Effective functionalisation of carbon nanotubes for reinforcement application in liquid state processed aluminium composites: A relatively greener approach

This paper outlines an innovative approach to functionalise multiwall carbon nanotubes at a reduced functionalisation time and energy consumption, preserving their structural integrity, with objective of potential application of the carbon nanotubes as reinforcement in aluminium matrix composites processed through liquid state method. Longstanding problems of aluminium carbide formation as reaction by-product in aluminium matrix composites is expected to be reduced by reinforcing the carbon nanotubes functionalised through the developed method. Carbon nanotube surfaces were oxidised following four different methods using solutions of different acids at different parametric combinations, and the best possible method was identified through dispersion stability test, Fourier-transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy and thermogravimetric analysis. Results revealed that primary oxidation by 6M HNO₃, followed by subsequent oxidation by weak acid H₂O₂ generated functionalised carbon nanotubes with satisfactory dispersion stability, preserved graphitic structure, high degree of structural integrity, less structural distortion and less carbon nanotube fragmentation.