Elaboration of the thermal sprayed reactive titania-based surfaces for the environmental applications

Filofteia-Laura Toma
LERMPS-UTBM (France)

Didier Klein
LERMPS-UTBM (France)

*Ghislaine Bertrand
LERMPS-UTBM (France)

Christian Coddet
LERMPS-UTBM (France)

*Cathy Meunier
FEMTO-CREST CNRS 6000 (France)

Hanlin Liao
LERMPS-UTBM (France)

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     Last modified: September 18, 2005

Abstract
Photocatalysis, that allows the decomposition of organic compounds and the removal of harmful gases is one of the most studies methods to solve the major problems of the environmental air and water pollution. Titanium dioxide (TiO2), the most important photocatalyst, can be used in form of slurry or immobilized in form of thin film or coating obtained by different methods of deposition. Thermal spraying is widely used to elaborate titania coatings for mechanical and biomedical applications due to their hardness, wear and corrosion resistance, biocompatibility. The studies performed in the last years showed that this technique could be employed to obtain TiO2 deposits with an effective activity for the decomposition of organic compounds.
In the present paper it was proposed a comparative study on the microstructure and photocatalytic performance of titania coatings elaborated by atmospheric plasma spraying (APS), suspension plasma spraying (SPP) and high-velocity oxygen fuel spraying (HVOF). Agglomerated spray-dried nano-structured anatase TiO2 and TiO2-Al powders were used as materials feedstock for spraying. Morphology and micro-structural characteristics of the coatings were studied by SEM, X-ray diffraction and thermal analysis. The photocatalytic behaviour of the TiO2-based surfaces was evaluated from the decomposition of nitrogen oxides (NOx), major air pollutants that participate to the greenhouse effect and cause very seriously problems on the human health.
Coatings microstructure and the photocatalytic performance were different, function of the thermal spraying technique. The photocatalytic responses of the films were principally correlated with their crystalline structure. The results showed that the anatase phase presented better efficiency and a highly amount of anatase was suitable for the pollutants degradation. Moreover, the presence of the co-sprayed aluminium particles enhanced the photocatalytic activity of the titania coatings for the degradation of environmental air pollutants, such the nitrogen oxides.