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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

Chalcogenide Glass Optical Waveguides for Infrared Biosensing

Due to the remarkable properties of chalcogenide (Chg) glasses, Chg optical waveguides should play a significant role in the development of optical biosensors. This paper describes the fabrication and properties of chalcogenide fibres and planar waveguides. Using optical fibre transparent in the mid-infrared spectral range we have developed a biosensor that can collect information on whole metabolism alterations, rapidly and in situ. Thanks to this sensor it is possible to collect infrared spectra by remote spectroscopy, by simple contact with the sample. In this way, we tried to determine spectral modifications due, on the one hand, to cerebral metabolism alterations caused by a transient focal ischemia in the rat brain and, in the other hand, starvation in the mouse liver. We also applied a microdialysis method, a well known technique for in vivo brain metabolism studies, as reference. In the field of integrated microsensors, reactive ion etching was used to pattern rib waveguides between 2 and 300 μm wide. This technique was used to fabricate Y optical junctions for optical interconnections on chalcogenide amorphous films, which can potentially increase the sensitivity and stability of an optical micro-sensor. The first tests were also carried out to functionalise the Chg planar waveguides with the aim of using them as (bio)sensors

Fluorescence in erbium doped gallium lanthanum sulphide: potential for mid-IR waveguide laser

Fluorescence is reported in waveguides fabricated via the ultrafast laser inscription technique in Erbium doped Gallium Lanthanum Sulphide (Er3+:GLS) for mid-infrared laser applications. The pump wavelength was 980nm leading to mid-infrared transition at 2.75 µm

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