Plasma Sprayed Tio/Na-Titanate Composite Coating for Photocatalytic Degradation of Methylene Blue

Abstract

Photocatalytic degradation of methylene blue (MB) in aqueous solution using plasma sprayed TiO2 coating has to be improved. Hydrothermally prepared Na-titanate which has wire-like structure was spray dried into granules and mixed with nanostructured TiO2 granules the ratio of 50(TiO2):50(Na-titanate) wt% to form the composite feedstock powder for plasma spraying. The prepared composite feedstock TiO2/Na-titanate was deposited on the metal substrate using one of the thermal sprays coating method which is plasma spray. In this coating technique, the feedstock material in the form of powder is injected into the plasma stream where the particles are heated and accelerated at high velocity towards the substrate. The particles are impacted, splatted and rapidly cooled on the substrate and formed the coating. The microstructure of the coatings was observed by field emission scanning electron microscope (FESEM) and it showed that the coating was composed of melted and partially melted particles. The phase composition of the coatings was analysed by X-ray diffraction (XRD) and the result showed the presence of rutile and small amount of anatase phase. The photocatalytic activity of the coatings was determined by measuring the degradation of methylene blue (MB) dye in an aqueous solution under UV-irradiation. The MB degradation of the prepared composite coating was 67.3% after 8h UVirradiation.