Synthesis And Morphology Control Of Tio₂ Nanocrystals By Hydrothermal Method

In this paper, we adopt hydrothermal method at 180℃for 24h, and the fill factor was 68%. With the sodium titanate nanotubes prepared by hydrothermal method as the precursor, rutile and anatase TiO2 nanocrystals with smaller particle size were synthesized on the strong acid condition; long lamina anatase TiO2 nanocrystals were synthesized on the neutral and alkalescent condition, and their maximum length and width were 2.5μm and 250nm respectively; little long lamina anatase TiO2 nanocrystals were synthesized on the strong alkaline.condition, but there were more sodium titanate nanotubes that did not react.Using the sodium titanate nanotubes marinated by hydrochloric acid solution as the precursor, club-shaped and long flakiness anatase TiO2 nanocrystals were synthesized on the neutral and alkalescent conditions respectively, and their lengths were about 50-100nm and 60-110nm respectively; lamina anatase TiO2 nanocrystals were synthesized on the super alkaline condition, and their lengths were about 300-500nm. It's indicated that the corrosion rate of sodium titanate and H-titanate nanotubes is related with the solution pH, the lower the pH is, the faster the corrosion rate is, and the smaller the crystal granule is. And contrarily, with the corrosion rate becoming slower, the crystal size becomes larger.With the sodium titanate nanofibers prepared by hydrothermal method as the precursor, rutile and anatase mixed TiO2 nanocrystals were synthesized on the strong acid condition; the anatase TiO2 nanofibers with character of self-organizing were synthesized on the weak acid condition; on the strong alkali condition, the crystal phase was not changed, and it was still sodium titanate fiber.With the sodium titanate nanofibers marinated by hydrochloric acid solution as the precursor, the anatase TiO2 nanofibers with character of self-organizing were synthesized. It's indicated that the corrosion rate of sodium titanate and H-titanate nanofibers is related with the solution pH, when the pH is low (strong acid), the corrosion rate of fibers is faster, only nanogranules were synthesized. On reasonable condition of the pH, the crystallization rate of anatase TiO2 was faster than the corrosion rate of fibers, which made anatase TiO2 adhering to the surface of fibers, crystallization, becoming nanocrystal's aggregation with character of directional grown trend, and keeping the shape of fiber. Then the quasi-crystal nanofibers can be acquired.With TiCl4 as the precursor, column rutile TiO2 nanocrystals were synthesized on strong acid condition, and their lengths were about 50-200nm. On the same condition, when FeCl3·6H2O and NiCl2·H2O were put in the solution of TiCl4 respectively, ribbon rutile TiO2 nanocrystals were all synthesized, and their lengths were about 1-3μm. It's indicated that the interface effect of{101} facets, which were made by Fe3+ and Ni2+ in the solution, restrained the growth rate of{110} facets, and induced the growth of TiO2 nanocrystals along [001] which is one dimension direction.