Preparation Of SiO₂ Microparticles By Ress Technology

This work is to prepare SiO₂ microparticles by RESS (the Rapid Expasion of Supercritical Solution) technology.The solubility of SiO₂ in supercritical CO₂ was first measured within a large range of pressure and temperature. The effects of temperature and pressure on the SiO₂ solubility in supercritical CO₂ were investigated. It was found that SiO₂ has poor solubility in the SCF-CO₂ and its solubility increases with the increasing of pressure and temperature in certain range. The retrograde area as reported in some literatures was found when pressure was low enough.Secondly, SiO₂ solubility in supercritical CO₂ were correlated by Chrastil models and P-R equation model respectivly. P-R equation model can correlate the experiment data better with reasonable greetment.In the RESS experiment, particles prepared are generally smaller, more uniform and better morphlology than the starting material. It was found that the temperature and pressure in the precipitator have no obvious effect on the size of the particles. The size of the particle prepared by RESS is almost in the range of 430⁵20nm. In addition, the particle size distribution of the particles was measured, and the results indicate that the particles are uniform. In the experiments, threadlike particles were obtained when the pressure was high enough, it's slenderness ratio reaches 3¹5.