Research On Polymer/CNTs And TiO₂ Nanotubes-based Composites

Nanocomposites have been the research focus in the world in 21th century since nanotechnology has been applied in the materials fields. There are two hots including polymer-based nanocomposites and noble metal catalysts nanocomposites. Because the polymer-based nanocomposites have the advantages of all the components, the nanocomposites with excellent and novel properties can be prepared by designing the structure of the nanocomposites. The noble metal electrocatalysts are very important in the research of the fuel cell. However, the application of the fuel cell has been delayed by the high cost and low catalytic efficiency of noble metal electrocatalysts. So the good carrier materials which can low the cost and imporve the catalytic efficiency have recently been paid much attention.In this paper, we reviewed the latest development in the research of the nanocomposites. With the focus on the polymer/CNTs nanocomposites and the electrocatalysts nanocomposites using TiO₂-NTs as carrier, we have fabricated the polymer/CNTs nanocomposites, TiO₂-NTs, Pd/TiO₂-NTs and Pt/TiO₂-NTs electrocatalysts nanocomposites. The properties of the synthesized nanocomposites have been investigated in details. The main content is the following:1. The three kinds of polymer/CNTs nanocomposites, including poly(methyl methacrylate)/CNTs, epoxy/CNTs and polystyrene/CNTs, have been produced successfully by means of in-situ polymerization method. The influence of CNTs on the friction and wear properties of the polymer base were investigated in details.The results showed that the introduction of CNTs greatly lowed the friction coefficient and wear rate of the nanocomposites. The friction and wear properties of the pure polymer were effectively improved. And the best reinforcement impact could be obtained at the right introduction weight of CNTs. For PMMA/CNTs, the introduction of 1.0wt% CNTs can make the best reinforement. For EP/CNTs and PS/CNTs, the best tribological properties of the nanocomposites can be obtained at the introduction of 1.0wt% CNTs. And the reinforcement mechanisms of CNTs were proposed. The improvements on the tribological properties of polymer/CNTs nanocomposites were mainly attributed to the following factors: 1) super high mechanical and thermal properties of CNTs; 2) the unique structure of the polymer/CNTs nanocomposites.2. The copolymer have better properties and structure than the single polymer. PMMA/PS/MWNTs copolymer composites have been fabricated successfully by means of in-situ polymerization method.The introduction of MWNTs improved the friction and wear properties of the copolymer base. The best tribological properties of the copolymer nanocomposites were obtained at the introduction of 1.5wt% MWNTs. The wear rate of the nanocomposites was decreased by 43.4% from 2.3×10⁴ mm³ N^-1m^-1 to 1.3×10⁴ mm³ N^-1m^-1. The mechanisms of the improvements on the tribological properties were discussed by analysising the experimental data of the structure, tribological experiments of the copolymer nanocomposites.3. PANI/MWNTs have been synthesized successfully by means of in-situ chemical polymerization method. The electrochemical capacitance performance of the composites was investigated in the solution of 1M NaNO₃ by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge tests with a three-electrode system. At the current of 5mAcm^-2, PANI/MWNTs showed the higher specific capacitance values of 328 Fg^-1 than the pure PANI (193 Fg^-1). The main reasons may be attributed to the following factors: 1) The high surface area of MWNTs can help the conjunction between MWNTs and PANI; 2) the well-coated MWNTs of the composites produced a porous three-dimensional network, which might provide a large surface area and allow excellent electrolyte access and storage in three dimensions. Therefore, PANI/MWNTs composites have more available active sites for faradic reaction and larger specific capacitance than pure PANI. 3) The super high mechanical properties of MWNTs can improve the stability of the composites and excellent conductivity of MWNTs can low the resistance of the composites. So PANI/MWNTs composites with good stability have the promising application as the electrochemical capacitors. 4. The carrier materials with high surface and good stabiligy have attracted much attention because they can low the load of noble metals and improve the catalytic efficiency. So the anatase TiO₂-NTs have been synthesized through the hydrothermal process. Pd/TiO₂-NTs and Pt/TiO₂-NTs electrocatalysts have been fabricated by chemical reduction. The catalytic activity of the two electrocatalysts for CH₃OH andN₂H₄ ? H₂O have been investigated in details. The negative voltage and the highcurrent were obtained. The main factors were the high surface and good stabiligy of TiO₂-NTs. The results imply that TiO₂-NTs are good carrier materials of the fuel cell electrocatalysts.