摘要
为优化氧化铝气凝胶的制备工艺,以异丙醇铝(AIP)为前驱体,乙醇(EtOH)为溶剂,乙酸(HAc)为催化剂,通过溶胶-凝胶法经超临界干燥方式制备了 Al2O3气凝胶.研究乙醇用量[n(AIP)∶n(EtOH)∶n(H2O)∶n(HAc)分别为 1∶8∶0.8∶2、1∶12∶0.8∶2、1∶16∶0.8∶2、1∶20∶0.8∶2]及乙酸用量[n(AIP)∶n(EtOH)∶n(H2O)∶n(HAc)分别为 1∶16∶0.8∶1、1∶16∶0.8∶2、1∶16∶0.8∶3、1∶16∶0.8∶4]对 Al2O3 气凝胶孔结构及比表面积的影响.结果表明:乙醇通过影响Al—OH基团的缩聚概率来影响Al2O3气凝胶的孔结构,乙酸通过影响反应速率来影响Al2O3气凝胶的孔结构.当n(AIP)∶n(EtOH)∶n(H2O)∶n(HAc)=1∶16∶0.8∶2时,制备的Al2O3气凝胶具有多孔的显微结构,且内部孔径普遍小于空气分子平均自由程,具有优良的隔热特性,密度低至0.20 g·cm-3,在25、1 000 和 1 200 ℃下比表面积分别为 458、102、51 m2·g-1.
Abstract
To optimize the preparation of Al2O3 aerogels,the sol-gel method was combined with supercriti-cal drying,using aluminum isopropoxide(AIP)as precursor,ethanol(EtOH)as solvent,and acetic acid(HAc)as catalyst.The effects of the ethanol addition[n(AIP)∶n(EtOH)∶n(H2O)∶n(HAc)=1∶8∶0.8∶2,1∶12∶0.8∶2,1∶16∶0.8∶2,and 1∶20∶0.8∶2]and acetic acid addition[n(AIP)∶n(EtOH)∶n(H2O)∶n(HAc)=1∶16∶0.8∶1,1∶16∶0.8∶2,1∶16∶0.8∶3,and 1∶16∶0.8∶4]on the pore structure and specific surface area of Al2O3 aerogels were studied.The results show that ethanol affects the pore structure of Al2O3 aerogels by affecting the condensation probability of Al—OH groups,and acetic acid affects the pore structure of Al2O3 aerogels by affecting the reaction rate;when n(AIP)∶n(EtOH)∶n(H2O):n(HAc)=1∶16∶0.8∶2,the Al2O3 aerogel has a porous microstructure,and its internal pore diameter is generally smaller than the average free path of air molecules,showing e×cellent thermal insulation characteristics,low density of 0.20 g·cm-3,and the specific surface area of 458,102,and 51 m2·g-1 at 25,1 000,and 1 200 ℃,respectively.
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