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

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

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

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 A potential risk for nanoparticle and ultrafine particle release to the environment was also identified, despite the fact that the efficiency of the filtration system was successfully tested and evidenced a >87% efficiency in particle number concentrations removal. (C) 2016 The Authors. Published by Elsevier B.V.Peer reviewe

Laser-assisted, crack-free surface melting of large eutectic ceramic bodies

6 páginas, 5 figuras, 1 tabla.-- El pdf del artículo es la versión post-print.The modification of ceramic surfaces by directional laser melting is interesting because it can eliminate surface defects and thus improve the ceramics mechanical performance, as long as one prevents the formation of cracks. The feasibility of surface modification by laser assisted melting on large t-ZrO2-Al2O3 eutectic ceramic pieces was evaluated in this work. 0.4 mm thick, defect free, resolidified layers were obtained on plates of 40 mm width by preheating at 1200 ºC and processing at 1000 mm/h with a line-shaped CO2 laser beam and 580 W/cm2 irradiance. The surface finish was smooth, free from overlapping-track roughness. The resolidified layer had eutectic microstructure with lamellae-type Al2O3 and tetragonal ZrO2(t-ZrO2) colonies. The fracture tests of the samples confirmed the absence of crack type resolidification defects and the removal of surface defects. Although no increase in average flexural strength was observed for surface resolidified samples, they showed significantly lower standard deviation.Spanish Government; European Community FEDER program; CSIC; DGA MAT2006-13005-C03-01; MAT2009-13979-C03-03; CEN2007-2014Peer reviewe

Horno láser continuo para síntesis de cerámicas avanzadas

Resumen del trabajo presentado al LII Congreso Anual de la Sociedad Española de Cerámica y Vidrio celebrado en Burgos del 3 al 6 de octubre de 2012.La síntesis de materiales cerámicos requiere un tratamiento térmico a temperaturas elevadas. Los hornos de laboratorio convencionales que en su mayoría son eléctricos permiten alcanzar temperaturas próximas a los 1700ºC en aire. A estas temperaturas ya aparecen problemas importantes de interacción entre los materiales de soporte o crisoles con el material procesado. Para alcanzar temperaturas más elevadas se hace uso de hornos de atmósfera controlada, de arco eléctrico, generadores de plasma, irradiación láser o solar, etc. Los hornos de atmósfera controlada para temperaturas superiores a 1700ºC actualmente se usan poco por su alto coste de instalación y mantenimiento. De los otros tipos de calentamiento, destaca la irradiación láser por ofrecer excelente control espacial y temporal y permitir alcanzar temperaturas extremas, tal y como es necesario para fundir prácticamente cualquier material sólido. No obstante, el estrés térmico asociado a los elevados gradientes de temperatura inducidos en la zona irradiada es un inconveniente característico en casi cualquier proceso realizado con láser, que provoca la aparición de grietas y otros defectos en el material procesado. Para evitar estos problemas es necesaria la combinación de irradiación láser con aporte de calor externo, tal y como se ha demostrado por primera vez en nuestro laboratorio. Se han desarrollado varios equipos que permiten procesar materiales en el interior de un horno contínuo, eléctrico o de gas natural, y simultáneamente irradiar la muestra con láser. La combinación de barrido de haz láser con una velocidad de pieza adecuada permite fundir la superficie del material, dejando la mayor parte de su espesor (volumen) sin fundir. El resultado es un material recubierto con una capa refundida a la temperatura de fusión de la mezcla de fases sólidas presentes en el entorno de la superficie expuesta al láser. Aunque el calentamiento intenso y localizado por láser induce importantes gradientes térmicos en el material irradiado, la aparición de grietas se evita realizando el proceso a temperaturas de horno relativamente bajas (450‐1200ºC). Utilizando el horno láser desarrollado en el ICMA se han preparado recubrimientos cerámicos compuestos, modificaciones de superficies a temperaturas extremas y se han desarrollado procesos industriales de fabricación de cerámica estructural dentro del proyecto europeo LIFE09 ENV/ES/000435 "LASERFIRING". En este trabajo se presenta un estudio sobre la influencia del barrido y potencia láser, temperatura de horno y velocidad de muestra en el proceso.Peer reviewe

Microstructure and transport properties of Bi-2212 prepared by CO 2 laser line scanning

A novel Laser Line Scanning method has been applied to process rectangular cross-section Bi-2212 monoliths containing 2.9 % Ag using a CO2 Laser. Although previous work has suggested the use of nIR lasers (?0.8-1.1 µm) for melt-processing metal oxide superconductors, the results obtained here demonstrate that mid-IR radiation from a CO2 laser (10.6 µm) may be just as convenient for such a purpose while it enables processing large surface areas. The samples described here were processed at traverse rates ranging between 15 and 60 mm/h, exhibited a complex textured microstructure and yielded highest Ic values of 71 A at 77 K. © 2012 Springer Science+Business Media New York.LIFE11/ENV/ES 560 Direction Générale de l’Armement: Superconductivity MAT2011-22719, MAT2008-00429 Universidad de Zaragoza: UZ2011-TEC-03Acknowledgements The authors acknowledge the European Commission LIFE Program (LIFE11/ENV/ES 560 “CERAMGLASS”), the Spanish MINECO and European Commission FEDER Program (Projects MAT2008-00429 and MAT2011-22719), Universidad de Zaragoza (Project UZ2011-TEC-03 and Servicio General de Apoyo a la Investigación-SAI), as well as DGA for Groups T87 (Laser Applications Lab) and T13 (Applied Superconductivity)

Laser‐assisted synthesis of colloidal FeWxOy and Fe/FexOy nanoparticles in wWater and ethanol

Homogeneous polycrystalline FexOy nanoparticles were generated by ablation of iron targets in water by nanosecond laser pulses at 532 nm. In ethanol, crystalline core‐shell Fe/FexOy structures with size medians around 20 nm were produced. The ablation of FeWxOy targets in water resulted in crystalline hollow shells and homogeneous FeWxOy nanoparticles. In contrast, amorphous core‐shell FeWxOy nanoparticles with a median size of 17 nm were produced in ethanol. The size distribution of both the FexOy and the FeWxOy particles showed a slight dependence on fluence and pulse number. This may be related to primary and secondary ablation and modification mechanisms.Partial financial support by the H2020 Action MSCA‐IF 656908‐NIMBLIS‐ESR is acknowledged. Further partial funding came from the National Science Foundation through Grant CMMI‐1301298, and the MAT2015‐67354‐R project of the Spanish Ministry of Economy and Competitiveness (MINECO).Peer reviewe

Processing of textured superconductors with a continuous laser furnace

Resumen del trabajo presentado a la: "3rd International Conference on Superconductivity and Magnetism" celebrada en Estambul (Turquia) del 29 de abril al 4 de mayo de 2012.Texture control in oxide superconductors has been studied intensively since the discovery of High temperature superconductivity. Efforts to induce texture with laser heating have been widely published in the literature, using systems, which usually made no use of external heating to avoid microcrack formation due to excessive thermal stress around the laser incidence area. The typical cylindrical geometry, most often used in Laser Float Zone Melting (LFZ) hindered the development of appropriate heating devices, thus efforts were launched in order to design a Laser Zone Melting system where the effect of external heating of the superconductor could be ascertained in order to obtain textured superconducting material in planar geometries. A number of papers have thus appeared in the literature based on Laser Zone Melting of Bi-2212. Recently, the method has been improved with the use of a patented continuous Laser Furnace, which will be described here. Combination of colloidal processing and continuous Laser Furnace has been used to fabricate superconducting coatings on different ceramics substrates. In particular we will present results about the optimization of colloidal processing of Bi-2212, RE-123, RE-211 and Cu5Ba3O8 green tapes as well as BaZrO3 substrates. Surface modification of the substrates and texture of the superconducting materials have been reached using a continuous Laser Furnace. The effects of the laser parameters and the temperature of the furnace on the microstructure and physical properties of the samples are also presented. Results show the potential of these processing techniques in the controlled modification of the microstructure and properties of different ceramic materials.Peer reviewe

Laser synthesis and luminescence properties of SrAl2O4:Eu2+, Dy3+ phosphors

A laser melting method has been developed for the synthesis of highly luminescent, long-lasting SrAl2O4:Eu2+, Dy3+ phosphors. The high temperature achieved in high-power density CO2 laser irradiation of mixtures of SrCO3, Al2O3, Eu2O3, and Dy2O3 enabled the one-step, fast synthesis of these phosphors in air at atmospheric pressure. X-ray diffraction, Raman spectroscopy, and scanning electron microscopy characterization studies reveal that the produced materials consist of monoclinic SrAl2O4 grains extensively surrounded by rare-earth ion-enriched grain boundaries. The photoluminescence properties of laser-produced SrAl2O4:Eu2+, Dy3+ materials are discussed. The results reported here suggest that this laser melting method is a promising route for the synthesis of ceramic phosphors. It is presented as an alternative to the conventional sol–gel and solid-state methods, which require the use of high-temperature furnaces, flux additives, and reducing atmospheres.The authors acknowledge financial support from the Spanish Ministry of Science and Innovation (MICINN, projects CEN-20072014, SOL-00030930, MAT2010-18519 and MAT2010-19837-C06-06), IMPLASER 99 S.L.L. (http://www.implaser.com), and the regional Government of Aragón (Spain, project PI119/09, and Excellence Research Groups Program T87).Peer Reviewe