  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.
