Fluidization, spouting, and metal-organic CVD of platinum group metals on powders

In the first part of this paper, processes used for the fluidization of particles in a CVD reactor are reviewed, then the concept of the spouted bed is introduced, and the possibility of using it in association with metal-organic (MO)CVD is discussed. In the second part, the particulars of the MOCVD of platinum group metals are recalled. Finally, the MOCVD of these metals in fluidized bed and spouted bed reactors is illustrated with results obtained during two research projects, one of which concerns the preparation of finely dispersed rhodium, platinum, and palladium-based catalysts by fluidized bed MOCVD, the other, the doping of NiCrAlY powders (a raw material for thermal barriers) with ruthenium by spouted bed MOCVD. Results on the morphology and purity of the deposits are presented, and the applicability of such techniques, either for industrial uses or for initial screening of dopants (nature and level), are discussed.