Preparation of silica, titania and mixed silica/titania particles has
been studied. The region for formation of monodisperse SiO2 particles
in the phase diagram tetraethyl orthosilicate (TEOS)-ethanol-H2O was s
tudied as a function of NH3 concentration at room temperature. Titania
particles could be prepared at lowered temperatures and concentration
of ammonia up to 0.01 M. The size of SiO2 particles was 0.03-1 mu m w
hereas TiO2 particles were size range 0.5-0.8 mu m. Mixed SiO2/TiO2 pa
rticles were prepared from prehydrolyzed TEOS/EtOH solutions by adding
tetraethyl orthotitanate (TEOT). This was accomplished at 3 degrees C
and slightly alkaline solutions. The final particle size of the mixed
particles was about 0.3 mu m.