规则SiO_2颗粒的超临界合成

Synthesis of Regular Silica Particles in Supercritical Fluids

通过正硅酸乙酯 (TEOS)在超临界乙醇 -水 -氨介质中的反应 ,合成出具有规则形状和大小均匀的SiO2 颗粒 ,并通过透射电子显微镜 (TEM )和扫描电子显微镜 (SEM )对颗粒进行了表征。同时通过调节体系中乙醇 /水的摩尔比例 ,改变临界温度和压力 ,可以调变合成产品的颗粒大小。同时为避免TEOS在升温过程中与水发生反应 ,TEOS的加入通过液体高压进样泵来完成。另外 ,不同组成的混合介质的临界温度和压力通过跟踪具有相同配比不同总体积的体系的压力

The reaction of tetraethylorthosilicate (TEOS) was conducted in supercritical medium composed of ethanol,water and ammonium as catalyst.The addition of TEOS was carried out by using a high pressure pump to avoid the reactions towards water during the heating process.As a result,very regular and uniform silica particles were obtained after the reaction conducted in the supercritical medium for 24h.The particle size could be adjusted by changing the molar ratio of ethanol to water and consequently the critical temperature and pressure.The critical temperature and pressure of the mixed medium was determined from the separating point of the p-T curves that possessed different total volume but the same composition.