Functionalization of Ultrafine Particles by Atomic Layer Deposition (ALD)
Fine powders can be functionalized with nearly perfect pin-hole free and ultrathin films on primary particles, including nanoparticles, by Atomic Layer Deposition (ALD). Substrate powders include both inorganic and organic materials. Coatings are generally inorganic in composition. Of particular importance is the ability to functionalize particles less than 100 microns in diameter, including submicron and nanosized powders, and carbon nanotubes. Primary particles can be coated with ceramic films having a thickness in the range of 1 to 20 nm, controlled to within approximately 2 angstroms of the desired film thickness. A comparison will be presented between coating particles by Chemical Vapor Deposition (CVD) and by ALD, with a particular emphasis on the advantages/disadvantages of both. Examples will be provided for applications where coated particles have value in specific markets, including microelectronics, cosmetics, polymer/ceramic nanocomposites, defense, and others. The process is scalable and low cost with significant cost/performance advantages using fluidized bed reactors.