Synthesis and purification of multi-walled carbon nanotubes for field emitter applications

Abstract

Carbon nanotubes have been attracting considerable attention because of their unique physical properties and their potential use in a variety of applications. Multi-walled carbon nanotubes (MWNTs) have properties which make them intrinsically suitable for acting as field emitters, such as sharp tips with an nm-scale radius of curvature, high mechanical stiffness, chemical inertness and electrical conductivity. We have studied the synthesis and purification of MWNTs. MWNTs were made by a d.c. arc method. We have developed a high-yield production method for MWNTs using a rotating cathode arc method. The advantages of this method are high stability and reliability of handling, and continuous mass production is possible with this method. The development of a purification method for carbon nanotubes is quite important for the utilization of carbon nanotubes. Two purification methods of MWNTs from cathode deposition by arc plasma were conducted by means of the different oxidation rates of various graphites. One is a chemical method and the other is a physical method. Both can purify MWNTs up to their optimum conditions. Using field-emission microscopy (FEM), emission patterns from MWNTs were observed. Conical beams from open-ended MWNTs were observed, and the emission was very stable. Further to the FEM study, cathode ray tube (CRT) lighting element equipped with MWNT field emitters was manufactured. Stable electron emission, adequate luminance and the long life such CRTs demonstrate that MWNTs are a very promising material for field electron emitters.