Research On Properties Of Titanium Dioxide Nanopowders Doped With Metal Ion Prepared By Plasma Spray

Pure TiO₂ has the disadvantages that photogenerated electrons and holes recombine easily, photocatalysis efficiency is low, its bandgap is wide, and only can show photochemical activity in the ultraviolet region. Contraposing to this phenomenon, the method of synthesizing metal ion doped TiO₂ nanopowders by plasma spray has been put forward. The powders were characterized by TEM, XRD, UV-Vis, FTIR and XPS, and the effect of doped ion on the particle pattern, grain size and other physical and chemical performance were analyzed; the effect of doped ion on photocatalytic performance was researched by photocatalytic test, and the effect mechanics and reaction dynamics of photocatalysis were analyzed.The results indicate that the powders prepared by plasma spray appeare globular shape or approximate globular shape, and that the particle size is between 10 and 50 nm. The powders are mainly of anatase when the ion doping content is low, and are mainly of rutile when the ion doping content is high. The anatase content increases firstly and then decreases as the content of iron ion increases, and the bismuth ion doping accelerates the transition from anatase to rutile. The particle size is small when the iron ion doping content is low, and is enlarged when the iron ion doping content is high; yet the particle size is enlarged gradually when the bismuth ion is doped. In FT-IR absorption spectra, the wide-band of absorption between 400 and 1000 cm-1 is corresponding to stretching vibration and variable-angle vibration of Ti-O bond, and it narrows down obviously as the content of iron and bismuth ion increases. The band-edge of intrinsic absorption of ion doped TiO₂ appears red shift from that of pure TiO₂, and the degree of red shift enhances as the content of ion doping content increases. The valency of Fe element is still +3, and that of Ti element is still +4. In the O 1s region of high resolution XPS spectra, theproportion of hydroxyl groups increases and that of absorbed H2O decreases as the iron ion content increases. The photocatalysis activity of TiO2 can be improved obviously by doping metal ion of iron and bismuth. It increases firstly and then decreases as the content of ion increases. The optimal doping content of iron ion is 0.5%, the degradation rate of methyl orange is 81% in 60min, and the photocatalysis activity is 1.8 times of that of pure TiO2. The optimal doping content of bismuth ion is 0.1%, the degradation rate of methyl orange is 92% in 60min, and the photocatalysis activity is 2.0 times of that of pure TiO2. As the heat treatment temperature increases, the anatase content increases firstly and then decreases, and the degradation rate of methyl orange decreases.