Dependence of Variation in Generated Silica Particle Properties on the Reactor Structure and Carrier Gas Type

抄録

The silicon production process without the use of chlorine has been investigated and can be simply described as follows:

MG-Si → SiH(OCH₃)₃ → SiH₄ → Poly-Si

However, in this process, a large amount of Si(OCH₃)₄ was produced. To overcome this problem, SiO (CH₃)₄ was used to produce pure silica.
It was demonstrated that the manufacture of fine silica is possible by the mixing of H₂O and Si(OCH₃)₄ in vapor phase with carrier gas. In addition to the temperature and reaction kinetic, the shape and size of the generated silica particles seemed to be affected by the carrier gas type and reactor structure. In this study, three different carrier gases and four reactor structures were tested. In fact, the fine SiO₂ particles were produced by the rapid heating and reaction of tetramethoxysilane (TEMS) with heated steam. The particle diameter became smaller in the order of Ar > N₂ > CO₂ due to the increased heat capacity. The higher the heat capacity of carrier gas, the faster is the heating of TEMS and is the formation of the nuclei. The same effect was also expected by the reduced flow rate of pure TEMS with larger flow rate of steam. Feeding the water from the lower part of the reactor avoided the instantaneous thermal decomposition of TEMS and accelerated its hydrolysis. The generated particle diameter was also demonstrated to be affected by the reactor type. By suppressing the back mixing, the standard deviation of the produced fine SiO₂ was reduced.