New Challenge of Plasma Spray Coatings in Nano Oxide Ceramics
Nanostructured and conventional Al2O3, ZrO2, and TiO2 were deposited using an atmospheric plasma spraying (APS). The size of commercial nano-ceramic powders was varied from 5nm up to 150nm. The microstructure and phase composition of the plasma sprayed coatings on metallic substrate were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that nano-sized ceramic powders enhanced the deposition efficiency on the metallic substrate rather than the micro-sized conventional commercial powders. Density and mechanical property such as microhardness were better in the case of the nano-sized ceramic powders than that of the conventional micro-sized ceramic powders, which are associated with the fine surface roughness and less size in pores of the coating layers. The wear rate of the nanostructured coating was lower than that of the conventional coating. The results were explained in terms of their microstructure of the coatings layers. Also, photocatalytic characterization of the plasma sprayed coatings, using nanocrystalline size TiO2 as feedstock with various powder sizes and shapes as well as adding with different photocatalytic oxides, was performed. The photocatalytic reactivity using plasma sprayed coating layers can be utilized into various applications.
T. Ohji, T. Sekino and K. Niihara
S. W. Lee, H. Chen, Y. Zeng, C. X. Ding, "New Challenge of Plasma Spray Coatings in Nano Oxide Ceramics", Key Engineering Materials, Vols. 317-318, pp. 533-538, 2006