溶胶-凝胶法制备不对称氧化铝膜

以异丙醇铝为原料，过量的水、醇溶剂的存在有利于异丙醇铝水解．适宜的水铝比H₂O／Al^3＋为100：1；醇铝比ROH／Al^3＋为5：1；酸胶溶剂的浓度H^＋／Al^3＋为0．07：1．溶胶的雾化快速胶凝法，大大缩短了凝胶干燥的时间，采用这种方法能容易地制备膜厚均匀、且无龟裂的无机氧化铝膜．适宜的溶胶浓度为0．5～1．4mol AlOOH／L溶胶，喷雾距离＜200mm，膜厚与溶胶浓度、喷雾时间成正比，与喷雾距离的平方成反比．用γ-AlOOH溶胶对基质膜作进一步的修饰制备不对称氧化铝膜时，勃母石溶胶的初始晶粒的大小决定着氧化铝膜的孔径，勃母石溶胶的胶体粒子的直径决定着形成的不对称膜的稳定性．勃母石溶胶的胶体粒子的平均直径与支撑体基质膜表面的最可见孔径相当时，喷涂于基质膜表面的溶胶快速胶凝后，能形成无裂纹和针孔的均匀凝胶膜．以表面最可几孔径为0．1μm的氧化铝膜为基质膜，雾化溶胶胶粒平均直径为100nm左右的勃母石溶胶，喷涂于基质膜表面，快速胶凝后于400℃焙烧形成的支撑γ-Al₂O₃膜孔径为3nm．

Preparation of Asymmetric Alumina Membrane by Sol-Gel Techniques

The clear stable sols were obtained above 50℃ with about 100:1 suitable H₂O/Al³⁺mol~ ratio, 5:1 ROH/H⁺, 0.07:1 H⁺/Al³⁺ concentrations of peptizant acid. Crack-free alumina membranes were obtained by rapid gelation processing of sols in shorten gel time. The suitable concentration of the sol was between 0.5～1.4 mol AlOOH/l sol, the suitable spraying distance shorter than 200mm. The pore size of the membrane was influenced by the size of boehmite grain, the pore size of γ-Al₂O₃ prepared by the boehmite sol with 3 nm grain size was about 3nm. Asymmetric alumina membrane was obtained by further modifying alumina supporter by using the clear stable sol. When the mean diameter of the colloidal particles was equivalent to the most pore size of the supporter, the crack-free gel film can be stably deposited on the supporter. With 0.1μm of the most pore size as the supporter, the γ-Al₂O₃ membrane of 3nm pore size was obtained by using the spraying sol of 100nm colloidal particles.