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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.

The following chapter gives an overview of the anodic layers and nanotubes produced with plasma electrolytic oxidation. An introduction into the mechanisms involved in producing these nanofilms, such as the required processing parameters including voltage, current, and time, are discussed. In addition to an examination into the relation and the requirements for a good interface between the implant using these nanofilms and the bone, we also investigate and discuss the available commercial implants employing nanofilms. Commercial applications have enormous potential and are an area of interest for future work. Finally, we discuss the mechanical properties and the improvements obtained on these nanofilms by the scientific community.

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.

The use of titania (TiO2) nanotubes is becoming one of the most attractive techniques as surface treatment for implants due its combination of morphology (that accelerates osteoblast adhesion and proliferation), bioactivity and possibility of being use as a drug vehicle. Anodic oxidation is one of the cheapest and simplest approaches to obtain highly ordered nanotubes. Parameters such as applied potential, reaction time and fluoride containing in the electrolyte define the nanotubes morphology. However, the mechanical properties of the nanotubes layer do not have been completely elucidated and they play a crucial role in the implant long term stability. The objective of this research was to obtain TiO2nanotubes using anodic oxidation and to determine their elastic modulus and hardness. The TiO2nanotubes layer was obtained in a fluoride containing electrolyte for 1 hour, one group at 15 V and another one at 25 V. The TiO2nanotubes morphology was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The elastic modulus and hardness were evaluated by nanoindentation experiments using a spherical tip. SEM images showed highly ordered nanotubes on all titanium surfaces and it was observed that the nanotubes diameters are directly related with the applied potential. Nanotubes diameters are 66 ± 9 nm and 131 ± 22 nm for nanotubes obtained at 15 V and 25 V, respectively. Nanoindentation test results showed a decrease in the elastic modulus comparing with titanium reference and these values approach to cortical bone elastic modulus. These results demonstrate that it was possible to obtain a homogeneous TiO2nanotubes layer that has mechanical properties adequate to improve implant long-term stability.

There are various surface treatments used to modify titanium surfaces to render it bioactive. In this study commercially pure titanium surfaces (cp Ti), grade 2 were modified by acid etching (AE) and anodic oxidation (OA) in order to evaluate the bioactivity in vitro of these surfaces using the simulated body fluid (SBF). The AE was realized using a mixture of acids and AO using 1 mol.L-1 sulfuric acid. The anodic films were obtained under potentiostatic mode, during 60s using as anode a bar of titanium. All the surfaces that means cp Ti, AE and AO were analyzed concerning to morphology, rugosity, structural changes before in vitro bioactivity tests. It was observed by scanning electron microscopy (SEM) that all surfaces presented different morphologies: those with AE showed a surface with peaks and rounded valleys, with Ra = (564±80) nm, the oxidized surfaces with sulfuric acid showed a morphology with small pores uniformly distributed over the surface and Ra = (177±0,02) nm. X-rays diffraction results showed the presence of titanium hydride on the samples with AE and the anatase and rutile phases on the anodic films after heat treatment at 600°C/1h. Bioactivity tests in vitro using SBF at 37°C showed that small aggregates containing Ca and P were observed on surfaces with AE after 30 days soaked in SBF and the surfaces oxidized were fully coated with an apatite layer, identified by SEM.

In recent years, many surface modification processes have been developed in order to induce the osseointegration on titanium surface and thus to improve the implants' biocompatibility. In this work, Ti surface has been modified by shot blasting followed by anodic oxidation process in order to associate the good surface characteristics of both processes to obtain a rough and porous surface able to promote the titanium surface bioactivity. Commercially pure titanium (grade 2) plates were used on the surface treatments that were as follows: Shot blasting (SB) performed using alumina (Al2O3) particles, and anodic oxidation (AO) using NaOH electrolyte. The morphology, structural changes and the open-circuit potentials (OCP) of the surfaces were analyzed. It can be observed that an increase on the roughness of the blasted surface and a rough and porous surface happens after the AO process. The anodic film produced is thin and followed the blasted surface topography. It can be observed that there are small pores with regular shape covering the entire surface. X-ray diffraction results showed the presence of the anatase and rutile phases on the blasted and anodized surface after heat treatment at 600 °C/1 h. Concerning electrochemical measurements, when the different samples were submitted to open-circuit conditions in a physiological electrolyte, the protective effect increases with the oxidation process due to the oxide layer. When the surface was blasted, the OCP was more negative when compared with the Ti surface without surface treatments.

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.

Titanium has been used in the production of dental implants and orthopedic prostheses due to the low tendency to corrosion and good biocompatibility. Meanwhile, the surface of titanium is not bioactive. Several surface treatments have been developed to make the surface of such metals bioactive. The aim of this work was to evaluate two of these modification processes in commercially pure titanium grade 2, both of them using NaOH solutions: the anodic oxidation and the alkali treatment. The surface morphology was evaluated by SEM/EDS, the crystal structure by XRD, and the mechanical properties and scratch resistance by instrumented indentation. The anodic oxidation (AO) was carried out using NaOH electrolyte 0.1 mol/L and constant current density of 150 mA/cm² for one minute. The alkaline treatment (AT) was performed by soaking the Ti sample in NaOH 5 mol/L solution at 60 °C for 24 hours; after this, the sample was heat treated at 600 °C for one hour in atmospheric air. The AO produced a TiO2 layer on Ti, whereas a thin sodium titanate layer was obtained by AT. Each surface modification resulted in a specific morphology, but both of them presented the increase in roughness as a common characteristic. The alkali treated Ti surfaces showed the lowest elastic modulus and hardness values. The largest increase in hardness between the treated surfaces was obtained for Ti after anodic oxidation. Scratch test indicates that the TiO2 film from AO has higher strength to tangential loading than the Ti substrate. In addition, for the Ti submitted to AT, the scratch test indicates that the modified surface layer has a poor adhesion with the substrate. Based on these results it is possible to conclude that, using NaOH solutions, Ti surfaces treated by anodic oxidation present improved mechanical properties than the alkali-treated ones.

Hydrogen diffusion is a well-known cause of embrittlement in titanium devices, however the use of H-implantation has been investigated to enhance the titanium biocompatibility and bioactivity. In the present study, effects of the hydrogen ion implantation on Ti and nitrided Ti through glow discharge are reported, focusing the surface tribo-mechanical response at nanoscale. The structural and chemical features were also evaluated, before and after the hydrogen implantation, by NRA, XRD, XPS, SEM and EDS. The hydrogen implantation increased the H content on Ti up to two times, promoted the formation of δ-TiH precipitates and changed the Ti oxidation state, without affecting hardness and elastic modulus. Hydrogen implanted after nitriding produced blisters, formed by H accumulation near the surface region of the nitride layer due to its barrier effect. A “denitriding” process at very near surface region was also observed after the hydrogenation. Nitriding increased Ti hardness by 120% and elastic modulus by 18%. Hydrogenation became the nitrided Ti harder and stiffer, increasing the hardness and elastic modulus by 180% and 41%, respectively. In both Ti and nitrided Ti, nanotribological tests pointed out that the surface became brittle after hydrogenation. On the other hand, the H-implantation had negligible effects on the Ti and nitrided Ti tribological behaviors in the tests performed under severe dry conditions.

Surface modification processes such as the alkali-heat treatment (AHT) can be employed in order to improve the titanium osseointegration with living tissues. Sodium titanate films produced by AHT presented high in vitro bioactivity when soaked in simulated body fluid. In order to produce bioactive surfaces and also improve the tribo-mechanical response of AHT films grown on Ti, samples were submitted to H, N and O low energy ion implantation (glow discharge—GD) at different working conditions. AHT film with thickness of 1 μm was produced on untreated Ti and had low hardness (0.012 GPa) as well as low critical nanoscratch resistance (5.5 mN). For the studied periods up to 30 days no in vitro bioactivity was observed on the only GD worked surfaces. Hydrogenated and nitrided Ti became bioactive after the AHT, but the film thickness decreases in comparison to untreated GD Ti. At the same time its critical nanoscratch resistance and bioactivity degree decrease. However for GD oxidized sample an AHT film was not formed. From these results it can be suggested that plenty availability of metallic Ti at the surface is required to grow AHT films with good bioactivity response.

The oxide layers of electrolytic oxidized titanium (Ti) were characterized using Ti L 2,3 and O K edge X-ray absorption. The spectra show that the structure of the oxide layers that are formed during a 1 min treatment are dependent on the concentration of the electrolyte (H 2 SO 4 or Na 2 SO 4 ) with which the Ti surface was treated, and also on the magnitude of the potential that was applied during the anodic oxidation process (100 V or 150 V). It is found that a potential of 150 V and an electrolyte concentration of 0.5 M or 1.0 M produces a layer of TiO 2 having rutile crystal structure.

Although titanium metal has been used intensively in the last years as biomaterial in the medical and dental areas its surface is not bioactive. In this work, titanium metal was submitted to an alkali treatment in order to make the metal surface bioactive. The samples were submitted to alkaline treatment (AT) using NaOH 5M aqueous solution at 60°C for 24 h and after that they were heated thermically to stabilize the layer obtained with AT. The bioactivity of the samples was evaluated soaking them into the simulated body fluid (SBF) at 36,5°C for 28 days. The morphological, structural changes and the electrochemical characterization were analyzed using scanning electron microscopy, x-ray diffraction and electrochemical impedance spectroscopy (EIS), respectively. It was verified that after AT plus heat treatment (HT) a sodium titanate layer was formed on the samples surface and after the bioactivity tests an apatite layer was formed. Impedance analysis show that the resistance of film on Ti is high and this value increases when the sample is soaked in SBF. It means that the apatite (HPA) film is occurring and the value of the capacitance with the presence of the HPA film (Cp) values indicate that the film maintain a compact and uniform characteristics.

Anodic oxidation is a promising technique to become titanium surfaces bioactive, by simultaneously changing the surface morphology, structure and chemical properties. Calcium and phosphorus based electrolytes were used to produce anodic films on c.p. Ti with two different current densities, 150 mA/cm2 and 300 mA/cm2. Morphology and structure were examined by SEM, EDS and XRD, and elastic modulus and hardness of the surfaces by instrumented indentation. Besides rutile and anatase TiO2 phases, hydroxyapatite was also identified on the films, as well as the segregation of very soft Ca and P-rich zones. Low values for the elastic modulus and hardness values close to the Ti corroborate to the applicability of Ca and P based TiO2 anodic films in biomedical titanium implants.

The aim of this work was to investigate the mechanical properties of the titanium The aim of this work was to investigate the mechanical properties of the titanium anodic films (TiO 2 ) produced by anodic oxidation under galvanostatic conditions, using a 1.4M phosphoric acid electrolyte, with different current densities (J) on commercially pure titanium (cp-Ti). The morphology of the oxide films were observed by scanning electron microscopy (SEM), whereas the composition of the film was determined by Raman spectroscopy. Porosity, average roughness (Ra) and thickness of the TiO 2 films increased with the applied J. Hardness and elastic modulus were measured by instrumented indentation technique, and the influence of the substrate was corrected using analytical models. The anodic films presented higher hardness and lower elastic modulus values compared with the cp-Ti.

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

Two different Ti oxide films produced by anodic oxidation were submitted to in vitro bioactivity and cell culture tests. The oxide films were produced in 1.0M H2SO4/150V and 1.0M Na2SO4/100V. Surfaces were found to be homogeneous and rough, with the presence of pores. Both oxide films presented anatase and rutile phases. Ti oxide film produced in Na2SO4 was rougher than the film grown with H2SO4 and composed of a rutile-rich phase. Both films were constituted by TiO2 and Ti2O3 oxides. Despite the differences observed, after 7 days, a calcium phosphate layer was precipitated on both surfaces. Indeed, these two treatment conditions seem to be efficient to spread and attach osteoblast-like cells within 4h.

Titanium oxide films produced on commercially pure Ti by anodic oxidation with different voltages were analyzed. Anodic oxidation was carried out at room temperature using 1.4 M H 3 PO 4 electrolyte and a platinum counter-electrode, in potentiostatic mode under the following conditions: 50 V, 100 V, 150 V, 200 V and 250 V. It was observed that porous titanium layers were formed at all voltage values but morphological differences were observed. Initially, the film was thin but with increasing voltage it broke down locally and porous regions became evident due to the dielectric breakdown. The porosity and the pore size increased with the increasing voltage. The surface morphology in samples formed with 200 V had substantially different porous structures than those formed with other voltage values. The anodic film surface displayed pores and craters formed on the relatively flat ground oxide surface. AFM images showed that higher voltages produced thicker titanium oxide films.

Osteoblast adhesion on metallic titanium coated with anodic films was evaluated. The anodic oxidation treatment was carried out on commercially pure-titanium (cp-Ti) substrate under the following conditions: 1.0M H2SO4/150V and 1.0M Na2SO4/100V. Osteoblast cells were cultured onto the samples for 4 hours. The morphologies of both Ti anodic films and cells were observed by scanning electron microscopy (SEM). The oxide films are rough with porous structure. Statistical differences in average surface roughness (Ra) values are found among both anodic films and substrate (abraded cp-Ti), measured by contact profilometry. The oxide films prepared in H2SO4 had greater contact angle, whereas there is no statistical significance between the values for the Ti anodic films produced in Na2SO4 and the substrate surface. Despite the some differences in morphology, roughness and contact angle between the treated and non-treated samples, cell morphologies were similar on all surfaces after 4h of culture. Further, was not clearly observed a correlation between the surface characteristics with cell behavior.

Bone formation around a metallic implant is a complex process that involves micro- and nanometric interactions. Several surface treatments, including coatings were developed in order to obtain faster osseointegration. To understand the role of these surface treatments on bone formation it is necessary to choose adequate characterization techniques. Among them, we have selected electron microscopy, profilometry, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) to describe them briefly. Examples of the potentialities of these techniques on the characterization of titanium for biomedical applications were also presented and discussed. Unfortunately more than one technique is usually necessary to describe conveniently the topography (scanning electron microsocopy, profilometry and/or AFM) and the chemical state (XPS) of the external layer of the material surface. The employment of the techniques above described can be useful especially for the development of new materials or products.

Titanium (Ti) and Ti alloys are widely used for the manufacture of dental implants and orthopedic prostheses due to suitable properties such as zero toxicity, good mechanical properties and corrosion resistance. The addition of niobium (Nb) to commercially pure Ti (cp-Ti) can results in elastic moduli lower than Ti. So in this work the elastic modulus of Ti-Nb alloys with 10% and 20%, in weight submitted to anodic oxidation (AO) has been investigated to verify how to obtain elastic modulus closer to bone. The AO has been realized using phosphoric acid as electrolyte applying a voltage of 250V/60s. Elastic modulus values were obtained using instrumented indentation technique. The results indicated that it was possible to obtain Ti-Nb alloys with lower elastic modulus values compared with cp-Ti.

The combination of shot blasting (SB) and micro-arc oxidation (or anodic oxidation--AO) in titanium surfaces was shown to provide enhanced conditions for cell differentiation and osseointegration than those provided by SB or AO alone. This study associated both methods aiming to attain titania layers on Ti with adequate tribo-mechanical features for bone implants. SB was performed using alumina particles, and titania layers were grown by AO using a CaP-based electrolyte. Mechanical properties and scratch resistance were characterized at nanoscale by instrumented indentation and nanoscratch, and correlated with morphological and microstructural changes (XRD, SEM, EDS, AFM, and profilometry). Analytical methods were employed to correct roughness and substrate effects on the indentation results. CaP-containing TiO2 layers were produced on AO and SB + AO. The latter presented small pore size and inhomogeneous layer thickness and Ca/P ratios, caused by the non-uniform surface straining by SB that affects the oxide growth kinetics in the electrochemical process. Elastic modulus of SB + AO layer (37 GPa) were lower than the AO one (45 GPa); both of them were smaller than bulk Ti (130 GPa) and close to bone values. The hardness profiles of AO and SB + AO were similar to the substrate ones. Because of the improved load bearing capacity and unique layer features, the critical load to remove the SB + AO titania coating in scratch tests was three times as much or higher than in AO. Results indicate improved mechanical biocompatibility and tribological strength of anodic titania layers grown on sand blasted Ti surfaces.

Prostheses are subject to various forms of failing mechanisms, including wear from ordinary patient motion. Superficial treatments can improve tribological properties of the contact pair, minimizing wear and increasing prostheses lifetime. One possibility is the diamond-like carbon (DLC) coating, where Carbon is deposited with variable ratio of sp(2)/sp(3) structures, leading to an increase in surface hardness. So in this research Ti6Al4V samples were coated with DLC using sputtering process to evaluate the debris release. The Ti6Al4V and Ti6Al4V plus DLC coating surfaces were analyzed using Raman spectroscopy and instrumented indentation (hardness). The wear behavior was tested using a reciprocating linear tribometer. The wear rate was smaller in the coated samples, producing less debris than the untreated Ti6Al4V alloy. Debris morphology was also evaluated, using scanning electronic microscopy, and it was observed that debris size from the coated samples were bigger than those observed from the uncoated Ti6Al4V alloy, above the size that generally triggers biological response from the host.

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.

Rough and porous titanium oxide layers, which are important features for improving the osseointegration of Ti implants with bone tissues, are obtained through the technique of anodic oxidation. The thicknesses of such coatings are typically in the order of micrometers, and their mechanical characterization can be assessed by instrumented indentation, provided that the composite nature of the surface is considered. Titania anodic layers were produced on Ti under galvanostatic mode using Ca–P-based electrolytes (a mixture of (CH3COO)2Ca⋅H2O and NaH2PO4⋅2H2O), employing current densities ( J ) of 150 mA/cm2 and 300 mA/cm2. The structure and morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy with electron dispersive X-ray spectroscopy (SEM/EDS), and profilometry, and the chemical features were characterized by X-ray photoelectron spectroscopy (XPS). TiO2 layers presented the crystalline phases rutile and anatase, and incorporation of Ca and P presented as a calcium phosphate compound. The porosity, roughness, and thickness increased with J . Analytical methods were employed to obtain the modified layers’ elastic modulus and hardness from instrumented indentation data, deducting the substrate and roughness effects. The elastic moduli were about 40 GPa for both values of J , which are similar to the values for human bones (10–40 GPa). The hardness decreased with indentation load, varying from 5 GPa at the near surface to 1 GPa at the layer–substrate interface. Such hardness behavior is a consequence of the surface brittleness under normal loading. Additional scratch tests using an acute tip indicated that the layer integrity under shear forces was 220 mN (J=150 mA/cm2) and 280 mN (J=300 mA/cm2). TiO2 layers produced with both current densities presented good results for in vitro bioactivity tests using simulated body fluid (SBF) solution, which can be attributed to a combined effect of the microstructure, layer porosity, and hydroxyl radicals in plenty at the near surface.

Alkali-heat treatment (AHT) is a simple and practical method to make titanium surfaces bioactive. Hydroxyapatite nucleates on Ti when in contact with body fluids due to the presence of a thin sodium titanate film produced by the AHT. This method was proposed more than a decade ago and it has been widely investigated at varied scopes. However, there is still little information about the mechanical properties of this film. In this work, the tribo-mechanical behavior of films produced by alkali treatment (AT) and AHT on Ti is investigated using instrumented indentation technique. The films were also characterized by TF-XRD, SEM, EDS and in vitro bioactivity tests. Analytical methods were employed to obtain the mechanical properties of the film from instrumented indentation data. The heat treatment subsequent to the alkaline processing increased the film elastic modulus from 1.7 GPa to 2.8 GPa, the hardness from 12 MPa to 20 MPa and the critical load for scratch test from 1.5 mN to 5.5 mN. Despite the overall improvement in the film bioactivity and tribo-mechanical behavior, the AHT elastic modulus is only 2% of the pristine Ti whereas hardness is less than 1%. This information must be considered for implant design purposes.

The aim of this work was to evaluate the ability of a bioactive glass-ceramic to induce the apatite nucleation on the titanium oxide layer produced by micro-arc oxidation. “ In vitro ” tests were carried out on a simulated body fluid solution in two different manners: one group was soaked in the SBF, while the other group was soaked together with the bioactive glass-ceramic. Results revealed that after 7 days, the specimens soaked in SBF were covered with an amorphous calcium phosphate layer, while the specimens soaked in SBF plus glass-ceramic formed a crystalline apatite layer, suggesting thus, that the glass-ceramic provides silanol groups that accelerated the hydroxyapatite apatite precipitation on the anodic TiO 2 layer.