2001 Volume 34 Issue 10 Pages 1285-1292
This paper describes the investigation of the generation of spherical silica particles, which could potentially be used as alternative calibration aerosol for substituting DOP (dioctylphthalate) particles. Silica particles were generated by a spray drying method using a nanometer-sized colloidal silica suspension as the starting material. The generated silica particles have a spherical morphology, are nearly monodispersed and their size can be controlled at submicron order. The smoothness of the particle surface is greatly affected by the size of the colloidal silica particles used. Silica aerosol particles were also generated by the spray pyrolysis of an aqueous solution of tetraethylorthosilicate (TEOS), in order to compare their properties with those of silica particles obtained by spray drying method. The electrical mobility equivalent diameter of silica particles generated by spray drying method is in good agreement with the diameter determined by SEM observation. The light scattering characteristics of the silica aerosol particles were also measured using a laser particle counter and compared with a polystyrene latex (PSL) aerosol. By increasing the drying temperature of the silica sol droplets to 1200°C, the change of scattered light intensity with particle diameter shows a tendency similar to that of spherical PSL particles. Consequently, the spherical submicron silica particles generated by the present spray drying method appear to be applicable to the test of air filters.