Fe₃O₄纳米微球、MWCNT/Fe₃O₄异质结构溶剂热制备和微波吸收性能

Solvothermal Synthesis and Microwave Absorbing Properties of Fe₃O₄Microspheres and MWCNT/Fe₃O₄Heterostructures

摘要: 以六水氯化铁、无水乙酸钠和乙二醇为原料，采用溶剂热法制备了尺寸均一的Fe₃O₄纳米微球。在反应体系中掺入多壁碳纳米管(MWCNTs)并通过改变其用量进而制备了一系列链状MWCNT/Fe₃O₄异质结构。利用扫描电子显微镜(SEM)和X-射线衍射仪(XRD)对Fe₃O₄纳米微球和MWCNT/Fe₃O₄异质结构进行形貌和晶相分析。结果表明Fe₃O₄纳米微球有明显的层级结构，在异质结构中不连续地镶嵌在MWCNTs表面，且镶嵌密度随MWCNTs用量的减少而增大。MWCNTs的掺入对Fe₃O₄纳米微球的晶相没有影响，但组成微球的颗粒变得更小。用N5230A型网络矢量分析仪测试两者在2～18 GHz的微波吸收性能。结果显示Fe₃O₄纳米微球有明显的微波吸收性能，且吸收频率区间和最大吸收峰随涂层厚度增加向低频移动。相比之下，MWCNT/Fe₃O₄异质结构的微波吸收能力在低频明显降低，而在高频有所增强。

Abstract: Fe₃O₄ microspheres were prepared via a facile solvothermal method using hydrous ferric chloride and anhydrous sodium acetate as materials, and ethylene glycol as solvent. Furthermore, the tunable denseness carbon nanotubes (MWCNTs)/Fe₃O₄ heterostructures were obtained by adjusting the ratio of ferric chloride and MWCNTs in the reaction system. The morphology and phase of the products were characterized by scanning electron microscope (SEM) and X-ray diffractometer (XRD). The results show that Fe₃O₄ microspheres with hierarchical structure wrap discontinuously on MWCNTs in the hybrids, and wrapping density increase with reduction of the amount of MWCNTs. The Fe₃O₄ microspheres with an unchanged phase in the heterostructures are composed of smaller particles after addition of MWCNTs than before. In addition, microwave absorbing properties of Fe₃O₄ microspheres and MWCNT/Fe₃O₄ heterostructures were measured at a microwave frequency range of 2 - 18 GHz with an N5230A vector network analyzer, and the results indicated that Fe₃O₄ microspheres obviously possessed the ability of microwave absorption and the strongest absorbing peak shifted to lower frequency with the coating thickness increase. Compared to Fe₃O₄ microspheres, MWCNT/Fe₃O₄ heterostructures tend to absorb microwave at higher frequency and weaken absorption at lower frequency.