Double-wall Carbon Nanotubes Synthesized by the Abnormal Glow Discharge Plasma Method
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Double-wall Carbon Nanotubes Synthesized by the Abnormal Glow Discharge Plasma Method Hiromichi Yoshikawa, Fumiyuki Hoshi, Mutsumasa Kyotani, Takefumi Ishikura1, Motoo Yumura2, Yoshinori Koga2 FCT Research Laboratory, JFCC, 1-1-1 Higashi, Tsukuba, Ibaraki, Japan 1 Frontier Technology Laboratory, Tokyo Gas Co., Ltd, 1-7-7 Suehiro, Tsurumi, Yokohama, Kanagawa, Japan 2 National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki, Japan ABSTRACT Double-wall carbon nanotubes (DWCNTs) and single-wall carbon nanotubes (SWCNTs) have been synthesized by the DC abnormal glow discharge plasma CVD method using methane and hydrogen gas on a Si substrate coated with catalyst. Fe(NO3)2 and Mo(CH3COCHCOCH3)2O2 with Al2O3 support were used as catalysts. The growth temperatures were 1000 - 1400°C and the gas pressures were 9kPa - 13kPa. DC plasma was generated between an array of four W cathodes and a Cu disk anode, and the applied power was 400010000W (2.5-4.0A per cathode, 400-800V). Samples were characterized by high-resolution transmission electron microscopy (HRTEM) and micro-Raman spectroscopy using 514.5 nm Ar ion laser excitation. The HRTEM images showed that many carbon nanotubes had a concentric cylindrical graphene layer structure (DWCNTs). We measured the diameters of the carbon nanotubes (CNTs) from HRTEM images. The outer diameter of the DWNT was 1.52-1.64nm and the inner diameter of the DWNT was 0.73-0.81nm. INTRODUCTION Multi-walled carbon nanotubes (MWCNTs) were found (discovered) by Iijima et al in the carbon deposit on the hot cathode tip of a direct current arc discharge plasma in He [1]. Singlewalled carbon nanotubes (SWCNTs) were also found in arc-produced soot, [2]. Since these discoveries in 1991 and 1993, carbon nanotubes have attracted great attention to their various physical properties. Carbon nanotubes are generally processed by laser ablation of graphite disks [3]; direct current arc discharge in a He, Ar, CH4 environment [1,2,4-7]; or by catalyzed chemical vapor deposition [8-11]. In this study, three types of carbon nanotubes (CNTs): MWCNTs, Double-wall carbon nanotubes (DWCNTs) and SWCNTs, were synthesized using the DC abnormal glow discharge plasma CVD method in a methane and hydrogen gas environment [12]. EXPERIMENTAL DETAILS To produce carbon nanotubes, a direct current abnormal glow discharge was used incorporating four cathodes, each with an independent DC power supply unit. DC plasma was generated between the array of four cathodes and the anode, and the applied power was 400010000W. The voltage was controlled between 400 and 800V according to the set current value between 2.5 and 4.0 A, in order to maintain the abnormal glow discharge (Figure 1). In the
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Vo l tage - Cu rren t Characteri sti c dark discharge
glow discharge
arc discharge glow to arc transition
V o l ta ge V
Townsend region
normal glow
abnormal glow
non-thermal thermal arc arc
1 .E- 06 1 .E-04 1.E-0 2 1.E+ 00 1 .E+02 1 .E+04 Curren t I
Figure 1 The relation between t
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