Search for: All records

Glass properties are governed by the interplay between network formers and network modifiers; for a given composition of network formers, the ratio of different cationic modifiers compensating the anionic species in the network has a profound effect, which is often nonlinear, called a mixed modifier effect (MME). We have investigated the MME of sodium (Na) and calcium (Ca) in an aluminosilicate (NCAS) glass series following the formula [Na₂O]_30−x[CaO]_x[Al₂O₃]₁₀[SiO₂]₆₀, wherex = 0, 7.5, 15, 22.5, and 30. A nonadditive trend was observed in hardness and indentation toughness, with aqueous corrosion resistance exhibiting a shift from incongruent to congruent corrosion, whereas the network structure determined by molecular dynamics simulations revealed no significant trend with composition. Additionally, the NCAS glass containing both [Na₂O] and [CaO] within an intermediate range exhibited superior resistance to wear at high humidity, a clear MME phenomenon previously only observed in soda–lime silica.

As a means to elucidate the mechanical stress effect on the durability of soda lime silicate (SLS) float glass, a thin glass plate under flexural stress was investigated with X‐ray photoelectron spectroscopy (XPS), specular reflectance infrared (SR‐IR) spectroscopy, nanoindentation, and tribo‐testing. A lab‐built four‐point bending rig was employed to create compressive or tensile stress (around 40 MPa) on the air‐side surface of SLS glass. XPS analysis showed that electric field‐induced sodium ion migration is greatly enhanced in both compressive and tensile stress surfaces. The SR‐IR analysis of the Si‐O‐Si stretch mode revealed that the structural distortion of the silicate network appears to be larger under compressive stress than tensile stress. The elastic and plastic responses of the SLS surface to nanoindentation were significantly altered under the flexural stress conditions even though the magnitude of the flexural stress was less than 0.7% of the applied indentation stress. Compared to the stress‐free surface, the resistance to mechanochemical wear at 90% relative humidity deteriorated under the compressive stress condition, while it just became more scattered under the tensile stress condition. Even though the applied flexural stress was very small, its impact on chemical and structural properties could be surprisingly large. Combining all results in this study and previously published works suggested that the changes observed in nanoindentation and mechanochemical wear behaviors may be associated with the strain in the Si‐O bonds of the silicate network.

The polishing of oxide glass in aqueous solution is sensitive to not only the mechanical conditions applied by abrasives but also the chemistry of solution. This study elucidates the synergistic interactions of mechanical and chemical effects—especially, the synergetic effects of surface mechanochemical wear and subsurface dissolution are studied by measuring the material removal rate of soda lime silica (SLS) glass upon rubbing with a Pyrex glass ball in noncorrosive (neutral pH) in corrosive solutions (pH 10 and 13 NaOH) as a function of sliding speed. Based on the synergetic model of surface wear and subsurface dissolution, it is found that the mechanochemical surface reaction dominates the wear behavior of SLS glass in neutral and pH 10 solution conditions; the wear of SLS glass in pH 10 is enhanced, compared to the neutral pH case, due to the presence of OH^‐ions at the sliding interface. In the case of pH 13, the dissolution of the densified subsurface region, which is formed due to interfacial friction during the surface wear, becomes significant, further enhancing the material removal yield. The finding provides an insight for designing an efficient polishing process in manufacturing of oxide glass materials with a good surface finish.