Porous silica ceramics prepared by sol-gel process-Effect of <TEX>$H_2O/TEOS$</TEX> molar ratio-

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J. Korean Ceram. Soc. > Volume 34(2); 1997 > Article

Journal of the Korean Ceramic Society 1997;34(2): 216.

솔-젤법에 의한 다공성 실리카 세라믹스의 제조-$H_2O/TEOS$ 몰비의 영향-

이진휘, 김화중, 이준¹

서울산업대학교 화학공학과
¹건국대학교 공업화학과

Porous silica ceramics prepared by sol-gel process-Effect of $H_2O/TEOS$ molar ratio-

ABSTRACT

Porous silica ceramics were prepared(with HCI catalyst) using H2O/TEOS molar ratios of 2.6~59.0, with the EtOH/TEOS ratio fixed. After preparing 9 kinds of sol, the followings were investigated; measurement of the gelation time, thermal analyses by TG/DTA, property analyses of the intermediates by FT-IR and X-ray diffractometry with dried samples, analyses of SiO2 polymer by FT-IR, the investigation of specific sur-face area and pore size distribution by N2-adsorption isotherm, and structural change of SiO2 polymer and pore morphology by TEM observation, with samples heat-treated to 50$0^{circ}C$. In the concentrations of in-vestigated compositions and catalyst, gelation time showed a minimum at ca. 11 moles of water per one mole of TEOS, the highest degree of polymerization at ca. 8-18 moles, and the largest specific surface area at ca. 11 moles, which means that the polymerization proceeded fastest at ca. 11 moles of water. In con-clusion, the more water used, the faster the polymerization reaction up to ca. 11 moles, but more than ca. 11 moles of water caused retardation of gelation and resultant reduction of specific surface area.

Key words: Sol-gel process, Porous silica ceramics, $H_2O/TEOS$ molar, ratio