采用非平衡物理气相蒸发法在氢气氩气混合气氛下制备了氧化硅包覆铁“壳/核”型纳米复合粒子. 通过X射线衍射(XRD)、透射电子显微镜(TEM)和能谱分析(EDS)等方法表征了纳米复合粒子的相组分、结构以及颗粒形貌. 结果表明，制备的氧化硅包覆铁纳米复合粒子的尺寸在50nm左右，在铁纳米粒子的表面还出现了非晶态的氧化硅纳米棒，长度为150~200nm. 利用电磁参数模拟微波吸收特性得出，涂层厚度为1.79mm时，在15.4GHz频率处达到最小反射损耗值为-14.5dB，反射损耗在8~18GHz的频段低于-10dB，且损耗机制为自然共振.
Silica-coated Fe nanocomposites were prepared by the DC arc plasma in a mixed atmosphere of hydrogen (H2) and argon (Ar). The phase structure, composition and morphology of silica-coated Fe nanocomposites were examined by X-ray diffraction(XRD), transmission electron microscope(TEM) and electron energy dispersive spectroscope(EDS). The results show that the mean size of silica-coated Fe nanocomposites is about 50nm, and the amorphous silica which cover BCC-Fe cores form nanorods with the length of 150-200nm. The growth mechanism of silicacoated Fe nanocomposites is governed by an extended vaporliquidsolid mechanism and Fe nanoparticles acted as a catalyst for the growth of the nanorods. Its electromagnetic parameters are measured in the range from 2GHz to 18GHz. It is calculated that the maximum reflection loss of silica-coated Fe nanocomposites can reach -14.5dB at 15.4GHz with 1.79mm in thickness, and the bandwidth with a reflection loss less than -10dB is from 8-18GHz. The indepth study of relative complex permittivity and permeability reveals that the excellent microwave absorption properties are the consequence of a proper EM match in microstructure. And the loss mechanism is natural resonance, as the consequence of the increased surface anisotropic energy for nanosized particles.
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