Elucidating the effect of heating induced structural change on electrical and thermal property improvement of single wall carbon nanotube

We have clarified that the electrical and thermal properties of single-walled carbon nanotubes (SWCNTs) are improved by multiple structural changes (wall number, diameter, and crystallinity) induced by high temperature treatment. Focusing on the relationship between structural change and electrical and thermal properties, high-purity SWCNTs were fabricated using the water-assisted CVD method and treated at high temperatures (1500–2000°C) in an argon atmosphere. We showed that the electrical and thermal properties of the SWCNTs were improved by ∼2.9 and 3.0, respectively, which required lower treatment temperatures than for multi-walled CNTs (MWCNTs). In addition to the crystallinity improvement, the wall number and diameter increased with treatment temperature. When compared to as-grown SWCNTs of similar wall number and diameter, the heat treated SWCNTs exhibited higher electrical and thermal properties, which suggested that the property improvements could be attributed to not only to the wall number and diameter but also to the improvement in crystallinity.