Effects of Ceramic Precursor Ratio on Antioxidation Properties of Pitch-based Carbon Materials Doped with Si-Zr-B

The Si-Zr-B doped coal-tar pitch was synthesized by co-pyrolysis of xylene soluble pitch, silicon carbide precursor, zirconium boride precursor, and zirconium carbide precursor. The pitch-based carbon materials doped with Si-Zr-B were prepared through co-carbonization, cold moulding and followed by high temperature heat treatment from the obtained Si-Zr-B doped coal-tar pitch. The phase composition and microstructure of the carbon materials were characterized by XRD, SEM and EDS. The oxidation behavior of specimens was tested at 1500°C in static air. The results show that weight loss of the doped carbon materials is increased firstly and then decreased with the decrease of content of silicon carbide precursor in Si-Zr-B doped coal-tar pitch. The doped carbon materials obtained from Si-Zr-B doped coal-tar pitch, with a mass ratio of the polycarbosilane, zirconium carbide precursor and zirconium boride precursor at 1:2:1, shows an excellent oxidant resistance. After oxidation in air at 1500°C for 4 h, its weight loss and oxidation depth is 27.5wt% and 0.7 mm, respectively. A dense SiO2-ZrO2-B2O3 glassy oxide layer which formed during oxidation in air can effectively reduce the rate of oxygen diffusion and thus improve the oxidation resistance of the carbon materials derived from the doped coal-tar pitch. 1312 无 机 材 料 学 报 第 31卷