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(107) Production(s) de FORET M.
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Rare gases adsorption in silica glass at high pressure 
Auteur(s): Foret M. , Weigel C., Ruffle B., Polian Alain, Coasne Benoit, Vacher R.
Conférence invité: Workshop on gases and bubbles in molten glasses: from chemical engineering to geosciences (Paris, FR, 2016-05-13)
Ref HAL: hal-01940780_v1
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Résumé: We investigate vitreous silica pressurized under the noble gases, He, Ne and Ar by both spectroscopic techniques and numerical simulations. We find an unexpectedhuge solubility of He and Ne at high pressure together with a large decrease of the static compressibility. We show that this relates to the open and flexible structure of the glass allowing gas atoms to distend the network, the same way a porous material deform upon fluid adsorption. This behavior can be rationalized using generalized poromechanical constitutive equations. Direct optical microscopy observations highlight the swelling of the silica network upon fluid adsorption. Very sharp diffusion front of the fluid into the silica the sample is further observed indicating non trivial kinetics of the diffusing atoms. In the Ne case, adsorption-desorption kinetics canbe tracked by Brillouin spectroscopy.
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Raman spectroscopy of vitreous silica under rare gas compression
Auteur(s): Weigel C., Foret M., Hehlen B., Polian Alain, Vacher R., Ruffle B.
Conference: 3d Glass summit (Wuhan, CN, 2016-04-04)
Ref HAL: hal-01937850_v1
Exporter : BibTex | endNote
Résumé: We present accurate measurement of the VV- and VH-polarized Raman spectra of vitreous SiO2 pressurized in the range 0 – 8 GPa in argon or helium atmosphere by means of diamond anvil cell. A fine quantitative analysis of the behavior of the Raman modes in function of pressure is achieved with the help of an old central-force model by Sen and Thorpe describing the dynamics of covalently bonded networks. The model predicts the effect of changes in force constants and bond angles on the vibrational frequencies of the coupled SiO4 tetrahedral network. We show that the pressure shift of the Raman bands cannot be understood without encompassing the variations of both parameters. Investigating two different pressurizing fluids including He which is adsorbed into the silica network, allows revealing the role of each parameter in the compression mechanism of the glass.
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Polarized Raman spectroscopy of v-SiO2 under rare gas compression
Auteur(s): Weigel C., Foret M.
Conference: 54th European High Pressure Research Group Meeting (EHPRG 2016) (Bayreuth, DE, 2016-09-05)
Ref HAL: hal-01909031_v1
Exporter : BibTex | endNote
Résumé: High-pressure polarized Raman spectra of vitreous silica are measured up to 8 GPa in a diamond-anvil cell at room temperature. The combined use of either a nonpenetrating pressurizing medium—argon—or a penetrating one—helium, allows one to separate density from stress effects on the Raman frequencies. In the framework of a simple central force model, the results emphasize the distinct role played by the shrinkage of the intertetrahedral angle Si-O-Si and the force-constant stiffening during the compression. The polarization analysis further reveals the existence of an additional isotropic component in the high-frequency wing of the boson peak. The pressure dependence of the genuine boson peak frequency is found to be much weaker than previously reported and even goes through a minimum around 2 GPa in remarkable coincidence with the anomalous compressibility maximum of silica.
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Elasticity of vitreous silica under fluid pressure
Auteur(s): Weigel C., Foret M., Kint M., Vacher R., Ruffle B., Polian Alain, Rouquette Jérome, Haines Julien, Coasne Benoit
Conference: Glass & Optical Materials Division Annual Meeting 2016 (Madison (WI), US, 2016-05-26)
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