Preparation of Ultraviolet Shielding Composite Fine Particles by the Spray Dry Method and Their Optical Properties

Abstract

We have proposed composite fine particles, i.e. composite powders of ultra-fine particles, to show the optical function of ultra-fine particles by preventing them from aggregating. They have the structure where optically functional ultra-fine particles are dispersed and fixed in transparent inorganic fine particles. For instanse, spherical TiO ₂/SiO₂ composite fine particles with diameters from 0.48 to 0.59 im were prepared by the spray dry method from an aqueous solution of SiO₂sol and TiO₂ sol under various experimental conditions. It was confirmed by an electron microscope that the microstructure of prepared particles was composed of SiO₂ fine particles with TiO₂ ultra-fine particles being dispersed and fixed in them. Moreover, it was found that the particle diameter was increased at higher concentration of nebulized solution, and it was primarily concerned with the droplet diameter. The prepared particles showed the optical properties of TiO₂ ultra-fine particles which had a high transparency in the visible range and a high shielding ability in the ultraviolet range. Accordingly, it is expected that prepared composite fine particles are applicable to cosmetics, paints, and other products as ultraviolet shielding agents with a high transparency.