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Browsing ENERGIA by Field of Science and Technology (FOS) "Ciências Naturais::Ciências Físicas"
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- Advancing Sustainable Production of High-Performance Cellulose PulpsPublication . Moran, Guadalupe; Costa Trigo, Iván; Bastida, Gabriela Adriana; Mazega, André; Duran, Josep; Domínguez, José Manuel; Vilaseca, FabiolaABSTRACT: Highlights What are the main findings? Enzymatic hydrolysis pretreatment of industrial pulps Pulp composition influencing the enzymatic performance Enhanced conditions for high-performance cellulose pulps What is the implication of the main finding? Sustainable methodology to produce cellulose pulps Lower environmental impact and alignment with circular economic principles Improvements in tensile strength, air permeability, hydrophobicity, and internal bondingHighlights What are the main findings? Enzymatic hydrolysis pretreatment of industrial pulps Pulp composition influencing the enzymatic performance Enhanced conditions for high-performance cellulose pulps What is the implication of the main finding? Sustainable methodology to produce cellulose pulps Lower environmental impact and alignment with circular economic principles Improvements in tensile strength, air permeability, hydrophobicity, and internal bondingAbstract With a growing demand for renewable resources in high-performance materials, sustainable methods are preferred for their lower environmental impact and alignment with circular economy principles. Among these, enzymatic hydrolysis remains relatively underexplored yet shows strong potential for cellulose fibrillation, offering a promising route that may lower energy requirements by minimizing the need for extensive refining compared to conventional mechanical or chemical approaches. In this study, enzyme cocktails rich in cellulase and xylanase were applied to three industrial pulps, sulphite, bleached Kraft eucalyptus and thermomechanical pine, to produce high-performance cellulose pulps. Treatments were carried out using varying enzyme loads (5-40 filter paper units per gram of dry pulp, FPU/gdp) and reaction times (1-16 h). The resulting chemical composition, structural morphology, and physical-mechanical properties were systematically evaluated. The findings revealed that pulp composition strongly influenced enzymatic treatment, affecting surface fibrillation, fibre aggregation, swelling, and fibre shortening. Under optimized conditions, enzymatic pretreatment significantly enhanced paper performance, with improvements in tensile strength, air permeability, hydrophobicity, and internal bonding. Overall, enzymatic hydrolysis represents a sustainable solution and a strategy which could reduce energy expenditures to high-performance cellulose pulps, suitable as reinforcing fibres in packaging applications.
- Layers PorosityPublication . Lima, Margarida
- Megafloat inicial state of ArtPublication . Lima, Margarida
- Small ANSYS ReportPublication . Lima, Margarida
- Thermal Stability and Irradiation Resistance of (CrFeTiTa)70W30 and VFeTiTaW High Entropy AlloysPublication . Pereira, André; Martins, Ricardo; Monteiro, Bernardo; Correia, Jose B.; Galatanu, Andrei; Catarino, Norberto; Jenus, Petra; Dias, MartaABSTRACT: Nuclear fusion is a promising energy source. The International Thermonuclear Experimental Reactor aims to study the feasibility of tokamak-type reactors and test technologies and materials for commercial use. One major challenge is developing materials for the reactor's divertor, which supports high thermal flux. Tungsten was chosen as the plasma-facing material, while a CuCrZr alloy will be used in the cooling pipes. However, the gradient between the working temperatures of these materials requires the use of a thermal barrier interlayer between them. To this end, refractory high-entropy (CrFeTiTa)70W30 and VFeTiTaW alloys were prepared by mechanical alloying and sintering, and their thermal and irradiation resistance was evaluated. Both alloys showed phase growth after annealing at 1100 degrees C for 8 days, being more pronounced for higher temperatures (1300 degrees C and 1500 degrees C). The VFeTiTaW alloy presented greater phase growth, suggesting lower microstructural stability, however, no new phases were formed. Both (as-sintered) alloys were irradiated with Ar+ (150 keV) with a fluence of 2.4 x 1020 at/m2, as well as He+ (10 keV) and D+ (5 keV) both with a fluence of 5 x 1021 at/m2. The morphology of the surface of both samples was analyzed before and after irradiation showing no severe morphologic changes, indicating high irradiation resistance. Additionally, the VFeTiTaW alloy presented a lower deuterium retention (8.58%) when compared to (CrFeTiTa)70W30 alloy (14.41%).