Influence of SiO_2 Coating Preparation Process on the Oxidation Resistance of 3-D Carbon Fiber Braids

The SiO2 coating on 3-D carbon fiber braids was prepared by the sol-dipping method. And the influence of coating preparation process on the oxidation resistance of the braids was also studied. The results show that the oxidation resistance of the dipped sample is improved 300℃ comparing with the raw braids, when the braids are treated by nitric acid. Then it is dipped with the sol, of which the viscosity is between 0.01-0.012(Pa·s)and the molecule growth model is linear. The thickness of coating is about 0.5μm. The oxidation resistance of dipped samples decreases when the thickness of coating is either thicker or thinner, because the coating is coated asymmetrically or combined badly with fiber surface.