Preparation And Properties Of Carbon Fiber In Millimeter Wave Attenuation Material Research

Polyacrylonitrile based carbon fibers were submitted to3day’s nitric acid oxidation treatments to improve their properties such as specific surface area and increase the oxygen-containing functional groups on the surface.Metal or alloy was electroless-planted on the surface of the oxidized carbon fibers to improve their conductivity as to skin effect. Metal or alloy layers were electrolessly deposited directly on the surface of the oxidized carbon fiber without using the conventional palladium or silver catalyst to initiate redox reactions leading to metallization. The chemical properties of metallized carbon fibers were estimated by SEM, XRD, EDS and TG. The results indicated that uniform and smooth metal or alloy coating could be obtained by the new precious-metal free activation process.The3mm and8mm microwave attenuation capability of metallized carbon fibers was tested by a dynamic method using cyclohexane as solvent. Compared to carbon fibers, the3mm and8mm microwave attenuation capability of metallized carbon fibers respectively increased by3-15dB and8-21dB. Among different metal and alloy coating layers, carbon fibers with Ag layers had the best microwave attenuation capability. Besides, carbon fibers with metal layers had better microwave attenuation capability than carbon fibers with alloy layers.As for3mm microwave, the best length of carbon fibers and metallized carbon fibers for3mm microwave attenuation isl.5mm or3mm.Considering to the carbon fibers’dispersing,1.5mm is a better choice.With the increase of layer’s thickness, the3mm and8mm microwave attenuation capability was improved at first, then it would descend after it reached a maximal value. The optimum layer’s thickness for actual3mm and8mm microwave attenuation test tends to be lower than the theoretical calculating value.