Mono-disperse spherical silicon dioxide was synthesized in 2-propanol-H2O-NH3 system by the ultrasonic hydrothermal method.The catalyst ammonia acted as strong nucleophilic reagent.With orthogonal experiments

the effects of ultrasonic power

reaction temperature

stirring intensity and molar ratio on the size of silicon dioxide were studied.The results indicated that the diameter of silicon dioxide increased greatly with increasing ultrasonic power and molar ratio.The size of silicon dioxide also increased with increasing temperature and stirring intensity

but with a less extent.The process of forming mono-disperse spherical silicon dioxide could be divided into two steps: hydrolysis and condensation

with hydrolysis as the key step.Mono-disperse spherical silicon dioxide was characterized with XRD

TEM

DTA and IR

and the results showed that the sample was noncrystalline with regular shape and uniform granularity and there was a large amount of hydroxyl group in the SiO2 sample.