Papers by Author: Jae Heyg Shin

Abstract: The influence of the two deposition parameters on microstructure, and microhardness of plasma sprayed TiO2 coatings were investigated. It was found that a higher spraying power and a shorter distance resulted in a lower porosity and a higher microhardness for the coatings. The anisotropy on the microstructure and microhardness of TiO2 coatings was also found. The denser microstructure is attributed to the higher degree of melting and higher velocity of the TiO2 powders during spraying. The improvement of microhardness is associated with the lower porosity. The difference of porosity and microhardness between surface and cross section resulted from their different microstructures.

Abstract: Plasma spraying technique was used to deposit thin TiO2-based photocatalytic coatings on a foamed aluminum. Before spraying, the composites of nano-TiO2 powder (P25) and nano- ZnO/CeO2/SnO2 powders were agglomerated into microsized powders by a spray-drying process. XRD, SEM, TEM, XPS and the photocatalytic activity evaluation by the decomposition of benzene were applied to characterize the starting powders and the coatings, respectively. The results showed that all the three plasma sprayed TiO2-based coatings were the mixture phases of anatase and rutile. The XPS spectra results revealed that the oxygen element was composed of three kinds of chemical states, i.e., crystal lattice oxygen, hydroxyl oxygen and physical-adsorbed oxygen. The plasma sprayed 90%TiO2-10%CeO2 coating and 90%TiO2-10%SnO2 coating exhibited similar photocatalytic activity, which was higher than that of 90%TiO2-10%ZnO coating.