Processing of single wall carbon nanotubes and implications for filling experiments
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Processing of single wall carbon nanotubes and implications for filling experiments Satishkumar B. Chikkannanavar, Brian W. Smith, Richard M. Russo, Ferenc Stercel and David E. Luzzi Laboratory for Research on Structure of Matter Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA 19104-6272, USA
ABSTRACT Single wall carbon nanotubes (SWNTs) have been processed in different schemes to get clean material for use in various filling experiments. The SWNTs synthesized by different methods require different processing schemes, and this is presumably due to heterogeneous nature of the various contaminants present along with the carbon nanotubes. For the pulsed laser synthesized SWNTs, a combination of nitric acid, hydrogen peroxide and hydrochloric acid treatment gives best results and the purified SWNTs give best ever filling fraction for fullerene, C60 of ~90%. The processing improves the surface cleanliness of SWNTs, in turn giving greater access for the target molecules, and hence the higher filling fraction. For the carbon arc produced SWNTs, air oxidation followed by treatment with nitric acid has been found to work best and the processed SWNTs have been used for filling experiments with metal chlorides. Both these processing schemes still leave a small fraction of catalyst impurities in the final material, thus the material quality of filled material and hence its properties depend on the processed material used for the filling experiments.
INTRODUCTION Ever since the discovery of single wall carbon nanotubes (SWNTs) [1-3], there has been an intense research effort focused towards the processing, characterization and property modification, apart from means to produce them by alternate synthesis methods. In order for the well-characterized carbon nanotubes to be available for various studies, one needs to develop methods to process or purify them. This is in order to remove the impurities, which accompany the carbon nanotubes during the formation process. The heterogeneous nature of the impurities has made the processing methods more elaborate and involved in terms of the details of chemical or physical processes involved. Various schemes of processing have been reported over the years for SWNTs synthesized by different methods [4-7]. In this paper we discuss the processing of SWNTs and implications for the various filling experiments.
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EXPERIMENTAL We have carried out the processing of SWNTs obtained by pulsed laser vaporization (PLV-SWNTs) and carbon arc (CA-SWNTs) methods. The laser synthesized material, Tubes@Rice was obtained from Rice University, which was synthesized in a pulsed-laser vaporization technique using Co/Ni catalysts [2]. The carbon arc produced SWNTs were provided by Prof. P. Bernier, CNRS, France and synthesized using Y and Ni as catalysts [3]. The collarette portion of the carbon arc process was subjected to a combination of static air oxidation and acid treatment. In a typical processing experiment ~ 20 mg of collarette (CA-SWNTs) was anneal
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