Formation of carbon needles from fluoropolymer by ion irradiation followed by defluorination

A new carbon material with a unique surface has been created from polytetrafluoroethylene (PTFE) using a combination of ion irradiation and defluorination. In this study, the morphological change in the PTFE surface due to ion irradiation is observed in detail, and the mechanism of needle formation is investigated. At lower irradiation doses, hollows were formed, due to evaporation of PTFE. The number of hollows increased with dose, and the surface became covered with hollows and edges. Heating effects play an important role when the edges evolve into needles. The specimen covered with projections at a high density (3 x 10(5) mm(-2)) was placed in an evacuated glass tube with sodium metal, and kept at 473 K for 48 h. Because of the defluorination, the needles became conductive and could be observed by electron microscopy without using metal deposition. About 92% of the fluorine was eliminated by the reaction, and amorphous carbon needles were generated perpendicular to the target PTFE specimen. (C) 2003 Elsevier Science B.V. All rights reserved.