Preparation And Properties Of Carbon Nanotube/TiO₂ Composite Material

Photoelectric effect had been discovered by German scientists Hz in 1887, soon it became a hotspot. Because of the good photoelectric effect, stable physical and chemical properties, researches of TiO₂ have been increased. In short, photoelectric effect is a phenomenon that bound electrons become a free electron in the role of light in certain materials. Study and utilization of photoelectric effect of TiO₂ in the following several aspects commonly: one is to use the photocatalytic effect to degrade organic molecules of sewage and waste water; second is the use of its photo-cathode effect for anti-corrosion treatment.However, applications of TiO₂ have limitations in these two areas. In its application of photocatalytic, first, TiO₂ band gap is 3.2eV, only when it absorbs UV which wavelengths less than 380nm it can show the catalytic activity, while in sunlight of solar spectrum UV accounted for only 3 to 5 percent; second, the semiconductor carrier load is high, but the quantum efficiency is low. In its anti-corrosion applications, as leave the illumination, the photo-cathode effect is come to an end, so it limited the scope of application. To overcome these two limitations, this paper doped carbon nanotube to form composite materials with TiO₂ to its modification, increase its scope and application of light response. Then doped by different proportions and different preparation methods in order to receive TiO₂ material both have a suitable photocatalytic degradation and corrosion protection.The research results are as follows:1. Carbon nanotube/TiO₂ composite powders of same proportion was prepared by high energy ball milling method and sol-gel method, then used these composite powders in UV degradation experiments of methyl orange. These composite powders were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and X-ray diffraction(XRD) and so on. The results show that composite powder prepared by high energy ball milling has a performance of fine and uniform particles, uniform structure and good decentralized nature. The study of photocatalytic degradation experiment by UV spectrophotometer found that the TiO₂ powder after carbon nanotube doped has better photocatabytic properties. This indicates that carbon nanotube can increase the range of the light response of TiO₂, also increase its quantum efficiency. The composite powder prepared by high energy milling has the best performance, and high energy ball milling method has a better application value.2.Carbon nanotube/TiO₂ composite powders of different proportion was prepared by high energy ball milling, then used these composite powders in UV degradation experiments of methyl orange, and using UV spectrophotometer to test the experimental results. The test results show that when the ball milling time is 12h, the ball milling speed is 300r/min, the weight of carbon nanotube is the 5%, the best performance the composite powder has, too much or too little of the doping is not conducive to the improvement of its photocatalytic properties.3. Carbon nanotube/TiO₂ sol was prepared by sol-gel method, and used dip-doped method to depositing carbon nanotube/TiO₂ composite coating on mild steel and copper, than calcined this coating and obtained the final coating. SEM, XRD and other methods were used to study the characterization of the composite coating. The results showed that after doping carbon nanotube, the continuity and integrity of the composite coating were improved, also the generation of pitting was reduced; XRD test showed that after calcination at 450℃, the coating was well crystallized. The electrochemical corrosion experimental analysis shows that in dull conditions and doped carbon nanotube, TiO₂ coating showed a more favorable anti-corrosion property and a broader application scope. These phenomena demonstrate the unique electrical properties of carbon nanotube can absorb and store electronics, show carbon nanotube capacitors.4. Carbon nanotube/TiO₂ coating of different ratios was prepared by sol-gel method and dip-doped method, used electrochemical corrosion experiments to analysis this coating. The results show that when the doping amount of carbon nanotube in the 5wt%, the composite coating has the best anti-corrosion, high and low doping is not conducive to the integrity of the coating. Electrochemical impedance spectroscopy also shows that, 5wt% doped carbon nanotube/TiO₂ has a higher impedance.