Multiwalled carbon nanotubes prepared by hydrogen arc

Multiwalled carbon nanotubes (MWNTs) with high quality were prepared by DC are discharge of pure graphite electrodes in hydrogen gas. Because these MWNTs co-existed with few carbon nanoparticles compared with the usual MWNTs prepared in helium gas, their purification could also easily be done by infrared irradiation in air at 500 degrees C for 30 min. Resonance Raman spectra of purified MWNTs were measured, and breathing modes at about 500 cm(-1) corresponding to a very thin central hole of about 5 Angstrom diameter were found. A new peak at about 1840 cm(-1) appeared for pristine MWNTs, and its intensity strongly depended on the preparation conditions (pressure of hydrogen gas). The measurement of temperature dependence for electric resistance of MWNTs showed metallic or semiconducting tendency. Purified MWNTs could be used as bright and long-life held emitters for cathode ray tubes, and a desirable current density of 1 mA/cm(2) could be stably achieved at a field of 1.2 V/mu m. (C) 2000 Elsevier Science S.A. All rights reserved.