Anisotropies in carbon nanotube synthesis by the hydrogen arc plasma jet method

Single-wall carbon nanotubes were prepared under hydrogen gas atmosphere with a DC arc discharge maintained between the tip of a sharpened graphite cathode and an anode formed by a catalytic mixture of graphite, FeS, Ni, Fe and Co compressed powders. The cathode is placed with an inclination with respect to the anode, so that the plasma jet of the discharge is deviated towards the empty space of the growth chamber. Samples were classified and analyzed according to their type and growth positions relative to the direction of the plasma jet flow. Characterization of the samples was performed with mass spectrometry, Raman spectroscopy and transmission electron microscopy. A subtle variation is found in the properties of the nanotubes obtained in different locations due to the directionality of the plasma jet flow. Observed differences in sample properties may be qualitatively understood in terms of accepted mechanisms of SWNT growth.