Research On Pore Alumina Composite Membranes

In this study, synthesis and approach of supported membranes of A12O3, and its modification composite membranes are described, such as Al2O3-SiO2, Al2O3-TiO2, A12O3-SiO2-TiO2, and Al2O3-SiO2-TiO2-ZrO2 membranes, made by Sol-gel process. Crystallization of sol-gel desired powders has been investigated by DTA-TG, XRD; microstructure and elements distribution are measured by SEM, AFM and EPMA methods; chemical stability is tested by AAS method.Research results show that a-Al2O3 ceramic substrate with porosity 46.8% have better combination with Al2O3 composite membranes. A12O3 and A12O3 composite sols are made by two methods, one is Abio-Al2O3 hydrolysis process, Abio-Al2O3 sol prepared by AlCl3-6H2O and ammonia and then age ten month, SEM indicates that there are narrow pore size distribution, so its further research should be paid attention to. Another is using metal tert-amylonides as chemical precursors, by different hydrolysis of aluminum-tri-sec-butoxide, tetraethyl lorthosilicate (TEOS), titanium ethoxide and zirconium oxychloride on a-Al2O3 ceramic substrate, which is principal method in this study.Peptized with lm/1 HNO3, PH value of Al2O3-TiO2 sol is about 3~7,pH value of A12O3-TiO2,Al2O3-ZrO2,Al2O3-SiO2-TiO2 and Al2O3-SiO2-TiO2-ZrO2 sols are about 1.2-2.5. Dipping times and heat treatment behavior have an important effect on membrane, in this experiment, dipping times about 3-4 is good; Repeating dipping-heat treatment process is due to make membrane and that repeat of dipping-heat treatment process are disadvantageous.Changing the ratio of Al: Si: Ti: Zr sol according to 1:1:1:1, 1:4:1:1, 2:1:1:1, 4:1:1:1 and 4:3:3:3, different pore size distribution of A12O3 composite membrane could be obtained. SEM, AFM, EPMA micrographs indicate that pore size distribution of membranes is narrow; thickness of membrane is about l-2um and gradual interface between membrane and substrate is continuous and uniformity. XRD of A12O3 composite membrane shows that there are existing several crystalline phases such as Al2O3, SiO2, TiO2, Al2SiO5, and ZrO2.Using material, which composition is basically same to substrates through grinding, and then dipping its slurry on substrate with heating 800 ℃ and then sintering at 1400℃. There was no crack on the surface of coating. Distinguish between coating and substrate may use SEM, from SEM micrographs of cross section of coating, there is gradated pore structure, while pore-forming agent is no good for coating.In above, SiO2, TiO2 and ZrO2.doped alumina membrane are successfully prepared by the Sol-Gel method on a-Al2O3 ceramic substrate in this study, which have good performance.