粉煤灰空心微珠的Co-Ni-P化学镀及镀层的吸波性能

Microwave Absorbing Performance of Electroless Co-Ni-P Alloy Coating on Fly Ash Hollow Microspheres

为了实现吸波材料的薄型化及轻量化,采用化学镀工艺对粉煤灰空心微珠(5μm级)进行表面电磁改性,制备出"核-壳"结构新型轻质复合粉体吸波材料,探讨了Co-Ni-P化学镀工艺参数对吸波性能的影响。借助SEM,EDS和微波矢量网络分析仪研究了施镀工艺参数对镀层形貌、成分与吸波性能的影响。结果表明,空心微珠表面镀层由粒径0.5～1.0μm的钴镍磷合金球形颗粒堆垛而成,厚度均匀,镀层合金成分与镀液组成存在明显差异;镀覆后空心微珠属于磁损耗介质,具有较强的软铁磁性能;镀液中m(Co2+)/m(Ni2+)为3∶1时,镀层的m(Co)/m(Ni)为1.34,按此配比包覆后的吸波性能最优;增加镀液中还原剂次亚磷酸钠的浓度至50 g/L时,镀层非晶化程度增大,形成双相软磁材料使吸波性能增强,对电磁波反射最低达到-31.5 dB,小于-10.0 dB的有效频宽达到4.5 GHz(在8.2～12.7 GHz),具有良好的吸波效果。

A novel lightweight microwave absorbing powder material with core-shell structure was prepared by conducting electromagnetic modification of fly-ash cenospheres(5 μm scale) via electroless plating of Co-Ni-P.The effects of electroless plating parameters on the morphology,composition and microwave absorbing performance of Co-Ni-P alloy coating were investigated by using a scanning electron microscope,an energy dispersive spectrometer and a microwave vector network analyzer.Results show that the coating on the surface of cenosphere particles consists of stacked Co-Ni-P spheres with a size of 0.5～1.0 μm.The coating was even in terms of thickness,but its composition was much different from that of the plating bath.Besides,the coated hollow microspheres were magnetic loss dielectric media and possessed strong soft ferromagnetic properties.The coating obtained from the plating bath with a Co2+/Ni2+ mass ratio of 3∶1 had a Co/Ni mass ratio of 1.34 and the best microwave absorbing performance.When the concentration of hypophosphite in the plating bath was increased to 50 g/L,resultant coating had increased content of amorphous phase and turned into two-phase soft magnetic material,showing enhanced microwave absorbing ability.Namely,it had a lowest reflectivity of-31.5 dB,and its frequency range corresponding to a reflectivity below-10.0 dB was as much as 4.5 GHz(8.2～12.7 GHz).