Ceramic processing

494 Pages·2017·16.895 MB·English

by  Rahaman, M. N

Ceramic
Processing

Ceramic
Processing
Mohamed N. Rahaman
University of Missouri-Rolla, USA
Boca Raton London New York
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Library of Congress Cataloging-in-Publication Data
Rahaman, M. N. 1950-
Ceramic processing / Mohamed Rahaman.
p. cm.
Includes bibliographical references and index.
ISBN 0-8493-7285-2 (acid-free paper)
1. Ceramics. 2. Ceramic engineering. 3. Polycrystals. 4. Sintering. I. Title.
TP807.R278 2006
666--dc22 2006043889
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Contents
Chapter 1 Ceramic Fabrication Processes: An Introductory Overview.......................................1
1.1 Introduction...............................................................................................................................1
1.2 Ceramic Fabrication Processes.................................................................................................2
1.2.1 Gas-Phase Reactions....................................................................................................2
1.2.1.1 Chemical Vapor Deposition..........................................................................4
1.2.1.2 Directed Metal Oxidation.............................................................................7
1.2.1.3 Reaction Bonding..........................................................................................8
1.2.1.4 Silicon Nitride...............................................................................................9
1.2.1.5 Oxides..........................................................................................................10
1.2.1.6 Silicon Carbide............................................................................................11
1.2.2 Liquid Precursor Methods..........................................................................................12
1.2.2.1 Sol–Gel Processing.....................................................................................12
1.2.2.2 Polymer Pyrolysis.......................................................................................15
1.2.2.3 Silicon Carbide............................................................................................15
1.2.2.4 Silicon Nitride.............................................................................................17
1.2.2.5 Boron Nitride and Boron Carbide..............................................................18
1.2.3 Fabrication from Powders..........................................................................................19
1.2.3.1 Melt Casting................................................................................................19
1.2.3.2 Sintering of Compacted Powders...............................................................20
1.3 Production of Polycrystalline Ceramics from Powders: An Overview.................................21
1.3.1 Powder Synthesis and Powder Characterization........................................................21
1.3.2 Powder Consolidation................................................................................................22
1.3.3 The Sintering Process.................................................................................................22
1.3.4 Ceramic Microstructures............................................................................................25
1.4 Case Study in Processing: Fabrication of TiO from Powders.............................................28
2
1.5 Concluding Remarks..............................................................................................................30
Problems...........................................................................................................................................30
References........................................................................................................................................32
Chapter 2 Synthesis of Powders.................................................................................................37
2.1 Introduction.............................................................................................................................37
2.2 Powder Characteristics...........................................................................................................37
2.3 Powder Synthesis Methods....................................................................................................38
2.4 Powder Preparation by Mechanical Methods........................................................................39
2.4.1 Comminution..............................................................................................................39
2.4.1.1 High Compression Roller Mills..................................................................40
2.4.1.2 Jet Mills.......................................................................................................41
2.4.1.3 Ball Mills.....................................................................................................41
2.4.2 Mechanochemical Synthesis......................................................................................45
2.5 Powder Synthesis by Chemical Methods...............................................................................46
2.5.1 Solid-State Reactions..................................................................................................46
2.5.1.1 Decomposition.............................................................................................47
2.5.1.2 Chemical Reaction between Solids............................................................53
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2.5.1.3 Reduction....................................................................................................57
2.5.2 Liquid Solutions.........................................................................................................58
2.5.2.1 Precipitation from Solution.........................................................................58
2.5.2.2 Evaporation of the Liquid...........................................................................74
2.5.2.3 Gel Route....................................................................................................79
2.5.2.4 Nonaqueous Liquid Reaction......................................................................81
2.5.3 Vapor-Phase Reactions...............................................................................................81
2.5.3.1 Gas–Solid Reaction.....................................................................................82
2.5.3.2 Reaction between a Liquid and a Gas........................................................84
2.5.3.3 Reaction between Gases.............................................................................84
2.6 Special Topic: Synthesis of Nanoscale Ceramic Powders.....................................................87
2.6.1 Liquid Solution Techniques.......................................................................................87
2.6.2 Vapor-Phase Techniques.............................................................................................88
2.7 Concluding Remarks..............................................................................................................89
Problems...........................................................................................................................................89
References........................................................................................................................................91
Chapter 3 Powder Characterization.............................................................................................97
3.1 Introduction.............................................................................................................................97
3.2 Physical Characterization.......................................................................................................97
3.2.1 Types of Particles.......................................................................................................98
3.2.1.1 Primary Particles.........................................................................................98
3.2.1.2 Agglomerates...............................................................................................98
3.2.1.3 Particles.......................................................................................................98
3.2.1.4 Granules.......................................................................................................99
3.2.1.5 Flocs............................................................................................................99
3.2.1.6 Colloids.......................................................................................................99
3.2.1.7 Aggregates...................................................................................................99
3.2.2 Particle Size and Particle Size Distribution...............................................................99
3.2.2.1 Definition of Particle Size.........................................................................100
3.2.2.2 Average Particle Size................................................................................101
3.2.2.3 Representation of Particle Size Data........................................................102
3.2.3 Particle Shape...........................................................................................................106
3.2.4 Measurement of Particle Size and Size Distribution...............................................106
3.2.4.1 Microscopy................................................................................................106
3.2.4.2 Sieving.......................................................................................................107
3.2.4.3 Sedimentation............................................................................................109
3.2.4.4 Electrical Sensing Zone Techniques (the Coulter Counter).....................110
3.2.4.5 Light Scattering.........................................................................................111
3.2.4.6 X-Ray Line Broadening............................................................................113
3.2.5 Surface Area.............................................................................................................113
3.2.6 Porosity of Particles.................................................................................................116
3.2.6.1 Gas Adsorption..........................................................................................116
3.2.6.2 Mercury Porosimetry................................................................................119
3.2.6.3 Pycnometry................................................................................................121
3.3 Chemical Composition.........................................................................................................122
3.3.1 Optical Atomic Spectroscopy: Atomic Absorption and Atomic Emission..............122
3.3.2 X-Ray Fluorescence Spectroscopy...........................................................................124
3.4 Crystal Structure and Phase Composition...........................................................................125
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3.5 Surface Characterization......................................................................................................127
3.5.1 Surface Structure......................................................................................................129
3.5.2 Surface Chemistry....................................................................................................130
3.5.2.1 Auger Electron Spectroscopy (AES)........................................................130
3.5.2.2 X-Ray Photoelectron Spectroscopy (XPS)...............................................132
3.5.2.3 Secondary Ion Mass Spectrometry (SIMS)..............................................133
3.6 Concluding Remarks............................................................................................................136
Problems.........................................................................................................................................136
References......................................................................................................................................138
Chapter 4 Science of Colloidal Processing...............................................................................141
4.1 Introduction...........................................................................................................................141
4.2 Types of Colloids.................................................................................................................142
4.3 Attractive Surface Forces.....................................................................................................142
4.3.1 van der Waals Forces between Atoms and Molecules............................................142
4.3.2 van der Waals Forces between Macroscopic Bodies...............................................144
4.3.3 The Hamaker Constant.............................................................................................146
4.3.4 Effect of the Intervening Medium...........................................................................148
4.4 Stabilization of Colloidal Suspensions................................................................................148
4.5 Electrostatic Stabilization.....................................................................................................149
4.5.1 The Development of Charges on Oxide Particles in Water....................................149
4.5.1.1 Isomorphic Substitution............................................................................150
4.5.1.2 Adsorption of Ions from Solution............................................................150
4.5.2 Origins of the Electrical Double Layer...................................................................153
4.5.3 Isolated Double Layer..............................................................................................154
4.5.4 Surface Charge.........................................................................................................157
4.5.5 Repulsion between Two Double Layers..................................................................158
4.5.6 Stability of Electrostatically Stabilized Colloids.....................................................160
4.5.7 Kinetics of Flocculation...........................................................................................161
4.5.8 Electrokinetic Phenomena........................................................................................162
4.5.8.1 Microelectrophoretic Technique...............................................................163
4.5.8.2 Significance of the ζ Potential..................................................................164
4.6 Steric Stabilization................................................................................................................164
4.6.1 Adsorption of Polymers from Solution....................................................................165
4.6.2 Origins of Steric Stabilization..................................................................................167
4.6.3 Effects of Solvent and Temperature.........................................................................168
4.6.4 Stability of Sterically Stabilized Suspensions.........................................................170
4.6.5 Stabilization by Polymers in Free Solution.............................................................171
4.7 Electrosteric Stabilization.....................................................................................................172
4.7.1 Dissociation of Polyelectrolytes in Solution............................................................172
4.7.2 Adsorption of Polyelectrolytes from Solution.........................................................174
4.7.3 Stability of Electrosterically Stabilized Suspensions..............................................175
4.8 Structure of Consolidated Colloids......................................................................................176
4.9 Rheology of Colloidal Suspensions.....................................................................................178
4.9.1 Rheological Properties..............................................................................................178
4.9.2 Factors Influencing the Rheology of Colloidal Suspensions..................................180
4.9.2.1 Influence of Interparticle Forces...............................................................180
4.9.2.2 Influence of Particle Interactions on the Viscosity...................................183
4.9.2.3 Influence of Particle Characteristics.........................................................185
4.10 Concluding Remarks............................................................................................................187
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Problems.........................................................................................................................................187
References......................................................................................................................................189
Chapter 5 Sol–Gel Processing...................................................................................................193
5.1 Introduction...........................................................................................................................193
5.2 Types of Gels........................................................................................................................194
5.2.1 Particulate Gels.........................................................................................................194
5.2.2 Polymeric Gels.........................................................................................................195
5.3 Sol–Gel Processing of Aqueous Silicates............................................................................197
5.3.1 Effect of pH..............................................................................................................198
5.3.1.1 Polymerization in the pH range of 2 to 7................................................198
5.3.1.2 Polymerization above pH ≈ 7...................................................................200
5.3.1.3 Polymerization below pH ≈ 2...................................................................200
5.4 Metal Alkoxides....................................................................................................................201
5.4.1 Preparation of Metal Alkoxides...............................................................................201
5.4.1.1 Reactions between Metals and Alcohols..................................................201
5.4.1.2 Reactions Involving Metal Chlorides.......................................................202
5.4.1.3 Miscellaneous Methods.............................................................................202
5.4.2 Basic Properties........................................................................................................204
5.4.2.1 Physical Properties....................................................................................204
5.4.2.2 Chemical Properties..................................................................................205
5.5 Sol–Gel Processing of Silicon Alkoxides............................................................................206
5.5.1 Precursors.................................................................................................................206
5.5.2 Hydrolysis and Condensation..................................................................................207
5.5.2.1 Acid-Catalyzed Conditions.......................................................................208
5.5.2.2 Base-Catalyzed Conditions.......................................................................209
5.5.3 Polymer Growth.......................................................................................................209
5.5.3.1 Polymer Growth Models...........................................................................210
5.5.3.2 Structural Evolution of Sol–Gel Silicates................................................212
5.5.3.3 Rheological Measurements.......................................................................212
5.5.4 Gelation.....................................................................................................................215
5.5.5 Aging of Gels...........................................................................................................216
5.5.6 Drying of Gels..........................................................................................................216
5.5.6.1 Conventional Drying.................................................................................217
5.5.6.2 Supercritical Drying..................................................................................227
5.5.6.3 Structural Changes during Drying............................................................229
5.5.7 Gel Densification during Sintering..........................................................................230
5.6 Sol–Gel Preparation Techniques..........................................................................................234
5.6.1 Preparation of Particulate Gels................................................................................234
5.6.1.1 Single-Component Gels............................................................................234
5.6.1.2 Multicomponent Gels................................................................................236
5.6.2 Preparation of Polymeric Gels.................................................................................237
5.6.2.1 Use of Double Alkoxides..........................................................................237
5.6.2.2 Partial Hydrolysis of the Slowest Reacting Alkoxide..............................238
5.6.2.3 Use of a Mixture of Alkoxides and Metal Salts......................................239
5.6.2.4 Slow Addition of Small Amounts of Water..............................................240
5.6.2.5 Matched Hydrolysis Rates........................................................................241
5.7 Applications of Sol–Gel Processing....................................................................................241
5.7.1 Thin Films and Coatings..........................................................................................242
5.7.1.1 Dip Coating...............................................................................................242
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5.7.1.2 Spin Coating..............................................................................................244
5.7.1.3 Structural Evolution in Films...................................................................245
5.7.1.4 Applications of Films................................................................................245
5.7.2 Fibers........................................................................................................................245
5.7.3 Monoliths..................................................................................................................246
5.7.4 Porous Materials.......................................................................................................247
5.8 Concluding Remarks............................................................................................................247
Problems.........................................................................................................................................247
References......................................................................................................................................249
Chapter 6 Mixing and Packing of Powders..............................................................................253
6.1 Introduction...........................................................................................................................253
6.2 Mixing of Particulate Solids................................................................................................254
6.2.1 Types of Mixtures.....................................................................................................254
6.2.2 Mixing and Segregation Mechanisms......................................................................254
6.2.3 Mixture Composition and Quality...........................................................................257
6.2.3.1 Statistical Methods....................................................................................257
6.2.3.2 Measurement Techniques..........................................................................259
6.2.4 Mixing Technology...................................................................................................260
6.3 Packing of Particles..............................................................................................................262
6.3.1 Regular Packing of Monosized Spheres..................................................................263
6.3.2 Random Packing of Particles...................................................................................264
6.3.2.1 Monosized Particles..................................................................................265
6.3.2.2 Bimodal Mixtures of Spheres...................................................................266
6.3.2.3 Binary Mixtures of Nonspherical Particles..............................................269
6.3.2.4 Ternary and Multiple Mixtures.................................................................270
6.3.2.5 Continuous Particle Size Distributions.....................................................271
6.4 Concluding Remarks............................................................................................................274
Problems.........................................................................................................................................274
References......................................................................................................................................276
Chapter 7 Forming of Ceramics................................................................................................279
7.1 Introduction...........................................................................................................................279
7.2 Additives in Ceramic Forming.............................................................................................280
7.2.1 Solvents.....................................................................................................................280
7.2.2 Dispersants................................................................................................................282
7.2.2.1 Inorganic Acid Salts..................................................................................283
7.2.2.2 Surfactants.................................................................................................284
7.2.2.3 Low- to Medium-Molecular-Weight Polymers........................................286
7.2.3 Binders......................................................................................................................287
7.2.4 Plasticizers................................................................................................................290
7.2.5 Other Additives.........................................................................................................292
7.3 Forming of Ceramics............................................................................................................292
7.3.1 Dry and Semidry Pressing.......................................................................................292
7.3.1.1 Die Compaction........................................................................................292
7.3.1.2 Isostatic Compaction.................................................................................301
7.3.2 Casting Methods.......................................................................................................302
7.3.2.1 Slip Casting...............................................................................................302
7.3.2.2 Pressure Casting........................................................................................306