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Castelló de la Plana, Spain

Portillo M.C.,Institute Recursos Naturales y Agrobiologia | Gazulla M.F.,Campus Universitario Riu Sec | Sanchez E.,Campus Universitario Riu Sec | Gonzalez J.M.,Institute Recursos Naturales y Agrobiologia
Journal of the European Ceramic Society | Year: 2011

Ceramic roofing tiles suffer deterioration through time due to environmental exposure. Biological colonization affects the appearance and integrity of building materials, such as roofing tiles. The resistance to biocolonization represents an important property affecting the product quality of ceramic roofing tiles. While natural colonization of roofing tiles by organisms is a progressive, heterogeneous, and slow process, laboratory assessment of this phenomenon requires a sensitive procedure that can be carried out within a reasonable period of time. Different microorganisms have been evaluated and the use of phototrophs, specifically the cyanobacterium Oscillatoria, presented several advantages such as good adherence, homogeneous growth on surfaces, and the chlorophyll-autofluorescence which can be used for a sensitive detection. Colonization by Oscillatoria on roofing tiles was assessed by measuring the autofluorescence of cells. This study proposes the use of specific cyanobacterial cells and a simple method for monitoring biofilm formation and biological colonization of roofing tiles. © 2010 Elsevier Ltd.

Bonache V.,Polytechnic University of Valencia | Salvador M.D.,Polytechnic University of Valencia | Busquets D.,Polytechnic University of Valencia | Burguete P.,University of Valencia | And 3 more authors.
International Journal of Refractory Metals and Hard Materials | Year: 2011

Nanocrystalline tungsten carbide has been obtained by reduction/ carburization at low temperature from precursors obtained by freeze-drying of aqueous solutions. Nanocrystalline WC powders with a adequate content of carbon were mixed with submicrometric Cobalt powder (12 wt.%), obtained by same synthesis method, and sintered in vacuum furnace. The cemented carbides fabricated from experimental powders were compared with both commercial ultrafine and nanocrystalline WC-12Co mixtures consolidated by the same route. The synthesised powders were characterized by X-ray powder diffraction, elemental analysis and scanning and high resolution transmission electron microscopy. On the other hand, density, microstructure, hardness and fracture toughness together with X-ray diffraction analysis of the sintered materials were evaluated. The cemented carbides obtained from synthesised powders exhibited a WC platelet-based homogeneous microstructure. This anisotropic growth might be due to the presence of stacking faults parallel to the basal plane in the starting WC powder, which would promote the defect-assisted preferential growth. These materials showed excellent mechanical properties, with a superior hardness/fracture toughness combination compared to materials prepared from commercial mixtures. © 2010 Elsevier Ltd. All rights reserved.

De Noni Jr. A.,Instituto Maximiliano Gaidzinski | De Noni Jr. A.,Federal University of Santa Catarina | Hotza D.,Federal University of Santa Catarina | Soler V.C.,Campus Universitario Riu Sec | Vilches E.S.,Campus Universitario Riu Sec
Materials Science and Engineering A | Year: 2010

The porcelain tile is a ceramic product with high technical and aesthetic performance, whose composition is formulated from a mixture of clay or kaolin, quartz and feldspar. This paper is the first part of a study focusing on determining the influence of the porcelain tile composition on mechanical behaviour of sintered bodies. Seven compositions were prepared according to a simplex-centroid mixture design for a triaxial mixture, comprised of kaolinite, quartz and albite. The mixtures were processed reproducing industrial conditions: wet mixing followed by spray-drying, forming by pressing and fast firing with maximum temperatures ranged from 1210 to 1260 °C. The presence of kaolinite increases the dry apparent density in a significant way up to 30 wt%. Because of the fast firing, the microstructure is directly influenced by particle packing after forming. The internal porosity presented little change as a function of starting composition in the tested intervals. The surface porosity of the polished product increased with higher amounts of quartz. The results obtained in this first part of the study showed how the starting and end composition could generate the microstructure and suggest its influence on the mechanical properties of the porcelain tile, which will be later analysed in the second part of this paper. © 2009 Elsevier B.V. All rights reserved.

Marti-Calatayud M.C.,Polytechnic University of Valencia | Garcia-Gabaldon M.,Polytechnic University of Valencia | Perez-Herranz V.,Polytechnic University of Valencia | Sales S.,Campus Universitario Riu Sec | Mestre S.,Campus Universitario Riu Sec
Ceramics International | Year: 2013

Cation-exchange membranes made exclusively from ceramic materials have been synthesized by means of the impregnation of microporous ceramic supports with zirconium phosphate. Changes in the pore size distribution and total pore volume of the supports were provoked by the addition of starch as pore former in the fabrication procedure. This allowed the production of supports with increased effective electrical conductivities and with larger pores available for the zirconium phosphate deposition. An improved functionality for the exchange of cations was given to the ceramic membranes by means of their impregnation with the active particles of zirconium phosphate. The ion-exchange properties of the membranes were increased with further impregnation cycles and the resulting current-voltage curves showed a similar shape to that typical of commercial polymeric ion-exchange membranes. The production of ion-exchange membranes with increased chemical and radiation stability will broaden their applicability for the treatment of specific industrial waste waters, which are very aggressive for the current commercial ion-exchange membranes. © 2012 Elsevier Ltd and Techna Group S.r.l.

Marti-Calatayud M.C.,Polytechnic University of Valencia | Garcia-Gabaldon M.,Polytechnic University of Valencia | Perez-Herranz V.,Polytechnic University of Valencia | Sales S.,Campus Universitario Riu Sec | Mestre S.,Campus Universitario Riu Sec
Desalination and Water Treatment | Year: 2013

In this article, the innovative cation-exchange membranes obtained from ceramic materials are presented. Different microporous ceramic supports were obtained from an initial mixture of alumina and kaolin, to which a varying content of starch was added in order to obtain supports with different pore size distributions. The deposition of zirconium phosphate into the porous supports generates membranes with cation-exchange properties. The fabrication of ion-exchange membranes which could resist aggressive electrolytes such as strong oxidizing spent chromium plating baths or radioactive solutions would allow the application of electrodialysis for the decontamination and regeneration of these industrial effluents. The performance of the manufactured membranes was studied in nickel sulfate solutions by means of chronopotentiometry. An increase of the membrane voltage drop during chronopotentiometric measurements was observed in some membranes, which seems to be a consequence of concentration polarization phenomena resulting from the ionic transfer occurred through the membranes. Current-voltage curves were obtained for the different ceramic membranes, allowing the calculation of their ohmic resistance. The ohmic resistance of the membranes increased when the open porosity (OP) of the samples was incremented up to a value of 50%. For values of OP higher than 50%, the resistance of the membranes decreased significantly with porosity. © 2013 Desalination Publications.

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