The microstructure, bio-tribological properties, and biocompatibility of titanium surfaces with graded zirconium incorporation in amorphous carbon bioceramic composite films

Abstract

One type of carbon-based bioceramic composite film, zirconium (Zr) incorporated amorphous carbon (Zr/a-C) gradient multilayer films (GMFs), is deposited on titanium (Ti) alloys by magnetron sputtering to attain superior biocompatibility and mechanical and bio-tribological properties. The morphologies and structure of Zr/a-C GMFs were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). XRD and SEM and TEM analysis confirmed the gradient multilayer nature of the film, and the presence of nanostructured fcc-ZrC at the Zr/C layer interface for Zr content of 6.3 at.%. XPS analyses confirmed elevated sp2 bond content as a result of incorporating the Zr interlayer in the a-C matrix. The tribological properties of Zr/a-C GMFs were defined using a tribometer with a fetal bovine serum (FBS) solution, in which all Zr/a-C GMFs exhibited improved wear resistance, compared to the pure a-C film and Ti alloy. Additionally, Zr/a-C GMFs exhibited the lowest friction coefficient (COF) at 0.114, and a wear rate of 1.47–1.56 × 10−6 mm3/Nm, compared to pure a-C films and Ti alloy. Phase composition and the superior mechanical properties of GMFs were determined as crucial factors contributing to the enhanced wear resistance and low COF in Zr/a-C GMFs. Furthermore, osteoblast cell viability and proliferation on GMF films were tested in cultures, and results indicated that Zr/a-C GMFs have better biocompatibility, compared to Ti alloy. Cell adhesion experiments also demonstrated the excellent biocompatibility and functional reliability of composite biofilms for potential application in bone implants.