Matériaux & Techniques Editorial - Matériaux désordonnés , verres et leur fonctionnalisation

International audienceDisordered materials, glasses and their functionalization. This Topical Issue presents articles which illustrate the diversity of the activities of research and development led on glasses in France, and reflects the way in which the GDR “Glass” and the Union for Glass Science and Technology (USTV)act to federate the scientific actions on glasses for the GDR and to insure the link between the academic and industrial communities.Ce numéro thématique présente des articles qui illustrent la diversité des activités de recherche et développement menées sur les verres en France , et refì etent bien l ' esprit avec lequel le GDR ((Verres)) et l ' Union pour la Science et la Technologie Verrì eres (USTV) agissent pour fédérer les actions scientifiques sur les verres pour le GDR et pour et assurer un lien entre les communautés académiques et industrielles

Le GDR-Verres et l’USTV : des réseaux pour la réflexion scientifique sur des problématiques verrières académiques et industrielles

International audienceLa communauté scientifique et industrielle du verre est extraordinairement riche en France. Des équipes scientifiques avec une renommée internationale et une R&D verrière industrielle française, très dynamique, ayant besoin d’échanges sur des domaines d’expertise. Le réseau animé par le GDR-Verres et l’USTV crée un lien entre les équipes de recherche fondamentale, celles plus appliquée ou technologiques, et le monde industriel

Structural interpretation of the modification of soda-lime-silica glass properties by P2O5

The influence of P2O5 addition on soda-lime-silica glass properties is discussed on the basis of a structural model. It involves two effects: Insertion of phosphate molecular complexes into the silicate network interstices, and increase in silicate network condensation. The latter results from the scavenging of sodium and calcium cations by P2O5. The properties considered in this paper are high-temperature viscosity and liquidus temperature. The P2O5 additions are in the 0.8 to 3.0 mol% range. The silica content of the glasses varies from 60 to 67 mol%, and the ratio CaO/(CaO+Na2O) from 0 to 0.85. Phosphate molecular complexes decrease the liquidus temperature and the high-temperature viscosity increasing the network condensation results in an increase in the viscosity, but its effect on the liquidus temperature depends on whether the glass composition lies on an upward or downward liquidus surface of the phase diagram

Dissolution of (50-x)Na₂O-xCaO-50P₂O₅ metaphosphate glasses in different saline Solutions: mechanism and kinetic control

The dissolution of (50-x)Na₂O-xCaO-50P₂O₅ metaphosphate glasses has been investigated at pH 3 in Solutions containing in Na⁺, Ca²⁺, Cl⁻, NO₃⁻ and (PO₃⁻)n ions. Whatever the conditions, a hydrated layer develops over a surface covered with etch pits. Na⁺ and Cl⁻ have no specific effect on the dissolution kinetics and mechanism. In Ca²⁺-containing Solutions, XPS, electrophoretic mobility and ³¹P NMR show that Na⁺ is exchanged for Ca²⁺ in the hydrated layer, resulting in a decreased dissolution rate. Polyphosphate anions, (PO₃⁻)n, act as complexing agent for Ca²⁺, and counterbalance its inhibiting effect on the dissolution rate

Structure-Property Correlation in Sodium Borophosphate Glasses Modified with Niobium Oxide

Bulk glasses of the series (100−x)[0.4Na2O-0.2Nb2O5-0.4P2O5]-xB2O3 with x = 0–48 mol% B2O3 were prepared by slow cooling in air. Their glass transition temperature increases within the range of 0–16 mol% B2O3, but further additions of B2O3 result in its decrease. Their structure was investigated by Raman, 11B, and 31P MAS NMR spectroscopy. The relative number of BO4 units decreases with increasing B2O3 content, while the number of BO3 units increases up to 59 % at x = 48. The upfield shift of a broad resonance peak in the 31P MAS NMR spectra is ascribed to an increasing connectedness of the structural network with increasing B2O3 content. A strong Raman band at 916–929 cm−1 shows the presence of NbO6 octahedra in the structural network of these glasses. With the B2O3 addition, a decrease in DC conductivity is observed, which is attributed to the decrease in the concentration of Na+ ions

Statistics of silicate units in binary glasses

In this paper, we derive a new model to determine the distribution of silicate units in binary glasses (or liquids). The model is based on statistical mechanics and assumes grand canonical ensemble of silicate units which exchange energy and network modifiers from the reservoir. This model complements experimental techniques, which measure short range order in glasses such as nuclear magnetic resonance (NMR) spectroscopy. The model has potential in calculating the amounts of liquid-liquid phase segregation and crystal nucleation, and it can be easily extended to more complicated compositions. The structural relaxation of the glass as probed by NMR spectroscopy is also reported, where the model could find its usefulness. Published by AIP Publishing

"Role liant des phosphates condenses dans les composites ceramique-metal: application au systeme alumine-nickel"

SIGLEINIST T 74719 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc