Abstract: This work aims to investigate the high-temperature resistance and the thermal insulation of alumina aerogels at high temperatures.Alumina aerogels were prepared by the sol-gel method plus supercritical drying using aluminum isopropoxide as the precursor,ethanol as the solvent,and glacial acetic acid as the catalyst.The obtained alumina aerogels were then heat-treated at different temperatures (25,150,250,300,500,600,850,1 000 and 1 200 ℃) for 6 h.The effects of the heat treatment temperature on the phase composition,microstructure,pore structure and specific surface area of the alumina aerogels were studied by FT-IR,XRD,TGA,DSC,SEM,TEM and BET.The results show that:(1)with the increasing heat treatment temperature,the prepared alumina aerogels undergo phase transition;when the temperature is ≥600 ℃,the sample mass hardly changes;(2)when the temperature is 850 ℃,the prepared alumina aerogel still maintains a three-dimensional porous network skeleton structure,the average pore size is still less than 69 nm (the free path of air molecules),and there is no obvious macropore;(3)the specific surface area of the prepared alumina aerogel is 458 m²·g^-1 at room temperature,321 m²·g^-1 after heat treatment at 850 ℃,and 102 m²·g^-1 after heat treatment at 1 000 ℃.

Key words: alumina aerogel, high temperature resistance, insulation material, specific surface area

摘要： 为了研究氧化铝气凝胶的耐高温性能和高温下的隔热水平,以异丙醇铝作为前驱体,乙醇作为溶剂,冰醋酸为催化剂,采用溶胶凝胶法经超临界干燥制备氧化铝气凝胶,并在不同温度下(25、150、250、300、500、600、850、1 000和1 200 ℃)保温6 h热处理,并通过FT-IR、XRD、TGA、DSC、SEM、TEM、BET等方法研究了热处理温度对氧化铝气凝胶物相组成、显微形貌、结构及比表面积的影响。结果表明:1)随着热处理温度的升高,制备的氧化铝气凝胶会发生相变,当热处理温度≥600 ℃后,随热处理温度继续升高,试样几乎不发生质量变化;2)当热处理温度为850 ℃时,制备的氧化铝气凝胶仍保持三维多孔网络骨架结构,平均孔径仍小于空气分子自由程69 nm,且无明显大孔;3)制备的氧化铝气凝胶常温下比表面积为458 m²·g^-1、850 ℃热处理后为321 m²·g^-1,经1 000 ℃热处理后仍可达到102 m²·g^-1。

关键词: 氧化铝气凝胶, 耐高温, 隔热材料, 比表面积