非均相沉淀-热还原制备纳米金属包覆Al_2O_3复合微球

Preparation of Nanosized Metal Coated Alumina Composite Microspheres by Heterogeneous Precipitation-Thermal Reduction Process

采用非均相沉淀—热还原工艺分别制备了纳米Fe、Co、Ni及其合金包覆Al_2O_3微球粉体,并利用SEM、XRD对热还原产物的成分、结构及形貌进行了表征,通过VSM对FeNi包覆Al_2O_3复合微球的磁滞行为进行了检测。结果表明:非均相沉淀—热还原工艺可以制备单分散或连续致密分布的金属包覆型复合微球,包覆层金属颗粒分布均匀、颗粒细小,一次颗粒粒径小于100 nm。包覆层前驱体经H_2热还原由无定型结构分别转变成了纯金属相或固溶体合金。FeNi包覆Al_2O_3微球的饱和磁化强度与纯FeNi相比未发生变化,但矫顽力大幅提高,增强了磁滞损耗,有望成为良好的电磁波吸收剂。

Nanosized alumina microspheres coated with Fe, Co, Ni and their alloys were successfully prepared by the heterogeneous precipitation--thermal reduction process. Their composition, structure and morphology were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. Hysteresis behavior of FeNi-coated alumina microspheres was investigated via vibration sample magnetmeter （VSM）. The results indicate that the alumina microspheres were coated by dispersive or continuous metal particles in the heterogeneous precipitation--thermal reduction process. The precursor coatings on alumina microspheres correspondingly were transferred into pure metal or solid solution alloy with particle size less than 100 nm during the hydrogen reduction process. The saturation magnetization intensity of FeNi-coated alumina microspheres was equal to that of pure FeNi alloy, but the coercive force increased, which leads to a higher magnetic loss. It was concluded that the composite microspheres would be a promising electromagnetic-wave absorber.