Research On Preparing, Electric Heating And Anti-oxidation Property Of Novel Carbon/ceramic Composite

In recent years, electric heating materials have been rapidly developed. To satisfy the demand of the market at home and abroad presently, the electric heating materials should have characteristic of the safe, efficient, clean, energy-saving, low cost, and at the same time having long service life and the good serviceability. As the inorganic nonmetallic materials are resourceful, low cost and meanwhile have many superior properties, study on the electric heating carbon/ceramic composites by using inorganic nonmetallic materials as raw materials were developed here.In this research, Bentonite was selected as the ceramic matrix added by flake graphite and carbon black as conductive phase and SiC as reinforcement to prepare carbon/ceramic composites with a synthesis sequence of ball milling, molding pressure and non-oxidizing sintering. The influences of the particle size, pressure of die form, heat treatment temperature and the species of raw material on the component and mechanical properties of electric heating carbon/ceramic composites was studied. The results show that when average particle size was controlled as fine as18μm or even smaller, adding appropriate ratio of flake graphite, carbon black and SiC with a certain synthesis condition of50Mpa molding pressure and1100℃non-oxidizing sintering, an excellent combined carbon/ceramic composites would be obtained. The phase and micromorphology of the carbon/ceramic composites were characterized and analyzed by XRD and SEM, which reveals that there is no extra or new compound emerged, and that microstructure has few imperfection. Mechanical test shows that the flexural strength of carbon/ceramic composites can reach to14.3MPa, insuring its possible future application.The electric heating carbon/ceramic composites prepared possess superior electric heating property, which performs a rapid temperature increase and then remaining stability merely at a low alternating voltage of10V. The effect of flake graphite, pretreated graphite, carbon black and voltage on the resistivity and electric heating property of the composites was researched. The results show that,1) the resistivity would be decreased as the amount of graphite increasing and thus a better heat property could be found;2) pretreated graphite could provide better heating result than that of flack graphite;3) limited amount of carbon black would be benefit to improve the density of composite and slightly modify its resistivity;4) with identical conditions, alternating voltage could provide better heating result compared with direct voltage.The best product of this research shows an impressive rate of temperature increase,3.5℃/s, and eventually remains649℃. Furthermore, the negative resistance-temperature coefficient and satisfied heat stability of this carbon/ceramic composites have been confirmed which endows it with even more excellent electric heating performance.The electric heating carbon/ceramic composites prepared shows preferable antioxidation ability in a relative high temperature environment. By combining carbon materials and ceramic materials, oxidation-resistance of carbon materials could be improved effectively as rasing the weight losing temperature of200℃. Moreover, composite treated by infiltration, H3PO4/Al(OH)3/H3BO3, could resist oxidation effectively in even higher temperature, with only1.9wt%weight loss in1000℃. It enables the expected possible application of this electric heating carbon/ceramic composites in more rough environment.