The membrane has nanometric pores and was produced through a simple and cost-effective method. Ceramic membranes are usually used in pharmaceutics, foodstuff industries and chemicals and petrochemicals for the separation of small gases such as He, H2, N2 and CH4. The main problem in the application of these types of membranes is their instability in humid and hot places. This problem rearranges the porous structure and decreases the performance of the membranes. In this research ("Micro-porous silica–yttria membrane by sol–gel method: Preparation and characterization"), efforts have been made to increase thermal stability of the silicate ceramic membrane as well as preserving its nanoporous structure by adding yttrium oxide to change the structure of the membrane. Physical and chemical structure of a membrane determines its important characteristics, including diffusivity, selectivity or sedimentation. It is possible to create a desirable structure by the simple method of elimination of problems on the surface of the membrane and by controlling the concentration of raw materials and the process temperature. Alpha-alumina substrate was prepared through the pressing of alumina powder method and thermal cooking in form of tablets. Colloid and polymeric sols were deposited on the substrate to create the middle layer of gamma-alumina and the membrane layer of silica/ytteria through immersion method.
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