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Ceramic Processing PDF

227 Pages·1995·12.714 MB·English
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Ceramic Processing Ceramic Processing Edited by R.A. Terpstra Manager ofthe Centre for Technical Ceramics N etherlands Organization for Applied Scientific Research TNO, Eindhoven, The Netherlands P.P.A.C. Pex Pl'oject Manager, Membrane Materials Development Netherlands Energy Research Foundation ECN, Petten, The Netherlands and A.H. de Vries Product Manager, Traditional Ceramics Netherlands Organizationfor Applied Scientific Research TNO, Eindhoven, The Netherlands SPRINGER-SCIENCE+BUSINESS MEDIA, B.\I. First edition 1995 © 1995 Springer-Science+Business Media Dordrecht Originally published by Chapman & Hali in 1995 Softcover reprint of tbe hardcover Ist edition 1995 Typeset in 10/12 pt Times by Thomson Press (India) Ltd., New Delhi Printed in Great Britain by St Edmundsbury Press, Bury St Edmunds ISBN 978-94-010-4236-9 ISBN 978-94-011-0531-6 (eBook) DOI 10.1007/978-94-011-0531-6 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the UK Copyright Designs and Patents Act, 1988, this publication may not be reproduced, stored, or transmitted, in any form or by any means, without the prior permission in writing of the publishers, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries conceming reproduction outside the terms stated here should be sent to the publishers at the London address printed on this page. The publisher makes no representation, express or implied, with regard to the accuracy of the information contained in this book and cannot accept any legal responsibility or liability for any errors or omissions that maybe made. A catalogue record for this book is available from the British Library Library ofCongress Catalog Card Number: 95-67913 8 Printed on acid-free text paper, manufactured in accordance with ANSljNISO Z39.48-1992 (Permanence of Paper). Contents List of contributors ix Foreword by R. Metselaar xi Preface xiii 1 Special ceramics for modern applications: which? why? how? 1 1.1. McColm 1.1 Introduction 1 1.2 Predictions arising from simple considerations of strength 5 1.2.1 Group 1: flawless material 6 1.2.2 Replacement of the surface energy term in equation (1.7) 7 1.3 Materials predictions based on equation (1.16) 9 1.3.1 The product triangle 10 1.4 Some predictions based on fracture toughness 12 1.5 The size and shape of materials needed for processing 14 1.6 Prediction of limiting particle size arising from mechanical grinding 16 1.7 Combination of ultrafine ceramic powders and fibres: ceramic-ceramic composites 21 1.7.1 Composite toughness 23 1.8 Relative costs 26 1.9 Self-propagating high-temperature synthesis (SHS) 27 References 33 2 Laser vapour phase synthesis of ceramic powders 34 R.A. Bauer and J. Schoonman 2.1 Introduction 34 2.1.1 General introduction 34 2.1.2 The use of sensitizers 35 2.2 Experimental aspects 37 2.3 Results 38 2.3.1 Optical absorption measurements 38 2.3.2 Thermodynamic calculations 41 2.3.3 Visible spectroscopy 46 VI Contents 2.3.4 Synthesis of silicon 49 2.3.5 Synthesis of Si3N4 51 2.4 Discussion 54 2.5 Conclusions 55 References 56 3 Particle interactions in suspensions 58 KG. Horn 3.1 Introduction 58 3.2 Surface forces 59 3.2.1 Forces and energies 61 3.2.2 Flat and curved surfaces: the Derjaguin approximation 61 3.2.3 van der Waals forces 63 3.2.4 Electrostatic forces in a non-polar environment 68 3.2.5 Electrostatic forces in a polar liquid: double-layer repulsion 69 3.2.6 DLVO theory 75 3.2.7 Charge correlation effects 77 3.2.8 Structural forces 78 3.2.9 Solvation forces 79 3.2.10 'Hydrophobic' forces 80 3.2.11 Capillary forces 81 3.2.12 Effects of surfactants 83 3.2.13 Effects of polymers 85 3.2.14 Short-range forces 87 3.2.15 Present status of theoretical and experimental work on surface forces 88 3.3 Behaviour of suspensions 89 3.3.1 Dispersion 89 3.3.2 Dense suspensions 89 3.3.3 Consolidation 91 3.3.4 Rheology 92 3.3.5 Strength of consolidated body 93 3.4 Controlling interparticle forces 93 3.4.1 Minimizing attractive forces 94 3.4.2 Arranging repulsive forces 94 3.4.3 Other considerations 96 3.5 Some examples 97 3.5.1 Improved strength from homogenization of powder 97 3.5.2 Aggregation with strong attractive forces gives low volume fraction 97 3.5.3 Adding the right amount of polymer dispersant 98 3.5.4 Effective use of block copolymer 98 3.5.5 Controlling rheology as well as stability 98 Contents Vll 3.5.6 Maintaining low viscosity until after forming 99 3.5.7 Using 'one stone to kill two birds' 99 References 100 4 Dry pressing of ceramic powders 102 D. Bortzmeyer 4.1 Introduction 102 4.2 Industrial problems 103 4.2.1 Compaction technology 103 4.2.2 A few compaction problems 104 4.3 Macroscopic behaviour: the classical approach 107 4.3.1 DensityI pressure relationship: theoretical and experimental 107 4.3.2 piP relationship: influence of powder characteristics 109 4.3.3 piP relationship: influence of process parameters 115 4.3.4 Radial pressure coefficient 117 4.3.5 Wall friction coefficient 120 4.3.6 Green tensile strength 120 4.3.7 Conclusion 123 4.4 Macroscopic behaviour: the mechanical approach 124 4.4.1 Density distribution measurement 124 4.4.2 Continuum mechanics theory 127 4.4.3 Experimental 128 4.4.4 Results 129 4.4.5 Numerical simulation 131 4.4.6 Conclusion 132 4.5 Microscopic behaviour 133 4.5.1 Microstructure evolution 133 4.5.2 Micromechanics of compaction 135 4.5.3 Conclusion 139 4.6 Conclusions 140 Appendix: Tensor notation for stress 141 References 142 5 The principles of tape casting and tape casting applications 147 R.E. Mistler 5.1 Introduction 147 5.2 The doctor blade tape process 153 5.2.1 Materials technology and seleCtion 153 5.2.2 Tape casting process and equipment 156 5.3 Subsequent processing of unfired tapes 165 5.3.1 Shaping 165 5.3.2 Multilayer processing 166 References 172 Vlll Contents 6 Plastic forming of ceramics: extrusion and injection moulding 174 M.A. Janney 6.1 Introduction to extrusion 174 6.2 Formulation principles 174 6.2.1 Role of additives 175 6.2.2 Powder 178 6.3 Mixing 179 6.4 Soil mechanics 183 6.4.1 Extrusion theory 183 6.4.2 Wet strength 184 6.5 The extrusion process 185 6.5.1 Equipment 185 6.5.2 Mechanics of flow 186 6.5.3 Dies 190 6.5.4 Defects 191 6.6 Additional topics 192 6.6.1 Ultrasonic extrusion 192 6.6.2 Multilayer or coaxial extrusion 194 6.7 Introduction to injection moulding 194 6.7.1 A little history 195 6.7.2 Limitations 195 6.7.3 The process 195 6.8 Detailed discussion of the process 196 6.8.1 Powder considerations 196 6.8.2 Formulation 197 6.8.3 Mixing 199 6.8.4 Equipment 199 6.8.5 Binder removal 201 6.8.6 Moulding parameters 201 6.8.7 Defects 204 6.8.8 Other factors 205 6.9 New approaches to forming complex shapes 206 References 209 Index 213 Contributors R.A. Bauer, PHD, Department ofInorganic Materials, TNO, Eindhoven, The Netherlands. D. Bortzmeyer, PHD, Leader of Shape Forming Group, Rhone-Poulenc Research, Aubervilliers, France. R.G.Horn PHD, Professor of Materials Science, University of South Australia, Adelaide Australia. M.A. Janney, PHD, Metals and Ceramics Division, Oak Ridge National Laboratory, Tennessee, USA. I.J. McColm, DSe, DPHIL, FRSC, C. CHEM., FIM, FRSA, Professor of Ceramic Materials, Department of Industrial Technology, University of Bradford, UK. R.E. Mistler, SeD, Richard E. Mistler Inc., Morrisville, Pennsylvania, USA. J. Schoon man, MSe PHD, Professor of Applied Inorganic Chemistry, Delft University of Technology, The Netherlands. Foreword Two years after the foundation of the European Ceramic Society the first ECerS Conference was held in Maastricht, The Netherlands. After this successful conference it was felt that the ECerS should not only stimulate ceramic research but also run projects of an educational character. To this end the Netherlands Ceramic Society decided to sponsor a summerschool on ceramic processing intended for young ceramists from European countries. Several internationally recognized ceramic specialists were prepared to lecture and the course was fully attended. In fact, this course showed that there is a clear need for dedicated courses at a moderate fee. A venue was chosen where the participants would have ample opportunities for personal contacts. In this way the summerschool gave the students more than purely technical training. After the meeting the ECerS Council established an Educational Committee to take care of educational matters on a permanent basis. Following an initiative of the French Ceramic Society a special Conference of Higher Educational Institutions in Ceramics was organized under the name Euro forum in 1992 in Limoges, France. The second Euroforum was held in 1994 in Hohr-Grenzhausen, Germany. These meetings aim to bring together educa tors, graduates and industrial managers. Further activities under the auspices of the ECerS are planned. Having been involved in the preparation of the course, it is a great pleasure to introduce the book of the proceedings of the NKV-summerschool. The contents and the level are such that we trust that many ceramists will benefit from the book. I congratulate the editors and organizers of the summerschool on their initiative. R. Metselaar Past-president. ECerS Preface This book has been edited from the lectures given at the NKV-summerschool on ceramic processing which was organized by the Netherlands Ceramic Society (NKV), 5-9 September 1991 in Petten, The Netherlands. The NKV-summerschool was sponsored by: • The Netherlands Ceramic Society, NKV • The European Ceramic Society, ECerS • Ceramic Manufacturers Association, VKI • The Netherlands Energy Research Foundation, ECN • The Netherlands Organisation for Applied Scientific Research, TNO • The National Ceramic Centre, NKA • The Centre for Technical Ceramics, CTK • N.V. Royal Sphinx, Maastricht • Hoogovens Industrial Ceramics, HIC • Gimex, Geldermalsen • NIF A Instruments, Leeuwarden • CAM Implants, Leiden • Royal Tichelaar, Makkum • Ceratec, Haaften The following people were responsible for organizing the NKV-Summer school: • Dr ir R.A. Terpstra, CTK (Chairman) • Ir P.P.A.C. Pex, ECN (Secretary) • Mr A.H. de Vries, TNO-Ceramics (Treasurer) • Prof. dr R. Metselaar, CTK/Eindhoven University ofTechnology (Scientific Advisor) • Mrs C.A.L. Ruitenburg, ECN (Local organizer) • Ing. PJ. van Tilborg, ECN (Local organizer) The NKV-summerschool was arranged to provide (graduate) students, scien tists and engineers an opportunity to attend an advanced course in ceramic processing taught by internationally well-known lecturers. The lectures were presented by specialists on topics most relevant for ceramic processing, starting from powder synthesis and the behaviour of powder particles in dispersions in relation to colloidal consolidation

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