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•Chitosan layers with Ag or Au NPs were deposited on Ti6Al7Nb alloy using simple method.•O2/NH3/Ar plasma treatment improved surface roughness and tribology.•Modifications resulted in ...high biocompatibility, eliciting minimal cytotoxicity.•Proper concentrations of Ag and Au ions were released up to 96 h.
Implant-associated infections are the major concern for failure of arthroplasty operations. The functionalisation of implant surface can provide solutions to the problem by either inhibiting the adherence of the bacteria or introducing a contact-killing mechanism. This work is focused on Ti6Al7Nb biomedical alloy modification involving chemical and plasma surface activation, followed by the deposition of chitosan layers enhanced with metal nanoparticles. A benign method using chitosan as an efficient reducing and stabilizing agent was applied to produce Au and Ag nanoparticles in situ with the size of ca. 20 nm and 5 nm, respectively. Piranha solution and O2/NH3/Ar plasma were used as a surface activation method, while Au and AgNPs provide antimicrobial properties, as a viable alternative to the antibiotic-based approach. The surface topography on submicrometre scale of deposited layers was evaluated. Chitosan and chitosan–Ag NPs composite layers showed excellent hydrophilicity, characterised by wetting angles below 13°. Modified alloy showed minimal toxicity towards MG-63 cell line in vitro, acceptable corrosion resistance and release of titanium, aluminium as well as niobium ions from the resulting modified alloys. The chitosan layers were proven to uphold satisfactory Au (over 2.8 mg/dm3) and Ag (over 5.1 mg/dm3) ion dosages up to 96h.
•Ti Grade 2 and Ti6Al7Nb were nitrided at cathode (CP) and plasma potentials (PP).•Layers formed by PP were characterized by lower roughness and also twice as thin.•CP layers were characterized by ...higher wear resistance, but also higher CoF.•Nitriding didn’t affect very good corrosion resistance of Ti6Al7Nb alloy.
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Plasma nitriding of titanium Grade 2 and Ti6Al7Nb titanium alloy at 730 °C was used to produce nitrided surface layers with an outer zone consisting of nanocrystalline titanium nitride - TiN, and a Ti2N zone right above the αTi(N) diffusion area. The paper presents a comparison of structure (TEM, SEM), phase composition (XRD, SAED) surface topography (AFM, optical profilometer), corrosion (potentiodynamic method), tribological properties (‘ball-on-disc’), and adhesion (scratch-test) of TiN + Ti2N + αTi(N) type nitrided surface layers produced on Grade 2 titanium and Ti6Al7Nb titanium alloy using conventional glow-discharge nitriding (so called glow discharge nitriding at the cathode potential) and with the use of an ‘active screen’ (glow discharge nitriding at plasma potential). A reduction of cathodic sputtering in the plasma potential process made it possible to produce surface layers maintaining a high smoothness of the titanium surfaces. Due to the low surface roughness and the high compressive residual stress of the sample after nitriding at plasma potential, ‘ball-on-disc’ test results showed the lowest coefficient of friction and the lowest penetration depth for this layer and very good adhesion of the layer to the substrate – i.e. Ti6Al7Nb titanium alloy. Nitriding of titanium alloy at cathode potential increased the corrosion potential value and slightly decreased corrosion current density. The corrosion current density of the sample nitrided at plasma potential was similar to initial state Ti6Al7Nb titanium alloy. The nitriding process type (cathode potential or plasma potential) used to produce TiN + Ti2N + αTi(N) surface layers on Ti6Al7Nb titanium alloy has an influence on the microstructure of the layer, its residual stress, in particular its TiN outer titanium nitride zone, its thickness, and on its properties such as wear and corrosion resistance.
This investigation addresses a novel additively manufactured circular honeycomb sample of the titanium alloy Ti6Al7Nb which exhibits superior mechanical properties compared to hexagonal honeycomb ...samples. Compared to other lattice structures/cellular solids of Ti-based alloys, the circular honeycomb sample provides an optimum combination of strength and fracture strain. During compression testing, the circular honeycomb exhibits a wide stress-strain curve with higher tensile stress and elongation compared to hexagonal honeycomb samples. The failure of the circular honeycomb sample occurs layer-by-layer, so the whole sample fails not before the fracture of all single layers of the cells in the circular honeycomb leading to higher elongations. In this regard, the hexagonal honeycomb sample fails by shear of struts oriented at 45° to the loading axis. The area near the fracture region shows a fine acicular αʹ microstructure. Electron Backscattered Diffraction (EBSD) data analysis reveals coarse prior β grains in the surrounding microstructure. So, the circular honeycomb sample is superior to the hexagonal honeycomb sample concerning impact and energy absorption applications.
With increased demands of artificial bone-like tissue specified orthopedic and dental replacement, medical grade of titanium alloys such as Ti6Al7Nb implants (Ti67IMP) have been considered due to ...their specific density and corrosion resistance with relatively lower moduli than other metals which leads to a better compliance with the modulus of bone. However, without any external force and overloading, the failure might be happen after implantation which need to repeat the surgery step. Thus, in order to minimize the risk of implant loosing and improve biocompatibility, surface modification is required to facilitate the stability of implant trough healing process. The development of nanotubular bioceramics can improve the implants’ surface properties and provide rapid osseointegration. It is notified that the considered nanobiomaterials with controlled morphology can effect on antibacterial and drug delivery activities of implants. Herein, mixed oxide nanotubes (titania-niobia-alumina) was fabricated on Ti67IMP using PVD magnetron sputtering and subsequent electrochemical anodization. Initially, a well-adherent niobium (Nb) film was PVD sputtered under optimized coating conditions, then nanotubular arrays were grown on Nb/Ti67IMP surface after subsequent anodization and thermal treatment. In the final stage, the as-prepared graphene oxide (GO) nanosheet was transparently loaded on anodic nanotubes to reinforce ternary ceramic film. The microstructural features, wettability behavior and in-vitro bioactivity of the nanostructured coating were examined. Based on in-vitro bioassay analysis, a thick apatite layer was formed on the implant surface after primary days of immersion in simulated body fluid (SBF).
Micro-arc oxidation is a simple, single-step surface modification method used to produce coatings on titanium alloys for biomedical applications. The formation and properties of coatings can be ...widely controlled by adjusting process parameters such as applied voltage, frequency, processing time and electrolyte composition. In the present study, three different electrolytes were used to obtain well adherent, rough, porous, hydroxyapatite containing, oxide coating on Ti6Al7Nb alloy. Coatings were investigated in terms of their microstructure, chemical composition, roughness, hardness, adhesion strength and biocompatibility. Among the coatings produced in different electrolytes, one of them exhibited both good mechanical properties and bioactivity, while containing crystalline hydroxyapatite on the surface, whereas the other two coatings were mostly amorphous. Thereby, we have proposed an efficient electrolyte containing calcium and phosphorous species in order to modify titanium based alloys to improve their biocompatibility and osseointegration. Such properties are achieved by formation of a rough outer layer with open pores, providing high surface area for cells to adhere, proliferate and migrate into the coating, promoting firm anchorage of the coated implant in the bone.
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•Medical grade Ti6Al7Nb alloy implants manufactured by Selective Laser Melting (SLM).•Heat treatment, chemical treatment, and impregnation with bioactive materials.•Treatments effect on bioactivity ...of SLM derived implants tested in vitro.•XRD, SEM/EDX, XPS analyses.
The work aims to characterize the structure and to evaluate in vitro the effect of different surface treatments on the bioactivity of medical grade Ti6Al7Nb alloy implants manufactured by selective laser melting. In order to improve the bioactivity of these samples, they were subjected to heat treatment, chemical treatment, and impregnation with bioactive materials. To evaluate the apatite forming ability, the samples were immersed in simulated body fluid solution) and characterized before and after immersion by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The composition and the texture of the surfaces after the applied treatments have a selective effect on apatite layer development on the surface of samples.
Plasma nitriding of titanium alloys is capable of effective surface hardening at temperatures significantly lower than gas nitriding, but at a cost of much stronger surface roughening. Especially ...interesting are treatments performed at the lower end of the temperature window used in such cases, as they are least damaging to highly polished parts. Therefore identifying the most characteristic defects is of high importance. The present work was aimed at identifying the nature of pin-point bumps formed at the glow discharged plasma nitrided Ti-6Al-7Nb alloy using plan-view scanning and cross-section transmission electron microscopy methods. It helped to establish that these main surface defects developed at the treated surface are (Ti,Al)O2 nano-whiskers of diameter from 20 nm to 40 nm, and length up to several hundreds of nanometers. The performed investigation confirmed that the surface imperfection introduced by plasma nitriding at the specified range should be of minor consequences to the mechanical properties of the treated material.
Unlike conventional manufacturing techniques, additive manufacturing (AM) can form objects of complex shape and geometry in an almost unrestricted manner. AM's advantages include higher control of ...local process parameters and a possibility to use two or more various materials during manufacture. In this work, we applied one of AM technologies, selective laser melting, using Ti6Al7Nb alloy to produce biomedical functional structures (BFS) in the form of bone implants. Five types of BFS structures (A1, A2, A3, B, C) were manufactured for the research. The aim of this study was to investigate such technological aspects as architecture, manufacturing methods, process parameters, surface modification, and to compare them with such functional properties such as accuracy, mechanical, and biological in manufactured implants. Initial in vitro studies were performed using osteoblast cell line hFOB 1.19 (ATCC CRL-11372) (American Type Culture Collection). The results of the presented study confirm high applicative potential of AM to produce bone implants of high accuracy and geometric complexity, displaying desired mechanical properties. The experimental tests, as well as geometrical accuracy analysis, showed that the square shaped (A3) BFS structures were characterized by the lowest deviation range and smallestanisotropy of mechanical properties. Moreover, cell culture experiments performed in this study proved that the designed and obtained implant's internal porosity (A3) enhances the growth of bone cells (osteoblasts) and can obtain predesigned biomechanical characteristics comparable to those of the bone tissue.
The tribology behaviors of Ti6Al7Nb, its alloy with N-ion implantation, and its alloy with diamond-like carbon (DLC) coating were investigated in artificial saliva. Fretting wear tests of untreated, ...N-ion implanted and DLC coated Ti6Al7Nb alloys plate against a Si3N4 ball were carried out on a reciprocating sliding fretting wear test rig. Based on the analysis of X-ray diffraction, Raman spectroscopy, 3-D profiler, SEM morphologies and frictional kinetics behavior analysis, the damage behavior of surface modification layer was discussed in detail. The results indicated that the fretting wear behavior of Ti6Al7Nb alloy with N-ion implantation was increased with the dose increase of the implanted nitrogen ions. Moreover, the DLC-coated Ti6Al7Nb alloy with low ion implantation could improve the fretting wear behavior greatly. In addition, the Ti6Al7Nb with DLC coating had better corrosion resistance due to the special compact structure. All results suggested that the Ti6Al7Nb with DLC coating had better wear resistance than that with N-ion implantation in artificial saliva.
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