Microstructure and Antibacterial of Thermal-sprayed Photocatalytic Coating Using Agglomerated Oyster Shell Powder from Disposed Oyster Shell and Photocatalytic Powders

Abstract

Agglomerated anatase TiO₂-oyster shell powders were sprayed by high-velocity oxy-fuel (HVOF) spraying on an A5052 (Al-Mg alloy) substrate. The powders were prepared by the spray dry method with various mixing ratios of 20%, 40%, and 60%. The primary particle size of TiO₂ was 7 nm, 30 nm and 200 nm. Phase transformation from anatase to rutile occurred during the HVOF spraying process. A higher anatase ratio could be obtained for the 200 nm-agglomerated powder. Therefore, the TiO₂ powder was used for the agglomerated TiO₂-oyster shell powder with mean diameters varying from 30 to 35μm.Sprayed coatings consisted of anatase-TiO₂, rutile-TiO₂, CaCO₃, and CaTiO₃. In gas examination of decomposition, the decomposition rate decreased by the addition of oyster powder. Conversely, the coating exhibits high antibacterial activity. Especially, the 60% TiO₂-oyster shell powder exhibited high antibacterial activity without black light irradiation.