Passivation of carbon fiber by diamond deposition

Diamond deposition on a highly graphitic carbon fiber substrate was performed using microwave plasma enhanced chemical vapor deposition. Carbon fibers were heat treated at different temperatures and polished by diamond dust for various periods of time. During the deposition, etching of fiber and nucleation of diamond occur simultaneously and compete kinetically with each other. Polishing was found to be critical for diamond nucleation, while the heat treatment temperature of the carbon fiber precursor affected both etching of fiber and nucleation of diamond. Raman spectra of the deposits show the characteristics of diamond as well as graphitic inclusions. Lower methane concentration and/or higher temperature resulted in deposits with less graphitic inclusion. An explanation of diamond nucleation on these fibers is suggested.