Conformal multilayer coatings on fine silica microspheres by atmospheric pressure fluidized bed chemical vapor deposition

Conference Dates

May 22-27, 2016


Surface properties of fine particles can be tuned through deposition of films or coatings. This approach is an area of science and technology of interest in numerous fields such as catalysis, energy production, microelectronics, optoelectronics, etc. Surface coating of powders can be applied by a dry technique (i.e., the use of a reactive gas phase), so-called chemical vapor deposition (CVD). However, conventional CVD processes cannot provide an efficient conformal deposition while fine particles are considered as substrates. This is due to the fact that mixing of particles, in such a way that their entire surface is exposed to the reactive gas phase, is rather complicated and not often addressed. Therefore, fluidization, as a recognized particle treatment process which meets the requirement of gas–solid contact, can be associated with the gas–solid reactions that are often used in the context of various CVD processes. The combination of such mature techniques, namely fluidized bed chemical vapor deposition (FBCVD) leads to innovative, flexible and cost-effective particle treatment processes [1].

In the present investigation, soda lime spherical particles with a particle size of ca. 27 µm were used as the substrate. Single- and multi-layer depositions composed of TiO2 and SiO2 films were applied to the surface of the particles by the FBCVD at atmospheric pressure, while employing, respectively, titanium and silicon tetrachloride as precursors, and using water as an oxidation agent. TiO2 and SiO2 films were deposited at 300oC and ambient temperatures, respectively.

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