Influence of Two-Stage Anodization on Properties of the Oxide Coatings on the Ti–13Nb–13Zr Alloy

Electrophoretically deposited titanium and its alloys in biomedical engineering: Recent progress and remaining challenges

Over the past decade, titanium implants have gained popularity as the number of performed implantation operations has significantly increased. There are a number of methods for modifying the surface of biomaterials, which are aimed at extending the life of titanium implants. The developments in this field in recent years have required a comprehensive discussion of all the properties of electrophoretically deposited coatings on titanium and its alloys, taking into account their bioactivity. The development that took place in this field in recent years required a comprehensive discussion of all the properties of coatings electrophoretically deposited on titanium and its alloys, with particular emphasis on their bioactivity. Herein, we attempt to assess the influence of the electrophoretic deposition (EPD) process parameters on these coatings' biological and mechanical properties. Particular attention has been addressed to the in-vitro and in-vivo studies conducted hitherto. We have seen an increased interest in using titanium alloys without the addition of toxic compounds and gaps in the EPD field such as the uncommon endeavors to develop a "Design of experiments" approach as well as the lack of assessment of the surface free energy and detailed topography of electrophoretically deposited coatings. The exact correlation of coating properties with EPD process parameters still seems explicitly not understood, necessitating more future investigations. Ipso facto, the exact mechanism of particle agglomeration and Hamaker's law need to be fathomable.

In Vitro Bioelectrochemical Properties of Second-Generation Oxide Nanotubes on Ti-13Zr-13Nb Biomedical Alloy

Surface charge and in vitro corrosion resistance are some of the key parameters characterizing biomaterials in the interaction of the implant with the biological environment. Hence, this work investigates the in vitro bioelectrochemical behavior of newly developed oxide nanotubes (ONTs) layers of second-generation (2G) on a Ti-13Zr-13Nb alloy. The 2G ONTs were produced by anodization in 1 M (NH₄)₂SO₄ solution with 2 wt.% of NH₄F. The physical and chemical properties of the obtained bamboo-inspired 2G ONTs were characterized using scanning electron microscopy with field emission and energy dispersive spectroscopy. Zeta potential measurements for the examined materials were carried out using an electrokinetic analyzer in aqueous electrolytes of potassium chloride, phosphate-buffered saline and artificial blood. It was found that the electrolyte type and the ionic strength affect the bioelectrochemical properties of 2G ONTs layers. Open circuit potential and anodic polarization curve results proved the influence of anodizing on the improvement of in vitro corrosion resistance of the Ti-13Zr-13Nb alloy in PBS solution. The anodizing conditions used can be proposed for the production of long-term implants, which are not susceptible to pitting corrosion up to 9.4 V.

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

The biomedical Ti-13Zr-13Nb bi-phase (α + β) alloy for long-term applications in implantology has recently been developed. The porous oxide nanotubes' (ONTs) layers of various geometries and lengths on the Ti-13Zr-13Nb alloy surface can be produced by anodizing to improve osseointegration. This work was aimed at how anodizing conditions determinatine the micromechanical and biotribological properties of the Ti-13Zr-13Nb alloy. First-generation (1G), second-generation (2G), and third-generation (3G) ONT layers were produced on the Ti-13Zr-13Nb alloy surface by anodizing. The microstructure was characterized using SEM. Micromechanical properties were investigated by the Vickers microhardness test under variable loads. Biotribological properties were examined in Ringer's solution in a reciprocating motion in the ball-on-flat system. The 2D roughness profiles method was used to assess the wear tracks of the tested materials. Wear scars' analysis of the ZrO₂ ball was performed using optical microscopy. It was found that the composition of the electrolyte with the presence of fluoride ions was an essential factor influencing the micromechanical and biotribological properties of the obtained ONT layers. The three-body abrasion wear mechanism was proposed to explain the biotribological wear in Ringer's solution for the Ti-13Zr-13Nb alloy before and after anodizing.

Enhanced Corrosion Resistance and Local Therapy from Nano-Engineered Titanium Dental Implants

Titanium is the ideal material for fabricating dental implants with favorable biocompatibility and biomechanics. However, the chemical corrosions arising from interaction with the surrounding tissues and fluids in oral cavity can challenge the integrity of Ti implants and leach Ti ions/nanoparticles, thereby causing cytotoxicity. Various nanoscale surface modifications have been performed to augment the chemical and electrochemical stability of Ti-based dental implants, and this review discusses and details these advances. For instance, depositing nanowires/nanoparticles via alkali-heat treatment and plasma spraying results in the fabrication of a nanostructured layer to reduce chemical corrosion. Further, refining the grain size to nanoscale could enhance Ti implants' mechanical and chemical stability by alleviating the internal strain and establishing a uniform TiO₂ layer. More recently, electrochemical anodization (EA) has emerged as a promising method to fabricate controlled TiO₂ nanostructures on Ti dental implants. These anodized implants enhance Ti implants' corrosion resistance and bioactivity. A particular focus of this review is to highlight critical advances in anodized Ti implants with nanotubes/nanopores for local drug delivery of potent therapeutics to augment osseo- and soft-tissue integration. This review aims to improve the understanding of novel nano-engineered Ti dental implant modifications, focusing on anodized nanostructures to fabricate the next generation of therapeutic and corrosion-resistant dental implants. The review explores the latest developments, clinical translation challenges, and future directions to assist in developing the next generation of dental implants that will survive long-term in the complex corrosive oral microenvironment.

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

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.

Surface and Tribological Properties of Oxide Films on Aluminium Alloy through Fly-Ash Reinforcement

Hard anodizing has proven to be a helpful surface treatment for aluminium alloy and typically accompanied by the growth of a porous and highly flawed oxide layer. The presence of pores on the oxide surface can be taken as an advantage in improving the surface properties. Fly-ash particles are high in SiO2 and Al2O3 content and can be utilized as inexpensive strengthening particles, which can increase the wear resistance and microhardness of composite material. It was noticed that limited research had been carried out in utilizing fly-ash as reinforcement on composite oxide coating as a wear resistance candidate. Thus, this study focused on reinforcing fly-ash on oxide coating and investigating its tribological performance. The composite oxide coating was grown on AA2017 aluminium alloy through anodizing process. To understand the effect of anodizing time and fly-ash content, the parameters were varied from 5–60 min and 0–50 g/L, respectively. The findings suggested that 60 min of anodizing time provides the highest thickness and surface roughness at 35 µm and 6.5 µm, respectively. Interestingly, composite oxide coating with 50 g/L fly-ash provides the highest coating thickness but has the lowest roughness at 52 μm and 8.2 μm, respectively. The composite oxide coatings are observed to reduce friction only for a limited time, despite their potential in significantly reducing the wear rate. The wear mechanism observed was adhesion, micro-crack, and delamination. The findings of this study are believed to provide insight on the potential of fly-ash to be a reinforcement for wear-reduction materials.

Production and Properties of the Porous Layer Obtained by the Electrochemical Method on the Surface of Austenitic Steel

The growing demand for implants has seen increasing interest in the introduction of new technologies and surface modification methods of metal biomaterials. This research aimed to produce and characterize a porous layer grown on austenitic stainless steel 316L, obtained via the anodization process near the micro-arc oxidation, i.e., low voltage micro-arc oxidation (LVMAO). The discussed layer significantly influences the properties of metallic biomedical materials. The surface topography, layer thickness, surface roughness, pore diameter, elemental composition, crystal structure, and surface wettability were assessed for all anodized layers, together with the resultant corrosion resistance. Attention was paid to the influence of the process parameters that affect the specification of the produced layer. The obtained results showed surface development and different sized pores in the modified layers, as well as an increase in corrosion resistance in the Ringer’s solution.

Influence of Electrolyte Temperature on Morphology and Properties of Composite Anodic Film on Titanium Alloy Ti-10V-2Fe-3Al

In this study, we introduced a novel environmentally-friendly electrolyte consisting of polytetrafluoroethylene (PTFE) nanoparticles and malic acid solution to fabricate composite anodic film on Ti-10V-2Fe-3Al alloy at different electrolyte temperatures. The morphology revealed that the PTFE nanoparticles were successfully incorporated into composite anodic films and embedded preferentially in the pores and cracks. Their performances (wear, corrosion and hydrophobicity) were evaluated via electrochemical tests, ball on disc tests, and a contact angle (CA) meter. Compared to the substrate of titanium alloy Ti-10V-2Fe-3Al, the composite anodic films exhibited the low wear rates, high corrosion resistance and good hydrophobicity. However, the microstructure and morphology of the films were affected by the electrolyte temperature. As a result, their performances were changed greatly as a function of the temperature and the film fabricated at 20 °C exhibited better performances (CA = 131.95, icorr = 6.75 × 10−8 A·cm−2, friction coefficient = 0.14) than those at other electrolyte temperatures. In addition, the corresponding lubrication mechanism of the composite anodic films was discussed.