基于Li0.35Zn0.3Fe2.35O4和碳纳米纤维双层吸波体的结构设计与吸收性能研究

通过静电纺丝技术和热处理制备了Li_0.35Zn_0.3Fe_2.35O₄纳米纤维和碳纳米纤维，并将它们各自均匀分散在硅橡胶基质中，测量了相应复合体在2~18GHz频率范围内的相对复介电常数和复磁导率，并根据传输线理论评估了由它们所构成的单层和双层结构吸波体的微波吸收特性。结果显示由于Li_0.35Zn_0.3Fe_2.35O₄纳米纤维与碳纳米纤维的电磁特性的有机结合，双层吸波体的微波吸收性能明显优于同厚度的单层吸波体。当以厚为1.8mm的Li_0.35Zn_0.3Fe_2.35O₄纳米纤维/硅橡胶复合体为吸收层和厚为0.2mm的碳纳米纤维/硅橡胶复合体为匹配层时，双层吸波体的反射率在13.9GHz达到一个最小值-47.8dB，反射率低于-10dB的吸收带宽为8.8GHz，频率范围为9.2~18GHz，反射率小于-20dB的频率范围为11.5~18GHz，带宽为6.5GHz，覆盖整个Ku波段。优化设计的双层吸波体有望作为一种轻质高效的Ku波段微波吸收材料。

Structural Design and Absorption Properties of Double-Layer Microwave Absorbers Based on Li0.35Zn0.3Fe2.35O4 and Carbon Nanofibers

Li_0.35Zn_0.3Fe_2.35O₄ and carbon nanofibers with average diameters of 160 and 360 nm, respectively, were fabricated by electrospinning technique combined with subsequent heat treatment. By dispersing the nanofibers homogeneously into a silicone rubber matrix, the relative complex permittivity and permeability of the composites containing either 60wt% Li_0.35Zn_0.3Fe_2.35O₄ nanofibers or 5wt% carbon nanofibers as fillers were measured in the frequency range of 2~18 GHz. Electromagnetic wave absorbing performance of both single-layer and double-layer microwave absorbers was evaluated according to transmission line theory. It is found that the double-layer absorbers have much better microwave absorption properties than the single-layer absorbers with the same thickness due to the proper combination of the electromagnetic characteristics resulting from the magnetic Li_0.35Zn_0.3Fe_2.35O₄ nanofibers and dielectric carbon nanofibers. When the absorbing layer is the Li_0.35Zn_0.3Fe_2.35O₄ nanofibers/silicone rubber composite with a thickness of 1.8 mm and the matching layer is the carbon nanofibers/silicone rubber composite with a thickness of 0.2 mm, the refection loss (RL) of the double-layer absorber reaches a minimum value of -47.8 dBat around 13.9 GHz and the absorption bandwidth with the RLvalue below -10 dBis about 8.8 GHz ranging from 9.2~18 GHz. Meanwhile, the RL value exceeding -20 dBis obtained over the range of 11.5~18 GHz, which covers the whole Ku-band. The results indicate that the optimal double-layer microwave absorbers can be a promising candidate for lightweight and highly effective microwave absorption materials in Ku-band.