Plasma-enhanced fluorination of carbon materials

The effect of r.f. plasma-enhanced fluorination using CF 4 has been investigated on several types of carbon materials exhibiting various levels of crystallinity. The samples ranged from highly graphitized compounds (exfoliated graphite for instance) to carbon blacks with small coherent domains and high specific surface areas. In graphitized materials, the PEF treatment yields the formation of an insulating layer composed of covalent C-F bonds on the outermost surface. These results differ from those obtained with F 2 -gas fluorination, for which an important amount of intercalated F species, characterized by semi-ionic C-F bonds, is observed In the case of the treatment of carbon blacks, the addition of O 2 or Ar to CF 4 gives rise to an in-situ activation of the powder, leading to an increase of surface perfluorinated CF n groups. A 2-step fluorination mechanism has been proposed.