Influence of the electrophoretic deposition route on the microstructure and properties of nano-hydroxyapatite/chitosan coatings on the Ti-13Nb-13Zr alloy

In this work, nanocomposite HA/chitosan coatings were electrophoretically deposited (EPD) on a near-beta Ti-13Nb-13Zr alloy. The influence of the state of the HA particles introduced to the colloidal solution of chitosan (nc-HA-p as a nanopowder and nc-HA-s as nanoparticles suspended in ethanol), as well as the chemical composition of a multi-component HA-chitosan suspension and EPD parameters, on the homogeneity of coatings has been studied. It was established that the pH value and the chemical composition of the suspension have a substantial effect on the electrokinetic properties of suspended HA and chitosan particles. These are also influenced by the deposition kinetics of EPD and the uniformity of as-deposited coatings. The thickness of the nc-HA-p/chitosan and nc-HA-s/chitosan coatings was up to 750 nm and 1.5 mu m, respectively. The nc-HA-s/chitosan coating microstructure consisted of HA nanoparticles, homogeneously embedded in an amorphous chitosan matrix. The nc-HA-p/chitosan coating microstructure was non-homogeneous, composed of HA agglomerates in a chitosan matrix. The presence of thin oxide layer was observed on the coatings/titanium alloy interface. The nc-HA-s/chitosan coating exhibited better adhesion to the titanium alloy substrate than the nc-HA-p/chitosan coating. It was found that the nc-HA-s/chitosan coating improves the electrochemical corrosion resistance of the Ti-13Nb-13Zr alloy in Ringer's solution, as well as its bioactivity and other biological properties. (C) 2017 Elsevier B.V. All rights reserved.