A new method of neodymium-iron-boron magnets/reduced graphene oxide manufacturing without a controlled atmosphere

Abstract

This paper introduces an innovative manufacturing method for NdFeB magnets, involving the integration of reduced graphene oxide (rGO) during mechanical milling (MM) to counteract powder ignition, a common issue in oxygen-rich environments. The NdFeB alloy underwent hydrogen decrepitation before being mechanically milled with varying rGO quantities in ambient air. Raman and X-ray diffraction (XRD) analyses confirmed the successful production of rGO samples with a minimal number of layers. The XRD analysis of the NdFeB/rGO powder demonstrated that all the diffraction peaks corresponded to the Nd2Fe14BH1.86 phase, with no carbides or other carbon compounds detected. Transmission electron microscopy revealed rGO encapsulating the NdFeBrGO particles, while scanning electron microscopy of the resulting magnets (samples 1, 2, and 3) displayed grain sizes ranging from 0.5 µm to 6.8 µm. These manufacturing variations led to a diverse range of magnetic properties: remanence (Br) varied from 0.5 T to 1.13 T, intrinsic coercivity (iHc) ranged from 263.5 kA m−1 to 776.1 kA m−1, and maximum energy product (BHmax) spanned from 21.0 kJ m−3 to 232.3 kJ m−3. Remarkably, the most favorable Br, iHc, and BHmax values were observed in Sample 0.02 wt.% rGO, closely aligning with the characteristics typically found in commercial NdFeB.