Cr含量对NdFeB材料微波吸收特性的影响

Effect of Cr Content on Microwave Absorbing Properties of NdFeB Materials

采用高能球磨和在微氧化气氛晶化热处理的方法制备钕铁硼吸波粉体,借助X射线衍射仪和微波矢量网络分析仪测量系统分析,研究Cr含量对钕铁硼粉体组织结构和微波吸收特性的影响。结果发现:高能球磨和微氧化气氛下进行600℃×2 h晶化处理后Nd11.76 Fe82.35 B5.88粉体组织由α-Fe,Nd2O3,Fe23(B.C)6相组成,加入Cr不改变NdFeB粉体的相组成,但可使粉体中的Fe23(B.C)6相对量减少,而α-Fe相对量增加;加入Cr可降低NdFeB粉体的复介电常数实部ε'和虚部ε″以及复磁导率实部μ',尤其是Nd26.67Fe69.83Cr2.5B粉体的复介电常数虚部ε″降低得最多,加入Cr使NdFeB粉体的复磁导率虚部μ″在4～10 GHz频段时增大,而大于10 GHz频率后,复磁导率虚部μ″变化不大;吸波涂层厚度为1.5 mm时,Nd11.76Fe82.35B5.88粉体的反射率最小值约为-8.5 dB,吸收峰频率约为10 GHz;Nd26.67Fe69.83Cr2.5B反射率最小值降低到-17.0 dB,吸收峰频率升高到15.5 GHz,当将Cr含量增加到4%时,粉体的反射率最小值回升到-10.8 dB,吸收峰频率升高到15.8GHz;加入Cr会使NdFeB粉体的吸波带宽变窄。

The NdFeB absorbing powders was prepared by methods of high energy ball milling and crystallization heat treatment under the partial oxidization atmosphere.Effects of Cr content on the structure and microwave absorbing properties of NdFeB powders were studied with X-ray diffraction and microwave vector network analyzer.The results showed that Nd11.76Fe82.35B5.88 powders under crystallization at 600 ℃ for 2 h were consisted of α-Fe,Nd2O3 and Fe23（B.C）6 phases.The addition of Cr,which reduced Fe23（B.C）6 phase and increased α-Fe phase without changing the phase composition of NdFeB powder,resulted in the decrease of the real part μ′ of complex magnetic conductance and the real part ε′ and imaginary part ε″ of the complex dielectric constant of NdFeB powders,in which the ε″ of Nd26.67Fe69.83Cr2.5B powders reduced significantly.The imaginary part μ″ of complex permeability increased with the introduction of Cr in the frequency range of 4~10 GHz,but it remained steady basically when the frequency in excess of 10 GHz.The minimum reflectivity of Nd11.76Fe82.35B5.88 powder with a coating thickness of 1.5 mm was about-8.5 dB,and its absorption peak frequency was about 10 GHz.The minimum reflectivity of Nd26.67Fe69.83Cr2.5B reduced to-17.0 dB,and the absorption peak frequency increased to 15.5 GHz.However,the minimum reflectivity of the powders rebounded to-10.8 dB,the absorption peak frequency increased to 15.8 GHz when the content of Cr was increased to 4%.Absorbing bandwidth became narrow owing to the addition of Cr.