Particles with vapor deposition coating

Abstract

A new fluidized bed particle coating method is disclosed by the use of which coatings can be uniformly and conveniently deposited on the surfaces of fluidized particulate materials by vapor deposition processes at temperatures lower than those of the heated coating precursor transport lines. By this method, particle materials with relatively low surface temperatures may be brought into close proximity with a coating precursor containing gas stream characterized by a substantially higher gas volume temperature in such a way that the vaporized precursor molecules are caused to adsorb or condense on the relatively cold particle surfaces without also condensing on any other surface. Further, if the adsorbed precursor molecules are capable of reacting or polymerizing on the relatively cold particle surfaces, thus forming substantially continuous coatings on those surfaces, they may do so without also depositing such coatings on any other surfaces. Such coating deposition processes cannot be carried out using conventional fluidized bed deposition methods or equipment.