Browsing by Issue Date, starting with "2022-08"
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- Effect of marine microbial activity in corrosion inhibition of 5083 aluminium alloy [Comunicação oral]Publication . Marques, Maria João; Mercier, Dimitri; Seyeux, Antoine; Zanna, Sandrine; Marcus, Philippe; Basseguy, RegineABSTRACT: Microbiologically influenced corrosion inhibition (MICI), can be considered as a new environmentally friendly strategy for corrosion inhibition. Nevertheless, at present, most of the findings in MICI research are obtained under optimized laboratory conditions, generally involving a single microorganism. To upgrade the knowledge in this research field and increase the potential applications, more studies under real conditions are needed, since environmental complexity and biological diversity coexist in field environments impacting the corrosion process of metal surfaces. In this context, one of the main objectives of the MICOATEC project (“New concept of Microbially Inspired anticorrosion coating technology”) is to understand the microbially induced formation of a protective layer on the Al-Mg surface during exposure in marine field. The present work is part of this study.
- Hot Corrosion Behavior of Slurry Sprayed Aluminide Coatings in a Simulated Dynamic Molten Carbonate Environment [Comunicação oral]Publication . Audigié, Pauline; Rodríguez Catela, Sergio; Agüero, Alina; Pedrosa, Fátima; Paiva Luís, Teresa; Cunha Diamantino, TeresaABSTRACT: One of the key challenges associated with the use of molten salts in Concentrated Solar Power (CSP) plants is to reduce or even suppress corrosion phenomena occurring at elevated temperatures. Molten nitrate mixtures are currently seen as the most viable storage medium for Thermal Energy Storage. But the upper temperature limit of the currently used “Solar Salt” is restricted by salt decomposition at ~580ºC. Prieto et al. estimated that increasing the temperature to 650ºC could increase the solar-to-electric conversion up to 18.5%, so alternative salts operating at higher temperature are required. Molten carbonates which are less corrosive and allow an operation up to 800ºC are an appealing breakthrough for future CSP plants.
- Microwave versus Conventional Sintering of NiTi Alloys Processed by Mechanical AlloyingPublication . Teixeira, Rodolfo da Silva; Oliveira, R. V.; Rodrigues, Patricia Freitas; Mascarenhas, João; Neves, Filipe; Paula, Andersan dos SantosABSTRACT: The present study shows a comparison between two sintering processes, microwave and conventional sintering, for the manufacture of NiTi porous specimens starting from powder mixtures of nickel and titanium hydrogenation-dehydrogenation (HDH) milled by mechanical alloying for a short time (25 min). The samples were sintered at 850 degrees C for 15 min and 120 min, respectively. Both samples exhibited porosity, and the pore size results are within the range of the human bone. The NiTi intermetallic compound (B2, R-phase, and B19 ') was detected in both sintered samples through X-ray diffraction (XRD) and electron backscattering diffraction (EBSD) on scanning electron microscopic (SEM). Two-step phase transformation occurred in both sintering processes with cooling and heating, the latter occurring with an overlap of the peaks, according to the differential scanning calorimetry (DSC) results. From scanning electron microscopy/electron backscatter diffraction, the R-phase and B2/B19 ' were detected in microwave and conventional sintering, respectively. The instrumented ultramicrohardness results show the highest elastic work values for the conventionally sintered sample. It was observed throughout this investigation that using mechanical alloying (MA) powders enabled, in both sintering processes, good results, such as intermetallic formation and densification in the range for biomedical applications.
- New proton conductive membranes of indazole- and condensed pyrazolebisphosphonic acid-Nafion membranes for PEMFCPublication . Teixeira, Fatima; Teixeira, António P. S.; Rangel, C. M.ABSTRACT: In this work, new doped Nafion membranes for PEMFC are prepared by casting with 1 wt% loading of the prepared indazole- and condensed pyrazolebisphosphonic acids (AzBPs). The new membranes were analysed by ATR-FTIR spectroscopy and their morphology was examined by SEM. Membranes were evaluated for water uptake and ion exchange capacity (IEC), and their hydration number was estimated. The proton conduction properties of the modified membranes were evaluated by electrochemical impedance spectroscopy (EIS), at different temperatures (30, 40, 50 and 60 °C) and relative humidity (RH) (40, 60 and 80%). The proton conductivities of all membranes increase with increasing temperature and RH. Also, all new membranes doped with AzBPs exhibited higher proton conductivities than Nafion N-115, used as a reference and tested at the same experimental conditions, with values up to 1.5-fold. Results show that the incorporation of AzBPs dopants on Nafion membranes enhances the proton conduction throughout the modified membranes. The best proton conductivity was observed for membranes with AzBP1 as dopant, with a value of 94 mS cm-1. These results indicate that the Nafion membranes doped with indazole- and condensed pyrazolebisphosphonic acids are a promising approach for new membranes for PEMFC with improved proton conductivity.
- Microbial action as an inspiring tool to propose innovative corrosion protection processes [Comunicação oral]Publication . Basseguy, Regine; Marques, Maria JoãoABSTRACT: Among the strategies employed to protect metallic materials, coatings can be considered as one of the most successful and cost-effective alternatives to increase the service lifetime of metallic structures, particularly in industries that are continuously exposed to changing and hard weather conditions such as shipbuilding, automobile, aerospace, marine and oil & gas energy infrastructures. However, towards a more constraining legislation as REACH, the surface treatment & coating Industry is at the forefront in developing innovative and even more sustainable products.
- Effective Mild Ethanol-Based Organosolv Pre-Treatment for the Selective Valorization of Polysaccharides and Lignin from Agricultural and Forestry ResiduesPublication . Carvalheiro, Florbela; Duarte, Luís C.; Pires, Filipa; Van-Dúnem, Vanmira; Sanfins, Luís; Roseiro, Luisa B.; Gírio, FranciscoABSTRACT: Organosolv pre-treatments aiming to selectively remove and depolymerise lignin and hemicellulose and yield an easily digestible cellulose fraction are one of the potential options for industrial implementation within the biorefinery concept. However, the use of high temperatures and/or high catalyst concentrations is still hindering its wide adoption. In this work, mild temperature organosolv processes (140 degrees C) that were either non-catalysed or catalysed with sulphuric or acetic acid were compared to standard similar conditions using ethanol-based organosolv for both wheat straw (WS) and eucalyptus wood residues (ERs) as agricultural and forestry-derived model raw materials, respectively. The experimental results demonstrated that high cellulose purities could be obtained for the catalysed ethanol-based processing of the WS, which resulted in high saccharification yields (>80%), conversely to the non-catalysed process, which only reached values close to 70%. For eucalyptus residues (ERs), the pulp yields obtained were lower than the values obtained for the WS, suggesting that the ERs were a more reactive material. Cellulose purity was higher than that obtained for the corresponding treatment for the WS, with the highest cellulose purity being obtained for the ethanol-based process catalysed with sulphuric acid. Both materials presented high lignin yield recovery in the liquid stream.
- Efeito do teletrabalho no impacte ambiental associado ao transporte dos trabalhadores do LNEGPublication . Sousa Rocha, Cristina; Duarte, Ana Paula; Gonçalves, Ana MariaRESUMO: O mundo do trabalho sofreu importantes mudanças nos últimos 3 anos devido à pandemia de COVID 19, tendo-se generalizado o teletrabalho. Considera -se teletrabalho a prestação de trabalho em regime de subordinação jurídica do trabalhador a um empregador, em local não determinado por este, através do recurso a tecnologias de informação e comunicação (Lei 83/2021). De acordo com inquérito realizado pela Eurofound (2020a) em julho de 2020, 34% dos inqui-ridos (cidadãos da União Europeia, UE) trabalhavam exclusivamente a partir de casa, sendo que 46,4 % das mulheres trabalhavam exclusiva ou parcialmente a partir de casa, em com-paração com 43,1 % dos homens. Antes do surto de COVID19, apenas 15% dos empregados na UE já tinham trabalhado remotamente (CE, 2020). Este aumento de teletrabalho gera não só oportunidades, mas também desafios e riscos. Segundo um outro estudo da Eurofound (2020b), as oportunidades oferecidas aos trabalha-dores pelo teletrabalho são a possibilidade de melhorar a conciliação entre vida profissional e vida familiar, maior produtividade e autonomia e redução do tempo necessário para as deslocações pendulares, bem como os custos a elas associados. Pode também incentivar o desenvolvimento de competências em tecnologias de informação, facilitar o acesso ao em-prego e reforçar a inclusividade dos mercados de trabalho para determinadas categorias de trabalhadores (em especial os trabalhadores com deficiência ou com responsabilidades fa-miliares e de prestação de cuidados). Para os empregadores, o teletrabalho tem o potencial de promover a produtividade e a efi-ciência, permitir poupanças nos custos diretos e associados das instalações e dos escritórios e promover uma organização do trabalho virada para os resultados (Messenger et al., 2019). Em termos de riscos para os trabalhadores indica-se o controlo excessivo com a supervisão do uso de equipamento informático a nível empresarial, esbatimento da linha que separa o trabalho da vida privada, níveis mais elevados de intensidade de trabalho, participação vir-tual, isolamento social e profissional, elevada procura de autogestão e auto-organização, falta de atividade física, problemas de ordem psicossocial e musculoesquelética, dificulda-des em assegurar a representação e a negociação coletivas e menor participação dos traba-lhadores nos processos de decisão a nível do local de trabalho (Eurofound, 2020b).