Variations of interlayer spacing in carbon nanotubes

The analysis of previous classic and recent reports on the interlayer distances in MWCNTs is described in this review. Simulations on interlayer spacing, applications of Raman spectroscopy, X-ray and neutron diffraction methods, influence of synthesis methods, heat and radiation (gamma-rays, electron and ion beams) treatments are discussed, as well as the polygonization and intercalation of CNTs. It is shown that the spacing values of DWCNTs and MWCNTs vary from 0.27 up to 0.42 nm. The most common values are in the range of 0.32-0.35 nm and do not strongly depend on the synthesis method. Diameter of CNTs and the symmetry of layers influence the interwall spacing.