Preparation And Characterization Of High Temperature Silicon-based Ceramic Separation Membrane Materials

Ceramic membrane separation technology has the advantage of high temperature resistance, corrosion resistance, high separation efficiency, low energy consumption, and green, which was applied widely in food, chemical industry, biological medicine and environmental protection. Due to the pervasive application and increasingly high requirements of the inorganic ceramic membrane materials, traditional inorganic materials have been not suitable for hostile environment such as high temperature and corrosion. Hence, it has been the the main research goals to develop new ceramic membrane materials and reduce cost. Herein we focused on studying the preparation of silicon carbide ceramic membrane support and possible ceramic separation membrane materials of yttrium silicate. The main work covers following sections:(1) Silicon carbide ceramic membrane support was prepared at low temperature by sol packing method.Silicon carbide ceramic membrane support of 49.58% porosity was prepared at 1100 ℃. The diameter of SiC ceramic membrane support green increased after sintering. Line shrinkages of the sample decreased and porosities increased with the increase of sintering additives content. These indicated that using aluminium nitrate nonahydrate and yttrium nitrate hexahydrate as sintering aid not only can reduce the sintering temperature, but also form pore and improve changes of the support shape. The negative linear shrinkage of the sample sintered at 1100℃ was as low as 0.83% when we used 20μm SiC,6 wt% starch,30 wt% sintering aids.(2) Silicon carbide hollow fiber ceramic membrane of asymmetric microstructure was prepared by phase inversion method.53.83% porosity of the SiC ceramic membrane tube was prepared by phase inversion combined solid sintering without adding pore-forming agent in oen step. The SiC ceramic membrane tube possessed asymmetric microstructure of fingerlike layer-spongelike layer-fingerlike layer, which is helpful to improve permeability of ceramic membrane.The influence of sintering temperature on shrinkage changes was very small, axial and radial line shrinkages were stable at 10.1% and 9.0% respectively.(3) Highly purity yttrium silicates powder was synthesized by EDTA-citric acid complexing process for the first time. The synthesis mechanism was investigated.Nano-sized a-Y2Si2O7 powder was obtained from the precursor solution pH 9.38 at higher than 1050℃. Y2SiO5 powders were obtained at the pH 4 in this work. This is mainly resulted from different complexation degree of both EDTA and citric acid with TEOS in the hydrolysis-polycondensation reactions at different pH values. The obtained α-Y2Si2O7 powders possessed grape-like structure. This structure with large number of grain boundaries can potentially provides many special physical tunnels and controlled mechanical strength in favor of gas permeability as separation membrane materials.