Papers by Fernando Castro
WASTES 2015 – Solutions, Treatments and Opportunities: Selected papers from the 3rd Edition of th... more WASTES 2015 – Solutions, Treatments and Opportunities: Selected papers from the 3rd Edition of the International Conference on Wastes: Solutions, Treatments and Opportunities, Viana Do Castelo, Portugal,14-16 September 2015
International Journal of Materials Research, 1998
In the Cu–Zr system, especially between 0.25 < x (Zr) < 1, experimental liquidus points are... more In the Cu–Zr system, especially between 0.25 < x (Zr) < 1, experimental liquidus points are missing and many doubts arise concerning the invariant points. In 1986, Kneller et al. [1] pointed out the existence of three phases and two eutectoid reactions which had not yet been reported. This work has been questioned by other authors [2,3]. Differential Thermal Analysis (DTA) experiments have been done in almost the whole range of compositions of the Cu–Zr system, especially where the work of Kneller et al. [1] is ambiguous; results are compared with the previous ones.
Journal de Chimie Physique, 1997
La partie riche en aluminium du systeme Al-Cu-Zr a ete etudiee par analyse thermique differentiel... more La partie riche en aluminium du systeme Al-Cu-Zr a ete etudiee par analyse thermique differentielle et par microscopie. Les alliages contenant jusqu'a 14 at.% Zr et 25 at.% Cu ont presente des phases en bon accord avec celles mentionnees dans la litterature, a l'exception d'une nouvelle phase qui a ete mise en evidence a la place de la phase τ9 citee dans la litterature mais jamais trouvee durant cette etude. Les temperatures des transformations de phases ont ete determinees par ATD. Les phases en equilibre dans les alliages ont ete identifiees sur des echantillons qui ont subi des traitements d'homogeneisation a des temperatures superieures et inferieures aux temperatures de transformation. Les auteurs proposent un schema reactionnel plausible pour cette partie du systeme ternaire.
Adequate physical and mechanical properties, for numerous steel grades, can be obtained only with... more Adequate physical and mechanical properties, for numerous steel grades, can be obtained only with a precise control of the composition, morphology and plasticity of oxide and sulphide inclusions that remain in the product. In liquid metal, the composition of complex inclusions can be monitored by appropriate deoxidation practice, calcium treatment and/or slag-metal reaction. Further transformation may occur during solidification or heat treatments prior to hotrolling: reaction between oxides and sulphides, as well as recrystallisation of oxides. An analysis of these factors and of tools (thermodynamic models and laboratory experiments) which have been developed to comprehend and control them is presented
The effect of zirconium addition on the eutectic reactions, on the Al-rich part of the Al-Cu and ... more The effect of zirconium addition on the eutectic reactions, on the Al-rich part of the Al-Cu and Al-Cu-Mg systems, were studied by differential thermal analysis (DTA). The temperature of the reactions and, for AI-Cu alloys, the heat of the reactions were determined. After the DTA experiments the alloys were studied by scanning electron microscopy (SEM) and the chemical analysis of the phases have been determined by energydispersive spectroscopy (EDS). The temperature of the eutectic reactions does not change significantly by the presence of zirconium in the system. The phase distribution on the ternary and quaternary systems shows that the zirconium present is essentially in the A13Zr and "32' phases. The N3Zr phase has a low solubility range for copper,-0.5 at.%, and no solubility for magnesium. The X-ray pattern of the ternary phase "32' is presented, for alloys belonging to the Al-rich part of the Al-Cu-Zr system
Developments in Mineral Processing, 2000
The zinc content of Blast Furnace (BF) and Basic Oxygen Furnace (BOF) dusts and sludges is relati... more The zinc content of Blast Furnace (BF) and Basic Oxygen Furnace (BOF) dusts and sludges is relatively high, however is generally not economically to treat these residues to recover zinc. Taking into account that they have a high iron content, removal of zinc would allow economical recovery of the iron values. On the other hand, due the increasing rate of
Waste and Biomass Valorization, 2012
ABSTRACT Many European countries are developing the use of pellets or wood briquettes for the sup... more ABSTRACT Many European countries are developing the use of pellets or wood briquettes for the supplying of local energy. Many industries are being forced to replace fossil fuels with biomass because of its neutrality in relation to CO2 emissions, thus creating an interesting market for pellets. In Portugal, the most common undergrowth includes: esteva (Cistus ladanifer), tojo (Ulex europaeus), giesta (Sarothamus scoparius), feto (Pteridium aquilium) and silva (Rubus ulmifolius). These undergrowth specimen are attractive due to the large volume available, but are not usually used for making pellets. It is possible to prevent large fires cleaning the forests, but this is an expensive task that could be compensated if the undergrowth can have some commercial value. The use of the common undergrowth for the manufacture of pellets and briquettes will allow the undergrowth to be considered not as a problem to be removed from the forest but an opportunity as renewable energy. The aim of this work is to obtain pellets with standard properties and evaluate the parameters that can qualify the performance of these pellets: moisture content, particle size distribution, high heating value, height of flame and burning time, pressure and temperature of the pelletizing process and mechanical durability. The pelletizing process was first simulated on laboratorial scale using small amounts of each vegetal specimen which was pressed in a heated mould. Some samples were submitted to a torrefaction treatment. After the laboratorial screening, the selected material was processed using a pellet mill to prepare pellets with 6 mm of diameter. The durability test was performed using a tumbling device following the ASAE S 269.4 standard. Burning tests of pellets with the same weight were performed and video images analysed, where height of flame and ignition time were measured. It was found that undergrowth pellets had good power of agglomeration and allow an easy ignition. The apparent density varies around 1,260 kg/m3. The moisture content of different pellet varied between 2.79 and 7.46 %, ash content was less than 3 %, the calorific value is between 16 and 18 kJ/kg, the durability results respect the values recommended by standards. After ignition the flame increases to an average height of 25 mm. The total burning time was in all cases dominated by the cinder combustion without visible flame and the total complete burning time varied between 400 and 600 s. The results showed that it is possible to produce pellets of undergrowth with physical and thermochemical characteristics similar to the existing in the market at the present time.
Os resíduos são considerados uma fonte atrativa para a produção de energia, principalmente os de ... more Os resíduos são considerados uma fonte atrativa para a produção de energia, principalmente os de base polimérica. Várias são as técnicas de valorização térmica e energética, como a pirólise, que constituem alternativas com elevado potencial no que concerne à produção de combustíveis alternativos e energia. Estas técnicas, quando aplicadas a resíduos, favorecem a formação de produtos com valor acrescentado. A utilização de resíduos como matéria-prima é uma das mais-valias associadas ao processo, constituindo uma alternativa à sua eliminação em aterro sanitário através do reaproveitamento dos mesmos em processos energéticos.
The feasibility of using a zinc oxide rich waste (ZnO>95%), dust originated in the brass smelt... more The feasibility of using a zinc oxide rich waste (ZnO>95%), dust originated in the brass smelting industrial process, as a raw material to produce targets to be used in radiofrequency magnetron sputtering (RFMS) deposition of ZnO thin films was investigated. The ZnO waste was characterized in terms of chemical and mineralogical compositions and particle size distribution. The targets were prepared by uniaxial pressing of the ZnO waste followed by sintering in air at a temperature in the range 900-1200 oC. The density of sintered targets increased with sintering temperature, and zincite (ZnO) was the predominant crystalline phase identified by X-ray diffraction (XRD). Scanning electron microscopy (SEM) revealed zincite grains, with an average size ~2 m and a nonhomogeneous microstructure due to the presence of dense aggregates. Preliminary MS thin film deposition tests on a glass substrate produced transparent nanostructured ZnO thin films with a homogeneous microstructure. Resea...
As ligas tradicionais para solda, à base de Sn-Pb, estão a ser substituídas devido ao impacto, ca... more As ligas tradicionais para solda, à base de Sn-Pb, estão a ser substituídas devido ao impacto, causado pela toxicidade do chumbo, no ambiente e na saúde humana. Entre os sistemas alternativos de ligas sem chumbo, as ligas à base de Sn-Zn e Sn-Cu apresentam propriedades promissoras. As características da ligação produzida dependem do tipo de reacções que ocorrem entre a solda e o substrato, durante a operação de soldadura. As reacções solda/substrato foram estudadas neste trabalho, para diferentes ligas dos sistemas Sn-Zn e Sn-Cu, relativamente à morfologia e composição química da interface. Foram caracterizadas as fases formadas entre a solda no estado líquido e o substrato de cobre, à temperatura de 250 ºC, para diferentes composições químicas da solda e tempos de estágio. As temperaturas de transformação das ligas ensaiadas foram determinadas por Calorimetria Diferencial de Varrimento (DSC). A caracterização morfológica da interface criada foi efectuada por Microscopia Electrónica de Varrimento e a análise química por Espectroscopia de Dispersão de Energias (SEM/EDS). Os resultados obtidos, para as ligas sem chumbo, foram comparados com os obtidos para a solda tradicional, à base de Sn-Pb. Foram obtidos diferentes tipos de morfologia de interface, nomeadamente, para os sistemas contendo zinco.
Este trabalho visa dar a conhecer o contexto de achado e a composicao quimica de uma ponta de lan... more Este trabalho visa dar a conhecer o contexto de achado e a composicao quimica de uma ponta de lanca de alvado curto e de folha ligeiramente losângica com nervura central, inserivel no Bronze Final e inedita. Esta foi encontrada na serra do Muro, freguesia de Baltar, concelho de Paredes, distrito do Porto. A serra do Muro corresponde a um monte com uma implantacao orografica dominante na regiao sobre os vales dos rios Ferreira e Sousa, este afiuente da margem norte da bacia do Douro, em area rica em recursos primarios e secundarios de estanho. No topo deste acidente geomorfologico foi edificado um povoado proto-historico que figura na literatura arqueologica especialmente pelo grande perimetro e espessura das suas muralhas petreas. Apesar da proximidade destes dois contextos arqueologicos nao ha qualquer indicacao precisa de que estejam vinculados, podendo esta peca constituir um deposito. Nao sendo muito frequente o achado de pontas de lanca no NO portugues, conhecem-se todavia algu...
Sustainability, 2021
The sustainability of resources is becoming a worldwide concern, including construction and build... more The sustainability of resources is becoming a worldwide concern, including construction and building materials, especially with the alarming increase rate in global population. Alternative solutions to ordinary Portland cement (OPC) as a concrete binder are being studied, namely the so-called alkali-activated cements (AAC). These are less harmful to the environment, as lower CO2 emissions are associated with their fabrication, and their mechanical properties can be similar to those of the OPC. The aim of developing alkali-activated materials (AAM) is the maximization of the incorporated recycled materials, which minimises the CO2 emissions and cost, while also achieving acceptable properties for construction applications. Therefore, various efforts are being made to produce sustainable construction materials based on different sources and raw materials. Recently, significant attention has been raised from the by-products of the steelmaking industry, mostly due to their widespread av...
Molecules, 2020
The influence of suction on the mechanical behaviour of unsaturated chemically stabilised soils i... more The influence of suction on the mechanical behaviour of unsaturated chemically stabilised soils is still mostly unknown and unquantified. This is also motivated by the difficulties associated with the experimental procedure required to fully characterise the unsaturated response of the soil, including its direct influence on traditional strength tests. The present paper presents the soil water retention curves obtained for a Portuguese soil before and after being stabilised with Portland cement (OPC) and an alkali-activated cement (AAC). Saturated undrained triaxial tests were also performed for the same curing conditions (0, 28, and 90 days). Previous attempts to characterise the retention curve of soils stabilised with AAC are unknown, and the results showed that the pore volume structure is already formed after 28 days, prior to the full development of the gel matrix responsible for the strength increase between 28 and 90 days. The curve changed after stabilisation, and with each...
Construction and Building Materials, 2019
An experimental campaign was carried out to assess shear creep behaviour of a rigid low-density c... more An experimental campaign was carried out to assess shear creep behaviour of a rigid low-density closedcell polyisocyanurate (PIR) foam. Two service temperature values were considered, 20 ºC and 30 ºC, and the applied stresses ranged between 20% and 60% of the corresponding shear strength. The results showed that a stress amplitude of 30% was enough to cause nonlinear creep response. Furthermore, creep deformations were slightly smaller in the tests at 30 ºC, a fact that matched the viscoelastic response of the PIR foam obtained from DMA testing. Finally, creep prediction curves were calibrated through an analytical approach based on the Findley's power law.
Construction and Building Materials, 2019
Introduction of new residues and wastes in the development of alkaline activated materials is a m... more Introduction of new residues and wastes in the development of alkaline activated materials is a major concern regarding the spreading and dissemination of this technique. Such increase in the spectrum of available raw materials will decrease the need for long-distance transportation of the more traditional precursors that have been tirelessly used in the past two decades (e.g. fly ash, blast furnace slag). Additionally, the use of commercial activators severely hinders its environmental and financial performance, promoting the need to develop waste-based activators. In this paper, wastes from the aluminium anodising process and the production of optical lenses were combined with low-calcium fly ash, to produce binders exclusively made from wastes and residues. The performance was assessed through uniaxial compression strength tests, which were accompanied by the monitorisation of several physical properties, including temperature, pH and weight; and by a through microscopic analysis, including scanning electron microscopy, coupled with energy dispersive spectroscopy, and x-ray diffraction, for mineralogy characterisation. Results show that the addition of glass residue and aluminium anodising sludge to class-F fly ash optimised the final precursor, which was then successfully activated with a disposed aluminium anodizing etching solution, originally used to clean the aluminium surface, prior anodization. The inclusion of soluble silicon and aluminium in the precursor raised the compression strength after short-term curing, compared with pastes prepared only with fly ash.
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Papers by Fernando Castro