Experimental and Theoretical Study on Small Gas Permeation Properties through Amorphous Silica Membranes Fabricated at Different Temperatures

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• 作者：Masakoto Kanezashi ; Takanori Sasaki ; Hiromasa Tawarayama ; Hiroki Nagasawa ; Tomohisa Yoshioka ; Kenji Ito ; Toshinori Tsuru
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：September 4, 2014
• 年：2014
• 卷：118
• 期：35
• 页码：20323-20331
• 全文大小：476K
• ISSN：1932-7455

文摘

The sol鈥揼el method was applied to fabrication of amorphous silica membranes, which have different silica network sizes caused by control of the calcination temperatures. The effects of fabrication temperature on small gas (He, H₂, Ne, NH₃, CO₂, N₂, and CH₄) permeation properties through silica membranes were evaluated quantitatively using modified gas translation (GT) model. A silica membrane fired at 550 掳C showed He and H₂ permeances of 8.6 脳 10^鈥? and 5.5 脳 10^鈥? mol m^鈥? s^鈥? Pa^鈥? with He/CH₄ and H₂/CH₄ permeance ratios of 2350 and 1500 at 500 掳C, respectively. The thermal stability was dramatically improved by the fabrication of deposited silica glass intermediate layer because N₂ permeance showed slight change, and the membrane showed a H₂/N₂ permeance ratio above 100 even heat-treated at 750 掳C. The estimated silica network size decreased from 0.385 to 0.347 nm when a membrane was fabricated at 750 掳C, which was consistent with the trend in activation energy of gas permeation. H₂ molecules were more permeable than Ne when passing through amorphous silica membranes despite their larger molecular size (H₂, 0.289 nm; Ne, 0.275 nm), and the H₂/Ne permeance ratios were approximately the same as the Knudsen ratio and were independent of the activation energy of Ne permeation, which was almost the same as that of H₂ permeation.