Preparation And Properties Of High-temperature Coated Carbon Fiber

Abstract:Carbon fibers are widely used in military, aerospace, construction and transportation because of its low density, high modulus, high strength, excellent mechanical properties and chemical stability, etc. Carbon fiber has valuable potential applications in the field of high temperatures and stealth field, the carbon fiber itself is a strong radar reflector and carbon fiber is oxidized at about400℃under aerobic conditions, which greatly limit application of the carbon fiber. This paper aims preparation of h-BN coating on carbon fiber surface. Experiment improvements the property of carbon fiber to expect changes in insulation resistance and oxidation resistance of carbon fiber, so as to meet the application requirements of stealth field and temperature field.First, we prepared h-BN coating carbon fiber with nitrogen-containing precursor, with urea and boric acid as a raw material for preparing nitrogen precursor solution and ammonia gas as the reaction gas during heat treatment process. In order to study effects of heat treatment temperature on the generation of the coating, impact of precursor proportion on the generation of the coating, effect of heat treatment time on the generation of the coating, impact of reactive substances on the generation of the coating, a series of experiments have been done. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) have been used to characterize composition, structure, morphology of the coating. The results show that h-BN produced when the heat treatment temperature began rise550℃the heat treatment temperature is higher h-BN generated the better, the higher the heat treatment temperature is less O content in the coating, in order to ensure the mechanical properties of the carbon fiber temperature should not be too high; the coating is the best when the mass ratio of urea and boric acid precursor is1:1; B, N, O element content in the coating decreases as the heat treatment time becomes longer, the longer the heat treatment the higher the purity of the coating; when urea and ammonia react together the coating is the best. Secondly, the experiment prepare h-BN coating on carbon fiber with polymer precursor, polyvinyl alcohol and boric acid as raw materials for preparing polymer precursor, ammonia as the reaction gas during heat treatment process, and finally h-BN coated carbon fiber got. The experiment studied impact of the molar ratio of the precursor solution on the generation of the coating, coated carbon fiber thermal stability and electrical properties of coated carbon fiber. The results showed that h-BN coating on the surface of the carbon fiber can be prepared with a precursor material solution prepared with polyvinyl alcohol and boric acid as raw materials, reducing heat treatment temperature; Thermal stability of coated carbon fiber is better than the original carbon fiber’s; coated carbon fiber is relatively original carbon fiber insulating higher.43figures.13tables.70references.