CHEMICAL VAPOR DEPOSITION OF PYROCARBON COATINGS ON POWDERS IN A FLUIDIZED BED. I. APPARATUS, FLUIDIZATION

Abstract

A laboratory setup for chemical vapor deposition (CVD) at reduced pressure on powder of medium particle size in a fluidized bed (reactor load of 50 g of substrate) was described. Calculations of critical points for the onset of fluidization and entrainment of particles for various gases (Ar, C3H8, C4H10) at a temperature of 20–1000 °C under low vacuum (pressure of 5 kPa) were performed. Model experiments were carried out on the fluidization of corundum powder (granularity of ~300 μm) in an argon flow, as well as in the propane-butane mixture in the absence of CVD. The dependences of the hydrodynamic mode of fluidization on the nature of fluidizing gas, temperature and pressure were analyzed, which make it possible to plan the process of coating deposition itself.