Study On Catalytic Graphitization Of Furan Resin Carbon And Pan-based Carbon Fibers

Carbon materials have very good mechanical, electrical and thermophysical properties, and are used widely in printing, electrode, metallurgy, avigation, spaceflight, etc. The properties of carbon materials depend on their graphitization degree. In generally, the graphitization of carbon happens at high temperature. In order to decrease energy waste and accelerate graphitization of non-graphitizable carbon, some catalysts were used to accelerate the graphitization of carbon, i.e., catalytic graphitization.In this dissertation, the effects of some new catalysts and dispersion method of catalysts in carbon materials on the catalytic graphitization of furan resin carbon and PAN-based carbon fibers have been studied. X-ray diffraction and Raman spectroscopy were used to examine the extent of graphitization of the carbon materials, the morphology of the resulting carbon was characterized by scanning electron microscopy. The influence factors and graphitization mechanism of carbon materials were also investigated. The main points in this dissertation are summarized as follows:1) Furan resin was used as carbon source, and rare earth elements (yttrium, lanthanum, cerium, and praseodymium) were used as catalysts, the catalytic graphitization of furan resin carbon by rare earth elements was investigated. X-ray diffraction and Raman spectroscopy were used to examine the graphitization of the furan resin carbon; the morphology of the resulting carbon was characterized by scanning electron microscopy. The results indicate that all rare earth elements (yttrium, lanthanum, cerium, and praseodymium) can accelerate the graphitization of furan resin carbon obviously. The catalyst content and the heat-treatment temperature (HTT) were two main factors on the catalytic graphitization of furan resin carbon. The optimum content for yttrium is 4wt% (9wt% for cerium , 15wt% for praseodymium). Among these catalysts, yttrium has the highest catalytic efficiency on the graphitization of furan resin carbon. For all rare earth elements, the mechanism of catalytic graphitization follows the carbide formation-decomposition mechanism (relatively low HTT) and the dissolution-precipitation mechanism (relatively high HTT).2) Graphite oxide (GO) was used as additive, and furan resin was used as carbon source, the effect of graphite oxide (GO) on graphitization of furan resin carbon was investigated. The extent of graphitization of furan resin carbon was examined by X-ray diffraction and Raman spectroscopy. The morphology of furan resin carbon was characterized by scanning electron microscopy. The results indicate that GO can accelerate the graphitization of furan resin carbon and the extent of graphitization of furan resin carbon increases with the GO content and the HTT.3) The metallic praseodymium (yttrium) was used as the catalyst and electrodeposited on the surface of PAN-based carbon fibers, the catalytic graphitization of PAN-based carbon fibers by praseodymium (yttrium) was investigated. The surface morphology of the PAN-based carbon fibers with praseodymium (yttrium) was characterized by scan electron microscopy. The effect of praseodymium (yttrium) on catalytic graphitization of PAN-based carbon fibers was investigated by X-ray diffraction. The results indicate that praseodymium (yttrium) has the good effect on the catalytic graphitization of PAN-based carbon fibers, the optimum praseodymium (yttrium) content is 8wt% (20 wt%).4) Silicomolybdic acid was used as the catalyst and deposited onto carbon fibers by alternate DC electrolysis, the catalytic graphitization of PAN-based carbon fibers by silicomolybdic acid was investigated. Element distribution of PAN-based carbon fibers after alternate DC electrolysis was characterized by energy dispersive X-ray spectroscopy. The catalytic graphitization of PAN-based carbon fibers was investigated by X-ray diffraction and Raman spectroscopy. The results indicate that the structure of PAN-based carbon fibers was destroyed, and the catalyst was simultaneously dispersed into fibers through alternate DC electrolysis; the graphitization of PAN-based carbon fibers is obviously enhanced in the presence of silicomolybdic acid, and the graphitization degree of carbon fibers with deposited silicomolybdic acid treated at 2400?C is 95.3%, which is much higher than that of the pristine carbon fibers treated at 2400?C.5) Graphite oxide (GO) was used as additive, furan resin was used as carbon source of the matrix carbon, and PAN-based carbon fibers was used as the reinforcement of C/C composites, the effect of GO on the graphitization, resistivity and compressive strength of C/C composites was investigated. The graphitization extent of C/C composite was investigated by X-ray diffraction, the resistivity and compressive strength of C/C composites were monitored by the Four-Point Probes and Electronic Universal Testing Machine, respectively. The results indicate that GO can enhance the compressive strength, decrease the resistivity and enhance the graphitization degree of C/C composites.6) Catalytic graphitization of carbon sphere (PAN-based carbon fibers) by transitional metal element Mo(Mn) has been investigated by X-ray diffraction. (a) Phosphomolybdic acid was used as the catalyst, furan resin was used as carbon source, the effect of phosphomolybdic acid on the preparation and the catalytic graphitization of carbon sphere was investigated. The results indicate that the carbon spheres were well obtained and the degree of graphitization of carbon sphere was enhanced by molybdenum. (b) Through the redox reaction between the PAN-based carbon fibers and KMnO4, Manganese oxides were spontaneously deposited on the surface of PAN-based carbon fibers. The effect of manganese oxides on the catalytic graphitization of PAN-based carbon fibers has also been investigated. The catalytic graphitization of the PAN-based carbon fibers can be achieved by manganese oxides.