| During isothermal anneal of diamond-like carbon (DLC) films in vacuum in the temperature range of 560 to 1060K, gases consisting of hydrogen and hydrocarbons, mainly methane, were produced and identified by a line-of-sight technique with a residual gas analyzer. The evolution of gases was attributed to the dissociation of sp{dollar}sp3{dollar} C-H bonds at all temperatures, but at temperatures above 860K, both sp{dollar}sp2{dollar} and sp{dollar}sp3{dollar} C-H bonds contributed to the formation of the gaseous species. Experimental results were interpreted by invoking a two-phase structural model of DLC. The first phase or the matrix mainly consisted of a random network of fourfold carbons passivated by double or/and triple hydrogens. The other graphitic phase accounted for less than 20% of the volume of the film.; The wear rates and the friction coefficients of DLC films sliding against a silicon nitride ball were measured in a pin-on-disk tribometer in argon and air of varying relative humidity. The wear rate of the ball and the DLC film were determined by profilometry and by optical microscopy. The friction coefficient was independent of film stress. The wear rate increased by less than one order of magnitude as the stress increased from 1.3 to 2.6 GPa. In 100% humid air, debonding was observed between the DLC film and the substrate during sliding. In 50% relative humidity, the measured wear rates of the ball and the DLC film were of the order of 10{dollar}sp{lcub}-8{rcub}{dollar} and 10{dollar}sp{lcub}-7{rcub}{dollar} mm{dollar}sp3{dollar}/Nm under a 1 kg load and for a sliding distance of 1000m. In dry argon, air and 100% humid air, the wear rate of the ball was not detectable but those of the films were 10{dollar}sp{lcub}-9{rcub}{dollar}, 10{dollar}sp{lcub}-9{rcub}{dollar} and 10{dollar}sp{lcub}-8{rcub}{dollar} mm{dollar}sp3{dollar}/Nm, respectively. The measured friction coefficients were 0.06 in dry argon, 0.08 in 50% humid air and 0.09 in 100% humid argon and 0.2 in the other conditions. In dry argon, the contact area of the ball was covered with a material transferred from the DLC film during sliding. The low friction coefficient and the low wear rate measured in dry argon are attributed to this transferred film. (Abstract shortened with permission of author.)... |
