Time filter

Source Type

Benavente R.,Polytechnic University of Valencia | Salvador M.D.,Polytechnic University of Valencia | Martinez-Amesti A.,University of the Basque Country | Fernandez A.,Research Center en Nanomateriales y Nanotecnologia UO PA | Borrell A.,Polytechnic University of Valencia
Materials Science and Engineering A | Year: 2016

β-eucryptite ceramics with low negative or near-zero coefficient of thermal expansion (CTE) with excellent mechanical properties, such as Young's modulus ≥100. GPa, have attracted attention for many important industrial applications. The extremely anisotropic thermal expansion behavior of this material leads to thermal residual stresses, and causes spontaneous microcracking. These microcracks cause large negative CTE with mechanical weaknesses. The appearance of microcracks is due to different factors. The most important are prolonged sintering time and heating source used.The present work shows experimentally the evolution of grain microcracks and residual stresses of the sintered β-eucryptite material going through many thermal fatigue cycles (~3600). The effect of stresses applied on β-eucryptite crystals due to the thermal cycling could be considered for explaining the small change observed of β-eucryptite to β-spodumene phase, which is higher in the samples obtained by microwave sintering. Therefore, the study of residual stresses has suggested that the heating source employed, such as conventional or microwave, has a great influence on thermal fatigue life and the final mechanical and thermal properties. The microwave heating has a significant impact on β-eucryptite materials lifetime. © 2015 Elsevier B.V.

Benavente R.,ITM University | Borrell A.,ITM University | Salvador M.D.,ITM University | Garcia-Moreno O.,Research Center en Nanomateriales y Nanotecnologia UO PA | And 2 more authors.
Ceramics International | Year: 2014

Microwave heating is proposed as the non-conventional technique for the sintering of optimal lithium aluminosilicate compositions of the β-eucryptite system. The coefficient of thermal expansion and mechanical properties of the sintered samples has been studied under the influence of microwave heating. The ad hoc synthesized β-eucryptite together with the microwave sintering technique developed in this work open the opportunity to produce breakthrough materials with low or negative coefficient of thermal expansion and excellent mechanical properties, as Young's modulus of 110 GPa. The combination of rapid heating with low energy applied by the microwave technology (eco-friendly process) and the dramatic reduction in cycle time allows densification without glass phase formation. Results of the coefficient of thermal expansion of the β-eucryptite ceramics presented here under cryogenic conditions will be of value, for example, in the future design of new composite materials for space applications. Copyright © 2013 Published by Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Benavente R.,Polytechnic University of Valencia | Salvador M.D.,Polytechnic University of Valencia | Garcia-Moreno O.,Research Center en Nanomateriales y Nanotecnologia UO PA | Penaranda-Foix F.L.,Polytechnic University of Valencia | And 2 more authors.
International Journal of Applied Ceramic Technology | Year: 2015

Lithium aluminosilicate was fabricated by conventional and nonconventional sintering: microwave and spark plasma sintering, from 1200 to 1300°C. A considerable difference in densification, microstructure, coefficient of thermal expansion behavior and hardness and Young's modulus was observed. Microwave technology made possible to obtain fully dense glass-free lithium aluminosilicate bulk material (>99%) with near-zero and controlled coefficient of thermal expansion and relatively high mechanical properties (7.1 GPa of hardness and 110 GPa of Young's modulus) compared with the other two processes. It is believed that the heating mode and effective particle packing by microwave sintering are responsible to improve these properties. © 2014 The American Ceramic Society.

Miranda M.,Research Center en Nanomateriales y Nanotecnologia UO PA | Fernandez A.,ITMA Materials Technology | Lopez-Esteban S.,Research Center en Nanomateriales y Nanotecnologia UO PA | Malpartida F.,CSIC - National Center for Biotechnology | And 2 more authors.
Journal of Materials Science: Materials in Medicine | Year: 2012

Hydroxyapatite/silver nanocomposites have been designed and synthesized as an engineering material for biomedical applications. The hydroxyapatite matrix was synthesized by a sol-gel method and, subsequently, the Ag nanoparticles were deposited by heterogeneous precipitation followed by two different reduction routes: thermal or chemical. Both sets were studied and compared and, in all cases, the metal nanoparticles appear perfectly isolated and attached to the surface of the hydroxyapatite. The average metal particle size is below 10 nm, allowing an important contact surface between silver and the microorganisms. The antimicrobial behavior against common bacteria showed a high effectiveness, well above the commercial level, as well as against yeast, in the case of the chemically reduced sample. Due to the nanocomposite microstructure, only a negligible portion of metal was released to the lixiviated liquid after the biocide tests, minimizing the risk of toxicity. These nanocomposites offer a solution to the infections on the surface of implants, one of the main problems in reaching a suitable level of osseointegration. © Springer Science+Business Media, LLC 2012.

Discover hidden collaborations