Browsing by Author "Bordado, J. C."
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- Advances on the development of novel heterogeneous catalysts for transesterification of triglycerides in biodieselPublication . Puna, Jaime; Gomes, João; Correia, M. Joana N.; Dias, A. P. Soares; Bordado, J. C.This paper describes experimental work done towards the search for more profitable and sustainable alternatives regarding biodiesel production, using heterogeneous catalysts instead of the conventional homogenous alkaline catalysts, such as NaOH, KOH or sodium methoxide, for the methanolysis reaction. This experimental work is a first stage on the development and optimization of new solid catalysts, able to produce biodiesel from vegetable oils. The heterogeneous catalytic process has many differences from the currently used in industry homogeneous process. The main advantage is that, it requires lower investment costs, since no need for separation steps of methanol/catalyst, biodiesel/catalyst and glycerine/catalyst. This work resulted in the selection of CaO and CaO modified with Li catalysts, which showed very good catalytic performances with high activity and stability. In fact FAME yields higher than 92% were observed in two consecutive reaction batches without expensive intermediate reactivation procedures. Therefore, those catalysts appear to be suitable for biodiesel production.
- Assessment of exposure to airborne ultrafine particles in the urban environment of Lisbon, PortugalPublication . Albuquerque, Paula Cristina; Gomes, João F.; Bordado, J. C.The aim of this study was the assessment of exposure to ultrafine in the urban environment of Lisbon, Portugal, due to automobile traffic, and consisted of the determination of deposited alveolar surface area in an avenue leading to the town center during late spring. This study revealed differentiated patterns for weekdays and weekends, which could be related with the fluxes of automobile traffic. During a typical week, ultrafine particles alveolar deposited surface area varied between 35.0 and 89.2 μm2/cm3, which is comparable with levels reported for other towns such in Germany and the United States. These measurements were also complemented by measuring the electrical mobility diameter (varying from 18.3 to 128.3 nm) and number of particles that showed higher values than those previously reported for Madrid and Brisbane. Also, electron microscopy showed that the collected particles were composed of carbonaceous agglomerates, typical of particles emitted by the exhaustion of diesel vehicles. Implications: The approach of this study considers the measurement of surface deposited alveolar area of particles in the outdoor urban environment of Lisbon, Portugal. This type of measurements has not been done so far. Only particulate matter with aerodynamic diameters <2.5 (PM2.5) and >10 (PM10) μm have been measured in outdoor environments and the levels found cannot be found responsible for all the observed health effects. Therefore, the exposure to nano- and ultrafine particles has not been assessed systematically, and several authors consider this as a real knowledge gap and claim for data such as these that will allow for deriving better and more comprehensive epidemiologic studies. Nanoparticle surface area monitor (NSAM) equipments are recent ones and their use has been limited to indoor atmospheres. However, as this study shows, NSAM is a very powerful tool for outdoor environments also. As most lung diseases are, in fact, related to deposition of the alveolar region of the lung, the metric used in this study is the ideal one.
- Assessment of exposure to airborne ultrafine particles in the urban environment of Lisbon, PorugalPublication . Gomes, João; Albuquerque, Paula Cristina; Bordado, J. C.The aim of this study was the assessment of exposure to ultrafine in the urban environment of Lisbon, Portugal, due to automobile traffic, and consisted of the determination of deposited alveolar surface area in an avenue leading to the town center during late spring. This study revealed differentiated patterns for weekdays and weekends, which could be related with the fluxes of automobile traffic. During a typical week, ultrafine particles alveolar deposited surface area varied between 35.0 and 89.2 mu m(2)/cm(3), which is comparable with levels reported for other towns such in Germany and the United States. These measurements were also complemented by measuring the electrical mobility diameter (varying from 18.3 to 128.3 nm) and number of particles that showed higher values than those previously reported for Madrid and Brisbane. Also, electron microscopy showed that the collected particles were composed of carbonaceous agglomerates, typical of particles emitted by the exhaustion of diesel vehicles. Implications: The approach of this study considers the measurement of surface deposited alveolar area of particles in the outdoor urban environment of Lisbon, Portugal. This type of measurements has not been done so far. Only particulate matter with aerodynamic diameters <2.5 (PM2.5) and >10 (PM10) mu m have been measured in outdoor environments and the levels found cannot be found responsible for all the observed health effects. Therefore, the exposure to nano- and ultrafine particles has not been assessed systematically, and several authors consider this as a real knowledge gap and claim for data such as these that will allow for deriving better and more comprehensive epidemiologic studies. Nanoparticle surface area monitor (NSAM) equipments are recent ones and their use has been limited to indoor atmospheres. However, as this study shows, NSAM is a very powerful tool for outdoor environments also. As most lung diseases are, in fact, related to deposition of the alveolar region of the lung, the metric used in this study is the ideal one.
- Edible films to improve quality and shelf life of fresh tortillasPublication . Serrano, Carmo; Santos, Rafael; Viegas, Cláudia; Sapata, M. Margarida; Santos, R. Galhano dos; Condeço, J. A.; Marques, Ana C.; Bordado, J. C.Edible films have emerged as packaging aids to replace synthetic polymers due to their biodegradable nature. The aim of this study was to develop starch-based edible films for application in packaging, to inhibit moisture transfer from the filling to the tortilla, while maintaining physicochemical and organoleptic quality characteristics, and improving shelf life. Twenty-four types of filmogenic solutions were produced by casting from corn, pea, and chestnut starch blended with agar, guar, and potassium alginate, using glycerol as a plasticizer. The films were selected due to its surface properties and water absorption capacity, which allowed selecting the films that best retained moisture. The hydration properties of the selected films allowed to verify that the corn and pea starch films show good resistance to water and microbial development. Microstructural properties showed that the pea starch films exhibit a homogeneous and smooth surface without porosity. Fourier Transform Infrared Micro-Spectroscopy allowed the characterization of the starch films at the molecular level. The mechanical properties of corn and pea starch films were evaluated in tensile strength (21.98–27.5 KPa), elongation at break (59.17–185.96%), and elastic modulus (42.35–17.09 MPa). The results suggest that pea films are more flexible than starch films due to differences in the amylose and amylopectin molecules and molecular masses of the different starches. The sensory analysis concluded that the pea starch film delayed moisture transfer from the filling to the tortilla, maintaining the texture, appearance, and organoleptic characteristics for 6 days, improving the consumption experience of these food products.
- Estudo de argamassas de base cimentícia por microscopia electrónica de varrimentoPublication . Costa, Carla; Carvalho, P. Almeida de; Bordado, J. C.; Nunes, A.Cement-based materials possess a heterogeneous microstructure that changes over time. Scanning electron microscopy is an experimental technique that allows the observation of materials in a wide range of magnifications and can be associated with local chemical analysis. This work describes the fundamental microstructural characteristics of cementbased materials and presents experimental results of Portland cement mortars analysis by scanning electron microscopy. Keywords: Cement-based materials, Microstructure, Scanning electron microscopy. Os materiais de base cimentícia possuem uma microestrutura heterogénea e que se altera ao longo do tempo. A microscopia electrónica de varrimento é uma técnica experimental que permite a observação de materiais numa vasta gama de ampliações e à qual se pode associar análise química local. Neste trabalho descrevem-se as características fundamentais da microestrutura de materiais de base cimentícia e apresentam-se resultados experimentais da análise de argamassas de cimento Portland por microscopia electrónica de varrimento. palavras chave: Materiais de base cimentícia, Microestrutura, Microscopia electrónica de varrimento.