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Repositório Científico do Laboratório Nacional de Energia e Geologia
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(CrVW)(1-x)(TaTi)x, (x=10 and 20 at.%), high entropy alloys as thermal barriers for nuclear fusion reactors
Publication . Martins, Ricardo; Lara, S. de; Neves, Filipe; Sá, Ana; Luz, Paulo P. da; Pereira Gonçalves, Antonio; Galatanu, Andrei; Sobieraj, Damian; Nguyen-Manh, D.; Dias, Marta
ABSTRACT: 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.
Acid-Based Deep Eutectic Solvents for Structural Modification of Sulphite Pulp Cellulose: A Potential Route Toward Advanced Materials
Publication . Moran, Guadalupe; Costa Trigo, Iván; Domínguez, José Manuel; Vilaseca, Fabiola
ABSTRACT: The transition toward renewable and environmentally responsible materials has intensified interest in cellulose-based systems for use in sustainable packaging applications. Although cellulose offers biocompatibility, structural versatility, and tuneable physicochemical properties, conventional modification routes rely on harsh chemicals and generate environmentally burdensome effluents. In this study, an efficient and a potentially green strategy for cellulose modification was developed using acid-based deep eutectic solvents (DES) composed of choline chloride and lactic, acetic, or citric acid at different molar ratios. Under mild conditions (110 degrees C, 4 h), DES pretreatment reduced glucan content in sulphite pulp from 99% to 79-93%, depending on the hydrogen bond donor (HBD), while suggesting an apparent increase in relative crystallinity, from approximately 82% to 90%, as estimated by the Segal method. FTIR, XRD, and morphological analyses revealed the disruption of the hydrogen bonding network, enhanced fibrillation, and residual DES-derived functional groups detectable by FTIR. Although DES pretreatment increased structural order, it also reduced enzymatic digestibility due to the higher proportion of crystalline domains. Overall, the results demonstrate that acidic DES constitutes a sustainable and recyclable medium capable of modulating cellulose structure and generating materials with enhanced physicochemical properties. These findings suggest that DES-modified cellulose could serve as a potential reinforcement platform for future biodegradable packaging and bioplastic formulations, enabling the development of high-performance, renewable, and environmentally compliant packaging materials.
Cyclopentadienyl vs indenyl control of thermal/photoactivated CO release in cationic molybdenum(II) dicarbonyl-ethylenediamine complexes
Publication . Bruno, Sofia M.; Calhau, Isabel B.; Dias, Tiago M.; Santos, Adriana; Silva, Luis Cunha; Nolasco, Mariela M.; Goncalves, Isabel S.; Pillinger, Martyn
ABSTRACT: Molybdenum half-sandwich carbonyl complexes continue to attract attention as potential anticancer agents and prodrugs for therapeutic use of carbon monoxide. Building on the known bioactivity and hydrolytic stability of cyclopentadienyl-based Mo fragments, we report the synthesis, structural characterization, and solution behavior of two cationic half-sandwich complexes, [(eta 5-Cp)Mo(CO)2(en)][BF4] (3) and [(eta 5-Ind)Mo(CO)2(en)][BF4] (4) (Cp = cyclopentadienyl, Ind = indenyl, en = ethylenediamine). Complex 3 is described here for the first time, while 4 was structurally characterized by single-crystal X-ray diffraction, revealing a distorted square-pyramidal geometry with cis-CO ligands and a chelating en ligand positioned beneath the indenyl ring. Both compounds are air-stable in the solid state and exhibit enhanced solubility in polar media due to their ionic nature. UV-vis stability studies under simulated physiological conditions (PBS, pH 7.4, 37 degrees C) show gradual decomposition of both complexes, accelerated by visible-light irradiation and/or the presence of air. CO-release behavior was quantified using the myoglobin assay: the allyl precursors [(eta 5-Cp')Mo(eta 3-C3H5)(CO)2] were inert, whereas complexes 3 and 4 released CO slowly, with 4 exhibiting significantly faster thermal CO liberation (t1/2 approximate to 129 min; 0.74 equiv. CO after 6 h). Complex 3 showed minimal thermal CO release but underwent enhanced and sustained photodecarbonylation under visible-light irradiation, enabling controlled CO delivery. These results identify 3 and 4 as rare examples of Mo-based CO-releasing molecules capable of slow, tunable CO release under biologically relevant conditions, with 3 displaying light-responsive behavior and 4 functioning as a spontaneous thermal CO donor.
A two-stage cultivation strategy for the industrial production of the novel microalga Chlorococcum amblystomatis
Publication . Correia, Nádia; Trovão, Mafalda; Santo, Gonçalo E.; Guerra, Inês; Cunha, P.; Fonseca, Joana; Pereira, Hugo; Costa, Monya M.; Ferreira, Sara; Santos, Tamára; Barros, Ana; Cardoso, Helena; Silva, Joana; Gouveia, Luisa; Varela, João
ABSTRACT: This study presented the industrial-scale validation of a two-stage growth strategy for a poorly explored yet industrially relevant chlorophyte microalga, Chlorococcum amblystomatis, addressing the gap between laboratory research and practical application. By using cultures grown heterotrophically as inoculum for industrial-scale photoautotrophic reactors, this approach significantly accelerated scale-up. The proposed strategy reduced the overall scale-up time by approximately 5.5-fold compared to the conventional pipeline, without compromising productivity or biochemical quality. A maximum biomass concentration of 70.96 +/- 0.35 g L-1 was achieved in 7-L benchtop fermenters under heterotrophic conditions, representing the highest value reported to date for this microalga. The biomass obtained presented a protein content of 32.42 +/- 2.30% of dry weight, which increased to 54.55 +/- 2.04% upon cultivation under photoautotrophic conditions, as well as polyunsaturated fatty acids, which increased from 50.12 +/- 3.27 to 67.74 +/- 0.35% of total fatty acids, with alpha-linolenic acid as the predominant fatty acid. Conversely, the saturated fatty acids content (38.26 +/- 1.63% of TFA) decreased to 22.37 +/- 0.02% of TFA in the phototrophic stage. Pigment contents also increased significantly during the phototrophic stage, with chlorophylls rising from 10.04 +/- 1.68 to 44.91 +/- 5.11 mg g(-)1 and carotenoids reaching notable concentrations, including lutein (5.34 +/- 0.10 mg g-1), beta-carotene (5.92 +/- 0.39 mg g-1), and neoxanthin (3.53 +/- 0.75 mg g-1). Among the industrial photoautotrophic systems tested, the closed tubular photobioreactors were the most suitable configuration for C. amblystomatis cultivation, achieving higher biomass productivity, enhanced protein content and pigment accumulation compared to open raceway ponds. Overall, this work demonstrates a scalable, efficient, and time-saving cultivation strategy for C. amblystomatis, supporting its potential for industrial biotechnological applications.
Dados geocientíficos: acesso e quantificação do conhecimento geológico e energético [Comunicação oral]
Publication . Quental, Lídia; Patinha, Pedro; Pereira, Aurete; Candeias, Ana Paula; Duarte, Salete; Luís, Gabriel