Research Center en Nanomateriales y Nanotecnologia

Llanera, Spain

Research Center en Nanomateriales y Nanotecnologia

Llanera, Spain
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Centeno A.,CSIC - National Coal Institute | Rocha V.G.,ITMA MaterialsTechnology | Borrell A.,Research Center en Nanomateriales y Nanotecnologia | Blanco C.,CSIC - National Coal Institute | And 2 more authors.
Ceramics International | Year: 2012

Carbon fibre-reinforced silicon carbide composites (C-SiC) were fabricated combining, for the first time, a liquid infiltration process (LI) of a mesophase pitch doped with silicon carbide nanoparticles followed by reactive liquid silicon infiltration using Spark Plasma Sintering (SPS) technique. A graphitization step was applied in order to improve the effectiveness of the processing. Up to three different morphologies of SiC particles were identified with a noticeable influence on the preliminary oxidation tests carried out. The presence of SiC nanoparticles added to the carbon matrix affects the morphology of the SiC obtained by in situ reaction of silicon and carbon during the LI process by SPS and it leads to an improvement of the material oxidation resistance. The results show that SPS is a promising method to develop C-SiC composites in a short time and with a high efficiency in the liquid silicon infiltration process. © 2011 Elsevier Ltd and Techna Group S.r.l.


Alvarez-Clemares I.,Research Center en Nanomateriales y Nanotecnologia | Borrell A.,Polytechnic University of Valencia | Agouram S.,University of Valencia | Torrecillas R.,Research Center en Nanomateriales y Nanotecnologia | Fernandez A.,Research Center en Nanomateriales y Nanotecnologia
Scripta Materialia | Year: 2013

The specific effects of spark plasma sintering (SPS) on the creep behavior, microstructure and mechanical properties of alumina monolithic ceramic were investigated. SPS introduces strains that concentrate at grain boundaries and inhibit crack growth, resulting in an improvement in the flexural strength and fracture toughness. However, creep blocks grain boundary movements and decreases the reliability of the material. These strains can be removed by a post-sintering thermal treatment, which plays an important role in the distribution of dislocations.


Espinosa-Fernandez L.,Polytechnic University of Valencia | Borrell A.,Polytechnic University of Valencia | Salvador M.D.,Polytechnic University of Valencia | Gutierrez-Gonzalez C.F.,Research Center en Nanomateriales y Nanotecnologia
Wear | Year: 2013

The present work aims are to study the dry sliding wear behavior of WC-12wt%Co materials, with or without addition of Cr3C2/VC grain growth inhibitors, and to sinter them by two different consolidation techniques: conventional sintering and spark plasma sintering (SPS). The dry sliding wear tests were performed on a tribometer with a ball-on-disc configuration using a WC-Co ball as a counterpart material with a normal contact load of 60N, a sliding distance of 10,000m and a sliding speed of 0.1m/s. The influence of the grain growth inhibitors and the consolidation techniques in sintered samples were related to the friction coefficient, wear rates and wear pattern damage. Samples sintered by non-conventional technique (SPS) show the best wear resistance and lower friction coefficient. The addition of inhibitors reduces the wear rates in materials consolidated by both techniques. The differences in the wear damage are related to microstructural parameters, mechanical properties and wear rates. © 2013.


Garcia-Moreno O.,Research Center en Nanomateriales y Nanotecnologia | Fernandez A.,Fundacion ITMA | Torrecillas R.,Research Center en Nanomateriales y Nanotecnologia
Ceramics International | Year: 2011

Lithium aluminosilicate powder precursors of compositions Li 2O:Al2O3:SiO2 as 1:1:2; and 1:1:3.11 were synthesized and sintered by the Spark Plasma Sintering technique. The sintering conditions were adjusted to obtain dense ceramic materials in an attempt to avoid the presence of a glassy phase. XRD and SEM images were employed for composition and microstructure characterization. The coefficient of thermal expansion of the sintered samples was studied down to cryogenic conditions. Rietveld quantification was performed with the use of an external standard. Pure β-eucryptite of different compositions in dense ceramic bodies was obtained with a negative expansion coefficient. © 2011 Elsevier Ltd and Techna Group S.r.l.


De La Iglesia P.G.,Research Center en Nanomateriales y Nanotecnologia | Garcia-Moreno O.,Research Center en Nanomateriales y Nanotecnologia | Torrecillas R.,Research Center en Nanomateriales y Nanotecnologia | Menendez J.L.,Research Center en Nanomateriales y Nanotecnologia
Ceramics International | Year: 2012

Calcium hexaluminate (CaAl 12O 19) is the most alumina-rich intermediate compound of the CaO-Al 2O 3 system. The formation of this aluminate is produced by the reaction between calcium oxide and alumina. Intermediate compounds with lower alumina content (CaAl 2O 4, CaAl 4O 7,⋯) are formed during the synthesis of calcium hexaluminate with increasing temperature. With the aim to obtain dense and pure calcium hexaluminate by reaction sintering method using Spark Plasma Sintering (SPS) the variation of sintering parameters was studied. Final densities close to the theoretical and calcium hexaluminate formation rates over 93% were achieved by this method. Once the sintering parameters were optimized, a study of the flexural strength and the hardness of the samples were performed.


Garcia-Moreno O.,Research Center en Nanomateriales y Nanotecnologia | Fernandez A.,Fundacion ITMA | Khainakov S.,Research Center en Nanomateriales y Nanotecnologia | Torrecillas R.,Research Center en Nanomateriales y Nanotecnologia
Scripta Materialia | Year: 2010

Five lithium aluminosilicate compositions of the LAS system have been synthesized and sintered. The coefficient of thermal expansion of the sintered samples has been studied down to cryogenic conditions. The data presented here under cryogenic conditions will be of value in the future design of new composite materials with very low thermal expansion values. The variation in thermal expansion properties with composition and sintering temperature was studied and is discussed in relation to composition and crystal structure. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.


Borrell A.,Research Center en Nanomateriales y Nanotecnologia | Rocha V.G.,ITMA Materials Technology | Torrecillas R.,Research Center en Nanomateriales y Nanotecnologia | Fernandez A.,ITMA Materials Technology
Journal of the American Ceramic Society | Year: 2011

The development of new carbon nanofibers (CNFs)-ceramic nanocomposite materials with excellent mechanical, thermal, and electrical properties is interesting for a wide range of industrial applications. Among the ceramic materials, zirconia stands out for their excellent mechanical properties. The main limitations in the preparation of this kind of nanocomposites are related with the difficulty in obtaining materials with homogeneous distribution of both phases and the dissimilar properties of CNFs and ZrO 2 which causes poor interaction between them. CNFs-reinforced zirconia nanocomposites ZrO 2/xCNFs (x=1-20 vol%) were prepared by powder mixture and sintered by spark plasma sintering (SPS). ZrO 2-reinforced CNFs nanocomposites CNFs/xZrO 2 (x=20 vol%) were prepared by powder mixture and a surface coating of CNFs by the wet chemical route with zirconia precursor is proposed as a very effective way to improve the interaction between CNFs and ZrO 2. After SPS sintering, an improvement of 50% in fracture strength was found for similar nanocomposite compositions when the surface coating was used. The improved mechanical properties of these nanocomposites are caused by stronger interaction between the CNFs and ZrO 2. © 2011 The American Ceramic Society.


Bonache V.,ITM University | Salvador M.D.,ITM University | Fernandez A.,Fundacion ITMA | Borrell A.,Research Center en Nanomateriales y Nanotecnologia
International Journal of Refractory Metals and Hard Materials | Year: 2011

The aim of present work is to study the effect of VC and/or Cr 3C2 in densification, microstructural development and mechanical behavior of nanocrystalline WC-12wt.%Co powders when they are sintered by spark plasma sintering (SPS) and hot isostatic pressing (HIP). The results were compared to those corresponding to conventional sintering in vacuum. The density, microstructure, X-ray diffraction, hardness and fracture toughness of the sintered materials were evaluated. Materials prepared by SPS exhibits full densification at lower temperature (1100 °C) and a shorter stay time (5 min), allowing the grain growth control. However, the effect of the inhibitors during SPS process is considerably lower than in conventional sintering. Materials prepared by HIP at 1100 °C and 30 min present full densification and a better control of microstructure in the presence of VC. The added amount of VC allows obtaining homogeneous microstructures with an average grain size of 120 nm. The hardness and fracture toughness values obtained were about 2100 HV30 and close to 10 MPa m1/2, respectively. © 2010 Elsevier Ltd. All rights reserved.


Fernandez-Garcia L.,Research Center en Nanomateriales y Nanotecnologia | Suarez M.,Research Center en Nanomateriales y Nanotecnologia | Menendez J.L.,Research Center en Nanomateriales y Nanotecnologia
Journal of Alloys and Compounds | Year: 2010

A transition from a low to a high spin state in the magnetization saturation between 1000 and 1100 °C calcination temperature is observed in YIG powders prepared by oxides mixture. Spark plasma sintering of these powders between 900 and 950 °C leads to dense samples with minimal formation of YFeO3, opening the way to co-sintering of YIG with metals or metallic alloys. The optical properties depend on the sintering stage: low (high) density samples show poor (bulk) optical absorption. © 2010 Elsevier B.V. All rights reserved.


Borrell A.,Research Center en Nanomateriales y Nanotecnologia | Torrecillas R.,Research Center en Nanomateriales y Nanotecnologia | Rocha V.G.,ITMA Materials Technology | Fernandez A.,ITMA Materials Technology
Fuel Cells | Year: 2012

There is an increasing demand of multifunctional materials for a wide variety of technological developments. Bipolar plates for proton exchange membrane fuel cells are an example of complex functionality components that must show among other properties high mechanical strength, electrical, and thermal conductivity. The present research explored the possibility of using alumina-carbon nanofibers (CNFs) nanocomposites for this purpose. In this study, it was studied for the first time the whole range of powder compositions in this system. Homogeneous powders mixtures were prepared and subsequently sintered by spark plasma sintering. The materials obtained were thoroughly characterized and compared in terms of properties required to be used as bipolar plates. The control on material microstructure and composition allows designing materials where mechanical or electrical performances are enhanced. A 50/50vol.% alumina-CNFs composite appears to be a very promising material for this kind of application. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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