Structural and optical characterisation of planar waveguides obtained via sol-gel

8 páginas, 6 figuras, 1 tabla.-- Trabajo presentado a la "International Conference on Applications of Optics and Photonics" celebrada en Braga (Portugal) en Mayo del 2011.Planar waveguides of SiO2:TiO2 (multilayer structure) and SiO2:CeO2 (thick layer) were prepared onto commercial glass substrates using a sol-gel technique combined with dip-coating. These glassy coatings were structural characterised by Transmission Electron Microscopy (TEM) Energy Dispersive X-ray analysis and by Confocal Microscopy. Thicknesses of 1230 nm and 4,15 μm and refractive indices of 1.59 and 1.48 for SiO2:TiO2 (70:30) and SiO2:CeO2 (95:5) waveguides were obtained, respectively, by Spectroscopic Ellypsometry. Losses of 0.8 dB/cm were measured by double prism method in the SiO2:CeO2 system.The authors acknowledge funding from MICINN (TEC2006-10469, CEN 2007-2014, SURFALUX SOL-00030930 and MAT2010-18519), from DGA (Group of Excellence in Laser Material Processing and Characterisation) and XUNTA DE GALICIA (INCITE08PXIB206013PR).Peer reviewe

Procedimiento de preparación y materiales conformados basados en compuestos eutécticos binarios o ternarios de circonia

Referencia OEPM: P9600891.-- Fecha de solicitud: 19/04/1996.-- Titular: Consejo Superior de Investigaciones Científicas (CSIC).Procedimiento de preparación y materiales conformados basados en compuestos eutécticos binarios o ternarios de circonia. La presente invención está relacionada con la preparación de materiales con estructuras eutécticas micrométricas basados en mezclas de óxidos, conformados con dimensiones mili y submilimétricas mediante fusión zonal por láser con diferentes sistemas ópticos de focalización y control de los haces de los láseres. Su utilización es en el sector de la producción y conservación de energía, como elementos calefactores, refractarios, cátodos para plasmas de aire, electrodos, en componentes para celdas de combustión, microsensores de gas oxígeno, etc.Peer reviewe

The spontaneous escape behavior of silver from graphite-like carbon coatings and its effect on corrosion resistance

Silver-doped graphite-like carbon (Ag-GLC) coatings were prepared on the surface of aluminum alloy and single-crystal silicon by magnetron sputtering under different deposition parameters. The effects of silver target current and deposition temperature, as well as of the addition of CH4 gas flow, on the spontaneous escape behavior of silver from the GLC coatings were investigated. Furthermore, the corrosion resistance of the Ag-GLC coatings were evaluated. The results showed that the spontaneous escape phenomenon of silver could take place at the GLC coating, regardless of preparation condition. These three preparation factors all had an influence on the size, number and distribution of the escaped silver particles. However, in contrast with the silver target current and the addition of CH4 gas flow, only the change in deposition temperature had a significant positive effect on the corrosion resistance of the Ag-GLC coatings. The Ag-GLC coating showed the best corrosion resistance when the deposition temperature was 500 °C, which was due to the fact that increasing the deposition temperature effectively reduced the number of silver particles escaping from the Ag-GLC coating

In-situ laser synthesis of rare earth aluminate coatings in the system Ln-Al-O (Ln = Y, Gd)

Laser zone melting (LZM) was employed in this work to prepare Ln-Al-O coatings on polycrystalline Al2O3 substrates, using the corresponding mixtures of powdered rare-earth oxides and Al2O 3 as starting materials. In-situ synthesis of the compounds Ln = Y, Gd was performed using a CO2 laser, emitting at 10.6 μm. Microstructure (SEM) and phase nature (XRD) demonstrated in-situ formation of Al2O3/Y3Al5O12(YAG) and Al2O3/GdAlO3(GAP) eutectic systems. The interaction with the substrate resulted in mechanically stable, well integrated 200-500 μm thick composite coatings, as observed in nanoindentation tests. The phase relations found in these materials are consistent with the crystallographic concepts advanced by Vegas (Ramos-Gallardo & Vegas, J. Solid State Chem. 128 (1997) 69), where cation sub-arrays are proposed to play an important role in governing metal oxide structures. These sub-arrays are suggested as the structural drive behind eutectic oxide formation. LZM proves to be a convenient method to investigate the behaviour of complex oxide systems at high temperature, to apply a rational concept towards the understanding of phase relations and to develop design criteria for oxide coatings. © 2011 Elsevier Masson SAS. All rights reserved.The authors gratefully acknowledge the financial support from the Spanish Government (projects CEN 2007-2014, MAT2010- 18519 and SURFALUX SOL-00030930),Peer Reviewe

Laser floating zone growth: Overview, singular materials, broad applications, and future perspectives

The Laser Floating Zone (LFZ) technique, also known as Laser-Heated Pedestal Growth (LHPG), has been developed throughout the last several decades as a simple, fast, and crucible-free method for growing high-crystalline-quality materials, particularly when compared to the more conventional Verneuil, Bridgman-Stockbarger, and Czochralski methods. Multiple worldwide efforts have, over the years, enabled the growth of highly oriented polycrystalline and single-crystal high-melting materials. This work attempted to critically review the most representative advancements in LFZ apparatus and experimental parameters that enable the growth of high-quality polycrystalline materials and single crystals, along with the most commonly produced materials and their relevant physical properties. Emphasis will be given to materials for photonics and optics, as well as for electrical applications, particularly superconducting and thermoelectric materials, and to the growth of metastable phases. Concomitantly, an analysis was carried out on how LFZ may contribute to further understanding equilibrium vs. non-equilibrium phase selectivity, as well as its potential to achieve or contribute to future developments in the growth of crystals for emerging applications

Tratamiento de depósitos electroforéticos de YBa2Cu3O7 sobre substratos policristalinos mediante fusión zonal por láser

[EN] Obtaining coatings on metallic substrates of irregular geometries is not easy by traditional methods. In those cases electrochemical methods show important advantages and have been used successfully. To date only silver has shown to be inert with respect to superconducting cuprates, although progress has been made in the development of intermediate buffer layers. However, in the particular case of YBa2Cu3O7 , annealing above the cuprate superconducting melting point to attempt densification or texturing is hard on silver because of the lower melting point of the metal. . Focalized heating of superconducting oxides over metallic substrates, using LASER techniques on controlled geometries, allows densification of coatings. The Laser processed sample may be amorphous but the crystallinity is easily recovered, as well as the optimal oxygen content for the oxide, but the preferential orientation induced by the electrophoretic deposition is lost upon the recrystallization process occurring over polycrystaline substrates.[ES] La realización de depósitos de óxidos superconductores sobre substratos metálicos de geometría compleja y en general policristalinos está prácticamente basada en métodos electroforéticos o electroquímicos que permiten la utilización de un campo eléctrico de geometría definida para inducir el movimiento de partículas de óxido o de precursores de éste, hacia el electrodo elegido. Dichos métodos son fundamentales cuando el substrato es metálico o puede hacerse metálico con facilidad. Hasta el presente tan sólo la plata ha mostrado ser lo suficientemente inerte para permitir recocidos posteriores, aunque se está progresando en el desarrollo de capas “buffer”. Sin embargo, cuando el óxido depositado es YBa2Cu3O7 , el proceso de recocido posterior no permite la obtención de textura sobre Ag mediante métodos térmicos dado el inferior punto de fusión de este metal. El presente trabajo presenta un estudio de fusión zonal por láser que permite recocer el óxido sin fundir el substrato metálico de plata. El control de las distintas variables permite llegar a una solución en la que se puede preservar la naturaleza superconductora del depósito y su densificación. Ello requiere un tratamiento térmico posterior que recupera la cristalinidad y el contenido óptimo de oxígeno. Sin embargo, el tratamiento disminuye la orientación preferencial de las partículas de YBa2Cu3O7 que se obtiene mediante la deposición electroforética.The authors want to thank the Spanish Ministery of Culture (former Science and Education) for financing through grants CICYT MAT96-1057-c02-01, PB98-0491 and graduate fellowships, and REE for the contract CSIC-REE on 1997- 1998.Peer reviewe

Laser treatment of nanoparticulated metal thin films for ceramic tile decoration

This paper presents a new method for the fabrication of metal-like decorative layers on glazed ceramic tiles. It consists of the laser treatment of copper thin films prepared by electron beam evaporation at glancing angles. A thin film of discontinuous copper nanoparticles was electron beam evaporated in an oblique angle configuration onto ceramic tiles and an ample palette of colors obtained by laser treatment both in air and in vacuum. Scanning electron microscopy (SEM and FESEM) along with UV-vis-NIR spectroscopy and time of flight secondary ion mass spectrometry (TOF-SIMS) analysis were used to characterize the differently colored layers. Based on these analyses, color development has been accounted for by a simple model considering surface melting phenomena and different microstructural and chemical transformations of the outmost surface layers of samples.Financial support from the EU (Grant LIFE11/ENV/ES560), Innovaragon (Grant ITA-DGA/ES 1368), DGA (Group T87), MINECO (Projects MAT2013-40852-R and MAT2013-42900-P), and Junta de Andalucia (Projects TEP 8067 and FQM 6900) is gratefully acknowledged. F.R.-G. acknowledges the Portuguese Science and Technology Foundation for Grant SFRH/BPD/108581/2015.Peer reviewe

Process-generated nanoparticles from ceramic tile sintering: Emissions, exposure and environmental release

Under a Creative Commons license.-- et al.The ceramic industry is an industrial sector in need of significant process changes, which may benefit from innovative technologies such as laser sintering of ceramic tiles. Such innovations result in a considerable research gap within exposure assessment studies for process-generated ultrafine and nanoparticles. This study addresses this issue aiming to characterise particle formation, release mechanisms and their impact on personal exposure during a tile sintering activity in an industrial-scale pilot plant, as a follow-up of a previous study in a laboratory-scale plant. In addition, possible particle transformations in the exhaust system, the potential for particle release to the outdoor environment, and the effectiveness of the filtration system were also assessed. For this purpose, a tiered measurement strategy was conducted. The main findings evidence that nanoparticle emission patterns were strongly linked to temperature and tile chemical composition, and mainly independent of the laser treatment. Also, new particle formation (from gaseous precursors) events were detected, with nanoparticles  87% efficiency in particle number concentrations removal.This work was supported by the European Commission FP7 (FP7-PEOPLE-2012-ITN) Marie Curie ITN project no. 315760 (HEXACOMM) and by the Spanish MINECO (PCIN-2015-173-C02-01) under the frame of SIINN, the ERA-NET for a Safe Implementation of Innovative Nanoscience and Nanotechnology, through SIINN-ERANET project CERASAFE (id.:16). Additional support was provided by LIFE projects AIRUSE (LIFE11 ENV/ES/584), CERAMGLASS (LIFE11 ENV/ES/560) and LASERFIRING (LIFE09 ENV/ES/435).Peer Reviewe

Nanoespumas de carbono: Producción por láser, propiedades químico-físicas y potenciales aplicaciones electroquímicas y en catálisis

Trabajo presentado a la "XII Reunion del Grupo Español del Carbón" celebrada en Madrid del 20 al 23 de octubre de 2013.Este trabajo ha sido financiado por la Comisión Europea (proyecto LIFE11/ENV/ES 560 “CERAMGLASS”) y el Gobierno de Aragón (Proyecto PI119/09).Peer Reviewe

UV femtosecond laser cleaning of encrusted historical stained-glasses

Laser irradiation enables the removal of unwanted surface deposits from different materials in a safe and controllable manner. Laser parameters should be carefully selected to achieve the removal of the target contaminants without inducing damage to the substrate. Ultra-short pulse lasers have opened new opportunities for safe and controlled decontamination of cultural heritage materials because the thickness of material that is affected by the laser is limited. In this study, an ultraviolet femtosecond pulsed laser was used for the removal of unwanted encrustation formed on the surface of an historical colourless stained-glass sample from the Cuenca Cathedral in Spain. One of the sides of this glass exhibits a reddish-brown grisaille that also has to be preserved. A laser cleaning process has been designed to avoid heat accumulation while controlling the thickness of ablated material. In this context, a multi-step process was selected in order to be able to eliminate, in a controlled way, the crust layer without damaging the grisaille layer, or the glass substrate. In this case, laser irradiation in beam scanning mode with a pulse repetition frequency of 10 kHz proved to be effective for the safe cleaning of the glass. The latter was analysed before and after laser cleaning by optical and confocal microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray fluorescence, and Raman spectroscopy, confirming that the crust layer was effectively eliminated without damaging the surface