ing to R o c c h i c c i o l i - D e l t c h e f f . 7 R a m a n

spect ra show mainly the symmetr ic M-Od band around 1000 c m - 1 and a convolut ion

of the symmetr ic P -0 and asymmetr ic M-Od band around 990 c m - 1 .

Inclusion of Keggin ions in pre formed aerogel

The preparat ion of oxometa la tes in pre formed g lasses resul ted in a loading of ca . 8 w t % Mo in B2-aeroge l a n d a ye l low color ind icated fo rmat ion of A M P . The IR spect rum is shown in Figure 2. The sil ica support b locks out a region be tween 1350 a n d ca . 1000 c m * 1 and obscures an even wider range in the IR. However , the main b a n d s of the K e g g i n ions ( 1 0 6 4 , 9 7 0 , 8 7 5 , 7 9 5 c m - 1 ) are sti l l v is ib le as super imposed peaks when compared with the precursor included in the Figure.

tfανα1ength (urn) 7 θ 9 12 15 20

1400 1200 1000 Wavenumbers

800 600

Figure 2 : FTIR spect rum of the preformed aerogel with included ( N H ^ P M o O ^ in compar ison to the precursor

599

W h e n a part of this sample was washed with a smal l amount of water at room tempera tu re , the color c h a n g e d f rom ye l low to whi te a n d no Kegg in ions were detec tab le in the so l id . Heat t reatment in air up to 200 C w a s thought to favour condensat ion react ions be tween the aerogel and the Keggin ions. A similar washing procedure as above still reduced the molybdenum content, but left ca . 5 0 % attached to the so l id . Af ter a s u b s e q u e n t i on -exchange exper imen t w i th s i lver n i t ra te, all remaining mo lybdenum ions were found in the wash solut ion.

Inclusion of Keggin ions during gellation

To avoid or reduce the loss of molybdenum f rom supported samples upon washing, a d i f ferent s t rategy for encapsu la t ion of Kegg in ions w a s d e v e l o p e d : Oxometa la te c o m p l e x e s were synthes ized in the presence of sol-gel precursors for the si l icate matr ix. It was ant ic ipated that bot t leneck pores deve lope which restrict mobil i ty of the Keggin ions but render access for smaller cat ions. Several different g lasses were p r e p a r e d v a r y i n g in the so l -ge l rou te a n d / o r the Kegg in ion p r e s e n t . A representat ive IR spect rum is shown in Figure 3 (AMP in T E O S + EtOH) . The high loading of c a . 38 w t % of Mo al lows for ready detect ion of the Keggin vibrat ions which conf i rm that the Keggin structure is mainta ined in the g lass. The thermal stabil ity of this g lass w a s tes ted by heat ing up to 400 0 C in o x g e n . R a m a n spect ra of a r e p r e s e n t a t i v e e x p e r i m e n t are s h o w n in F igure 4 . It is c lear ly v is ib le tha t decomposi t ion occurs between 200 and 400 0 C. Aging temperatures were therefore restr icted to 200 0 C .

Wove1ongth(urn) 7 7. 5 9 10 11

_ i 1 r—1 1 1 1 1 L i 1 1 1 h 1 Γ

1 1 1.. • ,... J 1 1 I 1 1 1 1 1 L

1400 1300 1200 1100 1000 900 600 Wavanumbar*

Figure 3: FTIR spectra of Ίη -s i t u " formed composi te T E O S + EtOH + (NH4)3PMo04o in compar ison to the precursor (NH4)3PMo04o and H3PM0O40

600

Figure 4 : FT-Raman spect ra of the thermal degradat ion of Ί η - s i t u " fo rmed

composi te T E O S + EtOH + (NhUtePMoCUo. Wavenumbers are given (the

laser line is at 9388 c m - 1 ) . Stokes shifts are as fol lows ( subscr ipts see

Figure 1 9 : ) :

(1) 989 c m * 1 : Mo-Od s y m m e t r i c s t re tch

(2) 879 c m * 1 : M o - O b - M o asymmet r i c s t re tch

(3) 600 c m ' 1 : M o - O c - M o symmet r i c s t re tch

(4) 381 c m * 1 : M o - O - M o bend ing

(5) 250 c m - 1 : M o - O a - M o symmet r i c s t retch

* : N 0 3 -

601

ion exchange

The bulk oxometa la tes were ion exchanged wi th rub id ium a n d si lver by of fer ing s to ich iometr ic amoun ts of the cat ions at room tempera tu re . A M P , A W P and the respect ive si lver salt exchange under these cond i t ions 5 0 % of their ca t ions for rubud ium, whi le A M P and A W P exchanged only 12-15 % of their ammon ium ions for silver. However , a 1 0 0 % exchange is achieved upon offer ing excess of silver nitrate.

W h e n silver salts of the molybdenum and tungsten Keggin ions were exposed to a m m o n i u m ions, back-exchange to the ammon ium form occured for A g M P up to 9 2 % and for A g W P up to 5 4 % in a 3 Μ NH4NO3 solution.

T h e g lass c o m p o s i t e s e x c h a n g e d larger f rac t ions of the i r p r o t o n s or a m m o n i u m cat ions, e.g. , 12 - 7 6 % for Ag and 42 - 9 2 % for Rb. However , some leach ing of the o x o m e t a l a t e s w a s o b s e r v e d for al l d i f fe ren t p o r o u s g l a s s e s . Composi tes made with T E O S showed a loss of 30 - 5 8 % Mo or W, whi le glasses made f rom A2 solut ions (TEOS + EtOH ref luxed at 60 C for several hours) showed a loss f rom 1 6 - 3 5 %. The p re fo rmed aerogel lost up to 9 8 % after two success ive exchange cyc les. The loss of Keggin ions is effect ively suppressed in thin f i lms of simi lar compos i t ions which were found to be non-porous . Mul t icomponent g lasses which retain porosi ty even in thin f i lms are present ly s tud ied.

E X A F S analysis

EXAFS measurements were per formed on the bulk oxometa la tes as well as on glass compos i tes before and after ion exchange. E X A F S al lows to determine the local s t ruc ture a r o u n d the X-ray absorb ing a tom of cho ice and can prov ide de ta i led in format ion about bond d is tances, coordinat ion numbers and types of a toms in the nearest ne ighbor shel ls . Figure 5 shows Fourier t rans fo rmed mo lybdenum EXAFS da ta of the precursors A M P and H M P , over layed wi th the respect ive compos i tes fo rmed with these Keggin ions. A large peak indicating the oxygen environment of the molybdenum atoms is visible between 0.5 and 2 Ä (Bond distances appear at ca . 0.5 Ä to lower bond distances due to phase shift effects). The mean bond distances obtained f rom X-ray di f f ract ion are 1.70 A for the terminal o x y g e n s , 1.92 A for oxygens br idging the mo lybdenum oc tahedra , and 2.43 A for the oxygen l inked to the central phosphorus a tom. The second and third shells ar ise f rom Mo-Mo bonds at 3.42 A f rom edge-shared oc tahedra and at 3.70 A f rom corner -shared oc tahedra . It can clearly be seen that precursor and glass composi tes have the same local structure. A quanti tai tve analysis of these data is in progress.

W h e n a H M P / T E O S composi te is analyzed after rubid ium exchange, the Mo-edge EXAFS da ta do not show any sign of degradat ion (see Figure 6; the imaginary parts of the Fourier t ransformat ions are shown in addit ion to the magni tudes. The former give valuable informat ion about the nature of ne ighbors or over lap of peaks) . The rub id ium edge da ta show a large contr ibut ion a round 2.5 A (uncorrected for phase shift) wh ich indicates a R b - 0 interact ion, whi le the peak around 3.9 A arises f rom the R b - M o b o n d . Th is spec t rum is ident ica l to that taken f rom the bulk rub id ium phospho molybdate and indicates that the rubid ium ions occupy identical cation posit ions in both compounds. When fitted with adequate reference compounds a bond d is tance of ca . 4.4 A can be expected. To our knowledge the only complete determinat ion for cat ion posi t ions in Keggin ions is done wi th combined neutron- and X-ray diffraction by Brown et a l . 8 Their d istance of hydrated protons to molybdenum atoms agrees closely with the above observat ions.

602

Χ10 - 2

9.

8. : \

0 1 2 3 4 5 6 7 8

Χ J Θ - 2

8.

Ä Figure 5: Mo lybdenum EXAFS data : top: Fourier t ransformat ion of the precursor

( Ν Η 4 ) 3 Ρ Μ ο · | 2 θ 4 ο data (solid line) as compared to the aerogel composi te broken ine) . Bo t tom: Fourier t ransformat ion of the precursor H3PM012O40 data (solid line) as compared to the T E O S composi te (broken l i n e )

603

Figure 6: EXAFS data: top: Mo-edge Fourier t ransformation of the composi te T E O S + H3PM012O40 after Rb ion exchange. Bot tom: Rb-edge: corresponding Fourier t ransformat ion of the above composi te

604

This study shows that Keggin ions can be occ luded in glassy substrates with no side products , by either assembl ing the componen ts in the pores of p re- fo rmed g lass, or by in-situ fo rmat ion in precursor ge ls . In porous g lasses , ion exchange simi lar to bulk react ions is observed , and cat ions are shown to be coord inated to the metalate f ramework. These glass composi te offer a potent ial for the design of thin f i lms with ion exchange capabi l i ty.

ACKNOWLEDGMENT

Financial support is grateful ly acknowledged from Sand ia Nat ional Laborator ies ( K. Μ., Τ. B.). A port ion of the work was per formed at Sandia National Laborator ies and suppor ted by the U.S. Departmenty of Energy under contract number DE-AC-04-76DP00789 . The operat ional funds for NSLS beaml ine X-11A are suppor ted by DOE g r a n t D E - A S - 0 5 - 8 0 E R 1 0 7 4 2 .

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