Insight into the Property Enhancement Mechanism of Chemically Prepared Multi-Main-Phase (Nd,Ce)₂Fe₁₄B

Abstract

Nd 2 Fe 14 B has attracted intensive attention because of its excellent magnetic properties since 1980s. However, large demands for the expensive rare earth (mainly refers to Nd/Pr/Dy) limit its wider applications. Investigations of Ce-doped Nd 2 Fe 14 B have been attempted recently and multimain-phase (MMP) (Nd,Ce) 2 Fe 14 B provides a promising way for the preparation of high-performance Ce-doped permanent magnets even though the inner mechanism has not been absolutely understood. We synthesized Cedoped Nd 2 Fe 14 B nanostructures by the chemical method and successfully realized the obvious property enhancement of the MMP sample compared with that of the single-main-phase one. The coercivity of the MMP nanostructures is nearly 4.5 kOe with a remanence ratio of 0.36 before magnetic orientation, which is much larger than that of the SMP sample (1.7 kOe and 0.21), respectively. The property enhancement mechanism of the MMP sample analyzed mainly by first-order reversal curves could be concluded in three aspects: first, the content of α-Fe will be decreased; hence, the difficulty of the magnetic nucleation is increased. Second, the exchange coupling effect between the adjacent magnetic structures will be strengthened significantly. Last, the grain boundary phases with various magnetic features are formed, enhancing the magnetic pinning effect and specially tuning the inner interactions. This work is helpful for the deeper understanding of the property enhancement mechanism in MMP nanomagnets and provides an instructive way for the effective design and preparation of highperformance MMP Ce-doped Nd 2 Fe 14 B nanomagnets. KEYWORDS: Ce-doped Nd 2 Fe 14 B, chemically prepared, multi-main phase, coercivity enhancement, first-order reversal curves (FORCs)

Nd2Fe14B permanent magnets substituted with non-critical light rare earth elements (Ce, La): A review

“…The gap in coercivity, 11.4 kOe (MMP) vs 10.4 (SMP), is however less pronounced in the work of Zhang et al [27] than in the previous study of Zhu et al [91]. In a very different approach for preparing MMP powders, based on high energy ball milling of RE oxides precursors followed by H2 reduction, Zhu et al [96] obtained, by mixing after reduction Nd-rich and Ce-rich powders, an higher coercive field (HcJ = 4.5 kOe) compared to the case where the oxides precursors were mixed before milling (HcJ = 1.7 kOe).…”

Design of Novel POB/h-BN Co-Filled PTFE Composites with Enhanced Thermal–Mechanical Properties

“…The composite with 25 wt.% POB and 5 wt.% h-BN showed a cross-linked structure with regularly distributed pores, which was further conducive to higher thermal stability and thermal conductivity (see Figure 8f and Table 3). In addition, the h-BN as the second phase possessed the pinning effect of phase boundaries, which enhanced the mechanical properties [43,44]. SEM images of the fracture surface for PTFE composites filled with different h-BN contents are shown in Figure 9.…”