Nanomaterials (eBook)

Preface 6
Acknowledgements 8
Contents 9
Acronyms 13
List of Figures 14
List of Tables 33
Nanomaterials 34
Length Scales and Nanotechnology 34
What are Nanomaterials? 36
Classes of Materials 38
Making Nanomaterials 39
Making dn Materials 39
Health Risks Associated with Nanoparticles 40
Making Bulk Nanomaterials 41
Closing 50
Suggestions for Further Reading 51
Problems and Directions for Research 51
References 52
Fundamentals of Mechanics of Materials 54
Review of Continuum Mechanics 54
Vector and Tensor Algebra 54
Kinematics of Deformations 58
Forces, Tractions and Stresses 62
Work and Energy 67
Field Equations of Mechanics of Materials 68
Constitutive Relations, or Mathematical Descriptions of Material Behavior 68
Elasticity 69
Plastic Deformation of Materials 76
Fracture Mechanics 86
Suggestions for Further Reading 90
Problems and Directions for Research 90
References 92
Nanoscale Mechanics and Materials: Experimental Techniques 93
Introduction 93
NanoMechanics Techniques 94
Characterizing Nanomaterials 96
Scanning Electron Microscopy or SEM 96
Transmission Electron Microscopy or TEM 97
X-Ray Diffraction or XRD 98
Scanning Probe Microscopy Techniques 98
Atomic Force Microscopy or AFM 100
In situ Deformation 100
Nanoscale Mechanical Characterization 103
Sample and Specimen Fabrication 103
Nanoindentation 104
Microcompression 106
Microtensile Testing 114
Fracture Toughness Testing 118
Measurement of Rate-Dependent Properties 118
Suggestions for Further Reading 123
Problems and Directions for Research 123
References 123
Mechanical Properties: Density and Elasticity 126
Density Considered as an Example Property 126
The Rule of Mixtures Applied to Density 127
The Importance of Grain Morphology 132
Density as a Function of Grain Size 134
Summary: Density as an Example Property 136
The Elasticity of Nanomaterials 137
The Physical Basis of Elasticity 137
Elasticity of Discrete Nanomaterials 138
Elasticity of NanoDevice Materials 141
Composites and Homogenization Theory 142
Simple Bounds for Composites, Applied to Thin Films 144
Summary of Composite Concepts 147
Elasticity of Bulk Nanomaterials 148
Suggestions for Further Reading 149
Problems and Directions for Research 149
References 150
Plastic Deformation of Nanomaterials 151
Continuum Descriptions of Plastic Behavior 151
The Physical Basis of Yield Strength 152
Crystals and Crystal Plasticity 158
Strengthening Mechanisms in Single Crystal Metals 162
Baseline Strengths 163
Solute Strengthening 163
Dispersoid Strengthening 164
Precipitate Strengthening 165
Forest Dislocation Strengthening 165
From Crystal Plasticity to Polycrystal Plasticity 166
Grain Size Effects 168
Models for Hall-Petch Behavior 168
Other Effects of Grain Structure 180
Summary: The Yield Strength of Nanomaterials 184
Plastic Strain and Dislocation Motion 185
The Physical Basis of Strain Hardening 186
Strain Hardening in Nanomaterials 188
The Physical Basis of Rate-Dependent Plasticity 190
Dislocation Dynamics 190
Thermal Activation 192
Dislocation Substructure Evolution 196
The Rate-Dependence of Nanomaterials 197
Case Study: Behavior of Nanocrystalline Iron 202
Closing 205
Suggestions for Further Reading 205
Problems and Directions for Research 206
References 206
Mechanical Failure Processes in Nanomaterials 209
Defining the Failure of Materials 210
Failure in the Tension Test 213
Effect of Strain Hardening 214
Effect of Rate-Sensitivity 216
Multiaxial Stresses and Microscale Processes Within the Neck 218
Summary: Failure in the Simple Tension Test 219
The Ductility of Nanomaterials 220
Failure Processes 223
Nucleation of Failure Processes 224
The Growth of Failures 225
The Coalescence of Cracks and Voids 226
Implications of Failure Processes in Nanomaterials 226
The Fracture of Nanomaterials 227
Shear Bands in Nanomaterials 231
Types of Shear Bands 233
Shear Bands in Nanocrystalline bcc Metals 233
Microstructure Within Shear Bands 237
Effect of Strain Rate on the Shear Band Mechanism 240
Effect of Specimen Geometry on the ShearBand Mechanism 240
Shear Bands in Other Nanocrystalline Metals 241
Suggestions for Further Reading 241
Problems and Directions for Research 241
References 242
Scale-Dominant Mechanisms in Nanomaterials 244
Discrete Nanomaterials and Nanodevice Materials 244
Nanoparticles 244
Nanotubes 251
Nanofibers 254
Functionalized Nanotubes, Nanofibers, and Nanowires 255
Nanoporous Structures 255
Thin Films 256
Surfaces and Interfaces 256
Bulk Nanomaterials 257
Dislocation Mechanisms 257
Deformation Twinning 259
Grain Boundary Motion 264
Grain Rotation 265
Stability Maps Based on Grain Rotation 280
Multiaxial Stresses and Constraint Effects 285
Closing 285
Suggestions for Further Reading 285
Problems and Directions for Research 286
References 286
Modeling Nanomaterials 289
Modeling and Length Scales 289
Scaling and Physics Approximations 295
Scaling Up from Sub-Atomic Scales 296
The Enriched Continuum Approach 297
The Molecular Mechanics Approach 297
Molecular Dynamics 302
Discrete Dislocation Dynamics 305
Continuum Modeling 306
Crystal Plasticity Models 306
Polycrystalline Fracture Models 307
Theoretically Based Enriched Continuum Modeling 308
Strain Gradient Plasticity 315
Multiscale Modeling 317
Constitutive Functions for Bulk Nanomaterials 320
Elasticity 320
Yield Surfaces 321
Closing 322
Suggestions for Further Reading 323
Problems and Directions for Future Research 323
References 324
References 327
Index 338