Highly crystalline, well-developed hydroxyapatite (HAp) crystals were grown successfully for the first time by a flux cooling method at a temperature less than 500 °C under air pressure. Environmentally friendly growth was induced by heating a mixture of solute [Ca(NO 3 ) 2 • 4H 2 O, (NH 4 ) 2 HPO 4 , and KOH] and flux (KNO 3 and LiNO 3 ) at 400-500 °C and holding at this temperature for 10 h. After that, the mixture was cooled at various rates of 5, 200, and >1000 °C • min -1 (water quenching). The obtained HAp crystals, which had average sizes of up to 18.0 × 2.1 µm and aspect ratios of up to 8.6, were colorless and transparent. They had hexagonal prismatic one-dimensional (1-D) forms with pyramidal or truncated pyramidal end faces. The 1-D crystal forms and sizes were obviously dependent on the growth conditions, such as the holding temperature and the cooling rate of the high-temperature solution. High-resolution transmission electron microscopy (HR-TEM) images indicated that the grown HAp crystals were of a very good crystallinity. From the HR-TEM and X-ray diffraction, the 1-D HAp crystals, which were hexagonal cylinders ({101 j 0} faces), elongated in the 〈0001〉 directions.
We examined the time-dependent changes in the optical properties of single-walled carbon nanotubes which were consecutively oxidized by irradiation with vacuum ultraviolet light. It is demonstrated that photochemical oxidation is a mild and controllable method for manipulating the surface of nanotubes in order to convert their affinity from hydrophobic to hydrophilic by controlling the density of functional groups on their sidewalls without destroying their tubular morphology.
Well-developed, highly crystalline Na 2 Ti 6 O 13 whiskers were successfully grown by cooling a NaCl flux at a relatively low temperature of 700°C. The obtained Na 2 Ti 6 O 13 whiskers were colorless and transparent. The whiskers grown at 700°C were single phase and exhibit the lowest sizes of up to about 3.5 µm ϫ 0.1 µm. From the results of SEM, XRD, and TEM, it was confirmed that the Na 2 Ti 6 O 13 whiskers have
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