A novel synthesis method of carbide-derived carbon (CDC) in open air for hip implants

Abstract

The inferior tribocorrosion behavior of commonly used biomedical alloys has led to the early failure of total hip replacements (THRs) and serious complications. Our previous results have shown that carbide-derived carbon (CDC) produced by direct chlorination can provide excellent protection to Ti6Al4V and has a high durability.In this study, a novel method has been developed to synthesize CDC on Ti6Al4V substrates by electrolysis from LiCl-KCl with a low melting point. Compared to previous preparation processes, this newly developed approach eliminates the exposure to chlorine gas and the requirement of the inert gas environment, which makes the synthesis process more controllable and the CDC layer more uniform. X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) techniques were utilized to characterize the products. Based on the characterization results, the produced CDC has a porous structure which may contain nanocrystalline graphite (NCG) and amorphous carbon (a-C). The theoretical thickness of the sample is estimated by a calculation which is approximately 1.44 μm. In addition, the performance of the new layer was tested in a tribocorrosion hip simulator. A system has a pin on ball contact and immersed in bovine calf serum of 30 g/L protein concentration, with a pH of 7.6 and a temperature of 37 °C. We applied a normal force of 16 N and ran the test for 3600 cycles with 1 Hz. According to the recordings of normal and tangential forces, the evolution of friction coefficient is deducted and reported in the results.The findings have shown that the CDC samples prepared by electrolysis method exhibit smaller friction coefficient (approximately 0.12) and potential drop (less than 0.1 V compared to 1.1 V for substrate). Therefore, it is promising that CDC prepared by the novel electrolysis approach can protect Ti6Al4V substrates from the tribocorrosive damages.