졸-겔 변환변수가 SiO<SUB>2</SUB>의 물성에 미치는 영향

정경택; 이동조; 설용건

HWAHAK KONGHAK, Vol.29, No.2, 176-182, April, 1991

Export Citation

졸-겔 변환변수가 SiO₂의 물성에 미치는 영향

Effect of Sol-gel Transition Parameters of TEOS on the Properties of SiO₂

정경택, 이동조, 설용건

초록

TEOS(tetra-ethyl-ortho-silicate)의 졸-겔 변환변수가 SiO₂의 특성에 미치는 영향을 알아보기 위해 초기 TEOS의 가수분해 반응에 의한 졸-겔 변환과정부터 최종적으로 실리카겔의 소성으로 얻어지는 SiO₂까지의 전체적인 과정을 살펴보았다. TEOS의 초기 가수분해 변수는 겔의 형태와 특성에 영향을 주는 것 뿐만 아니라 소성후 겔의 겉보기 밀도와 표면적에도 영향을 주고 있었다. 산촉매하에서 반응온도가 높아짐에 따라 졸-겔의 섬유인출구간이 작아졌다. 폐쇄계의 경우 섬유가 인출이 되지 않았다. TEOS의 초기 가수분해에서 H₂O의 증가는 가수분해속도를 증가시켰고 촉매는 염기의 경우가 산보다 빠른 가수분해를 나타내었다. 산의 경우 물의 증가는 bulk SiO₂ 겔에서 큰 1차입자를 형성한 반면 염기의 경우 물의 증가는 bulk 겔이 형성되기 전에 미세분말이 형성됨으로 해서 bulk 겔이 형성되지 않았다.

In order to evaluate the effects of sol-gel transition parameters of TEOS(tetra-ethyl-ortho-silicate)on properties of SiO₂, we studied whole process from sol-gel transition of TEOS by hydrolysis reaction to a sintering step to form SiO₂. Initial hydrolysis parameters of TEOS had an influence on gel shape and transition properties as well as on the bulk density and surface area of the final sintered products of SiO₂. In acid catalyst system, with increasing hydrolysis reaction temperature, fiber drawing zone of sol-gel had become smaller. In closed system no fiber was obtained. Incease in H₂O concentration enhanced the initial hydrolysis reaction of TEOS. The hydrolysis reaction was faster in base catalyst system than in acid catalyst system. In acid catalyst, increasing the water concentration resulted in formation of a big primary particles in bulk SiO₂ gel. On the other hand, in base catalyst system increasing the water concentration didn’t form a bulk gel, which is due to the formation of segregated fine powders before the bulk gel transition.

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