纤维增强Si-C-O气凝胶隔热复合材料的制备与表征

以正硅酸乙酯为原料,通过二甲基二乙氧基硅烷引入碳元素,以乙醇为溶剂,盐酸和氨水为催化剂,莫来石纤维为增强相,采用溶胶–凝胶、超临界干燥和1 200℃高温裂解工艺制备Si-C-O气凝胶隔热复合材料,并对材料的结构和性能进行了分析和表征。结果显示：1 200℃裂解得到的Si-C-O气凝胶复合材料为黑色且加工成型性较好,纤维表观体积密度为0.15 g/cm3时,800℃和1 000℃热导率分别为0.031 9 W/（m K）和0.043 0W/（m K）。纤维表观体积密度增大（0.15～0.30 g/cm3）,复合材料的拉伸和压缩强度增大,密度为0.25 g/cm3时,抗弯强度最大。1 200℃裂解得到的Si-C-O气凝胶的比表面积为217.7 m2/g,空气中1 000℃煅烧后,比表面积为208.6 m2/g。Si-C-O气凝胶复合材料在1 000℃空气中煅烧后没有出现收缩。

Preparation and Characterization of Si-C-O Aerogel Composites for Thermal Insulation

Si-C-O aerogel and its composite were synthesized by sol–gel,supercritical drying,and pyrolysis at 1 200 ℃,tetraethyl orthosilicate and dimethyldiethoxysilane as precursor,enthanol as solvent,hydrochloric acid and ammonia as catalysts,mullite fiber as reinforcement were used.The structure and properties of the materials were characterized.The result shows that when it is carbonized at 1 200 ℃,the appearance of Si-C-O aerogel composite changes from white to black with good machining ability.When the bulk density of the mullite fiber is 0.15 g/cm3,the thermal conductivities of mullite fiber reinforced Si-C-O aerogel composite at 800 ℃ and 1 000 ℃ are 0.031 9 W/(m K) and 0.043 0 W/(m K),respectively.Increase of the bulk density of mullite fiber from 0.15 g/cm3to 0.30 g/cm3results in increasing tensile strength and compressive strength.The bend strength is highest when the bulk density of mullite fiber is 0.25 g/cm3.The specific surface area of the Si-C-O aerogel at 1 000 ℃ is 208.6 m2/g.The Si-C-O aerogel composites do not shrink keeping their size unchanged until 1 000 ℃ during heat treatment.