Abstract
Lithium-zinc ferrite hollow microspheres (LiZn FHMs) containing special surface crystals were synthesized by self-reactive quenching technology. The samples were heat-treated at 1200 °C and held for 4 h. The influence of the heat-treatment on LiZn FHMs was studied. The results show that the surface of hollow microspheres is smooth without heat-treatment. The phase components are Fe2O3, Fe3O4, Li0.435Zn0.195Fe2.37O4, and Li0.5Fe2.5O4. The minimum reflectivity is −13.5 dB, and the corresponding frequency is 7.5 GHz. The effective absorption band lower than −10 dB is 6.2–8.5 GHz, and the bandwidth is 2.3 GHz. After heat-treatment, crystals on the surface of hollow microspheres grow significantly. Multiple-shape micro-nano crystals containing triangular, polygonal, and irregular crystal are generated. However, the phase composition does not change. The real part of the permittivity (ε′), the imaginary part of permittivity (ε″), the real part of permeability (μ′), and the imaginary part of permeability (μ″) all increase, and the microwave absorption properties at low frequency are significantly increased, with the absorption peak moving to a lower frequency range. The minimum reflectivity is −26.5 dB, and the corresponding frequency changes to 3.4 GHz. The effective absorption band is 2.6–4 GHz, and the bandwidth is 1.4 GHz.
摘要
目的
自反应淬熄法制备的LiZn 铁氧体空心微珠密度小,低频吸波性能良好,但微珠表面晶型生长不充分。对其采用特定热处理工艺不仅可以使晶体充分发育,获得特定晶型,还可以实现对低频吸波性能的有效调控。本文旨在研究热处理工艺对LiZn 铁氧体空心微珠表面形貌、相结构和低频吸波性能的影响。
创新点
1. 通过热处理工艺,实现对LiZn 铁氧体空心微珠表面形貌、相结构和低频吸波性能的有效调控;2. 深入分析热处理工艺对LiZn 铁氧体空心微珠低频吸波性能的改善机理。
方法
1. 通过工艺探索,确定热处理的详细工艺参数。2. 通过扫描电子显微镜检测和X 射线衍射分析,获得热处理前后LiZn 铁氧体空心微珠的微观形貌(图2)和物相组成(图3)。3. 通过矢量网络分析仪,获得热处理前后材料的电磁参数(图4);在此基础上对比其吸波性能(图5),并研究吸波影响机理。
结论
1. 采用240 °C/min 升温至1200 °C 并保温4 h 的热处理后,LiZn 铁氧体空心微珠表面晶粒明显长大;2. 热处理后,微珠四个电磁参数均有所增大,低频吸波性能明显提高,吸收峰值向低频移动;3. 表面多种形状微纳米晶粒的形成和长大可能是LiZn 铁氧体空心微珠低频吸波性能得以提高的主要原因。
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Project supported by the National Natural Science Foundation of China (No. 51172282) and the Hebei Provincial Natural Science Foundation of China (No. E2015506011)
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Cai, Xd., Wang, Jj., Jiang, Xj. et al. Effect of heat-treatment on LiZn ferrite hollow microspheres prepared by self-reactive quenching technology. J. Zhejiang Univ. Sci. A 19, 409–416 (2018). https://doi.org/10.1631/jzus.A1600768
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DOI: https://doi.org/10.1631/jzus.A1600768