氧化硅包覆铁“壳/核”型纳米复合粒子的制备及其吸波特性研究

Synthesis and Microwave Absorption of the Silica-coated Fe Nanocomposites

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 nano- composites 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 silica-coated Fe nanocomposites is governed by an extended vaporliquid-solid 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 l. 79mm in thickness, and the bandwidth with a reflection loss less than - 10dB is from 8 - 18GHz. The in-depth 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.