본 연구에서는 TEOS(Tetraethylorthosilicate) 반응물을 이용하여 SiO₂ 분말합성시에 SiO₂ 과포화 농도 변화에 따른 분말입자의 생성 및 성장에 대한 연구를 수행하였다. 반회분식 반응기에서 일정한 속도로 반응물을 암모니아 용액에 주입할 때 가수분해/축합반응에 의해 나타나는 silane의 농도변화 및 입자유도시간 측정을 통해 용액내의 SiO₂의 과포화 농도를 계산하였다. 용액내에서 SiO₂의 과포화 농도에 대한 분말 입자의 생성 및 성장 속도의 의존도를 측정하기 위하여 암모니아 촉매의 농도를 변화시켜 주었다. 암모니아 농도변화에 따라 가수분해/축합반응속도가 변하였으며 그로 인해 SiO₂ 과포화 농도의 변화를 얻을 수 있었다. 암모니아 농도의 증가에 따라 TEOS의 가수분해/축합반응속도는 증가하였으며 짧은 주입시간과 낮은 과포화농도에서 입자유도가 됨을 알 수 있었다. 따라서 암모니아 농도의 증가에 따라 최종적으로 얻어지는 분말 입자의 갯수밀도는 감소하고 평균크기는 증가하였다. TEOS 반응속도에 따른 SiO₂ 과포화농도 및 입도유도시간의 변화를 통해 입자의 생성속도와 성장속도를 예측하고자 모델식을 제시하였다. 실험결과와 모델식의 비교로부터 입자생성속도의 지수상수가 -634.02임을 알 수 있었다. 이것은 입자유도시간의 감소에 따라 입자생성속도가 감소하는 것을 나타내는 것으로서 동일한 과포화 농도에서 입자가 유도되는 것이 아님을 의미하는 것이다. 또한 모델식을 통해 최종 얻어지는 입자의 평균크기를 예측하였으며 이것은 실험결과와 잘 일치하는 것으로 나타났다.

Nucleation and growth of SiO₂ particle in the SiO₂ supersaturation solution, which was synthesized with TEOS by sol-gel method, were investigated. When the TEOS solution was fed into the semi-batch reactor containing the ammonia solution at constant flow rate, the concentration of silane produced by hydrolysis and condensation of TEOS and particle induction time were measured and then the supersaturation of SiO₂ in the solution was estimated. For investigation of dependency of nucleation and growth rates of SiO₂ particle on the supersaturation in the solution the concentration of the ammonia catalyst was varied. The reaction rates or hydrolysis and condensation of the TEOS was changed with the ammonia concentration and it resulted in variation of the supersaturation of SiO₂ in the solution. The induction time and supersaturation was reduced with increase of the ammonia concentration due to facilitation of the hydrolysis and condensation reaction. Thus, the lower population density and larger size of final particles were obtained with the higher ammonia concentration. To predict the particle nucleation and growth rates from measurable variables of SiO₂ supersaturation and particle induction time with change of TEOS reaction condition the model equations were suggested. From the comparison between experimental data and model prediction the exponential constant for particle nucleation rate was suggested as -634.02. This result meant that the particle nucleation rate was reduced with decrease of the induction time and the particles were induced at different supersaturation. In addition, the model prediction for the final mean particle size was well agreed with experimental data.

Sol-Gel Method Induction Time Particle Nucleation Particle Growth Hydrolysis Condensation Supersaturation

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