Self-induced Preparation And Properties Of Ti₃O₅Nanowires

Ti3O5, as a kind of environment friendly materials, is known for its numerousproperties such as phase transition reversibility, photocatalysis, oxygen-sensitivity,good resistance-temperature stability, non-toxic and innocuity. As thenanotechnology advances rapidly, increasing attention has been paid on Ti3O5, due toits excellent optical storage capacity and photocatalytic activity. The thesis focusedon the preparation technology and photocatalytic activity of self-induced Ti3O5nanowires by APCVD. The influences of the experiment parameters on Ti3O5nanowires and photocatalytic activity, including deposition temperature, reaction timeand the flux of O2were respectively investigated. Meanwhile, whether the nanowireswould grow or not during the temperature-fall period were specifically discussed.Accordingly, the influence regularity of preparation process on properties of Ti3O5nanowires deposited by APCVD was obtained. It was concluded that:The monoclinic system Ti3O5nanowires were synthesized successfully on Ti5Si3powder by self-induced APCVD. Masses of smooth and upright nanowires withlengths of about500nm and diameters of20-40nm were obtained in the O2flux of20sccm at800℃for90min. The growth mechanism of the self-induced process wasanalysised. The vacancies, left by the nucleation of Ti-O on the surface of Ti5Si3,induced the generation of Ti3O5cystal. Then the Ti3O5nanowires grew downwardfrom top with the constant supplement of O2. Combing with the thermodynamicanalysis, the reaction was feasible owing to the small Gibbs free energy.The reaction temperature, reaction time and the flux of O2could directly affect thegrowth of Ti3O5nanowires. As the deposition temperature gradually increased, Ti3O5crystalline phase grew rapidly while nucleation rate increased at first and thendecreased. The optimum temperature for the growth of Ti3O5nanowires was800oC.On the contrary, the growth of Ti3O5nanowires could not be promoted for inadequatesupply of Ti with excessive time.90min was the optimal time. Meanwhile, it was alsoimportant to take the flux of O2into consideration. The reaction was easily limitedunder small flux, on the contrary, too large flux made the anisotropy of nanowires shrink and the nanowires cluster, which were difficult to be recognized. The properflux of O2would be20sccm.Through setting the re-constant temperature segment in the temperature-fallperiod, the growth of Ti3O5nanowires was observed. However, the inappropriatetemperature and inadequate reactants resulted in the slow growth rate. It wasobserved that the new nanowires were longer while thinner with diameters of about15-20nm, making the morphology features with thick top and thin bottom appeared.Not only did the small diameter and large specific surface of Ti3O5nanowiresmake the probability of electron-hole recombination reduce, but made it easy to beadsorbed by degraded substances, further improving the photocatalytic activity ofTi3O5. Ti3O5nanowires synthesized under the optimum factors performed wellphotocatalysis. It was studied that62%of methylene blue was degraded by Ti3O5nanowires for180min degradation.