ZnO nanostructures grown on carbon fibers: Morphology control and microwave absorption properties

Morphology control is crucial to the applications of zinc oxide (ZnO) nanocrystals. In this study, ZnO nanostructures with varying morphologies were coated on the surface of carbon fibers (CFs). Scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) were conducted to characterize the morphology and structure of the ZnO-coated CFs (ZCCFs). SEM images reveal that ZnO nanostructures with different morphologies and microstructures are uniformly coated on CFs. XRD and TEM studies show that the products consist of crystallized hexagonal wurtzite ZnO. The complex permittivity and permeability of the ZCCF/paraffin composites with two different ZnO morphologies (floccus and particle) were measured in the frequency range of 1-18 GHz and their microwave absorption properties were investigated. Results show that the ZCCF/paraffin composite containing 30 wt.% floccus-shaped ZnO exhibits significantly higher dielectric loss and better microwave absorption properties as compared to that with particle-shaped ZnO. It is demonstrated that the floccus-like ZnO-coated CFs are a promising microwave absorbent with light weight, small thickness, strong absorption, and broad bandwidth.