Papers by Author: Hiroshi Asanuma

Abstract: Photocatalyst coatings on alumina (Al₂O₃) balls had been successfully fabricated by mechanical coating technique, with titanium carbide (TiC) powder and subsequent heat treatment in carbon powder. The effect of heat treatment conditions in carbon powder on the formed compounds, surface morphology and photocatalytic activity of photocatalyst coatings was investigated. XRD results show that the formed compounds change with increasing the heat treatment temperature in carbon powder, and rutile TiO₂ on the surface of TiC coatings at 1073 K and 1173 K. The generated oxygen vacancies confirmed by XPS measurement, are in favor of narrowing band gap to enhance the visible-light photocatalytic activity of photocatalyst coatings. The photocatalytic activity of photocatalyst coatings has been effectively enhanced, and the samples fabricated at 1073 K and 1173 K for 2 h show higher activity. The fabrication strategy provides us a facile preparation procedure of visible-light responsive photocatalyst coatings.

Abstract: The photocatalyst coatings on alumina (Al₂O₃) balls had been prepared by mechanical coating technique (MCT) and subsequent oxidation process with Ti powder and Cr powder, and the influence of oxidation temperature on the photocatalyst composite coatings (Cr-TiO₂) were investigated. The contrast experiments of the oxidation temperature and the usage of Cr powder had been carried out. The crystal structure and microstructure of the coatings were investigated. Photocatalytic activity of the coatings was evaluated and discussed. The XRD results showed that the mixed-phase of anatase (A) and rutile (R), and mass fraction of rutile (X_R) had been increased with adding Cr, especially under 973 K. The SEM images indicated that the needle-like oxide was formed at the temperature of 973 K. The photocatalytic activity is relatively higher at 973 K under both of ultraviolet (UV) and visible light (VL). At the same time, the influence on photocatalytic activity of the photocatalyst coatings under UV or VL by adding Cr would guide the direction for the improvement of photocatalytic activity.

Abstract: Ti coatings on alumina (Al₂O₃) balls had been prepared by mechanical coating technique (MCT), and the influence of the rotation speed on the coating formation process were investigated. The crystal structure and microstructure of the Ti coatings were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The formation process of Ti coatings was examined and discussed. The results showed that the rotation speed had great influence on the coating formation process. With increasing the rotation speed, the speed of coating formation had been accelerated and the surface became to be uneven. It was considered that the formation of metal coatings consists of 4 stages: nucleation, formation and coalescence of the discrete islands, formation of the continuous coating, and exfoliation.

Abstract: The influence of intermittent air introduction on the formation of Zn films during mechanical coating process was investigated. A series of contrast experiments were carried out. The XRD and EDS results showed that Zn particles were slightly oxidized. The SEM images indicated that disk-like zinc oxide (ZnO) nanocrystals were formed. The formation of disk-like ZnO made the morphology of Zn films more uneven and irregular. On the other hand, it increased the adhesion strength of Zn films to Al₂O3 balls and hence the exfoliation of Zn films was not found.

Abstract: A new designing concept to realize multifunctional structural material systems is proposed and demonstrated in this paper. The concept can be explained as follow: There exist a couple of competitive structural materials which normally compete with each other because of their similar and high mechanical properties, and they tend to have secondary properties which are different from each other or opposite among them. So if they are combined together to make a composite, the similar properties, normally high mechanical property, can be maintained, and the other dissimilar properties conflict with each other, which will generate functional properties. According to the proposed concept, a CFRP (carbon fiber reinforced plastics)/aluminum laminate was fabricated and its actuation capabilities and multifunctionality were successfully demonstrated. A titanium fiber/aluminum matrix composite was also fabricated, where the fiber was oxidized for electrical insulation and strengthening. This material system is very simple, but it can generate many useful functions such as heating, actuation, temperature sensing, deformation sensing and healing.