真空热处理对快淬纳米复合NdFeB电磁特性的影响

Effect of vacuum heat treatment on microwave properties of melt-spun NdFeB nanocomposite

采用真空快淬技术制备低Nd含量的NdFeB纳米复合磁性材料,通过差示扫描量热法(DSC)、X射线衍射(XRD)、振动样品磁强计(VSM)和微波矢量网络分析仪等手段研究了真空热处理前后样品微观结构和电磁特性的变化。DSC结果显示在510℃和630℃处出现两个放热峰,在稍微高于这两个温度分别热处理后,相对于快淬态样品,材料的磁导率(μ')和磁损耗(μ″)降低,并且磁损耗出现多重频散特性,同时复介电常数减小,特别在2 GHz处ε″分别为-103.7(540℃)和ε″为-245.3(650℃)。根据传输线理论模拟计算涂层的反射损耗,发现快淬态样品在3.7 GHz下厚度为1.5 mm时最小反射损耗为-5.3 dB;而热处理后的样品在12 GHz处获得最小反射损耗,分别为-3.3 dB(540℃)和-2.1 dB(650℃)。

Nanocomposite NdFeB alloy with low content of Nd were prepared by melt-spun technique.The microstructure and electromagnetic parameters were investigated by means of differential scanning calorimetry（DSC）,X-ray diffraction（XRD）,vibrating sample magnetometer（VSM） and microwave vector network analysis.The results show that there are two exothermic peaks at 510 ℃ and 630 ℃ for DSC curve.After vacuum heat treatment at 540 ℃ and 650 ℃,respectively,the microwave properties are detected,and then compared with the as-spun sample,both the complex permeability and complex permittivity for annealed samples reduce and the magnetic loss appears multiple dispersions.Especially the complex permittivity can be reached to ε″=-103.7（540 ℃）and ε″=-245.3（650 ℃）at 2 GHz.According to transmission line theory,the reflection loss was calculated.Results show that the minimal reflection loss of as-spun sample is-5.3 dB at 3.7 GHz with thickness of 1.5 mm.And after annealing,the minimal reflection loss is obtained at 12 GHz and its value is-3.3 dB（540 ℃）and-2.1 dB（650 ℃）,respectively.