Development of biocompatible and self lubricating nanocomposite films.

摘要

ZrN-Ag and CrAlN-Ag composite films have been deposited by an unbalanced magnetron sputtering to study their biocompatibility and wear properties. ZrN-Ag is expected to find commercial application in biomedical implants and CrAlN-Ag as high temperature protective coatings for air and space application. The coatings were deposited on (111) silicon wafers and stainless steel (304) at different temperatures (R.T., 200°C, 300°C) with bias voltage in the -70 to -130 Volt range. The elemental concentration of the films was regulated by controlling the power applied to the target and by adjusting N2 flow rate. The deposited films were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy(XPS), Auger electron spectroscopy, Rutherford back scattering, spectroscopic ellipsometry, nanoindentation, and ball on disc tribotester. The films consisted of Ag nanocrystals embedded in a ZrN or CrAlN matrix with crystallite size that decreases with increasing silver content. Chemical and phase composition was determined by XPS measurements. Optical constants were measured by using spectroscopic ellipsometry. The mechanical properties of the coating were evaluated using nanohardness testing and were found to depend on composition and deposition parameters. Ball on disc friction test was performed under room temperature. Friction and wear were lower with higher Ag contents. ZrN-Ag film with the largest Ag content showed best biocompatibility for the biomedical implants.