Study On Surface Modification And Dispersion Properties Of Carbon Nanotubes

Carbon nanotubes are one-dimensional nano-material with unique hollow structure. Because of strong adsorption capacity, excellent mechanical properties, excellent electrical and thermal conductivity, Carbon nanotubes have been widely used in many areas such as environmental protection, materials, information and electrochemical application prospects and so on. However, carbon nanotubes were difficult to disperse other substances because of their strong intermolecular interactions which limited the application of carbon nanotube in large.Therefore, the surface modification and the determination of the solubility of carbon nanotubes were studied in this paper and the main study were conducted as follows.The surface of carbon nanotubes was modified by nitric acid oxidation method. The single factor test had discussed several factors on the reaction including of the reaction temperature, reaction time and concentration of nitric acid and the results showed that the bent parts of carbon nanotubes was first opened during the reaction and the wall gradually got thinner; Combining the orthogonal test with the weight loss as the rateindex, the optimum conditions of reaction for nitric acid oxidatation were determined as follows:the temperature was80℃, the reaction time was20h, and the concentration of nitric acid was3mol/L. By characterization of the reaction products using SEM and IR, the results indicated that the carbon nanotubes was successfully prepared by method of nitric acid oxidation with active group of carboxyl, hydroxyl and carbonyl on their surface.Carboxylated carbon nanotubes were chloride-modified by thionyl chloride. By characterization of the reaction products using SEM and IR, the effect of time on reaction was investigated and the results showed that the peak height and peak area of the chloride groups of peaks got bigger and higher with increasing time and bigger within a certain reaction time and the optimum preparation time was20h. The chloride carbon nanotubes were modified by octadecylamine and the products were characterized by SEM and TG in order to investigate the effects of reaction time, the results showed that the peak height and peak area of the amide characteristic groups of peaks became higher and bigger with increasing time and the better preparation time was48h. In additional, the grafted rate of octadecylaminemodified carbon nanotubes was49.8%.The dispersion of original carbon nanotubes, carboxylated carbon nanotubes, chloride carbon nanotubes, octadecylamine/carbon nanotube were separatedly determined and compared in ethanol, acetone and disulfide carbon and the dispersion of the four samples in ethanol respectively were0.0895mg/mL,0.123mg/mL,0.101mg/mL and0.181mg/mL; the dispersion in acetone respectively were0.0265mg/mL,0.0344mg/mL,0.0608mg/mL and0.0751mg/mL and the dispersion of octadecylamine/carbon nanotube in the carbon disulfide was1.119mg/mL. All these results showed that the ability of carbon nanotubes to disperse in the three solvents after surface modification was enhanced. Determine and compare the electromagnetic shielding performance of conductive paper that mixed with the original carbon nano-tubes and octadecylamine/carbon nanotube, the results show that the electromagnetic shielding performance of conductive paper mixed with edoctadecylamine/carbon nanotube was better than the original carbon nanotubes and seperatedly with the electromagnetic shielding effectiveness of8.38dB at the frequency of935MHz and the electromagnetic shielding effectiveness of4.8dB at the frequency of85MHz. These were respectively improved6.87dB and2.85dB.