Comparative Study of Structure of Silica Gels from Different Sources |
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Authors: | Kanichi Kamiya Ai Oka Hiroyuki Nasu Tadanori Hashimoto |
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Affiliation: | (1) Department of Chemistry for Materials, Faculty of Engineering, Mie University, Kamihama-cho, Tsu-shi, Mie-ken, 514-8507, Japan |
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Abstract: | The medium-range-network structure of silicas from different sources was comparatively examined by X-ray diffraction, IR and NMR analyses. Silica gels made through the conventional sol-gel route were found to have a different structure from silica glass, and considered to be composed of 4-fold siloxane ring units, irrespective of preparation conditions. Amorphous silicas in rice-hulls and bamboo leaves showed structure data close to silica glass, being suggested to consist mainly of 6-fold siloxane ring units. The modified sol-gel method, in which siloxane oligomers containing cyclic siloxane tetramers may have been ring-opened and polymerized under the catalytic reaction of NaOH or NH4F in the water-free solution, provided the silica gel of which structure was very similar to silica glass. |
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Keywords: | sol-gel silicas biology X-ray diffraction IR NMR |
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