以陶瓷纤维制成的高温隔热瓦为骨架,真空浸渍氧化铝溶胶,再经过凝胶、老化和超临界干燥制备出氧化铝气凝胶复合高温隔热瓦,研究了其在不同温度处理后(最高温度1 400℃)的微观结构、隔热和力学性能.结果表明:气凝胶复合高温隔热瓦在1 400℃保温30 min后线收缩率仅为2％;随着热处理温度升高,气凝胶颗粒发生熔并、长大,气凝胶从填充纤维空隙到不断收缩,但对纤维骨架没有明显影响;隔热瓦的室温、高温热导率均显著降低;在热面1 400的背温测试中,复合后材料的背温从945℃降到870℃;复合后隔热瓦的力学性能略有增加;但是1 200～1 400℃的压缩强度下降较大.可见,气凝胶复合高温隔热瓦可改善其隔热性能,但在高温下力学性能下降.
Using ceramic fibrous insulating tiles as skeleton,the alumina sols via sol-gel process were infiltrated into the tiles via vacuum infiltration,followed by gelation,aging and supercirtical drying to fabricate the aerogels impregnated high-temperature insulating tiles.The aerogel/tile composites' microstructure,thermal and mechanical properties at high-temperatures (up to 1400℃) were investigated.The results showed the composites exhibited a small linear shrinkage of 2％ after hating at 1400℃ for 30 min.With increasing heating temperature,the aerogels' particles grew and condensed;the aerogels changed from filling the fibers' pores to being condensed,and to being mainly attached to the fibers' surface,but such evolution did not obviously affect the fibrous skeleton.After the aerogel impregnation,the specimen's room-temperature and high-temperature thermal conductivities decreased significantly,and the cold-face temperature dropped from 945℃ to 870℃ in the back-temperature tests.In addition,although the composites' room-temperature mechanical properties increased slightly,the high-temperature compressive strength drastically degraded at 1200℃ and 1400℃.
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