Synthesis and characterization of SnO-containing phosphorous oxynitride glasses

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Viscoelastic analysis of RFDA measurements applied to oxide glasses

International audienceThe Resonance Frequency and Damping Analysis (RFDA) is now a common experimental technique to measure the elastic moduli of materials vs. temperature. Nevertheless, the elastic moduli are calculated assuming that the frequency measured is the natural one, not impacted by any damping. In oxide glasses, a significant damping occurs below the glass transition temperature, and it may impact the frequency measured, the elastic moduli calculated, as well as the estimated glass transition temperature. We show here, using the equations of linear viscoelasticity, how we can know if the frequency measured is significantly lowered by damping, and how we can estimate the natural frequency to calculate the correct elastic moduli, only from the data provided by the RFDA the frequency measured and the damping. © 2020 Elsevier B.V

Analysis of in vitro reaction layers formed on 48S4 glass for applications in biomaterial field

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Mechanical strength improvement of a soda-lime-silica glass by thermal treatment under flowing gas

International audienceThe incidence of thermal treatments in air, N-2 or NH3, on the mechanical properties of a soda-lime silica glass is presented. The effects of the treatment time and temperature were studied. Ammonia treatments lead to the most important compositional changes near the surface: SIMS and XPS techniques revealed a significant depletion in alkali and alkaline earth cations and a limited incorporation of nitrogen. IR-reflexion spectroscopy provided evidence for compositional changes near the surface, from a typical soda-lime glass towards a silica glass composition. The affected surface layer is typically about 1 mum deep and leads to significant changes of the local mechanical properties. Nanoindentation measurements showed that hardness increases whereas Young's modulus decreases both by similar to10% in a 300 nm thick surface layer. A significant increase of the indentation fracture toughness (K-c) from 0.72 to 0.89 MPa.m(1/2) was also noticed. The different processes leading to the cationic migration and to the changes of the glass surface properties were discussed. (C) 2003 Elsevier Ltd. All rights reserved

Crystallization pathways and some properties of lithium disilicate oxynitride glasses

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Specific trends in phosphate glass crystallization

International audienceThis paper focusses on investigating and comparing the congruent crystallization of phosphate glasses with different degrees of polymerization. The study was performed both on powders, with different size fractions, and coarse particles which can be assimilated to bulk. From DSC experiments, corroborated by SEM analysis, it was demonstrated that LiPO3 crystallizes from surface whereas LiGe2(PO4)3 crystallizes in the whole volume. Sn2P2O7 presented both phenomena, the nucleation time lag being short enough to observe internal crystallization at the laboratory time scale. Using the non-isothermal Ozawa method, the kinetic parameters of the overall devitrification process were determined in terms of the Avrami exponent and of the activation energy for crystallization. The temperature of the maximum nucleation rate was calculated by using the nucleation adiabatic theory. For the achievement of this calculation, the heat capacity temperature dependence up to melting was determined from DSC experiments. The results were found in a good agreement with the SEM observation and the results of the non-isothermal crystallization study. © 2020 Elsevier B.V