Cleavage of catalytic ally grown carbon nanofibers into hydrophilic segments by oxidation in a mixture of concentrated HNO3-H2SO4 in an autoclave

Abstract

The catalytically grown carbon nanofibers were treated by a mixture of concentrated nitric aid and sulfuric aid in an autoclave at temperature 333, 363 and 423 K. It was found that the samples treated at 363 K and 423 K were still well dispersed in water 15 hours later, indicating that carbon nanofibers can be made hydrophilicy. It was also found that the dispersion was destroyed when the pH value was lowered by adding acid. The results are significant when the carbon nanofibers are used as enhancing component in polymer composite material because several hundreds of nm are perfect size and the hydrophilicity controls the dispersion of CNFs in the polymer media. It is concluded that the amount of the oxygen-containing groups on the surface and the hydrophilicity of the carbon nanofibers can be controlled by the treatment temperature, and that the carbon nanofibers can be cleaved into uniform segments.