Carbon-based coatings exhibit many attractive properties that make them good candidates for a wide range of engineering applications. Tribological studies of the films have revealed a close correlation between the chemistry of the hydrocarbon source gases and the coefficients of friction and wear rates of the diamond-like carbon films. Those films grown in source gases with higher hydrogen-to-carbon ratios had much lower coefficients of friction and wear rates than did films derived from source gases with lower hydrogen-to-carbon ratios. The mechanism for this low friction is as yet not properly understood. Ongoing structural characterization of the films at Argonne National Laboratory is gradually revealing this mechanism. Recent studies have included x-ray photoelectron spectroscopy (XPS), near edge x-ray absorption fine structure (NEXAFS) and x-ray reflectivity (XRR). XPS showed ∼10% oxygen at the surface, which was largely removed after a 1 minute sputter; NEXAFS showed a high sp2:sp3 ratio implying a highly graphitic material; and XRR has given a comprehensive depth profile, with three layers of increasing density as the substrate was approached. The paper discusses the results and correlation with previous friction measurements.

The objective of this work is to identify synthetic pathways for materials useful in the effective repair of the skeletal system. Ideally a universal artificial bone would be identified that can function as a cementitious, pseudoplastic, or structural material. The cementitious form would be very important for bone adhesives that repair bone fractures and restore bone defects. The pseudoplastic form would aid in the in situ reconstruction of anatomical defects and the structural material could be used to prefabricate prostheses. It is critical of course for all these forms of the artificial bone to have strongly regenerative properties so that as implants they would integrate microscopically with natural bone.