Surface nitriding of graphite substrate by plasma focus device towards synthesis of carbon nitride coating

Abstract

Circular graphite substrates have been nitrided in a plasma focus device. Nitrogen ions consisting of 100-ns pulses emanating from a Mather type plasma focus device were allowed to hit the surfaces of graphite substrates for 20 and 30 times (shots) to produce nitrided coatings. Microstructural characterization of the coatings carried out by XRD determined the d values of the nitride compound thus produced and four d values matched with those predicted by Cohen and co-workers and Wang et al. [Phys. Rev. B32 (1985) 7988; Science 245 (1989) 841; Phys. Rev. B41 (1990) 10727; Phys. Rev. B58 (1998) 11890] for carbon nitride. SEM and optical microscopic studies of the nitrided graphite surface reveal a rounded and island like morphology of the carbon nitride grains. Comparison of XPS results of the unnitrided and nitrided graphite shows the evidence for carbon-nitrogen bonding. IR spectra attribute the 1274.4 cm(-1) absorption peak to C3N4 (sp(3)). The clear improvements observed in microhardness values point to the growth of a hard carbon nitride phase. (C) 2001 Elsevier Science B.V. All rights reserved.