Magnetics and the Critical Materials Challenge: An FMD Symposium Honoring Matthew J. Kramer: On-Demand Oral Presentations
Sponsored by: TMS Functional Materials Division, TMS: Magnetic Materials Committee
Program Organizers: Scott McCall, Lawrence Livermore National Laboratory; Ryan Ott, Ames Laboratory
Monday 8:00 AM
March 14, 2022
Room: Energy & Environment (including REWAS 2022 Symposia)
Location: On-Demand Room
Synthesis and Stabilization of Magnetic Nanoparticles of Rare-earth Metal Alloys: Shouheng Sun1; 1Brown University
We report our recent studies on the synthesis and stabilization of strongly ferromagnetic NPs of REM alloys of SmCo and SmFeN. Our synthesis started with the preparation of composite NPs of CoO + Sm2O3 (denoted as SmCo-O) within one nanostructure. These SmCo-O NPs were then coated with polydopamine (PDA) and thermally annealed to convert the PDA to N-doped graphitic carbon (NGC). The SmCo-O/NGC NPs were further reduced by Ca at 850°C to give SmCo5/NGC NPs. The 10 nm NGC coating efficiently stabilized the SmCo5 NPs against air oxidation: the magnetic moment of the 180 nm SmCo5/NGC NPs was stabilized at 86.1 emu/g after their air exposure at room temperature for five days, and their Hc reached 51 kOe at 150 K and 22 kOe at 330 K. The method could be easily extended to synthesize Sm2Co17 NPs and Sm2Fe17N3 NPs.
Magnetoelastic Interactions Reduce Hysteresis in Soft Magnets: Negar Ahani1; A. Renuka Balakrishna1; 1University of Southern California
Soft magnets have the smallest coercivity compared to all magnets, which makes them well-suited for energy conversions, such as in rapid power-conversion electronics, induction motors for electric vehicles, and spintronics devices. More recently, soft magnets have been emerging as potential candidates for sustainable energy conversion, however, we do not have a systematic strategy to discover novel soft magnets with drastically reduced coercivities. In today's talk, I will discuss how the material's fundamental elastic stiffness constants and the residual stresses can be engineered to assist magnetization reversal and thus dramatically reduce coercivity. We use a theoretical framework based on micromagnetics to show that magnetoelastic interactions control both the shape and size of hysteresis loops. Our findings provide fundamental insights into the origins of magnetic hysteresis and propose a quantitative relationship to guide alloy development.
HDDR Treatment on Nd2Fe14B-based Magnets in the Presence of an Applied Magnetic Field: Zachary Tener1; Xubo Liu2; Ikenna Nlebedim2; Matthew Kramer2; Michael McGuire1; Michael Kesler1; 1Oak Ridge National Laboratory; 2Ames Laboratory
The purpose of this is study is to investigate the effects of thermomagnetic processing on the established HDDR method of producing Nd2Fe14B anisotropic powders towards improving the energy product of bonded magnetic materials. Samples from a drop cast ingot were subjected to controlled H2 gas pressure in 0, 1, and 2 T applied magnetic fields to investigate the effect of H2 pressure on hydrogenation disproportionation (HD) in the presence of a magnetic field. This was followed by the desorption and recombination (DR) steps, under the previously stated magnetic fields. Between the HD and DR steps, samples were characterized using X-ray diffraction and magnetometry measurements to gauge improvements to phase fraction, magnetization, and magnetic coercivity caused by thermomagnetic processing.This work is supported by the Critical Materials Institute, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office.