Preparation And Property Research Of C_f/SiC Composite

As fiber-reinforced ceramic matrix composites, Cf/SiC composite materials is a new type of structural materials with outstanding performance, such as high-strength, high hardness, high temperature use, wear resistance, anti-oxidation, and so on. These materials, widely used in the aerospace field, are becoming a research hotspot. Take Cf/SiC composite's as application background, this paper intent to shorten its production cycle, reduced costs and produce Cf/SiC composite materials by industrial furnaces. Solid-phase milling dispersed, molding and high temperature sintering technology had been used to prepare the Cf/SiC composite materials. The key technology for the preparation of the composite material, carbon fiber surface treatment, has been optimized. Scanning Electron Microscopy (SEM) and other analysis methods had been used on the research of its organizational structure characteristics. The mechanical properties, friction and wear properties and oxidation performance of the materials had also been studied. The characteristics of fracture failure and the toughen mechanism had been studied lastly. The results show that:Firstly, after the surface treatment by concentrated nitric acid liquid on carbon fiber, the number of active groups on the carbon fiber surface increased, surface activity increased. The dispersion condition of carbon fiber was exhausted. The cohesive force between carbon fiber and silicon carbide interface was reinforced. The compatibility problem between the short carbon fiber and silicon carbide matrix was solved.Secondly, by the comparison of the influence of the binder, the sintering temperature and the content of carbon fiber on the mechanical properties of materials, the formula for the binder was ascertained as 35% PVA and 65% hydroxymethyl cellulose, content of 3% total materials. The bending strength reached the highest point 8.7 MPa when carbon fiber content was 15%. The change of coefficients of thermal expansion of samples should be ascribed to the co-effect of the porosity and the carbon fiber content. Thirdly, according to fracture surface by SEM, short carbon fiber and SiC substrate in a weak interface, Cf/SiC composite material can effectively be delivered to fiber as the base load, to some extent improved the strength of the composite material. At the same time interface performed as the toughening mechanisms which the fiber were pull out. Composite materials experiment by without adding and adding carbon fiber proformed as brittle fracture and toughness fracture, respectivly. Research on fiber pull-out and crack the matrix of the bridging role of composite materials is the major toughening mechanism.Lastly, in the process of the wear, the debris from the wearing of Cf/SiC composite materials are hard SiC particles fracture and a small amount of carbon fiber. the main wear the form of abrasive wear and oxidation wear. The minimum of wear and tear for the composite rate appear when the carbon fiber content of 13 percent, and the sintering temperature is 1300℃.