Development of Novel Low-Modulus β-Type Ga-/Cu-Bearing Ti–Nb Alloys for Antibacterial Bone Implant Applications

Commercially available titanium (Ti) alloys, such as Ti–6Al–4V and c.p. Ti, even though established in clinical use as load-bearing bone implant materials in orthopedics and dentistry, possess significant drawbacks that may lead to implant failure: i) presence of alloying elements with harmful health effects, ii) high Young’s modulus (E > 100 GPa) compared to human cortical bone (Ebone = 10 – 30 GPa), and iii) lack of antibacterial activity against multidrug-resistant bacteria, which may lead to implant-associated infections. To overcome the first two drawbacks, a new generation of biocompatible metastable β-type Ti alloys has been developed, in particular β-type Ti–Nb alloys, which are versatile candidates due to their low Young’s modulus, high strength-to-weight ratio and improved corrosion resistance. The present work aims to tackle all three aforementioned issues by developing novel β-type Ti–45Nb-based alloys with potential intrinsic antibacterial activity by adding antibacterial gallium (Ga) and copper (Cu) in minor amounts (up to 8 wt.%) via metallurgical route. Nine alloys with the following chemical compositions: (100-x)(Ti–45Nb)–xGa, (100-x)(Ti–45Nb)–xCu (where x = 2, 4, 6, 8 wt.%), and 96(Ti–45Nb)–2Ga–2Cu, based on alloy design approaches, were produced by controlled casting and homogenization treatment. The effect of antibacterial alloying additions on phase constitution, mechanical characteristics, corrosion, and tribocorrosion response in a simulated physiological environment has been investigated. All nine alloys in the homogenized state display a single-phase β (BCC) phase microstructure, whose lattice parameter is proved to be sensitive to Ga and Cu content, with an almost linear contraction. The mechanical characteristics are strongly influenced by Ga and Cu addition, with a general strengthening effect mainly attributed to substitutional solid solution strengthening, and to grain boundary strengthening in case of Ga. Deformation behavior indicates high mechanical stability of the β phase, suggesting dislocation slip as dominant deformation mechanism. The results demonstrate that strategic alloy design is an effective method to significantly increase strength without adversely affecting the Young’s modulus, which remains in the range of good biomechanical compatibility (E = 64 – 104 GPa). Evaluation of the corrosion response and metal ion release in simulated physiological environment demonstrates the high corrosion resistance of the nine alloys, whereas tribocorrosion wear resistance increases upon Ga addition. Further thermal (aging) treatments, carried out on a specific Cu-containing alloy, proved the feasibility of tailoring enhanced mechanical, chemical and potentially antibacterial properties by thermally-induced precipitation of Ti₂Cu intermetallic compound. These novel developed alloys are considered to be promising candidates for biomedical bone implant applications

Novel low modulus beta-type Ti–Nb alloys by gallium and copper minor additions for antibacterial implant applications

This study aims to develop novel low-modulus, corrosion-resistant Ti-based alloys with enhanced antimicrobial properties for bone-related implant applications. Novel β-type (Ti–45Nb)-based alloys with minor additions of the antibacterial elements Ga and/or Cu (up to 4 wt.%) were produced by a two-step casting process followed by homogenization treatment. Three nominal compositions (Ti–45Nb)96-4 Ga, (Ti–45Nb)96–4Cu and (Ti–45Nb)96-2 Ga–2Cu (wt.%) were prepared based on alloy design approach using [Mo]eq and electron per atom (e/a) ratio. The influence of Ga and/or Cu addition on the phase constitution, mechanical response and corrosion characteristics in simulated body fluids (PBS, 37.5 °C) has been investigated. X-ray diffraction studies displayed a single β phase structure for all alloys, with an observed lattice contraction evidenced by the reduction of lattice parameters during Rietveld analysis. Homogenous equiaxed microstructures with grain sizes ranging from 55 μm up to 323 μm were observed for (Ti–45Nb)96-4 Ga, (Ti–45Nb)96-2 Ga–2Cu and (Ti–45Nb)96–4Cu alloys. The alloys displayed excellent plasticity with no cracking, or fracturing during compression tests. Their tensile strength, Young's modulus, maximum tensile strain and elastic energy were measured in the ranges of 544–681 MPa, 73–78 GPa, 17–28% and 2.5–3.7 MJ/m3, in the order (Ti–45Nb)96-4 Ga > (Ti–45Nb)96-2 Ga–2Cu > (Ti–45Nb)96–4Cu. In addition, it has been observed that micro-alloying Ti–Nb alloy with Ga and/or Cu posed no deleterious effect on the corrosion resistance in simulated body fluid conditions. The improvement in strength of the developed alloys has been discussed based on grain boundary and solid-solution strengthening, whereas the improved plasticity is attributed to work hardening

Designing Gallium-Containing Hydroxyapatite Coatings on Low Modulus Beta Ti-45Nb Alloy

Low-modulus β-type Ti-45Nb alloy is a promising implant material due to its good mechanical biocompatibility, non-toxicity, and outstanding corrosion resistance. Its excellent chemical stability brings new challenges to chemical surface modification treatments, which are indispensable for both osteogenesis and antibacterial performance. Coatings containing metal ions as anti-microbial agents can be an effective way to reduce implant-associated infections caused by bacterial biofilm. Gallium ion (Ga3+) has the potential to reduce bacterial viability and biofilm formation on implant surfaces. In this study, a novel two-step process has been proposed for Ga3+ incorporation in hydroxyapatite (HAP) to develop bioactive and antibacterial surfaces on Ti-45Nb alloy. For the generation of bioactive surface states, HAP electrodeposition was conducted, followed by wet chemical immersion treatments in gallium nitrate (1 mM). Different buffers such as phosphate, sodium bicarbonate, ammonium acetate, and citrate were added to the solution to maintain a pH value in the range of 6.5–6.9. Coating morphology and HAP phases were retained after treatment with gallium nitrate, and Ga3+ ion presence on the surface up to 1 wt.% was confirmed. Combining Ga and HAP shows great promise to enable the local delivery of Ga3+ ions and consequent antibacterial protection during bone regeneration, without using growth factors or antibiotics

Silver-induced γ→ε martensitic transformation in FeMn alloys : an experimental and computational study

Altres ajuts: acords transformatius de la UABPorous FeMn alloys with additions of 0, 1, 3 and 5 wt.% of Ag were fabricated using powder metallurgy and sintering. The microstructure of the fabricated alloys was characterized using X-ray diffraction, transmission electron microscopy and selected area electron diffraction. While equiatomic FeMn and FeMn-1Ag alloys possess a fully austenitic structure, a change in the crystallographic structure is observed upon addition of 3 and 5 wt.% of Ag, where a mixture of γ austenite and ε martensite phases is observed. Compression tests reveal that such structural transition causes an increase of the yield stress. The evolution of microstructure with the Ag content can be understood from theoretical calculations which show that Ag atoms prefer the intrinsic stacking fault (ISF) sites, revealing lower energy for the ε-like atomic plane sequence. This causes local depletion of the electronic charge, therefore weakening the interatomic bonds at the ISF plane and facilitating the phase transition. In addition, the total energy difference between the γ and ε phases decreases upon Ag addition. This enables the coexistence of both phases in the sample with 5 wt.% Ag. Both experimental and theoretical data agree that the magnetization value gradually increases upon Ag addition. This is due to the local stress that is introduced by Ag atoms, which expand the Ag-Fe and Ag-Mn first neighbour interatomic bonds compared to FeMn. This stress results in electronic charge that locally alters the Fe and Mn atomic magnetic moments. These results are appealing for the design of FeMn-based alloys with tuneable phase composition and physical properties for several technological application

Tribocorrosion behavior of β-type Ti-Nb-Ga alloys in a physiological solution

Tribo-electrochemical behavior in physiological solution of two β-type (100-x)(Ti-45Nb)-xGa (x = 4, 8 wt%) alloys, alongside β-Ti-45Nb and medical grade Ti-6Al-4V ELI, was investigated. Microstructure and mechanical behavior were evaluated by X-ray diffraction, microhardness and ultrasonic method. Tribocorrosion tests (open circuit potential, anodic potentiostatic tests) were performed using a reciprocating pin-on-disk tribometer under constant load. Degradation mechanisms are similar for the alloys: plastic deformation, delamination, abrasive and adhesive wear. Among the β-Ti-Nb alloys, an improved wear resistance with lower damage was remarked for β-92(Ti-45Nb)-8Ga alloy, attributed to increased microhardness. Content of Ga3+ ions released in the test solutions were found to be in very low amounts (few ppb). Addition of Ga to Ti-45Nb resulted in improved corrosion resistance under mechanical loading

Effect of minor gallium addition on corrosion, passivity, and antibacterial behaviour of novel β-type Ti–Nb alloys

Metastable Ti–Nb alloys are promising bone-implant materials due to improved mechanical biofunctionality and biocompatibility. To overcome increasing bacterial infection risk, alloying with antibacterial elements is a promising strategy. This study investigates the effect of minor gallium (Ga) additions (4, 8 wt% Ga) to as-cast and solution-treated β-type Ti–45Nb-based alloy (96(Ti–45Nb)-4Ga, 92(Ti–45Nb)-8Ga (wt.%)) on corrosion and passive film properties, as well as cytocompatibility and antibacterial activity. The electrochemical properties were evaluated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott-Schottky analyses in phosphate-buffered saline (PBS). X-ray photoelectron spectroscopy (XPS) was performed to analyze the chemical composition of passive films. Early adhesion and viability of macrophages and Staphylococcus aureus were assessed by nucleocounting and colony-forming unit counting, respectively. The results showed that high corrosion resistance and passive film properties of Ti–45Nb are retained and even slightly improved with Ga. EIS results revealed that Ga addition improves the passive film resistance. XPS measurements of 92(Ti–45Nb)-8Ga show that the passive film contains Ti-, Nb- and Ga-based oxides, implying the formation of mixed (Ti–Nb-Ga) oxides. In addition, marginal Ga ion release rate was detected under free corrosion conditions. Therefore, it can be assumed that Ga species may contribute to passive film formation on Ga-containing alloys. The 92(Ti–45Nb)-8Ga elicited an antibacterial effect against S. aureus compared to cp-Ti at 4 h. Moreover, Ga-containing alloys showed good cytocompatibility with THP-1 macrophages at 24 h. In conclusion, it was demonstrated that Ga additions to Ti–45Nb are beneficial to corrosion resistance and showed promising initial host and bacterial interactions

Surface Modified β-Ti-18Mo-6Nb-5Ta (wt%) Alloy for Bone Implant Applications: Composite Characterization and Cytocompatibility Assessment

Commercially available titanium alloys such as Ti-6Al-4V are established in clinical use as load-bearing bone implant materials. However, concerns about the toxic effects of vanadium and aluminum have prompted the development of Al- and V-free β-Ti alloys. Herein, a new alloy composed of non-toxic elements, namely Ti-18Mo-6Nb-5Ta (wt%), has been fabricated by arc melting. The resulting single β-phase alloy shows improved mechanical properties (Young’s modulus and hardness) and similar corrosion behavior in simulated body fluid when compared with commercial Ti-6Al-4V. To increase the cell proliferation capability of the new biomaterial, the surface of Ti-18Mo-6Nb-5Ta was modified by electrodepositing calcium phosphate (CaP) ceramic layers. Coatings with a Ca/P ratio of 1.47 were obtained at pulse current densities, −jc, of 1.8–8.2 mA/cm2, followed by 48 h of NaOH post-treatment. The thickness of the coatings has been measured by scanning electron microscopy from an ion beam cut, resulting in an average thickness of about 5 μm. Finally, cytocompatibility and cell adhesion have been evaluated using the osteosarcoma cell line Saos-2, demonstrating good biocompatibility and enhanced cell proliferation on the CaP-modified Ti-18Mo-6Nb-5Ta material compared with the bare alloy, even outperforming their CaP-modified Ti-6-Al-4V counterparts

Surface Modified β-Ti-18Mo-6Nb-5Ta (wt%) Alloy for Bone Implant Applications : Composite Characterization and Cytocompatibility Assessment

Commercially available titanium alloys such as Ti-6Al-4V are established in clinical use as load-bearing bone implant materials. However, concerns about the toxic effects of vanadium and aluminum have prompted the development of Al- and V-free β-Ti alloys. Herein, a new alloy composed of non-toxic elements, namely Ti-18Mo-6Nb-5Ta (wt%), has been fabricated by arc melting. The resulting single β-phase alloy shows improved mechanical properties (Young's modulus and hardness) and similar corrosion behavior in simulated body fluid when compared with commercial Ti-6Al-4V. To increase the cell proliferation capability of the new biomaterial, the surface of Ti-18Mo-6Nb-5Ta was modified by electrodepositing calcium phosphate (CaP) ceramic layers. Coatings with a Ca/P ratio of 1.47 were obtained at pulse current densities, −j, of 1.8-8.2 mA/cm 2, followed by 48 h of NaOH post-treatment. The thickness of the coatings has been measured by scanning electron microscopy from an ion beam cut, resulting in an average thickness of about 5 μm. Finally, cytocompatibility and cell adhesion have been evaluated using the osteosarcoma cell line Saos-2, demonstrating good biocompatibility and enhanced cell proliferation on the CaP-modified Ti-18Mo-6Nb-5Ta material compared with the bare alloy, even outperforming their CaP-modified Ti-6-Al-4V counterparts

Development of Novel Low-Modulus β-Type Ga-/Cu-Bearing Ti–Nb Alloys for Antibacterial Bone Implant Applications

Commercially available titanium (Ti) alloys, such as Ti–6Al–4V and c.p. Ti, even though established in clinical use as load-bearing bone implant materials in orthopedics and dentistry, possess significant drawbacks that may lead to implant failure: i) presence of alloying elements with harmful health effects, ii) high Young’s modulus (E > 100 GPa) compared to human cortical bone (Ebone = 10 – 30 GPa), and iii) lack of antibacterial activity against multidrug-resistant bacteria, which may lead to implant-associated infections. To overcome the first two drawbacks, a new generation of biocompatible metastable β-type Ti alloys has been developed, in particular β-type Ti–Nb alloys, which are versatile candidates due to their low Young’s modulus, high strength-to-weight ratio and improved corrosion resistance. The present work aims to tackle all three aforementioned issues by developing novel β-type Ti–45Nb-based alloys with potential intrinsic antibacterial activity by adding antibacterial gallium (Ga) and copper (Cu) in minor amounts (up to 8 wt.%) via metallurgical route. Nine alloys with the following chemical compositions: (100-x)(Ti–45Nb)–xGa, (100-x)(Ti–45Nb)–xCu (where x = 2, 4, 6, 8 wt.%), and 96(Ti–45Nb)–2Ga–2Cu, based on alloy design approaches, were produced by controlled casting and homogenization treatment. The effect of antibacterial alloying additions on phase constitution, mechanical characteristics, corrosion, and tribocorrosion response in a simulated physiological environment has been investigated. All nine alloys in the homogenized state display a single-phase β (BCC) phase microstructure, whose lattice parameter is proved to be sensitive to Ga and Cu content, with an almost linear contraction. The mechanical characteristics are strongly influenced by Ga and Cu addition, with a general strengthening effect mainly attributed to substitutional solid solution strengthening, and to grain boundary strengthening in case of Ga. Deformation behavior indicates high mechanical stability of the β phase, suggesting dislocation slip as dominant deformation mechanism. The results demonstrate that strategic alloy design is an effective method to significantly increase strength without adversely affecting the Young’s modulus, which remains in the range of good biomechanical compatibility (E = 64 – 104 GPa). Evaluation of the corrosion response and metal ion release in simulated physiological environment demonstrates the high corrosion resistance of the nine alloys, whereas tribocorrosion wear resistance increases upon Ga addition. Further thermal (aging) treatments, carried out on a specific Cu-containing alloy, proved the feasibility of tailoring enhanced mechanical, chemical and potentially antibacterial properties by thermally-induced precipitation of Ti₂Cu intermetallic compound. These novel developed alloys are considered to be promising candidates for biomedical bone implant applications

Development of Novel Low-Modulus β-Type Ga-/Cu-Bearing Ti–Nb Alloys for Antibacterial Bone Implant Applications

Commercially available titanium (Ti) alloys, such as Ti–6Al–4V and c.p. Ti, even though established in clinical use as load-bearing bone implant materials in orthopedics and dentistry, possess significant drawbacks that may lead to implant failure: i) presence of alloying elements with harmful health effects, ii) high Young’s modulus (E > 100 GPa) compared to human cortical bone (Ebone = 10 – 30 GPa), and iii) lack of antibacterial activity against multidrug-resistant bacteria, which may lead to implant-associated infections. To overcome the first two drawbacks, a new generation of biocompatible metastable β-type Ti alloys has been developed, in particular β-type Ti–Nb alloys, which are versatile candidates due to their low Young’s modulus, high strength-to-weight ratio and improved corrosion resistance. The present work aims to tackle all three aforementioned issues by developing novel β-type Ti–45Nb-based alloys with potential intrinsic antibacterial activity by adding antibacterial gallium (Ga) and copper (Cu) in minor amounts (up to 8 wt.%) via metallurgical route. Nine alloys with the following chemical compositions: (100-x)(Ti–45Nb)–xGa, (100-x)(Ti–45Nb)–xCu (where x = 2, 4, 6, 8 wt.%), and 96(Ti–45Nb)–2Ga–2Cu, based on alloy design approaches, were produced by controlled casting and homogenization treatment. The effect of antibacterial alloying additions on phase constitution, mechanical characteristics, corrosion, and tribocorrosion response in a simulated physiological environment has been investigated. All nine alloys in the homogenized state display a single-phase β (BCC) phase microstructure, whose lattice parameter is proved to be sensitive to Ga and Cu content, with an almost linear contraction. The mechanical characteristics are strongly influenced by Ga and Cu addition, with a general strengthening effect mainly attributed to substitutional solid solution strengthening, and to grain boundary strengthening in case of Ga. Deformation behavior indicates high mechanical stability of the β phase, suggesting dislocation slip as dominant deformation mechanism. The results demonstrate that strategic alloy design is an effective method to significantly increase strength without adversely affecting the Young’s modulus, which remains in the range of good biomechanical compatibility (E = 64 – 104 GPa). Evaluation of the corrosion response and metal ion release in simulated physiological environment demonstrates the high corrosion resistance of the nine alloys, whereas tribocorrosion wear resistance increases upon Ga addition. Further thermal (aging) treatments, carried out on a specific Cu-containing alloy, proved the feasibility of tailoring enhanced mechanical, chemical and potentially antibacterial properties by thermally-induced precipitation of Ti₂Cu intermetallic compound. These novel developed alloys are considered to be promising candidates for biomedical bone implant applications