Removal of Oxidation Fragments from Multi-walled Carbon Nanotubes Oxide Using High and Low Concentrations of Sodium Hydroxide

Abstract

Modification of multi-walled carbon nanotubes surface (MWCNT) using the mixture of $${{{\rm HNO}}_{3}/{{\rm H}}_{2}{{\rm SO}}_{4}}$$ is widely employed for MWCNT surface oxidation, but it also leads to shortening and thinning of the CNT layers causing fragmentation. The carbonaceous fragments had adsorbed on the surface is not removed from the sample in conventional treatments; however, the addition of NaOH successfully cleans the oxidized material. In this article, MWCNT was functionalized using $${{{\rm HNO}}_{3}/{{\rm H}}_{2}{{\rm SO}}_{4}}$$ as oxidizing agent and evaluate the impact of using high and low concentrations of NaOH to purify CNT oxide. The presence of oxidized groups as hydroxyl and carboxyl has been demonstrated by FTIR. The thermal stability of MWCNT and MWCNT-O after and before purification was studied by TGA, and the degree of its crystallinity was examined by XRD. The defect degree occurs during the oxidation process was confirmed by Raman spectroscopy. TEM images showed the presence and the absence of wrinkles and the adsorbed carbonaceous fragments.