Studying Kinetics with Neutrons (eBook)

Studying Kinetics with Neutrons 3
1 Introduction to Neutron Techniques 15
1.1 Why Neutrons? 15
1.2 Neutron Sources 17
1.3 Techniques 19
1.3.1 Three Axis Spectrometers 20
1.3.2 Backscattering Spectrometers 21
1.3.3 Time-of-Flight Spectrometers 23
1.3.4 Fixed Wavelength Diffractometers 25
1.3.5 Time-of-Flight Diffractometers 26
1.3.6 SANS Instruments 26
1.3.7 Reflectometers 28
1.3.8 Spin-Echo Spectrometers 29
1.4 … and What About Kinetics? 31
References 31
2 Systems in Real-time Using Quasielastic and Inelastic Neutron Scattering 32
2.1 Cement Research 32
2.1.1 Constituents and Hydration 33
2.1.2 Hydration Kinetics 34
2.1.3 Research Tools 35
2.2 Studying Hydrating Cement Using Quasielasticand Inelastic Neutron Scattering 36
2.2.1 Quasielastic Neutron Scattering of Hydrogenin Cement Systems 39
2.2.2 Models for QENS Data 39
Empirical Diffusion Models: Rotational Dynamics of Water 40
The Relaxing Cage Model: Translational-Dynamics of Water 45
Relaxing Cage Model: Combined Translational-Rotational Dynamics of Water 49
Jump-Diffusion and Rotation-Diffusion Models: Combined Rotational and Translational Dynamics of Water 51
2.2.3 Inelastic Neutron Scattering of Hydrogenin Cement Systems 53
Vibrational Density of State Studies 53
Combined Inelastic and Quasielastic Neutron Scattering Studies 56
2.2.4 Summary of QENS and INS methods 59
2.3 Time-Resolved Quasielastic and Inelastic Neutron Scattering 60
2.3.1 Time-evolution of Descriptive Parameters Derivedfrom Quasielastic and Inelastic Neutron Scattering Data 60
Fractions from Empirical Diffusion Models of QuasielasticNeutron Scattering Data 61
Parameters from the Relaxing-Cage Model of Quasielastic Neutron Scattering Data 67
Parameters from Inelastic Neutron Scattering 68
2.3.2 Kinetic Models 70
Arrhenius Behaviour 71
Nucleation and Growth 71
Diffusion-Limited Hydration 75
2.3.3 The Kinetics of Cementitious Hydration using Quasiand Inelastic Neutron Scattering: Case Studies 78
Particle-Size Effects 78
Comparison of Cementitious Components 80
Combinations of Cementitious Components 82
Effect of Additives 83
2.4 Conclusions and Outlook 86
References 87
3 Kinetic Properties of Transformations Between Different Amorphous Ice Structures 89
3.1 Introduction 90
3.2 Experimental 93
3.2.1 Sample Preparation and Experimental Procedure 93
3.2.2 Data Treatment 95
3.3 Results 95
3.3.1 Wide Angle Diffraction 95
3.3.2 Small Angle Signal 98
3.4 Discussion 101
3.5 Conclusions 108
References 109
4 Structure Evolution in Materials Studiedby Time-Dependent Neutron Scattering 112
4.1 Introduction 112
4.2 Kinetics of Phase Transformations 113
4.3 Time-Resolved Neutron Scattering Techniques 114
4.3.1 Characteristics Neutron Scattering Techniquesand Measurement Strategies 114
4.3.2 Comparison Neutron and Synchrotron Studies 116
4.4 Neutron and X-ray Studies During Solidificationof Aluminium Alloys 117
4.4.1 Time Resolved Neutron Scattering Experiments 117
4.4.2 Time Resolved X-ray Scattering Experiments 120
4.5 3D Neutron Depolarization Studies 122
4.5.1 Time-Resolved Magnetic Domain Wall Movement 123
4.5.2 Time-Resolved Phase Transformation Kinetics in Steels 125
4.6 Spin-Echo Small-Angle Neutron Scattering 128
4.7 Conclusions and Prospects 131
References 132
5 Applications of In Situ Neutron Diffractionto Optimisation of Novel Materials Synthesis 134
5.1 Brief Review of In Situ Diffractionand MAX Phase Synthesis 135
5.1.1 Introduction to In Situ Diffraction 135
5.1.2 Review of MAX Phases 136
5.2 In situ Neutron Diffraction: Long Time Scales 138
5.2.1 Ti3SiC2 Reactive Sintering Synthesis Mechanism 138
5.2.2 Ti3AlC2 Reactive Sintering Synthesis Mechanism 140
5.2.3 Ti3SiC2 Synthesis Kinetics 141
5.3 In situ Neutron Diffraction: Short Time Scales 143
5.3.1 Ti3SiC2 SHS Synthesis Mechanism 143
5.3.2 In situ Diffraction Differential Thermal Analysis 145
5.4 Designer Processing Routes from In Situ Neutron Diffraction Analysis 146
5.4.1 Inter-Conversion of MAX Phases 146
5.4.2 Intercalation of the A Element into a Crystalline Precursor 147
5.4.3 Lessons Learned 150
5.5 Design of Future In Situ Diffraction Equipment 151
5.5.1 In Situ Diffraction Chamber Design (Institutional) 152
5.5.2 In Situ Reaction Chamber Design (User Inserts) 155
5.5.3 Assembled ISRC Design 156
References 158
6 Time-Resolved, Electric-Field-Induced Domain Switching and Strain in Ferroelectric Ceramics and Crystals 160
6.1 Introduction 160
6.1.1 Piezoelectricity, Ferroelectricity, and Device Applications 160
6.1.2 Time-Resolved Neutron Scattering 163
6.1.3 Stroboscopic Techniques 164
Poke and Probe 165
List Mode 165
6.2 Experimental 165
6.2.1 Materials Under Investigation 165
6.2.2 Instrumentation 166
6.3 Domain Wall Motion in Ferroelectric Ceramics 168
6.3.1 Application of Static Electric Fields 168
6.3.2 Application of Subcoercive, Periodic Electric Fields 170
6.4 Time-Resolved Studies of Lattice Strain in Ferroelectric Ceramics 172
6.5 Domain Switching and Strain in Ferroelectric RelaxorSingle Crystals 175
6.6 Future Opportunities and Outlook for Time-Resolved Scattering of Ferroelectrics 180
6.6.1 Instrumentation Developments 181
6.6.2 Application to other Structures and Phenomena 182
6.6.3 Correlation Between Macroscopic Properties and Diffraction Measurements 183
References 184
7 Time-Resolved Phonons as a Microscopic Probefor Solid State Processes 187
7.1 Introduction 187
7.2 Techniques 188
7.3 Kinetics Between Seconds and Years: Demixing Processes in Simple Systems 191
7.3.1 Basics of Demixing and Phase Diagramsof Silver-Alkali Halides 191
7.3.2 Experimental 194
7.3.3 Nucleation and Growth in KCl–NaCl Mixed Crystals 194
7.3.4 Spinodal Decomposition in AgCl–NaCl Mixed Crystals 194
7.3.5 The Intermediate Case: AgBr–NaBr 204
7.3.5.1 Spinodal Decomposition at Low Temperatures 204
Diffraction and Small Angle Scattering 204
Inelastic Scattering from Phonons in Single Crystals 206
Phonon Density of States from Powder Experiments 210
Nucleation at Elevated Temperature 211
7.4 Kinetics in the Microsecond Regime: Phase Transitions in Ferroelectrics 213
7.4.1 Modulated Ferroelectrics and Softmode Transitions 213
7.4.2 Experimental 214
7.4.3 The Lock-in Transition in K 2SeO4 215
7.4.4 The Ferroelectric Phase in SrTiO3 217
7.5 Concluding Remarks and Future Prospects for Time-Resolved Inelastic Scattering 218
References 220
8 Small Angle Neutron Scattering as a Tool to StudyKinetics of Block Copolymer Micelles 222
8.1 Introduction 222
8.2 Theoretical Background 225
8.2.1 Brief Introduction of Thermodynamics and Scaling Laws 225
8.2.2 Aniansson and Wall Mechanism 226
8.2.3 Scaling Theory – Halperin and Alexander 227
8.2.4 Other Theories 229
8.3 Experimental Background: Small Angle Neutron Scattering 230
8.3.1 Structure with SANS: Core-Shell Model 230
8.3.2 Equilibrium Kinetics and Time Resolved SANS 233
8.4 Results – Equilibrium Micellar Kinetics 235
8.4.1 Low Molecular Weight Surfactant Micelles 235
8.4.2 Block Copolymer Micelles 236
8.4.3 Amphiphilic Diblock Copolymer Micellesin Aqueous Solutions 237
8.4.4 Diblock Copolymer Micelles in Organic Solvents 242
8.4.5 Triblock Copolymer Micelles in Organic Solvents 244
8.5 Concluding Remarks and Outlook 245
References 247
9 Stroboscopic Small Angle Neutron Scattering Investigations of Microsecond Dynamics in Magnetic Nanomaterials 250
9.1 Introduction 250
9.2 Stroboscopic SANS Techniques 251
9.3 Experimental 254
9.4 Scattering Cross-Sections 255
9.5 Results 257
9.5.1 Relaxation of Magnetic Correlations Toward Equilibrium in Cobalt-FF 257
9.5.2 Response on Oscillating Field in ContinuousStroboscopic SANS 261
9.5.3 Response from Pulsed Stroboscopic Technique TISANE 264
9.5.4 Temperature and Frequency Dependence 265
9.5.5 Co-Precipitates in Solid CuCo Alloy 269
9.6 Discussion 270
9.7 Conclusion 271
References 271
Index 273