THERMAL EXPANSION IN SINGLE-WALLED CARBON NANOTUBES AT DIFFERENT TEMPERATURES

Abstract

Energy stored in a bond depends on the bond length and bond angle. We use computer simulation software to measure the bond lengths and bond angles, diameters and other parameters of single-walled carbon nanotubes (SWCNTs), and employ the results to determine thermal expansion of SWCNTs in the radial and axial directions. It is found in this study that at low temperatures and even at room temperature, SWCNTs show negative thermal expansion in both the radial and axial directions (the diameter and length both decrease with the increase in temperature). At high temperatures the expansion becomes positive in the radial and axial directions (the diameter and length both increase with increasing temperature). Thermal expansion in the radial direction does not depend on the tube helicity. SWCNTs of large diameter show higher thermal expansion in the radial direction than that for small diameter tubes up to 700 K, but beyond 700 K the opposite occurs.