Process Of Optimization And Properties Study Of Nanotubes Using TiO₂ Powder

This paper researches on the technology of preparing titanium nanotubes with the commercial rutile TiO₂ nano-powder as raw materials.The method is Hydrothermal Synthesis, and the process is optimized. With SEM, XRD, TEM and Sensitivity test system, it discussed that different reaction temperature, reaction time and alkali concentration effected on phase , size and morphology of titanium nanotubes, and also discussed the acid stability, heat stability and the gas sensitivity of the product under the optimum reaction parameters.The commercial rutile TiO₂ nano-powder reacted with NaOH solution. The optimum reaction parameters are 210℃, 24 hours and 10mol/L NaOH solution. The length of water-washing product is from 2μm to 8μm, and its diameter is between 30 nm to 70nm, it has multilayer wall, different bundles interlace and the distribution of bundles is disordered. The diameter of single-layer nanotube is from 7nm to 13nμm, and its length is between 70 nm to 110nm, but multilayer nanotube has 2 to 5 layers , its inner-diameter is from 5 nm to 50nm , its outer-diameter is from 13nm to 63nm, and multilayer nanotube shows non-uniform symmetry. The phase of water-washing product is Na₂Ti₃O₇; The length of acid-washing product is shorter than water-washing product's, but the diameter of both product is similar. The phase of acid-washing product is Ha₂Ti₃O₇. With the reaction temperature rising, the length-diameter ratio of titanium nanotube increases, the morphology is clear and obvious. In order to get the ideal morphology of nanotubes, the reaction time and reaction alkali concentration must be in certain scope. Too high or low reaction time and reaction alkali concentration cannot get clear and obvious nanotubes.There are acid stability test and thermal stability test included in stability test.In the acid stability test, with the increasing of acid concentration, the length of titanium nanotubes gets shorter and its dispersivity is reduced, but the phase is still H₂Ti₃O₇ which has no change. Compared with unprocessed product, there is almost no change with the length and diameter of titanium nanotubes after heat treatment, just reduction of dispersion between vascular bundle. So, it is dispersion between vascular bundle that declined as heat treatment temperature rised. The phases are mainly Na₈Ti₅O₁₄ and brookite TiO₂ when heat treatment temperature rises to 400℃and 500℃, and when the temperature rise to 600℃, the phases are mainly Na₈Ti₅O₁₄, a little brookite TiO₂ and anatase TiO₂.Rresistance semiconductor gas sensors were made by water-washing product and acid-washing product and measured ethanol with a concentration of 250ppm at room temperature. The response time of gas semsors made of both products are 21s and 48s respectively,recovery time are 21s and 15s, and sensitivity respectively are 27% and 16%.