Materiais para a Energia - ME
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Percorrer Materiais para a Energia - ME por Objetivos de Desenvolvimento Sustentável (ODS) "12:Produção e Consumo Sustentáveis"
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- Comparison of the corrosion of ferritic and austenitic stainless steel (AISI 430 and AISI 316L) with LiNaK carbonate salts for thermal energy storage in CSP/CST applicationsPublication . Gil, Mafalda; Pedrosa, Fátima; Paiva Luís, Teresa; Figueira Vasques, Isabel; Oliveira, Fernando; Cunha Diamantino, TeresaABSTRACT: This study focuses on the corrosion rates and mechanisms of two stainless steels, austenitic AISI 316L and ferritic AISI 430, in contact with a eutectic mixture of LiNaK carbonates in long-term tests at 650 degrees C. The selection of these two stainless steels was based on their differences, both in their intrinsic characteristics and in the cost associated with each one. The research also underscores the importance of optimizing the descaling methods used to evaluate the corrosion rate. Corrosion rates were measured gravimetrically according to ISO 17245:2015, revealing an asymptotic behavior for both steels, with AISI 430 with a corrosion rate of 237 f 21 mu m and AISI 316L of 151 f 13 mu m after 2000 h of testing. Corrosion mechanisms were analyzed using SEM/EDS, GDOES, and XRD techniques, which identified well-defined oxide layers with varying compositions. Given the observed corrosion mechanisms and its lower cost, AISI 430 steel seems to have great applicability in CSP/CST plants, provided it is paired with an appropriate protective coating.
- CrFeVWX (X = Ta or Ti) High-Entropy Alloy: A Theoretical and Experimental Comparative Investigation on Phase StabilityPublication . Martins, Ricardo; Valadares, Vasco; Pereira, André; Pereira Gonçalves, Antonio; Neves, Filipe; Sá, Ana; Luz, Paulo P. da; Monteiro, Bernardo; Galatanu, Andrei; Monnier, Judith; Villeroy, Benjamin; Dias, MartaABSTRACT: Materials capable of withstanding extreme environments open promising opportunities for nuclear fusion reactors. In this study, equiatomic CrFeTaVW and CrFeTiVW high-entropy alloys are investigated as interlayer materials between W and CuCrZr. Monte Carlo and Molecular Dynamics simulations predicted a bcc-type structure for both systems. Additionally, the Monte Carlo simulation predicts lower potential energy and a more stable structure for both systems than Molecular Dynamics. For CrFeTaVW, the chemical segregation values are lower in MC than in the MD simulation, whereas for CrFeTiVW, the opposite trend is observed, with MC indicating stronger segregation values. After simulation, the high-entropy alloys were prepared by planetary ball milling, consolidated by spark plasma sintering, and analyzed using X-ray diffraction, scanning electron microscopy, and thermal diffusivity. The experimental results for the milled powders confirmed the formation of a bcc structure in both alloys. The consolidated material revealed a bcc-type structure and an Fe2Ta Laves phase for the CrFeTaVW HEA, while the CrFeTiVW HEA exhibits two different bcc-type structures. The values of CrFeTaVW and CrFeTiVW thermal diffusivity are between 3.5 and 7 mm2/s, which is consistent with the expected values for high-entropy alloys. Overall, the findings indicate that these HEAs have promising properties that can be used in extreme environments.
- (CrVW)(1-x)(TaTi)x, (x=10 and 20 at.%), high entropy alloys as thermal barriers for nuclear fusion reactorsPublication . Martins, Ricardo; Lara, S. de; Neves, Filipe; Sá, Ana; Luz, Paulo P. da; Pereira Gonçalves, Antonio; Galatanu, Andrei; Sobieraj, Damian; Nguyen-Manh, D.; Dias, MartaABSTRACT: Due to the extreme operating temperatures in nuclear fusion reactors, current divertor monoblock materials, tungsten (plasma-facing material) and CuCrZr (heat sink), exhibit a substantial mismatch in mechanical and thermal properties. Therefore, a thermal barrier interlayer is required to guarantee continuous operation. In this work, (CrVW)(1-x)(TaTi)x alloys (x = 10 and 20 at.%) were studied for application as interlayers in nuclear fusion reactors. Atomistic modeling using Monte Carlo simulations combined with a first-principles-based Cluster Expansion Hamiltonian has been performed as a function of temperature to predict the order-disorder transitions in the investigated high-entropy alloys. Moreover, the experimental alloys were prepared by mechanical alloying followed by spark plasma sintering. Both alloy compositions display strong negative average chemical shortrange ordering below 1500 K for the W-Ta and W-Ti chemical pairs, with an estimated transition temperature around 1300 K. Atomic structures obtained from Monte Carlo simulations for (CrWV)80(TaTi)20 indicate that the ordering observed in this composition is stronger than that for (CrWV)90(TaTi)10. Moreover, both systems exhibit a bcc structure, and heat treated samples show phase growth and a four phase microstructure. The thermal diffusivity increases with temperature, reaching lower values than those of pure W and CuCrZr.
- Enhancing Corrosion Resistance of Al-Mg Alloys through Biomineralization [Resumo]Publication . Marques, Maria João; Fori, Benoit; Mercier, Dimitri; Seyeux, Antoine; Zanna, Sandrine; Marcus, Philippe; BASSEGUY, RegineABSTRACT: In recent decades, new emerging microbiological technologies have been studied, based on the recognition that microorganisms can inhibit corrosion by different mechanisms, the so-called MICI (microbiologically influenced corrosion inhibition), opening up different lines of research. In this context, biomineralization has been attracting the attention of researchers, with an increasing number of studies showing that different types of mineralized layers formed on metal surfaces can reduce the risk of corrosion.
- Enhancing modular facade systems with natural materials: Durability and sustainability of wood-based solutions [Poster]Publication . Morgado, Vanessa; Ferreira, Cristina; Vieira, Ana; Alves, Isabel N.; Donato, Mariana; Costa, Luís; Rocha, Jorge; Barreiros, Maria Alexandra; Cunha Diamantino, Teresa
- Enhancing Proton Conductivity of SPEEK Based Membranes by Incorporation Graphene Oxide / Bisphosphonic acid dopant [Resumo]Publication . Teixeira, Fatima; Teixeira, António Paulo Silva; Rangel, Carmen M.ABSTRACT: The most commercially successful membrane for applications in fuel cell and electrolyzers, perfluorinated sulfonic NafionR, exhibits relevant performance limitations due to its dependence on water content with consequent proton mobility restrictions, environmental concerns and very high cost. Poly(etheretherketone) (SPEEK) polymer appears as a versatile non-fluorinated alternative for a low-cost and a more environmentally friendly membrane. Our previous studies showed that the incorporation of biphosphonic acid dopants (BPs) into the mentioned polymeric matrices, improves membrane proton conduction and durability1-5. In this work, we prepared and evaluated new doped SPEEK membranes using graphene oxide (GO) with bisphosphonic acid functionalities as dopant (GOBP), anticipating superior membranes properties, including proton conductivity.
- Evolution of atomically dispersed co-catalysts during solar or UV photocatalysis for efficient and sustained H2 productionPublication . Capelo, Anabela; Fattoruso, Domenico; Valencia-Valero, Laura; Esteves, M. Alexandra; Rangel, Carmen M.; Puga, AlbertoABSTRACT: The evolution of metal/titania photocatalysts during photocatalytic H-2 evolution is herein studied. Samples containing atomically dispersed Pt co-catalysts (single atoms, clusters and sub-nanoparticles) formed after calcination were compared to pre-reduced analogues mostly having metallic nanoparticles (diameters >1 nm) during ethanol photoreforming under either UV-rich irradiation or natural sunlight. Aggregation of ultra-dispersed oxidised platinum entities (Pt delta+) with concomitant reduction into Pt-0 nanoparticles (1-2 nm) was observed after UV irradiation by transmission electron microscopy (TEM), and diffuse reflectance UV-visible (DRUV-vis) and X-ray photoelectron (XPS) spectroscopies. A parallel, albeit slower, evolution trend was evidenced during solar photocatalysis. Conversely, atomically dispersed Cu co-catalyst species did not grow and became in-situ reduced into sub-nanometric Cu-0 under irradiation. Hydrogen production rates were remarkably high during initial stages of UV irradiation, and then declined to a sustained regime (approximate to 50 and 8 mmol g(-1) h(-1) for Pt/TiO2 or Cu/TiO2, respectively, for up to 24 h of irradiation). Steadier solar photoreforming was observed in experiments performed in a compound parabolic collector tubular reactor (approximate to 7.6 and 1.7 mmol g(-1) h(-1) for Pt/TiO2 or Cu/TiO2, respectively). Despite the non-negligible effect of co-catalyst rearrangement on activity rationalised herein, attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy measurements pre- and post-photocatalysis suggest that accumulation of strongly adsorbed degradation intermediates, chiefly acetate, is a major cause for rate decreases. Notwithstanding, this phenomenon did not result in total deactivation, so that sustained hydrogen production upon long-term irradiation was not compromised.
- Exploring Marine Biomineralization on the Al-Mg Alloy as a Natural Process for In Situ LDH Growth to Improve Corrosion ResistancePublication . Marques, Maria João; Mercier, Dimitri; Seyeux, Antoine; Zanna, Sandrine; Tenailleau, Christophe; Duployer, Benjamin; Jeannin, Marc; Marcus, Philippe; Basséguy; BASSEGUY, RegineABSTRACT: This study provides a detailed characterization of the AA5083 aluminum alloy, surface, and interface over 6 months of immersion in seawater, employing techniques such as SEM/EDX, GIXRD, mu-Raman and XPS. The purpose was to evaluate the evolution of the biomineralization process that occurs on the Al-Mg alloy. By investigating the specific conditions that favor the in situ growth of layered double hydroxide (LDH) during seawater immersion as a result of biomineralization, this research provides insights into marine biomineralization, highlighting its potential as an innovative and sustainable strategy for corrosion protection.
- Functional alginate aerogels as green catalytic platform for CO₂-to-syngas conversion [Resumo]Publication . Messias, Sofia; Paninho, A. B.; Vieira, G.; Souza, A.; Rangel, Carmen M.; Nunes, Daniela; Martins, Rodrigo; Mendes, Manuel Joao; Machado, Ana
- Green Catalytic Transformation of CO₂ to Syngas Using Aerogels [Resumo]Publication . Paninho, A. B.; Messias, Sofia; Fernandes, I.; Rangel, Carmen M.; Nunes, A. V. M.; Branco, Luis; Martins, Rodrigo; Mendes, Manuel Joao; Machado, Ana
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