Modern Permanent Magnets (Woodhead Publishing Series in Electronic and Optical Materials)

Description

Modern Permanent Magnets provides an update on the status and recent technical developments that have occurred in the various families of permanent magnets produced today. The book gives an overview of the key advances of permanent magnet materials that have occurred in the last twenty years. Sections cover the history of permanent magnets, their fundamental properties, an overview of the important families of permanent magnets, coatings used to protect permanent magnets and the various tests used to confirm specifications are discussed. Finally, the major applications for each family of permanent magnets and the size of the market is provided. The book also includes an Appendix that provides a Glossary of Magnetic Terms to assist the readers in better understanding the technical terms used in other chapters. This book is an ideal resource for materials scientists and engineers working in academia and industry R&D. Front cover Half title Full title Copyright Contents Contributors 1 - The history of permanent ­magnets 1.1 Introduction 1.2 Lodestones: the first permanent magnets 1.3 Early permanent magnet studies 1.4 The era of steel permanent magnets 1.5 The discovery of alnico permanent magnets 1.6 The discovery of hard ferrite magnets 1.7 The discovery of Sm-Co permanent magnets 1.8 The discovery of NdFeB permanent magnets 1.9 The discovery of Sm-Fe-N permanent magnets 1.10 Future permanent magnet materials 1.11 Summary References 2 - Fundamental properties of permanent magnets 2.1 Introduction 2.2 The different families and types of permanent magnets 2.3 Key magnetic parameters 2.4 On the origin of magnetism 2.5 The different types of magnetism 2.6 The origin of anisotropy in permanent magnets 2.7 Magnetic domains and domain walls 2.8 Magnetic hysteresis 2.9 Coercivity mechanism in modern permanent magnets 2.10 Stability of permanent magnets References 3 - Recent advances in hard ­ferrite magnets 3.1 Introduction 3.2 Historical overview of M-type Sr- and Ba- Hexaferrites 3.3 Crystal structure, intrinsic magnetic properties, microstructure and morphology 3.4 Advances towards the improvement of intrinsic magnetic properties 3.5 Industrial fabrication routes 3.5.1 Fabrication of hexaferrites 3.5.2 Bonded magnets 3.5.3 Sintered magnets 3.5.4 Additive manufacturing 3.6 Recycling efforts, recovery, and reusability in production line 3.7 Applications of hexaferrites: present and perspectives References 4 - Modern Sm-Co permanent magnets 4.1 Introduction 4.2 Manufacturing process of Sm-Co magnets 4.3 High (BH)max Sm2Co17 type permanent magnets 4.4 Temperature compensated Sm-Co magnets 4.5 Ultra-high temperature Sm-Co magnets with small reversible temperature coefficient of Br 4.6 Performance of Sm-Co magnets in special environments 4.7 Laminated Sm-Co magnets 4.8 Additive manufacturing 4.9 Small magnets 4.10 Sm-Co nanoparticles and nanoflakes for nanocomposite magnets 4.11 Summary References 5 - The status of sintered NdFeB magnets 5.1 Introduction 5.2 History of the development of Nd-Fe-B 5.2.1 How did the idea of NdFeB sintered magnets come about? 5.2.2 How were the NdFeB sintered magnets developed? 5.2.3 How was the discovery of NdFeB sintered magnets presented? 5.3 Compositions of the NdFeB sintered magnets and their magnetic properties 5.4 Production process for sintered NdFeB magnets 5.4.1 Preparation of raw material alloys (strip-casting method) 5.4.2 Hydrogen decrepitation (HD) 5.4.3 Jet milling 5.4.4 Application of lubricant to the powder surface 5.4.5 Magnetic field pressing 5.4.6 Sintering 5.4.7 Heat treatment 5.4.8 Machining 5.4.9 Surface treatment 5.4.10 Magnetization 5.5 Progress in the microstructure investigation 5.6 Development of HRE-Free and reduced HRE magnets 5.6.1 Development of the powder-blend method 5.6.2 Development of grain boundary diffusion process 5.6.3 Ga-doped NdFeB sintered magnets 5.6.4 Grain size refinement 5.7 Ultimate NdFeB sintered magnets for EV traction motors References 6 - Compression bonded NdFeB permanent magnets 6.1 Introduction 6.2 The compression molding process 6.3 Isotropic compression bonded NdFeB permanent magnets 6.4 Anisotropic hot deformed NdFeB compression bonded magnets 6.5 Compression molded HDDR permanent magnets References 7 - Injection molded permanent magnets 7.1 Introduction 7.2 Overview of applications, basic parameters and materials 7.3 Manufacturing 7.4 Polarization patterns 7.5 Design of in-mold magnetized magnets 7.6 Design of pulse magnetized magnets 7.7 Applications - Sensors 7.8 Applications – Electrical machines 7.9 Summary Acknowledgments References 8 - Hot formed NdFeB magnets 8.1 Introduction 8.2 Development of hot-formed Nd-Fe-B magnets 8.2.1 Previous examples of magnets made by plastic deformation 8.2.2 Invention of rapidly quenched Nd-Fe-B and application of hot deformation 8.2.3 Early studies and commercialization efforts 8.2.3.1 MQ2 and MQ3 (die-upset) commercialization efforts 8.2.3.2 Mode of deformation and alignment directions 8.2.3.3 Cast and rolled Pr-Fe-B 8.2.4 Commercialization of hot-deformed Nd-Fe-B magnets 8.2.4.1 Starting powders 8.2.4.2 Densification of rapidly quenched powders 8.2.4.3 Hot workability 8.2.4.4 Development of radially oriented rings 8.2.4.5 Rare-earth crisis and need for HREE-free magnets 8.2.4.6 Development of axially oriented plates 8.3 Characteristics of hot-deformed Nd-Fe-B magnets 8.3.1 Basic properties 8.3.2 Comparison with sintered Nd-Fe-B 8.3.2.1 Microstructure 8.3.2.2 Coercivity and thermal stability 8.3.2.3 Initial magnetization and minor loops 8.3.2.4 Corrosion resistance 8.3.2.5 Producibility 8.4 Fundamental research 8.4.1 Alignment mechanism 8.4.2 Coercivity mechanism 8.4.3 Grain boundary analyses and modification 8.4.4 Other notable research 8.5 Applications 8.5.1 Radially oriented rings 8.5.1.1 FA (Factory automation) servo motors 8.5.1.2 EPS (Electric power steering) 8.5.1.3 Assembly, magnetizing, banding 8.5.2 Axially oriented plates 8.5.2.1 EV/HEV traction motors 8.6 Future outlook 8.6.1 Addressing resource and cost issues 8.6.2 Higher magnetic properties 8.6.3 Improvement of electrical resistance 8.6.4 Flexible shape extrusions 8.7 Concluding remarks Acknowledgments References 9 - Bonded Sm-Fe-N permanent magnets 9.1 Introduction 9.2 Interstitial modification 9.3 Basic characteristics of Sm-Fe-N compounds 9.3.1 Crystal structure 9.3.2 Intrinsic magnetic properties 9.3.3 Dense Sm-Fe-N magnets 9.4 Magnet processing 9.4.1 Sm-Fe-N powder 9.4.1.1 Anisotropic Sm2Fe17N3 powder 9.4.1.2 Isotropic SmFe7-9N powder 9.4.2 Production processes for bonded magnets 9.4.3 Magnetic properties of bonded magnets 9.5 Applications 9.5.1 Features of bonded Sm-Fe-N magnets 9.5.2 Application examples 9.6 Conclusion Acknowledgments References 10 - Critical materials for permanent magnets 10.1 Introduction 10.2 What is a critical material? 10.3 Critical materials in permanent magnets 10.3.1 Growth of the market 10.3.2 The rare earth elements: a general introduction to their science and technology 10.3.3 Samarium-Cobalt 10.3.3.1 Criticality of samarium 10.3.3.2 Criticality of cobalt 10.3.4 Neodymium-Iron-Boron 10.3.4.1 Criticality of neodymium and praseodymium 10.3.4.2 Criticality of dysprosium, terbium and holmium 10.4 Effects of criticality on technology evolution, and vice versa 10.4.1 Conventional vehicles 10.4.2 Electric vehicles 10.4.3 Wind power 10.5 Source diversification 10.5.1 Samarium 10.5.2 Cobalt 10.5.3 Neodymium and praseodymium 10.5.4 Dysprosium, terbium and holmium 10.6 Substitution 10.6.1 Technology substitutions 10.6.1.1 LEDs vs fluorescent lamps, and their impact on magnet materials 10.6.2 Material substitutions 10.6.2.1 Using Nd-Fe-B in place of Sm-Co after the cobalt crisis 10.6.2.2 Element substitutions within Nd-Fe-B 10.6.2.3 Praseodymium and neodymium 10.6.2.4 Terbium, dysprosium and holmium 10.6.2.5 Substitutes for the Nd-Fe-B family of alloys 10.6.2.6 Superconducting magnets 10.6.2.7 Gap magnets 10.6.2.8 Using Sm-Co in place of Nd-Fe-B 10.6.2.9 3-D printing of magnets 10.7 Summary Acknowledgments References 11 - Permanent magnet coatings and testing procedures 11.1 Introduction 11.2 Magnet characteristics relevant to coating 11.2.1 Alnico 11.2.2 Ferrite 11.2.3 Samarium cobalt 11.2.4 Neodymium iron boron 11.2.5 Samarium iron nitride (SmFeN) 11.2.6 Bonded magnets 11.3 Coating permanent magnets 11.3.1 Surface preparation 11.3.2 Conversion coatings 11.3.3 Organic coatings 11.3.4 Parylene 11.3.5 Metallic plating 11.3.6 Aluminum ion vapor deposition (IVD) 11.3.7 Combination coatings 11.4 Coating test and evaluation 11.4.1 Temperatuire and humidity test 11.4.2 Autoclave (hygrothermal) test 11.4.3 Salt spray (fog) test 11.4.4 Other tests 11.5 Summary References 12 - Permanent magnet markets and applications 12.1 Introduction 12.2 Permanent magnet materials 12.3 Applications and markets 12.4 Price/Performance ratio for permanent magnet types – niche and mass market magnet materials 12.5 Current and future major applications and devices (Constantinides, 2021; Benecki et al., 2021) 12.5.1 Permanent magnet motors 12.5.2 Types of motors 12.5.3 Motor efficiency 12.5.4 Motor size and diversity 12.5.5 Information storage: computer hard disk and optical storage drives 12.5.6 Industrial and general use motors 12.5.7 Permanent magnets in transportation 12.5.8 Hybrid and electrical vehicles 12.5.9 Electric vehicle traction drive motors 12.5.10 Electric bicycles (E-bikes) 12.5.11 Acoustic transducers 12.5.12 Wind power 12.5.13 Magnetic sensors 12.5.14 MRI 12.5.15 Magnetic separation 12.5.16 Advertising and promotional 12.5.17 Magnetically levitated transportation 12.5.18 Reprographics 12.5.19 Magnetically-Coupled drives 12.5.20 Torque-coupled drives 12.5.21 Eddy current coupled devices 12.5.22 Hysteresis coupling 12.5.23 HVAC 12.5.24 Elevators 12.5.25 Solenoids, relays, switches 12.5.26 Wave guides, TWT, undulators & wigglers 12.5.27 Undulators & wigglers 12.5.28 TWTs 12.5.29 Wave guides 12.5.30 Miscellaneous References Web link Glossary of Magnetic Terms Index Back cover