Microstructural analysis and development of Nd-Fe-B magnets
Permanent magnets (PM) are critical components for electric motors and power generators. Key properties of permanent magnets, especially coercivity and remanent magnetization, are strongly dependent on microstructure. Understanding metallurgical processing, phase stability and microstructural changes are essential for designing and improving permanent magnets. The widely used PM for the traction motor in electric vehicles and for the power generator in wind turbines contain rare earth elements Nd and Dy due to their high maximum energy product. Dy is used to sustain NdFeB's coercivity at higher temperature. Due to the high supply risk of rare earth elements (REE) such as Dy and Nd, these elements are listed as critical materials by the U.S. Therefore, an effective method to reduce the usage of Dy from the high coercivity (Nd,Dy)-Fe-B permanent magnets must be developed.
We are trying to develop and understand grain boundary diffusion process (GBDP) for high-performance Nd-Fe-B magnets based on microstructural analysis by using SEM/TEM/EBSD/EPMA.
Fundamental behavior of magnetic skyrmions
A skyrmion is a nanoscale vortex-like spin structure with topological charge, and magnetic skyrmions are promising information carriers for spintronic applications. Different mechanisms, such as magnetic dipolar interaction, Dzayaloshinskii−Moriya interaction (DMI), frustrated exchange interaction, and four-spin exchange interactions, have been proposed for their formation. In particular, the skyrmions that generated by DMI has been widely studied, including Ńeel-type skyrmion, Bloch-type skyrmion, etc. The realization of skyrmionic devices will depend on understanding and exploiting the principles that guide skyrmion formation.
We are trying to answer critical questions remain about SkX dynamics, including the effects of external parameters such as external magnetic field, temperature, strain, composition, and electric current.
Rare-earth free Fe16N2 magnets
Several permanent magnet materials have been discovered in recent decades, including those based on rare-earth intermetallic compounds. Since the development in the 1980s of neodymium (Nd) and samarium (Sm) rare-earth magnets, which perform high-flux densities, permanent magnet based electric machines are preferred over induction machines. α″-Fe16N2 has been picked up as one of the most promising rare-earth-free magnet candidates because of its use of environment-friendly raw materials. The iron nitride magnet is of great interest as a magnetic material for applications working at relatively low temperature (< 150 °C) and not requesting high coercivity
We are trying to synthesize iron nitride magnetic powder by using different approaches, and prepare the bulk compounds with microstructural analysis and magnetic property measurement.
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