Production and Characterization of the Third-Generation Oxide Nanotubes on Ti-13Zr-13Nb Alloy

Abstract

In the group of vanadium-free titanium alloys used for applications for long-term implants, the Ti-13Zr-13Nb alloy has recently been proposed. The production of a porous layer of oxide nanotubes (ONTs) with a wide range of geometries and lengths on the Ti-13Zr-13Nb alloy surface can increase its osteoinductive properties and enable intelligent drug delivery. This work concerns developing a method of electrochemical modification of the Ti-13Zr-13Nb alloy surface to obtain third-generation ONTs. The effect of the anodizing voltage on the microstructure and thickness of the obtained oxide layers was conducted in 1 M C2H6O2 + 4 wt% NH4F electrolyte in the voltage range 5–35 V for 120 min at room temperature. The obtained third-generation ONTs were characterized using SEM, EDS, SKP, and 2D roughness profiles methods. The preliminary assessment of corrosion resistance carried out in accelerated corrosion tests in the artificial atmosphere showed the high quality of the newly developed ONTs and the slight influence of neutral salt spray on their micromechanical properties.

Influence of Anodizing Conditions on Biotribological and Micromechanical Properties of Ti–13Zr–13Nb Alloy

“…Figure 2 shows SEM images of the microstructure of the self-assembled ONTs obtained on the surface of the Ti–13Zr–13Nb alloy by anodizing under different conditions (see Table 1 ). The detailed mechanism of the electrochemical formation of ONT layers on the surface of the Ti–13Zr–13Nb alloy in electrolytes containing fluoride ions that form water-soluble complexes with titanium, zirconium, and niobium was described in our earlier paper [ 33 , 35 ]. A strong influence of the type of electrolyte on the surface morphology of the obtained ONT layers could be observed.…”

“…With the increase in the ONTs diameter on the Ti–13Zr–13Nb alloy, the number of oxide nanotubes carrying loads in the contact area of the tested surfaces with the diamond indenter decreased. On the other hand, ONTs are able to compensate for the large hardness defect of the biomedical Ti–13Zr–13Nb alloy used for the production of implants, eliminate implant–bone stress mismatch, and minimize “stress shielding” [ 35 ].…”

“…The natural and uneven oxide layer present on titanium and its alloys does not sufficiently protect the implant in the environment of body fluids, therefore the surfaces of these materials are often subjected to modification [ 6 , 7 , 8 , 11 , 12 , 13 , 14 , 29 , 30 ]. One of the currently most popular electrochemical methods of modifying the oxide film to form self-assembled nanotubular oxide structures is anodizing, which allows the production of oxide layers in the form of a matrix of ordered, vertically arranged oxide nanotubes (ONTs) [ 11 , 12 , 13 , 17 , 18 , 19 , 28 , 29 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. The ONTs exhibit numerous unique properties compared to ultrathin oxide films formed spontaneously.…”

“…The porous surface of the ONT layers has a beneficial effect on the osseointegration process and ensures faster tissue growth and stronger bonding of the bone with the implant due to the chemical and morphological similarity of the nanotube oxide layer to the structure of bone tissue. The type of electrolyte in which the anodizing process is carried out has the greatest impact on the microstructure and properties of the ONTs obtained on titanium oxide and its alloys [ 11 , 12 , 13 , 17 , 18 , 19 , 28 , 29 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. The prospect of using ONTs dominated the efforts of researchers at the expense of understanding the mechanical properties of the nanotubular oxide layer [ 21 , 23 , 36 , 41 , 42 , 43 ].…”

“…ONTs used as intelligent drug carriers enable the delivery of poorly water-soluble drugs and prevent the first-pass effect through the liver. ONTs can be produced on a variety of substrates, including three-dimensional, nonplanar, and curved surfaces such as, for example, thin, long surgical wires and bone fixation needles, allowing ONTs to be clinically used on the surface of implants or surgical supports in orthopedics [ 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. However, despite numerous studies on ONTs, relatively little is known about their impact on biotribological wear of modern titanium alloys in a biological environment due to the dominance of research in dry sliding conditions [ 17 , 19 ].…”