Preparation and Microwave Absorption Properties of ZnO Nanoparticles Anchored on Submicron-Diameter Carbon Fibers

ZnO nanoparticles anchored submicron-diameter carbon fibers (denoted as ZnO/SDCFs) composites were synthesized by electrospinning combined with hydrothermal method. The influences of pH value of the reaction solution on the structure, composition, electromagnetic (EM) characteristics and microwave absorption properties of the products are investigated in details. The results show that with increasing pH value of the solution, the complex permittivity, dielectric loss and EM attenuation ability of as-obtained ZnO/SDCFs composites decrease monotonously due to the increase of ZnO content in composites, in contrast, the EM impedance matching is improved gradually. Compared as the pure SDCFs, the microwave absorption capacities of ZnO/SDCFs composites are enhanced at different degrees. Among all the samples, the ZnO/SDCFs-8 composite prepared in solution with a pH value of 8 owns the best overall absorption properties, which is mainly attributed to the better balance between its EM attenuation capability and impedance matching. For the paraffin composites with only 2.5% (mass fraction) ZnO/SDCFs-8 as absorbent, the minimum reflection loss (RL) reached 44.1 dB at 17.7 GHz, and the effective absorption bandwidth with RL values less than 10 dB was as wide as 6.1 GHz ranging from 11.9 to 18 GHz at a relatively thin matching thickness of 1.7 mm. Moreover, the effective absorption bandwidth can be further increased to 11.8 GHz (6.2-18 GHz) when the absorber thickness was 3.0 mm.