The Fabrication Of Continuous SiC Fiber By Chemical Vapor Deposit

SiC fiber has been used in different high technology domain for its high strength, high modulus and refractory properties. There have been commercial available CVD-SiC fiber products which are prohibited to sale to our country. Although we have started to research this at home and produced some products, the properties of that fall behind the similar foreign products. It is necessary to develop the research about CVD-SiC fiber.SiC fiber is produced by radioheating method which is a perfect technique for it reduces the environment pollution by the way of non-contact heating. At the same time the deposit rate and the strength of SiC fiber are insured by the symmetrical and adjustable heating temperature.SiC fiber is deposited on the tungsten wire which is used as substrate. The result shows that deposit velocity and density of SiC fiber increase with increasing temperature. But the higher temperature will result in the coarse surface and decreasing the tensile strength of SiC fiber.Optimum process conditions that deposit electricity (deposit temperature) is 6.5A, deposit time is 2V, flow rate of argon is 1.7ml/min, the mol ratio of CH₃SiCl₃ and CH₃SiHCl₂ is 2:1, flow rate of hydrogen is 1.7ml/min. Primary and secondary sequence of parameters is deposit temperature, deposit time, flow rate of argon, the mol ratio of CH₃SiCl₃ and CH₃SiHCl₂ flow rate of hydrogen and experiment error.Tensile test was conducted at room temperature for CVD SiC fibers. The results show that the tensile strength of the fiber can be described by Weibull distribution function. Weibull modulus and the average tensile strength of SiC fiber decrease with increasing of gauge length of sample. Tensile strength of SiC fiber has a close relationship with surface properties and morphologies.Except including silicon and carbon elements, there are some other impurities such as W, O in SiC fiber in deposition. These impurities result in the increasing ofSiC fiber defects which decrease the tensile strength of SiC fiber. We can reduce those impurities by improve the purity of raw materials and increase leak tightness of reactor.