阴极析氢对钕铁硼磁体矫顽力和热稳定性的影响

Effect of Cathodic Hydrogen Evolution on the Coercivity and Thermal Stability of Sintered NdFeB Magnets

摘要:

本文研究了由阴极析氢导致的烧结钕铁硼磁体矫顽力和热稳定性下降。使用SQUID-VSM、DSC、XRD、TEM和SEM系统地研究了磁性能，相结构和形貌的变化。阴极析氢后，300 K时矫顽力从13 kOe下降到12.1 kOe。温度系数α从-0.253 %/℃下降到-0.3229 %/℃，β从-0.7518 %/℃下降到-0.7738 %/℃。其作用机制如下：在阴极析氢过程中，部分产生的氢与Nd2Fe14B相和富钕相反应，相应地生成Nd2Fe14BHx和NdHx。生成的NdHx有体积膨胀，导致了晶间裂纹和应力。XRD和微观形貌都确认了这些缺陷的存在。这些缺陷促进了反磁化畴的形核，进而降低了磁体的矫顽力和热稳定性。

Abstract:

The effect of cathodic hydrogen evolution on coercivity and thermal stability had been investigated in sintered NdFeB magnets. The magnetic properties, phase structure and morphology were systematically studied by SQUID-VSM, DSC, XRD, TEM and SEM. After cathodic hydrogen evolution, The Hcj decreased from 13 to 12.1 kOe. The temperature coefficients α declined from -0.253 %/℃ to -0.3229 %/℃, and the β declined from -0.7518 %/℃ to -0.7738 %/℃. A mechanism was proposed to explain the results. In the process of cathodic hydrogen evolution, parts of the generated hydrogen atoms reacted with the Nd2Fe14B phase and Nd-rich phase, formed Nd2Fe14BHx and NdHx, respectively. The formation of NdHx caused a volume expansion. Which resulted in intergranular cracks and stress. X-ray diffraction and morphology characterization confirmed the presence of these defects. These defects would significantly promote the nucleation of reverse magnetic domains, and further declined the coercivity and thermal stability of magnets.