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- Exploring the potential of cuttlebone waste to produce building limePublication . Ferraz, Eduardo; Gamelas, J. A.F.; Coroado, João; Monteiro, C.; Rocha, F.The goal of this study is to find a practicable way to recycle cuttlebone waste in the production of lime. It was studied the behavior of calcium oxide obtained from the calcination of this waste at 900, 1000 and 1100 ºC and, after wet slaking, the produced lime was characterized. All the results were compared to calcium oxide or to hydrated lime obtained from commercial limestone. According to the slaking results, the waste and the limestone calcined at 1000 ºC achieved the R4 (around 13 min to reach 60 ºC) and R5 (60 ºC in 25 s) reactivity class, respectively. Changing the calcination temperature to 900 or 1100 ºC did not promote an increase in the reactivity of the calcined waste. Although less reactive than the calcined limestone, the calcined cuttlebone can be transformed without significant constraint into building lime, since this construction material fulfills the relevant physic-chemical standard specifications.
- Projeto TURARQ - Turismo Arqueológico para Territórios de Baixa Densidade do Médio TejoPublication . Ferraz, Eduardo; Trindade, Anícia; Cardoso, Douglas O.; Gomes, Hugo Filipe Teixeira; Martins, Marco; Garcês, Sara; Nunes, Sérgio Leal; Figueira, Luís Mota; Delfino, Regina; Rey, Joana; Anastácio, Rita Ferreira; Pereira, Anabela Borralheiro; Oosterbeek, LuizApresentação do projeto TurArq, que tem como objetivo principal promover o turismo científico e cultural em territórios de baixa densidade do Médio Tejo português (municípios de Abrantes, Constância, Mação, Tomar e Vila Nova da Barquinha), gerando riqueza e novos empregos, apostando no usufruto presencial do património arqueológico e nos meios de divulgação digital. O projeto pretende contribuir para uma gestão patrimonial integrada na região, a fixação de capital humano, a mobilização de recursos dedicados à sua capacitação e a valorização do património existente. Visa ainda promover o desenvolvimento comunitário, a coesão do território e a sua preservação, numa lógica de sustentabilidade.
- Improving Colloidal Stability of Sepiolite Suspensions: Effect of the Mechanical Disperser and Chemical DispersantPublication . Alves, Luís; Ferraz, Eduardo; Santarén, Julio; Rasteiro, Maria G.; Gamelas, José A. F.To allow the use of fibrous-like clays, as sepiolite, in different applications, their disaggregation and the formation of stable suspensions are crucial steps to enhance their performance significantly, e.g., in cellulose nanofibrils/clay composite formulations, enabling an adequate mixture of the matrix and filler individual components. Three distinct physical treatments of dispersion (magnetic stirring, high-speed shearing, and ultrasonication) and four different chemical dispersants (polyacrylate, polyphosphate, carboxymethylcellulose, and alginate, all in the form of sodium salts) were tested to improve the dispersibility and the formation of stable suspensions of sepiolite. Two sepiolite samples from the same origin but with different pre-treatments were evaluated. The particle size and suspension stability were evaluated by dynamic light scattering, zeta potential measurements and optical microscopy. Additionally, the sepiolite samples were initially characterized for their mineralogical, chemical, and morphologic properties. Of the three physical dispersion treatments tested, the ultrasonicator typically produced more stable suspensions; on the other hand, the biopolymer carboxymethylcellulose showed a higher ability to produce stable suspensions, being, however, a smaller particle size obtained when polyphosphate was used. Remarkably, 47 out of 90 prepared suspensions of sepiolite stayed homogeneous for at least three months after their preparation. In sum, the combination of a high energy dispersing equipment with an appropriate dispersing agent led to stable suspensions with optimal properties to be used in different applications, like in the composite production.
- Composite Films of Nanofibrillated Cellulose with Sepiolite: Effect of Preparation StrategyPublication . Alves, Luis; Ramos, Ana; Rasteiro, Maria G.; Vitorino, Carla; Ferraz, Eduardo; Ferreira, Paulo J. T.; Puertas, Maria L.; Gamelas, José A. F.Cellulose nanofibrils (CNFs) are nanomaterials with promising properties to be used in food packaging and printed electronics, thus being logical substitutes to petroleum-based polymers, specifically plastics. CNFs can be combined with other materials, such as clay minerals, to form composites, which are environmentally friendly materials, with acceptable costs and without compromising the final properties of the composite material. To produce composite films, two strategies can be used: solvent casting and filtration followed by hot pressing. The first approach is the simplest way to produce films, but the obtained films may present some limitations. In the present work, CNFs produced using enzymatic or TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) oxidation pretreatments, followed by high-pressure homogenization, or only by mechanical treatment (homogenization), were used to produce films by both the available procedures. The films obtained by filtration + hot pressing presented higher tensile strength and Young’s modulus compared with those obtained by solvent casting. In general, a decrease in the values of these mechanical properties of the films and a decrease in elongation at break, with the addition of sepiolite, were also observed. However, for the TEMPO CNF-based films, an improvement in tensile strength could be observed for 10% of the sepiolite content. Furthermore, the time necessary to produce films was largely reduced by employing the filtration procedure. Finally, the water vapour barrier properties of the films obtained by filtration are comparable to the literature values of net CNF films. Thus, this technique demonstrates to be the most suitable to produce CNF-based composite films in a fast way and with improved mechanical properties and suitable gas barrier properties.
- Tuning rheology and aggregation behaviour of TEMPO-oxidised cellulose nanofibrils aqueous suspensions by addition of different acidsPublication . Alves, L.; Ferraz, Eduardo; Lourenço, A. F.; Ferreira, P. J.; Rasteiro, M. G.; Gamelas, J. A. F.The present work intends to study the variations in the rheological properties and aggregation behaviour of TEMPO-oxidised cellulose nanofibrils (CNF) aqueous suspensions, as a function of changes in concentration and systematic changes in the pH, by addition of acids with different anions. It was found that CNF suspensions form strong gels at mass fractions higher than 0.35 % and the gel point is ca. 0.18 %. On the other hand, aggregation is enhanced at acidic pH conditions due to lower charge repulsion among fibrils, leading to an increase of the suspension viscosity. However, distinct rheological behaviours were presented by CNF suspensions as different acids were applied. It was found that phosphate ions resulted in significant aggregation leading to formation of particles of large size and very strong gels, at pH 2.3; distinctly, the presence of acetate ions resulted in lower aggregation, lower particle size and weaker gels, at the same pH value.
- Comparison of mineralogical, mechanical and hygroscopic characteristic of earthen, gypsum and cement-based plastersPublication . Santos, Tânia; Gomes, Maria Idália; Silva, António Santos; Ferraz, Eduardo; Faria, PaulinaIt is important to ensure indoor comfort by passive methods, avoiding mechanical equipment that has energy costs. To assess plasters common efficiency but also its contribution as moisture buffers, five different plastering mortars, including unstabilized and stabilized earth-based plasters, gypsum and cement-based pre-mixed plasters, were analyzed and their chemical, mechanical and hygroscopic characteristics compared. The materials and mortars were analyzed by X-ray diffraction and simultaneous thermal analysis. Linear shrinkage, dry bulk density, dynamic modulus of elasticity, flexural and compressive strengths, dry abrasion resistance, surface cohesion, surface hardness and sorption and desorption of mortars and plasters were also evaluated. The mechanical strength of earthen mortars is lower than gypsum and cement-based mortars. However, earth plasters show the highest hygroscopicity, acting as moisture passive buffers, improving thermal comfort and contributing to occupantś health.
- Design of cellulose nanofibre-based composites with high barrier propertiesPublication . Alves, Luís; Ramos, Ana; Ferraz, Eduardo; J. T. Ferreira, Paulo; G. Rasteiro, Maria; A. F. Gamelas, JoséGas barrier properties are very relevant in composite materials for applications so diverse such as food packaging, electronics, or old document restoration. In the present work, four different types of cellulose nanofibres (CNFs), two types of clay minerals used individually (sepiolite) or combined (sepiolite + kaolinite), and the influence of pH, were explored in the production of composite films. Neat CNFs, only mechanically treated or prepared by enzymatic pre-treatment, gave films with good mechanical and barrier properties, but the addition of minerals led to a dramatic loss of these properties. Contrarily, the use of thin and functionalized fibrils (TEMPO-oxidised or cationized CNFs) gave composite films with good mechanical, thermal and barrier properties. Superior oxygen barrier properties (oxygen transmission rate (OTR) < 0.4 cm3 m−2 day−1) were obtained using TEMPO-oxidised CNF and 20% sepiolite, and, in general, for all the composite films containing the TEMPO CNF (OTR ≤ 1.8 cm3 m−2 day−1). The cationic CNF-based composites also showed a very good oxygen barrier (OTR ≤ 8.2 cm3 m−2 day−1). The high oxygen barrier could be explained by the compactness of the films and better entanglement of the more fibrillated nanocelluloses with the mineral particles. A decrease in the pH of the suspensions led to a decrease in the film preparation time, without a major negative impact on the composite film’s properties.
- Effect of the dispersion state of minerals on the properties of cellulose nanofiber-based composite filmsPublication . Alves, Luís; Ramos, Ana; Ferraz, Eduardo; Sanguino, Pedro; Santaren, Julio; Rasteiro, Maria Graça; Gamelas, José AFThe dispersion state and the efficiency of the mixture of the different components in a composite film have an important impact on its mechanical and optical properties. In the present work, the impacts of different dispersion treatments on the disaggregation state of fibrous clay particles in water, and on the properties of related cellulose nanofiber (CNF)-based composite films, were evaluated. X-ray diffraction studies, performed on samples of sepiolite and palygorskite, revealed only minor changes in the diffraction pattern when the minerals were subjected to ultrasonic treatment, with or without the addition of different chemical dispersing agents. Conversely, microscopic studies revealed important differences in the dispersion state of the samples, induced by the addition of the different dispersants, showing an improvement in the disaggregation of the mineral crystals. The composite films prepared with sepiolite (and carboxymethylcellulose, as chemical dispersant) dispersed using ultrasonic treatment, and different types of CNF, showed improved optical and mechanical properties when compared with composites of the same counterparts prepared with sepiolite dispersed using a high-speed shear disperser.
- Stabilization of Palygorskite Aqueous Suspensions Using Bio-Based and Synthetic PolyelectrolytesPublication . Ferraz, Eduardo; Alves, Luís; Sanguino, Pedro; Santarén, Julio; Rasteiro, Maria G.; Gamelas, José A. F.Palygorskite is a natural fibrous clay mineral that can be used in several applications, for which colloidal stability in aqueous suspensions is a key point to improve its performance. In this study, methods of magnetic stirring, high-speed shearing, and ultrasonication, as well as different chemical dispersants, combined with these methods, namely carboxymethylcellulose, alginate, polyphosphate, and polyacrylate, were used to improve the dispersibility and the formation of stable suspensions of palygorskite in different conditions of pH. The stability and particle size of suspensions with a low concentration of palygorskite were evaluated by visual inspection, optical and electron microscopy, dynamic light scattering, and zeta potential measurements. Moreover, the palygorskite used in this work was initially characterized for its mineralogical, chemical, physical, and morphological properties. It was found that more stable suspensions were produced with ultrasonication compared to the other two physical treatments, with magnetic stirring being inefficient in all tested cases, and for higher pH values (pH of 12 and pH of 8, the natural pH of the clay) when compared to lower pH values (pH of 3). Remarkably, combined with ultrasonication, carboxymethylcellulose or in a lesser extent polyphosphate at near neutral pH allowed for the disaggregation of crystal bundles of palygorskite into individualized crystals. These results may be helpful to optimize the performance of palygorskite in several domains where it is applied.
- Filmes de celulose nanofibrilada com incorporação de minerais: uma nova geração de materiais para embalagens alimentares e eletrónica impressaPublication . Alves, Luís; Aragão, António; Ferraz, Eduardo; Santarén, Júlio; Ferreira, Paulo J. T.; Ramos, Ana; Rasteiro, Maria G.; Gamelas, José A. F.