Investigation of the body-centred tetragonal structure of Fe–Co–V–N Bulk foils using the rolling and ammonia-gas-nitriding method

Abstract

Improving the properties of permanent magnets is essential for the advancement of electric motors in reducing energy consumption and carbon emissions. This study investigated the effect of V and N addition to FeCo foils on the stability of tetragonally distorted FeCo-based bulk magnets. The incorporation of these two elements stabilised the body-centred tetragonal structure in thin-film and bulk systems. Fe–Co–V ingots were rolled and nitrided by ammonia gas at 650 °C for 5 h. A body-centred tetragonal lattice with an axial ratio of c/a ≈ 1.1 was observed by transmission electron microscopy, and the collected data suggested the induction of a large uniaxial magnetic anisotropy. This study is expected to improve our understanding of rare-earth-free magnets.

Local stabilization of body-centred tetragonal Fe and enhanced dislocation density in carbon nanotubes filled with μm-long nanowires

“…The possible roles of the locally distorted bcc structure ( i.e. local bcc to bct transformation 55,56 ) or of the reduced unit-cell cell dimensions in depleting the overall magnetism of the encapsulated nanowires cannot be excluded. Such a non-equilibrium structural transition evidences a crucial role of (I) the initial phase-composition of the encapsulated nanowire and (2) the highly controllable cooling rates, in allowing for a control of interstitial carbon migration within the fully filled CNTs.…”

Challenge of fabricating difficult-to-nitride materials: Formation of martensitic phase in (Fe0.8Co0.2)8N foil based on industrially suitable gas-nitriding process

“…If our purpose is only to penetrate nitrogen into the FeCo alloy, introducing additional elements that easily bond with nitrogen (for example, vanadium or chromium) may be effective. Hasegawa recently succeeded at synthesizing a bct crystal structure in the quaternary system of Fe-Co-V-N. 19 However, he also observed the formation of V-N compounds, which can be a critical issue from the viewpoint of the practical use of magnetic materials. An effective method needs to be developed to form a martensitic phase in FeCo bulk materials without additional elements toward practical use.…”