Study On Catalytic Graphitization Of Carbon Fibers With Alloy Coating

Carbon fibers are a new type of high-performance reinforced material which has characteristics of low density, high strength, high modulus, resistance to high-temperature, good chemical anti-corrosion, low resistance, high thermal conductivity, low thermal expansion, resistance to chemical radiation and good biocompatibility. Carbon fibers are used mostly as reinforced materials of resin, carbon, metal, ceramic and cement and have extensive applications in aerospace, automotive, civil engineering, cultural and sports equipment, medical devices and so on. Carbon fibers coated with metals can further expand their application scope. The properties of carbon fibers can be greatly enhanced after graphitization. However, high heat treatment temperature (HTT) to graphitization is the main factor leading to high price of graphite fibers. The graphitization temperature can be reduced and the graphitization process will be facile by adding catalysts. Studies on catalytic graphitization of carbon fibers have mainly concentrated on single elements. However, there is little research on multi-element catalytic graphitization. Electroplating alloy on the surface of carbon fibers and the catalytic graphitization mechanism of carbon fibers with electrodeposited alloy coating were studied in this paper. The main contents are presented as follows:1. The process of electroplating Ni-B alloy on the surface of carbon fibers was investigated. The results show that the Ni-B deposits performance and deposition rate were evidently affected by pretreatment, bath composition and electrodeposition parameters. scanning electron microscope (SEM) , X-ray diffraction (XRD) and ICP-AES techniques were used to analyze the morphology, structure and composition of the Ni-B deposit. The results show that uniform, compact Ni-0.8～4 wt%B microcrystalline coatings with good adhension can be obtained under certain conditions.2. Catalytic graphitization of carbon fibers with electrodeposited Ni-B alloy coating was studied. Carbon fibers with and without electrodeposited Ni-B coating were heat treated at different temperatures and the structural changes were characterized by XRD, Raman spectroscopy and SEM The results show that high graphitization can be achieved for carbon fibers at low heat treatment temperature (HTT) when the Ni-B coating is present. Moreover, the degree of graphitization increases with the increasing of B content in Ni-B coating for Ni-B coated carbon fibers at the same HTT. The mechanism of catalytic graphitization was discussed.3. Catalytic graphitization of carbon fibers with electrodeposited Fe-P alloy coating was studied. Carbon fibers with electrodeposited Fe-P coating were heat treated at different temperatures and the structural changes were characterized by X-ray diffraction, Raman spectroscopy and scanning electron microscope. The results show that high graphitization can be achieved for carbon fibers at lower HTT when the Fe-P coating is present. Moreover, the degree of graphitization increases with the increasing of P content in Fe-P coating for Fe-P coated carbon fibers at the same HTT. And the degree of graphitization increases with the increasing of the electrodepositing time of Fe-P coating. But the degree of graphitization is unchanged when the catalyst reaches a certain quantity. The mechanism of catalytic graphitization was also discussed.