Synthesis of engineered particulates with tailored properties using dry particle coating

Dry particle coating is used to create new-generation materials by combining different powders having different physical and chemical properties to form composites, which show new functionality or improve the characteristics of known materials. Materials with relatively large particle size (1-200 mum) 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 particle coating are reviewed. The fundamental mechanisms by which these devices achieve coating are discussed, and many examples of coated particles produced 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 able to predict suitable operating conditions and processing times for different host and guest particle properties, are also described. A theoretical predictive capability is necessary, not only to determine which of the devices 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 certain applications where wet coating processes are not feasible. (C) 2001 Elsevier Science B.V. All rights reserved.