Synthesis of engineered particulates with tailored properties using dry particle coating

Dry particle coating is used to create new-generation materials by combinin g different powders having different physical and chemical properties to fo rm composites, which show new functionality or improve the characteristics of known materials. Materials with relatively large particle size (1-200 mu m) form a core and these core (host) particles are mechanically coated with fine submicron (guest) particles; no liquid of any kind (solvents, binders or water) is required. A number of different devices used to achieve dry p article coating are reviewed. The fundamental mechanisms by which these dev ices achieve coating are discussed, and many examples of coated particles p roduced by these methods in our laboratory, as well as by other researchers , are described. Attempts to model some of these processes, so as to be abl e to predict suitable operating conditions and processing times for differe nt host and guest particle properties, are also described. A theoretical pr edictive capability is necessary, not only to determine which of the device s would give the best results in a specific application, but also for scale -up and optimization. Based on our research, we believe that dry coating is a viable alternative to wet coating and can be used successfully for certa in applications where wet coating processes are not feasible. (C) 2001 Else vier Science B.V. All rights reserved.