Passive and transpassive behaviour of Alloy 31 in a heavy brine LiBr solution

The passive and transpassive behaviour of Alloy 31, a highly alloyed austenitic stainless steel (UNS N08031), has been investigated in a LiBr heavy brine solution (400 g/l) at 25 °C using potentiostatic polarisation combined with electrochemical impedance spectroscopy and Mott-Schottky analysis. The passive film formed on Alloy 31 has been found to be p-type and/or n-type in electronic character, depending on the film formation potential. The thickness of the film formed at potentials within the passive region increases linearly with applied potential. The film formed at transpassive potentials is thinner and more conductive than the film formed within the passive region. These observations are consistent with the predictions of the Point Defect Model for passive and transpassive films on metals and alloys

Effect of Reynolds number and lithium cation insertion on titanium anodization

This work studies the influence of using hydrodynamic conditions (Reynolds number, Re = 0 to Re = 600) during Ti anodization and Li+ intercalation on anatase TiO2 nanotubes. The synthesized photocatalysts were characterized by using Field Emission Scanning Electron Microscope (FE-SEM), Raman Confocal Laser Microscopy, Electrochemical Impedance Spectroscopy (EIS), Mott-Schottky analysis (M-S), photoelectrochemical hydrogen production and resistance to photocorrosion tests. The obtained results showed that the conductivity of the NTs increases with Li+ intercalation and Re. The latter is due to the fact that the hydrodynamic conditions eliminate part of the initiation layer formed over the tube-tops, which is related to an increase of the photocurrent in the photoelectrochemical water splitting. Besides, the photogenerated electron-hole pairs are facilitated by Li+ intercalation. Finally, this work confirms that there is a synergistic effect between Re and Li+ intercalation

Effect of alloying elements on the electronic properties of thin passive films formed on carbon steel, ferritic and austenitic stainless steels in a highly concentrated LiBr solution

The influence of alloying elements on the electrochemical and semiconducting properties of thin passive films formed on several steels (carbon steel, ferritic and austenitic stainless steels) has been studied in a highly concentrated lithium bromide (LiBr) solution at 25 °C, by means of potentiodynamic tests and Mott-Schottky analysis. The addition of Cr to carbon steel promoted the formation of a p-type semiconducting region in the passive film. A high Ni content modified the electronic behaviour of highly alloyed austenitic stainless steels. Mo did not modify the electronic structure of the passive films, but reduced the concentration of defects

Synergistic effect between hydrodynamic conditions during Ti anodization and acidic treatment on the photoelectric properties of TiO2 nanotubes

In the present work, the combined influence of controlled hydrodynamic conditions during Ti anodization and the acidic treatment with HClO4 on the photoelectric properties of mixed anatase/rutile TiO2 nanotubes has been studied. Anodized samples were analyzed by means of Field Emission Scanning Electronic Microscopy (FE-SEM), Confocal Raman Microscopy, electrochemical measurements (electrochemical impedance spectroscopy and Mott-Schottky analysis) and photoelectrochemical measurements. It has been observed that the use of hydrodynamic conditions increases the surface area of nanotubes, while acidic treatment enhances their conductivity. Besides, there is a clear synergistic effect between the hydrodynamic conditions and the acidic treatment, which results in higher photocurrent densities for the treated nanotubes formed under hydrodynamic conditions.Authors would like to express their gratitude for the financial support to the Ministerio of Economia y Competitividad (Project CTQ2013-42494-R).Sánchez Tovar, R.; Fernández Domene, RM.; Martinez Sanchez, A.; Blasco Tamarit, ME.; García-Antón, J. (2015). Synergistic effect between hydrodynamic conditions during Ti anodization and acidic treatment on the photoelectric properties of TiO2 nanotubes. Journal of Catalysis. 330:434-441. https://doi.org/10.1016/j.jcat.2015.08.002S43444133

Thermogalvanic effects on the corrosion of copper in heavy brine LiBr solutions

Thermogalvanic corrosion of copper in heavy brine LiBr solutions has been investigated using a zero-resistance ammeter (ZRA). The temperature gradients between copper electrodes immersed in the same LiBr solution result in the formation of thermogalvanic cells with hot anodes, leading to high and sustained thermogalvanic currents. Copper loss rates, calculated using Faraday's law, substantially exceed 0.025 mm year−1, a value regarded as the threshold of low corrosion rates. The effects of thermogalvanic coupling on the surface properties of the anode and the cathode have been analysed by means of electrochemical impedance spectroscopy (EIS). The results obtained in this analysis have been related to the process of copper electrodissolution in bromide media

Implementation of a problem-based learning methodology to a chemical engineering master course

[EN] Problem-Based Learning (PBL) is a teaching methodology which uses comprehensive real-world problems to introduce the different concepts of the course to students. In this way, PBL methodology tries to develop, among others, problem-solving abilities, communication skills, critical thinking skills, and, the most important, it can promote life-long learning. PBL methodology was introduced to design the classes of a corrosion course. Corrosion is a course which belongs to the Master of Chemical Engineering and to the Master of Industrial Security and Environmental of the Universitat Politècnica de Valencia (Spain). In this study it is explained how PBL methodology was designed to cover all the concepts of the course in order that students could acquire generic, technical and specific competences. The crucial part to succeed in the implementation of the PBL methodology is the design of the problems. In the study it is detailed how problems were designed and the main difficulties found during the implementation of the methodology in the corrosion course.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.Sánchez-Tovar, R.; Fernández-Domene, R.; Muñoz-Portero, M.; Garcia-Anton, J. (2019). Implementation of a problem-based learning methodology to a chemical engineering master course. IATED. 155-161. https://doi.org/10.21125/inted.2019.0077S15516

Design of a survey to evaluate problem-based learning methodology in a corrosion course

[EN] Problem Based Learning (PBL) methodology was introduced for the first time in a Corrosion course from the Master of Chemical Engineering of the Universitat Politècnia de València, Spain. Different problems involving all these concepts were designed and presented as primary learning methodology over the entire course. This work is focused on the design of a survey for the students in order to: first, know their opinion about the PBL methodology, indicating the advantages and main drawbacks of it and, second, know if this methodology motivates students to seek out a deeper understanding of concepts. This study presents the survey used to evaluate the PBL methodology used during the corrosion course and discuss the obtained results. It is important to point out that this was the first time that students face up to this kind of methodology in university but the general opinion about the methodology is very positive.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.Sánchez-Tovar, R.; Fernández-Domene, R.; Lucas-Granados, B.; Blasco-Tamarit, E.; Garcia-Anton, J. (2019). Design of a survey to evaluate problem-based learning methodology in a corrosion course. IATED. 162-165. https://doi.org/10.21125/inted.2019.0078S16216

Influence of annealing atmosphere on photoelectrochemical response of TiO2 nanotubes anodized under controlled hydrodynamic conditions

[EN] The influence of three annealing atmospheres (air, nitrogen and argon) and the use of controlled hydrodynamic conditions (from 0 to 5000 rpm) on morphological, structural, chemical and photoelectrochemical properties of TiO2 nanotubes have been evaluated. For this purpose, different characterization techniques have been used: Field Emission Scanning Electron Microscopy, Raman Confocal Laser Spectroscopy, X-Ray Diffraction, X-Ray Photoelectron Spectroscopy, Incident Photon-to-electron Conversion Efficiency measurements, ultraviolet-visible absorption spectra, Mott-Schottky analysis and photoelectrochemical water splitting tests. According to the results, it can be concluded that both hydrodynamic conditions and annealing in non-oxidizing atmospheres improve the photoelectrochemical response of the TiO2 nanotubes. This fact has been attributed to the oxygen vacancies formed after annealing in argon and nitrogen atmospheres and also to the presence of nitrogen into the TiO2 lattice due to the thermal treatment in the nitrogen atmosphere.The authors would like to express their gratitude for the financial support to the "Generalitat Valenciana (GV/2020/044) " as well as to the "Agencia Estatal de Investigacion" (Project Code: PID2019-105844RB-I00/AEI/10.13039/501100011033) ", for its help in the Laser Raman Microscope acquisition (UPOV08-3E-012) and the co-finance by the European Social Fund. Authors from UV also thank MINECO (MAT2017-84118-C2-1-R project) and FEDER for funding.Blasco-Tamarit, E.; Solsona, B.; Sánchez-Tovar, R.; García-García, D.; Fernández Domene, R.; Garcia-Anton, J. (2021). Influence of annealing atmosphere on photoelectrochemical response of TiO2 nanotubes anodized under controlled hydrodynamic conditions. Journal of Electroanalytical Chemistry. 897:1-13. https://doi.org/10.1016/j.jelechem.2021.11557911389

Enhancement of photoelectrochemical activity for water splitting by controlling hydrodynamic conditions on titanium anodization

This work studies the electrochemical and photoelectrochemical properties of a new type of TiO2 nanostructure (nanosponge) obtained by means of anodization in a glycerol/water/NH4F electrolyte under controlled hydrodynamic conditions. For this purpose different techniques such as Scanning Electronic Microscopy (SEM), Raman Spectroscopy, Electrochemical Impedance Spectroscopy (EIS) measurements, Mott-Schottky (M−S) analysis and photoelectrochemical water splitting tests under standard AM 1.5 conditions are carried out. The obtained results show that electron-hole separation is facilitated in the TiO2 nanosponge if compared with highly ordered TiO2 nanotube arrays. As a result, nanosponges enhance the photoelectrochemical activity for water splitting