Surface coating of particles by nanospray process and CCVD in circulating fluidised bed

Coating of powders is often used to protect particles and to modify surface properties such as lustre, catalytic activity, hardness, permeability, adhesion and conductivity. A fast circulating fluidised bed for combustion chemical vapour deposition (CCVD) and CVD is introduced for the production of particles coated with nanolayers of metal oxides and metals. The CCVD fluidised bed process involves Nanomiser device atomisation and controlled thermal decomposition of low cost metalorganic liquid precursors and nanocoating of particles with thin films or with nanoparticulates while suspended in a turbulent fluidised bed. This paper describes the production of mica and glass spheres uniformly covered with metal oxide (TiO₂, Cr₂O₃) and metal (Ag) films. The coated powder morphology, surface composition and optical properties were characterised by electron and optical microscopy and elemental analysis.