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Del Campo A.,Institute Ceramica y Vidrio ICV | De Leon A.S.,Max Planck Institute of Colloids and Interfaces | Rodriguez-Hernandez J.,CSIC - Institute of Polymer Science and Technology | Munoz-Bonilla A.,CSIC - Institute of Polymer Science and Technology
Langmuir | Year: 2017

Herein, we propose a strategy to fabricate core-shell microstructures ordered in hexagonal arrays by combining the breath figures approach and phase separation of immiscible ternary blends. This simple strategy to fabricate these structures involves only the solvent casting of a ternary polymer blend under moist atmosphere, which provides a facile and low-cost fabrication method to obtain the porous structures with a core-shell morphology. For this purpose, blends consisting of polystyrene (PS) as a major component and PS40-b-P(PEGMA300)48 amphiphilic copolymer and polydimethylsiloxane (PDMS) as minor components were dissolved in tetrahydrofuran and cast onto glass wafers under humid conditions, 70% of relative humidity. The resulting porous morphologies were characterized by optical and confocal Raman microscopy. In particular, confocal Raman results demonstrated the formation of core-shell morphologies into the ordered pores, in which the PS forms the continuous matrix, whereas the other two phases are located into the cavities (PDMS is the core while the amphiphilic copolymer is the shell). Besides, by controlling the weight ratio of the polymer blends, the structural parameters of the porous structure such as pore diameter and the size of the core can be effectively tuned. © 2017 American Chemical Society.


Vicent M.,Jaume I University | Sanchez E.,Jaume I University | Santacruz I.,University of Malaga | Moreno R.,Institute Ceramica y Vidrio ICV
Journal of the European Ceramic Society | Year: 2011

This work deals with the dispersion and stabilisation of nanosized TiO2 particles in an aqueous medium as a first step in the preparation of spray-dried nanostructured powders.A colloidal route leading to the production of titania nanostructured feedstocks to obtain nanostructured powders was developed. The process was based on the production of homogeneous and concentrated TiO2 nanosuspensions dispersed in deionised water with a suitable control of pH and the use of an appropriate anionic dispersant. Concentrated suspensions could be obtained by mixing with an ultrasounds probe at different times depending on the dispersing conditions.Homogeneous suspensions prepared were then reconstituted by spray drying into free-flowing powders with an adequate granule size distribution for diverse purposes, such as atmospheric plasma spraying coatings. © 2011 Elsevier Ltd.


De Leon A.S.,CSIC - Institute of Polymer Science and Technology | Del Campo A.,Institute Ceramica y Vidrio ICV | Fernandez-Garcia M.,CSIC - Institute of Polymer Science and Technology | Rodriguez-Hernandez J.,CSIC - Institute of Polymer Science and Technology | And 2 more authors.
Langmuir | Year: 2014

In the current paper, we prepared microstructured porous films by the breath figures approach using polymer blends consisting of polystyrene as the major component and an amphiphilic additive, either a synthetic block copolymer {two different polystyrene-b-poly[poly(ethylene glycol) methyl ether methacrylate] copolymers} or a series of commercial surfactants. Tetrahydrofuran was employed as the solvent. Confocal micro-Raman spectroscopy demonstrated the preferential location of the amphiphilic additives in the cavities of the film as a consequence of the breath figures mechanism. However, the distribution of the copolymer within the cavities varies depending upon the structure and, more precisely, the surface properties of the additives, leading to three different situations. First of all, the copolymer with a larger polystyrene segment, insoluble in the condensed water droplets, is homogeneously distributed along the whole surface of the cavities. On the contrary, when the copolymer is soluble in water (shorter polystyrene segment), it migrates inside the droplet and a coffee-stain phenomenon takes place during the water droplet evaporation, conducting to a ring-like deposition on the top edge of the cavities. Finally, when a water-soluble surfactant with high surface activity is used, the surfactant is solubilized inside the water droplets, which provokes a decrease on the surface tension and the coffee-ring effect is modified. In this situation, the copolymer covers the bottom of the pore. © 2014 American Chemical Society.


Carriazo D.,CSIC - Institute of Materials Science | Pico F.,CSIC - National Center for Metallurgical Research | Gutierrez M.C.,CSIC - Institute of Materials Science | Rubio F.,Institute Ceramica y Vidrio ICV | And 2 more authors.
Journal of Materials Chemistry | Year: 2010

Three dimensional (3D) hierarchical porous (micro-, meso- and macro-porous) carbon monoliths (HCMs) have recently been proposed as promising supercapacitor electrodes. In this work, we have further explored the use of block-copolymers as templates for the preparation of HCMs via condensation of resorcinol and formaldehyde (RF) and subsequent carbonization. The resulting HCMs exhibited a textured morphology consisting of a bicontinuous macroporous carbon network built of interconnected microporous carbon colloids, as demonstrated by nitrogen adsorption/desorption isotherms, mercury porosimetry and electron microscopy, in both scanning and transmission mode. Such a texture favored the performance of HCMs as supercapacitor electrodes, reaching remarkable values of capacitance of up to 198 F g-1 (normalized by mass) and 34.5 μF cm -2 (normalized by BET surface area). The first electrolyte infiltration into the micropore (prior capacitance measurements) was demonstrated to play a crucial role in the achievement of large capacitance values. © 2010 The Royal Society of Chemistry.


Vicent M.,Jaume I University | Sanchez E.,Jaume I University | Moreno A.,Jaume I University | Moreno R.,Institute Ceramica y Vidrio ICV
Journal of the European Ceramic Society | Year: 2012

Nanosized TiO2 powder with an average primary size of ∼20nm and surface area of ∼50m2/g (Aeroxide® P25, Degussa-Evonik, Germany) was used as starting material. A colloidal titania suspension from the same supplier was also used (W740X). The dispersing conditions were studied as a function of pH, dispersant content, and solids loading. Well-dispersed TiO2 nanosuspensions with solids contents up to 30vol.% (62wt%) were obtained by dispersing the powder with 4wt% PAA. Suspensions with solids contents as high as 35vol.% were prepared by adding the TiO2 nanoparticles to the TiO2 colloidal suspension under optimised dispersing conditions.TiO2 powder reconstitution was performed by spray drying both types of nanosuspensions to obtain free-flowing micrometre-sized nanostructured granules. The spray-dried nanostructured TiO2 granules were deposited on austenitic stainless steel coupons using atmospheric plasma spraying. Coating microstructure and phase composition were characterised using scanning electron microscopy and X-ray diffraction techniques. © 2011 Elsevier Ltd.


Vicent M.,Jaume I University | Sanchez E.,Jaume I University | Molina T.,Institute Ceramica y Vidrio ICV | Nieto M.I.,Institute Ceramica y Vidrio ICV | Moreno R.,Institute Ceramica y Vidrio ICV
Journal of the European Ceramic Society | Year: 2012

This work studies the spray drying and freeze drying of different nanosized ceramic materials and the physicochemical characteristics of the obtained granules. Colloidal suspensions of alumina, titania, and a 87/13 mixture were studied. The influence of temperature, pressure, nozzle diameter, and solids loading on the morphology and characteristics of dried granules were evaluated. It was demonstrated that these processing parameters have practically no influence, and the only parameter determining the granules characteristics is the solids content of the suspensions, in both processes. Spray drying leads to a monomodal distribution with higher granule size, while freeze drying produces more porous granules, with a bimodal intragranular distribution. The flowability of spray-dried powder is better than that of the freeze-dried powder and suit better the requirements of a feedstock targeted to obtain coatings by plasma thermal spraying whereas freeze drying can produce high porosity, softer granules. © 2011 Elsevier Ltd.


Vicent M.,Jaume I University | Bannier E.,Jaume I University | Moreno R.,Institute Ceramica y Vidrio ICV | Salvador M.D.,ITM University | Sanchez E.,Jaume I University
Journal of the European Ceramic Society | Year: 2013

In this work, Al2O3-13wt% TiO2 submicron-nanostructured powders were deposited using atmospheric plasma spraying. The feedstocks were obtained by spray drying two starting suspensions of different solids content, prepared by adding nanosized TiO2 and submicron-sized Al2O3 powders to water. The spray-dried granules were heat-treated to reduce their porosity and the powders were fully characterised in both untreated and thermally treated state. Comparison with two commercial feedstocks was carried out. Characterisation allowed a temperature for the thermal treatment to be chosen on the basis of the sprayability of the feedstock and the preservation as much as possible of the submicron-sized structure of the unfired agglomerates. Optimisation of the deposition conditions enabled the reconstituted powders to be successfully deposited, yielding coatings that were well bonded to the substrate. The coating microstructure, characterised by SEM, was mostly formed by a matrix of fully molten particles where the presence of semi-molten feedstock agglomerates was also observed. Moreover, microhardness, toughness, adhesion and tribological behaviours were determined, and the impact of the granule characteristics on these properties was studied. It was found that changing the feedstock characteristics allows controlling the coating quality and properties. In general, good mechanical properties were obtained using a feedstock comprising a binary mixture of submicrometric Al2O3 and nanometric TiO2 particles in the spray-dried powder. © 2013 Elsevier Ltd.


Munoz V.,CONICET | Pena P.,Institute Ceramica y Vidrio ICV | Martinez A.G.T.,CONICET
Ceramics International | Year: 2014

Alumina-magnesia-carbon refractories (AMC) are of great technological interest for their use as linings for iron and steelmaking ladles. In this paper, the methodology implemented for the physical, chemical and thermal characterization of AMC refractories is presented along with the obtained results. These results are essential for the study of the chemical and mechanical behavior of these materials, which the present work frames. AMC bricks comprise different amounts of alumina, sintered or electrofused magnesia, graphite and antioxidant additives bonded together with a phenolic resin. The variety of components, be they oxidic, metallic or polymeric in nature, and the complexity of the final microstructure and texture make characterizing these refractories a difficult task. In the present work, several complementary techniques were used in combination: X-ray fluorescence, plasma emission spectroscopy, gravimetry, X-ray diffraction, differential thermal and thermogrametric analyses, reflection optical microscopy and scanning electron microscopy, density and porosity measurements, dilatometric analysis and permanent linear change measurements. The results of these different techniques were analyzed separately and together in order to obtain a detailed description of each refractory in relation to its physical and chemical characteristics and thermal evolution. In addition, the characterization was completed by evaluating the mechanical properties at room temperature, such as the mechanical strength and Youngs modulus. © 2014 Elsevier Ltd and Techna Group S.r.l.


Gutierrez M.C.,CSIC - Institute of Materials Science | Rubio F.,Institute Ceramica y Vidrio ICV | Del Monte F.,CSIC - Institute of Materials Science
Chemistry of Materials | Year: 2010

Deep eutectic solvents (DES, a new class of ionic liquids) have been used as solvents to carry out the polycondensation of resorcinol-formaldehyde (RF). RF gels were characterized by FTIR and solid 13C NMR spectroscopy, and scanning electron microscopy. Solid 13C NMR spectroscopy demonstrated that the use of DES containing small amounts of water (those required to introduce formaldehyde in the solution) favored RF polycondensation as compared to that carried out in regular aqueous conditions (that is, in absence of DES). RF polycondensation also occurred in DES in its pure state (in this case, after lyophilization) albeit the reaction efficiency was difficult to evaluate given to partial elimination of formaldehyde. Carbonization of any of the RF gels obtained in DES (e.g., with or without water) resulted in the formation of monolithic carbons with conversion rates and carbon contents in range to and even slightly above those obtained in aqueous solutions. Finally, we took advantage of the excellent solvent properties of DES to suspend carbon nanotubes (CNTs) within the starting sol. Polycondensation of resorcinol and formaldehyde in DES also containing CNTs in suspension allowed the preparation of carbon-carbon nanotube RF gels and ultimately (i.e., after thermal treatment) carbon composites, having multiwall CNTs (MWCNTs) homogeneously distributed within the whole monolithic structure. © 2010 American Chemical Society.


Ramirez C.,Institute Ceramica y Vidrio ICV | Osendi M.I.,Institute Ceramica y Vidrio ICV
Journal of the European Ceramic Society | Year: 2013

Raman spectroscopy is a very useful tool to study composites containing carbon phases and in particular graphene based structures. For a Si3N4 composite containing 3wt.% of graphene nanoplateletes (GNPs) fabricated by spark plasma sintering (SPS), the main characteristics observed in the Raman spectra and the images obtained by mapping specific graphene peaks are presented. Raman images evidence differences in the relative intensity of typical D, G carbon peaks for two different specimen orientations - perpendicular and parallel to the SPS axis - attributed to the GNP orientation. An interesting difference between the Raman spectra of the GNP composite and the Si3N4 specimen similarly processed is the presence of free Si in the blank specimen, whereas in the composite the presence of SiC is observed. Both the Si and the SiC are imaged by using corresponding peaks indicating their homogenous and similar distributions in both materials. © 2012 Elsevier Ltd.

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