The Preparation, Characterization And Application Of Carbon Fibers Coated With Fe₃ O₄ Films

Carbon fiber (CF) microwave absorption materials are multifunctional composites with high strength and modulus, good carrying capacity, excellent electrical property and reflection loss characteristic, which are increasingly recognized as practical structural absorption composites. The magnetization modification of CFs is an important way to enhance the microwave absorption property of CFs filled composites. In this work, cathodic electrodeposition was explored successfully to fabricate Fe3O4 coated carbon fibers (MCCFs). Compared with CFs, MCCFs not only have additional magnetic loss characteristic, but avoid the formation of conductive CF network in the matrix and reduce the reflectivity of the composites.The experimental results of this work indicated that the Fe3O4 films were uniform and compact. As a byproduct, element Fe existed in the films. With the change of electrodeposition temperature and current, the shapes of Fe3O4 grains were diverse. The pretreatment of CFs with nitric acid increased the chemical and physical nonuniformity, which influenced the formation process of Fe3O4. The influence of electrodeposition temperature, current and fiber pretreatment on the composition and morphology finally led to the diversity of MCCFs with respect to the magnetic and microwave absorption properties.The MCCF/W-type hexagonal Sr ferrite/methyl vinyl silicone rubber (MCCF/WHF/VMQ) and graphite/SiC/VMQ composites were manufactured for the research on microwave absorption properties of the single-layer and double-layer materials. The reflection loss results showed that the microwave absorption properties of WHF/VMQ composites were significantly improved by MCCFs as well as their mechanical properties. As far as the double-layer microwave absorption materials, when the graphite/SiC/VMQ composites served as the surface layers, the absorption frequency band could be modulated by changing the contents of the fillers of surface layers. When the MCCF/WHF/VMQ composites served as the surface layers, the overall microwave absorption properties of double-layer composites were enhanced because of the improved impedance matching characteristic between surface layers and air.The fabrication of high-resistance Fe3O4 films endowed CFs with advantages in the utilization of microwave absorption materials. The practical research confirmed the availability of MCCFs on improving the microwave absorption and mechanical properties of WHF/VMQ composites. Through the design of double-layer microwave absorption materials, the modulation mechanisms of absorption frequency band and impedance matching characteristic for different types of attenuation materials were investigated. These researches had great significance for the design and application of microwave absorption materials.