본 연구에서는 솔 침전공정에서 TEOS(Tetraethylorthosilicate) 반응물을 이용하여 실리카 분말 합성시에 TEOS 농도, 물농도, 반응물 주입속도, 교반속도 등의 반응조건이 실리카 과포화 농도 및 입자크기에 미치는 영향에 대해 연구하였다. TEOS 반응물과 물 농도가 증가할수록 입자유도시간은 짧아졌으며 입자유도시점에서의 과포화 농도는 감소하였다. 그러나, 반응물 주입속도가 입자유도시간과 입자유도시점에서의 과포화 농도에 미치는 영향은 서로 상반되었다. 즉, 반응물 주입속도의 증가에 따라 입자유도시간은 감소하였으나 입자유도시점에서의 과포화 농도는 증가하였다. 반응조건에 따라 서로 다른 과포화 농도에서 입자가 유도되는 것은 입자의 형성에 있어서 과포화도 이외의 용액의 조건에도 영향을 준다는 것을 의미하는 것이다. 한편, 교반속도는 입자유도시간과 유도시점에서의 과포화 농도는 거의 영향을 주지 않았다. 이것은 솔 침전공정에서 반응물 혼합시간이 충분히 짧아 실리카 생성에 있어서 반응속도가 입자유도 및 과포화 농도 결정에 가장 크게 영향을 미쳤기 때문이다. 반응조건에 따른 가수분해 및 축합 반응속도를 Kim 등[15]이 제시한 식을 이용하여 예측하였으며 이 결과는 본 실험에서 측정한 입자유도시간의 함수로도 매우 잘 묘사될 수 있었다. 또한, 반응조건에 따라 합성된 최종입자의 크기 변화도 입자유도시간의 함수로 훌륭히 묘사될 수 있음을 보여 주었다.

In a single feed semi batch reactor effects of reaction conditions, such as TEOS and water concentrations, reactant feed flow rate and agitation speed, on the silica supersaturation and particle size synthesized in sol precipitation were investigated. As the TEOS and water concentrations increased, the particle induction time and the supersaturation at the particle induction point were reduced. However, the dependencies of the particle induction time and supersaturation at the particle induction point on the reactant flow rate were opposite to each other. That was, the particle induction time decreased with increase in the reactant flow rate but the supersaturation at the particle induction point increased. The fact that the supersaturation level to induce the particle was varied with the reaction condition implied that the solution condition determined by the reaction condition as well as the supersaturation level was important to the particle induction. Meanwhile, the particle induction time and supersaturation at the particle induction point were little influenced by the agitation speed in the reactor. This result was due to the micromixing time being short enough in comparison to the reaction time of TEOS. Thus, the particle induction time and supersaturation at the particle induction point was predominantly determined by the reaction time rather than the micromixing time of TEOS. The reaction rate constants of TEOS hydroysis and condensation, which was predicted with Kim et al.'s equations[15] at the reaction conditions was described as a function of the particle induction time. In addition, the particle size synthesized at the reaction conditions was able to be well fitted as a function of the particle induction time.

Sol Precipitation Reaction Condition Particle Induction Time Hydrolysis/Condensation Supersaturation Particle Size

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