Fluidized bed chemical vapor deposition of pyrocarbon on various types of powders: Heat and mass transfer analyses and nanotexture characterization

[Display omitted] •A Fluidized Bed CVD experiment has been set up, tested and validated.•The optimization of heat transfer is an essential feature for the reactor control.•Pyrocarbon was deposited successfully on very fine and porous powders.•Heat and mass transfer computations are in good agreement with experimental data.•The nanotexture of the deposited pyrocarbon is shown to be dependent on pore size. SiC powders coated by pyrocarbon are a promising feedstock for the synthesis of Ceramic-matrix composites. Preparing such powders is possible using low pressure Fluidized-Bed Chemical Vapor Deposition (FB-CVD) with propane as a precursor at 1000 °C. A preliminary study on non-porous and porous alumina powders as substrates has been carried out. With the help of a numerical assessment of heat transfer in the reactor, it has been possible to optimize the setup and achieve excellent deposition yields (up to 100%), even inside very small pores (7 nm), and transpose the protocol to 200-nm diameter SiC powders. The microstructure and texture of the deposits were characterized by TEM, showing dependence to pore size due to a texture-induction effect by the substrate surface. A quantitative assessment of mass transfer indicated that the results obtained here agree with past studies on FB-CVD of other materials and on pyrocarbon CVD on flat substrates.