Influence of chamber volume in single-walled carbon nanotube synthesis by an electric arc
Résumé
Single-walled carbon nanotubes (SWCNTs) were produced by an electric arc process in a low-pressure chamber with vertical electrodes using heterogeneous graphite anodes containing nickel and yttrium catalysts. The influence of the chamber volume (18, 25 and 60L) and graphite grain size (1 and 100m) of the anode on the resulting products was analysed. This was correlated with the physical properties of the plasma as studied by optical emission spectroscopy and with the temperature of the gaseous atmosphere surrounding the plasma as measured using thermocouples. Nanotube yield and purity were evaluated from high-resolution transmission electron microscopy. Results showed a strong influence of the heterogeneous anode grain size. It was found that the optimal synthesis conditions correspond to an arc chamber volume of 25L and a graphite grain size of 1m. In that case the plasma temperature and the carbon over nickel concentration ratio in the plasma differ notably from those observed under the other synthesis conditions. It was also found that a slower temperature rise of the gaseous atmosphere surrounding the plasma and a higher anode erosion rate are associated with a higher SWCNT yield. These results were interpreted considering the vapour-liquid-solid nanotube formation model.
Mots clés
Synthesis conditions
Temperature rise
Vertical electrodes
Electric arcs
Emission spectroscopy
Grain size and shape
Graphite
Graphite electrodes
Nanotubes
Plasmas
Single-walled carbon nanotubes (SWCN)
Thermocouples
Transmission electron microscopy
Yttrium
Atmospheric temperature
Anode erosion
Arc chamber
Gaseous atmosphere
Grain size
Graphite anode
Graphite grains
Nanotube formation
Nickel concentrations
Optimal synthesis
Plasma temperature
Single-walled carbon