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Ion exchange sol - gel prepared composite membranes and their structure and properties of Al_2O_3-ZrO_2

Author: ZhangZuo
Tutor: WangLianJun；LiJianSheng
School: Nanjing University of Technology and Engineering
Course: Environmental Engineering
Keywords: anionic exchange method sol-gel method boehmite sol zirconium hydroxide sol Al2O3-ZrO2 composite membrane thermal stability
CLC: TB383
Type: Master's thesis
Year: 2005
Downloads: 279
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Abstract


The methods of preparing stable boehmite sol and zirconium hydroxide sol by anionic exchange method using inorganic compounds as raw materials were investigated in this dissertation,and forming-membrane capability of the sols were also investigated on the base of the it.The reaction mechanism of the process of preparing the stable uncrystalloid aluminum hydroxide sol and boehmite sol by anionic exchange method was primarily discussed. The boehmite sol and zirconium hydroxide sol were blended to prepare Al2O3-ZrO2 composite sol,and the Al2O3-ZrO2 composite membranes supported by porous α-Al2O3 substrates were prepared.The phase components,thermal stability,pore configuration,microcosmic structure and gas permeation were characterized. The dissertation was mainly discussed as follows:The OH" ions were introduced much more slowly by the methods of preparing boehmite sol by anionic exchange method,and the Cl" ions could be wipe off at the same time in the process of preparing.The stable,transparent uncrystalloid aluminum hydroxide sol in which almost no Cl" ions was prepared by this method in the dissertation.The pH of the sol was 6.46. This sol could be transformed to stable boehmite sol in which particle size of boehmite was almost the same by aging some hours.The forming-membrane capability of the boehmite sol was very nice,and the defect-free γ-Al2O3 membranes supported by hollow fiber were prepared.In the processing of preparing zirconium hydroxide sol by anionic exchange method,the pH and concentration of solution could make great effect on stability of the sol.When the pH was 3.0 and the concentration was 0.5M,the sol was transparent and stable.It didn’t gelatificate after placing a long time.But the forming-membrane capability of this sol is not good, the defect-free t-ZrO2 membranes supported by hollow fiber could not be prepared.The defect-free Al2O3-ZrO2 composite membranes supported by hollow fiber and ceramic tube were prepared by anionic exchange sol-gel process from zirconyl chloride and aluminum chloride as their precursors.The effects of the mole ratio of alumina and zirconia（r） in composite membranes on crystal temperature and crystal phase were investigated in detail.The results showed that the thermal stability of composite membranes was greatly improved compared to pure Al2O3 or ZrO2 membranes. When the content of Al2O3 was high（r>l）,there were crystal phase of t-ZrO2 or blended crystal phases of t-ZrO2

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