Reactive Vaporization of Soda-Lime-Silica Glass Melts

Water-vapor-assisted transport of glass constituents from a soda-lime-silica melt was studied, using atomic spectroscopy for analysis of vapor condensates and microprobe analysis to determine diffusion profiles. The data presented indicate that the vaporization process is controlled by a surface membrane which has a composition different from the bulk composition. The influence of this effect on glass homogeneity is discussed.     

Aqueous Corrosion of Soda-Silica and Soda-Lime-Silica Glass

Corrosion of a 20Na2O-10CaO-70SiO₂ (mol%) glass by water was investigated using ir reflection spectroscopy, solution analysis, electron microprobe, and Auger electron spectroscopy. Corrosion proceeds at a much slower rate in the ternary glass than in a 20Na2O-80SiO2 glass. Within the Na-depleted layer of the ternary glass, a Ca-enriched zone develops—1500 A from the surface. The role of CaO in both the early and later stages of corrosion is discussed.     

Subcritical Growth of Indentation Median Cracks in Soda-Lime-Silica Glass

The influence of load and dwell time on the subcritical growth of indentation cracks was investigated. The behavior of soda-lime-silica glass in both active and inert environments was considered. Vickers indentations were obtained.using loads ranging from 1.96 to 39.2 N and the dwell time.at maximum load was varied between 5 s and 30 min. Indented samples were broken and the fracture surfaces.observed using optical microscopy. Anomalous crack shapes were obtained in air and water for long dwell times, particularly at higher indentation loads. The cracks were markedly circular in shape and substantially deeper than conventional median/radial indentation cracks, evidencing a time-dependent growth. Comparison of the measured crack depth with a theoretical analysis demonstrated that the appearance of the "circular" cracks was related to the subcritical growth of median cracks.     

Strength Degradation of Soda-Lime-Silica Glass During Dynamic Loading

The strength degradation of soda-lime-silica glass during dynamic loading was studied by using a fracture-mechanics approach. The theoretical and experimental results indicate that subcritical flaw growth during loading causes the strength degradation.     

Methanol Vapor Adsorption on Silica and Soda-Lime-Silica Glass

Methanol vapor adsorption isotherms on vitreous silica and soda-lime-silica glasses were measured by gas chromatography in the low-pressure region of the physical adsorption isotherms after the adsorbents had been degassed in a dry atmosphere at successively higher temperatures. The isosteric heats of adsorption indicate that after strong degassing treatments each methanol molecule is adsorbed by the formation of a single hydrogen bond with the surface, but after low-temperature degassing more than one hydrogen bond is formed for each adsorbed molecule.     

SIMS Analysis of Aqueous Corrosion Profiles in Soda-Lime-Silica Glass

In secondary ion mass spectrometry (SIMS) of glasses compensation of surface charging is necessary to avoid migration of mobile ions. A charge-compensation method, involving a metal diaphragm placed on the sample surface and a rastered primary ion beam, was tested on aqueous corrosion profiles in 20Na₂O·10CaO·700SiO₂ (mol%) glass. The method was effective with both O⁻ and O₂⁺ primary ions.     

Development of Porous Antireflective Films on Soda-Lime-Silica Glass

Glass compositions were surveyed to identify candidates that could be heat-treated to produce an interconnected phase-separated structure needed for porous antireflective films and which matched the viscosity-temperature characteristics needed for the float glass process. A glass composition of 10% Na₂O,10% CaO, and 80% SiO₂ meets these criteria. Microstructural development and film-formation kinetics were characterized to permit definition of appropriate heat-treatment and selective dissolution processes. Broadband antireflective characteristics were developed on treated glass surfaces.     

Anelasticity of Glass: II, Internal Friction and Sodium Ion Diffusion in Tank Plate Glass, A Typical Soda-Lime-Silica Glass

The internal-friction peak observed near room temperature in tank plate glass at a period of the order of seconds and previously attributed to sodium ion diffusion is further discussed. The temperature of maximum internal friction is shown to vary with the frequency of vibration with an activation energy of about 16 kg.-cal. Per mole for air-chilled glass fibers. Likewise, the activation energy for the electrical resistivity of the chilled glass is about 16 kg.-cal. Although the activation energy for sodium ion diffusion and alkali durability is about 21 kg.-cal., it too can be properly interpreted to confirm that the internal friction peak is caused by sodium ion diffusion. The internal friction peak is much broader than can be accounted for by a single relaxation mechanism. However, a dispersion of relaxation mechanisms is consistent with the accepted theory of randomness in the silica network.     

Effect of Deuterium Oxide on Crack Growth in Soda-Lime-Silica Glass

Crack growth in acidic and basic deuterium oxide solutions was studied. An isotopic effect was observed in basic deuterium oxide solutions but not in acidic deuterium oxide solutions. The results suggest that the rate-limiting step for crack growth difsers for basic and acidic environments.     

Detection of Reaction Products Between Water and Soda-Lime-Silica Glass

A simulated extract approach was used to ascertain the identities of the products of reaction between a soda-lime-silica glass and water. The reaction between the glass and water was studied at 90° C. with reaction time periods up to 4 hours. The products of this reaction were found to be sodium metasilicate, calcium meta-silicate, and metasilicic acid.     

Temperature Dependence of the High-Frequency Viscoelastic Behavior of a Soda-Lime-Silica Glass

The high-frequency viscoelastic behavior of a soda-lime-silica glass has been investigated using the Brillouin scattering technique. The temperature dependence of instantaneous elastic constants and very short-time relaxation mechanisms have been measured in a temperature range between 100° and 1000°C. Variations in the elastic constants in the transition region are significant, and have to be taken into account for numerical computations of tempering and annealing of glasses. A complex thermorheological behavior is observed for very fast relaxation mechanisms in the transition range, whereas intermediate and slow relaxation mechanisms exhibit a simple thermorheological behavior. The viscoelastic behavior of this glass can be adequately represented by assuming a different thermorheological behavior in the alpha- and β-relaxation regimes.     

Novel Combined Scratch and Nanoindentation Experiments on Soda-Lime-Silica Glass

Many advanced applications of glass demand fabrication of engineering parts of utmost dimensional precision which require very accurate grinding and polishing that involves controlled removal of glass. Despite the wealth of literature, however; the mechanism of material removal in glass grinding and polishing is still far from well understood. For instance, it is not known at all to what extent the mechanical properties are compromised inside a scratch groove so as to optimize the machining parameters. Therefore, to develop better understanding about the mechanism of material removal, a series of combined nanoindentation and single pass scratch experiments were conducted on a commercially available soda-lime-silica glass as a function of various normal loads (2–20 N) and scratch speeds (0.1–1 mm/s). It was found that the nanohardness and Young's modulus at the local microstructural length scale inside the scratch groove could decrease quite dramatically (~30% to 70%) depending on the combination of load and scratching speed. Further, the tribological properties, the severity and the spatial density of damage evolution were sensitive to the normal loads, scratching speeds, and tensile stresses. Extensive scanning electron microscopy leads to interesting observations on material removal mechanisms. These observations were explained by the theoretical predictions of a model for a brittle, microcracked solid.     

Effect of Heating Time on the Thermal Stress Resistance of a Soda-Lime-Silica Glass

A model study was conducted of the thermal fatigue and single-cycle thermal shock resistance of indented soda-lime-glass rods heated over durations sufficiently short that thermal equilibrium was not reached prior to quenching into a water bath. The experimental results indicate that for short heating periods thermal fatigue life at fixed ΔT and the critical quenching temperature difference (Δ7_c) for a single-cycle quench significantly exceed the corresponding values obtained for specimens heated for sufficiently long periods that conditions of final thermal equilibrium were obtained prior to quenching. The implications of these results for single-cycle and multicycle thermal shock testing are discussed.