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This work introduces a sustainable alkaline membrane fuel cell, SAMFC, stack. The SAMFC includes a reactor that uses recycled aluminum to break the water molecule via the oxidation of aluminum catalyzed by NaOH in order to generate hydrogen to feed system. A cellulosic membrane supports the liquid electrolyte. CO2 purified air is obtained from atmospheric air that is filtered by a KOH solution, so that potassium carbonate is not formed. The prototype consisted of a four single alkaline membrane fuel cells, AMFC, the H2-producing reactor, and the CO2 purifier. The SAMFC performance is evaluated via direct voltage and power. Although residual Al from soda cans was utilized, the results showed that the SAMFC stack delivered a maximum 3.77 V (I = 0 A) and 2.70 W of maximum power, which is only 18% lower than the same AMFC stack fed with pure H2. In parallel, a simplified SAMFC stack transient mathematical model numerical results were validated by direct comparison to experimental data. A parametric analysis investigated the impact of electrolyte KOH mass fraction variation (y = 20%, y = 40%, and y = 50%) on performance, showing that there was an optimal condition, yopt = 40% w/w, for maximum SAMFC net power output, which was the adopted value in this work's experiments. Remarkable is that the maximum is sharp, since the net power drops by ∼42% with y = 50% w/w, and by 50% with y = 20% w/w in comparison to y = 40% w/w. It is concluded that in situ sustainable H2 generation coupled with the fuel cell stack showed potential to be a viable sustainable power generation system in the near future, mainly if operating at the herein found optimal operating conditions.

Metallic implants with Harmonic Structure has been reported to perform better mechanical properties compared to traditional microstructure on several biomedical alloys. Researchers have shown mechanic improvement when obtaining this microstructure but, there is a literature gap about the electrochemical behavior of these alloys related to harmonic microstructure obtainment. Thus, in this paper, the HS Ti6Al4V was obtained by Spark Plasma Sintering in order to be compared on its electrochemical behavior to commercial α + β Ti6Al4V ELI (Extra Low Interstitial), which is one of the most studied alloys for implants due to its biocompatibility and because of its good relation of the mechanical and electrochemical properties. Optical microscopy was conducted to verify the morphology and microstructure of the alloys, X-ray diffraction analyses to crystalline phase determination. For the electrochemical stability analysis, Open Circuit Potential curves were obtained in chloride media followed by voltammetry profile analysis on simulated blood solution, finally, the electrical parameters of the corrosion process were obtained using Electrochemical Impedance Spectroscopy. The results indicated that the materials presented a very similar electrochemical behavior with high polarization resistance, with almost no difference in the values of the curves, indicating there is no inference on the electrochemical behavior or corrosion resistance from the Ti6Al4V alloy with the harmonic structure.

Benzotriazole (BTA) release from a layered double hydroxide based on Zn and Al (LDH-ZnAl/BTA) in a saline solution was investigated using UV-Vis spectroscopy, and corrosion protection was studied b...

Chitosan-based organic-inorganic bio-hybrid nanocapsules, containing benzotriazole, a corrosion inhibitor, were prepared. In view of the versatile chemistry of silicon and the pH sensitivity of chitosan and benzotriazole, two synthesis approaches are presented. In both methods, tetraethoxysilane (TEOS) was used as the silicon source. Particles with different architectures, structural features and pH-dependent release behavior were obtained. The capsules prepared by the sol-emulsion-gel method demonstrated the highest release efficiency at pH 7.0 (∼90%) and pH 9.0 (∼65%) whilst the capsules prepared through layer-by-layer deposition technique showed the best efficiency at pH 3.0 (∼90%). Therefore, in combination, the particles delivered benzotriazole in a wide range of pH (from 3 to 9). The materials were fully characterized at the molecular, mesoscopic and nanometric length scales and the results suggest that they can successfully be applied in pH-sensitive smart coatings for corrosion inhibition.

The 2524-T3 aluminium (Al) alloy produced by ALCOA may be used as skin material by the aircraft industry. Some studies are available in the literature about fatigue and fatigue - corrosion behaviour of 2524-T3 Al alloy. However, the corrosion mechanisms are not yet fully understood since the material has a very complex microstructure due to impurities and the addition of alloying elements which lead to an increase in the localized corrosion process. It is known that the corrosion process in Al alloys, most of the time, is due to the galvanic coupling of the intermetallic particles (IMs) and the Al matrix. Thus, the use of protective coatings appears as a possible alternative against the advancement of the corrosion process of the 2524-T3 alloy. In this way, a set of DLC films was obtained by using physical vapor deposition (PVD) method and characterized by various techniques including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Atomic force microscopy (AFM) and Raman spectroscopy. The deposited films on the surface of the 2524-T3 Al alloy were characterized electrochemically by using potentiodynamic polarization curves (PPc), electrochemical impedance spectroscopy (EIS) and mechanically by using micro-abrasive wear tests (MAWTs). The results show an advantage in using the PVD method to produce thin films on the 2525-T3 Al alloy surfaces, as the wear resistance of the Al alloy coated by DLC film is higher than for the bare material and the corrosion resistance of the material is not compromised. DOI: http://dx.doi.org/10.17807/orbital.v11i2.1321

Over the past years, the use of layered materials such as clay minerals, layered double hydroxides, and layered hydroxide salts, as nanocontainers of corrosion inhibitors has grown, and these materials have proved to be very advantageous to improve the corrosion protection of metallic surfaces. The layered materials are especially advantageous for this application due to their capacity of not only releasing corrosion inhibitors on-demand to protect the metal but also capturing ionic aggressive species from the medium. The diversity of corrosion inhibitors species that can be intercalated in the interlayer space of these materials and the possibility to synthesize different layered materials (composition, structure, and morphology), using different methods, provide a high versatility to produce efficient protective systems, which are elucidated and discussed in this review. Moreover, a section on future perspectives is presented, indicating promising and still underexplored possibilities for future development trends in using layered materials for corrosion protection applications. published

The use of smart nanocontainers to store corrosion inhibitors in coatings significantly increases the efficiency and durability of the coating, providing active corrosion protection. Here we report the synthesis of a zinc-layered hydroxide salt (LHS) and its use as a novel nanocontainer for this purpose, storing the corrosion inhibitor molybdate in the interlayer region of the LHS. Layered zinc hydroxide molybdate (ZHM) was obtained by anion-exchange reactions using layered zinc hydroxide acetate (ZHA) as a precursor, obtained by alkaline coprecipitation. The release behavior of molybdate from the ZHM nanocontainers in aqueous NaCl solution (0.05 mol/L) was evaluated using UV-vis absorption spectroscopy. The molybdate release from the ZHM nanocontainers was realized by the anion-exchange mechanism, where chloride anions replaced intercalated molybdate anions. The release was fast in the first minutes of exposure, followed by a controlled release afterward, reaching about 35% of cumulative amount of released molybdate after 30 days of exposure. The anticorrosion effect provided by the ZHM nanocontainers for carbon steel was investigated by electrochemical impedance spectroscopy. The steel substrate was coated with an epoxy resin loaded with ZHM nanocontainers (5 wt %) and immersed in an NaCl solution (0.05 mol/L) to evaluate the active mechanisms of inhibition and the anticorrosion properties of the loaded coating in comparison with a neat coating (blank). The coating loaded with ZHM nanocontainers presented the best corrosion protection performance, exhibiting an increase of RC (coating resistance) with the immersion time and superior RP (polarization resistance) for all the measured periods, compared to the blank. This effect is a consequence of the double mechanism of protection provided by the ZHM nanocontainers: (i) stimulus-response release of molybdate and its active inhibition in the scratched region by the formation of an insoluble protective film, simultaneously with (ii) removal of the corrosive chloride species from the medium.

During the last decades, researchers have been growing the interest in surface treatment with an antimicrobial agent. Silver nanoparticles (AgNPs) are widely used in biomedical fields due to their potent antimicrobial activity. So, in this study was investigated silver particles (isles) coated on titanium surface for dental and orthopedic application. Silver particles coating process on titanium surface were performed via sputtering that is a plasma-assisted deposition technique with and titanium without treatment was applied as comparing standard. Plasma treatment parameters were optimized so that the result was not a thin film of Ag but dispersed particles of Ag on the Ti-cp surface. The alloy surfaces were investigated using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). In order to investigate antibacterial potential Staphylococcus aureus and Escherichia coli have been used at Agar diffusion assay. The results were analyzed by analysis of variance (ANOVA) in order to verify significant difference antimicrobial activity between samples that have shown no difference between the surfaces studied treatments. For silver deposition scattered particles (isles) over titanium surface for a 10-minute treatment, EDS revealed by silver clusters that the particles were not properly scattered onto surface, hence, the low effectiveness in antibacterial activity. Durante las últimas décadas, los investigadores han aumentado el interés en el tratamiento de superficie con un agente antimicrobiano. Las nanopartículas de plata (AgNP) se usan ampliamente en campos biomédicos debido a su potente actividad antimicrobiana. Entonces, en este estudio se investigaron partículas de plata (islas) recubiertas en superficie de titanio para aplicaciones dentales y ortopédicas. El proceso de recubrimiento de partículas de plata en la superficie de titanio se realizó mediante pulverización catódica, que es una técnica de deposición asistida por plasma y se aplicó titanio sin tratamiento como estándar de comparación. Los parámetros de tratamiento con plasma se optimizaron para que el resultado no fuera una película delgada de Ag sino partículas dispersas de Ag en la superficie de Ti-cp. Las superficies de aleación se investigaron mediante microscopía electrónica de barrido (MEB) y espectroscopía de rayos X de dispersión de energía (EDS). Con el fin de investigar el potencial antibacteriano, se han utilizado Staphylococcus aureus y Escherichia coli en el ensayo de difusión en agar. Los resultados se analizaron mediante análisis de varianza (ANOVA) para verificar la diferencia significativa de la actividad antimicrobiana entre las muestras que no mostraron diferencias entre los tratamientos de las superficies estudiadas. Para las partículas de plata dispersamente depositadas (islas) sobre la superficie de titanio para un tratamiento de 10 minutos, EDS reveló al presentar grupos de plata que las partículas no se dispersaron adecuadamente en la superficie, por lo tanto, la baja efectividad en la actividad antibacteriana. Nas últimas décadas, os pesquisadores têm aumentado o interesse no tratamento de superfície com um agente antimicrobiano. Nanopartículas de prata (AgNPs) são amplamente utilizadas em campos biomédicos devido à sua potente atividade antimicrobiana. Assim, neste estudo foram investigadas partículas de prata (ilhas) revestidas na superfície de titânio para aplicação odontológica e ortopédica. O processo de revestimento das partículas de prata na superfície do titânio foi realizado por pulverização, que é uma técnica de deposição assistida por plasma e o titânio sem tratamento foi aplicado como padrão de comparação. Os parâmetros de tratamento com plasma foram otimizados para que o resultado não fosse um filme fino de Ag, mas partículas dispersas de Ag na superfície do Ti-cp. As superfícies das ligas foram investigadas por microscopia eletrônica de varredura (MEV) e espectroscopia de raios X dispersiva em energia (EDS). Para investigar o potencial antibacteriano Staphylococcus aureus e Escherichia coli foram utilizados no ensaio de difusão em ágar. Os resultados foram analisados por análise de variância (ANOVA), a fim de verificar diferenças significativas na atividade antimicrobiana entre amostras que não mostraram diferença entre as superfícies estudadas. Para partículas de prata dispersamente depositadas (ilhas) sobre a superfície de titânio para tratamento de 10 minutos, o EDS revelou, ao apresentar aglomerados de prata, que as partículas não foram adequadamente dispersas na superfície, logo a baixa efetividade na atividade antibacteriana.

Modified supermartensitic stainless steel surfaces were investigated as protective means against deterioration in Cl−- and H+-rich media. Nitrogen plasma immersion ion implantation at the 300–400 °C range produced top nitride-rich layers (with mainly γ′-Fe4N and e-Fe2-3N, but also with α′N, according to the treatment temperature) followed by underneath expanded martensite cases. The 400 °C nitrided sample presented the best performance in potentiodynamic polarization tests with NaCl electrolyte, featured by 4.3 times increase in the corrosion potential and the absence of pits, attributed to the thickest and continuous e-phase containing nitride-rich layer. The hydrogen embrittlement was assessed through cathodic hydrogenation tests. Both reference and 400 °C nitrided surfaces disclosed the phenomenon of intensified plastic flow under normal and tangential loadings. A decrease in hardness, elastic modulus and scratch resistance featured a ductile-to-brittle transition on the nitrided surface, possibly due to improved hydrogen trapping by nitride species with subsequent effects in plasticity. In summary, while the nitride layer played an advantageous role in protecting SMSS from chlorine attack, it was susceptible against the hydrogen corrosion.

Background: In the last 40 years, scientific efforts were focused on the efficiency improvement in organic photovoltaic devices. Bleaching agents were used to absorb UV light and convert it into lower energy radiation appear as potential candidates for further improvements. The present contribution investigated the effect of adding umbelliferone to poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) on its optical and electrical properties. Methods: Characterizations were performed under various umbelliferone concentrations. Fluorescence decay lifetimes were obtained using a MicroTime 200 system (PicoQuant). The UV–vis absorption spectra were obtained with a GE Healthcare Ultrospec 2100 pro Spectrometer. The electrical conductivity measurements as a function of temperature using a cryostat model ARS CS202AE-DMX-1AL. Results: The absorbance increases around 325 nm and decreases in the near infrared s the umbelliferone concentration is increased. It also decreases the absorption in the visible spectrum, concomitantly with a significant increase in the UV region. The electrical conductivity for the umbelliferone doped PEDOT:PSS films display an increase with increasing temperature, but does not follow a linear behavior with the increase of umbelliferone concentration in the films. Conclusion: It was shown that the absorbance displays a redshift in doped samples, while photoluminescence experiments demonstrated that UV light is converted to the visible spectrum more efficiently, which is a desirable feature for photovoltaic devices. Also, the electrical conductivity of PEDOT:PSS is increased for moderate umbelliferone concentrations.

Microcapsules containing linseed oil were synthesized by in situ polymerization method and benzotriazole was entrapped between polyelectrolytes layers assembled outside the microcapsules, using the Layer-by-Layer technique. The prepared microcapsules presented mean number diameter of 2.08 μm and released greater amount of benzotriazole in slightly acidic NaCl solution. The corrosion protection effect of the microcapsules was evaluated using a carbon steel substrate coated with an epoxy resin loaded with the microcapsules (4.8 wt%). Electrochemical impedance spectroscopy demonstrated the best performance of the loaded coating when compared to a control due to the stimuli-responsive release of linseed oil and benzotriazole.

The influence of nitrogen plasma immersion ion implantation (N-PIII) on the corrosion mechanisms of austenitic, duplex, martensitic and ferritic stainless steels (SS) was evaluated through open circuit potential, cyclic voltammetry and electrochemical impedance spectroscopy. The nitrided SS exhibited high hardness (>1000 HV0.01) and high corrosion resistance, evidenced by transpassive potential increase and polarization resistance values on the order of 106 Ω cm2. Expanded phases developed a diffusion mechanism within the passive film of the austenitic and duplex SS, whereas iron nitrides provided a barrier against corrosion, inhibiting localized corrosion on the ferritic SS and inducing uniform corrosion on the martensitic SS.

The Ti6Al4V alloy has been applied in situations where mechanical strength, corrosion resistance and biocompatibility are the concern, as in permanent biomedical implants. These material properties are straightly correlated with the microstructure morphology as grain size and crystallographic phases, which is very dependent of the thermal mechanical history and the chemical composition. The Ti6Al4V harmonic structure was primarily achieved by means of Mechanical Ball Milling (MBM) and Spark Plasma Sintering (SPS) using pre-alloyed powder from the plasma rotating electrode processes (PREP). This work aimed at developing the harmonic microstructure by MBM and SPS using pre-alloyed gas atomized powder (GAP). The chemical composition, the microstructure and the hardness were evaluated for the sintered samples and for the commercial wrought annealed conditions, for comparison. The harmonic structure obtained consists of cores containing alpha lath coarse grains surrounded by a three-dimensional network of fine equiaxial grains, while the wrought material shows equiaxial alpha grains in a matrix of beta phase microstructure. The sintered material revealed higher hardness than the wrought alloy.

The aim of this work was to study the corrosion process of new aluminium alloy AA2524-T3 (Solution Heat Treated and Cold Worked), which is a promising substitute of the base line AA2024-T3 for aircrafts fabrication, by global and localised techniques in sodium chloride medium (0.05 mol L-1 NaCl). The open circuit potential results revealed a stochastic evolution of pitting events and to the resulting variations in the ratio of passive/active areas and/or cathode/anode, which may be related to the presence of different types of intermetallics. The cyclicvoltammetry showed that the corrosion potential (Ecorr) and the pit nucleation potential (E pit) values are quite similar (approximately -0.525 V). The results of EIS show that the corrosion rate is quite stable, with no tendency to increase or decrease for longer immersion periods. The results of SVET were in agreement with the results obtained by EIS technique, showing strong anodic activity on the surface with no repassivation along the whole immersion time. Besides, corrosion process led to significant surface degradation after 24h.

It’s proposed a single methodology for the encapsulation of Aloe vera oil or microalgae fatty acids using the complex coacervation process between gelatin and gum arabic. Although a very recurrent method, it is not trivial to establish a single coacervation methodology to encapsulate different compounds. The optimal synthesis conditions, that resulted in the best yield and encapsulation efficiency, are 1:1 (m/m) wall-to-core ratio, a temperature of 40°C and agitation speed of 10,000 rpm. Optical microscopy analysis revealed that the microcapsules are spherical, have average diameters of 112 μm (A. vera) and 118 μm (microalgae) and do not form agglomerates. The microcapsules were characterized by the osmotic pressure at which they ruptured, allowing the calculation of their mechanical resistance, which resulted in 392 MPa (A. vera) and 425 MPa (microalgae). The presented optimized methodology to encapsulate both compounds aims to contribute to their efficient and rational use, especially in cosmeceutical applications.

Degenerative diseases, such as osteoarthritis, osteoporosis and accidents can cause hip problems and injuries leading to a necessary hip prosthetic replacement. Acetabular and femoral prosthesis parts, consisting of special alloys of steel and titanium, are fixed to the bones using orthopedic cement based on poly(methyl methacrylate) (PMMA). With aim of improving implant material properties in terms of compatibility with the human body, were evaluated the bioactive responses of ISO 5832-9 steel and Ti6Al4V alloy coated with electrospun PMMA nanofibers. The electrospinning technique is widely used due to the possibility of easily producing fibers within nano or micrometric scale using a low cost, simple experimental apparatus that allows large-scale production. In this work the metallic substrates were submitted to surface pretreatments with sanding alone or in combination with acid etching. After deposition by electrospinning, the surfaces were characterized morphologically, chemically, and for roughness. PMMA fibers were obtained, with nanometric diameter, forming a uniform and homogeneous layer over both metal sample surfaces without appreciable differences in adhesion. The sanded surface, being a one-step process, was chosen for the next step. Fibroblasts were grown on the sample surfaces, for seven days, to determine biocompatibility. Electrospinning Induced Surface Activation (EISA) was used to incorporate hydroxyl radicals into the PMMA chain to produce hydroxylated PMMA, that was later redissolved and electrospun into nanofibers. Both samples (PMMA and PMMA-OH nanofibers) resulted in good cell adhesion properties. However, a denser cell monolayer was observed on the hydroxyl-terminated sample, indicating better cell-material interaction. Hydroxyl (OH) functionalized molecules can regulate cell behavior acting as a linker capable of reacting with proteins, thus accelerating cell growth, migration, differentiation, synthesis of extracellular matrix components, and tissue morphogenesis. By a simple two-step methodology it was possible to obtain electrospun hydroxyl functionalized bioactive PMMA nanofibers deposited on metallic implant samples with an increased cell response.

Concretes with 1% nano-Fe 3 O 4 addition aged for 300 days in chloride and sulfur dioxide chambers were analyzed by multiple technics and the performance results were evaluated by impedance spectroscopy and cyclic voltammetry. They exhibited a higher electrochemical stability because of the absence of passive film breakdown and an enhanced electrical resistance to charge transfer. The better properties were resulted from a more homogeneous microstructure produced by the byproducts of the reaction between the cement hydrates and the added nano-material. They were supposed be accumulated in pores and voids.

Dual-functional poly(urea-formaldehyde) microcapsules, containing the healing agent linseed oil in the core and the corrosion inhibitor benzotriazole (BTA) in the multilayer shell, were synthesized by in situ polymerization. A layer-by-layer assembly technique was applied using the biopolymers alginate and chitosan as oppositely charged polyelectrolytes. The microcapsules were characterized concerning their composition, surface charge, and morphology, using FTIR, TG, zeta potential measurements and SEM. The capsules are spherical, with an average diameter of 0.99 ± 0.15 μm. The encapsulation of linseed oil was confirmed by FTIR and TG. The adsorption of the multilayers was monitored by zeta potential measurements. The release of BTA, in a solution of NaCl and at different pH values, was studied by UV–Vis spectrophotometry, showing the stimulus-responsive behavior of the microcapsules. The corrosion protection performance was investigated by electrochemical impedance spectroscopy (EIS), using a carbon steel substrate coated with epoxy resin loaded with 5 wt% microcapsules. The EIS results showed that the presence of microcapsules provided better protection compared to the pure resin coating, with average RP three times higher.

Gordaite (NaZn4(OH)6SO4Cl·6H2O) is a mineral from the layered hydroxide salts (LHS) family that presents both cation- and anion-exchange properties, which is rare in this class of materials, having then called much attention lately due to its interesting potential applications. Sharing similar layered structure and composition, gordaite’s non-cation-exchanger analogous such as osakaite (Zn4(OH)6SO4·5H2O) and simonkolleite (Zn5(OH)8Cl2·H2O) show the possibility of interconversion reactions, in dynamics that might be of interest in technological applications such as corrosion protection. The materials can act as stimuli-responsive nanocontainers for storing corrosion inhibitors between the layers that might then be released on demand and avoid corrosion reactions on metals and alloys. In this work, we study the different methodologies for obtaining these LHS by synthesizing them by the oxide hydrolysis, co-precipitation by increasing pH and electrochemical methods, and comparing the obtained results.

Biopolymeric microspheres containing corrosion inhibitor benzotriazole (BTA) were prepared by a spray-drying technique using carboxymethylcellulose (CMC-Na) as encapsulating material. The resulting microspheres were characterized by FTIR, TGA, SEM and TEM analysis. Microspheres containing BTA have an average diameter of 1.1 μm. FTIR analysis confirmed the presence of the core and encapsulating components. The release studies by UV−Vis spectrophotometry showed that the mechanism of inhibitor release from CMC-Na biopolymeric matrix is based on a hydrogel-swelling-driven mechanism triggered by water presence. Electrochemical impedance spectroscopy (EIS) measurements on bare carbon steel in NaCl solution revealed that the presence of CMC-Na does not affect the corrosion inhibition mechanism associated with BTA. Furthermore, the microcapsules were added to an epoxy coating and its active corrosion protection performance was also investigated by EIS. The results obtained indicate that capsules loaded with BTA do not affect negatively the barrier properties of the coating, and contribute for the enhancement of the corrosion protection of the metallic substrate. Therefore, this work shows the potential application of carboxymethylcellulose microspheres for development of new environmentally-friendly microcontainers for corrosion inhibitors.

Several studies regarding superficial treatments of Nitinol (NiTi) shape-memory have been developed aiming to the improve corrosion resistance and to block the Ni release to adjacent tissues. The necessary heat treatment to achieve the shape memory effect normally occurs at temperatures between 500 and 600 °C. However, titanium oxide (TiO2) is formed on the NiTi surface during the shape memory process heat treatment. In this work the effects of the heat treatment time on the surface characteristics of the formed NiTi oxide, at temperatures that promote the shape-memory (530 and 570 °C), were evaluated. The TiO2 layers which were obtained were evaluated by X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscope (SEM), thermogravimetric analysis (TGA), wettability and roughness. The results show that by increasing the exposure time at the temperature of 570 °C the formation of a thicker oxide is promoted, with less superficial roughness and of a hydrophobic nature. According to the literature, these characteristics indicate that the obtained oxide layer has properties that accelerat the osseointegration process.

To improve the implants biocompatibility many surface modifications were proposed. Investigations about the surface modification on Ti alloys by anodic oxidation are reported. This research presents a study on the stability of thin titanium dioxide grown by potentiodynamic method on Ti6Al4V surfaces up to 5.0 V. Its bioactive surface in phosphate buffer solution (PBS) and the oxide stability after immersion in artificial blood media were measured by Electrochemical Impedance Spectroscopy (EIS). Hydroxyapatite (HAP) presence was evaluated using simulated body fluid (SBF) with different immersion times. The oxides and HAP presence were analyzed by Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The oxide stability was confirmed with low dissolution rates where the Rp was around 106Ω.cm2. The results showed the TiO2 was compact and thin oxide that could prevent the severe corrosion processes and improve in few days the physical-chemical interaction of the Ti alloys with bone in physiological media.

In order to improve the NiTi alloy biocompatibility, surface treatments become very important. Nevertheless, researchers use different solutions to simulate the body fluids in electrochemical assays, and the correlation between the obtained results is difficult and might not even be possible. The present paper evaluated the electrochemical behavior of polished NiTi surfaces exposed to different simulated body fluid solutions: Hanks solution, Hanks’ balanced salt (HBSS) solution, saline body fluid (SBF) solution, and Ringer solution. The electrochemical behavior of NiTi was evaluated by open circuit potential (OCP) and cyclic voltammetry tests. The surfaces of the samples were also characterized by scanning electron microscopy, which was performed after the electrochemical tests. The results demonstrated that the NiTi alloy shows the same corrosion mechanism (pitting) in all simulated body fluids that were studied. However, the corrosion potential changes for each electrolyte, being HBSS, SBF and Ringer the most corrosive solutions. Furthermore, the Hanks and HBSS solutions demonstrated good reproducibility of the electochemical results. Considering that the HBSS represents an extreme environment, this solution seems to be the most indicated to study the corrosion behavior of NiTi treated surfaces.

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

Samples of reinforced mortar specimens (Sps) were studied over 300 days of exposure in reference, sulfate, and chloride environments. Electrochemical impedance spectroscopy (EIS) was used to investigate external sulfate attack (ESA) in comparison with known chloride models. The study, based on the mortar behavior and its measured electrical properties, highlighted the mechanisms that occur under the pores during the aging. The sulfate samples presented a capacitive behavior at lower frequencies, and the mortar resistance shifted. It was confirmed that EIS is a qualified technique to identify the sulfate attack in concrete by non-destructive methods.

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.

Titanium and its alloys are biomaterials used in endosseous implants, due to desirable mechanical properties, high corrosion resistance and biocompatibility. Using electrochemical anodization technique these materials can be recovered with self-organized TiO2 nanotubes layer resulting in increased specific surface area and probable bioactivity improvement. This research aimed determine potentiostatic anodization parameters to obtain self-organized TiO2nanotubes layer with reproducibility and ideal diameters for probable bioactive response on Ti - 2 grade (ASTM F67) and Ti6Al4V (ASTM F136) orthopedic alloy and evaluation the electrochemical stability behavior in simulated body fluid media. The self-organized nanotubes layer were obtained by potentiostatic electrochemical method in electrolyte containing fluoride ions, H3PO4/HF for Ti 2 grade and H3PO4/NH4F for Ti6Al4V alloy, the applied potentials were 15 V, 20 V and 25 V for 30, 60 and 90 minutes, for both materials. For morphologic characterization were employed scanning electron microscopy SEM and the Image J software for nanodiameter measurements. The nanoestructure electrochemical stability was evaluated by open circuit potential after immersion for 15, 30 and 60 days in artificial blood plasma, into an electrochemical cell, using SCE (saturated calomel electrode) as reference electrode, in PBS ((phosphate buffered saline) solution electrolyte for 90 minutes. The ideal anodization parameters were 15 V and 20 V for 1 hour and a reproducible, uniform and homogeneous self-organized nanotubes layer were obtained with ideal diameters that probably improve the implant superficial bioactivity with 80 and 120 nm respectively, according to the literature. Open-circuit potentials from metal/oxide system obtained on both materials are stable with potentials in range of -0.031 V to -0,183 V indicating good stability of nanoestructures in simulated body fluid. Nanotubes layer as a superficial treatment is viable with high reproducibility, low cost and electrochemical stability in simulated body fluid media.

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.

The influence of surface microstructure and chemical composition on the corrosion behavior of AISI 1045 (UNS G10450) plain steel modified by plasma-assisted diffusion of nitrogen and oxygen was investigated. A detailed surface characterization was performed before and after cyclic potentiodynamic polarization and salt spray tests, using scanning electron microscopy at low and high resolutions, energy-dispersive x-ray spectroscopy, x-ray diffraction, and glow discharge optical emission spectroscopy. The corrosion resistance as determined by cyclic potentiodynamic polarization was found to depend more strongly on the morphology and composition of the outermost oxynitride layer than on its thickness. For post-oxidation times below and above 90 min, the oxynitride layer presented defects that can act as pathways for corrosive species. The degradation of the corrosion resistance for longer processing times is through cracking of granules, which were previously formed at shorter times owing to the hydrogen accumulation at the oxide-nitride interface. The salt spray tests revealed a main dependence on the manganese sulfide (MnS) inclusions content in the base material.

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.

This paper aims to produce a dynamic model that is computationally fast to predict the response of the single AMFC according to variations of physical properties of the materials, and operating and design parameters. The model is based on electrochemical principles, and mass, momentum, energy and species conservation. It also takes into account pressure drop in the gas channels and the temperature gradient with respect to space in the flow direction. The simulation results comprise temperature distribution, net power and polarization curves, which were experimentally validated by direct comparison to voltage and current measurements performed in a cellulose-based AMFC prototype for different electrolyte (KOH) solution concentrations (y), showing good quantitative and qualitative agreement. It is concluded that the startup transient is short and that there are optimal values of y (∼40 wt. % ) which lead to maximum power, that are herein shown experimentally for the first time. In the process, the model was used to formulate empirical correlations for the exchange current density (i0) in the electrodes with respect to the electrolyte concentration for future fuel cell development. Therefore, the adjusted and validated model is expected to be a useful tool for AMFC control, design and optimization purposes.

BACKGROUND: Microalgae have recently been considered a potential feedstock for biodiesel production, since they do not compete with agricultural land, unlike oil crops. However, the production processes must be energetically and economically viable. Therefore, an in situ methanolysis process is proposed for biodiesel production directly from microalgae biomass, to avoid the need for the separation and extraction steps. RESULTS: Biodiesel was obtained using methanol as the methylation reactant for the transesterification reaction and hydrochloric acid as the catalyst precursor, at 80 °C for 2 h of reaction. A mass return of 23.07 ± 2.76% (m/m) was obtained. Spectrometry in the infrared region showed that the product had equivalent bands of axial deformation of CO, CO and CH, i.e. an ester. Tests showed the chromatographic profile of fatty acids in the sample. A process energetic efficiency value of 1.17 was obtained for microalgae derived biodiesel, which is higher than from soybean and sunflower, reportedly 1.06 and 1.12. CONCLUSIONS: Industrial sustainability results from low energetic, economic and environmental losses. The microalgae in situ methanolysis process showed greater fuel available energy than energy consumption, therefore is energetically sustainable. Economic and environmental issues should still be addressed. Copyright © 2011 Society of Chemical Industry

The stability of anodic films potentiodynamically grown on titanium, titanium-grade 2, and Ti6Al4V alloy was studied in a simulated physiological electrolyte, up to 8.0 V, and at room temperature to determine the corrosion resistance levels of dental implants. In PBS (phosphate buffer saline) solution, thin titanium oxide films protect the surface of the Ti6%Al4%V alloy up to 6.0 V, pure Ti up to 8.0 V, and Ti-grade 2 up to 1.5 V. At more positive potentials, localized corrosion starts to occur possibly due to the alloy elements (Ti6Al4V-V and Al) and variable levels of interstitials (Ti-grade 2: C, N, and Fe, mainly). When the biomaterials were submitted to open-circuit conditions, in artificial saliva, the worst corrosion resistance was observed in dental implant (Ti-grade 2), according to the open-circuit potential values and reconstruction rate analysis of these oxide films. The XPS spectra revealed TiO2oxide as the main phase in the barrier oxide film coating the dental implant.

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.

Recycling of automotive batteries for the recovery of secondary lead is extremely important in Brazil, for the country does not possess large reserves of this metal. Lead is one of the most widely used metals in the world, but it is highly toxic, posing risks for humans and for the environment if not utilized or treated adequately. Industrial waste containing lead in Brazil are classified by the Brazilian Residue Code (NBR—10004:2004) as hazardous. The lead recycling process employed by the recycling industry in Brazil is the pyrometallurgical process in a rotary furnace. This process consists of four stages: (1) grinding of the battery to separate plastic, electrolyte and lead plates; (2) lead reduction in a rotary furnace; (3) separation of metallic lead from slag; and (4) refining of recycled lead. The purpose of this work is to propose process improvements aimed primarily at increasing production output by reducing the loss of lead in slag and particulates, thereby providing a healthier work environment in line with Brazilian environmental and labor laws.

This paper presents the study of the electrodeposition of Fe–Mo from sodium citrate solutions at pH 4.0. The behaviour of the deposits was investigated by cyclic voltammetry (CV) for different Fe:Mo ratios and they were characterized by scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis. The XPS results show that, in the solution containing the least Fe, molybdate can only be reduced to a mixture of polyvalent molybdenum oxides and/or hydroxide. On the other hand, when the Fe concentration is higher, molybdate can be reduced to metallic Mo and the alloy can be obtained. However, for 10:1 molar ratio practically only Fe, as oxide and metallic iron, is deposited. In this case, the amounts of Fe–Mo alloy corresponding to 2% of the deposits. In all cases the deposits obtained consisted of the oxide layers doped with Fe–Mo. SEM analysis demonstrated that globular and compact deposits were obtained at higher Fe contents. Regular deposition is observed for Fe and Mo codeposition, at all molar ratios studied, since the Fe:Mo ratio in the alloy was lower than the corresponding [Fe(II)]/[Mo(VI)] ratio in solution.

The aim of this work is to study an electrochemical reactor using metallic particles as cathode for lead, copper and nickel ions recovery from acidified aqueous solutions for different process parameters as metallic ion concentration, current density and bed expansion. The reactor performance was evaluated considering the system efficiency and energy consumption. Taguchi method was selected as the statistical technique since it allows the main effects to be estimated with a minimum number of experimental runs. Moreover, it makes use of fractional factorial and orthogonal arrays to identify the factors, which present the greatest influence on the system, and the optimum factor setting for each experiment run. The highest current efficiency obtained were 75.8%, 89.9% and 30.3% for lead, copper and nickel, respectively.