Solvothermal synthesis of CoxFe3-xO4 spheres and their microwave absorption properties
Solvothermal synthesis of CoxFe3-xO4 spheres and their microwave absorption properties
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CoxFe3-xO4球的溶剂热合成及其微波吸收性能
DOI：
10.1039/c4tc00167b
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发表时间：
2014-01-01
影响因子：
6.4
通讯作者：
Bai, Ju
中科院分区：
文献类型：
--
作者：
Ji, Renlong;Cao, Chuanbao;Bai, Ju
以乙二醇（EG）为溶剂，通过溶剂热反应合成了Co（x）Fe（3-x）O 4（x 0-1）微球。结果表明，所制备的微球主要由小颗粒组成，粒径在300-500 nm之间。对于含有化学计量成分（Co 2+：Fe 3+的原子比为1：2）的EG溶液，所获得的球在200 ℃下为Co 0.9Fe 2.1O4（球A），在300 ℃下为Co 0.74Fe 2.26 O 4（球B），其晶粒尺寸分别为23 nm和30 nm。VSM测量揭示了球体B的改进的性质。不同的复合材料（75%的球的质量比）的复介电常数和磁导率的变化作为频率的函数进行了研究。计算的反射率值表明，含有球A的复合材料具有较好的微波吸收能力。在12.08 GHz时，最小反射损耗为41.089 dB，匹配厚度为2 mm，在3-14 GHz频率范围内，介质损耗的贡献大于磁损耗。双损耗的协同效应使得亚微球在X和Ku波段成为一种很有前途的吸收剂。由球形B组成的复合材料的介电性能较差，这是由于亚铁离子从八面体位置迁移到四面体位置以及由于大的微晶缺乏缺陷。经过700摄氏度的煅烧处理后，由于相邻八面体位置中的Fe 2 + 4 Fe 3+对消失以及缺陷的消失，介电损耗很低。微球中钴含量的变化可以改变微球的谐振频率和结晶度，最终改变微球的最小反射损耗和相应的频带。磁铁矿和钴铁氧体混合球的微波吸收性能受阳离子化学计量比和结晶完整性的影响。
Co(x)Fe(3-x)O4 (x 0-1) spheres are synthesized via a solvothermal reaction using ethylene glycol (EG) as a solvent. They are characterized, and the results show that the prepared spheres are mainly 300-500 nm in diameter and constituted by small grains. For the EG solution containing stoichiometric ingredients (atomic ratio of Co2+ : Fe3+ 1 : 2), the obtained spheres are Co0.9Fe2.1O4 at 200 degrees C (sphere A) and Co0.74Fe2.26O4 (sphere B) at 300 degrees C, whose crystallites are 23 nm and 30 nm in size, respectively. VSM measurements reveal improved properties with sphere B. Variations of complex permittivity and permeability for different composite (75% mass ratio of spheres) have been studied as a function of frequency. The calculated reflectivity value indicates that the composite containing sphere A displays better microwave absorption capability. The minimum reflection loss reaches 41.089 dB at 12.08 GHz, with a matching thickness of 2 mm. The dielectric loss contributes even more than magnetic loss in the frequency range of 3-14 GHz. The synergistic effect of dual losses makes the submicrosphere a promising absorbent in X and Ku bands. The composite consisting of sphere B is inferior in dielectric properties owing to ferrous ion migration from octahedral to tetrahedral sites and due to the big crystallites lacking defects. After the calcination treatment of the spheres at 700 degrees C, the dielectric loss turns out to be low due to the disappearing Fe2+ 4 Fe3+ pairs in adjacent octahedral sites and the loss of defects. Variations of the cobalt ratio in spheres can change the resonance frequency and crystallinity of the spheres and ultimately the minimum reflection loss and corresponding frequency band. The microwave absorption properties of mixed magnetite and cobalt ferrite spheres are influenced by the cationic stoichiometry and crystalline integrity.