Search

The aim of the present paper is to apply the laser powder bed fusion process to a new biodegradable Mg-Zn-Zr-Ca alloy powder prepared via a mechanical alloying method from powder pure components. This additive manufacturing method is expected to allow for the obtaining of high biomechanical and biochemical performance. Various processing parameters for laser powder bed fusion are tested, with a special focus on laser energy density—E [J/mm3]—which is calculated for all experiment variants, and which represents an important processing parameter, dependent upon all the rest. The goal of all the trials is to find the most efficient schema for the production of small biodegradable parts for the medical domain, meaning the selection of optimal processing parameters. An important observation is that the most robust and homogeneous samples without cracks are obtained for lower values of the E, around 100 J/mm3. Thus, the most performant samples are analyzed by scanning electron microscopy, X-ray diffraction and by compression mechanical test.

To enhance their longevity, dental implants must be highly biocompatible and must have a low elastic modulus close to that of the bone. They must also possess a high superficial hardness and a high corrosion resistance. For these reasons, a recently developed low-modulus Ti-27Nb alloy with nontoxic elements was treated by gas nitriding at high temperature in this study. A very thin nitrided layer of 0.5 μm in thickness followed by an enriched nitrogen zone was observed. Consequently, a very high hardness evaluated at about 1800 HV was obtained in surface, which represents an increase of 4-5 times the hardness of the non-nitrided alloy. This superficial hardness was experimentally observed to decrease up to 800 nm in depth from the surface to the core. The low modulus of Ti-27Nb (evaluated at 55 GPa, which is twice lower than the commercially pure titanium) was not affected by the surface nitriding treatment. A better corrosion resistance was observed and a significant decrease in ion release rates for the nitrided alloy (ion release of 1.41 ng/cm2 compared to the 163.58 ng/cm2 obtained for the commercially pure titanium at pH = 7.48 in artificial Carter-Brugirard saliva). The cytocompatibility was not compromised and the cell viability performed on human osteoblasts, fibroblastic cells, and epithelial cells was enhanced on the nitrided surface in comparison with the non-nitrided surface. These combined properties make the nitrided Ti-27Nb alloy a good candidate for dental implant applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1483-1490, 2019.

The novel Ti-20Zr-5Ta-2Ag alloy was characterised concerning its microstructure, morphology, mechanical properties, its passive film composition and thickness, its long-term electrochemical stability, corrosion resistance, ion release rate in Ringer solution of acid, neutral and alkaline pH values and antibacterial activity. The new alloy has a crystalline α microstructure (by XRD). Long-term XPS and SEM analyses show the thickening of the passive film and the deposition of hydroxyapatite in neutral and alkaline Ringer solution. The values of the electrochemical parameters confirm the over time stability of the new alloy passive film. All corrosion parameters have very favourable values in time which attest a high resistance to corrosion. Impedance spectra evinced a bi-layered passive film formed by the barrier, insulating layer and the porous layer. The monitoring of the open circuit potentials indicated the stability of the protective layers and their thickening in time. The new alloy releases (by ICP-MS measurements) very low quantities of Ti, Zr, Ag ions and no Ta ions. The new alloy exhibits a low antibacterial activity.

A new Ti-20Zr-5Ta-2Ag alloy was elaborated and characterized regarding its microstructure, its native passive film composition and thickness, its surface wettability, its electrochemical behavior in Ringer solution of different pH values, and its ion release. The new alloy has a bi-phase, α + β, acicular, homogeneous microstructure (scanning electron microscopy (SEM)). Its native passive film (12-nm thicknesses) consists of the protective TiO2, ZrO2, and Ta2O5 oxides, Ti and Ta suboxides, and metallic Ag (X-ray photoelectron spectroscopy (XPS) data). The alloy possesses high hydrophilic properties. The main electrochemical parameters of the new alloy are superior to those of Ti as a result of the beneficial influence of Zr, Ta, and Ag alloying elements, which reinforce its native passive film. Electrochemical impedance spectroscopy (EIS) spectra in Ringer solutions for the new alloy displayed better values of impedances and phase angles, proving a more insulate passive film than that on the Ti surface. The main corrosion parameters for the new Ti-20Zr-5Ta-2Ag alloy are more favorable by about 25 to 38 times than those of Ti, confirming extremely resistant passive film. The new Ti-20Zr-5Ta-2Ag alloy releases into Ringer solution low quantities of Ti4+, Zr4+ metallic ions (inductively coupled plasma–mass spectroscopy (ICP-MS)). The Ag+ ions are released in low quantity, conferring to this alloy’s low antibacterial activity. All experimental results show that the new Ti-20Zr-5Ta-2Ag alloy fulfills the requirements for biocompatibility, corrosion resistance, and antibacterial protection.

In this paper, the microstructure, mechanical and anticorrosive properties of the new CoCrNbMoZr alloy were studied in comparison with those of the commercial CoCrMo, Heraenium CE alloy. SEM and XRD techniques were used to evince the microstructure, and the morphology of the two alloys. Electrochemical linear and potentiodynamic polarisation and electrochemical impedance spectroscopy methods showed the electrochemical and corrosion behaviour of the alloys in artificial Carter-Brugirard saliva of different composition (doped with NaF, pH = 8.21 and undoped) and pH values (3.83; 7.84; 9.11) simulating the various functional conditions from the oral cavity. The new CoCrNbMoZr alloy showed self-passivation, more favourable values of the corrosion, passivation and transpassive potentials and tendency to passivation than those of the commercial Heraenium CE alloy and lower values of the passive current density; the values of the corrosion current densities and corrosion rates are lower and polarisation resistances are higher comparing with those of the reference alloy. EIS spectra revealed a passive film, a compact, resistant layer formed especially by the chromium, cobalt, niobium and zirconium oxides. Taking into consideration the microstructural features, electrochemical behaviour, corrosion resistance, and mechanical characteristics, it results that the new CoCrNbMoZr alloy is recommended for the dental applications.

The native passive film on the new Ti–15Ta–5Zr alloy surface contains the protective TiO2, Ta2O5 and ZrO2 oxides (XPS analysis). The decrease of the corrosion current densities and the increase of the polarisation resistances values signify the thickening of the passive film in time. The duplex oxide film formed by the inner, compact, layer and by the outer, porous layer was modelled; electrical parameters indicated the thickening over time both of the barrier and porous layers. XPS and SEM analyses demonstrated the in time deposition of new layers consisting by brushite in acid Ringer solution and from hydroxyapatite in neutral and alkaline Ringer solutions.

We applied a new nitrogen-implantation technique (trademark Hardion+) using a source of nitrogen ions, electron cyclotron resonance that assures higher energy and deeper implantation than the conventional techniques. The N-implantation surface of the new Ti-25Ta-25Nb alloy was analyzed as follows: for the phase identification by x-ray diffraction (XRD) in a glancing geometry (1°); for the hardness by the nano-indentation method; for the corrosion behaviour in Ringer solutions of different pH values (simulating the real conditions from the human body) by cyclic and linear polarization, electrochemical impedance spectroscopy and the monitoring of the open circuit potentials and corresponding potential gradients. XRD pattern was indexed with face-centred cubic TiN compound partially substituted with TaN and NbN. The hardness increased about 2 times for the N-implantation alloy. The implantation layer had a protection effect, increasing the corrosion and passivation potentials and decreasing the tendency to passivation and passive current density, due to its compactness, reinforcement action. The corrosion current density and rate decreased by about 10 times and the polarization resistance increased by about 2 times, indicative of a more resistant nitride layer. The porosity was much reduced and the protection efficiency had values closed to 90%, namely the implantation treatment led to the formation of a dense, resistant layer. Impedance spectra showed that the capacitive behaviour of the N-implantation alloy was more insulating and protective. An electric equivalent circuit with two times constants was modelled.

This paper describes the synthesis of a novel Ti-15Ta-5Zr alloy with an α + s stable, homogeneous, biphasic microstructure (by optical microscopy, X-ray diffraction and scanning electron microscopy) and the determination of its mechanical properties, hardness and a Young’s modulus of 42.2 GPa. The alloy passive film composition and thickness were analyzed by X-ray photoelectron spectroscopy; a thick, compact native passive film containing the protective oxides of all constituent elements (TiO2, Ta2O5, ZrO2) was identified. The electrochemical parameters confirmed a nobler behaviour and a more capacitive, resistant passive film on the alloy surface compared to Ti and other existing implant alloys; these facts are due to the alloying elements that, by their oxides stabilize and reinforce the alloy passive film. This passive film thickened in time, which increased its protective capacity. The new alloy had no susceptibility to galvanic or local corrosion. Ti-15Ta-5Zr alloy is recommended as an advanced orthopaedic implant material.

The new Ti-15Ta-5Zr alloy revealed a homogeneous bi-phase α + β microstructure without inclusions or secondary phases. The alloy native passive film contains both Ti2O3, and TiO2 oxides and very resistant Ta2O5 and ZrO2 oxides (X-ray photoelectron spectroscopy). All main electrochemical and corrosion parameters in artificial Carter-Brugirard saliva had more favourable values than those of Ti and other implant alloys, due to the Ta and Zr alloying elements, which contributed with their protective oxides to the native passive film and due to the alloy very homogeneous microstructure. Impedance spectra indicated a passive film formed by two layers: an inner, insulating, barrier layer that provides the high corrosion resistance and an outer, porous, less protective layer that permits the absorption of ions and species from surrounding environment into its pores, favouring both interaction and bioactivity. X-ray photoelectron spectroscopy and scanning electron microscopy detected new depositions (Na3PO4 and K3PO4 protective compounds) of 5 nm thickness on the alloy surface after 1000 h in Carter-Brugirard saliva, which confer to the substrate both corrosion resistance and bioactivity.

The new ternary Ti–15Zr–5Nb alloy is non-toxic and non-allergenic and possesses very good mechanical and anticorrosive properties. A ceramic hydroxyapatite (HA) coating was deposited on this new alloy surface by a chemical method. The formation of HA was proved by Raman micro-spectroscopy and X-ray photoelectron spectroscopy, which identified the main characteristic features for the crystalline HA. This ceramic coating has an optimal microstructure and morphology (from scanning electron microscopy). Also, a pronounced roughness was indicated by 2D and 3D atomic force microscopy images, showing a very proper surface for the adherence of the bone cells. The electrochemical behavior and corrosion resistance of this ceramic HA coating were studied in Ringer solutions. The main electrochemical parameters had more favorable values for the HA coated alloy due to the protective effect of the coating that thickened the native passive film on the alloy surface and together acted as a barrier against the ion diffusion. The HA coating increased the corrosion resistance of the substrate by its resistive properties to a large extent. Electrochemical impedance spectroscopy data were modeled by a two time constants electric equivalent circuit for the bare alloy and with a three time constant circuit for the HA coated alloy (formed from inner oxide layer, porous oxide layer and respectively outer HA porous layer). The HA coating thickened over time, improving its bioactivity and assuring long-term corrosion resistance. Therefore, the new Ti–15Zr–5Nb alloy coated with ceramic HA satisfies the most exigent requirements and signifies a progress in the domain of the orthopedic implant alloys.

A novel ternary Ti–15Zr–10Nb alloy with innovative microstructural and mechanical properties and very good long-term corrosion resistance in simulated physiological solutions was studied in this paper. Optical and scanning electron microscopy (SEM) observations revealed α + β biphasic Widmanstatten microstructure with characteristic interleaving lamella of α and β phases. Energy dispersive spectroscopy (EDS) measurements gave good compositional homogeneity with wt.% contents of 75 ± 5% for Ti, 15 ± 2% for Nb, and 10 ± 2% for Zr. The XRD pattern was indexed to a biphasic crystalline structure containing the hexagonal α phase with calculated lattice parameters of a = 2.92 A, c = 4.63 A and the cubic β phase with calculated lattice parameter of a = 3.19 A. The alloy has very good mechanical properties: Young’s modulus of 64 GPa, very close to that of the human bone; superior ultimate tensile strength, appropriate 0.2% yield strength and strain to fracture to those of Ti. The alloy native passive film has a thickness of 5.5 ± 0.5 nm and contains protective TiO 2 , ZrO 2 and Nb 2 O 5 oxides (X-ray photoelectron spectroscopy – XPS analysis). The cyclic voltammetry in Ringer’s solutions indicated a nobler electrochemical behaviour of the alloy in comparison with Ti due to the beneficial influence of the alloying elements, which participate with their oxides to the compactness, thickening, reinforcement of the native passive film. The electrochemical impedance spectra were modelled with an electric equivalent circuit comprising two time constants: for inner, compact layer and outer, porous slightly inferior protective layer.

This article analyses the microstructure, electrochemical behavior, and biocompatibility of a novel Ti-20Nb-10Zr-5Ta alloy with low Young’s modulus (59 GPa) much closer to that of bone, between 10 and 30 GPa, than Ti and other Ti alloys used as implant biomaterial. XRD and SEM measurements revealed a near β crystalline microstructure containing β phase matrix and secondary α phase, with a typical grain size of around 200 μm. The corrosion behavior in neutral Ringer solution evidenced: self-passivation behavior characterizing a very resistant passive film; an easy passivation as a result of favorable influence of the alloying elements Nb, Zr, and Ta that participate with their passive oxides to the formation of the alloy passive film; low corrosion and ion release rates corresponding with very low toxicity. In MEM solution, the novel alloy demonstrated very high corrosion resistance and no susceptibility to localized corrosion. Biocompatibility was evaluated on in vitro human osteoblast-like and human immortalized pulmonary fibroblast cell (Wi-38) lines and the new Ti-20Nb-10Zr-5Ta alloy exhibited no cytotoxicity. The new Ti-20Nb-10Zr5Ta alloy is a promising material for implants due to combined properties of low elastic modulus, very low corrosion rate, and good biocompatibility.

In this paper, we applied on the surface of the new Ti%20Nb%10Zr%5Ta alloy nano-crystalline hydroxyapatite (HA) coating by the method of the chemical deposition in a solution supersaturated with Ca2+ and inline image ions. The composition and crystallinity of the obtained coating was determined by X-ray diffraction, micro-Raman, infrared, and energy dispersive X-ray spectroscopies and its morphology and porosity by scanning electron microscopy. The coating long-term corrosion behavior for 3000 soaking hours in simulated human fluids (Ringer's solutions of different pH values) was studied by cyclic potentiodynamic and linear polarization, electrochemical impedance spectroscopy and monitoring of the open circuit potentials and corresponding open circuit potential gradient due to the pH non-uniformity of the biofluid. Also, the coating biocompatibility was performed by cells (human osteoblast % HOS and human immortalized pulmonary fibroblast % Wi-38) adhesion and proliferation testing in the HA coated bioalloy extract compared to respective effects of the un-coated bioalloy extract. The initial HA nano-coating promoted the deposition of new HA layers, thickening itself and showing its ability to induce the formation of this main inorganic component of the human bone, therefore denoting bioactivity of the HA nano-coated alloy.

A porous, homogeneous, phosphorous-enriched oxide nanolayer was realized on the new Ti-15Ta-5Zr alloy surface by the anodic galvanostatic electrodeposition in phosphoric acid solution. This nanolayer contains TiO2, ZrO2oxides, tantalum suboxides, andPO43-ions incorporated in the time of the electrodeposition process and has a thickness of 15.5 nm (X-ray photoelectron spectroscopy data). Atomic force microscopy determined a homogeneous roughness. Scanning electron microscopy evinced a porous microstructure that can stimulate the growth of the bone tissue into pores. The presence of thePO43-anions promotes the electrostatic bonds between the nanolayer and different species from the biofluid, namely, osteoinduction. The anodic oxidation nanolayer improved all electrochemical and corrosion parameters conferring superior protection to the substrate by its higher resistance to the ion migration. Impedance spectra showed that the electrodeposited nanolayer is formed by an inner, dense, barrier layer and an outer porous layer. The nanolayer thickened in time, namely, is bioactive. The oxidized nanolayer is able to protect the alloy from ion release, to assure long-term corrosion resistance, to minimize adverse reactions, to increase alloy bioactivity, to stimulate cell growth, and to favor osseointegration.

The corrosion resistance of new Ti–15Zr–5Nb alloy was correlated with its microstructure, surface structure and composition of its native passive film and of film formed after immersion for 1500 h in Ringer solutions of different pH values. Nobler passive behaviour of alloy in comparison with Ti and similar ternary alloy was determined due to its more compact passive film (containing TiO2, Ti2O3, ZrO2 and Nb2O5). EIS spectra depicted predominantly capacitive behaviour, passive film formed by two layers. After long-term immersion, XPS, Raman spectroscopy, SEM and EDX revealed the same protective oxides and Ca3(PO4)2 compound (precursor of hydroxyapatite) deposited on alloy surface.

The binary Ti–20Zr alloy was elaborated with the aim to be used as small diameter implant placed in narrow edentulous ridge. The alloy surface was galvanostatically anodized in 1 M H3PO4 solution to increase its corrosion resistance and bioactivity. The results of energy dispersive X-ray spectroscopy, Raman spectroscopy, Fourier-transform infrared and X-ray photoelectron spectroscopy showed that the alloy surface was covered by a quasi-amorphous TiO2 oxide based nanolayer with very small crystalline nuclei of rutile-type structure that incorporated phosphorous ions. The anodized nanolayer revealed submicron surface features and nanoscale roughness measured by atomic force microscopy, and flake-like platelets observed by scanning electron microscopy. The electrodeposited nanolayer acted as a barrier against the diffusion of ions through it and reduced very much (about ten times lower) the corrosion and ion release rates, a good indicator of increased long-term alloy biocompatibility in Ringer's solutions/simulated body fluids. The main electrochemical parameters evinced a nobler behavior of the anodized alloy in comparison with bare one. Electrochemical impedance spectroscopy indicated that the anodization treatment provided the formation of a more stable, resistant nanolayer. Long-term experiments denoted the improvement over time of the protective properties of the anodized nanolayer by its thickening. Immersion of the anodized alloy in neutral and alkaline Ringer's solutions resulted in the deposition of nanostructured coatings with a morphology of entangled acicular n-HA nanocrystallites, while brushite coatings deposited in acid Ringer's solution. The anodized nanolayer obtained on the Ti–20Zr alloy surface endowed the substrate both with protection and bioactivity.

An advanced Ti–20Zr alloy was obtained by double vacuum melting in a semi-levitation furnace with cold crucible. The alloy shows fully lamellar α + β microstructure. Cyclic potentiodynamic polarization curves revealed that the alloy passivated easier, more rapid than Ti, having a more stable passive film in Ringer solutions of different pH values, simulating severe functional conditions of an implant. In neutral and alkaline Ringer solutions, the alloy passive film improved its properties in time (1500 h) by the deposition of protective hydroxyapatite, as was demonstrated by XPS, SEM, EDX, Raman and FT-IR measurements. Alloy presented lower corrosion rates and higher polarization resistances (from linear polarization measurements) than those of Ti (tens of times) proving a more resistant passive film. Alloy open circuit potentials had more electropositive values in comparison with Ti and tended to nobler values in time, which denote better passive state and its enhancement in time, due to the new depositions from the physiological solutions. Nyquist and Bode spectra depicted a more protective passive film on the alloy surface than on Ti surface. The passive film is formed by two layers: an inner barrier layer and an outer porous layer. An electric equivalent circuit with two time constants was modeled.

The corrosion behavior of a new, advanced Ti-20Zr alloy with α+β microstructure (determined by optical microscopy, XRD, and SEM) and very good mechanical properties (obtained from the stress-strain curve) is studied in this paper. The composition of the alloy native passive film was determined from a XPS analysis and the long-term corrosion resistance in undoped and doped states with 0.05M NaF artificial Carter-Brugirard saliva of different pH values, simulating the severe functional conditions of a dental implant, was analyzed by electrochemical methods. This alloy possesses an advantageous balance between good mechanical resistance and plasticity and Young’s modulus and exhibits more favorable electrochemical parameters and corrosion resistance than CP Ti due to its more resistant passive layer containing Ti2O3, TiO2, and ZrO2 protective oxides. After 1000 h of immersion in saliva, the protective properties of the alloy were enhanced due to the deposited surface layer that incorporated protective phosphates (shown by SEM and XPS).

In this paper, we applied the potentiostatic anodisation method on the new Ti–20Nb–10Zr–5Ta alloy surface with the aim to increase its stability and bioactivity. The morphology (SEM) and composition (Raman, FT-IR) of the obtained anodisation nanolayer are studied. Also, electrochemical stability (by cyclic potentiodynamic polarisation and EIS), corrosion resistance (by linear polarisation), long-term behaviour (by monitoring of the open circuit potentials and corresponding open circuit potential gradients) and the characterisation of the layers deposited on the alloy surface after 1000 h in acid, neutral and alkaline Ringer and neutral Ringer–Brown solutions are presented. By potentiostatic anodisation, on the alloy surface was electrodeposited a continuous nanolayer containing TiO2 rutile type oxide. The anodised layer possesses better protective properties and at the same time better porosity, therefore a higher stability and bioactivity in comparison with the native passive film. After 1000 h in the testing solutions promoted the deposition of the brushite, phosphatotitanate and hydroxyapatite, precursors, respectively component of the human bone, namely this layer is bioactive.

A new ternary Ti–15Zr–5Nb alloy was elaborated with the aim to satisfy the most stringent requirements of a good implant material. The alloy has α + β bi-phase microstructure (by XRD and optical microscopy) and presents a proper combination between Young's modulus, elasticity and good ultimate tensile strength and 0.2% yield strength (from stress–strain tensile curve), indicating a good suitability as implant material. Electrochemical behaviour in artificial Carter-Brugirard saliva of different pH values (3.96, 7.84, and 9.11) and composition (un-doped and doped with 0.05 M NaF) that simulate the severe functional conditions in the oral cavity was evaluated. All electrochemical parameters of the new alloy revealed more favourable values than those of the CP Ti and Ti–6Al–4V ELI alloy, showing a more compact, resistant passive film formed on the new alloy surface. The corrosion rates and corresponding ion release rates for the new Ti–15Zr–5Nb alloy exhibited very low values (hundreds of times smaller) in comparison with similar commercial biomaterials. Electrochemical impedance spectra distinguished bi-layered passive film formed by inner, barrier layer and outer, porous layer. X-ray photoelectron spectra and scanning electron microscopy (SEM) observations proved that in time, protective compounds were deposited from saliva on the alloy surface, enhancing its corrosion resistance.

A new quaternary Ti–20Nb–10Zr–5Ta alloy was thermo-mechanically processed; applying a stress of 10 ton-forces after heat treatment at 1000 °C it resulted a very homogeneous, fine microstructure characterized by the best mechanical properties: low Young's modulus (60 GPa) and high tensile strength and hardness. The corrosion behaviour of this processed alloy after long-term soaking (5000 h) in simulated human fluid (Ringer solution) was studied. SEM micrographs of as-cast and processed alloy after immersion proved that their surfaces were covered with a layer with a porous microstructure. EDX analysis detected Ca, P, and O as constituent elements of this porous layer. XPS determined the presence of the protective TiO2, Nb2O5, ZrO2, and Ta2O5 oxides and of the hydroxyapatite deposited from solution. All electrochemical parameters exhibited more favourable values for the processed alloy indicating the beneficial influence of the applied treatment. Impedance parameters revealed a nobler behaviour of the processed alloy than of the as-cast one. EIS spectra showed a passive film with two layers: a compact, inner, electronically conducting, barrier layer and an outer, porous layer.

International audience; In this work, the new (Ti-Zr)-1.5Mo-3Sn biomedical alloy showing a large superelastic recovery strain of 7% and Young's modulus of 60GPa was characterized and compared with CP Ti and Ti-6Al-4V alloys currently used in medicine. The microstructure of the new (Ti-Zr)-1.5Mo-3Sn alloy consists of single phase (XRD and optical microscopy results). The new alloy has a relatively thick (7.0nm) native passive film mainly formed by protective TiO2, ZrO2, MoO2, and SnO2 oxides (XPS data). The electrochemical parameters for the new alloy have more favorable values than those of CP Ti, and Ti-6A-4V alloy, namely a nobler electrochemical behavior. The corrosion current density and rate of the (Ti-Zr)-1.5Mo-3Sn alloy are about 7 times lower and the polarization resistance is about 5 times higher than those obtained for the comparing metallic biomedical materials. Electrochemical impedance spectra proved that the new alloy presents the most insulating and protective passive film out of the three studied materials.

A new quaternary Ti–20Nb–10Zr–5Ta alloy with β-near microstructure was obtained. Its native passive film composition and its modification and corrosion resistance after 2000 immersion hours in simulated biofluids were studied. The native film on the alloy surface contains TiO 2 , Nb 2 O 5 , ZrO 2 , Ta 2 O 5 protective oxides as was demonstrated by XPS. After 2000 h, XPS revealed the presence of same oxides and calcium, phosphorous ions deposited from physiological solutions as hydroxyapatite. In Ringer and Ringer–Brown solutions, the new alloy presented low corrosion rates. Impedance data exhibited a passive film with two layers: an inner, barrier layer and an outer, porous layer.

A new Ti-20Nb-10Zr-5Ta bioalloy with low Young's modulus (59 GPa) was coated with nanocrystalline hydroxyapatite (HA) ceramic layer by chemical method of soaking in a slightly supersaturated calcium and phosphate ions solution. The formation of HA was demonstrated using XRD, Raman microscopy and energy-dispersive X-ray spectroscopy; the coating morphology and microstructure were determined using SEM. The coating protective capacity and its long-term (2000 h) stability in simulated biofluids were revealed by the improvement of the all electrochemical parameters; also, HA ceramic coating reduced the alloy corrosion and ion release rates. After 2000 immersion hours in biofluids no compositional change occurs in the HA ceramic coating, only depositions from solution take place that change the coating morphology. Also, the in time increase of the coating stability and thickness (as a result of the new deposition from physiological solutions) indicates bioactivity.

In the present work, nitrogen ion implantation (original method) to enhance the corrosion performance and cytocompatibility of biomedical pure titanium (CP Ti) and Ti–6Al–4V alloy has been studied. Different characterization methods were used to investigate the corrosion resistance of the nitrided Ti and Ti–6Al– 4V samples such as anodic polarization, electrochemical impedance spectroscopy, monitoring of the open circuit potentials and corresponding gradients, evaluation of corrosion rates. Further, cell viability, initial cell spreading and osteoblast proliferation were tested in order to assess cytocompatibility of modified Ti and Ti–6Al–4V alloy. In severe functional conditions, the main electrochemical parameters for nitrided biomaterials presented better values, revealing nobler behaviour than un-nitrided samples; these more favourable values assure a very good corrosion resistance for long term of the treated biomaterials. The results of biological performance evaluation indicated that nitrided Ti and Ti–6Al–4V represent suitable biomaterials for the adhesion and proliferation of human osteoblastsin vitro. All these findings demonstrate that nitrided biomaterials exhibited a very good improvement of their corrosion resistance and biocompatibility, characteristics which recommend them as potential candidates for bone implants.

For an alloy to be suitable for use as an implant material, it must have a low specific weight and Young’s modulus, good mechanical properties that are similar to those of bone, and very good corrosion resistance and biocompatibility. In this study, we have developed a novel Ti-20Nb-10Zr-5Ta alloy that is composed of nontoxic, nonallergenic, corrosion-resistant elements. This alloy has low specific weight and Young’s modulus and good mechanical properties. It has a fine microstructure with a matrix that is mainly composed of the β phase and some α phase due to recrystallization during cooling. It shows elastoplastic behavior with a fairly linear elastic behavior and low Young’s modulus (59 GPa). In addition, its ultimate tensile strength, 0.2% yield strength, and hardness are higher than those of CP Ti, commercial Ti-6Al-4V, and similar β-type alloys. It exhibited a very stable passive state and its electrochemical parameters and corrosion and ion release rates were better than those of CP Ti in Ringer’s solutions of different pH values that simulate the severe functional conditions of an implant; this is attributable to the beneficial influence of the alloying elements and to the better protective properties of the coated passive film.

In this work, a new ternary Ti–25Ta–5Zr alloy (with nontoxic alloying elements) was obtained and used to develop a thermo-mechanical procedure in order to optimize the balance strength – elastic modulus. Data about structural (by SEM) and mechanical properties are investigated. Also, its electrochemical behaviour in Ringer–Brown and Ringer solutions of different pH values (simulating severe functional conditions of an implant) was studied by cyclic potentiodynamic and linear polarization and electrochemical impedance spectroscopy (EIS). From cyclic potentiodynamic polarization curves it resulted the nobler behaviour of the thermo-mechanical treated alloy than as-cast alloy due to the favourable influence of the applied processing. Impedance spectra were fitted with one time constant equivalent circuit characterizing a very stable, resistant oxide passive film. The values of the open circuit potentials for the treated alloy are nobler than of the as-cast alloy and tended to more positive values in time, proving that the passive film on its surface is more compact and thickened in time.

In this work, a multi-elementary Ti–10Zr–5Nb–5Ta alloy, with non-toxic alloying elements, was used to develop an accumulative roll bonding, ARB-type procedure in order to improve its structural and mechanical properties. The alloy was obtained by cold crucible semi-levitation melting technique and then was ARB deformed following a special route. After three ARB cycles, the total deformation degree per layer is about 86%; the calculated medium layer thickness is about 13 μm. The ARB processed alloy has a low Young’s modulus of 46 GPa, a value very close to the value of the natural cortical bone (about 20 GPa). Data concerning ultimate tensile strength obtained for ARB processed alloy is rather high, suitable to be used as a material for bone substitute. Hardness of the ARB processed alloy is higher than that of the as-cast alloy, ensuring a better behaviour as a implant material. The tensile curve for the as-cast alloy shows an elastoplastic behaviour with a quite linear elastic behaviour and the tensile curve for the ARB processed alloy is quite similar with a strain-hardening elastoplastic body. Corrosion behaviour of the studied alloy revealed the improvement of the main electrochemical parameters, as a result of the positive influence of ARB processing. Lower corrosion and ion release rates for the ARB processed alloy than for the as-cast alloy, due to the favourable effect of ARB thermo-mechanical processing were obtained.

Passivating coatings of brushite (CaHPO 4 ·2H 2 O) were obtained on Ti and Ti–6Al–4V ELI alloy substrates by cathodic polarization. After soaking in Ringer's solution for 48 h brushite was transformed to hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) as confirmed by XRD, FT-IR and Raman spectroscopy. Electrochemical cyclic polarization curves of the coated biomaterials obtained in Ringer's solution at pH values of 7.1 and 8.91 as well as in Hank's Balanced Salt Solution (HBSS) at pH value of 7.4 show a nobler behavior than of the uncoated biomaterials. The coated biomaterials had lower corrosion rates than the uncoated biomaterials suggesting a protective character of the hydroxyapatite coating. Electrochemical impedance spectra (EIS) revealed capacitive behavior, owing to the protective, very resistant layer, the thickness of which increased with soaking time. The coated biomaterials presented higher electropositive open circuit potentials compared to the uncoated biomaterials as result of the protective effect of the coating. The morphology of the coatings changed with soaking time as the coatings became denser, smoother and better adhering. Hence such coatings may provide favorable structure for cell adhesion and proliferation.

The properties of the surface films formed on Ti and its Ti–5Al–4V and Ti–6Al–3.5Fe alloys by chemical (immersion in 10 M NaOH) and thermal treatment (500 °C) were studied in this paper. Their corrosion behaviour in Ringer solution was investigated. After treatments, the sample microhardness was measured. Also, the sample surfaces were observed by an optical microscope before and after immersion in Ringer solutions. The electrochemical behaviour of the surface films obtained by the chemical and thermal treatments was studied using the methods of the electrochemical impedance spectroscopy (EIS) and monitoring of open circuit potentials at different immersion periods (up to 60 days) in Ringer solution. Microhardness increased with the increasing loads for the studied materials, showing the existence of a compact protective layer. Microscopic observations exhibited more compact coatings after 60 days of exposure in Ringer solution, due to the formation of an apatite layer. EIS spectra revealed surface films with two layers: an inner, barrier protective layer and an outer, porous apatite layer. The impedance increases in time denoting that the films have grown by apatite nucleation. Also, EIS spectra showed that the complex treatment by chemical + heat method is the most efficiently. For the samples treated by the two processes (chemical + heat) the values of the open circuit potentials are nobler than of the chemical treated samples, denoting better protective, bioactive films.

A new Ti-6Al-2Nb-1Ta alloy was obtained for to satisfy the mechanical and anticorrosion requirements in neutral corrosive environment. The corrosion behaviour of this new Ti-6Al-2Nb-1Ta alloy in 0.1 M Na2SO4, 3% NaCl solutions and synthetic sea water was studied in this paper, using potentiodynamic and linear polarisation method, electrochemical impedance spectroscopy (EIS) and monitoring of the open circuit potentials. The structure of the alloy represents an α + β uniform structure with un-oriented grains. From the potentiodynamic polarisation curves it resulted that the studied alloy is self-passivated in all three solutions having a very good and very easy tendency to passivation. The most favourable values of the electrochemical parameters were registered in 0.1 M Na2SO4 solution due to its reduced corrosivity. EIS measurements proved the improvement of the passive layer resistance with the immersion time. An electric equivalent circuit with two time constants was fitted. The values of the polarisation resistances showed very good protective capacities which improved in time. The open circuit potentials have the general tendency to ennoble in time, suggesting the thickening of the passive films and the increase of their protective capacities.

A new titanium base Ti–6Al–4V–1Zr alloy covered with hydroxyapatite or bovine serum albumin/hydroxyapatite was characterized in this paper in order to be used as implant material. Following techniques were used: linear polarization, electrochemical impedance spectroscopy, scanning electronic microscopy, Fourier transform infrared spectroscopy and atomic force microscopy. For HA or BSA/HA covered alloy, the electric equivalent circuit contains two time constants (for the passive film and for coatings). The resistance of the protective films increased in time and BSA/HA coating was slightly rougher than HA coating, this situation being favourably to the cell adhesion.

In this study, a new Ti-25Ta-25Nb (mass%) β alloy was synthesised by cold crucible semi-levitation melting. After melting, each ingot was solution treated in the β-phase domain and water quenched in order to obtain a fully recrystallised homogeneous β-phase microstructure. To evaluate the bio-corrosion property of this new alloy, corrosion tests (cyclic potentiodynamic and linear polarisation, EIS) and surface analysis (SEM) were carried out in Ringer solution at different pH values (acid, neutral and basic). The results indicated that the corrosion resistance of the Ti-25Ta-25Nb alloy is quite higher than that of the commercially pure CP Ti alloy. These results show that this new alloy possesses all the characteristics necessary for its long-term use as medical implants.

International audience; In this study, we have synthesized a new Ti-23Nb-0.7Ta-2Zr-0.5N alloy composition with the aim to obtain useful mechanical properties to be used in medicine such as high strength, good superelastic property, low modulus, and large ductility. Thus, mechanical properties including superelasticity and plasticity were investigated in relation with the different deformation mechanisms observed (stress-induced martensitic transformation, twinning and dislocation slip). On the other hand, the corrosion resistance in simulated body fluid (Ringer solution) and the in vitro cell behavior (MG63 human osteoblasts) of such biomedical alloy were also evaluated in order to assess its biocompatibility.

International audience; A new superelastic Ti-23Hf-3Mo-4Sn biomedical alloy displaying a particularly large recovery strain was synthesized and characterized in this study. Its native passive film is very thick (18 nm) and contains very protective TiO2, Ti2O3, HfO2, MoO2, and SnO2 oxides (XPS analysis). This alloy revealed nobler electrochemical behavior, more favorable values of the corrosion parameters and open circuit potentials in simulated body fluid in comparison with commercially pure titanium (CP-Ti) and Ti-6Al-4V alloy taken as reference biomaterials in this study. This is due to the favorable influence of the alloying elements Hf, Sn, Mo, which enhance the protective properties of the native passive film on alloy surface. Impedance spectra showed a passive film with two layers, an inner, capacitive, barrier, dense layer and an outer, less insulating, porous layer that confer both high corrosion resistance and bioactivity to the alloy. In vitro tests were carried out in order to evaluate the response of Human Umbilical Vein Endothelial Cells (HUVECs) to Ti-23Hf-3Mo-4Sn alloy in terms of cell viability, cell proliferation, phenotypic marker expression and nitric oxide release. The results indicate a similar level of cytocompatibility with HUVEC cells cultured on Ti-23Hf-3Mo-4Sn substrate and those cultured on the conventional CP-Ti and Ti-6Al-4V metallic materials.

A new CoCrNbMoZr alloy, with Nb and Zr content is characterized from the point of view of surface features, corrosion resistance and biological performance in order to be proposed as dental restorative material. Its properties are discussed in comparison with commercial Heraenium CE alloy based on Co, Cr and Mo as well. The microstructure of both alloys was revealed by scanning electron microscopy (SEM). The composition and thickness of the alloy native passive films were identified by X-ray photoelectron spectroscopy (XPS). The surface characteristics were analyzed by atomic force microscopy (AFM) and contact angle techniques. The quantity of ions released from alloys in artificial saliva was evaluated with inductively coupled plasma-mass spectroscopy (ICP-MS) measurements. The electrochemical stability was studied in artificial Carter-Brugirard saliva, performing open circuit potentials, polarization resistances and corrosion currents and rates. The biological performance of the new alloy was tested in vitro in terms of human adipose stem cells (hASCs) morphology, viability and proliferation status. The new alloy is very resistant to the attack of the aggressive ions from the artificial saliva. The surface properties, the roughness and wettabiliy sustain the cell behavior. The comparison of the new alloy behavior with that of existing commercial CoCrMo alloy showed the superior properties of the new metallic biomaterial.

International audience; The influence of gas nitriding surface treatment on the superelastic Ti-23Nb-0.7Ta-2Zr-0.5N alloy was evaluated. A thorough characterization of bare and nitrided Ti-based alloy and pure Ti was performed in terms of surface film composition and morphology, electrochemical behaviour, and short term osteoblast response. XPS analysis showed that the nitriding treatment strongly influenced the composition (nitrides and oxynitrides) and surface properties both of the substrate and of the bulk alloy. SEM images revealed that the nitrided surface appears as a similar dotted pattern caused by the formation of N-rich domains coexisting with less nitrided domains, while before treatment only topographical features could be observed. All the electrochemical results confirmed the high chemical stability of the nitride and oxynitride coating and the superiority of the applied treatment. The values of the corrosion parameters ascertained the excellent corrosion resistance of the coated alloy in the real functional conditions from the human body. Cell culture experiments with MG63 osteoblasts demonstrated that the studied biomaterials do not elicit any toxic effects and support cell adhesion and enhanced cell proliferation. Altogether, these data indicate that the nitrided Ti-23Nb-0.7Ta-2Zr-0.5N alloy is the most suitable substrate for application in bone implantology

International audience; In this study, the "Gum Metal" titanium-based alloy (Ti-23Nb-0.7Ta-2Zr-1.2O) was synthesized by melting and then characterized in order to evaluate its potential for biomedical applications. Thus, the mechanical properties, the corrosion resistance in simulated body fluid and the in vitro cell response were investigated. It was shown that this alloy presents a very high strength, a low Young's modulus and a high recoverable strain by comparison with the titanium alloys currently used in medicine. On the other hand, all electrochemical and corrosion parameters exhibited more favorable values showing a nobler behavior and negligible toxicity in comparison with the commercially pure Ti taken as reference. Furthermore, the biocompatibility tests showed that this alloy induced an excellent response of MC3T3-E1 pre-osteoblasts in terms of attachment, spreading, viability, proliferation and differentiation. Consequently, the "Gum Metal" titanium-based alloy processes useful characteristics for the manufacturing of highly biocompatible medical devices.

International audience; In this study, a superelastic Ni-free Ti-based biomedical alloy was treated in surface by the implantation of nitrogen ions for the first time. The N-implanted surface was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and secondary ion mass spectroscopy, and the superficial mechanical properties were evaluated by nano-indentation and by ball-on-disk tribological tests. To investigate the biocompatibility, the corrosion resistance of the N-implanted Ti alloy was evaluated in simulated body fluids (SBF) complemented by in-vitro cytocompatibility tests on human fetal osteoblasts. After implantation, surface analysis methods revealed the formation of a titanium-based nitride on the substrate surface. Consequently, an increase in superficial hardness and a significant reduction of friction coefficient were observed compared to the non-implanted sample. Also, a better corrosion resistance and a significant decrease in ion release rates have been obtained. Cell culture experiments indicated that the cytocompatibility of the N-implanted Ti alloy was superior to that of the corresponding non-treated sample. Thus, this new functional N-implanted titanium-based superelastic alloy presents the optimized properties that are required for various medical devices: superelasticity, high superficial mechanical properties, high corrosion resistance and excellent cytocompatibility.

In this work, the anodic galvanostatic electrodeposition of an oxidation film containing phosphates on Ti-20Nb-10Zr-5Ta alloy from orthophosphoric acid solution is presented. Its composition was determined by X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman micro-spectroscopy, and its topography by atomic force microscopy (AFM). The corrosion resistance of the coated alloy in simulated human fluid (by linear polarization method and monitoring of open circuit potentials, corresponding open circuit potential gradients) as well as the characterization of the coating (by Raman spectroscopy and depth profile X-ray photoelectron spectroscopy (XPS)) deposited in a period of 300 h soaking in simulated human body fluid were studied. The electrodeposited film was composed of amorphous titanium dioxide and contained phosphate groups. The corrosion resistance of the coated Ti-20Nb-10Zr-5Ta alloy in neutral and alkaline Ringer's solutions was higher than that of the bare alloy due to the protective properties of the electrodeposited film. The corrosion parameters improved over time as result of the thickening of the surface film by the deposition from the physiological solution. The deposited coating presented a variable composition in depth: at the deeper layer nucleated nanocrystalline hydroxyapatite and at the outer layer amorphous calcium phosphate. Neste trabalho, a eletrodeposição galvanostática anódica de um filme de oxidação contendo fosfatos em liga de Ti-20Nb-10Zr-5Ta de uma solução de ácido ortofosfórico é apresentada. Sua composição foi determinada por difratometria de raios X (XRD), espectroscopia no infravermelho por transformada de Fourier (FTIR) e micro-espectroscopia Raman, e a topografia por microscopia de força atômica (AFM). A resistência à corrosão da liga recoberta em fluido humano simulado (por método de polarização linear, monitoramento de potenciais de circuito aberto e gradientes do potencial de circuito aberto correspondentes) assim como a caracterização do recobrimento (por espectroscopia Raman e perfil de profundidade por espectroscopia fotoeletrônica de raios X (XPS)) depositado por um período de imersão de 300 h em fluido humano simulado foram estudadas. O filme eletrodepositado era composto de dióxido de titânio amorfo e grupos fosfato. A resistência à corrosão da liga Ti-20Nb-10Zr-5Ta recoberta em soluções de Ringer neutra e alcalina foi maior que a da liga pura devido as propriedades protetoras do filme eletrodepositado. Os parâmetros de corrosão foram aprimorados com passar do tempo como resultado do espessamento do filme da superfície por deposição da solução fisiológica. O recobrimento depositado apresentou uma composição variável em profundidade, na camada mais profunda hidroxiapatita nanocristalina nucleada e na camada exterior fosfato de cálcio amorfo.

A new Ti-15Zr-5Nb alloy with suitable microstructure and mechanical properties was processed by galvanostatic anodization in 0.3 M H3PO4solution and a continuous nanostructured layer of protective TiO2oxide was electrodeposited. The obtained anatase oxide layer has a nanotubes-like porosity (SEM observations) and contains significant amount of phosphorus in phosphotitanate compound embedded in the oxide lattice (Raman, FT-IR, SEM, and EDX analysis). This layer composition can stimulate the formation of the bone and its porosity can offer a good scaffold for bone cell adhesion. The electrochemical behaviour, corrosion stability, and variations of the open circuit potentials,Eoc, and corresponding open circuit potential gradients,ΔEoc, for 1500 soaking hours in Ringer solutions of 3.21, 7.58, and 8.91 pH values were studied. The anodized layer was more resistant, stable (from EIS spectra), and was formed from an inner barrier insulating layer that assures the very good alloy corrosion resistance and an outer porous layer that provides the good conditions for cell development. The nanostructured alloy has higher corrosion stability, namely, a more reduced quantity of ions released and a lower toxicity than that of the bare one. The monitoring ofEocandΔEocshowed the enhancement and stabilizing of the long-term passive state of the anodized alloy and, respectively, no possibility at galvanic corrosion.

This paper presents a complete and complex characterization of the new Co-Cr-Nb-Mo-Zr alloy in comparison with the commercial CoCrMo (Heraenium CE) alloy. The alloy microstructure was showed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS); the composition and thickness of the native passive film were identified by X-ray photoelectron spectroscopy (XPS). Also, the surface roughness was revealed by atomic force microscopy (AFM) and the contact angle evinced the alloys hydrophilic properties. The amounts of ions released in artificial Carter-Brugirard saliva were evaluated by the inductively coupled plasma-mass spectroscopy (ICP-MS) technique. The corrosion rate was obtained by the linear polarization method. The cast new Co-Cr-Nb-Mo-Zr alloy is characterized by a multicomponent, fine dendritic structure with typical interdendritic distances of few microns. EDS spectra detected the alloying elements, Co, Cr, Nb, Mo, Mn, Si, etc. EDS elemental analysis quantified that Mo, Nb, Si and C are enriched in the interdendritic regions. XPS survey spectrum for the new Co-Cr-Nb-Mo-Zr alloy surface showed a complex feature that included the peaks for Co 2p, Cr 2p, Nb 3d, Mo 3d, Zr 3d, o 1s; this film is composed from chromium, niobium, molybdenum, zirconium, manganese, silicon oxides and is thicker (6.5 nm – 8.0 nm), more compact and enhanced with oxides as compared with that of commercial Co-Cr-Mo alloy. The topography and roughness parameters (AFM data) are similar for the two studied alloys and very proper for the cell adhesion. An increase in the contact angle value for the new Co-Cr-Nb-Mo-Zr alloy has been observed as compared to the commercial Heraenium CE alloy. The increase from 75.920 to 86.790 values indicates that the both alloys have hydrophilic character but the stronger one is for the commercial alloy. The quantity of ions (determined by ICP-MS method) released in artificial saliva for the both alloys is relatively small, but for the new alloy, the amount is significant lower. The quantified amounts in ppb (parts-per-billion, 10−9) sustain increased stability for the new alloy. The evolution of open circuit potentials in time for the both alloys depicts a trend to steady state sooner after immersion in the both cases; it is a specific aspect for passivity due to the protective oxides formed on the surface of the both alloys. The open circuit potentials tend to more electropositive values, indicating an increase of passive film thickness. The Tafel results showed that the new alloy is included in conventional stability scale „Perfect Stable” while the commercial alloy in “Very Stable” in the corrosion resistance group (corrosion classification). With the increase of immersion time, the penetration index, corrosion rate decreased. Also, the polarization resistance, Rp values for the new alloy increased in time as result of the passive film thickening; for the commercial alloy, polarization resistance decreased in time, denoting some dissolution and repassivation processes. Rp have higher values from about 8 times to 175 times than those of Heraenium CE alloy; correlating with the lower values of the corrosion current densities, it results a better corrosion resistance, a more resistant passive film for the new alloy due to its passive film that contains beside chromium oxide, niobium (Nb2O5, 49.8%) and zirconium oxides (ZrO2, 54.9%), as was showed by XPS analysis. In conclusion, the new Co-Cr-Nb-Mo-Zr alloy displayed an increased corrosion resistance as compared with the commercial Heraenium CE alloy.

International audience; In this study, the new Hardion+ micro-implanter technology was used to modify surface properties of biomedical pure titanium (CP-Ti) and Ti-6Al-4V ELI alloy by implantation of nitrogen ions. This process is based on the use of an electron cyclotron resonance ion source to produce a multienergetic ion beam from multicharged ions. After implantation, surface analysis methods revealed the formation of titanium nitride (TiN) on the substrate surfaces. An increase in superficial hardness and a significant reduction of friction coefficient were observed for both materials when compared to non-implanted samples. Better corrosion resistance and a significant decrease in ion release rates were observed for N-implanted biomaterials due to the formation of the protective TiN layer on their surfaces. In vitro tests performed on human fetal osteoblasts indicated that the cytocompatibility of N-implanted CP-Ti and Ti-6Al-4V alloy was enhanced in comparison to that of the corresponding non treated samples. Consequently, Hardion+ implantation technique can provide titanium alloys with better qualities in terms of corrosion resistance, cell proliferation, adhesion and viability.

Titanium possesses an excellent corrosion resistance in biological environments because the titanium dioxide formed on its surface is extremely stable. When aluminium and vanadium are added to titanium in small quantities, the alloy achieves considerably higher tensile properties than of pure titanium and this alloy is used in high stress-bearing situations. But these metals may also influence the chemostatic mechanisms that are involved in the attraction of biocells. V presence can be associated with potential cytotoxic effects and adverse tissue reactions. The alloys with aluminium and iron or with aluminium and niobium occur to be more suitable for implant applications: it possesses similar corrosion resistance and mechanical properties to those of titanium-aluminium-vanadium alloy; moreover, these alloys have no toxicity.In this paper, pure Ti, Ti-6Al-7Nb and Ti-6Al-4Fe with a nanostructured surface were studied. Data about mechanical behavior are presented. The mechanical behavior was determined using optical metallography, tensile strength and Vickers microhardness.For the electrochemical measurements a conventional three-electrode cell with a Pt grid as counter electrode and saturated calomel (SCE) as reference electrode was used. AC impedance data were obtained at open circuit potential using a PAR 263A potentiostat connected with a PAR 5210 lock-in amplifier. The ESEM and EDAX observation were carried out with an environmental scanning electronic microscope Fei XL30 ESEM with LaB6-cathode attached with an energy-dispersive electron probe X-ray analyzer (EDAX Sapphire). After 3 days of immersion in simulated body fluid the nucleation of the bone growth was observed on the implant surface.It resulted that the tested oxide films presented passivation tendency and a very good stability and no form of local corrosion was detected. The mechanical data confirm the presence of an outer porous passive layer and an inner compact and protective passive layer. EIS confirms the mechanical results. The thicknesses of these layers were measured. SEM photographs of the surface and EDX profiles for the samples illustrate the appearance of a microporous layer made up of an alkaline titanate hydrogel. The apatite-forming ability of the metal is attributed to the amorphous sodium titanate that is formed on the metal during the surface treatment.The results emphasized that the surface treatment increases the passive layer adhesion to the metal surface and improves the biocompatibility of the biomedical devices inducing the bone growth on the implant surface.

The corrosion resistance of the new Ti-6Al-4V-1Zr alloy in comparison with ternary Ti-6Al-4V alloy in Ringer-Brown solution and artificial Carter-Brugirard saliva of different pH values was studied. In Ringer-Brown solution, the new alloy presented an improvement of all electrochemical parameters due to the alloying with Zr; also, impedance spectra revealed better protective properties of its passive layer. In Carter-Brugirard artificial saliva, an increase of the passive film thickness was proved. Fluoride ions had a slight negative influence on the corrosion and ion release rates, without to affect the very good stability of the new Ti-6Al-4V-1Zr alloy.

In this study, a new Ti–25Ta–25Nb (mass%) beta alloy was synthesised by cold crucible semi-levitation melting. This technique made it possible to obtain homogeneous ingots although the elements used have very different melting points. After melting, a thermo-mechanical treatment was applied in order to obtain a perfectly recrystallised beta microstructure. For this alloy composition, the tensile tests showed a very low Young’s modulus associated with an important super-elastic behaviour, which contributes to decrease the elastic modulus under stress and to increase the recoverable strain. On the other hand, the corrosion tests, which were carried out in a neutral Ringer solution, indicated a corrosion resistance higher than that of the commercially pure CP Ti alloy. These results show that this new alloy possesses all the characteristics necessary for its long-term use in medical implants.

The paper presents the experimental results concerning the performance assessment of electrodeposited epoxy films using electrochemical techniques (electrochemical impedance spectroscopy–EIS and anodic polarization) assisted by microscopical studies. The films were formed during the cathodic and anodic electrodeposition of a modified epoxy resin on carbon steel substrate. The specimens were tested in a normal aerated 3% NaCl solution at room temperature for a total period up to 1500 hours. Analysis of the impedance spectra has established an equivalent electric circuit with two time constants fitted to describe the electrodeposited epoxy film/carbon steel/electrolyte system. The time monitoring of the principal elements from the equivalent electric circuit were used to determine protective properties of the electrodeposited epoxy films. Results show a high performance of electrodeposited epoxy films, characterized by uniformity, insignificant porosity, very low water and ions permeability.

Introduction In this paper, a novel Ti-15Ta-5Zr alloy with α+β stable, homogeneous, biphasic microstructure was synthesized; this alloy revealed very good mechanical properties and hardness and a Young’s modulus of 42.2 GPa, which are more suitable for an implant material than those of other existing implant materials (Ti, Ti-6Al-4V). Experimental The microstructure was identified by scanning electron microscopy (SEM). Electrochemical properties of the interface between new alloy and simulated physiological Ringer-Brown solution were investigated by the potentiodynamic cyclic and linear polarization and electrochemical impedance spectroscopy (EIS). Results and discussion SEM (Fig. 1) image of the chemically etched surface revealed a homogeneous α+β biphasic microstructure showing the characteristic interleaving lamellas of α and β phases. The cyclic potentiodynamic curves in Ringer-Brown solution (Fig. 2) showed the self-passivation of Ti-15Ta-5Zr alloy with a large constant current domain that indicates the absence of the electron transfer reactions and the existence of the ion transfer reactions, namely, the constant thickening of the oxide layer, according with the high field mechanism. The curve for Ti characterized by a slow increase of the passive current density with the applied potential suggests that its native passive film seems to dissolve and repassivate. These behavior differences between Ti and Ti-15Ta-5Zr alloy are due to the alloying elements Ta and Zr, which stabilize, reinforce the passive film on the new alloy surface. Alloy corrosion, Ecorr potentials have more electropositive value and passive current densities, ip are lower than those of Ti (Table 1) as result of the more compact, thicker, resistant passive film existing on the Ti-15Ta-5Zr alloy surface, that contains both protective TiO2 and Ta2O5 and ZrO2 oxides. The alloy corrosion current densities, icorr and rates, Vcorr are lower (of about 70 times smaller) than those of Ti, proving a more protective passive film on the alloy surface. The alloy polarization resistances, Rpreached higher values (about ten times higher) than those of Ti, fact that represents a very corrosion resistant material. Table 1. Main electrochemical parameters in Ringer-Brown solution Material Ecorr (mV) icorr (µA/cm2) Vcorr (µm/y) ip (µA/cm2) Rp (kΩ.cm2) Ti -250 3.890 44.1 10.5 29 Ti-15Ta-5Zr -210 0.055 0.63 1.12 250 The Nyquist plots (Fig. 3a) exhibited open arches, demonstrating capacitive behaviour, namely, a passive film with dielectric properties; the bigger diameters and impedance values for the alloy describe a more insulating, thicker, protective passive film on its surface. Bode phase spectra (Fig. 3b) displayed two phase angles; the higher phase angles recorded for the new alloy denote a nobler passive behaviour, a more stable passive state. These phase angles suggest a passive film with two layers: for the higher phase angle corresponds a barrier, compact, inner layer and the lower phase angle indicates a less protective, porous, outer layer. The open circuit potentials of the new Ti-15Ta-5Zr alloy shifted to nobler values in time; this behavior indicates the film thickening that confers high protection to alloy. SEM micrograph evinced (Fig. 4) some depositions on the alloy surfaces after 2000 immersion hours in Ringer-Brown solution; it is a continuous layer formed by globular nanocrystals with the diameter of about 2-3 µm, with interwoven texture in a porous feature. EDX elemental analysis (Fig. 4) detected the presence of calcium, phosphorus and oxygen, namely calcium phosphate, a precursor of the hydroxyapatite, the major inorganic component of the human bone. Therefore, the alloy surface represents a suitable support for the adhesion of the bone cells. Conclusions Main electrochemical parameters attested a nobler behaviour and lower corrosion rates, proving more resistant passive film on the alloy surface (in comparison with Ti) that is reinforced, stabilized by the very protective oxides of the alloying elements Ta and Zr. The new alloy represents an advanced alloy in the domain of the non-toxic, non-allergenic ternary implant alloys.