尖锥八面体Fe_3O_4的水热合成及微波吸收性能

Hydrothermal synthesis and microwave absorption of sharp octahedral Fe_3O_4 crystals

采用水热法,在碱性条件下,以PEG6000与水的混合溶液为反应介质,以硫代硫酸钠氧化前驱体氢氧化亚铁制备Fe3O4晶粉。采用X线衍射仪(XRD)和扫描电子显微镜(SEM)对产物结构和形貌进行表征。用微波矢量网络分析仪测试了样品在2～18GHz微波频率范围内的复介电常数和复磁导率,计算微波反射系数,探讨材料的微波损耗机制。研究结果表明:在水热反应一定时间后,得到单分散的尖晶石型Fe3O4晶粒,颗粒呈规则的尖锥八面体形貌且表面平整;对反应为12h、厚度为2.8mm的样品,7.1GHz频率位置的反射系数峰值为35dB,小于10dB吸收带宽为7.9GHz;低频段(2～13GHz)的微波吸收主要源于磁损耗兼具介电损耗,高频段(13～18GHz)的微波吸收主要源于介电损耗且磁损耗弱。尖锥微八面体Fe3O4是一种低反射率宽带微波吸收材料。

With mixed solution of PEG-6000 and water as a reaction medium, Fe3O4 crystal particles were synthesized by hydrothermal method from Fe（OH）2 precursor oxidized by Na2S2O3 in alkaline conditions. The crystal structure and surface morphology of the products were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）, respectively. The complex dielectric constant and complex permeability of Fe3O4 samples were measured by microwave vector network analyzer in the frequency range from 2 to 18 GHz. The microwave reflection coefficients of the samples were calculated according to measurements and the microwave absorbing mechanism was discussed. The results show that monodisperse spinel-type Fe3O4 crystal particles with regular sharp octahedral shape and fiat surface are obtained by hydrothermal reaction in a certain time, and the microwave reflection coefficient peak of the sample with 2.8 mm thickness is -35 dB at 7.1 GHz frequency and the absorption bandwidth less than -10 dB is 7.9 GHz after hydrothermal growth of 12 h. The microwave absorption is caused by magnetic loss mainly and dielectric loss secondly in the low-frequency range of 2-13 GHz, while dielectric loss mainly but magnetic loss weakly in the high-frequency range of 13-18 GHz. So, the sharp micro-octahedral Fe304 is an excellent microwave absorption material with low reflectivity and broadband.