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采用酸碱两步溶胶凝胶法,以仲丁醇铝为前驱体,硝酸/氨水为酸/碱催化剂,通过酒精超临界干燥制备了氧化铝气凝胶。制备得到的气凝胶块体密度低(50~120kg/m3)、比表面积高(400~500m2/g),具有介孔结构和良好的热稳定性。采用TEM、FTIR、XRD、BET、DSC/TGA等手段表征了氧化铝气凝胶热处理前后的结构和性能。实验表明,制备的氧化铝气凝胶为拟勃姆石结构,经800和1000℃热处理后分别变为γ-Al2O3和δ-Al2O3,对应的比表面积仍分别高达381和183m2/g。添加少量的乙酰丙酮制备的氧化铝气凝胶在热处理前后晶相和比表面积的变化趋势跟未添加的相同,但具有更高的热稳定性。此外,研究了水、氨水和络合剂乙酰丙酮的用量对气凝胶的微结构及比表面积和孔径的影响。
Alumina aerogels were prepared by acid-base two-step sol-gel method using aluminum sec-butoxide as precursor and nitric acid / ammonia as acid / base catalyst by alcohol supercritical drying. The prepared airgel block has low density (50-120kg / m3) and high specific surface area (400-500m2 / g), has the mesoporous structure and good thermal stability. The structure and properties of alumina airgel before and after heat treatment were characterized by TEM, FTIR, XRD, BET and DSC / TGA. Experiments show that the prepared alumina airgel is a pseudo-boehmite structure, and after heat treatment at 800 and 1000 ° C, it turns into γ-Al2O3 and δ-Al2O3, respectively, and the corresponding specific surface areas are still as high as 381 and 183 m2 / g, respectively. Alumina airgel prepared by adding a small amount of acetylacetone has the same trend of crystallite and specific surface area before and after heat treatment, but has the same higher thermal stability. In addition, the effects of the amount of water, ammonia and complexing agent acetylacetone on the microstructure and specific surface area and pore size of aerogels were investigated.