Influence of Ag concentration on microstructure, mechanical properties and cytocompatibility of nanoscale Ti-Ag-N/Ag multilayers

Abstract

Nanoscale Ti-Ag-N/Ag multilayers were successfully deposited on the medical titanium alloy (Ti-6Al-4V) substrates using a multi-target magnetron co-sputtering system. The microstructure, mechanical properties and cytocompatibility were investigated. X-ray diffraction indicated that Ti-Ag-N/Ag multilayers exhibited Ag (111) and (220) textures at a thicker lAg (Ag layer thickness) of 6nm. The intensity of TiN (111) peak became gradually weak with lAg varying from 1.2 to 6nm. A thinner lAg of 1.2nm can block the growth of Ag grains and particles and stimulate the development of TiN (111) orientation, which led Ti-Ag-N/Ag multilayer to a highest hardness (20.5GPa), elastic modulus (260.7GPa) and fracture critical load (27.4mN). X-ray photoelectron spectrometer proved the presence of Ag, TiN, and TiO2 on the surface of Ti-Ag-N/Ag multilayers. Owing to Ag diffusion from Ag layer to TiN layer, Ag was embedded in the surrounding of TiO2 and TiN in Ti-Ag-N layer, which stimulated the photocatalytic activity of TiO2, and then resulted in an improvement in the cytocompatibility of Ti-Ag-N/Ag multilayers with the increased Ag concentration. This work proved that an appropriate Ag concentration can lead to a positive effect on hardness and fracture resistance and also induce negligible adverse effect on the cells growth.