Browsing by Author "Fraga D."

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    In-situ sol-gel synthesis and thin film deposition of Cu(In, Ga)(S, Se)2 solar cells
    (2013-12-17) Oliveira L.; Lyubenova T.; Martí R.; Fraga D.; Rey A.; Kozhukharov V.; Carda J.
    Chalcogenide-based solar cells Cu(In, Ga)(S, Se)2 were developed using an in-situ sol-gel method and spin coating thin film deposition. The influence of chemical composition and thermal treatment were studied in detail. It was revealed that these variables are related to band gap changes and final device performance. Increasing in band gap experimental values (1.18-1.67 eV) was observed, due to the formation of solid solution of Ga (III) and S (-II) incorporation in the crystal lattice. Optimal device performance of 3,1 % efficiency of solar energy conversion was achieved for the Cu(In1-xGax)(S, Se)2 solid solution.
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    Multifunctional smart coatings on novel ceramics and glassceramic substrates in the context of the circular economy
    (2018-01-01) Lyubenova T.S.; Fraga D.; Castelló J.B.C.; Kozhukharov V.; Machkova M.S.
    Nowadays is time of products generated by ``smart coatings`` that exhibit multiple functionalities. In particular, the construction industry is reached the point where it is possible to fabricate ``smart and sustainable`` buildings that fulfill the requirements of a growing marketplace of products and devices for ``smart cities`` generation. In addition, if the buildings are ``green``, i.e. in accordance with the today's economic model ``made to be made again`` or so-called ``circular economy`` they are very attractive and viable alternative for future businesses and industrial exploring. In this concept, we report a development sustainable ceramic and glass-ceramic tile substrates made by cheap, easily accessible and recycled materials that are further functionalized by different ``smart coatings`` for specific applications. Devices that generate and save energy, air and pollution cleaning, with anti-slip and phosphorescence properties are some examples of the overview that this publication described.
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    Rheological effect of different deflocculation mechanisms on a porcelain ceramic composition
    (2015-01-01) Barrachina E.; Llop J.; Notari M.; Fraga D.; Martí R.; Calvet I.; Rey A.; Lyubenova T.; Kozhukharov S.; Kozhukharov V.; Carda J.
    The current environmental policy imposes general optimisation of the industrial process. There are two critical steps related to suspensions fluidity in the ceramic spray-drying industry: the emptying of the ball mill and the spray-drying operation. The chemicals producers provide a large number of commercial deflocculants aiming to improve both processes. The present research is focused on the comparison of the rheological effect of four commercial liquid deflocculants on a porcelain ceramic composition in view of different mechanisms of deflocculation. The suspensions prepared have 70 %-solid content and a range of deflocculant concentrations between 0.1 mass % and 0.6 mass %. Each suspension is characterized by measuring its solid content, particle size distribution, pH values, conductivity and rheology, including viscosity at two shear rates and thixotropy calculated from the hysteresis area of the flowability curves. On the basis of the experiments carried out adequate conclusions are presented.