Preparation And Electrothermal Properties Of One-step Firing Modified Carbon Fiber Ceramic Matrix Composite

Ceramic is a suitable material as the surface element of electrical heaters,because of its particular advantages,such as excellent chemical inertness,high thermal conductivity,reliable mechanical property,good insulation and low cost.Carbon fiber not only has excellent mechanical properties such as high specific strength and high specific modulus,but also has good electrical and thermal conductivity.It has been widely used as a heating material in ceramic and polymer composites.Because of higher electric-to-heat conversion efficiency,good electrical conductivity and excellent mechanical properties,carbon fiber can be applied to indoor heating equipment,which can solve problems such as large power consumption and potential safety hazards.In this paper,the conductive and thermal properties of carbon fibers were used as the starting point,the surface modification and oxidation of carbon fibers were the guarantee,and the one-step firing method was the innovation point to prepare a modified carbon fiber ceramic matrix composite material,and researched the aspects of resistance stability and electric heating characteristics;By setting different size parameters of the sample,the electrothermal efficiency was studied,at the same time,its microstructure was characterized and compared by scanning electron microscope?SEM?,thermogravimetry?TGA?,X-ray diffraction?XRD?,atomic force microscope?AFM?and mechanical properties,which provided guidance for engineering applications of composite materials.Based on the original ceramic preparation method,different size parameters were designed for the thickness of ceramics,the length of carbon fibers,and the number of carbon fibers.At the same time,the surface oxidation of carbon fibers and ceramicification of ceramic powder?kaolin,Feldspar and quartz?were achieved at a high temperature?1100¹200??,and the modified carbon fiber ceramic matrix composites with different specifications were prepared.The influence factors of the oxidation resistance of the modified carbon fiber were studied,and it was found that the graphene coating successfully achieved the oxidation resistance of the carbon fiber surface,and the N₂ atmosphere also played a role in protecting the carbon fiber during the sintering process.The static resistance characteristics of the modified carbon fiber ceramic matrix composites were studied.It was found that the size effect of the resistance characteristics of the modified carbon fiber ceramic matrix composites was expressed as follows:the resistance of the carbon fibers increased linearly with the increase in length,and the smaller the number of carbon fiber bundles,the greater the electrical resistance of the carbon fiber bundles.The relationship between the resistance and temperature of the modified carbon fiber ceramic matrix composites and the electrical and thermal characteristics were studied.The optimal number of twists of the carbon fiber twist required to maintain the thermal stability of the composite was grasped.The on-off heating rules of carbon fiber electrothermal composite materials were obtained:The surface temperature of the composite material will rise rapidly after being energized,reach a stable temperature after being energized for 30 minutes,and then no longer change significantly.When the power is turned off,the surface temperature of the composite material drops rapidly,and then it can be maintained above room temperature for a long time.The thermal stability of the modified carbon fiber ceramic matrix composite material was realized:After applying a constant voltage,and then turning on and off multiple times,the resistance of the composite material can be stabilized within a fluctuation value of±0.1?.The heating efficiency of the modified carbon fiber ceramic matrix composite was studied.It was found that at the same power,the smaller the thickness of the ceramic sheet,the larger the temperature rise of the composite and the better the heating effect.The temperature rise of composite materials under different powers was studied,and its electrothermal efficiency was found to be related to the length of carbon fiber bundles and the number of carbon fiber bundles.The mechanical properties of the modified carbon fiber were studied,and it was found that the graphene coating can improve the mechanical properties of the carbon fiber.This has important guiding significance for the dimensional design of large-scale applications of modified carbon fiber ceramic matrix composites.