Graphene Nanoplatelets as Novel Additive to Enhance Coercivity of Hot‐Deformed Magnets by Tuning Microstructures

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AbstractIn this work an effective approach of tuning the microstructures and enhancing the coercivity of hot‐deformed Nd‐Fe‐B magnets without obvious remanence loss by adding graphene nanoplatelets (GNPs) is proposed. Based on the microstructure characterization, the adjacent Nd2Fe14B grains on the interfaces are in polygonal shape with the small grain size less than 100 nm, and the GNPs are mainly around the interfaces of the melt‐spun ribbons. Due to the outstanding mechanical, electrical, and thermal properties, the GNPs can act as the steric hindrance additives and thermal conducting medium, which is helpful to restrain the growth of Nd2Fe14B grains effectively and decrease or even eliminate the coarse grains region. As a result, the coercivity of hot‐deformed Nd‐Fe‐B magnets is enhanced remarkably with their refined microstructure; the coercivity is substantially improved by 33.2% from 785 to 1046 kA m−1 with the GNPs additive amount from 0 to 0.2 wt%, while the remanence loss is also as low as 1.56% from 1.28 to 1.26 T. This work reported here suggests that the GNPs have great potentials in fabricating materials with controlled grain growth properties.