Enhanced quench propagation in 2G-HTS coils co-wound with stainless steel or anodised aluminium tapes

Early quench detection and thermal stability of superconducting coils are of great relevance for practical applications. Magnets made with second generation high temperature superconducting (2G-HTS) tapes present low quench propagation velocities and therefore slow voltage development and high local temperature rises, which may cause irreversible damage. Since quench propagation depends on the anisotropy of the thermal conductivity, this may be used to achieve an improvement of the thermal stability and robustness of 2G-HTS coils. On pancake type coils, the thermal conductivity along the tapes (coil's azimuthal direction) is mostly fixed by the 2G-HTS tape characteristics, so that the reduction of anisotropy relies on the improvement of the radial thermal conductivity, which depends on the used materials between superconducting tapes, as well as on the winding and impregnation processes. In this contribution, we have explored two possibilities for such anisotropy reduction: by using anodised aluminium or stainless steel tapes co-wound with the 2G-HTS tapes. For all the analysed coils, critical current distribution, minimum quench energy values and both tangential and radial quench propagation velocities at different temperatures and currents are reported and compared with the results of similar coils co-wound with polyimide (Kapton®) tapes.This work was supported by the Spanish Ministerio de Economía y Competitividad and the European FEDER Program (Projects MAT2011-22719 and ENE-2014-52105-R), and by the Gobierno de Aragón (research group T12).Peer reviewe

Application of digital speckle interferometry to visualize surface changes in metallic samples immersed in Cu(NO3)2 solutions

Digital speckle pattern interferometry (DSPI) has been applied to analyze surface corrosion processes in a metallic sample immersed in a 0.1 M Cu(NO3)2 solution. The corrosion process induces changes in the surface and in the solution refractive index. A detailed analysis of the DSPI measurements has been performed to obtain a two-dimensional visualization of the surface changes and an evaluation of the refractive index changes of the solution. The possibilities of DSPI for measuring surface changes in these conditions have been analyzed.Funding of this research by Spanish MINECO and the European FEDER Program (Project MAT2011-22719) and by Gobierno de Aragón (Research groups T12 and T76) is gratefully acknowledged. Authors would also like to acknowledge the use of Servicio General de Apoyo a la Investigación-SAI, Universidad de Zaragoza.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

Ultra-Short Pulse Laser Cleaning of Contaminated Pleistocene Bone: A Comprehensive Study on the Influence of Pulse Duration and Wavelength

The impact of wavelength and pulse duration in laser cleaning of hard blackish contaminants crust from archaeologically significant Pleistocene bone is investigated in this research. The objective is to determine the practical cleaning procedures and identify adequate laser parameters for cleaning archaeological bone from Sima de los Huesos (Spain) based on conservation and restoration perspectives. Bone surface cleaning was performed utilizing two Q-switched Nd:YAG lasers: sub-nanosecond pulsed lasers with emission wavelengths at 355 nm and 1064 nm, respectively, and a Yb:KGW femtosecond pulsed laser with an emission wavelength in the third harmonic at 343 nm. In all experiments, the laser beam scanning mode was applied to measure cleaning efficiency in removing contaminants and degradation products while assessing the underlying substrate surface damage. Several properties, including wavelength-dependent absorption, pulse repetition rate, and thermal properties of the material, are analyzed when evaluating the ability of these lasers to boost the cleaning efficiency of the deteriorated bone surface. Bone surface morphology and composition were studied and compared before and after laser irradiation, using Optical Microscopy, Scanning Electron Microscopy with Energy Dispersive X-ray Spectrometry (SEM-EDS), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Photoelectron Spectroscopy (XPS) characterization methods. The results indicate that 238-femtosecond UV laser irradiation with 2.37 TWcm−2 is significantly safer and more efficient toward surface contaminant desorption than sub-nanosecond laser irradiation. The results herein presented suggest that these types of fs lasers may be considered for realistic laser conservation of valuable historic and archaeological museum artifacts

Ultrashort pulsed Femtosecond UV laser for selective cleaning of significant Cretaceous flints

This work reports on studies aimed to evaluate the utilization of ultrashort 238 fs (fs) pulsed UV laser emission at 343 nm for eliminating colored crusts and surface deposits on significant Cretaceous flint surfaces, in an attempt to safeguard its aesthetic appearance and archaeological value. The results indicate that fs UV lasers may be an ideal, non-contact tool for selective surface cleaning of sensitive archaeological artefacts, since they enable contaminant desorption while avoiding photothermal damage

Highly regular hexagonally-arranged nanostructures on Ni-W alloy tapes upon Irradiation with ultrashort UV laser pulses

This article belongs to the Special Issue Dynamics and Processes at Laser-Irradiated Surfaces—A Themed Issue in Honor of the 70th Birthday of Professor Jürgen Reif.Nickel tungsten alloy tapes (Ni—5 at% W, 10 mm wide, 80 µm thick, biaxially textured) used in second-generation high temperature superconductor (2G-HTS) technology were laser-processed in air with ultraviolet ps-laser pulses (355 nm wavelength, 300 ps pulse duration, 250–800 kHz pulse repetition frequency). By employing optimized surface scan-processing strategies, various laser-generated periodic surface structures were generated on the tapes. Particularly, distinct surface microstructures and nanostructures were formed. These included sub-wavelength-sized highly-regular hexagonally-arranged nano-protrusions, wavelength-sized line-grating-like laser-induced periodic surface structures (LIPSS, ripples), and larger irregular pyramidal microstructures. The induced surface morphology was characterized in depth by electron-based techniques, including scanning electron microscopy (SEM), electron back scatter diffraction (EBSD), cross-sectional transmission electron microscopy (STEM/TEM) and energy dispersive X-ray spectrometry (EDS). The in-depth EBSD crystallographic analyses indicated a significant impact of the material initial grain orientation on the type of surface nanostructure and microstructure formed upon laser irradiation. Special emphasis was laid on high-resolution material analysis of the hexagonally-arranged nano-protrusions. Their formation mechanism is discussed on the basis of the interplay between electromagnetic scattering effects followed by hydrodynamic matter re-organization after the laser exposure. The temperature stability of the hexagonally-arranged nano-protrusion was explored in post-irradiation thermal annealing experiments, in order to qualify their suitability in 2G-HTS fabrication technology with initial steps deposition temperatures in the range of 773–873 K.The authors gratefully acknowledge the financial support from the Scientific and Technological Research Council of Turkey (TUBITAK) ARDEB 1001 (project number: 117F399) program, the Spanish MCIN/AEI/10.13039/501100011033 (project PID2020-113034RB-I00), the LaserImplant project (European Union’s Horizon 2020 research and innovation program under grant agreement No. 951730) and from Gobierno de Aragón (research group T54_20R).Peer reviewe

Del colesterol a la tele plana

Artículo de divulgacion publicado en prensa.El ICMA trata de despertar el interés por la ciencia en los laumnos de la ESO a tráves de experimentos con aplicaciones de los cristales líquidos.Programa Ciencia Viva patrocinado por: DreamGlass, SURISA y 3M-Speedglas.Peer reviewe

Thermal stability analysis of YBCO-coated conductors subject to over-currents

8 páginas, 9 figuras, 1 tabla.-- et al.The thermal stability of superconducting YBCO-coated conductors subject to over-currents are analysed. We have studied the effect of DC and AC over-current pulses in Cu-stabilized and non-stabilized coated conductors by measuring the electric field and temperature profiles of these conductors immersed in liquid nitrogen. Current pulses of short duration of about 90 ms and long duration of a few seconds were applied to the samples. Three different cooling regimes of liquid nitrogen—convection, nucleate boiling and film boiling—were observed and their influence on the recovery time of superconductivity in the coated conductors after the over-current pulses has been analysed. We have studied the recovery behaviour under two different conditions, in which the current was set to zero and to the operating current after the current pulses. These experiments simulated the conditions during an over-current situation in different electric power applications with special attention given to the behaviour of these coated conductors acting as in-fault current limiters.This work was supported by the Spanish Ministry of Science and Innovation, MAT2008-06279-C03-01.Peer reviewe

Desarrollo de materiales compuestos cerámicos reforzados con fibras de sílice

Resumen del póster presentado a la 6ª Jornada de Jóvenes Investigadores en Física y Química de Aragón celebrada en Zaragoza el 20 de noviembre de 2014.Peer reviewe

II Escuela de materiales: una propuesta para introducir la enseñanza sobre materiales en educación secundaria y bachillerato

Trabajo presentado al XI Congreso Nacional de Materiales: "Educación en Materiales", celebrado en Zaragoza del 23 al 25 de junio de 2010.Cuando la Sociedad Española de Materiales encargó al Instituto de Ciencia de Materiales de Aragón la organización de la II Escuela de Materiales le pidió que estuviera especialmente dirigida a profesores de educación secundaria y bachillerato. Por ello, desde un principio se organizó en colaboración con el Programa Ciencia Viva. El objetivo era dedicar la Escuela a un tema que permitiera introducir los materiales a partir de diversos experimentos que se pudieran realizar con facilidad en las aulas. En este contexto se eligió como tema “Aplicaciones de los cristales líquidos”. La estructura de la escuela ha constado de dos fases. En una primera sesión presencial, investigadores explicaron a los profesores participantes los fundamentos necesarios para comprender cómo funcionan las diversas aplicaciones. En una segunda fase, los propios profesores han trabajado en grupo para elaborar diversos materiales didácticos. Algunas empresas que comercializan productos basados en cristales líquidos han aportado materiales para ser utilizados en las aulas.Peer reviewe