The membrane is porosity in nano dimensions and was developed through a low cost process. Shirin Khanmohammadi, the research manager told Mehr News science and technology correspondent that the research group improved the thermal stability along with its nanoporous structure, through adding compounds such as yttria and modification of the silica ceramic membrane structure.
“Physico-chemical structure of a membrane is a decisive factor of determining important properties as thermal stability, permeability, selectivity, and sedimentation capacity, and an optimum structure would be achieved through simple methods of eliminating minor defects from the membrane surface or controlling the concentration of membrane composition and process temperature,” said Khanmohammadi, “our research succeeded in development of ceramic membrane with nanoporousity, improved thermal and hydrothermal properties,” she added.
“The cavities achieved have a mean diameter of 9.1nm and show a good thermal stability in temperatures up to 800 degrees centigrade, with final trilayer thickness of 680nm,” said the research manager. “Sol-Gel process is the most prevalent method in producing ceramic membranes; among its advantages are production of homogenous material with high purity and higher specific surface area, the capability to control porosity size and microstructure,” she noted.
Khanmohammadi added that the research project developed microporous trilayered silica-yttria on an alpha-alumina substrate and gamma-alumina substrate. “The alpha-alumina substrate was prepared as tablets by thermal annealing and pressing alpha-alumina powder; the colloid and polymeric sols were placed in the substrate to form intermediate layer of gamma-alumina and membranous layer of silica-yttria through immersion method, and after drying, the intermediate level was subject to 600 degrees Celsius and membranous layer was subject to 500 degrees Celsius,” she detailed.
Ceramic membranes have applications in pharmaceutical, food, chemical and petrochemical industries to filter out light gases such as hydrogen, nitrogen and methane; the major problem of this type of membranes, however, is their lack of stability in the presence of humidity and heat, which negatively affect its porous structure and causes malfunctioning. The research project used AFM, FESEM, FTIR, and XRD tests, and nitrogen absorption and desorption.
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