Elastic properties and surface damage resistance of nitrogen-rich (Ca,Sr)-Si-O-N glasses

International audienceCa and Sr-based oxynitride glasses with very high nitrogen content have been synthesized using metal hydrides as primary precursors. Values of Young's modulus, shear modulus, bulk modulus and Poisson's ratio were determined by means of ultrasonic echography. Vickers micro-indentation has been used to characterize hardness and indentation fracture toughness behaviour. Elastic moduli were found to increase linearly with nitrogen content, with the highest value of Young's modulus at 135 GPa, for a Ca-glass with 58 e/o of nitrogen. The Sr-glasses exhibit lower elastic moduli than Ca glasses. Poisson's ratio, hardness, indentation fracture toughness, crack initiation load and surface damage resistance were found to increase with increasing nitrogen content for both glass series. (C) 2010 Elsevier B.V. All rights reserved

Evidence and modeling of mechanoluminescence in a transparent glass particulate composite

International audienceMechanoluminescence (ML) of a transparent alkali-phosphate glass composite with SrAl2O4:Eu, Dy particles is reported. Uniaxial compression experiments show the linear dependence of the mechanoluminescence intensity with the mechanical power. A theoretical model, based on the physics of delayed processes (in analogy of viscoelasticity), is proposed. This model accurately predicts the ML intensity changes induced by a complex mechanical loading and provides a convincing description of the mechanoluminescence response

Direct observation of the displacement field and microcracking in a glass by means of X-ray tomography during in situ Vickers indentation experiment

International audienceThe actual displacement field in a glass during an in-situ Vickers indentation experiment was determined by means of X-ray tomography, thanks to the addition of 4 vol % of X-ray absorbing particles, which acted as a speckle to further proceed through digital volume correlation. This displacement was found to agree well with the occurrence of densification beneath the contact area. The intensity of the densification contribution (Blister field proposed by Yoffe) was characterized and provides evidence for the significant contribution of densification to the mechanical fields. Densification accounts for 27% of the volume of the imprint for the studied glass, that is expected to be less sensitive to densification than amorphous silica or window glass. A major consequence is that indentation cracking methods for the evaluation of the fracture toughness, when they are based on volume conservation, as in the case of Hill-Eshelby plastic inclusion theory, are not suitable to glass. The onset for the formation of the subsurface lateral crack was also detected. The corresponding stress is z 14 GPa and is in agreement with the intrinsic glass strength

The development of advanced optical fibers for long-​wave infrared transmission

International audienceLong-​wave IR fibers are used in an increasing no. of applications ranging from thermal imaging to bio-​sensing. However, the design of optical fiber with low-​loss in the far-​IR requires a combination of properties including good rheol. characteristics for fiber drawing and low phonon energy for wide optical transparency, which are often mutually exclusive and can only be achieved through fine materials engineering. This paper presents strategies for obtaining low loss fibers in the far-​IR based on telluride glasses. The compn. of the glasses is systematically investigated to obtained fibers with minimal losses. The fiber attenuation is shown to depend strongly on extrinsic impurity but also on intrinsic charge carrier populations in these low band-​gap amorphous semiconductor materials

Linear and Nonlinear Characterizations of Chalcogenide Photonic Crystal Fibers

International audienceIn this paper, we investigate the linear and nonlinear properties of GeSbS and AsSe chalcogenide photonic crystal fibers. Through several experimental setups, we have measured the second- and third-order chromatic dispersion, the effective area, losses, birefringence, the nonlinear Kerr coefficient as well as Brillouin and Raman scattering properties

Spectroscopie de nouveaux verres d'oxyfluorures dopés Er3+. Réalisation de fibres optiques en verres IR : Monomodes et fortement non linéaires à 1,55 micromètres Pour détection d'exo-planètes entre 4 et 20 micromètres (projet Darwin)

Cette thèse se compose de trois parties qui correspondent chacune à létude d'un verre différent avec des applications potentielles différentes.Dans la première partie, nous nous sommes intéressés à une nouvelle matrice vitreuse d'oxyfluorures dérivée des fluorophosphates, les verres de fluoroarsenates. Nous avons étudié les caractéristiques physiques, optiques et structurales de ces verres. Cette matrice a la particularité d'accepter un fort pourcentage d'ions terre rares. Elle est ici dopée avec l'ion erbium pour effectuer une analyse spectroscopique de cet ion dans cette nouvelle matrice.Dans la deuxième partie, nous avons utilisé le verre de chalcogènures GeSe4. Le but de cette étude est de mesurer la non linéarité de ce verre sur une fibre optique à 1,55 æm. Cette mesure passe par la réalisation d'une fibre monomode à 1,55 æm. Une nouvelle technique permettant lélaboration de fibres monomodes en deux étapes de fibrage a été mise au point. Pour finir, un indice de réfraction non linéaire 100 fois supérieur à celui de la silice a été mesuré sur cette fibre monomode.La troisième partie concerne un autre verre de chalcogénure composé de tellure, d'arsenic et de sélénium et nommé plus communément verre TAS. Cette partie est basée sur le projet Darwin qui a pour objectif de détecter des planètes hors du système solaire. Ce projet nécessite un filtre interférométrique opérant entre 4 et 20 æm. La fenêtre de transmission du verre TAS sétend de 2 à 20 æm, il apparaît donc comme un candidat potentiel. Enfin, nous avons procédé à la réalisation de cette fibre monomode, en utilisant une nouvelle technique de fabrication de préforme, double indice sous vide, brevetée par le laboratoire Verres et Céramiques.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Review: Elaboration, structure, and mechanical properties of oxynitride glasses

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Mechanoluminescence of (Eu, Ho)-doped oxynitride glass-ceramics from the BaO-SiO2-Si3N4 chemical system

International audienceMechanoluminescence is observed in oxynitride glass-ceramics from the BaO-SiO2-Si3N4 chemical system, doped with Eu and Ho. Light emission was investigated by means of uniaxial compression experiments on disks and parallelepipedic bars with constant loading rates ranging from 0.3 to 300 MPa s(-1) up to about 500 MPa. In agreement with previous reports on SrAl2O4-based materials [Dubernet et al., Appl. Phys. Lett. 107, 151906 (2015) and Dubernet et al., Sci. Rep. 10, 19495 (2020)], the mechanoluminescence intensity is found proportional to the mechanical power. Nevertheless, in contrast with SrAl2O4, no gain in the intensity is observed at the onset of the unloading stage, but a drop of the photoluminescence intensity during unloading. This stems from different electron trapping populations and associated energy levels for the Ba4Si6O16 phase (the dominant crystallized phase in the present glass-ceramics), which are discussed in light of density functional theory calculations

Synthesis and mechanical characterization of glasses and glass-ceramics along the 0.3 BaO – x TiO2 - (0.7-x) SiO2 composition line x [0;0.3]

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Healing of cracks by green laser irradiation in a nanogold particles glass matrix composite

International audienceA transparent composite material consisting of a soda-lime-silicate glass matrix containing up to 0.5 %w gold nanoparticles (10 to 20 nm) was successfully obtained by coating glass grains and a subsequent sintering using a spark plasma sintering (SPS) furnace. Coating was achieved thanks to the reduction of gold(III) chloride trihydrate by sodium borohydride in an ethanol solution. The sintered composites were dense and transparent, but for the largest gold content where the sample exhibits a deep red color. When submitted to laser irradiation (532 nm, up to 100 W/cm2), the composite experiences a fast, localized and much more significant increase of its temperature in comparison with the pristine glass material. A temperature as high as 550 °C was reached, allowing the healing of surface crack