碳热还原温度对耐高温纤维增强碳化硅多孔材料组织结构的影响（英文）

Effect of Carbothermal Reduction Temperature on Microstructure of Fiber Reinforced Silicon Carbide Porous Monoliths with High Thermal Resistance

本研究目的是开发一种耐高温纤维增强碳化硅多孔块状材料.以纤维增强间苯二酚-甲醛/氧化硅复合气凝胶为前驱体,经过1 300～1 500℃碳热还原制备了纤维增强碳化硅多孔材料.采用XRD、SEM、TEM、氮气吸附孔结构分析仪和压汞仪对纤维增强碳化硅多孔材料的物相组成、微观形貌和孔结构进行了表征,结果表明：纤维增强碳化硅多孔材料由β-SiC和莫来石纤维组成,随着碳热还原温度的升高,样品中的SiC纳米晶颗粒团聚成大块,最终在1 500℃生成SiC晶须,升高碳热还原温度会导致样品中大孔的增多和纳米孔的消失以及比表面积的降低.热分析结果表明纤维增强碳化硅多孔材料在空气中的耐温性高达1 300℃.纤维增强碳化硅多孔材料的密度为0.330～0.345 g·cm^-3,孔隙率在89％以上,室温下热导率为0.06～0.07 W· m^-1·K^-1.

The objective of this work is to develop fiber reinforced silicon carbide porous monoliths （FRSiCs） with high thermal resistance at low carbothermal reduction temperature. FRSiCs were prepared by carbothermal reduction of fiber reinforced resorcinol-formaldehyde/silica （FR-RF/SiO2） aerogel at different temperatures starting at 1 300 ℃. The evolution of phase composition, morphology and pore structure of FRSiC with carbothermal reduction temperature were investigated by X-ray diffractometer （XRD）, scanning electron microscope （SEM）, transmission electron microscope （TEM）,N2 adsorption/desorption analyzer and mercury intrusion porosimeter （MIP）. The results reveal that FRSiCs consist ofβ-SIC and mullite fibers transformed from aluminium silicate fibers. Along with the increase of carbothermal reduction temperature, SiC nanoerystals aggregate to lump and transform to whiskers, and pore size becomes larger.Thermalanalyses of FRSiCs indicate that FRSiCs have excellent thermal stability in air up to 1 300 ℃. FRSiCs have a high porosity more than 89%, and their apparent densities and thermal eonductivities are 0.345-0.330 g. cm^-3 and 0.06-0.07 W· m^-1· K^-1, respectively.