Improving the wettability of aluminum on carbon nanotubes

The wetting of a metal on carbon nanotubes is fundamentally difficult due to the unusually large difference between their surface tensions and is a bottleneck for making metal carbon nanotube (CNT) composites. Here, we report a simple method to enhance the wettability of metal particles on the CNT surface by applying aluminum, which is the material with the largest surface tension. This method involves two steps: (i) Al nanoparticles are decorated on multiwalled carbon nanotubes by electroplating and (ii) Al powder is further spread on Al-electroplated CNTs, followed by high-temperature annealing to accommodate complete wetting of the aluminum. The large surface tension difference is overcome by forming strong Al C covalent bonds initiated by defects of the CNTs. The decrease in the D-band intensity, the G-band shift in the Raman spectroscopy and the formation of Al C covalent bonds, as confirmed by X-ray photoelectron spectroscopy, were in agreement with our structural model of CNT-vacancy-O-Al determined by density functional calculations. Crown Copyright (C) 2011 Published by Elsevier Ltd. on behalf of Acta Materialia Inc. All rights reserved.