Search

This review article deals with the design of bioactive calcium phosphate coatings deposited on metallic substrates to produce bone implants. The bioceramic coating properties are used to create a strong bonding between the bone implants and the surrounding bone tissue. They provide a fast response after implantation and increase the lifespan of the implant in the body environment. The first part of the article describes the different compounds belonging to the calcium phosphate family and their main properties for applications in biomaterials science. The calcium to phosphorus atomic ratio (Ca/P)at. and the solubility (Ks) of these compounds define their behavior in a physiological environment. Hydroxyapatite is the gold standard among calcium phosphate materials, but other chemical compositions/stoichiometries have also been studied for their interesting properties. The second part reviews the most usual deposition processes to produce bioactive calcium phosphate coatings for bone implant applications. Plasma spraying is the main industrial process, but magnetron sputtering, pulsed laser deposition, electrospray deposition, electrophoretic deposition, and electrodeposition are also widely studied in academic and industrial research. The last part describes the main physicochemical properties of calcium phosphate coatings and their impact on the bioactivity of bone implants in a physiological environment.

This research work describes the impact of the surface mechanical attrition treatment (SMAT) on the microstructure of cobalt-chromium-molybdenum (CoCrMo), a biomedical alloy commonly used for orthopedic applications. This surface treatment induces crystalline phases transformations characterized by X-ray diffraction (XRD) and selected area electron diffraction (SAED). The corresponding structural changes are observed from cross-section images obtained by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the SMAT process induces the martensitic transformation of the CoCrMo alloy (from γ-fcc phase to ε-hcp phase) related to an important grain refinement due to twinning and sliding.

The skutterudite materials belonging to the CoSb3 family are widely studied for thermoelectric applications. They are typically used under vacuum, but applications under oxidizing environments are increasingly considered. The addition of ytterbium is known to enhance the thermoelectric properties of CoSb3, but the corresponding impact on the oxidation behavior of the skutterudite material is barely explored. For that purpose, the present research describes the oxidation behavior of Yb0.2Co4Sb12 under a flow of air at 800 K for 15, 50, 100, and 1000 hours. The oxidation treatment induces the growth of a surface layer made of three oxides in various amounts as a function of the oxidation time. The spinel oxide CoSb2O4/CoO·Sb2O3 and CoSb2O6 are observed from 15 hours of oxidation, whereas Sb2O4 is formed only from 100 hours of treatment. To assess the impact of ytterbium, the oxidation behavior of Yb0.2Co4Sb12 is compared to that of CoSb3 oxidized in the same experimental conditions. The results show that the low amount of ytterbium promotes the oxidation reactions of the skutterudite material. Nonetheless, the impact on the degradation of the material remains acceptable to use Yb0.2Co4Sb12 for thermoelectric applications under oxidizing environments.

A thermoelectric generator is a powerful system used to produce electricity by the action of heat. The development of nanostructured thermoelectric materials is widespread with the objective to improve their efficiency. However, if these materials are used at high temperatures under oxidative atmosphere (e.g., in air), they may suffer degradation in service, drastically decreasing their lifespan. This work investigates the oxidation behavior of an innovative skutterudite material made of cerium, iron, cobalt and antimony (Ce0.75Fe3CoSb12) either microstructured or nanostructured. For that purpose, several oxidation experiments are carried out under a flow of synthetic air at 650 K (15 h, 50 h and 100 h). The oxide layers formed on surface are observed, and their characteristics (chemical composition, thickness, structure) are compared to those obtained with microstructured Ce0.75Fe3CoSb12 samples. As a result, it is observed that the nanostructuring of the skutterudite materials slightly slow down the oxidation reactions in air. Consequently, the nanostructured Ce0.75Fe3CoSb12 is established to be a promising thermoelectric material for use in oxidative environments.

Everywhere on Earth, people are living longer and longer [...]

This review summaries more than three decades of scientific knowledge on electrodeposition of calcium phosphate coatings. This low-temperature process aims to make the surface of metallic bone implants bioactive within a physiological environment. The first part of the review describes the reaction mechanisms that lead to the synthesis of a bioactive coating. Electrodeposition occurs in three consecutive steps that involve electrochemical reactions, pH modification, and precipitation of the calcium phosphate coating. However, the process also produces undesired dihydrogen bubbles during the deposition because of the reduction of water, the solvent of the electrolyte solution. To prevent the production of large amounts of dihydrogen bubbles, the current density value is limited during deposition. To circumvent this issue, the use of pulsed current has been proposed in recent years to replace the traditional direct current. Thanks to breaking times, dihydrogen bubbles can regularly escape from the surface of the implant, and the deposition of the calcium phosphate coating is less disturbed by the accumulation of bubbles. In addition, the pulsed current has a positive impact on the chemical composition, morphology, roughness, and mechanical properties of the electrodeposited calcium phosphate coating. Finally, the review describes one of the most interesting properties of electrodeposition, i.e., the possibility of adding ionic substituents to the calcium phosphate crystal lattice to improve the biological performance of the bone implant. Several cations and anions are reviewed from the scientific literature with a description of their biological impact on the physiological environment.

The skutterudite CoSb3 is a well-known thermoelectric material widely used to produce electricity from heat. This material is commonly employed under vacuum but in a near future it is expected to be used at high temperatures under oxidative atmospheres, e.g. in air. The lifetime of the material may be affected by the oxidative environment, considerably limiting the use of the thermoelectric equipment. The present research describes the degradation mechanisms of CoSb3 from oxidation experiments carried out under a flow of synthetic air at 800 K. The skutterudite material is progressively oxidized after 15 h, 50 h, 100 h and 1000 h of treatment, producing three oxides on the CoSb3 surface (CoSb2O4/CoO·Sb2O3, Sb2O4 and CoSb2O6). These three oxides have different growth kinetics and they are produced in various amounts as a function of the oxidation time. Next, as a solution for an appropriate oxidation protection, this work explores the chemical vapor deposition (CVD) process named pack cementation to synthesize a protective coating on CoSb3. This process produces a surface layer made of aluminum antimonide (AlSb) and cobalt aluminide (Al9Co2). The oxidation experiments carried out on the coated CoSb3 highlight the protective properties of this innovative surface layer. The coating is a protective barrier against oxygen that keeps the CoSb3 substrate unaffected by the flow of air at 800 K for 1000 h. Consequently, pack cementation is an efficient process to synthesize a protective surface layer that makes CoSb3 usable under oxidative environments.

This work deals with the electrodeposition of calcium phosphate coatings on the surface of Fe-Mn-Si alloys which is designed for bone implant applications. Three different alloy compositions are considered (Fe-23Mn-5Si, Fe-26Mn-5Si and Fe-30Mn-5Si, all in wt pct). In order to explore the impact of hydrogen peroxide (H2O2) on the electrodeposition process, two different electrolytic solutions are studied, one that contains no H2O2 and the other that contains 9 vol pct H2O2. The physicochemical characterizations reveal that the electrodeposited coating is made of an apatite phase of low crystallinity with less porosity when hydrogen peroxide is added to the electrolyte solution. The corrosion measurements of the uncoated and coated alloys are also carried out during immersion in Hank’s solution at 310 K (37 °C), a physiological solution that simulates the inorganic composition of the body fluids. Interestingly, it was found that the manganese content in the alloy and the porosity of the coating both modify the corrosion behavior, i.e., the biodegradability of the Fe-Mn-Si alloy immersed in the physiological environment. Hence, the corrosion behavior of the calcium phosphate-coated Fe-Mn-Si alloys is tunable as a function of the experimental parameters used during the synthesis of the material.

The electrochemical behavior of pure Co, pure Sb, and CoSb3 has been investigated over a large anodic potential range (0 to 40 V) in two acids, i.e., oxalic acid or sulfuric acid at different concentrations (0.01 to 1 M). Potentiodynamic polarizations performed on CoSb3 plates reveal the possible formation of a passive layer between 1 and 3 V (vs SCE), on a passivation plateau. The oxidation of CoSb3 at 2 V in sulfuric and oxalic acids results in the growth of an anodic conversion layer. This coating is mainly made of a porous layer of amorphous antimony oxides due to dealloying of CoSb3. In the specific case of oxalic acid, rods of crystallized oxalates are tangled between the oxide sheets.

The Fe-Mn-Si alloys are promising materials for biodegradable metallic implants for temporary healing process in the human body. In this study, three different compositions are considered (Fe23Mn5Si, Fe26Mn5Si, and Fe30Mn5Si, all in wt pct). The phase composition analysis by XRD reveals e-martensite, α-martensite, and γ-austenite in various proportions depending on the manganese amount. The DSC study shows that the starting temperature of the martensitic transformation (Ms) of the alloys decreases when the manganese content increases (416 K, 401 K, and 323 K (143 °C, 128 °C, and 50 °C) for the Fe23Mn5Si, Fe26Mn5Si, and Fe30Mn5Si alloys, respectively). Moreover, mechanical compression tests indicate that these alloys have a much lower Young’s modulus (E) than pure iron (220 GPa), i.e., 145, 133, and 118 GPa for the Fe23Mn5Si, Fe26Mn5Si, and Fe30Mn5Si alloys, respectively. The corrosion behavior of the alloys is studied in Hank’s solution at 310 K (37 °C) using electrochemical experiments and weight loss measurements. The corrosion kinetics of the Fe-Mn-Si increases with the manganese content (0.48, 0.59, and 0.80 mm/year for the Fe23Mn5Si, Fe26Mn5Si, and Fe30Mn5Si alloys, respectively). The alloy with the highest manganese content shows the most promising properties for biomedical applications as a biodegradable and biomechanically compatible implant material.

International audience; Biphasic calcium phosphate coatings (hydroxyapatite/β-tricalcium phosphate) on titanium substrate (Ti6Al4V) are synthetized by pulsed current electrodeposition coupled to a thermal treatment under controlled atmosphere. The experimental conditions of the process such as the hydrogen peroxide amount and the treatment temperature are optimized in order to obtain different coatings compositions. The physico-chemical and structural characterizations of the coatings are carried out respectively by scanning electron microscopy associated with energy dispersive X-ray spectroscopy (SEM-EDXS) and X-ray diffraction (XRD). The in vitro dissolution-precipitation properties of the coated substrates are investigated by immersions into Dulbecco's Modified Eagle Medium (DMEM) from 1 to 28 days. The calcium and phosphorus concentrations variations in the biological liquid are assessed by Induced Coupled Plasma - Atomic Emission Spectroscopy (ICP-AES) for each immersion time. Furthermore, the corrosion behavior of the coated substrates are investigated using potentiodynamic polarization tests in DMEM and in Ringer's solution.The results show that this innovative process is suitable to synthesize two coatings composed respectively of HAP (37%)/β-TCP (63%) and HAP (62%)/β-TCP (38%) with different morphologies. On the other hand, the in vitro studies reveal that the coatings composition greatly influences their behavior in physiological medium, i.e. their dissolution-precipitation and their corrosion protection properties.

This work investigates the electrodeposition of cobalt-substituted calcium phosphate coatings on Ti22Nb6Zr alloy designed for bone implant applications. Several electrolytic solutions are tested with various amounts of cobalt. The impact of the addition of hydrogen peroxide (H2O2) to the electrolyte is also explored. The scanning electron microscope observations highlight the specific morphology of the coatings electrodeposited from the solutions with cobalt ions and H2O2. The X-ray diffraction analyses reveal that the substituted calcium phosphate coatings are made of an apatite phase of low crystallinity. The corrosion behaviour of the coated alloys is studied from polarization curves in Hank's solution at 37 °C, a physiological solution that simulates the body fluids. The cobalt-substituted calcium phosphate coatings protect the surface of the titanium alloy against the corrosion reactions induced by the aggressive physiological environment. The specific effect of the cobalt substitution is discussed and the corrosion results are compared to those obtained from unsubstituted coatings synthesized in the same experimental conditions. At last, the biocompatibility of this new implant surface is assessed in vitro by determining the cells survival after 24 h, 48 h and 72 h in contact with the electrodeposited coating.

International audience; This work presents the synthesis and the characterization of hybrid material thin films obtained by the combination of two processes. The electrochemical grafting of organic layers made of carboxyphenyl moieties is carried out from the reduction of a diazonium salt on tin dioxide (SnO2) thin films previously deposited on Si substrates by metal organic chemical vapor deposition (MOCVD). Since the MOCVD experimental parameters impact the crystal growth of the SnO2 layer (i.e. its morphology and its texturation), various electrochemical grafting models can occur, producing different hybrid materials. In order to evidence the efficiency of the electrochemical grafting of the carboxyphenyl moieties, X-ray Photoelectron Spectroscopy (XPS) is used to characterize the first nanometers in depth of the synthesized hybrid material layer. Then three electrochemical grafting models are proposed.

This work aims at studying the synthesis of hydroxyapatite (HAP) coatings by electrophoretic deposition (EPD) of a nano-sized powder. In this research, the variation of the potential and the deposition time, two essential experimental parameters, is explored. It has been established by scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM–EDXS) and X-ray diffraction (XRD) that the best results are obtained for deposition of the coating at 10 V during 10 min. Subsequently, the electrophoretic deposition was followed by thermal treatment of the samples in a controlled atmosphere to enhance their mechanical properties (hardness and Young's Modulus), key parameters to improve the lifespan of the implant materials. In this way, an innovative synthesis process has been developed to produce nano-HAP coatings with appropriate dimensional features known to provide an improved biological response.

The CoSb3 skutterudite compounds are thermoelectric materials used to produce electricity from heat. Unfortunately, these materials quickly oxidize in air at elevated temperature. To solve this problem, this work explores the possibility to produce a protective aluminide surface layer to limit the interactions with oxygen. To synthesize the layer, this research work experiments the pack cementation process. A good understanding of the process requires the knowledge of the thermodynamic phase equilibria of the involved elements. However, this ternary system has never been considered in literature. Therefore, the first part of the research concerns the study of the isothermal section at 600 °C of the Al–Co–Sb ternary system to improve the knowledge of the phases that can be formed during the pack cementation process. Next, the aluminide surface layer is synthesized, then characterized by coupling scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. The results reveal that the obtained coating is made of two crystalline phases, AlSb is the major one and Al9Co2 is the minor one. At last, the oxidation experiments point out the protective properties of the surface layer against oxygen penetration, keeping the substrate safe for 1000 h under a flow of synthetic air at 527 °C. Consequently, the aluminized CoSb3 is a promising thermoelectric material useable in oxidative environments.

International audience; The low carbon Co28Cr6Mo alloy used for artificial joints like hip and knee prostheses is subjected to a surface treatment called SMAT (surface mechanical attrition treatment). The purpose of this treatment is to modify the surface mechanical properties of the treated alloy. Since the SMAT impacts the surface of materials, its influence on the corrosion behavior of the CoCrMo alloy has to be assessed in a physiological solution as Ringer’s solution. Furthermore, a specific biomedical polishing is coupled with the SMAT in order to finalize the production of a hip prosthesis ready for use. The corresponding corrosion behavior is also studied. The corrosion behavior of CoCrMo alloy samples is investigated using electrochemical techniques (potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS)) in physiological liquid and simulated by an equivalent circuit. The polarization results show the reduction of the corrosion current density and the increase of the corrosion potential after the SMAT. The EIS analyses also show the benefit of the SMAT on the corrosion resistance of the CoCrMo alloy. The surface morphology modification and the phase’s transformation induced by the SMAT are evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD).

The effect of thermal treatments on electrodeposited calcium phosphate materials (CaP) is investigated. For this purpose, several temperatures up to 1000 °C are applied to powders obtained by scratching the synthesized coatings from their metallic substrate. The goal is to assess the structural and the morphological modifications of the powders that are known to strongly influence the in vivo bioactivity of the CaP materials. The morphology of the CaP materials is made of needles at room temperature that agglomerate to form rounded particles when the treatment temperature exceeds 800 °C. Simultaneously, the crystallinity increases with the treatment temperature until reaching a fully crystalline biphasic structure at 1000 °C. This biphasic structure consists in 80% Hydroxyapatite (HAP) and 20% β-tricalcium phosphate (β-TCP).

This work presents a new experimental process for the thermal treatment of prosthetic coatings obtained by electrodeposition on titanium alloy Ti6Al4V. This thermal treatment is required to evaporate the solvent from the coating and to improve its cohesion and its adhesion to the titanium alloy substrate. When such treatment is carried out in air, the temperature is limited to 550 °C due to the high oxidation of the titanium substrate. To overcome this limitation, we introduce a new thermal treatment process using a controlled atmosphere obtained by Argon injection under vacuum. In these conditions, the temperature can be increased up to 1 000 °C. This process prevents the formation of the oxide layer onto the titanium alloy surface without noticeable modification of its mechanical properties. It also allows to obtain a fully crystallized biphasic coating made of hydroxyapatite and β-tricalcium phosphate. Consequently, this work resulted in obtaining an implant (calcium phosphate coating on Ti6Al4V) with improved mechanical properties.

Au XIXe siecle, l’intervention laique est peu courante dans une Eglise catholique hierarchisee ou celui qui n’est pas clerc ne fait pas partie de l’Eglise enseignante ou meme agissante. Il faut attendre le concile de Vatican II pour que l’activite des laiques soit envisagee du point de vue de la doctrine. Cependant le XIXe siecle assista a l’emergence de quelques formes variees d’apostolat laique, de la Societe de Saint-Vincent-de-Paul a la premiere Action catholique, mais rares sont celles q...

An important aim of bone regenerative medicine is to design biomaterials with controlled chemical and topographical features to guide stem cell fate towards osteoblasts without addition of specific osteogenic factors. Herein, we find that sprayed bioactive and biocompatible calcium phosphate substrates (CaP) with controlled topography induce, in a well-orchestrated manner, Wharton's jelly stem cells (WJ-SCs) differentiation into osteoblastic lineage without any osteogenic supplements. The resulting WJ-SCs commitment exhibits features of native bone, through the formation of three-dimensional bone-like nodule with osteocyte-like cells embedded into a mineralized type I collagen. To our knowledge, these results present the first observation of a whole differentiation process from stem cell to osteocytes-like on a synthetic material. This suggests a great potential of sprayed CaP and WJ-SCs in bone tissue engineering. These unique features may facilitate the transition from bench to bedside and the development of successful engineered bone. Designing materials to direct stem cell fate has a relevant impact on stem cell biology and provides insights facilitating their clinical application in regenerative medicine. Inspired by natural bone compositions, a friendly automated spray-assisted system was used to build calcium phosphate substrate (CaP). Sprayed biomimetic solutions using mild conditions led to the formation of CaP with controlled physical properties, good bioactivity and biocompatibility. Herein, we show that via optimization of physical properties, CaP substrate induce osteogenic differentiation of Wharton's jelly stem cells (WJ-SCs) without adding osteogenic supplement factors. These results suggest a great potential of sprayed CaP and WJ-SCs in bone tissue engineering and may facilitate the transition from bench to beside and the development of clinically successful engineered bone. journal article research support, non-u.s. gov't 2017 02 2016 11 22 imported

Tin dioxide (SnO 2 ) thin films are deposited by pulsed metalorganic chemical vapor deposition (pulsed-MOCVD) on Si and LaAlO 3 substrates from tin precursor (Sn(thd) 2 ). The effects of two synthesis parameters on the structural and electrical properties of the films are studied. The structural modifications are assessed by grazing incidence X-ray diffraction (GIXRD) and Fourier transform infra-red spectroscopy (FT-IR). Two SnO 2 structures are observed in the deposited thin films (tetragonal and orthorhombic) and various preferential orientations of these SnO 2 structures are obtained according to the substrate temperature and the deposition frequency used. The morphology and the microstructure of the films are analyzed by field emission gun-scanning electron microscopy (FEG-SEM). The films are dense and well crystallized with various nanocrystalline morphologies. The electrical measurements carried out on the deposited SnO 2 thin film show that the observed morphological and structural modifications induce changes of its electrical properties. Finally, the electrochemical grafting of an organic layer is carried out on the various deposited SnO 2 surfaces to obtain new hybrid materials. Such innovative materials are very attractive as they have particular surface properties which make them powerful tools for thermoelectrical applications and for sensor applications for the detection of various ionic species at very low concentrations in aqueous media.

Calcium phosphate coatings are synthesized on titanium alloy (Ti6Al4V) substrates by pulsed electrodeposition. This work aims to observe the morphological modifications of the coating when an amino acid is added to the electrolytic solution used in the process. The effects of two amino acids (glutamic acid and aspartic acid) are studied at a low and a high concentration. The coating morphology is observed at a nanometer scale by field emission gun-scanning electron microscopy (FEG-SEM). The structural characterization of the coating is performed by Fourier transformed infrared spectroscopy (FT-IR), Raman spectroscopy and X-ray diffraction (XRD). Moreover, corrosion measurements of the prosthetic surfaces are carried out by potentiodynamic polarization experiments in a physiological solution named Dulbecco's modified eagle medium (DMEM). The results show that the addition of an amino acid to the electrolytic solution leads to the decrease of the size of the crystallites which compose the prosthetic calcium phosphate coating that becomes denser and less porous than the coatings obtained without amino acid. Consequently, the corrosion behavior of the prosthetic material immersed in DMEM is improved.

International audience; Doped CoSb3-based skutterudites compounds such as Co0.94Ni0.06Sb3 and Ce0.75Fe3CoSb12 are promising thermoelectric materials thanks to a high figure of merit (ZT > 1). This property makes these doped CoSb3-based skutterudites interesting materials to produce thermoelectric generators able to convert heat into electrical energy. Several recent developments have established that the nanostructuration of these materials enhance their thermoelectrical properties. However, the impact of the nanostructuration on the oxidation behavior of the skutterudites has never been studied. Indeed, their operating temperature under oxidative atmosphere (e.g. in air environment) is drastically limited because of their strong oxidation that produces oxides layers made of Sb2O3, Sb2O4, CoSb2O6 or CoSb2O4. These reactions promote the degradation of the thermoelectric properties of the material and the decrease of the device durability. Therefore the objective of this research work is to determine the impact of the nanostructuration on the oxidation behavior of two interesting doped CoSb3-based skutterudites, Co0.94Ni0.06Sb3 and Ce0.75Fe3CoSb12.The oxidation of the n-type skutterudite material (Co0.94Ni0.06Sb3) is enhanced by its nanostructuration since the surface oxide layer formed remains very thin up to 1000 hours. The oxidation of the p-type material (Ce0.75Fe3CoSb12) depicts similar behaviors whatever the structuration (micro- or nano-). The nanostructuration of these thermoelectric materials is known to improve their thermoelectric properties. Since there is no significant negative effect on their oxidation behavior, these nanostructured thermoelectric materials are good candidates for industrial uses in air atmosphere at these temperatures.

Calcium phosphate coatings on titanium alloy substrates are synthesized by pulsed electrodeposition and characterized by scanning electron microscopy associated to energy dispersive X-ray spectroscopy and by X-ray diffraction. The corrosion behavior of CaP/Ti6Al4V systems and uncoated Ti6Al4V are investigated using electrochemical methods in three physiological solutions and simulated with an equivalent circuit. The results reveal that the calcium phosphate coatings act as a protective layer especially when electrodeposition is carried out in the presence of hydrogen peroxide into the electrolyte which is used to control the chemical composition of the coatings and which implies a control of the corrosion behavior of the prosthetic material.

Thermal behavior of electrodeposited hydroxyapatite (HAP) coating on a titanium alloy (Ti6Al4V) is investigated in order to optimize the heat treatment conditions for this prosthetic material. The synthesized coatings are annealed in air atmosphere at 400, 600, 800, and 1000 °C, and then characterized by X-ray diffraction (XRD) and selected area electron diffraction (SAED) for structure and phases analysis. Scanning and transmission electron microscopy associated to energy dispersive X-ray microanalysis (SEM-EDXS and STEM) are used for morphology and composition analysis. The results show that when the electrodeposited coating is annealed at temperatures greater than 600 °C, a well-crystallized HAP is obtained with a notable change of its morphology. However, at these temperatures the surface of Ti6Al4V alloy (uncoated zones of the implant) is deteriorated by the formation of a thick surface oxide layer. Therefore, we limit the heat treatment temperature for the electrodeposited coatings on a Ti6Al4V alloy at 550 °C. At this optimized temperature it is demonstrated that the link between the coating and the substrate is improved and the crystallinity of the coating is controlled which make it well bioactive.

Calcium phosphate coatings on Ti6Al4V substrates were elaborated by pulsed electrodeposition with hydrogen peroxide (H 2 O 2 ) into electrolyte. The surface morphology and the chemical composition of the coatings were characterized by scanning electron microscopy (SEM) associated to Energy Dispersive X-ray Spectroscopy (EDXS) for X-ray microanalysis. The obtained results were systematically confirmed at the nanometre scale analysis using scanning transmission electron microscopy (STEM). Moreover, X-ray diffraction (XRD) was performed in order to identify the coatings phases. The results showed that pulsed electrodeposition without H 2 O 2 into electrolyte followed by heat treatment favoured coatings made of two phases which are stoichiometric hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP). On the other hand the addition of an optimized H 2 O 2 amount into electrolyte led to adherent and uniform coatings mainly made of stoichiometric hydroxyapatite (HAP).

Calcium phosphate coatings on Ti6Al4V substrates are elaborated by pulsed electrodeposition. The surface morphology and chemical composition of the coatings are characterized by SEM-EDS. The obtained results are systematically confirmed at the nanometre scale using TEM. Moreover, XRD is performed in order to identify the coatings phases. The results show that pulsed electrodeposition allows uniform coatings to be obtained without the holes and craters usually observed with classical electrodeposition. After appropriate heat treatment, these coatings have a biphasic composition of stoichiometric hydroxyapatite and β-tricalcium phosphate. Moreover, the addition of 9% H 2 O 2 to the electrolyte leads to monophasic coatings made of stoichiometric hydroxyapatite. As an indication of the passive nature of the electrodeposited coating, electrochemical potentiodynamic tests are performed in physiological solution in order to determine the corrosion behaviour of these coatings.

International audience; Hydroxyapatite (HAP) and 58S Bioactive Glasses (BG) coatings are successfully synthesized by Electrophoretic Deposition (EPD) on Ti6Al4V alloy subjected to Surface Mechanical Attrition Treatment (SMAT). This process uses steel balls impacts on the Ti6Al4V surface to improve its mechanical properties. However when the Ti6Al4V substrate is treated by SMAT the industrial plasma spray technique is not efficient to obtain adherent HAP coatings. This problem is mainly related to the modifications of the Ti6Al4V surface topography due to the SMAT process. Therefore, in this work we demonstrate that EPD offers an efficient solution to solve this technical problem. Indeed we obtain a homogeneous and adherent HAP coating on the SMATed Ti6Al4V surface from a suspension of nanoparticles in ethanol. Moreover EPD is successfully employed to produce a 58S BG coating on the SMATed Ti6Al4V surface. Scanning Electron Microscopy (SEM) associated to Energy Dispersive X-Ray Spectroscopy (EDXS) reveals that the coatings obtained by EPD are adherent and compact without alteration of their chemical composition.

International audience; Tin dioxide (SnO2) thin films are deposited by metal organic chemical vapor deposition (MOCVD) on Si substrates from three commercial metal organic precursors. The morphology and the microstructure of the films are observed by field emission gun-scanning electron microscopy (FEG-SEM). The films are dense and made of crystallites with a nanometer size. The structural properties of the films are assessed by grazing incidence X-ray diffraction (GIXRD). A tetragonal SnO2 phase is observed in the deposited thin films with various texturations as a function of the metal organic precursor used for the deposition. Chemical characterizations of the thin films are also carried out by Fourier transformed infrared spectroscopy (FT-IR) and by X-ray photoelectron spectroscopy (XPS). Finally, the observed morphological, chemical and structural modifications induce changes in the electrical properties of the film. Results are discussed and indicate that the electrical properties of the synthesized SnO2 thin films differ as a function of the MOCVD precursor used for the deposition. Therefore, their electrochemical behavior is modified which influences the grafting of organic molecules to synthesize and develop novel hybrid materials sensors.

In this paper a new sol–gel approach was explored for the synthesis of the 45S5 bioactive glass. We demonstrate that citric acid can be used instead of the usual nitric acid to catalyze the sol–gel reactions. The substitution of nitric acid by citric acid allows to reduce strongly the concentration of the acid solution necessary to catalyze the hydrolysis of silicon and phosphorus alkoxides. Two sol–gel powders with chemical compositions very close to that of the 45S5 were obtained by using either a 2 M nitric acid solution or either a 5 mM citric acid solution. These powders were characterized and compared to the commercial Bioglass®. The surface properties of the two bioglass powders were assessed by scanning electron microscopy (SEM) and by Brunauer–Emmett–Teller method (BET). The Fourier transformed infrared spectroscopy (FTIR) and the X-ray diffraction (XRD) revealed a partial crystallization associated to the formation of crystalline phases on the two sol–gel powders. The in vitro bioactivity was then studied at the key times during the first hours of immersion into acellular Simulated Body Fluid (SBF). After 4 h immersion into SBF we clearly demonstrate that the bioactivity level of the two sol–gel powders is similar and much higher than that of the commercial Bioglass®. This bioactivity improvement is associated to the increase of the porosity and the specific surface area of the powders synthesized by the sol–gel process. Moreover, the nitric acid is efficiently substituted by the citric acid to catalyze the sol–gel reactions without alteration of the bioactivity of the 45S5 bioactive glass.

Strontium-substituted calcium phosphate coatings are synthesized by pulsed electrodeposition on titanium alloy (Ti6Al4V) substrates. Experimental conditions of the process are optimized in order to obtain a coating with a 5% atomic substitution of calcium by strontium which corresponds to the best observations on the osteoblast cells activity and on the osteoclast cells proliferation. The physical and chemical characterizations of the obtained coating are carried out by scanning electron microscopy associated to energy dispersive X-ray spectroscopy (EDXS) for X-ray microanalysis and the structural characterization of the coating is carried out by X-ray diffraction. The in vitro dissolution/precipitation properties of the coated substrates are investigated by immersion into Dulbecco's Modified Eagle Medium (DMEM) from 1 h to 14 days. The calcium, phosphorus and strontium concentrations variations in the biological liquid are assessed by Induced Coupled Plasma - Atomic Emission Spectroscopy for each immersion time. The results show that under specific experimental conditions, the electrodeposition process is suitable to synthesize strontium-substituted calcium phosphate coatings. Moreover, the addition of hydrogen peroxide (H 2 O 2 ) into the electrolytic solution used in the process allows us to observe a control of the strontium release during the immersion of the prosthetic materials into DMEM.

CoSb3-based skutterudite compounds are promising thermoelectric materials thanks to a high figure of merit ZT. However their sensitivity to thermal degradation under oxidation mechanisms is a significant problem regarding their high operating temperature. A protective coating is therefore necessary. In this framework, the formation of an oxide conversion layer by surface anodizing represents an interesting alternative to PVD coatings usually considered. In the present work, the electrochemical behavior of CoSb3 is studied over a large anodic voltage range (0 to 50 V) in three acids, i.e. phosphoric acid, oxalic acid and sulfuric acid at different concentrations (0.01 M to 1 M). Potentiodynamic polarizations performed on CoSb3 plates, in comparison with pure Co and pure Sb, reveal the possible formation of a passive layer between 1V and 3V, on a passivation plateau. Actually, below 3V, the electrochemical behavior of CoSb3 is similar to the behavior of pure Sb, whatever the electrolyte and the concentration. Beyond this potential, the current density rises on CoSb3 and stabilizes one order of magnitude higher. Regarding pure Co, it obviously undergoes dissolution as shown by the very high current densities reached. The oxidation of CoSb3 at 2V in sulfuric and oxalic acids results in the growth of a conversion layer. According to SEM-EDS and DRX experiments, this coating is mainly made of amorphous antimony oxides (due to the high selective dissolution rate of cobalt in these media), constituting a porous (exfoliated) matrix. In the specific case of oxalic acid, sticks of crystallized oxalates (mostly antimony oxalate hydroxide but also cobalt oxalate hydroxide) are tangled between the oxide sheets. Figure 1

International audience; Titanium alloys used in orthopedic surgery are usually coated with hydroxyapatite to improve their biocompatibility and osseointegration. Bioactive glasses (BGs) are an interesting alternative to hydroxyapatite for the production of prosthetic coatings due to their osteoproductive property (Class A bioactivity) and to their resorbability. However the classical techniques used to obtain prosthetic coatings are not suitable in the case of BGs. In this study bioactive glass coatings are obtained by electrophoretic deposition on a Ti12Mo5Ta alloy. These coatings were obtained from ethanol suspensions of two different bioglass powders: a Sol-Gel derived 58S and a Melting-Quenching derived 46S. Scanning electron microscopy observations were used to characterize the coatings (morphology and thickness) and the coating/substrate interfaces. The chemical composition of the coatings was studied by X-ray microanalysis and X-ray maps were performed to characterize the spatial distributions of all elements composing the coatings.

Calcium-deficient hydroxyapatite (Ca-def-HAP) coatings on titanium alloy (Ti6Al4V) substrates are elaborated by pulsed electrodeposition. In vitro dissolution/precipitation process is investigated by immersion of the coated substrate into Dulbecco’s Modified Eagle Medium (DMEM) from 1 h to 28 days. Calcium and phosphorus concentrations evolution in the biological liquid are determined by Induced Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) for each immersion time. Physical and chemical characterizations of the coating are performed by scanning electron microscopy (SEM) associated to Energy Dispersive X-ray Spectroscopy (EDXS) for X-ray microanalysis. Surface modifications are investigated by an original method based on the three-dimensional reconstruction of SEM images (3D-SEM). Moreover, corrosion measurements are carried out by potentiodynamic polarization experiments. The results show that the precipitation rate of the Ca-def HAP coating is more pronounced in comparison with that of stoichiometric hydroxyapatite (HAP) used as reference. The precipitated bone-like apatite coating is thick, homogenous and exhibits an improved link to the substrate. Consequently, the corrosion behaviour of the elaborated prosthetic material is improved.

In this work, the 45S5 bioactive glass has been prepared by the sol-gel process using an organic acid catalyst instead of nitric acid usually used. The physico-chemical and structural characterizations confirmed and validated the elemental composition of the resulting glass. In addition, the 45S5 bioactive glass powder thus obtained was successfully used to elaborate by electrophoretic deposition a prosthetic coating on titanium alloy Ti6Al4V.

Calcium-deficient hydroxyapatite (Ca-def HAP) coatings are synthesized by pulsed electrodeposition on titanium alloy (Ti6Al4V) substrates. Physico-chemical characterizations of the coating are carried out using Scanning Electron Microscopy (SEM) associated with Energy Dispersive X-ray Spectroscopy (EDXS) for X-ray microanalysis, and Scanning-Transmission Electron Microscopy (STEM) and X-Ray Diffraction (XRD) for structural characterization. Moreover, the biocompatibility properties of the synthesized biomaterial are studied by observing the human osteoblast-like cells’ (MG-63) response, which is investigated using a proliferation study carried out with an MTS test, and a cellular morphology study performed by SEM. The analysis of gene expression is carried out using a Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR). The results indicate that the pulsed electrodeposited Ca-def HAP coating doesn't produce any cytotoxic effect and enhances the gene expression of alkaline phosphatase (ALP) and osteocalcin (OC) which are the two main markers of osteoblast differentiation and bone neoformation.