Progress in Nitrogen Ceramics

NATO ASI Series Advanced Science Institutes Series

A Series presenting the results of activities sponsored by the NATO Science Committee, which aims at the dissemination of advanced scientific and technological knowledge, with a view to strengthening links between scientific communities.

The Series is published by an international board of publishers in conjunction with the NATO Scientific Affairs Division

A Life Sciences Plenum Publishing Corporation B Physics London and New York

C Mathematical and D. Reidel Publishing Company Physical Sciences Dordrecht and Boston

D Behavioural and Martinus Nijhoff Publishers Social Sciences BostonlThe Hague/DordrechULancaster

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Series E: Applied Sciences - No. 65

Progress in Nitrogen Ceramics

edited by

F.L. Riley Houldsworth School of Applied Science The University of Leeds Leeds, Yorksh., UK

1983 Martinus Nijhoff Publishers ... A member of the Kluwer Academic Publishers Group ••

Boston I The Hague I Dordrecht I Lancaster .~ Published in cooperation with NATO Scientific Affairs Division

Proceedings of the NATO Advanced Study Institute on Nitrogen Ceramics, University of Sussex, Falmer, UK, July 27 - August 7, 1981

Library of Congress Cataloging in Publication Data

Main entry unaer title:

Progress in nitrogen ceramics.

(NATO ASI series. Series E, Applied sciences no. 65)

Proceedings of the 2nd NATO Advanced Study Institute on Nitrogen Ceramics, University of Sussex, Falmer, U.K., July 27-Aug. 7, 1981.

"Published in cooperation with NATO Scientific Affairs Division."

Includes indexes. 1. Silicon nitride--Congresses. 2. Ceramics-­

Congresses. I. Riley, F. L. II. NATO Advanced Study Institute on Nitrogen Ceramics (2nd : 1981 : University of Sussex) III. North Atlantic Treaty Organization. Scientific Affairs Division. IV. Series: NATO advanced science institutes serie~. Series E, Applied sciences no. 65. TP245.N8P7 1983 666 83-4052

ISBN·13: 978·94·009·6853·0 e·ISBN·13: 978·94·009·6851·6 00/: 10.10071978·94·009·6851·6

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Copyright © 1983 by Martinus Nijhoff Publishers, The Hague

Softcover reprint of the hardcover 1st edition 1983

v

PREFACE

The first NATO Advanced Study Institute on Nitrogen Ceramics held in 1976 at Canterbury came at a particularly significant moment in the development of this subject. The five-year period, 1971-75, had been an especially fruitful one in very many respects for work in the areas of covalent materials in general, and of the nitrides in particular. The Institute was therefore able to cap­ture fully the spirit of excitement and adventure engendered by the outputs of numerous national research programmes, as well as those of many smaller research groups, concerning ceramics potent­ially suitable for applications in a high temperature engineering context. It reflected accurately the state of knowledge with respect to the basic science, the powder technology, and the prop­erties of materials based on silicon nitride and associated syst­ems. The Proceedings of the Institute thus provided a good record for workers already in the field, and a useful textbook for new­comers to the subject of nitrogen ceramics.

The Canterbury Advanced Study Institute had a valuable educ­ational and social function in bringing together for two weeks a large proportion of those workers most closely involved at that time with the nitrogen ceramics. The atmosphere of this meeting, providing both intensive discussions and informal contacts, made a lasting impression on the participants, and inevitably the question was raised of whether, and when, a second Advanced Study Institute might be held on this subject. There was no unique answer to the second of these questions, but an interval of four to five years, in the light of developments, seemed a not unreasonable one, after which a sound case might be made to the Scientific Affairs Division of NATO for necessary financial support. As part of this case, when it was presented in 1980, attention was drawn to the continu­ing expansion of interest in silicon nitride materials, and in particular in the relatively new areas of sintered silicon nitride and sintered reaction bonded silicon nitride, topics which, as the progress chart in the Concluding Remarks section of 'Nitrogen Ceramics' indicates, in 1976 were in their infancy. Work in the area of 'Sialon' systems had also brought about a considerable expansion of knowledge in breadth and in depth of these complex systems, and their essential importance in connection with the production and properties of the sintered and hot-pressed silicon nitrides was now clear. The distinction between 'silicon nitride' and 'sialon' materials was indeed in certain respects becoming less meaningful. The crystallization of the intergranular glass phase, known to be present but barely detectable at grain interfaces in 1976, and recognized as the key to obtaining high strengths at high temperat­ure, had received attention and by now formed the basis for the development of a range of commercial materials. In presenting the case, attention was also drawn to the practical achievements seen in the expanding number of ceramic gas turbine and diesel engine

VI

research programmes in the U.S.A. and in Europe, and the intense interest being shown in high grade ceramic materials in Japan. At the same time, it was recognized by the planning group that the last five years had also seen big steps in the development of other groups of high strength ceramic materials for engineering applications. High grade sintered silicon carbides in particular were now serious contenders, together with the self-bonded or siliconized forms, as gas turbine and diesel engine components. The possibility that the subject of a second Advanced Study Inst­itute might be broadened to include silicon carbide was, however, rejected on the grounds that it would not then be possible, even in the space of a two-week meeting, to treat adequately either set of materials. Nonetheless, in recognition of the fact that the silicon carbides were becoming increasingly mature materials and, in some senses, competitors to the nitrides, it seemed very appropriate that a formal discussion session should be devoted to this subject, so that recent developments in the area of the sili­con carbides could be examined, and respective properties compared.

The Institute programme again was a very full one with 15 invited review contributions and some 60 shorter presentations on specific topics. The texts of the majority of these presentations appear in this volume, together with edited selected contributions from the very lively discussion sessions which followed the presen­tations, and of which teams of reporters, and the speakers, attempted to keep a record. Also included are the prepared texts of the four major contributions to the session on 'National Research Programmes', which will be of interest as a rare statement of the extent of international interest at a high level in nitrogen cer­amic materials. As in 1976, the original intention of the planning group was that all types of ceramic nitrides should receive atten­tion during the Institute. As a glance at the 'Contents' section will show, however, the fact is that with only one or two notable exceptions, in the ceramic nitrides area interest is still firmly focussed on silicon nitride and the 'sialon' families of materials.

The success of this second Institute rested largely on the uniformly very high quality of the teaching and research review contributions, and of the ensuing discussions, and it is the part­icipants themselves therefore who must take the credit. We were, however, indebted to the members of the international planning group, who by their efforts helped to ensure that those particip­ants best able to represent the many active groups in the field were indeed present at Sussex. Essential financial support for the Institute was provided by the Scientific Affairs Division of NATO, together with generous contributions from the European Research Office in London (USARDSG-UK), the Office of Naval Research, Arlington, Virginia, and the National Science Foundation, Washington D.C. In the context of the preliminary planning of the Institute, the valuable guidance and help of Dr. Mario di Lullo and Dr. Tilo Kester of the Scientific Affairs Division of NATO is gratefully acknowledged.

The Institute has also to acknowledge with gratitude the behind-the-scenes activities of many members of Staff of the Universities of Sussex and Leeds. In particular, the efficient organisational work of Mrs. S. Michael and Mrs. J. Hutchings of

Vll

the Sussex Conference Office, and Miss Gillian Horsfall, seconded to the Institute Office from the Leeds Secretarial Office, should be singled out for mention. Equally important for the smooth run­ning of the technical sessions and refreshment breaks was the assistance provided by the technical staff of the Sussex Department of Physics. Messrs. Lu and Oswald of the University of Leeds Department of Ceramics, and Mr. Spacie from the Crystallography Laboratory at the University of Newcastle-upon-Tyne, provided flawless service in the projection room. Finally, the Editor has to acknowledge once again his deep indebtedness to Miss Susan H. Toon, ably assisted by Mrs. Susan Richards, in the Leeds Department of Ceramics, for their calm efficiency in dealing with a very large volume of correspondence and paper-work, both before and after the period of the Institute, and in the" typing of many sections of this Proceedings.

F.L. Riley Editor

PREFACE

PARTICIPANTS

GENERAL INTRODUCTION

CONTENTS

(R) Nitrogen Ceramics 1976-1981 R.N. Katz

SECTION A

CRYSTAL CHEMISTRY

(R) Silicate Structures and Atomic Substitution J. Lang

(R) The Characterization of a: '-sialons and the a:-{3 relationships in sialons and silicon nitrides K.H. Jack

The Structural Characterization of Sialon Polytypoids D.P. Thompson, P. Korgul and A. Hendry

SECTION B

THERMODYNAMICS

Calculation of Phase Equilibria in Systems Based on Silicon Nitride J. Weiss, H.L. Lukas and G. Petzow

Phase Equilibrium Studies in Silicon Nitride -Metal Oxides Systems T.Y. Tien, G. Petzow, L.J. Gauckler and J. Weiss

Solid-Liquid Reactions in Part of the System Si-Al-Y-N-O H. Hohnke and T.Y. Tien

High Temperature Reactions and Microstructures in the A1203-A1N System J.W. McCauley and N.D. Corbin

SECTION C

FORMATION PROCESSES

Silicon Nitridation F. L. Riley

(R) indicates an invited review lecture

IX

v XV

3

23

45

61

77

89

101

111

121

x

The Effect of Silicon Particle Size on the Nitriding Behaviour of Reaction Bonded Silicon Nitride Compacts J.A. Mangels

135

An Experimental Plan for the Nitridation of Si +AI 141 Compacts W. Mustel and D. Broussaud

Preparation of Silicon Nitride from Silica 149 M. Mori, H. Inoue and T. Ochiai

On the Preparation of Fine Silicon Nitride Powders 157 G. Schwier

SECTION D

STRUCTURAL DEVELOPMENT

(R) Liquid Phase Sintering J. Weiss and W.A. Kaysser

(R) Sintering of Silicon Nitride, A Review P. Popper

169

187

Influence of Powder Properties and Processing 211 Parameters on the Sintering of Silicon Nitride G. W8tting and H. Hausner

Sintering of Silicon Nitride-Based Materials using 219 the Powder Bed Technique R. Pompe and R. Carlsson

Densification and Transformation Mechanisms in 225 Nitrogen Ceramics S. Hampshire and K.H. Jack

Sintering of Reaction Bonded Silicon Nitride 231 J.A. Mangels

Microstructure of Densified Reaction Bonded Silicon 237 Nitride J.R.G. Evans and A.J. Moulson

Sintering of Aluminium Nitride with Low Oxide Addition 245 K.A. Schwetz, H. Knoch and A. Lipp

(R) Stress Assisted Hot Formation of Ceramics A. Mocellin

Influence of Composition and Process Selection on Densification of Silicon Nitride G.E. Gazza

253

273

A Gas Pressure Sintering Process for Producing Dense 283 Silicon Nitride c. Greskovich

Hot Pressing of Aluminium Nitride J.P. LeCompte, J. Jarrige and J. Mexmain

SECTION E

VITREOUS STATE

(R) Structure-Property Relationships of the Vitreous State H.A. Schaeffer

XI

293

303

The Preparation and Properties of Oxynitride 323 Glasses R.A.L. Drew, S. Hampshire and K.H. Jack

The Crystallization Behaviour of a Mg-Si-O-N Glass 331 T.M. Shaw and G. Thomas

Thermodynamics of Grain Boundary Glass 337 Crystallization (Abstract) R. Raj

SECTION F

MICROSTRUCTURE

(R) The Microstructure of Nitrogen Ceramics D.R. Clarke

Evaluation of Microstructure in ~'-Sialon Materials by TEM Methods and its Correlation to Some Properties P. Greil and J. Weiss

Sialon X-Phase D.P. Thompson and P. Korgul

341

359

375

Microstructure Development in Silicon Nitride 381 H. Knoch, K.A. Schwetz and A. Lipp

Contribution of the Strength-Porosity Relationship 393 in Reaction-Bonded Silicon Nitride J. Heinrich

SECTION G

CHEMICAL INTERACTIONS

(R) The Kinetics of Gas-Solid Reactions and Environmental Degradation of Nitrogen Ceramics M. Billy

403

Thermodynamics of Cation Diffusion through an 421 Intergranular Phase: Application to Environmental Reactions with Nitrogen Ceramics D.R. Clarke

XII

Oxidation of Hot-Pressed Silicon Nitride G.N. Babini and P. Vincenzini

Oxidation Behaviour of ~'-Sialons in Oxygen and Carbon Dioxide J.G. Desmaison, M. Brossard, M. Desmaison-Brut and P. Goursat

Metallic Infiltration of Reaction Bonded Silicon Oxide W.G. Schmidt

Brazing of Silicon Nitrides J.E. Siebels

427

439

447

455

SECTION H

MECHANICAL AND PHYSICAL PROPERTIES

(R) High Temperature Deformation and Fracture Phenomena 467 of Polyphase Silicon Nitride Materials F.F. Lange

(R) Time-Temperature Effects in Nitride and Carbide 491 Ceramics R.N. Katz and G.D. Quinn

High Temperature Fatigue Failure in Pressureless 501 Sintered Silicon Nitride I. Oda, M. Matsui and T. Soma

Effect of Deformation on the Fracture of Si3N4 and 507 Sialon R.J. Fields, T-J. Chuang,E.R. Fuller (Jr.) and N.J. Tighe

Cyclic Fatigue Behaviour of Ceramics 515 Y. Matsuo, Y. Hattori, Y. Katayama and I. Fukuura

The Fracture Behaviour of Hot-Pressed Silicon 523 o Nitride between Room Temperature and 1400 C

K. Khz

Parameter Studies on the Oxidation and the Strength 529 Behaviour of Silicon Nitride J.E. Siebels

Characterization, Oxidation and Mechanical Behaviour of Reaction-Bonded Silicon Nitride F. Porz

Creep and Internal Oxidation of Reaction Bonded Silicon Nitride F. ThUmmler and G. Grathwohl

539

547

Influence of Corrosion and Microstructure on the Mechanical Properties of Si-Y-O-N Ceramics P. Goursat, A. Bouarroudj and J.L. Besson

(R) Thermal Properties and Thermal Shock Resistance of Nitrogen Ceramics G. Ziegler

XIII

557

565

Thermal Shock Resistance of two Nitrogen Ceramics 589 P. Boch and J.C. Glandus

(R) Non-Destructive Failure Prediction in Ceramics A.G. Evans

595

Non-Destructive Evaluation of Ceramic Gas Turbine 627 Components by X-rays and other Methods K. Goebbels and H. Reiter

(R) Surface Damage in Ceramics: Implications for Strength Degradation, Erosion and Wear D.B. Marshall

Contact Stresses at Ceramic Interfaces D.W. Richerson

SECTION I

APPLICATIONS

Sintering Properties and Fabrication of Si3N4/ Y203-Based Ceramics C.L. Quackenbush, J.J. Smith, J.T. Neil and K.W. French

635

657

669

Lucas Syalons: Composition, Structure, Properties 683 and Uses R.J. Lumby, E. Butler and M.H. Lewis

The Nature of SiC for Use in Heat Engines as 695 Compared to Si3N4: An Overview of Property Differences D.C. Larsen and J.W. Adams

Fabrication of Complex Shaped Ceramic Articles by 711 Slip Casting and Injection Molding J.A. Mangels

Hot Isostatic Pressing of Ceramics 717 H.T. Larker

SECTION J

NATIONAL RESEARCH PROGRAMMES

U.S. National Programmes in Ceramics for Energy Conversion R.N. Katz and R.B. Schulz

727

XIV

status Report 1981 on the German BMFT-Sponsored Programme "Ceramic Components for Vehicular Gas Turbines" W. Bunk and M. B8hmer

Nitrogen Ceramics in France M. Billy, J. Desmaison and P. Goursat

Current Japanese Research Programmes into Nitrogen Ceramics (presented by K.Suzuki) H. Suzuki

SURVEY AND CONCLUSIONS

Concluding Remarks K.H. Jack

AUTHOR INDEX

SUBJECT INDEX

INDEX OF CRYSTAL STRUCTURES

INDEX OF SYSTEMS AND SUB-SYSTEMS

737

753

755

771

775

777

791

793

PARTICIPANTS

Advisory Committee:

M. Billy W. Bunk K.H. Jack R.N. Katz F.F. Lange F. L. Riley P. Vincenzini

University of Limoges, France DFVLR, K8ln, Germany University of Newcastle-upon-Tyne, .U.K. AMMRC, Watertown, U.S.A. Rockwell International, U.S.A. University of Leeds, U.K. (Director) IRTEC, Faenza, Italy.

Local Organization:

Mrs. S. Michael and Mrs. J. Hutchings, University of Sussex. Miss G.L. Horsfall, University of Leeds.

Chairmen and Discussion Reporting Teams:

Session

July 27th 1. P. Popper 2. J. Lang

July 28th 1. P.E.D. Morgan 2. H. Hausner

July 29th 1. K.H. Jack 2. A. Mocellin

July 30th 1. C. Greskovich 2. D.P. Thompson

July 31st 1. D.R. Clarke 2. M. Billy 3. J. Weiss

August 3rd 1. J. Lang 2. T.Y. Tien

August 4th 1. D. Marshall 2. F. ThUmmler 3. A.G. Evans

August 5th 1. J.A. Mangels 2. G. Ziegler

August 6th 1. E. Gugel 2. R.N. Katz

August 7th 1. F. L. Riley.

D.P. Thompson, T.Y. Tien P.E.D. Morgan, G.E. Gazza

K.H. Jack, C. Greskovich S. Hampshire, P. Popper

M. Kizilyalli, J. Briggs J.W. McCauley, H. Knoch

F.L. Riley, R.N. Katz H. Hausner, W. Schmidt

A. Mocellin, R. Pompe D. Marshall, J.R.G. Evans R.J. Fields, G. W8tting

T.M. Shaw, J.A. Mangels J. Heinrich, J. Desmaison

J. Cotton, C.S. Furtado J. Kirk, K. Kriz K. Goebbels, H. Knoch

H.T. Larker, G. Schwier D.W. Richerson, K. Suzuki

R.J. Lumby, C.L. Quackenbush

xv

XVII

Hampshire, :oz.. s. College of Engineering and Science, National Insti tute for Higher Education, Limerick, Eire.

Hattori, Mr. Y. Research & Development, The Nippon Tokushu Togyo Kaisha Ltd., 14-18 Takatsuji-cho, Mizuho-cho, Nagoya, Japan.

Hausner, Prof. H. Insti tut f'Ur Nichtmetallische Werkstoffe, Englische Strasse 20, 1000 Berlin 12, Germany.

Heinrich, :oz.. J. Rosenthal Aktiengesellschaft, Insti tut fih. Werk­stofftechnik, Wittelsbacherstrasse 49, 8672 Selb, W. Germany.

Holmke, Mrs. H. 4228 E Engineering Bldg., Uni versi ty of Michigan, Ann Arbor, Michigan 48018, U.S.A.

Hunt, Mr. R.A. Lucas Industries Ltd., Group Research Centre, Shirley, Solihull, B90 4JJ, U.K.

Jack, Prof. K.H. Department of Metallurgy and Engineering Materials, The Uni versi ty, Newcas tIe upon Tyne, NE1 7RU, U. K.

Katz, :oz.. R.N. Materials Branch, A:rm.y Materials and Ceramics Research Center, Watertown, Mass. 02172, U.S.A.

Kirk, :oz.. J. Morgan Themic Ltd., Technological Centre, Bewdley Road, Stourport on Severn, DY13 8Q,R, U.K.

Kizilyalli" :oz.. H.M. Department of Physics, Middle East Technical Uni versi ty, Ankara, Turkey.

Kizilyalli, :oz.. M. Department of Chemistry, Middle East Technical Uni versi ty, Ankara, Turkey.

Knoch, :oz.. H. Elektroschmelzwerk Kempten GmbH, Postfach 1526, 8960 Kempten, W. Germany.

Kriz, Mr. K. Institut f-llr Werkstoffwissenschaften I, UniversitM.t Erla.ngen-Nlirnberg, Martensstrasse 5, D-8520 Erla.ngen, W. Germany.

Lal, :oz.. M. Department of Metallurgy & Materials Engineering, Lehigh University, Bethlehem, Pat 18015, U.S.A.

Lang, Prof. J. Universite de Rennes, UER structure et Proprietes de la Matiere, Laboratoire de Chimie Minerale C, Avenue du General Leclerc, 35031 Rennes Cedex, France.

Lange, Dr. F.F. Rockwell International Science Center, 1049 Camino dos Rios, P.O. Box 1085, Thousand Oaks, California 91360, U.S.A.

Larker, Dr. H. T. ASEA AB, S-91500 Robertsfors, Sweden. Larsen, Dr. D.C. lIT Research Institute, Materials Technology

Division, 10 West 35 Street, Chicago, Illinois 60616, U.S.A. Lauri tzen, :oz.. O. Universi tetet i Trondheim, Norges Tekniske

Hlgskole, Institutt f-llr Silikat-OG Hoytemperaturkjemi, Sem Saelandsvei 12, N-7034, Trondheim-NTH, Norway.

Lecompte, :oz.. J-P. Ecole Nationale Superieure des Mines de Saint-Etienne, 158 Cours Fauriel, 42023 Saint-Etienne Cedex, France.

Lenhart, Mr. A. Insti tut ftI.r Werkstoffwissenschaften, Lehrstuhl III, UniversitM.t Erla.ngen-Nlirnberg, Martensstrasse 5, 8520 Erla.ngen, W. Germany.

Lu, Mr. H. Y. Department of Ceramics, Houldsworth School of Applied Science, The University, Leeds 182 9JT, U.K.

Lumby, :oz.. R.J. Lucas Industries Ltd., Group Research Centre, Shirley, Solihull, B90 4JJ, U.K.

XVIII

McCauley, Dr. J.W. Ceramics Research Division, Army Materials and Mechanics Research Centre, Watertown, Mass. 02172, U.S.A.

Mangels, Mr. J.A. Ford Mator Compa.ny, Tln'bine Developnent Dept., 20000 Rotunda Drive, Dearborn, Michigan 48121, U.S.A.

Marshall, Dr. D. Depar'bnent of Materials Science & Mineral Engin­eering, Hearst Mining Building, University of California, Berkeley, California, 94720, U.S.A.

Matsuo, Mr. Y. 2808 Iwasaki, Komoki-Si, Aichi Ken 485, Japan. Maunder, Mr. M.J. de F. Department of Industry, Abell House,

John Islip Street, London SW1P 4LN, U.K. Macellin, Prof. A. Laboratoire de ceramique, Ecole Poly technique

Federale de Lausanne, 34 ch. de Bellerive, CH-1007 Lausanne, Switzerland.

Margan, Dr. P.E.D. Rockwell International Science Center, 1049 Camino dos Rios, P.O. Box 1085, Thousand Oaks, California 91360, U.S.A.

Mari, Mr. M. Technical Department, Refractories Division, '1'oshiba Ceramics Co. Ltd., 1 Minamifuji, Ogakie, Kariya-shi, Aichi-Ken, Japan 448. , ,

Mus tel , Mr. W. Centre des Materiaux, Ministere de l'Industrie, Ecole Na tionale Buperieu:t'e des Mines de PariS, B. p. 87, 91003 Evry Cedex, France.

Nicol, Dr. A.W. Department of Minerals Engineering, University of BiDmingham, BiDmingham B15 2'1''1', U.K.

Nilsson, Mr. S. Department of PhysiCS, Chalmers University of Technology, Go thenberg , Sweden 41296.

ada, Mr. I. Research & Development Laboratory, NGK Insulators Ltd., 2-56 Buda, Mizuho, Nagoya 467, Japan.

Orange, Dr. G. Bat. 502, INSA, 69261 Villeurba.nne Cedex, France. Ortali, Dr. P.L. IR'I'EC, Via Gra.na.rolo 8, 48018 Faenza, Italy. Oswald, Mr. J.R. Department of Ceramics, Houldsworth School of

Applied Science, University of leeds, leeds LS2 9J'I', U.K. Pompe, Dr. R. Swedish Institute for Silikate Research,

Gibral targatan 5J, S-412 58 G8teborg, Sweden. Popper, Dr. P. Bri tish Ceramic Research Association, Queens Road,

Penkhull, Stoke-on-wrent, U.K. Porz, Mr. F. Institut fti:r Werkstoffk:unde II, UniversitRt Karlsruhe

('I'H), Kaiserstrasse 12, n-7500 Karlsruhe 1, W. Germany. Quackenbush, Dr. C.L. Precision Materials 'I'echnology Department,

G'I'E Laboratories Inc., 40 Sylvan Road, Waltham, Mass. 02254, U.S.A.

Ratcliff, Mr. N.A. NRDC, Kingsgate House, 66/74 Victoria Street, London SW1E 6SL, U.K.

Richerson, Mr. D.W. Materials Engineering, Engineering Sciences, Garrett 'I'urbine Engine Co., 111 S. 34th Street, P.O.Box 5217, Phoenix, Arizona, 85010, U.S.A.

Riley, Dr. F.L. Department of Ceramics, Houldsworth School of Applied ·Science, University of leeds, leeds I.S2 9J'I', U.K.

Rothwarf, Dr. F. Chief, Materials Branch, European Research Office, Uni ted States Army, 223 Old Marylebone Road, London NW1 5'I'H, UK.

XIX

Schmidt, Dr. W. HutscheXl1'8uther AG, Central laboratory, 1}-8672 Selb, W. Ge:t'mB.Il;y. "

Schrimpf, Dipl. lng. C. Lehrstuhl fur Glas und Keramik, Insti tut Flir Steine und Erden, Teohnisohe Uni versi tit Claus thaI, Zehntnerstrasse 2A, 1}-3392 Claus thal-Zellerf'eld , W. Ge~.

Sohwier, Dr. G. Hemann C. Starok Berlin, Postfach 2540, 1}-3380 Goslar 1, W. Ge~.

Shaw, Dr. T.M. Department of Materials Soience & Engineering, College of Engineering, Cornell Uni versi ty, Ithaca, N.Y. 14853, U.S.A.

Siebels, lIh'. J.E. Volkswagenwerk AG, E/Zentrallabor-Metallurgie, 3180 Wolfsburg, W. Ge~.

Spacie, Mr. C. J. Crystallogt'aphy laboratory, Uni versi ty of Newoastle-upon-Tyne, Newoastle-upon-Tyne NE1 7RU, U.K.

Suzuki, Mr. K. Asahi Glass Co. ,Ltd., Research laboratory, Hazawa-Cho, Kanagawa-Ifu, Yokohama, Japan.

TalUlt, Dr. R.J. Smi the Industries Ltd., Putney Division, KLG Works, Putney Vale, London SW15 3DY, U.K.

Thompson, Dr. D.P. Crystallography laboratory, The University, Newoastle-upon-Tyne NE1 7RU, U.K.

Thi:Immler, Prof. F. Institut f'lir Werkstoffkunde, UniversitM.t Karlsruhe (TH), POstfaoh 6380, 1}-7500 Karlsruhe 1, W.Ge~.

Tien, Prof. T. Y. Department of Materials Science & Metallurgioal Engineering, University of Miohigan, Ann Arbor, Miohigan 48103, U.S.A.

Weiss, Dr. J. Aluminium-Hfitte 1lheinfelden GmbH, 1}-7888 1lheinfelden 1, Postfaoh 1140, W. Germany.

Winder, lIh'. S. Ceramios Researoh Group, Department of Physios, Universi ty of Warwiok, Coventry OV4 7AL, U.K.

Wtting, Mr. G. DFVLR, Insti tlit f'lir Werkstoff-Forsohung, Postfach 90 60 58, 1}-5000 K8ln 90, W. Germany.

Yeter, Miss B. Asagi Ayranci, Menevis Sok 41/10, Ankara, Turkey. Ziegler, Dr. G. DFVLR, Postfaoh 90 60 58, D-5000 K8ln 1,

W. Ge:t'mB.Il;y •

Group Photograph