Alumina coatings on silica powders by Fluidized Bed Chemical Vapor Deposition from aluminium acetylacetonate
Résumé
A SiO2 powder has been coated by alumina using the Fluidized Bed Chemical Vapor Deposition process
and a metal organic precursor, aluminium acetylacetonate (Al(acac)3 or C15H21AlO6) as single source. A
range of low temperatures, i.e. 400–620 C has been explored at atmospheric pressure. Systematic characterizations
were performed by Field Emission Gun Scanning Electron Microscopy (FEG-SEM) coupled
with Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infra-Red (FT-IR) spectroscopy
and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The process involves a first
step of gas phase reactions producing reactive intermediates, themselves leading to Al2O3 and carbon
containing deposits. Between 400 and 500 C, the deposits are lamellar and constituted of mixtures of
Al2O3, non-decomposed Al(acac)3 and impurities, leading to a C/Al molar ratio close to 2. For this range
of temperature, the precursor is not totally decomposed and the limiting parameter of the process is the
deposition temperature. For 600 and 620 C, the deposits are nodular and mainly formed of Al2O3 and
acetylacetone C5H8O2, one of the main intermediate species formed in the gas phase. The Al(acac)3
decomposition seems to be complete, but a deposition temperature of 620 C is not high enough to allow
a complete decomposition of carbon ligands of the chemisorbing intermediate species. For these conditions,
the C/Al molar ratio increases with the deposition temperature, to reach values between 4 and 6, in
agreement with the observed darker colors of the deposits.
Domaines
Génie chimique
Origine : Fichiers produits par l'(les) auteur(s)
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