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Recent Advances in Additive Manufacturing of Soft Magnetic Materials: A Review
Additive manufacturing (AM) is an attractive set of processes that are being employed lately to process specific materials used in the fabrication of electrical machine components. This is because AM allows for the preservation or enhancement of their magnetic properties, which may be degraded or limited when manufactured using other traditional processes. Soft magnetic materials (SMMs), such as Fe–Si, Fe–Ni, Fe–Co, and soft magnetic composites (SMCs), are suitable materials for electrical machine additive manufacturing components due to their magnetic, thermal, mechanical, and electrical properties. In addition to these, it has been observed in the literature that other alloys, such as soft ferrites, are difficult to process due to their low magnetization and brittleness. However, thanks to additive manufacturing, it is possible to leverage their high electrical resistivity to make them alternative candidates for applications in electrical machine components. It is important to highlight the significant progress in the field of materials science, which has enabled the development of novel materials such as high-entropy alloys (HEAs). These alloys, due to their complex chemical composition, can exhibit soft magnetic properties. The aim of the present work is to provide a critical review of the state-of-the-art SMMs manufactured through different AM technologies. This review covers the influence of these technologies on microstructural changes, mechanical strengths, post-processing, and magnetic parameters such as saturation magnetization (MS), coercivity (HC), remanence (Br), relative permeability (Mr), electrical resistivity (r), and thermal conductivity (k).
Journal Article
Additive Manufacturing and Topology Optimization of Magnetic Materials for Electrical Machines—A Review
Additive manufacturing has many advantages over traditional manufacturing methods and has been increasingly used in medical, aerospace, and automotive applications. The flexibility of additive manufacturing technologies to fabricate complex geometries from copper, polymer, and ferrous materials presents unique opportunities for new design concepts and improved machine power density without significantly increasing production and prototyping cost. Topology optimization investigates the optimal distribution of single or multiple materials within a defined design space, and can lead to unique geometries not realizable with conventional optimization techniques. As an enabling technology, additive manufacturing provides an opportunity for machine designers to overcome the current manufacturing limitation that inhibit adoption of topology optimization. Successful integration of additive manufacturing and topology optimization for fabricating magnetic components for electrical machines can enable new tools for electrical machine designers. This article presents a comprehensive review of the latest achievements in the application of additive manufacturing, topology optimization, and their integration for electrical machines and their magnetic components.
Journal Article
Energy investment needs for fulfilling the Paris Agreement and achieving the Sustainable Development Goals
Low-carbon investments are necessary for driving the energy system transformation that is called for by both the Paris Agreement and Sustainable Development Goals. Improving understanding of the scale and nature of these investments under diverging technology and policy futures is therefore of great importance to decision makers. Here, using six global modelling frameworks, we show that the pronounced reallocation of the investment portfolio required to transform the energy system will not be initiated by the current suite of countries’ Nationally Determined Contributions. Charting a course toward ‘well below 2 °C’ instead sees low-carbon investments overtaking fossil investments globally by around 2025 or before and growing thereafter. Pursuing the 1.5 °C target demands a marked upscaling in low-carbon capital beyond that of a 2 °C-consistent future. Actions consistent with an energy transformation would increase the costs of achieving the goals of energy access and food security, but reduce the costs of achieving air-quality goals.
The scale and nature of energy investments under diverging technology and policy futures is of great importance to decision makers. Here, a multi-model study projects investment needs under countries’ nationally determined contributions and in pathways consistent with achieving the 2 °C and 1.5 °C targets as well as certain SDGs.
Journal Article
Spin-Crossover Materials
The phenomenon of spin-crossover has a large impact on the physical properties of a solid material, including its colour, magnetic moment, and electrical resistance. Some materials also show a structural phase change during the transition. Several practical applications of spin-crossover materials have been demonstrated including display and memory devices, electrical and electroluminescent devices, and MRI contrast agents. Switchable liquid crystals, nanoparticles, and thin films of spin-crossover materials have also been achieved.
Spin-Crossover Materials: Properties and Applications presents a comprehensivesurvey of recent developments in spin-crossover research, highlighting the multidisciplinary nature of this rapidly expanding field. Following an introductory chapter which describes the spin-crossover phenomenon and historical development of the field, the book goes on to cover a wide range of topics including
* Spin-crossover in mononuclear, polynuclear and polymeric complexes
* Structure: function relationships in molecular spin-crossover materials
* Charge-transfer-induced spin-transitions
* Reversible spin-pairing in crystalline organic radicals
* Spin-state switching in solution
* Spin-crossover compounds in multifunctional switchable materials and nanotechnology
* Physical and theoretical methods for studying spin-crossover materials
Spin-Crossover Materials: Properties and Applications is a valuable resource for academic researchers working in the field of spin-crossover materials and topics related to crystal engineering, solid state chemistry and physics, and molecular materials. Postgraduate students will also find this book useful as a comprehensive introduction to the field.
eBook
Composite Magnetoelectrics - Materials, Structures, and Applications
This book gives the reader a summary of the theory behind magnetoelectric phenomena, later introducing magnetoelectric materials and structures and the techniques used to fabricate and characterize them. Part two of the book looks at magnetoelectric devices. Applications include magnetic and current sensors, transducers for energy harvesting, microwave and millimeter wave devices, miniature antennas and medical imaging. The final chapter discusses progress towards magnetoelectric memory.
eBook
Microstructure and magnetic properties of NdFe/MgO(001) thin films elaborated by evaporation from Nd3Fe29 nanocrystalline powder
Rare earth (R) and transition metal (T) based films are potential magnetic materials for a variety of applications. However, their structural and magnetic behavior is sensitive to growth and processing parameters. This article presents a comprehensive investigation aiming to analyze the microstructure and magnetic properties of NdFe/MgO(001) films. These films were fabricated by evaporating nanocrystalline Nd3Fe29 powder at different thicknesses (t) and subjected to various heat treatments (Ta). The main objective of this research is to gain a detailed understanding of how the structural and magnetic behavior evolves based on these parameters, which had not been achieved previously. X-ray diffraction analysis was employed to determine the crystalline structure of NdFe/MgO(001) films and to track the grain size evolution with film thickness. Scanning electron microscopy (SEM) and magnetic force microscopy (MFM) images were used to directly visualize magnetic domains and the arrangement of magnetic grains at different thicknesses. Ferromagnetic resonance (FMR) measurements revealed significant variations in resonance fields and easy axes depending on film thickness and heat treatments. The study also examined how magnetic properties such as saturation magnetization (Ms) and coercivity (Hc) are closely related to grain size, magnetic domain organization, and heat treatments. Our research produced remarkable results, especially concerning a 250 nm thick NdFe/MgO(001) film annealed at 873 K, which exhibited outstanding properties. These properties include a robust coercivity of 5230 Oe, a substantial remanent magnetization of 211 emu/cm
3
, a magnetic anisotropy field of 10,325 Oe, a saturation magnetization (Ms) of 396 emu/cm
3
, and a Curie temperature of approximately 388 K. It’s noteworthy that this film possesses an easy magnetization axis parallel to the film plane (HFMR(∥) = 9125 Oe > HFMR(⊥) = 5897 Oe). Although the study provides valuable insights for the design and optimization of magnetic materials for various technological applications in the field of magnetism, its limitation should be acknowledged. The research did not deeply explore the correlations between the different studied properties, leaving a gap in our overall understanding of these characteristics. Therefore, future work will focus on conducting simulations and theoretical modeling to address this research gap.
Journal Article
Effect of Magnetic Properties of Magnetic Composite Tapes on Motor Losses
Alternating current (AC) copper losses in motors increase with carrier frequency of the pulse width modulation (PWM) and are further increased by leakage flux of the permanent magnet. Therefore, AC copper losses increase with motor speed. Conventional techniques for reducing AC copper losses tend to increase other losses. In this paper, AC copper loss was reduced by wrapping a magnetic tape made of a magnetic composite material around the winding. This method controlled the flux path through the winding. Magnetic composite materials are mixtures of magnetic powders and liquid resins whose magnetic properties can be manipulated by changing the combination and other factors. When Fe–Si–Al magnetic tape was wrapped around the winding, the AC copper loss was reduced by 40%. The loss was further reduced by optimizing the magnetic properties of the magnetic composite material. The AC copper loss was maximally reduced when the specific permeability was 100 and the saturation flux density was 1.6. Magnetic tapes composed of magnetic composite materials with high saturation flux density and specific permeability reduce the AC copper losses without increasing other losses in the motor.
Journal Article
Magnetic Properties of Silicon Steel after Plastic Deformation
The energy efficiency of electric machines can be improved by optimizing their manufacturing process. During the manufacturing of ferromagnetic cores, silicon steel sheets are cut and stacked. This process introduces large stresses near cutting edges. The steel near cutting edges is in a plastically deformed stress state without external mechanical load. The magnetic properties of the steel in this stress state are investigated using a custom magnetomechanical measurement setup, stress strain measurements, electrical resistance measurements, and transmission electron microscopic (TEM) measurements. Analysis of the core energy losses is done by means of the loss separation technique. The silicon steel used in this paper is non-grain oriented (NGO) steel grade M270-35A. Three differently cut sets of M270-35A are investigated, which differ in the direction they are cut with respect to the rolling direction. The effect of sample deformation was measured—both before and after mechanical load release—on the magnetization curve and total core energy losses. It is known that the magnetic properties dramatically degrade with increasing sample deformation under mechanical load. In this paper, it was found that when the mechanical load is released, the magnetic properties degrade even further. Loss separation analysis has shown that the hysteresis loss is the main contributor to the additional core losses due to sample deformation. Releasing the mechanical load increased the hysteresis loss up to 270% at 10.4% pre-release strain. At this level of strain, the relative magnetic permeability decreased up to 45% after mechanical load release. Manufacturing processes that introduce plastic deformation are detrimental to the local magnetic material properties.
Journal Article