Al2O3-SiO2气凝胶的常压制备和性能研究

Preparation and properties of Al2O3-SiO2 aerogel by ambient pressure drying process

以六水氯化铝(AlCl3·6H2O)、正硅酸乙酯(TEOS)为原料,采用溶胶-凝胶法,经老化、常压干燥后,制备出块状乳白色的Al2O3-SiO2气凝胶。气凝胶经过不同温度煅烧处理后,分别进行SEM、TEM、XRD、BET、TG、红外分析等性能分析。结果表明Al2O3-SiO2气凝胶具有良好的热稳定性,SiO2在气凝胶中以不定形存在,Al2O3以针状或长条状的勃姆石(γ-AlOOH)存在,经600~1 000℃煅烧后,转变为γ-Al2O3,当煅烧温度达到1 200℃时,Al2O3与SiO2生成了莫来石相,抑制了γ-Al2O3向α-Al2O3转变。室温下,气凝胶比表面积为692.7 m^2/g,孔洞分布均匀,孔隙率高。随着煅烧温度升高,比表面积、孔容在逐渐减小,孔径稍微增大,当煅烧温度达到1 200℃时,气凝胶比表面积仍有67.3 m^2/g。

Bulk milky white Al2O3-SiO2 aerogels were prepared by sol-gel process after aging and ambient pressure drying with six water aluminum chloride(AlCl3·6 H2O)and tetraethoxysilane(TEOS).Aerogels were calcined at different temperatures,and their properties were analyzed by SEM,TEM,XRD,BET,TG and FT-IR.The results show that Al2O3-SiO2 aerogels had good thermal stability.SiO2 was amorphous in aerogels,and Al2O3 existed in needle-like or long strip boehmite(γ-AlOOH).After calcination at 600-1 000℃,Al2O3 transformed intoγ-Al2O3.When the calcination temperature reached 1 200℃,mullite phase formed by Al2O3 and SiO2,which inhibited the conversion ofγ-Al2O3 toα-Al2O3.At room temperature,the specific surface area of aerogel was 692.7 m^2/g,the distribution of pores was more homogeneous and porosity was higher.With the increase of calcination temperature,the specific surface area and pore volume gradually decreased,but the pore size increased gradually.When the calcination temperature reached 1 200℃,the specific surface area of aerogel was still 67.3 m^2/g.