An analysis of carbon nanotube structure wettability before and after oxidation treatment
In this work contact angle measurements have been carried out on different carbon nanotube-based materials. Thin layers of entangled carbon nanotubes have been considered, together with thick mats of vertically aligned carbon nanotubes. Pressed single-walled carbon nanotubes and graphite have also been considered, for comparison.
In particular, the properties of the as-grown thick carpets have been compared to those of the oxidized material. Oxidation treatments have been performed either by chemical oxidation with a nitric/sulfuric acid mixture or by applying a bias voltage of 10 V on the material. Tests have been performed using three liquids with differing polarity (water, dimethylsulfoxide and diiodomethane). Very high hydrophobicity was observed for the top surface of the aligned carbon nanotube mats, but after oxidation a dramatic reduction in the contact angle was observed, bringing about a hydrophilic behaviour. Theoretical calculations of the bulk pore distribution of the material have been made to estimate the liquid percolation through the oxidized carpet's surface.