AC impedance behavior of silicon-hydroxyapatite doped film on the Ti–35Nb–xZr alloy by EB-PVD method

Abstract

The AC impedance behavior of silicon-hydroxyapatite doped film on the Ti–35Nb–xZr alloy by EB-PVD method was investigated in this study. The Si–HA composite coating layers were formed from Si of 0.8wt.% with HA by EB-PVD method. The surface characteristics were analyzed by FE-SEM, EDS, and XRD. The AC impedance test was performed the frequency range from 10mHz to 100kHz in 0.9wt.% NaCl solution at 36.5±1°C.The Ti–35Nb–10Zr alloy shows an equiaxed β-phase microstructure. HA‐coated surface of Ti–35Nb–10Zr alloy showed the small droplets and the chemical composition of HA‐coated surface consisted of Ca, P, Ti, Nb, and Zr with Ca/P ratio of 1.67. The surface of Si–HA‐coated Ti–35Nb–10Zr alloy showed rougher morphologies after heat treatment than as-surface with the coated thickness around 100nm. The Si–HA‐coated surface showed hydroxyapatite, calcium phosphate silicate, and β-Ti peaks. From the current density–time curves at constant 300mV, the current density of HA and Si–HA‐coated surface decreased with time, Especially, Si–HA‐coated surface showed the lower than HA‐coated and non-coated surfaces with time due stable film formation. From these results, Si–HA layer showed the high polarization resistance compared to other samples. Si–HA had a lager semicircle of Nyquist curve and increased in the order of non-coating, HA coating, and Si–HA coating. Si–HA‐coated surface showed a good corrosion resistance than HA single‐coated and non-coated surface.