陶瓷前驱体配比对Si-Zr-B掺杂沥青基炭材料抗氧化性能的影响

以SiC、ZrC、ZrB₂前驱体和二甲苯可溶煤沥青为原料共裂解制备了Si-Zr-B掺杂沥青, 掺杂沥青经共炭化、冷压成型以及高温热处理得到了Si-Zr-B掺杂沥青基炭材料。采用XRD、SEM、EDS等手段分析了掺杂沥青基炭材料的组成和微观形貌, 并研究了其在1500℃静态空气环境中的氧化行为。结果表明, 随着SiC前驱体含量的降低, Si-Zr-B掺杂沥青基炭材料的失重率呈现先减少后增大的趋势, 当原料中SiC、ZrC和ZrB₂前驱体质量比为1:2:1时, 所制备的样品具有较好的抗氧化性能, 它在1500℃氧化4 h, 失重为27.5wt%, 氧化深度为0.7 mm。在Si-Zr-B掺杂沥青基炭材料表面氧化形成的致密的SiO₂-ZrO₂-B₂O₃玻璃态阻氧层可以有效降低氧化性气氛向材料内部扩散的速率, 提高其抗氧化性能。

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℃ 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℃ 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.