Fabrication and characterization of SiO2 particles generated by spray method for standards aerosol

This paper describes the investigation of the generation of spherical silic a particles, which could potentially be used as alternative calibration aer osol for substituting DOP (dioctylphthalate) particles. Silica particles we re generated by a spray drying method using a nanometer-sized colloidal sil ica suspension as the starting material. The generated silica particles hav e a spherical morphology, are nearly monodispersed and their size can be co ntrolled at submicron order. The smoothness of the particle surface is grea tly affected by the size of the colloidal silica particles used. Silica aer osol particles were also generated by the spray pyrolysis of an aqueous sol ution of tetraethylorthosilicate (TEOS), in order to compare their properti es with those of silica particles obtained by spray drying method. The elec trical mobility equivalent diameter of silica particles generated by spray drying method is in good agreement with the diameter determined by SEM obse rvation. The light scattering characteristics of the silica aerosol particl es were also measured using a laser particle counter and compared with a po lystyrene latex (PSL) aerosol. By increasing the drying temperature of the silica sol droplets to 1200 degreesC, the change of scattered light intensi ty with particle diameter shows a tendency similar to that of spherical PSL particles. Consequently, the spherical submicron silica particles generate d by the present spray drying method appear to be applicable to the test of air filters.