以聚碳硅烷(PCS)和三甲胺基环硼氮烷聚合前驱体(PBN)进行共聚合制得复合前驱体, 以此为原料采用高压裂解发泡技术制备了一种氮化硼/碳化硅(BN/SiC)复相开孔泡沫陶瓷. 由包含不同比例组分的起始前驱体所制得的泡沫陶瓷的孔隙直径在1~5 mm, 体积密度在0.44~0.73 g/cm3之间. 对该陶瓷材料的微观结构和性能的研究表明, 由于BN相的引入使得BN/SiC复相泡沫陶瓷在800~1100℃的抗氧化性能有了显著的提高; 其压缩强度随着引入BN比例的增加而提高, 约为纯SiC泡沫陶瓷的5~10倍. 其中以组分重量比为1:1的起始复合前驱体所制备BN/SiC复相多孔陶瓷在1500℃时的导热系数仅为4.0 W/(m·K); 对其进行隔热性能测试, 材料热面中心温度为1400℃时, 其背面中心温度仅为280℃; 采用有限差分法数值模拟背部升温历程, 将其有效导热系数代入计算模型, 得到材料背部中心温度升温历程的数值模拟结果, 与实际升温历程基本一致.
A kind of BN/SiC open-cell ceramic foams were fabricated from complex co-polymeric precursors of polycarbosilane and tris(methylamino)borane [B(NHCH3)3] using a high-pressure pyrolysis foaming technique. The obtained foams exhibited cell sizes ranging from 1 mm to 5 mm with bulk densities varying from 0.44 g/cm3 to 0.73 g/cm3, depending on the proportion of the starting precursors. Studies on the microstructure and thermal property of the porous ceramics showed that the addition of BN into SiC could improve dramatically the oxidation resistance from 800 to 1100℃. The compression strength of the composite foams was 5–10 times higher than that of pure SiC foam, which increased with increasing of BN content in the ceramic foams. Heat insulation performance of the ceramic foam fabricated from the starting precursors with a proportion of 1:1 in weight was analyzed by a device designed for insulation performance at high-temperature. When the temperature at the center point of hot surface of the foam was 1400℃, the temperature at the center point of the back achieved only 280℃. The heating history of the foam was simulated by finite-difference method, and the results showed that thermal conductivity of the composite foam was 4.0 W/(m·K), which was almost identical to the experimental result.
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