New material for orthopedic implants: Electrochemical study of nickel free P558 stainless steel in minimum essential medium

Nickel, a component of stainless steels (SS) applied in orthopedic implants may cause allergic processes in human tissues P558 nickel free SS was studied to verify its viability as a substitute for stainless steel containing nickel Its performance is compared to ISO 5832-9 and F138 most used nowadays grades in implants fabrications, in minimum essential medium. MEM, at 37 degrees C. Potentiodynamic polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and ""in vitro"" cytotoxicity were used as techniques. From the electrochemical point of view P558 SS is comparable to ISO 5832-9 SS in MEM It remains passivated until the transpassivation potential, above which generalized corrosion occurs F138 presents pitting corrosion at 370 mV/SCE. The cytotoxicity results showed that P558. ISO 5832-9 and F138 do not present cytotoxic character Therefore, these results suggest that P558 SS can be applied in orthopedic implants (C) 2010 Elsevier BV All rights reserved

Automated two-dimensional separation flow system with electrochemical preconcentration, stripping, capillary electrophoresis and contactless conductivity detection for trace metal ion analysis

This paper describes the automation of a fully electrochemical system for preconcentration, cleanup, separation and detection, comprising the hyphenation of a thin layer electrochemical flow cell with CE coupled with contactless conductivity detection (CE-C(4)D). Traces of heavy metal ions were extracted from the pulsed-flowing sample and accumulated on a glassy carbon working electrode by electroreduction for some minutes. Anodic stripping of the accumulated metals was synchronized with hydrodynamic injection into the capillary. The effect of the angle of the slant polished tip of the CE capillary and its orientation against the working electrode in the electrochemical preconcentration (EPC) flow cell and of the accumulation time were studied, aiming at maximum CE-C(4)D signal enhancement. After 6 min of EPC, enhancement factors close to 50 times were obtained for thallium, lead, cadmium and copper ions, and about 16 for zinc ions. Limits of detection below 25 nmol/L were estimated for all target analytes but zinc. A second separation dimension was added to the CE separation capabilities by staircase scanning of the potentiostatic deposition and/or stripping potentials of metal ions, as implemented with the EPC-CE-C(4)D flow system. A matrix exchange between the deposition and stripping steps, highly valuable for sample cleanup, can be straightforwardly programmed with the multi-pumping flow management system. The automated simultaneous determination of the traces of five accumulable heavy metals together with four non-accumulated alkaline and alkaline earth metals in a single run was demonstrated, to highlight the potentiality of the system.

Study of electrochemical behavior of azoles for AISI 430 stainless steel in H(2)SO(4) 1 mol L(-1)

Corrosion is an undesirable process that occurs in metallic materials. Studied was the effect of inhibiting Benzotriazole (BTAH), Benzimidazole (BZM) and Indole in different concentrations-for the stainless steel (SS) AISI 430 in H(2)SO(4) mol The techniques employed this research were: anodic potenciostatic polarisation, electrochemical impedance spectroscopy, optical microscopy and scanning electron microscopy The curves of anodic polarisation showed that BTAH, BZM and Indol act as corrosion inhibitors for 430 SS, at concentrations of 1x10(-3) and 5x10(-4) mol L(-1) but do not inhibit corrosion for concentrations equal to or less than 1x10(-4) mol L(-1). The in-crease of the efficiency in relation to the inhibitory substances studied followed this order: Indol electrochemical impedance spectroscopy, and microscopic analysis.

Effect of mechanical coating with Ni and Ni-5% Al on the structure and electrochemical properties of the Mg-50% Ni alloy

The Mg-Ni metastable alloys (with amorphous or nanocrystalline structures) are promising candidates for anode application in nickel-metal hydride rechargeable batteries due to its large hydrogen absorbing capacity, low weight, availability, and relative low price. In spite of these interesting features, improvement on the cycle life performance must be achieved to allow its application in commercial products. In the present paper, the effect of mechanical coating of a Mg-50 at.% Ni alloy with Ni and Ni-5 at.% Al on the structure, powder morphology, and electrochemical properties is investigated. The coating additives, Mg-Ni alloy and resulting nanocomposites (i.e., Mg-Ni alloy + additive) were investigated by means of X-ray diffraction and scanning electron microscopy. The Mg-Ni alloy and nanocomposites were submitted to galvanostatic cycles of charge and discharge to evaluate their electrode performances. The mechanical coating with Ni and Ni-5% Al increased the maximum discharge capacity of the Mg-Ni alloy from of 221 to 257 and 273 mA h g(-1), respectively. Improvement on the cycle life performance was also achieved by mechanical coating.

Deposition of selenium thin layers on gold surfaces from sulphuric acid media: Studies using electrochemical quartz crystal microbalance, cyclic voltammetry and AFM

In this paper we report here new considerations about the relationship between the mass and charge variations (m/z relationship) in underpotential deposition (UPD), bulk deposition and also in the H(2)Se formation reaction. Nanogravimetric experiments were able to show the adsorption of H(2)SeO(3) on the AuO surface prior to the voltammetric sweep and that, after the AuO reduction, 0.40 monolayer of H(2)SeO(3) remains adsorbed on the newly reduced Au surface, which was enough to gives rise to the UPD layer. The UPD results indicate that the maximum coverage with Se(ads) on polycrystalline gold surface corresponds to approximately 0.40 monolayer, in good agreement with charge density results. The cyclic voltammetry experiments demonstrated that the amount of bulk Se obtained during the potential scan to approximately 2 Se monolayers, which was further confirmed by electrochemical quartz crystal microbalance (EQCM) measurements that pointed out a mass variation corresponding of 3 monolayers of Se. In addition, the Se thin films were obtained by chronoamperometric experiments, where the Au electrode was polarized at +0.10V during different times in 1.0 M H(2)SO(4) + 1.0 mM SeO(2). The topologic aspects of the electrodeposits were observed in Atomic Force Microscope (AFM) measurements. Finally, in highly negative potential polarizations, the H(2)Se formation was analyzed by voltammetric and nanogravimetric measurements. These finding brings a new light on the selenium electrodeposition and point up to a proposed electrochemical model for molecule controlled surface engineering. (c) 2009 Elsevier Ltd. All rights reserved.

Structural and electrochemical properties of LiCoO2 prepared by combustion synthesis

LiCoO2 powders were prepared by combustion synthesis, using metallic nitrates as the oxidant and metal sources and urea as fuel. A small amount of the LiCoO2 phase was obtained directly from the combustion reaction, however, a heat treatment was necessary for the phase crystallization. The heat treatment was performed at the temperature range from 400 up to 700 degreesC for 12 h. The powders were characterized by X-ray diffraction (XRD), X ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and specific surface area values were obtained by BET isotherms. Composite electrodes were prepared using a mixture of LiCoO2, carbon black and poly(vinylidene fluoride) (PVDF) in the 85:10:5% w/w ratio. The electrochemical behavior of these composites was evaluated in ethylene carbonate/dimethylcarbonate solution, using lithium perchlorate as supporting electrolyte. Cyclic voltammograms showed one reversible redox process at 4.0/3.85 V and one irreversible redox process at 3.3 V for the LiCoO2 obtained after a post-heat treatment at 400 and 500 degreesC.Raman spectroscopy showed the possible presence of LiCoO2 with cubic structure for the material obtained at 400 and 500 degreesC. This result is in agreement with X-ray data with structural refinement for the LiCoO2 powders obtained at different temperatures using the Rietveld method. Data from this method showed the coexistence of cubic LiCoO2 (spinel) and rhombohedral (layered) structures when LiCoO2 was obtained at lower temperatures (400 and 500 degreesC). The single rhombohedral structure for LiCoO2 was obtained after post-heat treatment at 600 degreesC. The maximum energy capacity in the first discharge was 136 mA g(-1) for the composite electrode based on LiCoO2 obtained after heat treatment at 700 degreesC. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Microstructural and electrochemical study of La0.5Li0.5TiO3

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electrochemical study of o-toluidine blue impregnated in mesoporous silica channels

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Stability of cp-Ti and Ti-6Al-4V alloy for dental implants as a function of saliva pH - an electrochemical study

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Thermal and electrochemical study of solid-state reaction of mercury with Pt-20% Rh alloy

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Utilization of electrochemical impedance spectroscopy for monitoring bornite (CU5FeS4) oxidation by Acidithiobacillus ferrooxidans

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of iron addition on the microstructure and the electrochemical corrosion of Al-Zn-Mg alloys

The effect of Fe addition on the microstructural properties and the corrosion resistance of Al-Zn-Mg alloys submitted to different heat treatments (cast, annealed and aged), has been studied in chloride solutions using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), cyclic polarization (CP) and open circuit potential (o.c.p.) measurements. The presence of 0.3% Fe in the alloy limited the growth of the MgZn2 precipitates, both in the annealed and in the quenched specimens. No effect of Cr on the grain size in the presence of Fe was found because of the accumulation of Cr in the Fe-rich particles. Fe in the Al-Zn-Mg alloys also made them more susceptible to pitting. Pitting occurred mainly near the Fe-rich particles both, under o.c.p. conditions in O-2-saturated solutions and during the CP.

Influence of spraying parameters on the electrochemical behaviour of HVOF thermally sprayed stainless steel coatings in 3.4% NaCl

Stainless steel coatings obtained by High Velocity Oxygen Fuel (HVOF) were characterized using optical (OM) and scanning electron microscopy (SEM), electron probe micro-analysis, X-ray diffraction (XRD), open-circuit potential (E-OC) measurements, electrochemical impedance spectroscopy (EIS) and polarisation tests. Differences among coated steels were mainly related with the gun-substrate distance parameter (310 nm for samples A and B and 260 min for C and D). The open-circuit potential values measured for all the samples after 18 h of immersion in aerated and unstirred 3.4% NaCl solution were: - 0.334, - 0.360, - 0.379 and - 0.412 V vs. Ag/AgCl,KClsat. for samples A to D, respectively. For EIS measurements, Nyquist plots showed higher capacitive semi-circle for samples sprayed at longer distance, indicating higher corrosion resistance in NaCl solution. (c) 2005 Elsevier B.V. All rights reserved.

Effects of thickness coating on the electrochemical behaviour of thermal spray Cr3C2-NiCr coatings

Thermally sprayed HVOF coatings are increasingly being used in industrial applications where high wear and corrosion resistance are needed [1,2]. In this paper, electrochemical ac and de experiments were used in order to obtain the corrosion resistance of coated steel with different numbers of Cr3C2-NiCr layers. This work has been performed in order to determine the role of coating thickness in the corrosion behaviour of a steel protected with cermet thermally sprayed coatings. It is known that a thicker layer protects better against corrosion when a metallic coating is evaluated. But cermet coatings, such as Cr3C2-NiCr, contain higher levels of porosity and residual stresses than metallic coatings, which really could influence the corrosion resistance of the deposited layer. Electrochemical measurements, such as Open-Circuit Potential (E-Osubset of), Polarisation Resistance (RP) and Cyclic Voltammetry (CV), were performed in an aerated 3.4 NaCI media (%wt.). Electrochemical Impedance Measurements (EIS) were also done in order to obtain a mechanism that explains the corrosion process. Structural Characterisation was carried out by means of Optical and Scanning Electron Microscopes (OM, SEM) with an Energy Dispersive Spectrometry analyser (EDS). Results show that the corrosion resistance of the complete system is mainly influenced by the substrate behaviour. The application of a higher number of deposited layers did not substantially increase their anticorrosive properties. Stress generation during the spraying deposition process plays an important role in the behaviour of the coated steel against corrosion phenomena. (C) 2002 Elsevier B.V. B.V All rights reserved.

Electrochemical behaviour of heat-treated Al-Zn-Mg alloys in chloride solutions containing sulphate

The electrochemical corrosion and passivation of Al-5Zn-1.7Mg-0.23Cu-0.053Nb alloys, submitted to different heat treatments (cold-rolled, annealed, quenched and aged, and quenched in two steps and aged), in sulphate-containing chloride solutions, has been studied by means of cyclic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The cyclic polarization curves showed that sulphate addition to the chloride solution produced a poor reproducible shift of the breakdown potential to more positive potentials. The repassivation potentials, much more reproducible, and practically separating the passive from the pitting potential region, were slightly displaced in the negative direction with that addition. When the alloys were potentiodynamically polarized in the passive potential region, sulphate was incorporated in the oxide film, thus precluding chloride ingress. In addition, Zn depletion was favoured, whereas Mg losses were avoided. Different equivalent circuits corresponding to different alloys and potentials in the passive and pitting regions were employed to account for the electrochemical processes taking place in each condition. This work shows that sulphate makes these alloys more sensitive to corrosion, increasing the fracture properties of the surface layer and favouring the pitting attack over greater areas than chloride alone. (C) 2002 Elsevier B.V. Ltd. All rights reserved.