Jaime Gallego

Activation energies and structural changes in carbon nanotubes during different acid treatments

In this work, we studied the effect of acid type in the final properties of CNTs as the resistance to air oxidation; for this, different techniques of characterization were used such as Raman spectroscopy, thermogravimetric analysis, and chemical analysis by ICP-AES. Through Raman spectroscopy, it is possible to monitor the structural changes induced by acids and this is reflected in changing of the activation energies for the different processes determined by thermogravimetric analysis; also by ICP-AES analysis, it was shown that the inorganic material was eliminated efficiently with the acid treatments used in this study.

Intershell spacing changes in MWCNT induced by metal–CNT interactions

The intershell spacing in different regions of a multi-walled carbon nanotube (MWCNT) was determined by analysis of high resolution transmission electron (HR-TEM) micrographs. Three general effects can be pointed out, (1) the regular intershell spacing of a CNT is bigger than that in a graphitic carbon because the curvature generates geometrical and electronic deformations which increase repulsion forces between the graphene sheets, (2) when an extra curvature appears, e.g. at the tip of a closed CNT or in a bamboo-like structure, the intershell spacing is expanded due to the extra repulsion caused by the combination of pentagonal and heptagonal rings imbibed in the hexagonal lattice, and (3) when a metal particle interacts with a CNT, the intershell spacing is compressed due to strong metal-CNT interactions.