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Made available in DSpace on 2019-10-04T12:34:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-03-30 Fundacao Araucaria Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A number of researches have been concerned about the development of beta-type titanium alloys because they can present good biocompatibility, non-cytotoxicity, suitable mechanical and corrosion resistance behavior. However, due to their chemical inertness property, the surfaces of the novel Ti alloys must be modified by different methods to improve their bioactivity. This work is focused on the electrochemical surface modification of Ti-10Nb and Ti-20Nb alloys by Plasma Electrolytic Oxidation (PEO) method in 1.0 M H3PO4 electrolyte at 250 V. X-Ray diffraction showed that both binary Ti-Nb alloys are mainly composed of (alpha+beta) phase. The PEO treatment led to producing rough and thick titanium and niobium oxides films on the Ti-Nb alloys. The oxide films produced on the Ti-10Nb alloys have the anatase structure, whereas those formed on the Ti-20Nb alloy have an amorphous structure observed by Raman Spectroscopy. Hardness and elastic modulus were measured by instrumented indentation. Both oxide films are harder than their substrates (4.0-6.0 GPa) and have reduced elastic modulus values (100-110 GPa) compared to cp-Ti (reference). Linear reciprocating tests were employed to study the surface wear resistance of the samples. Among the non-treated samples, the Ti-10Nb alloy presented a better wear performance. In addition, the titanium and niobium oxides films formed on the Ti-10Nb alloy presented the most resistant surfaces. In relation to the cellular viability evaluation, the oxide films produced on both Ti-Nb alloys did not show any sign of cytotoxicity. Indeed, the porosity, roughness and chemical composition of the resulting titanium and niobium oxides films were able to promote osteoblast cells attachment and proliferation on their surfaces. Based on these findings, the PEO electrochemical treatment on Ti-10Nb alloy can form porous oxides coating and could be used as a reference line for manufacturing more wear resistant and non-cytotoxic surfaces to biomedical applications. (C) 2018 Elsevier B.V. All rights reserved. Univ Fed Parana, Programa Posgrad Engn Ciencia Mat PIPE, Curitiba, Parana, Brazil Athlone Inst Technol, Mat Res Inst, Athlone, Ireland Ctr Univ Volta Redonda UniFOA, Volta Redonda, RJ, Brazil Univ Fed Parana, Programa Posgrad Engn Mecan, BR-81531990 Curitiba, Parana, Brazil Univ Tecnol Fed Parana, Programa Posgrad Engn Mecan & Mat, Curitiba, Parana, Brazil Univ Fed Campina Grande, Dept Engn Mat, Campina Grande, PB, Brazil Pontificia Univ Catolica Parana, Escola Politen, Dept Engn Mecan, Curitiba, Parana, Brazil Univ Estadual Paulista, Dept Fis, Campus Bauru, BR-17033360 Bauru, SP, Brazil Univ Estadual Paulista, Dept Fis, Campus Bauru, BR-17033360 Bauru, SP, Brazil Fundacao Araucaria: 685/2014 Fundacao Araucaria: 42466 CNPq: 307037/2014-2 CAPES: 1522225

Among titanium alloys with non-toxic elements, the Ti-25Nb-25Ta alloy has good elastic behavior for applications in osseous implants, biocompatibility, and excellent corrosion resistance. The present study aimed to better the biocompatibility characteristics of Ti-25Nb-25Ta alloy modifying its surface through Plasma Electrolytic Oxidation (PEO) treatment. The formed oxide coating is amorphous and composed of two distinct porous formations: smaller hole-shaped pores and larger volcano-like pores. The regions with the formation of smaller pores and in the hole shaped presented the highest atomic percentage of the chemical element phosphorus. Nanoindentation tests have shown that the hardness of the Ti-25Nb-25Ta alloy is slightly lower than the commercially pure grade 2 titanium (a material used as reference), while elastic modulus measurements of Ti-25Nb-25Ta presented more suitable values for implant application (lower values when compared with titanium reference). After PEO treatment there were significant mechanical surface improvements (increased fairly surface hardness and decreased elastic modulus) for application in osseous tissue. Despite the Ti-25Nb-25Ta alloy presented excellent characteristics for applications in hard biological tissues, the PEO treatment better its features. Keywords: Titanium alloy, Ti-25Nb-25Ta, nanoindentation, mechanical properties, Plasma Electrolytic Oxidation.

Nanotubes grown on titanium and its alloys can improve biocompatibility, surface wettability and corrosion resistance when compared to untreated materials. However, the tribological properties of these films are scarcely investigated. In this study, hardness and elastic modulus pure titanium and Ti-35Nb alloy were analyzed, while tribological properties of these materials were compared with those of nanotube films grown on Ti-35Nb alloy. The Ti-35Nb alloy, composed of alpha and beta phases, presented the higher hardness (3.7 GPa) and the lower elastic modulus (96 GPa) than the pure alpha‑titanium (2.3 GPa and 145 GPa, respectively). The coefficient of friction of the alloy was approximately 1.3, which was higher than that of titanium (~1.05). Analyses of the worn tracks revealed abrasive and adhesive wear mechanisms occurring in both titanium and Ti-35Nb alloy. However, the presence of beta phase was responsible for the strongest adhesion wear and the highest wear rate of the Ti-35Nb alloy. The nanotube films with approximately 1.0 μm thick were produced through controlled anodization. The tubes diameters were random; their composition was a TiO2 and Nb2O5 crystalline phases mixture. In reciprocating sliding tests, nanotubes were compacted on the surface, being damaged on the outer part of the film. However, the wear rate of surfaces with nanotube films was only 42% [(0.055 ± 0.012)·10−3 mm3/Nm] the value measured for the Ti-35Nb substrate [(1.661 ± 0.129)·10−3 mm3/Nm]. To summarize, the Ti35Nb alloy were more suitable than titanium, regarding mechanical properties, for use in bone implants; moreover, its tribological performance was enhanced through a lubricating effect provided by oxide nanotube films grown on it.

Made available in DSpace on 2018-11-26T17:51:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-08-01 Fundacao Araucaria Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Nanotubes grown on Ti and its alloys have been extensively investigated for the biomaterials applications, since these structures improve the surface biocompatibility and the corrosion resistance due to oxide formation. Some researchers showed that the microstructure of the pure Ti affect the morphology of nanotubes grown by anodic process. However, this subject is rarely investigated for nanotubes grown on Ti alloys. In the same way, nanostructured films formed by concomitant regions of tubes and lamellar structures hardly ever were reported. Investigations concerning these topics are required once beta titanium alloys are suitable candidates to replace the pure Ti and Ti-Al-V alloys for biomedical applications. Beta alloys composed of non-toxic elements (Nb, Ta, Mo) are biocompatible and have an excellent mechanical properties and corrosion resistance. The present work investigated questions regarding to the effect of microstructure of Ti-10Nb alloy on morphology of nanostructured film growth by anodization. The morphology, thickness, composition and atomic arrangement (amorphous/crystalline) of formed oxides, and the contact angle of anodic film were investigated. The X-ray diffraction patterns and SEM image show that the Ti-10Nb alloy is composed by alpha (hcp) and beta (bcc) phases. SEM and TEM techniques revel that self-organized nanotubes grew on alpha phase, whereas a lamellar structure with transversal holes grew on beta-phase. Crystalline oxides are formed at oxide-metal interface, as indicated by X-ray diffraction patterns. However, the tubes and lamellas grown over the compact oxide are amorphous, as-prepared and annealed at 230 degrees C for 3 h, as showed by SAED patterns. The nanostructured films annealed at 430 degrees C and at 530 degrees C were damaged. A few changes were observed in XRD patterns of film annealed at 230 degrees C while the morphology held similar as the unannealed film. Finally, the presence of phosphorus ions incorporated into the anodic layer makes the surface hydrophilic, since a similar nanostructured film without phosphorous incorporation results hydrophobic. (C) 2018 Elsevier B.V. All rights reserved. Univ Fed Parana, Programa Posgrad Engn & Ciencia Mat PIPE, BR-81531990 Curitiba, Parana, Brazil Pontificia Univ Catolica Parana, Escola Politecn, Dept Engn Mecan, BR-80215901 Curitiba, Parana, Brazil Univ Tecnol Fed Parana, Programa Posgrad Engn Mecan & Mat, BR-81280340 Curitiba, Parana, Brazil Univ Estadual Paulista, Lab Anelasticidade & Biomat, Dept Fis, BR-17033360 Bauru, SP, Brazil Univ Fed Parana, Dept Fis, BR-81531990 Curitiba, Parana, Brazil Univ Estadual Paulista, Lab Anelasticidade & Biomat, Dept Fis, BR-17033360 Bauru, SP, Brazil Fundacao Araucaria: 685/2014 Fundacao Araucaria: 42466

Made available in DSpace on 2020-12-10T19:47:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-25 LORXI at UFPR, Brazil Hydroxyapatite (HA) is a bioactive calcium phosphate capable of enhancing the implant/bone connection improving osteoconductivity and osseointegration process. However, the HA presents mechanical properties limiting its application. A good way to resolve this limitation is to combine the excellent biological properties of HA with materials with suitable mechanical behavior, like Ti-25Nb-25Ta alloy. The Ti-25Nb-25Ta alloy is cornposted by non-toxic and corrosion-resistant elements, presenting good biological compatibility. In this work, Plasma Electrolytic Oxidation (PEO) (using direct current-DC) was applied in conventional mode and Two-Step PEO aiming to produce a porous coating containing HA. It was not possible to produce a satisfactory coating applying conventional PEO due to successive spalling during the oxidation process. Adding a pretreatment to the conventional PEO changed the process to Two -Step PEO allowing to form a porous coating containing HA. The pretreatment was made by PEO using phosphoric electrolyte to produce a pre-coating. After that, the pre-coating was re-oxidized with calcium/phosphorus electrolyte. The Two -Step oxidized surface presented well-known good characteristics to applications in osseous implant devices such as porous formation, roughness in the micrometrical range, surface containing calcium and phosphorus, bioactive crystalline titanium oxide, and well adhered HA formation. However, the coating morphology and chemical composition of pre-coating and Two Step oxidized surfaces were not uniform. The non-uniformity of the Two -Step oxidized surface follows a similar non-uniformity pattern of the pre-coating surface. Two distinct morphologies were identified on the Two-Step oxidized surface: a velvety morphology with HA formation and a highly porous morphology. Regarding the Ti-25Nb-25Ta alloy, the Two-Step oxidation produced an adhered coating with porous apatite distribution interspersed with calcium-rich porous oxide. Univ Fed Parana, Postgrad Program Mat Engn & Sci PIPE, Curitiba, Parana, Brazil Athlone Inst Technol, MRI, Athlone, Ireland Univ Tecnol Fed Parana, Dept Mech Engn Curitiba, Curitiba, Parana, Brazil Univ Fed Parana, Dept Phys, Curitiba, PR, Brazil Univ Estadual Paulista, Dept Mat & Technol, Guaratingueta, SP, Brazil Univ Estadual Paulista, Dept Mat & Technol, Guaratingueta, SP, Brazil LORXI at UFPR, Brazil: FINEP CT-INFRA 793/2004 LORXI at UFPR, Brazil: 3080/2011

Well-adhered nanotube arrays were produced through the anodizing technique on a Ti-25Nb-25Ta alloy and tribo-mechanically evaluated by nanoindentation and nanoscratch tests. Disregarding substrate effects, the hardness of the nanotube arrays layer was 0.7 ± 0.1 GPa and elastic modulus was

International audience; Surface modification by deposition of hard coatings is a way to overpass the poor wear resistance of some metallic materials and one potential material is the Diamond-Like Carbon (DLC). We investigated the wear behavior, and the adhesion of the DLC deposited on a Ti6Al4V (Ti64) alloy after Surface Mechanical Attrition Treatment (SMAT). The SMAT was applied using 100Cr6 steel balls, and the DLC was deposited through the sputtering method. The nano-hardness was evaluated using a MTS Nano Indenter XP. The adhesion of the DLC was evaluated using a CSM Revetest, and the wear tests was performed in a reciprocating linear tribometer from CSM Instruments. The mean wear rate for the Ti64 was 437x10-6 mm3/N/m against 5x10-6 mm3/N/m for the Ti64+SMAT+DLC. The SMAT reduced the wear rate of the DLC coating, showing that the SMAT might be a viable treatment with promising results regarding the DLC wear resistance.

Orthopedic implants still have limitations regarding their durability, despite being in use for over fifty years. Particles arising from wear due to the relative motion of their surfaces remain responsible for aseptic failure. This paper presents a device to be coupled with a reciprocal linear tribometer to reproduce the ex vivo wear of biomaterials, allowing the measurement of force and coefficient of friction. The device consists of a structure connected to the tribometer that transforms its reciprocal linear motion into one that is oscillatory for the mechanical assembly that contains the samples to test the desired biomaterials. The tribological pair used for testing consisted of Ultra High Molecular Weight Polyethylene (UHMWPE) in conjunction with the austenitic stainless steel AISI 316L in dry lubrication. The results showed that the values of the coefficient of friction in the linear mode and oscillatory mode and the UHMWPE life curve in the oscillatory mode were consistent with those cited in the literature for tests in a dry lubrication environment. Moreover, the UHMWPE sample life curve showed a reduction in the wear rate that can be explained by the preponderance of a wear mechanism over the others. The volumetric wear showed an increase with the number of cycles.

Made available in DSpace on 2018-12-11T17:13:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-07-01 The Ti-Nb alloy binary system has been widely studied with regard to biomedical applications due to the high biocompatibility and excellent mechanical properties of the alloys. Regarding physicalchemical stability, Ti-Nb alloys maintain the properties of Ti metal, which is highly resistant to corrosion in aggressive media due to a spontaneous stable oxide layer (TiO2) formed on its surface. The objective of this study was to evaluate the corrosion resistance of the Ti-40Nb alloy in artificial blood. The thermodynamic stability was studied using the open circuit potential technique and the corrosion resistance was assessed by potentiodynamic measurements and electrochemical impedance spectroscopy. The electrochemical results indicated that the Ti-40Nb alloy has high corrosion resistance and good thermodynamic stability, with an OCP of around -485 mV, and the alloy remained electrochemically stable in potentiodynamic conditions with initial and final potentials of -1.0 V to +2.0 Vsce, respectively, in low current densities (∼μA cm-2) with an absence of hysteresis, aspure Ti. The results obtained showed that this specific alloy has the potential to be used in biomedical applications. Laboratory of Biomaterials and Electrochemistry Federal University of Paraná UFPR Physics Department Laboratory of Surface Mechanical Properties Federal University of Paraná UFPR UNESP School of Engineering Materials and Technology Department Guaratinguetá Campus Department of Mechanical Engineering Laboratory of Biomaterials and Electrochemistry Federal University of Paraná UFPR UNESP School of Engineering Materials and Technology Department Guaratinguetá Campus

Niobium plates were electrochemically treated by Plasma Electrolytic Oxidation (PEO) with electrolytes containing phosphorous and/or calcium. Three different electrolyte and experimental parameters were used forming three different surfaces. Film morphology, thickness, and chemical composition were analyzed by scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). A profilometer and the sessile drop technique measured the average surfaces roughness (Ra) and contact angles respectively. X-ray diffraction technique (XRD) analyzed the oxide crystallinity, and scratch tests evaluated the film adhesion. All oxidized surfaces presented pores, without observed cracks. Comparing the different experimental conditions, films obtained with phosphoric acid (P100) show superficial pores, phosphorus incorporation, high hydrophilicity, non-crystalline oxide formation, and good scratch resistance. Films treated with calcium acetate electrolyte (Ca100), compared to P100 exhibit smaller size pores and film thickness, smaller hydrophilicity, and lower scratch resistance. They also demonstrated higher oxide crystallinity, calcium incorporation, and pores interconnections. When the PEO was executed with a blended electrolyte containing calcium acetate and phosphoric acid (Ca50P50) the formed films presented the highest thickness, high phosphorus incorporation, and the lowest contact angle compared with other films. In addition, the pores size, the scratch resistance, calcium incorporation, and oxide crystallinity present intermediate values compared to P100 and Ca100 films. Film crystallinity seems to be influenced by calcium incorporation, whereas, hydrophilicity is phosphorus amount dependent. The pores amount and their interconnections reduced the scratch resistance. Surface features obtained in this work are largely mentioned as positive characteristics for osseointegration processes.

Plasma electrolytic oxidation (PEO) of niobium plates were done electrochemically in two steps with electrolytes containing phosphorous and calcium being observed the formation of crystalline apatite. All samples were submitted to a first step of PEO using an electrolyte containing phosphate ions. The second oxidization step was made using three different electrolytes. Some samples were oxidized by PEO in electrolyte containing calcium, while in other samples it was used two mixtures of phosphoric acid and calcium acetate monohydrate solutions. Three different surface layers were obtained. The morphology and chemical composition of the films were analyzed by scanning electronic microscopy (SEM), and energy dispersive spectroscopy (EDS) respectively. It was observed that all samples submitted to two-step oxidation shown porous surface and a calcium and phosphorus rich layer. Average surface roughness (Ra) was measured by a profilometer remaining in the sub-micrometric range. The contact angle by sessile drop technique, using 1μL of distilled water was performed with an optical goniometer. It was verified a higher hydrophilicity in all surfaces compared to the polished niobium. Orthorhombic Nb2O5 was identified by XRD in the oxide layer. Crystalline apatite was identified by XRD in surfaces after the second oxidation made with the Ca-rich electrolyte and a mixture of an electrolyte richer in Ca compared to P. These results indicate that a two-step oxidized niobium surface present great features for applications in the osseointegration processes: favorable chemical composition that increase the biocompatibility, the formation of crystalline niobium pentoxide (orthorhombic), high hydrophilicity and formation of crystalline calcium phosphate (apatite) under adequate electrolyte composition.

Anodic oxidation is a technique widely used to improve the bioactivity of Ti surface. In this study, micro-arc oxidation (MAO) was used to obtain an anodic film incorporating Ca and P ions to evaluate the effect of heat and hydrothermal treatment on the mechanical and in vitro bioactivity properties of these new layers. The MAO process was carried out using (CH3COO)2Ca·H2O and NaH2PO4·2H2O electrolytes under galvanostatic mode (150 mA/cm2). The thermal treatments were made at 400 °C and 600 °C in air atmosphere while hydrothermal treatment was made in an alkaline water solution at 130 °C. These surfaces presented desired mechanical properties for biomedical applications owing to the rutile and anatase phases in the anodic film that are more crystalline after thermal treatments; which provided an increase in hardness values and lower elastic modulus. The dry sliding wear resistance increased by performing thermal treatments on the surfaces with one condition still maintaining the film after the test. Bioactivity was investigated by immersion in simulated body fluid during 21 days and hydroxyapatite was formed on all samples. Finally, lower values of contact angle were obtained for heat treated samples. yes

Porous TiO 2 coatings were produced on commercially pure Ti substrates by micro-arc oxidation (MAO) in 1.0 M H 2 SO 4 electrolyte for different anodizing times. Their mechanical properties were assessed by means of instrumented indentation, XRD residual stress measurements and scratch resistance tests. The rutile/anatase ratio increased from ~ 0 up to 84% in the 10–360 s anodizing time range, with further increase of coating thickness, porosity and roughness. Titania coatings produced for 180 and 360 s had poor adhesion and uneven surfaces with spontaneous detachment from the substrate. Coating hardness ranged from 3.5 up to 4.0 GPa (close to Ti), whereas the effective elastic modulus varied from 110 up to 120 GPa (19% lower than Ti), regardless of the substrate effects. Coatings exhibited tensile residual stresses, while the substrate compressive stress increased forming a plateau at about − 110 MPa for anodizing time longer than 60 s. The presence of such hardened layer beneath the interface improved the coating integrity in the scratch tests under the severe tribological condition, thereby increasing about tenfold the detachment critical load for the samples prepared in the 10–60 s MAO time range. Therefore, the 60 s anodizing time can be a useful reference line for producing mechanically resistant porous titania coatings.

Titanium and its alloys are widely used as implants due to their excellent mechanical properties, corrosion resistance and biocompatibility. TiO2 nanotubes have been studied as surface treatment to increase the specific area and to improve osseointegration. However, the thermodynamic stability and bioactivity of these nanostructures must be evaluated. The objective of this research was to obtain nanotubes oxides on Ti6Al4V alloy and to analyze the electrochemical stability in physiological solution at 37 °C and the bioactive response of the biomaterial. The nanotubes were obtained by potentiostatic anodization. The morphology of the oxides was evaluated by scanning electron microscopy. The chemical characterization was analyzed by energy dispersive spectroscopy and x-ray photoelectron spectroscopy techniques. The electrochemical stability was analyzed by open circuit potential (OCP) and the bioactivity by biomimetic test in a simulated body fluid (SBF) solution. The OCP of the nanotubes oxides was shown to be more noble and stable than the compacted oxides. The biomaterial covered with theses oxides showed sealing by Ca and P after 30 d immersion in artificial blood. And after 15 d of immersion in SBF, the hydroxyapatite could be seen on the non-sealed nanotubes. TiO2 nanotube layers could improve the superficial chemical stability and also the osseointegration process.