Surface modification of carbon microspheres by KMnO₄

Carbon microspheres (CMSs) were synthesized by chemical vapor deposition in an Ar atmosphere using deoiled asphalt as carbon source. KMnO^₄ aqueous solutions with different concentrations were used to oxidize the CMSs to form MnO₂-coated CMSs (MnO₂/CMS composites) and H₂ C₂ O₄ solution was used to wash the MnO₂/CMS composites to remove MnO₂ to obtain oxidized CMSs. The morphology and structure of the CMSs before and after MnO₂ deposition, as well as the oxidized CMSs, were characterized by field-emission scanning electron microscopy and X-ray diffraction. The dispersion of the oxidized CMSs in water and ethanol was also investigated. A uniform MnO₂ nano-coating was formed on surface of the CMSs when a 0.1mol/L KMnO₄ aqueous solution was used. When an excess amount of H₂ C₂ O₄ solution was used to wash away the MnO₂ nanocoating, the resulting CMSs have oxygen-containing groups, such as hydroxyl, carbonyl and carboxylic, and can be well dispersed in water and partly dispersed in ethanol.