Spectroscopic study of double-walled carbon nanotubes functionalization for preparation of carbon nanotube / epoxy composites

TL;DR

This study uses spectroscopic techniques to analyze amino functionalization of double-walled carbon nanotubes and its impact on composite interfaces, electrical properties, and structural integrity.

Contribution

It provides detailed spectroscopic evidence of selective functionalization on DWCNTs and links chemical modifications to improved composite interface properties.

Findings

Amino groups graft onto external walls of DWCNTs at defect sites.

Functionalization enhances DWCNT/epoxy interface bonding.

Electrical percolation occurs mainly through inner metallic tubes.

Abstract

A spectroscopic study of the amino functionalization of double-walled carbon nanotube (DWCNT) is performed. Original experimental investigations by near edge X-ray absorption fine structure spectroscopy at the C and O K-edges allow one to follow the efficiency of the chemistry during the different steps of covalent functionalization. Combined with Raman spectroscopy, the characterization gives a direct evidence of the grafting of amino-terminated molecules on the structural defects of the DWCNT external wall, whereas the internal wall does not undergo any change. Structural and mechanical investigation of the amino functionalized DWCNT / epoxy composites show coupling between epoxy molecules and the DWCNTs. Functionalization improves the interface between amino-functionalized DWCNT and the epoxy molecules. The electrical transport measurements indicate a percolating network formed only by inner metallic tubes of the DWCNTs. The activation energy of the barriers between connected metallic tubes is determined around 20 meV.