Corrosion Behavior of VM12-SHC Steel in Contact with Solar Salt and Ternary Molten Salt in Accelerated Fluid Conditions

Ternary low melting point mixtures with the addition of LiNO3 and Ca(NO3)2 have been presented as direct system candidates for CSP technologies due to having better physical and chemical properties than those of Solar Salt. In this study, thermal, physical and chemical properties are measured as is the corrosive behavior of stainless alloy VM12 (Cr 12%) when in contact with Solar Salt, 60% NaNO3-40% KNO3 (wt.%) and ternary 46% NaNO3-19% Ca(NO3)2-35% LiNO3 (wt.%). Gravimetric weight change measurements were performed on the test specimens, which were tested under accelerated fluid conditions (0.2 m s−1) at 500 °C for 2000 h. This research confirms the potential of this novel formulation as a thermal storage medium and validates the suitability of ferritic VM12-SHC stainless steel as a structural material for CSP technology with Solar Salt. Meanwhile, the results obtained by scanning electron microscopy and X-ray diffraction indicate a reduction in the protective character of the oxide layer formed on this alloy when the medium contains calcium and lithium components.Depto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasTRUEMinisterio de Ciencia, Innovaciónpu

Computational modelling of the local structure and thermophysical properties of ternary MgCl2-NaCl-KCl salt for thermal energy storage applications

Molten salts as heat transfer fluids (HTF) for concentrated solar power (CSP) plant application are considered as the best thermal storage medium, and more precisely molten chlorides, presenting a wide operating range and coupled with competitive cost. Furthermore, MgCl2-NaCl-KCl (MgNaK) mixture appeared as the most promising one but need further studies to better understand its thermophysical properties. Indeed, its hydrated form leads to the formation of corrosive compounds. In this research, two different methods are used to model the ternary mixture. The dehydration process is evaluated by thermodynamical calculations with Thermocalc software. Then, the local structure, thermal conductivity and viscosity are estimated by means of molecular dynamics simulation, with LAMMPS package. The results were close to past simulations studies and experimental references, but discrepancies need to be further minimized regarding some variable fluctuations

Corrosion study of Ni-based alloy in ternary chloride salt for thermal storage application

MgCl2/NaCl/KCl salt appeared as a high-potential heat transfer fluid for concentrated solar application, offering a wide operating range and low cost. Nevertheless, MgCl2 hydrates and atmosphere relative humidity are the limiting factors for a real scale CSP plant, leading to severe corrosion. Thus, Inconel 617 was tested at 700ºC up to 24 h in air atmosphere to simulate a punctual failure in the inertization system of a plant. XRD and SEM-EDX analysis showed unstable multilayers growing in cascade, highlighting chromium, aluminum, magnesium, and oxygen activities. Additionally, A radial growth of MgCr2O4 at the expense of MgO grains was visualized

Metodologías Activas para los “Cuidados de enfermería en el adulto con problemas en la eliminación urinaria y digestiva” de la asignatura Enfermería del Adulto III. Realidad Virtual para el marcaje del estoma

Dentro de la asignatura Enfermería de Adulto III hay un contenido denominado “Cuidados de enfermería en el adulto con problemas en la eliminación urinaria y digestiva”. El cuidado del estoma digestivo es una intervención principalmente de enfermería, por lo tanto, su formación y capacitación en este campo es imprescindible para garantizar la autonomía en los pacientes con estoma digestivo. Así pues, se hace necesaria la búsqueda y el establecimiento de las mejores prácticas pedagógicas para mejorar el aprendizaje y potenciar la formación de los alumnos de Grado en Enfermería para un desempeño autónomo y pertinente a las demandas sociales vinculadas al autocuidado de los pacientes con estoma digestivo. Por esta razón se elabora el presente proyecto, cuyo objetivo principal consiste en implementar las metodologías activas (MA) como estrategia didáctica para mejorar el nivel de enseñanza/aprendizaje en los estudiantes de Grado en Enfermería en el abordaje de las personas con estoma digestivo y analizar si estas metodologías mejoran su aprendizaje. Dentro de la gran variedad de métodos de aprendizaje activo, se ha seleccionado el Flipped Classroom (aula invertida), la Gamificación y la Realidad Virtual. El interés en estas MA se debe a su carácter innovador y por estar en pleno apogeo didáctico, además de los resultados relevantes mostrados en diferentes acciones formativas y los múltiples beneficios para el desarrollo del aprendizaje del alumno. Para alcanzar los objetivos propuestos, se organizará un seminario que se impartirá en los Campus Universitarios de Ceuta, Melilla y Granada. En una primera sesión se presentará el proyecto a los docentes encargados de la asignatura y se tendrá una primera toma de contacto con los alumnos, explicándoles cómo se va a desarrollar la acción formativa, así como la posibilidad de otorgar o no su consentimiento de participación. Tras finalizar la experiencia se llevará a cabo la evaluación de los resultados obtenidos, así como el impacto que han tenido las sesiones en los estudiantes a través de una encuesta de satisfacción

Substrate finishing and niobium content effects on the high temperature corrosion resistance in steam atmosphere of CrN/NbN superlattice coatings deposited by PVD-HIPIMS

The main objective of this work was to evaluate the oxidation resistance of three PVD-HIPIMS CrN/NbN coatings, studying the effect of the surface finishing of the substrate and the role of niobium content into the coating composition. CrN/NbN nano-multilayered films on P92 steel were tested at 650°C in pure steam atmosphere. The mass gain was measured at fixed intervals to study their oxidation kinetics. The morphology and thickness of nanoscales were measured by transmission electron microscopy (TEM). Characterization of coatings before and after the thermal treatment was performed by scanning electron microscopy-energy with facilities of dispersive X-ray spectroscopy (SEM–EDX) and X-ray diffraction (XRD). All coatings improved the oxidation resistance of the substrate material, but the best behaviour was exhibited by the CrN/NbN with the high niobium (Nb) content and deposited on the substrate with the finest surface finishing

Past research and future strategies for molten chlorides application in concentrated solar power technology

This review summarizes past research and future strategies for the improvement of the pair heat transfer fluids (HTF) - containing material, used in concentrated solar power (CSP) plants, focusing on the most interesting and promising HTF, chloride molten salts. Indeed, their low cost and operating range temperature make them very strong potential candidates for future CSP plants, furthermore improvable by wisely adding nanoparticles. Nevertheless, their well-known aggressive behaviour entails selecting a long-lasting resistant alloy, which requires a better understanding of its associated corrosion mechanisms and the influences of its alloying elements. Mitigation strategy mechanisms that come from salt impurities implying purification processes are also reviewed. Finally, thermogravimetric analysis (TGA) coupled with differential scanning calorimetry (DSC) for salt preparation, and numerical simulations on Thermocalc software modelling elements activities of selected alloys and their interaction with molten chlorides are discusse

Temperature dependence of high-temperature corrosion on nickel-based alloy in molten carbonates for concentrated solar power applications

Concentrated solar power plants present several issues due to salt-induced corrosion, and the modelling of these mechanisms is needed for estimating power plants lifetime predictions. Moreover, a small variation of temperature can lead to microstructure changes due to allotropic transformations and thus free energy of formation of phases within the materials. Therefore, a corrosion study of molten carbonates, being high potential heat transfer fluids for CSP applications, on H230 alloy was performed at 700ºC, 750ºC and 800ºC up to 1000 h, in air atmosphere. The diffusion processes inducing the corrosion mechanism were analyzed and modelled with microstructural characterizations and thermogravimetric studies.Agencia Estatal de InvestigaciónDepto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasTRUEpubAPC financiada por la UC

Temperature effect and alloying elements impact on the corrosion behaviour of the alloys exposed to molten carbonate environments for CSP application

This investigation assesses the effect of the alloy composition and temperature in the corrosivity of the ternary carbonate eutectic, 32% Li2CO3, 33% Na2CO3, 35% K2CO3. To this end, an iron-based alloy, coded as 51Fe-24Cr-20Ni, and a nickel-based alloy, coded as 5Fe–23Cr-58Ni-8Mo, were exposed to the carbonate mixture for 500 h at 700 ºC, 750 ºC and 800 ºC under static atmospheric air. The results revealed that corrosion extension does not have a linear dependence on temperature. There are changes in the corrosion mechanism that depend on the temperature, but, in turn, they are directly influenced by the alloying elements of the material. The performance of the nickel-based substrate proved to be catastrophic at all the studied temperatures. The order from worst to best was 700 ºC > 750 ºC > 800 ºC. The presence of a high molybdenum concentration in the carbonate mixture in contact with this nickel-based alloy suggested that this element dissolution contributes to increasing the corrosivity of the mixture. By contrast, the iron-based alloy showed improved corrosion resistance, with an estimated corrosion rate in the order of hundreds of microns at the three temperatures. The best performance of the 51Fe-24Cr-20Ni alloy was achieved at 700 ºC, followed by that at 800 ºC, while the highest degradation was registered at 750 ºC. This investigation reinforced the idea of the complexity of the corrosion processes in molten carbonate. The equilibrium of corrosive species is very sensitive to an important number of parameters, meaning that modifications in the system conditions have a great impact on corrosivity. Hence, it is critical not to make assumptions when considering potential materials for carbonate containment in CSP technology