Characterization of the glass transition in vitreous silica by temperature scanning small-angle X-ray scattering

The temperature dependence of the x-ray scattering in the region below the first sharp diffraction peak was measured for silica glasses with low and high OH content (GE-124 and Corning 7980). Data were obtained upon scanning the temperature at 10, 40 and 80 K/min between 400 K and 1820 K. The measurements resolve, for the first time, the hysteresis between heating and cooling through the glass transition for silica glass, and the data have a better signal to noise ratio than previous light scattering and differential thermal analysis data. For the glass with the higher hydroxyl concentration the glass transition is broader and at a lower temperature. Fits of the data to the Adam-Gibbs-Fulcher equation provide updated kinetic parameters for this very strong glass. The temperature derivative of the observed X-ray scattering matches that of light scattering to within 14%.Comment: EurophysicsLetters, in pres

Deactivation of Pressure-Induced Amorphization in Silicalite SiO2 by Insertion of Guest Species

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Flexibility windows and compression of monoclinic and orthorhombic silicalites

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Organisation structurale locale dans des composes CdS_xSe_1_-_x massifs ou inclus dans une matrice vitreuse

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 79935 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Acoustic properties of Vycor porous glass at hypersonic frequencies

Brillouin scattering experiments have been performed from 5 to 1600 K in vycor, a porous silica glass. The acoustic velocity and attenuation at hypersonic frequencies are compared to those of bulk silica and others porous silica samples. The experimental evidence for the influence of porosity on the scattering by acoustic waves is compared to calculations. The correlation between internal friction and thermal conductivity at low temperature is discussed

Étude par dynamique moléculaire et diffusion multiple de verres d'intérêt géologique

PARIS-EST Marne-la-Vallee-BU (774682101) / SudocSudocFranceF

Mesure de tension de surface en température : application au cas verres de confinement des déchets nucléaires

poste

Structural Change in Li and Na Aluminophosphate Glasses : Evidence of a "Structural Mixed Alkali Effet"

The short- and long-range structure of a series of single and mixed aluminophosphate glasses with the general composition [xNa(2)O (46-x)Li2O], [y,Al2O3 (54 -y)P2O5] is analyzed using P-31 and Al-21 magic-angle spinning (MAS) NMR as well as small-angle X-ray scattering. These series of glasses allow analyzing both the effect of alumina incorporation in these glasses, for small alumina content (y = 0, 4, 8). and the structural changes associated with the so-called mixed alkali effect (,v = 0, 11.5, 23, 34.5, 46). Our results indicate that aluminum is mainly octalledrally coordinated in these glasses and that there is most likely some segregation of the Al(OP)(6) species. In the pure phosphate glasses, we observe a "classical" continuous variation of the structural properties with the relative alkali content, but in the aluminophosphate, both local and long-range structural results reveal for the first time some nonlinear change as a function of the relative alkali content