Search

Magnesium and its alloys are promising materials that have potential mainly in the field of transport (e.g. automobile industry) and medicine (e.g. orthopedic implants). Their disadvantage is poor corrosion resistance, which limits their wider use in practice. Therefore, surface treatment by various methods is performed in order to improve corrosion protection. The preparation of a superhydrophobic coating is an interesting approach because the hydrophobic coating minimizes contact of the corrosion medium with the magnesium substrate. In this work, the hydrothermally prepared hydroxyapatite coating on AZ31 magnesium alloy was superhydrophobized by myristic acid. The prepared coatings were characterized by determining contact angle and surface analysis using a scanning electron microscopy with energy dispersive spectroscopy and Fourier transformed infrared spectroscopy. The corrosion resistance of modified surfaces was examined by potenciodynamic polarization in 3.5 % NaCl.

Magnesium and its alloys are promising materials that have potential mainly in the field of transport (e.g. automobile industry) and medicine (e.g. orthopedic implants). Their disadvantage is poor corrosion resistance, which limits their wider use in practice. Therefore, surface treatment by various methods is performed in order to improve corrosion protection. The preparation of a superhydrophobic coating is an interesting approach because the hydrophobic coating minimizes contact of the corrosion medium with the magnesium substrate. In this work, the hydrothermally prepared hydroxyapatite coating on AZ31 magnesium alloy was superhydrophobized by myristic acid. The prepared coatings were characterized by determining contact angle and surface analysis using a scanning electron microscopy with energy dispersive spectroscopy and Fourier transformed infrared spectroscopy. The corrosion resistance of modified surfaces was examined by potenciodynamic polarization in 3.5 % NaCl.

Magnesium and its alloys are promising materials that have potential mainly in the field of transport (e.g. automobile industry) and medicine (e.g. orthopedic implants). Their disadvantage is poor corrosion resistance, which limits their wider use in practice. Therefore, surface treatment by various methods is performed in order to improve corrosion protection. The preparation of a superhydrophobic coating is an interesting approach because the hydrophobic coating minimizes contact of the corrosion medium with the magnesium substrate. In this work, the hydrothermally prepared hydroxyapatite coating on AZ31 magnesium alloy was superhydrophobized by myristic acid. The prepared coatings were characterized by determining contact angle and surface analysis using a scanning electron microscopy with energy dispersive spectroscopy and Fourier transformed infrared spectroscopy. The corrosion resistance of modified surfaces was examined by potenciodynamic polarization in 3.5 % NaCl.

Titanium and its alloys are widely used in medical devices, orthopedic implants, dental implants, and device components of aerospace industries. It is attractive for having superior room and elevated temperature mechanical properties, corrosion resistance, fatigue resistance and low weight. However, titanium and its alloys are not fully applicable replacement in biomedical application. Suitable surface modification of titanium is needed in order to obtain Ti with improved properties. This paper deals with the optimization of the in-situ anodizing/anaphoretic electrodeposition process of hydrothermally synthesized hydroxyapatite (HAp) on Ti substrate for subsequent obtaining of HAp/TiO2 composite coatings without multi-stage pre-treatment and post-treatment of titanium and oxidized titanium surface. Coatings were prepared at constant voltage of 60 V and deposition time of 1 min. The morphology of coatings was investigated using optical microscope and field emission scanning electron microscope. Fourier transform infrared spectroscopy measurements were also performed. The coating with optimal properties was obtained by deposition from suspension containing 1.0 M NaOH.

In-situ synthesis of HAp/TiO2 coating on titanium was performed via anaphoretic deposition of HAp and simultaneous anodization of Ti to produce highly adherent and strengthened composite coating. The prepared coatings were characterized by field emission scanning electron microscopy, X-ray diffraction and electron dispersive spectroscopy. HAp on anodized titanium was prepared at constant voltage of 60 V and deposition time of 45 s, which provided uniform and adherent HAp/TiO2 composite coating on Ti. Since smaller size of HAp crystals within highly porous coating structures is of improved binding ability to various biomolecules, our coating is expected to be of excellent coverage and compactness. The obtained coating can be good candidate for bone implants due to reduced brittleness and improved adhesion.

In-situ synthesis of HAp/TiO2 coating on titanium was performed via anaphoretic deposition of HAp and simultaneous anodization of Ti to produce highly adherent and strengthened composite coating. The prepared coatings were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and electron dispersive spectroscopy. HAp on anodized titanium was prepared at constant voltage of 60 V and deposition time of 45 s, which provided uniform and adherent HAp/TiO2 composite coating on Ti. Since smaller size of HAp crystals within highly porous coating structures is of improved binding ability to various biomolecules, our coating is expected to be of excellent coverage and compactness. The obtained coating can be good candidate for bone implants due to reduced brittleness and improved adhesion.

In-situ synthesis of HAp/TiO2 coating on titanium was performed via anaphoretic deposition of HAp and simultaneous anodization of Ti to produce highly adherent and strengthened composite coating. The prepared coatings were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and electron dispersive spectroscopy. HAp on anodized titanium was prepared at constant voltage of 60 V and deposition time of 45 s, which provided uniform and adherent HAp/TiO2 composite coating on Ti. Since smaller size of HAp crystals within highly porous coating structures is of improved binding ability to various biomolecules, our coating is expected to be of excellent coverage and compactness. The obtained coating can be good candidate for bone implants due to reduced brittleness and improved adhesion.

In-situ synthesis of HAp/TiO2 coating on titanium was performed via anaphoretic deposition of HAp and simultaneous anodization of Ti to produce highly adherent and strengthened composite coating. The prepared coatings were characterized by field emission scanning electron microscopy, X-ray diffraction and electron dispersive spectroscopy. HAp on anodized titanium was prepared at constant voltage of 60 V and deposition time of 45 s, which provided uniform and adherent HAp/TiO2 composite coating on Ti. Since smaller size of HAp crystals within highly porous coating structures is of improved binding ability to various biomolecules, our coating is expected to be of excellent coverage and compactness. The obtained coating can be good candidate for bone implants due to reduced brittleness and improved adhesion.

The lack of bioactivity of titanium (Ti) is one of the main drawbacks for its application in biomedical implants since it can considerable reduce its osseointegration capacities. One strategy to overcome this limitation is the coating of Ti with hydroxyapatite (HA), which presents similar chemical composition than bone. Nonetheless, most of the strategies currently used generate a non-stable coating and may produce the formation of amorphous phases when high temperatures are used. Herein, we proposed to generate a Ti-HA composite coating on Ti surface to improve the stability of the bioactive coating. The coating was produced by cold gas spraying, which uses relatively low temperatures, and compared to a Ti coating. The coating was thoroughly characterized in terms of morphology, roughness, porosity and phase composition. In addition, the coating was mechanically characterized using a tensile loading machine. Finally, biological response was evaluated after seeding SaOS-2 osteoblasts and measuring cell adhesion, proliferation and differentiation. The novel Ti-HA coating presented high porosity and high adhesion and bond strengths. No change in HA phases was observed after coating formation. Moreover, osteoblast-like cells adhered, proliferated and differentiated on Ti-HA coated surfaces suggesting that the novel coating might be a good candidate for biomedical applications., Peer Reviewed, Postprint (author's final draft)

En raison du vieillissement de la population et de son augmentation constante, les pathologies et traumatismes osseux nécessitant une réparation ou un remplacement sont en croissance permanente (4%/an). Le revêtement d’hydroxyapatite confère à la prothèse une stabilité primaire et des propriétés d’ostéointégration. Cependant, une révision prématurée de la prothèse est nécessaire dans environ 10 % des cas et entre 1 et 2 % des prothèses ont été l’objet d’une ré-opération suite à une infection bactérienne. Les besoins actuels en orthopédie exigent donc un revêtement mécaniquement stable sur le long terme et présentant un caractère antibactérien. Des revêtements de structure nanométriques développés récemment suscitent beaucoup d’intérêt de la part des professionnels de santé car ceux-ci présentent une bioactivité accrue. Or, un tel ordre de grandeur est inatteignable via les techniques de projection actuellement employées. La projection plasma de suspension (SPS) est une technique de synthèse permettant d’accéder à des revêtements de dimension submicrométrique voire nanométrique. Les objectifs de ce travail de thèse ont consisté à mettre au point un revêtement de structure submicrométrique par rf-SPS en vue d’en améliorer la bioactivité, et d’évaluer l’impact de l’incorporation de dopants antibactériens sur les caractéristiques physicochimiques et les propriétés mécaniques et biologiques, en vue d’une potentielle application clinique de ces revêtements. Afin de faciliter la mise en œuvre et améliorer la répétabilité du procédé, l’impact de la préparation de la suspension sur les caractéristiques physicochimiques des revêtements a été investigué, puis les conditions de projection ont été optimisées afin d’atteindre des caractéristiques conformes aux normes et aux exigences conventionnelles des fabricants, comme la composition cristalline (%m HA > 50), la cristallinité (> 45 %) et la microstructure (porosité < 10 %v). Ensuite, les effets d’une incorporation d’éléments a, Due to the aging of the population and its constant increase, bone diseases and traumas requiring repair or replacement are constantly growing (4%/year). Hydroxyapatite coating gives the prosthesis primary stability and osseointegration properties. However, premature revision of the prosthesis is necessary in about 10% of cases. Bacterial infections lead to re-operations for 1 to 2 % of newly implanted prostheses. These revisions are expensive for the health system but also for the patient. Current needs in orthopedics therefore require a mechanically stable coating in the long term and having an antibacterial character. Recently developed nanostructured coatings are of great interest to health professionals since they show increased bioactivity. However, such an order of magnitude is unattainable by spraying techniques currently used by manufacturers. Suspension plasma spraying (SPS) is a synthetic technique for accessing sub-micron or even nanometer-sized coatings. The objectives of this thesis work were to develop a submicrometric structured coating by rf-SPS in order to improve the bioactivity, and to evaluate the impact of the incorporation of antibacterial dopants on the physicochemical characteristics and the mechanical and biological properties, with a view to a potential clinical application of these coatings. In order to facilitate the implementation and improve the repeatability of the process, the impact of the suspension preparation on the physicochemical characteristics of the coatings has been investigated. The spraying conditions have been optimized to achieve minimum features that meet the standards and conventional requirements of manufacturers, such as crystalline composition (HA > 50 wt%), crystallinity (> 45 %) and microstructure (porosity < 10 v%). Then, the effects of incorporation of elements with bactericidal (Ag) and bone growth stimulating (Sr) properties were investigated and compared with a conventional plasma sprayed reference

Present paper reports on the results of surface modification of the additively manufactured porous Ti6Al4V scaffolds. Radio frequency (RF) magnetron sputtering was used to modify the surface of the alloy via deposition of the biocompatible hydroxyapatite (HA) coating. The surface morphology, chemical and phase composition of the HA-coated alloy were studied. It was revealed that RF magnetron sputtering allows preparing a homogeneous HA coating onto the entire surface of scaffolds.

Characteristics of the hydroxyapatite (HA) plasma coatings are directly related to the performances of the plasma jet used in the deposition process. Previous research within a plasma spray technique, based on the application of the conventional plasma gun (PG), suggested the use of lower power level of the PG, about 25kW, in order to avoid significant chemical decomposition of HA occurring at higher powers. However, coatings obtained at this power level have a poor microstructure, resulting in their unsatisfactory cohesion/adhesion properties. In contrast to that, this study shows that good quality HA coatings can be produced in plasma obtained by plasma jet operated at high power level (52 kW) and in laminar flow mode. For two HA powders types, containing particles differing in mass by a factor of 20, a set of optimum deposition parameters has been defined leading to the coatings with high crystallinity (80-90%), excellent microstructure (porosity 1-2%) and high adhesion strength (60 and 40 MPa for the coating thicknesses of 120 and 350 mu m, respectively). It has been shown that higher plasma power does not necessarily lead to a higher HA decomposition.

For two hydroxyapatite (HA) powders, containing particles differing in mass by a factor of 20, a set of optimum deposition parameters was defined, leading to the coatings with high crystallinity (80-90%), high adhesion strength (60 and 40 MPa for the coating thicknesses of 120 mu m and 350 mu m, respectively) and excellent microstructure (coatings were without micro- or macro-cracks, without delaminating on substrate-coating surface contact, and possess low porosity, 1-2%). It was shown that higher plasma power (52 kW) did not necessarily lead to a higher HA decomposition. (C) 2011 Elsevier B.V. All rights reserved.

In this study was evaluated the corrosion resistance of nitrogen austenitic stainless steel, ASTM-F1586 and Böhler-P558, plasma-sprayed hydroxyapatite coating. The layers were characterized by SEM and DRX. The corrosion resistance was evaluated using tests of potential open circuit and cyclical polarization in Ringer solution to 37°C. The layers present lamelar morphology and pores. In the electrochemical tests was observed that the resistance was improved due to the presence of nitrogen and the influence of the layers porosity in the diminution of the corrosion resistance., En este estudio fue evaluada la resistencia a la corrosión de los aceros inoxidables austeníticos conteniendo nitrógeno, ASTM-F1586 y Böhler-P558, recubiertos con hidroxiapatita por aspersión por plasma. Las capas fueron caracterizadas por MEB y DRX. Fue analizada la resistencia a la corrosión usando ensayos de potencial de circuito abierto y polarización cíclica en solución Ringer a 37°C. Las capas presentan una estructura porosa. En los ensayos electroquímicos se mostró la mejora en la resistencia por la presencia del nitrógeno y la influencia de la porosidad de las capas en la disminución de la resistencia a la corrosión.

This is a clinical and radiographic review of 87 hips in 79 patients 9 (7-11) years after acetabular revision with extensive use of morselized allograft firmly impacted into localized defects as well as the entire acetabular cavity, followed by insertion of an uncemented hydroxyapatite-coated cup with supplementary screw fixation. The 9-year survival rate for the acetabular implant was 90.5% (95% CI, 83.4%-97.6%) with revision for any reason as end point and 94% (95% CI, 89%-99.1%) with revision for aseptic loosening as end point. Acetabular revision with massive allograft impaction and hydroxyapatite-coated implants show very promising results. The limited contact between implant and host bone does not seem to compromise implant survival in the 7- to 11-year perspective.

A new test method for the mechanical behavior of coatings on metal substrates under shear loading has been developed. Finite element simulations show that this new test method provides an almost identical shear load on the coatings to that of the conventional test. Using the new method, the static and fatigue behavior of plasma-sprayed hydroxyapatite (HA) coatings on Ti-6Al-4V substrates were studied at room temperature as a function of processing conditions. The results of the static tests show that the nominal interface shear strength is in the range of 25 similar to 40 MPa. The fatigue resistance to cyclic shear loading was characterized by shear stress amplitude versus cycle-to-failure for the samples that failed within 10(7) cycles, and by residual nominal interfacial shear strength for the samples that survived 10(7) cycles. The experimental results indicate that a threshold level of shear stress amplitude exists for introducing fatigue damage to HA coatings. AES and XPS studies indicated that bonding between the coating and substrate does not occur over about 12 percent of the area of the interface while bonding in the contact area of the interface is mainly mechanical interlocking. A failure mechanism of interfacial microflaw coalescence is suggested.

Plasma-sprayed hydroxyapatite (HA) coated Ti-6A1-4V is a promising material for biomedical implants. Successful applications of this implant material rely on fundamental understandings of the microstructure characteristics and mechanical behavior of the HA coating. The objectives of this M. Phil. study are (1) to characterize the heterogeneous features of the plasma sprayed HA coatings, and (2) to study the shear strength and shear fatigue of HA coatings by torsion testing. Although the XRD revealed multiphases in the as-sprayed coating and improvement of homogeneity in the coatings by post heat treatment, more advanced techniques, including micro Raman spectroscopy, ToF SIMS and XPS were employed to reveal the chemical and microstructure variation through the coating thickness direction by examining the cross-section of coatings. The results of micro Raman spectroscopy confirmed that chemical gradient exists along coating thickness direction. The coating crystallinity decreases with the distance from interface in the as-sprayed conditions. The Raman spectra also showed that the heat treatment effectively promote chemical homogeneity through the thickness direction. Two recently developed techniques were examined and their possible applications to the plasma sprayed HA coating were explored. The techniques include identifying calcium phosphates with PO3-/PO2- in ToF-SIMS and with the energy loss peaks of O 1s as well as Ca/P, O/Ca ratios in XPS. This study confirmed that such techniques can be used for identifying certain calcium phosphate phases in their pure power states. Their applications to the plasma sprayed coatings however have turned out to be unsatisfactory. This study also found out that it was difficult to use the information of energy loss peaks of O 1s in XPS, because the weak peaks make substantial errors in their measurement. Torsion tests were employed to examine the coating bonding shear resistance, which eliminated the normal stress associated wit

Plasma-sprayed hydroxyapatite (HA) coated Ti-6Al-4V is a promising material for biomedical implants. Successful applications of this implant material rely on fundamental understandings of the microstructure characteristics and mechanical behavior of the HA coating. The objectives of the present work are (1) to characterize the heterogeneous features of the HA coating, (2) to quantify the elastic/plastic behavior of the HA coating, and (3) to systematically examine in vitro mechanical integrity of the HA coating under various loading conditions The microstructure characterization of the as-sprayed HA coating demonstrates that it exhibits two distinctive regions on its cross-section, i.e. a crystalline ribbon-like region surrounded by a relatively smooth amorphous region. The OH and O concentrations are also found to decrease with depth from the surface of the HA coating and reach a minimum at the coating/substrate interfaces. A feasible approach that combines the indentation tests with nonlinear finite element modeling has been developed to estimate the elastic/plastic constitutive relation of HA coatings on Ti-6Al-4V substrates. The results show that the Ramberg-Osgood constitutive equation properly describes the deformation behavior of the HA coating. Experiments revealed that conventional cyclic bending tests cannot effectively evaluate the fatigue resistance of the HA coating on Ti-6Al-4V in both air and simulated body fluid (SBF). Alternative approaches including Hertzian indentation and a new shear test method were employed. The fatigue tests of the coating under cyclic Hertzian indentation revealed that the fatigue damage of the HA coating is more severe in SBF than in air, and thin HA coating exhibits less fatigue damage than thick HA coating. The new shear test method was developed to test coatings on metal substrates. This method generates almost the same shear loading on coatings as that in conventional tests and possesses such advantages as simplicity, ea