Graphene Oxide/Silver Nanoparticle Coating Produced by Electrophoretic Deposition Improved the Mechanical and Tribological Properties of NiTi Alloy for Biomedical Applications

Abstract

The aim of this study was to evaluate the mechanical and tribological properties of graphene oxide/silver nanoparticle (GO/AgNP) coated medical grade nickel-titanium (NiTi) alloy. The alloy substrates were coated using electrophoretic deposition at 30 V for 1, 5, and 10 min and were characterized by SEM, Raman spectroscopy, EDS, and surface profilometer. Mechanical and tribological tests were performed for hardness, Young's modulus, and friction coefficient. The data were analyzed using the Kruskal-Wallis test at a significance level of 0.05 to compare the coatings' roughness, thickness, friction coefficient, and hardness at the different coating times. The GO/AgNP coatings were confirmed with Raman spectroscopy, which demonstrated the presence of D bands and G bands at ∼1300 cm^-1 and ∼1600 cm^-1. The intensity ratios of the D and G bands (I_D/I_G) were 0.838, 0.836, and 0.837 in the 1, 5, and 10 min coated groups, respectively. The coating thickness ranged from 0.46-1.34 μm and the mean surface roughness (Ra) ranged from 50.72-69.93 nm. Increasing the coating time from 1-10 min increased the roughness, thickness, and Young's modulus of surface coating. The friction coefficients of the coated NiTi alloy were significantly lower compared with that of the uncoated NiTi allloy (p < 0.001). The GO/AgNP nanocomposite coated NiTi alloy demonstrated improved mechanical strength and a reduced friction coefficient that would be more favorable for biomedical applications.