| SiC fibre has many advantages, such as high strength and hardness, good thermal stability and oxidation resistance, low thermal expansion coefficient and low density and so on. It is an ideal material used in the reinforced metal alloy. However, due to the interface reaction between the SiC fibre and metal alloy at high temperature, which affects the performance of SiC fiber reinforced metal matrix composites. Therefore, it is very important to find the protective coatings on the surface of SiC fibre.In this paper, a coating layer composed of alumina and alumina/silica were prepared on the surface of SiC fibers through an improved sol-gel process. Some means sucha as SEM, EDS, TG-DSC and XRD were used to character the samples. The parameters for the colloid formation and coating preparation were studied systematically.Alumina sol was prepared firstly, the optimal conditions were as follows:The mol ratio of aluminium isopropo, water and nitric acid is 1:90:0.15, the concentration of nitric acid is 1 mol/L, the hydrolysis temperature is 85℃ and the hydrolysis time is 1 h.The aluminium isopropo is added into the solution fractionally after sufficient grind, and the oxalic acid is added according to a fixed propotion:1 g oxilic acid/100 mL solutionThe aluminia and aluminia/silica composite film was coated on the SiC fibers. The effects of SiC pretreatment, the coating times, and oxalic acid addition on the morphology of aluminia and aluminia/silica composite layer was implored. The results showed that the thickness of coatings was increased, and the thickness of aluminia layer is about 589 nm, and the thickness of aluminia/silica composite layer can bereached 500 nm,In the antioxidant experiments, the SiC fibers with aluminia or aluminia/silica protective layer show enhanced antioxidant ability compare with pure SiC fibers. In the tensile tests, the composite fibers present the same tensile strength compared to poriginal SiC fibers. |
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