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 AlC 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 AlC covalent bonds, as confirmed by X-ray photoelectron spectroscopy, were in agreement with our structural model of CNTvacancyOAl determined by density functional calculations.