Fluidization and coating of very dense powders by Fluidized Bed CVD
Résumé
The feasibility of fluidizing very dense powders has been studied in a collaborative work between the French Alternative Energies and Atomic Energy Commission and the Laboratoire de Génie Chimique from INP Toulouse. For this work, a commercial tungsten powder, 75 μm in mean volume diameter and 19,300 kg/m3 in grain density, was used.
First, the fluidization of the tungsten powder has been attempted at room temperature using nitrogen or argon as carrier gas. Then, the fluidization was studied at 400 °C in order to investigate the subsequent coating of tungsten powder by Fluidized Bed Chemical Vapour Deposition (FBCVD). In particular, the influence of the H0/D ratio (initial fixed bed height to reactor diameter) on the bed thermal behaviour was analysed. Finally, the first results concerning the coating of tungsten powder by alumina FBCVD from aluminium acetylacetonate are detailed. These latter tend to show that FBCVD is a suitable process to uniformly coat so dense particles.