Comparison of Mechanical and Barrier Properties of Al2O3/TiO2/ZrO2 Layers in Oxide–Hydroxyapatite Sandwich Composite Coatings Deposited by Sol–Gel Method on Ti6Al7Nb Alloy

Abstract

In this study, coatings of different oxides (TiO2, Al2O3, ZrO2) and hydroxyapatite (HAp) as well as sandwich composite hydroxyapatite with an oxides sublayer (oxide+HAp) were deposited on Ti6Al7Nb alloy using the sol–gel dip-coating method. The coatings were characterized in terms of morphology (optical microscope), surface topography (AFM), thickness (ellipsometry), and crystal structure (XRD/GIXRD). The mechanical properties of the coatings—hardness, Young’s modulus, and adhesion to the substrate—were examined using nanoindentation and scratch tests. The barrier properties of the coatings against the migration of aluminum ions were examined by measuring their concentration after soaking in Hank’s balanced salt solution (HBSS) with the use of optical emission spectrometry of inductively coupled plasma (ICPOES). It was found that all the oxide and HAp coatings reduced the permeation of Al ions from the Ti6Al7Nb alloy substrate. The best features revealed an Al2O3 layer that had excellent barrier properties and the best adhesion to the substrate. Al2O3 as a sublayer significantly improved the properties of the sandwich composite HAp coating.

A review: Recent advances in sol‐gel‐derived hydroxyapatite nanocoatings for clinical applications

“…Coatings of different oxides such as TiO 2 , Al 2 O 3 , ZrO 2 , and HAp in addition to sandwich composite HAp with an oxide sublayer were deposited on Ti6Al7Nb alloy using the dip‐coating method. The study claimed that an Al 2 O 3 sublayer improved the adhesion of the sandwich composite Al 2 O 3 + HAp coating and at the same time had excellent barrier properties 46 …”

“…The study claimed that an Al 2 O 3 sublayer improved the adhesion of the sandwich composite Al 2 O 3 + HAp coating and at the same time had excellent barrier properties. 46…”

The Microstructure, Mechanical and Friction-Wear Properties of (TiBx/TiSiyCz)x3 Multilayer Deposited by PLD on Steel

“…Low hardness values measured in this range are related to the presence of titanium and boron oxides (and hydrooxides), which are formed spontaneously on the surface of the TiB x layer of the coating after the sample removing from the vacuum chamber. The oxides layer is relatively soft (HV 1.5 GPa, for α-B 2 O 3 [30], 1-5 GPa for TiO 2 [31]) and its thickness is relatively low, as the impact of the layer on the measured hardness value decreases rapidly with increasing load. Maximum values of hardness and Young modulus were determined for loads in the range 5-20 mN and with the indentation depth of 50-150 nm.…”