Highly crystalline and oriented Na 2 Ti 3 O 7 whiskers were successfully and directly grown on a metallic titanium mesh using a NaCl flux cooling method for application to semiconducting photocatalysis. Specifically, unique threedimensional photocatalytic materials were fabricated by converting a titanium mesh into a Na 2 Ti 3 O 7 tubular mesh consisting of highly oriented whiskers. The formation mechanism of the oriented Na 2 Ti 3 O 7 whiskers was investigated using field emission scanning electron microscopy, energy-dispersive X-ray spectrometry, and X-ray diffraction. From these results, the following conclusions could be confirmed. First, a titanium oxide layer was formed on the Ti wire surface by thermal oxidation. Since this oxide layer acts as a protective layer to thermal energy, the wire shape was maintained during Na 2 Ti 3 O 7 whisker growth. Next, highly oriented Na 2 Ti 3 O 7 whiskers were directly grown on the titanium oxide layer. During whisker growth, Ti was radially supplied from the bulk of the Ti mesh to the inner surface of the TiO 2 layer. Finally, the Ti wire structure transitioned into a tubular structure consisting of Na 2 Ti 3 O 7 whiskers. During the fabrication process, the Ti wire was dissolved by the NaCl flux, and the dissolved Ti ions reacted with O and Na ions to form TiO 2 and Na 2 Ti 3 O 7 layers. As a result, oriented and highly crystalline Na 2 Ti 3 O 7 whiskers were directly grown on the TiO 2 layer. The Ti wire was completely dissolved in this reaction system. Furthermore, the photocatalytic activities of the tubular mesh consisting of Na 2 Ti 3 O 7 whiskers were confirmed by the photocatalytic degradation of a fluoroalkylsilane self-assembled monolayer and trichloroethylene under ultraviolet light irradiation. The whisker mesh developed herein exhibited good photocatalytic properties under ultraviolet light irradiation.

Well-formed, highly crystalline potassium titanate whiskers were successfully grown by the KCl flux cooling method at a holding temperature of 800 uC using metallic titanium materials. Of primary importance were the metallic Ti spheres and potassium chloride powders that were used as the starting materials for growth of the titanate whiskers. Ultralong K 2 Ti 6 O 13 whiskers grew radially from the center of the Ti spheres by our flux technique. Cross-sectional SEM images demonstrate that the ultralong whiskers were grown on the TiO 2 crystal layer, and the whisker spheres had a bilayer structure that was hollow in the center. When Ti powders were used as the starting material, spherical aggregation of K 2 Ti 6 O 13 and K 2 Ti 4 O 9 whiskers occurred. The product structures were different from those obtained from metallic Ti spheres. Based on SEM, EDS and XRD, the formation mechanism of the ultralong whiskers was also discussed. Furthermore, the photocatalytic activity of the whiskers was confirmed by trichloroethylene degradation under ultraviolet light irradiation.