The degradation of oxide glasses in atmospheric conditions concerns a wide range research and technological applications. This includes sub-critical crack propagation of damage, which leads to the unexpected failure of a system. We have found this sub-critical crack propagation to depend on the chemical compositions in pristine SiO2-B2O3-Na2O ternary glass systems. The chemical compositions controls the mesoscale structure as revealed by a novel parameter coined the depolymerization index. This parameter reveals surprising trends with the stress corrosion cracking behavior in Region I. The presentation will focus on stress corrosion fracture damage and how it varies with chemical composition and the depolymerization index.
Characterizations of SiO2-B2O3-Na2O Amorphous Phase Separated Glasses
Amorphous phase separated glasses are known to be crush resistant, yet there how their structural properties are connected to their physical and mechanical properties is not understood. SiO2-B2O3-Na2O glasses are model glass today as Silica, Sodium oxide, and diboron trioxide are the principal components of many industrial glasses. This ternary system is known to undergo two-phase amorphous phase separation (APS) and is hypothesized to undergo three-phase APS. Herein, we will take a look at one SBN sample with APS, of which the composition falls in the supposed three-phase APS zone. Characterizations on the sample include a closer look at structural (degree of APS, RAMAN spectra…), physical (density, Young’s modulus, Poisson’s ratio…) and mechanical (Hardness) properties of the system in order to understand how they depend on APS in the SBN sample.
Sub-critical crack growth in hydrous silicate glasses
M.Sc. Tina Waurischk | Bundesanstalt für Materialforschung und -prüfung (BAM) | Germany
M.Sc. Robert Balzer | Leibniz University Hannover
M.Sc. Philipe Kiefer | Institute for Non-Metallic Materials, Clausthal University of Technology
Dr.-Ing. Stefan Reinsch | Bundesanstalt für Materialforschung und -prüfung (BAM)
Dr. rer. nat. Ralf Müller | Bundesanstalt für Materialforschung und -prüfung (BAM)
Prof. Harald Behrens | Leibniz University Hannover
Prof. Joachim Deubener | Institute for Non-Metallic Materials, Clausthal University of Technology
Environmental conditions are known to influence sub-critical crack growth (SCCG) that starts from microscopic flaws at the glass surface, leading to stress corrosion phenomena at the crack tip. The processes at the crack tip are complex and water has been identified as a key component governing SCCG at low crack velocities (region I). In particular, the influence of humidity accelerating crack propagation is well studied for dry industrial soda-lime silicate glasses (< 1000 ppm water). To shed light on this influence, the effect of water is mimicked by studying SCCG in water-bearing glasses. For this purpose, water-bearing silicate glasses of up to 8 wt% total water were synthesized in an internally heated pressure vessel at 0.5 GPa and compared to dry glasses. SCCG was measured using the double cantilever beam technique. For dry glasses, three trends in the crack growth velocity versus stress intensity, KI, curve were found. The slope in region I, limited by environmental corrosion, increases in the order soda-lime silicate < sodium borosilicate < barium calcium silicate < sodium zinc silicate < sodium aluminosilicate glass. The velocity range of region II, reflecting the transition between corrosion affected and inert crack growth (region III), varies within one order of magnitude among these glasses. The KI region of inert crack growth strongly scatters between 0.4 and 0.9 MPam1/2. For hydrous glasses, it is found that water strongly decreases Tg, form a new sub-Tg relaxation peak caused by molecular water, and makes the glasses more prone to SCCG. The observed trends will be discussed in terms of the effects of Youngs Modulus on strain energy release rate and energy dissipation related to glass relaxation phenomena.
Application of the model of associated solutions to the study of the structure and properties of Li2O-P2O5 glasses
PhD Rajesh Dagupati | Alexander Dubček University of Trenčín | Slovakia
Prof. Marek Liska | Alexander Dubček University of Trenčín | Slovakia
PhD Francisco Munoz | CSIC | Spain
Lithium phosphate glasses are important for their properties of ionic conduction, most particularly in the form of thin-films, when part of the oxygens are substituted by nitrogen, giving rise to the so-called LiPON solid electrolytes that have application in lithium batteries. The introduction of nitrogen in the phosphate composition improves their thermal and chemical properties and originates an increase of the ionic conductivity of the glasses, the last being explained through the decrease of the bridging to non-bridging oxygens ratio . More recently, several authors have studied the structure and properties of phosphorus oxynitride phases with adequate values of conductivity and that may help in explaining the behavior of the LiPON electrolytes through their structural characteristics. In this work, we will show the first results on the application of the model of associated solutions, previously used by Shakhmatkin&Vedishcheva in glasses , for the study of the structure and properties of the Li2O-P2O5 system. This will be useful for the analysis of the feasibility of its application in the prediction of the ionic conductivity of nitrogen containing phosphate electrolytes.
 N. Mascaraque et al., Solid State Ionics 233 (2013) 73.
 B.A. Shakhmatkin et al., J. Non-Cryst. Solids 293 (2001) 220.
Influence of Al addition on structure and mechanical properties of Borosilicate glass
M.Sc. Sebastian Bruns | Technische Universität Darmstadt | Germany
Dr. rer. nat. Tobias Uesbeck | FAU Erlangen | Germany
Dominik Weil | Technische Universität Darmstadt | Germany
Prof. Dominique de Ligny | FAU Erlangen | Germany
Prof. Karsten Durst | Technische Universität Darmstadt | Germany
It has been found that the fracture response of borosilicate glass can be influenced by changes in the network interconnectivity. In the NBS2 borosilicate glass (74SiO2-20.7B2O3-4.3Na2O-1Al2O3) there are two subnetworks present, i.e. a silicate and a borate one. Increasing cooling rates while processing were found to increase interconnectivity between both which in turn improves the glasses fracture response and is accompanied with an increasing densification ability.
In the present study the borosilicate glasses have been systematically modified by additions of up to 4% Al. The inherent glass structure is characterized using Brillouin and Raman spectroscopy. Mechanic properties are studied using nanoindentation were volume conservative shear flow as well as inelastic densification and cracking can be present. Raman spectroscopic investigations in the indent center were performed to examine shear and densification influences on the glasses cracking behavior supported by cohesive zone finite element modelling. Finally the inherent glass structure and its network interconnectivity is linked to the mechanic glass response.