Structure And Property Of The Shortened Carbon Nanotubes By Cutting In Molten Nitrate

Multi-walled carbon nanotube (MWNT) is a promising one-dimensional nanomaterial of great potential for applications because its tubular structure whose length is a thousand times its width, and excellent mechanical properties. The research on the MWNTs are always interesting and cutting-edge topics in the international area. MWNTs with relatively short lengths have been attracting strong attention because such MWNTs are expected to provide as nano-electronic devices and supercapacitor electrode materials due to short size and rich chemistry compared to the long ones.In this paper, we etched the MWNTs into different lengths and roughness in a molten potassium nitrate based on the control of reaction time and temperature. Transmission electron microscopy and field-emission electron microscopy were utilized to investigate the morphological properties of the short MWNTs (s-MWNTs). X-Ray diffractomer and Raman spectra were used to analysis the structural features of the s-MWNTs. In order to investigate the suspensibility of the s-MWNTs, the suspensions of the pristine MWNTs and the s-MWNTs in water with the concentration of 0.15 mg/ml were prepared by sonication. Cyclic voltammograms and electrochemical impedance spectroscopy were used to figure out the specific capacitance of the s-MWNTs.The results show that the MWNTs can be etched and cut short gradually in molten potassium nitrate as the increasing of time and temperature. The defective carbon is removed due to a selective oxidation of the molten nitrate. The value of ID/IG in the Raman spectra of the s-MWNTs is decreased, indicating that the ordering of the s-MWNTs is improved. It confirms that the present method is simple and effective for preparing s-MWNTs. The s-MWNTs can form stable dispersion in the polar solvents. The electrochemical results have proved that the specific capacitance of the s-MWNTs can be increased, and it increases with the length of the MWNTs decreasing.