The effect of electric current on the synthesis of single-walled carbon nanotubes by temperature controlled arc discharge Delong He a, ⁎ , Tingkai Zhao a , Yongning Liu a , Jiewu Zhu a , Guang Yu a , Liling Ge b a State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, PR China b Advanced Material Analysis and Test Center, Xi'an University of Technology, Xi'an 710048, PR China Received 29 April 2006; received in revised form 2 November 2006; accepted 15 May 2007 Available online 24 May 2007 Abstract The effect of discharge current on the synthesis of single-walled carbon nanotubes (SWCNTs) was studied under controlled atmosphere at 500 °C by electric arc discharge. It was shown that the production rate of collected soot was increased but the purity of SWCNTs decreased with increasing discharge current. With a current of 100 A, the SWCNT was very uniform in diameter and a high purity rate of 55% was achieved, as shown by TEM and Raman spectra. Then the influence of electric force, discharge current and catalyst distribution on the formation of SWCNTs was also discussed. © 2007 Elsevier B.V. All rights reserved. Keywords: Carbon nanotubes; Arc discharge; High resolutions electron microscopy 1. Introduction Since single-walled carbon nanotubes (SWCNTs) [1,2] were first reported in 1993, worldwide attention has been paid to the research on their preparations and applications because of their unique structures and attractive properties. Many methods, including arc discharge [1-5], chemical vaporization deposition [6] and laser ablation [7,8], have been applied to produce SWCNT. In contrast to other methods, arc discharge provides an easier and cheaper way. The large-scale production of SWCNT on the order of grams was first realized by Journet et al [3] through electric arc discharge in 1997. Although the SWCNT deposited on the cathode had high density, the deposit only occupied ∼ 20% of the total mass in this conventional electrical discharge. Recently, some progress has been made through modifying discharge equipment and experimental methods. By making an oblique angle (30–50°) between two electrodes during the discharge, long ropes of well-aligned SWCNT were synthesized under a hydrogen and argon atmosphere by Liu et al [9]. Thirty milligrammes of the ropes were obtained at a 30% purity rate of SWCNT during the 5 minute discharge. Zhao and Liu [5] modified the conventional arc discharge apparatus by adding a temperature controlled unit inside the vacuum chamber. The SWCNT with a purity of about 95% after purification could be produced under the current of 60 A at higher temperatures. Ando et al [10] reported that the SWCNTs could be mass-produced by plasma jet assisted DC arc discharge. The highest yield of the soot was 1.24 g/min when current was 100 A and the best purity of the SWCNTs was about 50% when current was 70 A. Even big progress has been made in electric arc discharge, the production rate of SWCNT is still very low and it could not supply enough samples to satisfy the need of research or industry. To increase discharge current is prerequisite to improvement of SWCNT output with electric arc discharge. However, the influence of big current on the production of SWCNTs is not yet known. The purpose of the present paper is to study the current effect on the synthesis of SWCNT in a temperature controlled arc discharge furnace. The large-scale and high purity SWCNT with very uniform diameter are synthesized using Ni–Co catalyst at 500 °C by our self-designed temperature controlled arc discharge furnace [5,11]. Furthermore, the influence of big Diamond & Related Materials 16 (2007) 1722 – 1726 www.elsevier.com/locate/diamond ⁎ Corresponding author. Fax: +86 29 8266 3453. E-mail address: dlhe2008@126.com (D. He). 0925-9635/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.diamond.2007.05.006