Atmospheric plasma sprayed (APS) coatings of Al2O3–TiO2 system for photocatalytic application

Abstract

The goal of this study is to examine the photocatalytic ability of coatings produced by atmospheric plasma spraying (APS). The plasma gun used is a common gas-stabilized plasma gun (GSP) working with a d.c. current and a mixture of argon and hydrogen as plasma-forming gas. The TiO₂ powders are particles of about 100 nm which were agglomerated to a mean size of about 55 μm, suitable for spraying. Composition of the commercial powder is 13 wt% of TiO₂ in Al₂O₃, whereas also in-house prepared powder with the same nominal composition but with agglomerated TiO₂ and conventional fused and crushed Al₂O₃ was sprayed. The feedstock materials used for this purpose are α-alumina and anatase titanium dioxide. The coatings are analyzed by scanning electron microscopy (SEM), energy dispersion probe (EDS) and X-ray diffraction. Photocatalytic degradation of acetone is quantified for various coatings. All plasma sprayed coatings show a lamellar structure on cross section, as typical for this process. Anatase titania from feedstock powder is converted into rutile titania and α-alumina partly to γ-alumina. Coatings are proven to catalyse the acetone decomposition when irradiated by UV rays.