https://dc.engconfintl.org/cgi/viewcontent.cgi?article=1032&context=superalloys_ii

A critical review of high entropy alloys and related concepts

In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

A new energy paradigm, consisting of greater reliance on renewable energy sources and increased concern for energy effi ciency in the total energy lifecycle, has accelerated research into energy-related technologies. Due to their ubiquity, magnetic materials play an important role in improving the effi ciency and performance of devices in electric power generation, conditioning, conversion, transportation, and other energy-use sectors of the economy. This review focuses on the state-of-the-art hard and soft magnets and magnetocaloric materials, with an emphasis on their optimization for energy applications. Specifi cally, the impact of hard magnets on electric motor and transportation technologies, of soft magnetic materials on electricity generation and conversion technologies, and of magnetocaloric materials for refrigeration technologies, are discussed. The synthesis, characterization, and property evaluation of the materials, with an emphasis on structure‐property relationships, are discussed in the context of their respective markets, as well as their potential impact on energy effi ciency. Finally, considering future bottlenecks in raw materials, options for the recycling of rare-earth intermetallics for hard magnets will be discussed.

/pdf/magnetic-materials-and-devices-for-the-21st-century-stronger-xvi5miqu1p.pdf

Magnetic materials and devices for the 21st century: Stronger, lighter, and more energy efficient

Electrocatalysis will play a key role in future energy conversion and storage technologies, such as water electrolysers, fuel cells and metal-air batteries. Molecular interactions between chemical reactants and the catalytic surface control the activity and efficiency, and hence need to be optimized; however, generalized experimental strategies to do so are scarce. Here we show how lattice strain can be used experimentally to tune the catalytic activity of dealloyed bimetallic nanoparticles for the oxygen-reduction reaction, a key barrier to the application of fuel cells and metal-air batteries. We demonstrate the core-shell structure of the catalyst and clarify the mechanistic origin of its activity. The platinum-rich shell exhibits compressive strain, which results in a shift of the electronic band structure of platinum and weakening chemisorption of oxygenated species. We combine synthesis, measurements and an understanding of strain from theory to generate a reactivity-strain relationship that provides guidelines for tuning electrocatalytic activity.

https://www.unicat.tu-berlin.de/fileadmin/user_upload/MAIN-bilder/UniCat/2_Research/24_Research_Highlights/NCHEM.623s.pdf

Lattice-strain control of the activity in dealloyed core–shell fuel cell catalysts

http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

https://www.andrew.cmu.edu/user/dl0p/laughlin/pdf/PMS.pdf

Amorphous and nanocrystalline materials for applications as soft magnets

The development of Fe73.5Si13.5B9Nb3Cu1 (FINEMET) by Yoshizawa et al. and Fe88Zr7B4Cu1 (NANOPERM) by Inoue et al. have shown that nanocrystalline microstructures can play an important role in the production of materials with outstanding soft magnetic properties. The FINEMET and NANOPERM materials rely on nanocrystalline α-Fe3Si and α-Fe, respectively, for their soft magnetic properties. The magnetic properties of a new class of nanocrystalline magnets are described herein. These alloys with a composition of (Fe,Co)–M–B–Cu (where M=Zr and Hf) are based on the α- and α′-FeCo phases, have been named HITPERM magnets, and offer large magnetic inductions to elevated temperatures. This report focuses on thermomagnetic properties, alternating current (ac) magnetic response, and unambiguous evidence of α′-FeCo as the nanocrystalline ferromagnetic phase, as supported by synchrotron x-ray diffraction. Synchrotron data have distinguished between the HITPERM alloy, with nanocrystallites having a B2 structure from the ...

Structure and magnetic properties of (Fe0.5Co0.5)88Zr7B4Cu1 nanocrystalline alloys

http://www.contrib.andrew.cmu.edu/~dl0p/laughlin/pdf/248.pdf

Nano-scale materials development for future magnetic applications

We have investigated magnetic relaxation on a grain-aligned sample of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} powder embedded in epoxy with the magnetic field along the {ital c} axis. Through a thermal-cycling procedure and through variations in the measuring temperature over the range 10--30 K, we manage to commence magnetic relaxation from a range of values of the magnetization, {ital M}, or current density {ital J}. Analysis of relaxation measurements at a magnetic field of 1.0 T over the temperature range 10--30 K reveals a nonlinear dependence of the effective activation energy {ital U}{sub {ital e}} on {ital M} or {ital J} that is consistent with the logarithmic dependence obtained by Zeldov {ital et} {ital al}. from transport measurements. This demonstration of a nonlinear dependence of {ital U}{sub {ital e}}({ital M}) is capable of resolving anomalies in the magnitudes and temperature dependence of flux-creep activation energies obtained from magnetic-relaxation studies.

Dependence of flux-creep activation energy upon current density in grain-aligned YBa2Cu3O7-x.

This highly readable, popular textbook for upper undergraduates and graduates comprehensively covers the fundamentals of crystallography and symmetry, applying these concepts to a large range of materials. New to this edition are more streamlined coverage of crystallography, additional coverage of magnetic point group symmetry and updated material on extraterrestrial minerals and rocks. New exercises at the end of chapters, plus over 500 additional exercises available online, allow students to check their understanding of key concepts and put into practice what they have learnt. Over 400 illustrations within the text help students visualise crystal structures and more abstract mathematical objects, supporting more difficult topics like point group symmetries. Historical and biographical sections add colour and interest by giving an insight into those who have contributed significantly to the field. Supplementary online material includes password-protected solutions, over 100 crystal structure data files, and Powerpoints of figures from the book.

/pdf/structure-of-materials-an-introduction-to-crystallography-2a0msqayyl.pdf

Michael E. McHenry

Papers

Amorphous and nanocrystalline materials for applications as soft magnets

Structure and magnetic properties of (Fe0.5Co0.5)88Zr7B4Cu1 nanocrystalline alloys

Nano-scale materials development for future magnetic applications

Dependence of flux-creep activation energy upon current density in grain-aligned YBa2Cu3O7-x.

Structure of Materials: An Introduction to Crystallography, Diffraction and Symmetry