Passivity Breakdown of Titanium in LiBr solutions

The passive behavior of titanium and its susceptibility to undergo localized attack in different LiBr solutions at 25 degrees C have been investigated using different electrochemical techniques: potentiodynamic polarization curves, potentiostatic passivation tests, EIS measurements and Mott-Schottky analysis. In low and moderately concentrated LiBr solutions, the breakdown potential E-b decreased with increasing bromide concentrations, while in highly concentrated LiBr solutions, E-b increased with increasing LiBr concentration. In the most concentrated LiBr solution (11.42M) Ti did not undergo passivity breakdown even at 9 V-Ag/AgCl. This observation can be explained by a a decrease in the activity of water in highly concentrated LiBr solutions. (C) 2013 The Electrochemical Society.We wish express our gratitude to the Ministerio de Ciencia e Innovacion (Project CTQ2009-07518), and to Dr. M. Asuncion Jaime. for her translation assistance.Fernández Domene, RM.; Blasco-Tamarit, E.; García-García, D.; García Antón, J. (2014). Passivity Breakdown of Titanium in LiBr solutions. Journal of The Electrochemical Society. 161(1):25-35. https://doi.org/10.1149/2.035401jesS25351611Been J. Grauman J. S. , in: Uhlig's Corrosion Handbook, 2nd ed., Winston Revie R. (ed.), 863-885, Wiley Interscience, New York (2000).Blasco-Tamarit, E., Igual-Muñoz, A., García Antón, J., & García-García, D. (2007). Corrosion behaviour and galvanic coupling of titanium and welded titanium in LiBr solutions. Corrosion Science, 49(3), 1000-1026. doi:10.1016/j.corsci.2006.07.007Huang, Y. Z., & Blackwood, D. J. (2005). Characterisation of titanium oxide film grown in 0.9% NaCl at different sweep rates. Electrochimica Acta, 51(6), 1099-1107. doi:10.1016/j.electacta.2005.05.051Pan, J., Thierry, D., & Leygraf, C. (1996). Electrochemical impedance spectroscopy study of the passive oxide film on titanium for implant application. Electrochimica Acta, 41(7-8), 1143-1153. doi:10.1016/0013-4686(95)00465-3Assis, S. L. de, Wolynec, S., & Costa, I. (2006). Corrosion characterization of titanium alloys by electrochemical techniques. Electrochimica Acta, 51(8-9), 1815-1819. doi:10.1016/j.electacta.2005.02.121Birch, J. R., & Burleigh, T. D. (2000). Oxides Formed on Titanium by Polishing, Etching, Anodizing, or Thermal Oxidizing. CORROSION, 56(12), 1233-1241. doi:10.5006/1.3280511Peláez-Abellán, E., Rocha-Sousa, L., Müller, W.-D., & Guastaldi, A. C. (2007). Electrochemical stability of anodic titanium oxide films grown at potentials higher than 3V in a simulated physiological solution. Corrosion Science, 49(3), 1645-1655. doi:10.1016/j.corsci.2006.08.010Azumi, K., & Seo, M. (2001). Changes in electrochemical properties of the anodic oxide film formed on titanium during potential sweep. 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Theoretical Analysis of the Effects of Alloying Elements on Distribution Functions of Passivity Breakdown. Journal of The Electrochemical Society, 136(4), 961. doi:10.1149/1.2096894Schmidt, A. M., & Azambuja, D. S. (2006). Electrochemical behavior of Ti and Ti6Al4V in aqueous solutions of citric acid containing halides. Materials Research, 9(4), 387-392. doi:10.1590/s1516-14392006000400008Brug, G. J., van den Eeden, A. L. G., Sluyters-Rehbach, M., & Sluyters, J. H. (1984). The analysis of electrode impedances complicated by the presence of a constant phase element. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 176(1-2), 275-295. doi:10.1016/s0022-0728(84)80324-1Valero Vidal, C., & Igual Muñoz, A. (2010). Study of the adsorption process of bovine serum albumin on passivated surfaces of CoCrMo biomedical alloy. Electrochimica Acta, 55(28), 8445-8452. doi:10.1016/j.electacta.2010.07.028Smart, N. G., & Bockris, J. O. (1992). 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Studies of collaborative audio-visual cases on educational television as education’s methodologies in European space of higher education

El trabajo que presentamos forma parte de una actividad académica realizada con alumnos de tercero de Pedagogía de la Facultad de Ciencias de la Educación de la Universidad de Sevilla. Este consistió en la realización de tres estudios de caso audiovisuales relacionados con la asignatura de Tecnología Educativa. Más concretamente, se realizaron tres vídeos en soporte DVD con la temática de la televisión educativa, tan comentada hoy en día debido a la gran proliferación de programas basura que existen en nuestra televisión. Hemos utilizado el medio vídeo con la intención de que los alumnos desarrollaran lo que creemos que debe ser una competencia del pedagogo, la de diseñador de escenas de aprendizaje. Por esta razón, los estudiantes han creado pequeños cortos a modo de viñetas con las que ilustrar qué es lo que se debe hacer con la televisión y lo que no, pretendiendo enseñar cómo se puede formar a las personas con y en la televisión. Al amparo de las reformas de las titulaciones y dentro del Espacio Europeo de Educación Superior, se definen las competencias del futuro pedagogo, como son el saber y conocer cómo se diseñan medios educativos, trabajando con el concepto de estudio de casos y con todos los pasos que se tienen que seguir para elaborar un vídeo didáctico (el guión técnico, el literario, la hoja de rodaje, la grabación, la edición etc.) los estudiantes han demostrado estar perfectamente capacitados al finalizar sus trabajos. Esta investigación ha pretendido demostrar cómo el trabajo con diseños de medios y materiales educativos, en concreto el medio vídeo, favorece el aprendizaje del alumno y les motiva a trabajar en grupo. También pretendemos describir, no sólo las ventajas, sino también los problemas o inconvenientes que conlleva el trabajar siguiendo esta dinámica de trabajo, el trabajar con falta de conocimientos y destrezas sobre el diseño, producción, posproducción y evaluación de materiales audiovisuales. Asimismo, hemos demostrado que tanto el aprendizaje adquirido por los estudiantes a través de estudios de caso audiovisuales, como la evaluación de los mismos, no es una tarea fácil, ni tiene una única respuesta. En esta tarea, creemos que deben confluir una serie de alternativas que debe seleccionar el profesor en función de los objetivos que persiga el curso y de la modalidad y tipo de formación en la cual nos estemos moviendo. Resulta curioso cómo los estudiantes plantean a lo largo de los vídeos interrogantes a modo de preguntas clave sobre los diversos comportamientos que se suelen dar, por ejemplo, en el ámbito doméstico cuando los hijos quieren ver un determinado programa o una serie en particular, y los padres se lo prohíben. Interrogantes que padres y educadores se hacen todos los días son: ¿cómo deben ver los padres la televisión con sus hijos?, ¿qué cosas se pueden hacer y cuáles se deben hacer con la televisión?, ¿qué cosas no se deben hacer con la televisión?, ¿es objetiva la televisión?, ¿cómo se puede solucionar la falta o la ausencia de objetividad de la televisión?, ¿por qué o para que se usa la televisión en las aulas?, ¿qué es la televisión educativa?The work that we presented is a part of one activity with students of third of Pedagogy studies of the Faculty of Sciences of the Education of the University of Seville. This consists in the accomplishment of three audio-visual studies of case related to the subject of Educative Technology. But concretely, three vídeos were produced in DVD with the thematic of the educative television, so commented today in day because to the great proliferation of programs sweepings that exists in our television. We have used the vídeo with the intention of which the students developed what we think that must be a competition of pedagogy: programmer of learning scenes. For this reason, they have created short recordings as a comic to illustrate what is correct to do with the television and what no, trying to teach to the people with television and in the television. Under defence of the reforms of the qualifications inside the European Space of High Education, are defined the competitions of the future pedagogue: to know how and to know are designed the educative resources, by means of the concept of study of cases and with all the steps that must follow to elaborate a didactic vídeo (the technical script, the literary one, the leaf of filming, the recording, the edition etc.) the students have demonstrated to be perfectly enabled when finalizing their works. This investigation has tried to demonstrate like the work with educative resources and educative materials, in concrete the vídeo, it favours the learning of the students, motivates them to work in group. Also we try to describe, no only the advantages, but also the problems or disadvantages that working entails following this dynamic of work, working with lack of knowledge and skills design, production, postproduction and evaluation of audiovisual resources. Also, we have show that as the acquired learning by the students through audiovisual studies of case, like their evaluations, is not an easy task, not has a unique answer. In this task, we think that a series of alternatives must come together to select by the professor in function of the objectives that persecutes the course and of the modality and type of learning in which we are practicing. Is peculiar as the students rise throughout the vídeos questions about the diverse behaviours that usually occur, for example, at home when the children want to see a certain program or a series, and the parents forbid it. Questions that parents and educators become all the days are: how the television must see the parents with their children?, what things can do and what must do with the television?, what things cannot do with the television?, the television is objective?, how can be solved to the lack or the absence of objectivity of the television?, why or so that is used the television in the classrooms?, what is the educative television

The case method: study of a corrosion problem

[EN] The aim of the present work is the application of the case method as teaching-learning methodology for the study of a corrosion problem, in order to obtain more active learning of the student. The educational innovation has been applied in 2018/2019 academic year in the subject of “Manufacturing Processes of Building Materials” imparted in the fourth course of the Chemical Engineering Degree in the Higher Technical School of Industrial Engineering in the Polytechnic University of Valencia. Such educational innovation consists in the description by the lecturer of a real situation about a corrosion problem, so that the students can analyse it and propose solutions individually and in group. At the end of the case it is added questions to help to the students in the analysis. This activity is realized in class, which is evaluated using a rubric. The evaluation of the educational innovation proposed is realized by the scores of the students, the polls of the students, and the autoevaluation of the lecturer. The results show the high scores obtained by the students in the case method and the high grade of satisfaction of the students after applying the educational innovation. The case method permits that the students know real situations that they could find in a professional future, which increase the motivation towards the subject of study.Authors would like to express their gratitude to the project PIME: Aprendizaje Basado en Problemas para su aplicación en las áreas de Ingeniería Química y de Materiales (Ref. 27) and to the Instituto de Ciencias de la Educación and the Vicerrectorado de Estudios, Calidad y Acreditación from the Universitat Politècnica de Valencia, for their financial and technical support.Muñoz Portero, MJ.; Sánchez Tovar, R.; Fernández Domene, RM. (2020). The case method: study of a corrosion problem. Editorial Universitat Politècnica de València. 249-257. https://doi.org/10.4995/INN2019.2019.10137OCS24925

Accompanied child irregular migrants who arrive to Spain in small boats: experiences and health needs

The European Union is the preferred destination of child irregular migrants arrived from northern Africa, who risk their lives crossing the Mediterranean Sea in small boats. Accompanied Child Irregular Migrants (AChIMs) are exposed to physical and psychological risk. The objective of our study is to describe and understand the experiences and health needs of AChIMs who arrive to Spain in small boats, through the testimony of adults who accompany them on the journey. A qualitative study, based on Gadamer's hermeneutic phenomenology, was performed. After obtaining approval from the Ethics and Research Committee, we conducted in-depth interviews on 32 adults who travelled with AChIMs. Two main themes emerged: (1) The journey a child should never have to take, with the subthemes 'AChIMs as a paradigm of vulnerability' and 'Crossing the sea, playing with death' and (2) Characterising emergency care to AChIMs, with the subthemes 'Prioritising specific care', 'Identifying high-risk situations' and 'The detaining of innocent children'. AChIMs, along with adults, risk their lives in such a dangerous and perilous journey, therefore, finding out about their experiences may contribute to improving the treatment of their specific health needs during the phases of rescue and emergency care

Comparison of the effect of non-polluted and underwater-volcano-polluted seawater on the corrosion resistance of different stainless steels

This work compares the effect of non‐polluted and underwater‐volcano‐polluted seawater on the electrochemical behavior of two different alloys, notably an austenitic stainless steel (SS) and a duplex stainless steel. Polarization measurements, potentiostatic passivation tests, electrochemical impedance spectroscopy and capacitance measurements were performed. Results show that the composition of the polluted seawater negatively affects the passivation kinetics of both AISI 316 SS and Alloy 900, decreasing the corrosion resistance of both alloys. Additionally, when both steels are compared, it can be concluded that passive films formed on Alloy 900 presented better protective properties than those on AISI 316 SS

Corrosion Behaviour of a Highly Alloyed Austenitic Alloy UB6 in Contaminated Phosphoric Acid

The influence of temperature (20-80°C) on the electrochemical behaviour of passive films anodically formed on UB6 stainless steel in phosphoric acid solution (5.5 M H3PO4) has been examined by using potentiodynamic curves, electrochemical impedance spectroscopy, and Mott-Schottky analysis. UB6 stainless steel in contaminated phosphoric acid is characterised by high interfacial impedance, thereby, illustrating its high corrosion resistance. The obtained results show that the films behave as n-type and p-type semiconductors in the potential range above and below the flat band potential, respectively. This behaviour is assumed to be the consequence of the semiconducting properties of the iron oxide and chromium oxide regions which compose the passive film

Influence of the Heating Rate on the Annealing Treatment of Iron Oxide Nanostructures Obtained by Electrochemical Anodization under Hydrodynamic Conditions

Iron oxide nanostructures are promising materials for photoelectrochemical applications such as water splitting. In this work, electrochemical anodization of iron is used to form different iron oxide nanostructures, and the influence of different anodization parameters was studied in order to find the most suitable nanostructure for photocatalysis applications. On the one hand, hydrodynamic conditions were evaluated by stirring the electrode at different rotation speeds during the electrochemical anodization to check their influence on the formation of the nanostructures. On the other hand, different heating rates during the annealing treatment were studied for obtaining efficient iron oxide nanostructures. The synthesized nanostructures were characterized by different techniques such as photocurrent density vs. potential measurements, Field Emission Scanning Electron Microscopy, Raman spectroscopy and Incident Photon-toelectron Conversion Efficiency (IPCE). The results revealed that the best heating rate during the annealing treatment is 15 ºC·min-1 and that the hydrodynamic conditions allow the formation of nanotubular iron oxide structures achieving ~0.1 mA·cm-2 at 0.5 V (vs. Ag/AgCl) in the water splitting measurements. Moreover, all the nanostructures are mainly composed by hematite (α-Fe2O3) with some amount of magnetite (Fe3O4) in their structure. Finally, the IPCE measurements showed that the best rotation speed during the electrochemical anodization for the formation of an efficient iron oxide nanostructure for photocatalysis applications is 1,000 rpm

Iron oxide nanostructures for photoelectrochemical applications: Effect of applied potential during Fe anodization

In photoelectrochemistry, a suitable photoanode leading to high efficiencies in photocatalytic processes is a research challenge. Iron oxide nanostructures are promising materials to be used as photoanodes. In this work, different potentials during iron anodization were applied to study the properties of the synthesized nanostructures. Results revealed that nanostructures anodized at 50 V presented well-defined nanotubular structures with open-tube tops, and they achieved values of photocurrent density of 0.11 mA cm−2 at 0 rpm and 0.14 mA cm−2 at 1000 rpm (measured at 0.50 VAg/AgCl), corresponding to the oxygen evolution reaction from water, i.e. 2H2O + 4 h+ → 4H+ + O2, demonstrating their good photoelectrochemical behavior

Effect of Temperature on Thermogalvanic Coupling of Alloy 31 in Libr Solutions Studied by Means of Imposed Potential Measurements

Corrosion resistance of Alloy 31, a highly alloyed stainless steel (UNS N08031) were studied in heavy brine LiBr solutions (400, 700 and 992 g/l) at different temperatures using electrochemical techniques. The mixed potential theory was used to evaluate thermogalvanic corrosion of Alloy 31 in the studied LiBr solutions. Potentiodynamic curves indicate that high temperatures favoured both cathodic and anodic processes, increasing passive current densities and decreasing the pitting potential. Generally, the cold electrode of the pair was the anode of the thermogalvanic cell

Formation of ZnO nanowires by anodization under hydrodynamic conditions for photoelectrochemical water splitting

The present work studies the influence of hydrodynamic conditions (from 0 to 5000 rpm) during Zn anodization process on the morphology, structure and photoelectrocatalytic behavior of ZnO nanostructures. For this purpose, analysis with Confocal Laser-Raman Spectroscopy, Field Emission Scanning Electron Microscope (FE-SEM) and photoelectrochemical water splitting tests were performed. This investigation reveals that hydrodynamic conditions during anodization promoted the formation of ordered ZnO nanowires along the surface that greatly enhance its stability and increases the photocurrent density response for water splitting in a 159% at the 5000 rpm electrode rotation speed