Nanotwin-assisted nitridation of quenched FeNi alloy nanopowders for rare-earth-free magnets  

作　　者：Jian Wang Yusuke Hirayama Kazuyuki Suzuki Kwangjae Park Zheng Liu Kenta Takagi Kimihiro Ozaki 

机构地区：[1]Innovative Functional Materials Research Institute,National Institute of Advanced Industrial Science and Technology,4-205,Sakurazaka,Moriyama,Nagoya,463-8560,Japan

出　　处：《Journal of Materials Science & Technology》2023年第34期244-252,共9页材料科学技术（英文版）

摘　　要：L1_(0)-ordered FeNi alloy with a high uniaxial magnetic anisotropy and large magnetic moment is a promising candidate for rare-earth-free permanent magnets applications.However,the synthesis of this chemically ordered phase remains a longstanding challenge because of its low chemical order-disorder transition temperature(200-320℃).Although a non-equilibrium synthetic route based on a nitrogen topotactic reaction has been proposed as a valid approach,the volume fraction and degree of chemical ordering of the product phase are limited.Herein,we propose a promising approach that promotes the efficient formation of L1_(0)-ordered nitride phase in FeNi nanopowders by introducing a quenching treatment during a low-oxygen induction thermal plasma process.The quenched FeNi nanopowders possessed much smaller powder sizes(40.4 vs 74.0 nm),exhibited higher number densities of nanotwins(39.8%vs 24.1%)and formed much larger volume fraction(33.6 wt.%vs 0.6 wt.%)of ordered phase than the unquenched nanopowders.Notably,quenching-induced high-density nanotwins led to the dominant coverage of serrated{001}crystal facets over the surfaces of the FeNi nanopowders.Such unique features substantially accelerated the formation of the L1_(0)-ordered nitride phase in the FeNi nanopowders because the{001}crystallographic orientation had the highest nitrogen diffusivity.This work provides not only a valid synthetic approach for mass production of the L10-ordered nitride phase in FeNi nanopowders but also novel insights into the crystal-defect-assisted nitridation of nanomaterials.

关 键 词：Rare-earth-free Permanent magnet FeNi NITRIDATION Nanotwin 

分 类 号：TG174.4[金属学及工艺—金属表面处理]