Research Of Composition Structure And Corrosion Resistance Of Ti-O Films Prepared By Reactive Magnetron Sputtering Using CO₂Gas

With the rapid development of society, Much attention has been paid to the issues of environmental pollution and energy crisis. Titanium dioxide(TiO2) is an n-type semiconductor, as one of the most suitable photocatalysts due to their attractive characters, such as low cost, non-toxicity and so on, widely applied in the fields of waste water treatment, air pollution control, the conversion of solar energy, water photolysis of hydrogen, self-cleaning glass and corrosion prevention. However, as a photocatalyst, TiO2has two major drawbacks:stimulated by visible light little and high electron-hole recombination rate. Furthermore, TiO2in a role of the photocatalyst is mainly in nano-powder, causing separation difficulties and low catalyst recycling rate. Only by preparing a thin film of TiO2which is stimulated by visible light can widen its applications. In order to solve the problem about titania absorption of visible light, doping carbon can be utilized to stimulate a response band width of TiO2photocatalysis. In this paper, using carbon dioxide(CO2) in gas offered carbon source and magnetron sputtering method were employed to form the carbon-doped Ti-O film. The film composition, structure and corrosion resistance were also studied.Used CO2as a carbon source, a series Ti-O films were prepared by changing the volume flows of oxygen and carbon dioxide. The composition, structure and corrosion resistance of the films were measured by X-ray diffraction(XRD), Raman spectroscopy, X-ray photoelectron spectroscopy, UV-vis spectrophotometer and electrochemical methods. The XRD results showed that CO2gas as C source in preparing doped Ti-O films can promote the appearances of TiO crystalline phases. When CO2meet with oxygen, there is a decreasing trend to form the TiO crystalline phase.By measuring the absorption spectrum of the film and calculate the band gap width, it is assumed that the reaction atmosphere inflenced width of band gap. Particularly, when the atmosphere contained no oxygen, the influences become significant. The use of CO2as a carbon source and an oxygen source successfully synthesized C-doped Ti-O thin film and the doping carbon atoms were formed through substituting oxygen atoms.Excess surface carbon is mainly caused by exposing to the atmosphere. only increasing CO2flux, the film lattice doped C significantly reduced, indicating that Ti atoms and O atoms preferentially bonds.When CO2and O2coexisted, the amount of the lattice doping C significantly reduced and and content of Ti2+relative became lower..At the same time, the results of electrochemical impedance measurements showed that the carbon incorporated into TiO2lattice was beneficial to extend the life of photo-generate carrier, decrease the electronic exchange of resistance and make the oxidation-reduction reaction emerge on the surface.Although there was little different among the results of polarization curves, the remaining five samples showed better corrosion resistance compared to the rutile phase of sample1#with proper corrosion resistance. Corrosion potential of samplel#was a relatively low and the corrosion probability was relatively minimal. The study of corrosion speed had taken corrosion current density and corrosion rates into consideration.The effect of annealing on the composition and structure of thin films was also studied in the paper. XRD and Raman spectroscopy results indicated that the crystalline phase of the as-annealed films was mainly anatase and the extent of crystallization increased much. It should be pointed out that annealing could improve the crystal quality of TiO2and reduce crystal defects in the TiO2lattice.The original carbon contamination on the surface of unannealed films significantly declined after annealing and the Ti-C bonds in surface of the crystal lattice were broken after annealing, but Ti-C bonds was still existed in the deeper surfaces. After annealing, the oxygen circumstance had changed, titanium element in surface existed as Ti4+. At the same time, Ti-C bonds were converted into Ti-O bonds coating on the surface.The study results of this paper proved the researchers have designed a feasible method to use carbon dioxide as a carbon source for the synthesis of carbon-doped titanium oxide films, extending absorption band film and increasing the absorption of visible light. CO2functioned as carbon source improved to form TiO crystalline phase and Ti2+had a significant decrease after carbon-doped. The content of carbon was dropped down by adding CO2flux. When CO2and O2coexisted, they would restrain the formation of TiO phase and carbon content declined obviously, incorporating carbon into TiO2lattice is beneficial for extending the life of photo-generate carrier, decreasing the electronic exchange of resistances and making the oxidation-reduction reaction emerge on the surface.