快淬速度对低钕纳米复合NdFeB材料吸波特性影响

Effect of Quenching Speed on Microwave Properties of Melt-spun NdFeB Nanocomposite

研究在不同淬速下获得的低Nd复合Nd Fe B材料吸波特性。X射线衍射（XRD）显示不同淬速下获得的样品晶体结构都呈α-Fe体心立方结构,扫描电子显微镜（SEM）显示样品都具有扁平状的微观结构,但均匀性及钝化程度不同。随着淬速的增加,合金的矫顽力和剩磁呈先升后降的趋势,矢量网络分析仪测量的样品电磁特性基本符合频散特性,淬速为40 m/s样品的磁损耗（μ″）先升后降,表明此样品μ″和晶粒间磁共振有关。基于传输线理论对样品反射损耗（RL）的数值模拟结果表明,涂层厚度为1.5 mm,淬速30 m/s样品在8.2 GHz获得的最小反射损耗RLmin为-7.69 d B,淬速40 m/s的样品在3.1 GHz时RLmin为-5.87 d B,当淬速增加到50 m/s时,样品在8.9 GHz处获得RLmin为-8.8 d B,不同的快淬速度对晶体结构的改变显著影响其吸波特性。

The Nd3 Fe68 Co18 B11 alloy was prepared by rapid quenching at different quenching speed. The XRD spectra show that only α-Fe phase can be observed from those quenching samples. Milled powder samples have the microstructure of a flat shape,but with different degree of fragmentation and passivation at the edge. With the increase of the quenching speed,the magnetic properties of the alloy show a trend of increasing first and then descending. The electromagnetic parameters obtained by the vector network analyzer show that the complex permittivity and the complex permeability increase and then decrease with the increase of quenching speed. All these samples conform to the dispersion characteristics. Based on transmission line theory,it is calculated that the sample with quenching speed of 30 m/s can achieve their optimal reflection loss（ RL=-7. 69 d B） at 8. 2 GHz with a coating thickness of 1. 5 mm. When the quenching speed increased to 40 m/s,the optimal reflection loss（-5. 87 d B） at 3. 1 GHz was obtained. As the quenching speed is increased to 50 m/s,the sample can obtain optimal reflection loss（-8. 8 d B） at 8. 9 GHz.