Disperse ultrafine amorphous SiO2 nanoparticles synthesized via precipitation and calcination

Disperse ultrafine spherical amorphous SiO2 nanoparticles with high purity are essential for producing SiO2 nanoglass which may show a good toughness. Herein, synthesis of disperse ultrafine spherical amorphous SiO2 nanoparticles with high purity via precipitation and calcination is reported. In the preparation, Na(2)SiO(3.)9H(2)O was used as silicon source, and NH4Cl as a buffer for a catalytic self-condensation of hydroxyl groups during hydrolysis of Na2SiO3 in the alcohol/water solvent system and a slowly hydrolyzed precipitator as well. The main factors affecting the size, dispersity, and shape of amorphous SiO2 nanoparticles including the amount of cetyltrimethyl ammonium bromide (CTAB), different surfactants (sodium dodecyl benzene sulfonate, CTAB, and polyethylene glycol), ethanol/water solvent volume ratio, and different solvent systems were investigated. Welldispersed spherical amorphous SiO2 nanoparticles with an average particle size of 4.0 nm and a size range of 2-12 nm were synthesized using 0.15 g/L CTAB and 1:1 volume ratio of methanol/water and by calcination. The specific surface area of the SiO2 nanoparticles with an average particle size of 4.0 nm is 584 m(2)/g. The SiO2 nanoparticles have a purity of 99.4% (mass percent). The disperse ultrafine spherical amorphous SiO2 nanoparticles have a high purity, the finest particle size, and the largest specific surface area achieved so far.