Functional High Entropy Alloys and Compounds

Contributors vii

Foreword ix

Preface xi

1 High-Entropy Alloys and Compounds: Fundamentals 1

1.1 Introduction (Historical Background and Development) 1

1.2 Definition of HEAs and Compounds 3

1.3 Characteristics, Structures, Phase Transformations, and Microstructures 6

1.3.1 Characteristics of HEAs and Compounds 7

1.3.2 Crystal Structures of HEAs and Compounds 12

1.3.3 Phase Transformations in HEAs and Compounds 14

1.3.4 Microstructures of HEAs and Compounds 18

1.4 Diverse Applications of Functional HEAs and Compounds 25

References 34

2 Extreme Conditions and Novel Structure Design 43

2.1 Introduction to Extreme Conditions and Harsh Requirements 43

2.2 HEMs for Extreme Temperatures 44

2.2.1 The Application of HEM at High Temperatures 44

2.2.2 The Application of HEMs at Low Temperatures 48

2.3 HEMs Sustain Under Strong Irradiations 52

2.3.1 Anti-Irradiation Mechanism of HEAs 53

2.3.2 Evolution of Microstructure and Defects 57

2.3.3 Mechanical Changes Caused by Irradiation 61

2.3.4 High-Entropy Ceramics 62

2.4 Fiber and Single-Crystal HEMs 64

2.4.1 HEA Fibers 64

2.4.2 Single-Crystal HEA 69

References 71

3 Corrosion and Antioxidation 75

3.1 Introduction to Corrosion and Antioxidation Scenario 75

3.2 Anticorrosion Design in High-Entropy Materials 77

3.2.1 Effect of Alloying Elements 78

3.2.2 Effect of Processing 81

3.3 High-Temperature Oxidation Resistance 82

3.3.1 Oxidation Mechanism 84

3.3.2 Influencing Factors 88

References 93

4 Additive Manufacturing and Phase Control 97

4.1 Introduction to Additive Manufacturing Technologies 97

4.2 3D Printing of High-Entropy Materials 101

4.2.1 Introduction of HEAs for 3D Printing 101

4.2.2 Classification of HEAs for 3D Printing 102

4.3 Shape Design and Phase Control in High-Entropy Materials by 3D Printing 103

4.3.1 Phase Structure of HEAs 103

4.3.2 The Influence of Printing Parameters on the Phase Structure 104

4.3.3 Effect of Alloying Elements on Phase Structure 105

4.3.4 Research Progress on Additive Production of HEAs 106

4.4 Applications of 3D Printed High-Entropy Materials 114

4.4.1 Energy Industry 114

4.4.2 Aerospace Industry 115

4.4.3 Nuclear Application 116

4.4.4 Medical Applications 117

4.4.5 Coating Application 118

References 118

5 Functional Properties: Thermal, Electric, Magnetic, and Optics 129

5.1 Introduction to Functional Properties and Applications 129

5.2 Thermal and Electronic Properties in HEMs 130

5.2.1 Thermal Conduction in HEMs 130

5.2.2 Superconducting in High-Entropy Materials 132

5.2.3 High-Entropy Materials for Thermoelectric Applications 134

5.2.4 Conclusion 138

5.3 Magnetic and Optical Properties in HEMs 139

5.3.1 Magnetic Properties in High-Entropy Materials 139

5.3.2 Optical Properties in High-Entropy Materials 142

5.3.3 High-Entropy Materials for Optoelectronic Applications 145

5.3.4 Conclusion 149

5.4 Materials Design for Functional Applications 150

5.4.1 Microstructure Regulation 151

5.4.2 Machine Learning-Assisted Design 156

References 162

6 Nanoscale High-Entropy Materials 165

6.1 Introduction to Evolution from Bulk to Nanoscale HEMs 165

6.2 Synthesis and Advanced Characterization 166

6.2.1 Top-Down Method 167

6.2.2 Bottom-Up Method 170

6.2.3 Perspectives for HEM Synthesis 172

6.3 Diverse Applications of Nanoscale HEMs 174

6.3.1 HEMs as Electrocatalysts 174

6.3.2 Nano-HEAs as an Irradiation-Resistant Structural Material 177

6.3.3 Nano-HEAs for Solid Hydrogen Storage Properties 179

6.3.4 Nano-HEAs for Biomedical Fields 180

6.4 Emerging Nano-HEAs 182

References 182

7 High-Entropy Materials for Thermal-Catalytic Applications 193

7.1 Introduction to Thermal Catalysis and Important Concepts 193

7.1.1 Definition and Background 193

7.1.2 The Role of Catalysts in Thermal Reactions 194

7.1.3 Thermodynamics and Kinetics in Catalysis 195

7.1.4 Catalyst Activation and Deactivation 196

7.1.5 Selectivity and Activity in Thermal Catalysis 198

7.2 Catalysts Evolution to HEMs 200

7.2.1 Transition from Single-Component to Multicomponent Catalysts 200

7.2.2 Strategies to Stabilize High-Entropy Catalysts 201

7.3 Typical Reactions and Their High-Entropy Catalysts 203

7.3.1 Hydrotreatment Reactions 203

7.3.2 Oxidation and Ammoxidation 206

7.3.3 Dehydrogenation and Decomposition Reaction 210

7.3.4 Catalyst Performance Comparison 214

7.4 Understanding of High-Entropy Catalysts 215

7.4.1 Structural Characteristics Influencing Catalysis 215

7.4.2 Electronic Effects and Ligand Effects 217

7.4.3 Entropy’s Role in Stabilizing Catalytic Active Phases 219

7.4.4 Mechanistic Insights Through Theoretical Calculations and Spectroscopy 221

7.4.5 Designing HEA Catalysts for Specific Reactions 221

References 223

8 Clean Energy and Electrocatalysis 227

8.1 Introduction to Electrocatalysis and Its Importance 227

8.2 Application of High-Entropy Alloys in Key Reactions of Electrocatalysis 227

8.3 Advanced Ex/In Situ Characterization Techniques 234

8.3.1 Electron Spectroscopy 242

8.4 High-Throughput and Data-Driven Techniques in High-Entropy Catalyst Development 244

References 248

9 High-Entropy Materials for Energy Storage Applications 253

9.1 Introduction to High-Entropy Materials for Battery Applications 253

9.2 High-Entropy Anode Materials 254

9.3 High-Entropy Cathode Materials 258

9.4 High-Entropy Solid-State Electrolytes 263

9.4.1 High-Entropy Oxide Solid-State Electrolytes 264

9.4.2 High-Entropy Sulfide Solid-State Electrolytes 268

9.4.3 High-Entropy Halide Solid-State Electrolytes 271

9.5 High-Entropy Liquid Electrolytes 273

9.6 Perspectives on High-Entropy Battery Materials 274

References 277

10 Future Trends and Concluding Regards 283

10.1 Key Challenges Presented in Functional High-Entropy Alloy and Compounds 283

10.1.1 Synthesis Challenges 283

10.1.2 Characterization Challenges 285

10.1.3 Theoretical Challenges 287

10.1.4 Application Challenges 290

10.2 Future Development of Functional HEA and Compounds 292

10.2.1 High-Throughput Exploration of ML 293

10.2.2 Statistical Methods 293

10.2.3 Artificial Neuron Networks 295

10.3 Concluding Regards: Materials Evolution from Simple to a Complex Yet Fruitful Future 297

References 297

Index 301