Preparation of ultrafine multicomponent particles by filter expansion aerosol generator

Abstract

A high-volume spray aerosol generator producing small droplets for low pressure applications, named as filter expansion aerosol generator(FEAG), was developed and characterized. The FEAG was composed of pneumatic nozzle for dispersing liquid, porous glass filter and vacuum pump. The mean size of the droplet was estimated to be 2.1 ㎛ with a geometric standard deviation 1.76. This generator in principle can be scaled up by increasing vacuum pump capacity and filter area. The potential applications of this spray generator will be film deposition, aerosol etching, and ultrafine particle preparation by spray pyrolysis at reduced pressure. Crystalline zinc oxide particles of nanometer size(< 12 nm) particles were produced from a zinc acetate solution by using filter expansion aerosol generator. Shape of particles produced by the FEAG were distinctively different from the one produced by the ultrasonic spray source. The nanometer particles were formed by uniform precipitation at the drying stage and decomposition followed by disintegration into nanometer particles. The photodegradation of trichloroethylene was carried out to investigate the photocatalytic activity of nanometer size ZnO particles prepared by FEAG. The photocatalytic activity of nanometer size particles was much greater than that of submicrometer size ZnO particles. Although the submicrometer size ZnO particles have lower photoactivity than that of the commercial $TiO_2$ particles, the photoactivity of nanometer size ZnO particles for the decompositon of TCE was greater than that of $TiO_2$ particles. The activity of submicrometer size ZnO particles based on the BET surface area had similar value to that of the commercial $TiO_2$ particles. But, the nanometer size ZnO particle showed greater initial rate than that of $TiO_2$ particles. Various types of multicomponent ceramic particles such as cathode materials and phosphor materials were prepared by the FEAG process and ultrasonic spray pyrolysis....