Synergy between surface mechanochemistry and subsurface dissolution on wear of soda lime silica glass in basic solution

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.     

Differences in surface failure modes of soda lime silica glass under normal indentation versus tangential shear: A comparative study on Na+/K+-ion exchange effects

The effects of exchanging Na⁺ with K⁺ on the mechanical and mechanochemical properties of a soda lime silica (SLS) glass were investigated. It is known that replacing smaller modifier ions with bigger ions in the silicate glass network, at temperatures below the glass transition (T_g), produces a compressive stress in the subsurface region that enhances resistance to mechanical damages. This study found that when Na⁺ ions in SLS are exchanged with K⁺ ions at 400°C, the hardness, indentation fracture toughness, and crack initiation load of the surface are increased, which is consistent with the chemical strengthening effect. However, the resistance to mechanochemical wear in a near-saturation humidity condition (relative humidity RH = 90%) is deteriorated. When K⁺ ions are exchanged back with Na⁺ ions at 350°C, the wear resistance in high humidity conditions is recovered. These results indicate that the improvement of mechanical properties under indentation normal to the surface is irrelevant with the resistance to mechanochemical wear under tangential shear at the surface. Based on the analysis of the surface chemical composition, silicate network structure, and hydrogen-bonding interactions of hydrous species in the subsurface region, it is proposed that the leachable Na⁺ associated with non-bridging oxygen and subsurface hydrous species in the silicate network play more important roles in the mechanochemical wear of SLS at high RH.     

Effect of humidity on friction,wear, and plastic deformation during nanoscratch of soda lime silica glass

Physical flaws and defects on glass surfaces are known to reduce the mechanical strength and chemical durability of glass. The formation of surface defects depends not only on the mechanical conditions of the physical contact but also on the environment in which the contact is made. In this study, the nanoscratch behavior of soda lime silica (SLS) glass was investigated in 10% and 60% relative humidity (RH) conditions. Based on the evolution of friction and scratch depth, the deformation of SLS glass surface could be divided into four regimes: elastic deformation and recovery (E), RH-independent mild plastic deformation (P-1), RH-dependent intermediate plastic deformation (P-2), and RH-independent severe plastic formation (P-3). It is quite surprising to observe that plastic deformation of the glass surface has dependence on RH of the environment (outside the glass) because plastic deformation is the process occurring below the surface (inside the glass) by the externally applied load. From this result, it can be inferred that frictional energy dissipation mode at the sliding interface, which is a function of adsorbed water molecules, influences the subsurface deformation mode. Although friction, wear, and subsurface deformation/damage are all coupled, there is no direct one-on-one correlation among them.     

Powder-fed directed energy deposition of soda lime silica glass on glass substrates

Novel glass processing by powder-fed directed energy deposition was explored as a method of adding glass décor to glass surfaces and bottles. Consistent, semitransparent, single-line tracks of soda lime silica glass could be processed onto glass substrates of the same composition, without significant cracks forming in the substrate. A suitable processing window was found with laser power and scan speed showing independent effects on processing. Consideration of processing surface conditions and reduction of laser transmission through transparent substrates was necessary, and the use of an adhesive tape layer aided adhesion of glass feedstock to substrate surfaces. The work demonstrates the potential for a one-step method of glass bottle decoration for the packaging industry, with scope to create 3D designs of high geometric complexity and customizability on glass substrates, thereby adding value to glass packaging by brand differentiation without the high costs associated with molds and tooling.     

Chemical structure and mechanical properties of soda lime silica glass surfaces treated by thermal poling in inert and reactive ambient gases

This study employed thermal poling at 200°C as a means to modify the surface mechanical properties of soda lime silica (SLS) glass. SLS float glass panels were allowed to react with molecules constituting ambient air (H₂O, O₂, N₂) while sodium ions were depleted from the surface region through diffusion into the bulk under an anodic potential. A sample poled in inert gas (Ar) was used for comparison. Systematic analyses of the chemical composition, thickness, silicate network, trapped molecular species, and hydrous species in the sodium‐depleted layers revealed correlations between subsurface structural changes and mechanical properties such as hardness, elastic modulus, and fracture toughness. A silica‐like structure was created in the inert gas environment through restructuring of Si–O–Si bonds at 200°C in the Na‐depleted zone; this occurred far below T_g. This silica‐like surface also showed enhancement of hardness comparable to that of pure silica glass. The anodic thermal poling condition was found so reactive that O₂ and N₂ species can be incorporated into the glass, which also alters the glass structure and mechanical properties. In the case of the anodic surfaces prepared in a humid environment, the glass showed an improved resistance against crack formation, which implies that abundant hydrous species incorporated during thermal poling could be beneficial to improve the toughness.     

Densification effects on the fracture in fused silica under Vickers indentation

This study investigates the effects of densification on the deformation and fracture in fused silica under Vickers indentation by both the finite element analysis (FEA) and experimental tests. A refined elliptical constitutive model was used, which enables us to investigate the effects of the evolution of yield stress under pure shear and elastic properties with densification. The densification distribution was predicted and compared with experiments. The plastic deformation and indentation stress fields were used to analyze the initiation and morphology of various crack types. The formation mechanism of borderline cracks was revealed for the first time. This study reveals that the asymmetry of the densification distribution and elastic-plastic boundary significantly influences the cracking behavior. Under the Vickers indentation, conical cracks have the largest penetration depth. When these cracks emerge from a region far from the impression, they extend with constant radii to form circles on the sample surface. Otherwise, they tend to be initiated at the centers of the indenter-material contact edges before propagating towards the impression corners with increasing radii. Therefore, the borderline cracks consisting of successive partial conical cracks can form at a low load and makes them the first type of crack to appear.     

Electric field-assisted ion exchange strengthening of borosilicate and soda lime silicate glass

In this study, we investigate the effects of electric field-assisted ion exchange (EF-IE) on potassium for sodium ion exchanges of soda borosilicate and soda lime silicate glasses. The results show that applying an electric field (E-field) with the intensity of 1000 V cm⁻¹ for few minutes produces an exchanged layer with a thickness comparable to the conventional chemical strengthening for 4 hours. There is a critical E-field that increases the mobility and, therefore, the diffusion coefficient of the potassium ions in the glasses. The increase is, perhaps, related to the evolution of the glass structure due to the penetration of potassium ions under an E-field. Vickers indentations showed that strong compression is generated in the glass by EF-IE; however, the bending strength improvement is limited because of the presence of large surface defects and the stress distribution inhomogeneity.     

Vickers crack extension and residual fracture strength of annealed and thermally tempered glass in water

The effect of water contact on the propagation of microscale surface cracks is investigated in two types of glass: annealed and tempered glass. Initial flaw is artificially created on the glass surface using a Vickers indenter, and is covered with a water droplet for 20 min. Micrographs of the flaw taken before and after water contact confirms the increase in crack length from around 61–103 μm for thermally tempered glass. After water dipping, the maximum length to which the crack growth is approximately 57 % smaller in the thermally tempered glass than in the annealed glass. Despite the severe effect of water contact on crack propagation, it is found that the fracture strength is not substantially altered by water dipping; even though the crack length is enlarged, the fracture strength of glass is similar, and in the case of tempered glass, its fracture strength is slightly changed within 7% due to the blunting of the crack tip by water or others.     

Effects of fictive temperature on the leaching of soda lime silica glass surfaces

The fictive temperature of glass characterizes the glass network structure and its thermal history, and thereby can influence ion and water transport in the glass surface. In this study, IR specular reflectance (SR), refractive index, and density measurements were used to characterize and confirm the effects of glass sample processing, especially the fictive temperature/thermal‐history variations. The subsequent acid leaching of these glasses created leached surface layers due to interdiffusion and reaction of hydrous species in the surface; the hydrogen depth profiles obtained with secondary ion mass spectrometry (SIMS) confirmed enhanced leaching with increasing fictive temperature. Attenuated total reflectance (ATR) in the mid‐ and near‐IR indicated increases in both SiOH and H₂O species with increasing fictive temperature. The relative intensities and shapes of the ATR peaks were found to vary between the samples suggesting that speciation of the hydrous reaction products (eg, strong and weakly hydrogen‐bonded OH) is also influenced by the original fictive temperature of the glass, but could not be quantitatively determined.     

Flexural stress effect on mechanical and mechanochemical properties of soda lime silicate glass surface

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.     

Correlations between residual stress and water diffusion in silica glass at low temperatures

Residual stress profiles in silica glass were measured after water diffusion treatment under 47.33 kPa (355 Torr) water vapor at 350°C and 650°C. Earlier, it was found that water solubility in silica glass exhibited peculiar time dependence: Solubility increased with time exceeding the normal water solubility expected from higher temperatures. Then, the water solubility decreased with time. It was hypothesized that the stress induced by water diffusion and its subsequent relaxation is responsible for the phenomenon. Residual surface stress generation in silica glass was found to correlate closely with surface hydroxyl concentration, systematically increasing until eventual surface stress relaxation results in stress decrease for treatments beyond 265 hours at 650°C. This observation validates previous theories of time dependent diffusivity in silica glass.     

玻璃纤维增强酚醛树脂复合材料摩擦磨损性能研究

对几种玻璃纤维织物增强酚醛树脂复合材料进行了双向滑动摩擦试验,考察织物结构和基体树脂对复合材料的摩擦磨损性能的影响。研究结果表明:通过添加自润滑颗粒可提高复合材料的摩擦磨损性能,其中石墨的耐摩擦磨损效果比聚四氟乙烯(PTFE)显著;织物结构对复合材料摩擦性能的影响,主要受控于织物的表面粗糙度和织物结构对复合材料树脂体积分数的影响。此外,复合材料存在一个较优的树脂体积分数范围,在此范围内,复合材料的摩擦磨损性能较为优异。     

Surface damage resistance and yielding of chemically strengthened silicate glasses: From normal indentation to scratch loading

We report on surface elasticity, plastic deformation and crack initiation of chemically strengthened soda-lime silicate and sodium aluminosilicate glasses during lateral indentation and scratch testing. Instrumented indentation using a normal indenter set-up corroborated previous findings on the effects of chemical strengthening on surface Young's modulus, hardness, and indentation cracking. Using lateral indentation in the elastic-plastic regime, we find a pronounced increase in the scratch hardness as a result of chemical strengthening, manifest in higher work of deformation required for creating the scratch groove. Thereby, the glass composition is found to play a stronger role than the absolute magnitude of surface compressive stress. Using a blunt conical stylus for instrumented scratch testing reveals three distinct modes of scratch-induced surface fracture, which occur during scratching or after unloading. Occasional micro-cracking caused by pre-existing surface flaws at low scratching load can be completely suppressed through chemical strengthening. The intrinsic defect resistance to microcracking is reduced as a result of ion stuffing, depending on the initial glass composition, whereas the resistance to abrasive yielding is enhanced by several hundred MPa.     

Spatial distribution of nucleated bubbles in molten glasses undergoing coalescence and growth

Two‐dimensional spatial distributions and growths of nucleated bubbles during the re‐melting of “float” glass samples are experimentally investigated. To follow the bubble population undergoing coalescence, the temporal behavior of the Voronoï tessellation built by the bubble positions are monitored. During coalescence, the Voronoï cell areas are fitted by a single‐parameter Gamma distribution. Numerical time simulation of population of bubbles undergoing coalescence shows an exponential increase in the parameter associated to the Gamma distribution with the fraction of coalesced bubbles in agreement with experimental observation. An initial density of nuclei is then estimated; direct observation would require an extremely high space resolution. The bubble number density is two orders of magnitude larger on the side which was in contact with tin bath than on the other side in contact with atmosphere. Moreover, bubbles grow faster on tin side. From a thermodynamic and mass transfer models, we prove that tin reduces the glass former liquid which leads to an increase in dissolved sulfur explaining the more abundant bubble population and the enhanced growth rate on tin side.     

Different hydrothermal corrosion results between two sides of sodalime float glass and the possible corrosion mechanism

Sodalime float (SF) glass is widely used in our societies and industries. Hydrothermal corrosion method is one of the effective ways to prepare a superhydrophobic glass, but there is still lack of knowledge about hydrothermal corrosion behavior and mechanism of SF glass. We have hydrothermally treated SF glass at 180 °C for different time, and tried to reveal the aqueous corrosion process of SF glass. We have characterized the morphologies and chemical compositions of samples, and found that (1) the two sides of SF glass have different corrosion resistances, and (2) a multilayer structural coating with a nanoflake layer (Mg-rich gel layer), a nanowire layer (Ca-rich gel layer), and a porous layer (etched layer) is formed on the air-side of SF glass. Based on the experimental results, we have proposed an aqueous corrosion mechanism of SF glass. The insights of the hydrothermal corrosion behaviors and mechanism provide helpful guidelines to glass surface structural control and functionalization.     

双组分水性木器涂料抗压痕问题的研究与探讨

提出了当前双组分水性木器涂料在家具生产或运输过程中存在的压痕问题,并介绍了压痕产生的外部环境,分析了压痕产生的原因,认为解决压痕问题的关键在于改变涂膜的内部结构。并在水性体系中引入了异氰酸酯—紫外光双重固化交联的方法,使问题得到较好的解决。     

Effect of heat treatment on the surface chemical structure of glass: Oxygen speciation from in situ XPS analysis

Compositional changes in unleached and acid‐leached soda‐lime silicate surfaces were tracked with in‐vacuo heating and X‐ray Photoelectron Spectroscopy. Surface oxygen speciation was determined using a stoichiometry‐based algorithm via elemental composition, instead of the typical O 1s peak‐fitting approach. Accurate surface hydroxyl quantification is shown to require dehydration at temperatures near 200°C. On the unleached surface, no change in surface hydroxyl density (~2.5 OH/nm²) is observed in the temperature range of 200°C‐500°C after the initial dehydration. However, repolymerization in the network (non‐bridging oxygen→bridging oxygen) is observed due to volatilization of sodium. The acid‐leached surface undergoes sodium out‐diffusion from the bulk at sub‐T_g temperatures with laterally resolved inhomogeneity and shows a reduction in the concentration of hydroxyls from 4.5 OH/nm² (200°C) to 3.2 OH/nm² (500°C) accompanied by an increase in bridging oxygen. These results suggest that when [OH] > 2.5~3/nm², vicinal OH undergo dehydroxylation with evolution of water, whereas when [OH] < 2.5/nm², most OHs are non‐interacting and isolated (at temperatures below T_g). Furthermore, at temperatures exceeding 300°C, sodium has enough thermal energy to desorb in vacuum and diffuse from the bulk (depending on the abundance & local structure).     

Effect of Al3+ on the spectroscopic properties of Eu2+- and Tb3+-Doped high silica glass

In this study, Eu²⁺/Al³⁺-, Eu²⁺/Tb³⁺-, and Eu²⁺/Tb³⁺/Al³⁺-doped high silica glasses were prepared, and the effect of Al³⁺ on the spectroscopic properties of Eu²⁺ and Tb³⁺ and the energy transfer of Eu²⁺→Tb³⁺ was investigated. The results revealed that the addition of Al³⁺ increased the luminescent intensity of the Eu²⁺-doped glass by approximately 400 times. An obvious Eu²⁺→Tb³⁺ energy transfer occurred in the Eu²⁺/Tb³⁺-doped high silica glass, whose transfer efficiency can reached 66.9%. However, the efficiency continuously decreased as the Al³⁺ concentration increased, and eventually, it dropped to 7.2%. These phenomena can be explained by the following: Al³⁺ not only disperses Eu²⁺ but also changes the field strength and symmetry of its neighboring environment, thus increasing its emission intensity. Moreover, Al³⁺ destroys the strong dipole–dipole interactions between Eu²⁺ and Tb³⁺ in high silica glass due to its dispersive ability, which inhibits the energy transfer of Eu²⁺→Tb³⁺. This indicates that a small amount of Al³⁺ can significantly modify the neighboring environment of Eu²⁺ and change its light-emitting characteristics, potentially yielding efficient blue and green phosphors excited by near-ultraviolet light for use in white light-emitting diodes.     

Effects of injection conditions on temperature and component distributions in a CVD furnace for large-size silica glass

Silica glass is a superior functional material due to its excellent thermophysical properties. With the increasing demand for large-size and high-purity silica glass, a novel chemical vapor deposition (CVD) furnace characterized by a crucible has been proposed, which requires a deep understanding of heat and mass transport characteristics inside for better control. Aimed at this, a comprehensive simulation model is developed in the paper. The model is well verified with the experimentally measured temperature and is then used to examine distributions of temperature and critical components in the furnace. Effects of the injection conditions are further investigated, among which the H₂–O₂ equivalence ratio and flow rate have a great influence on the temperature and components distributions, whereas the SiCl₄ flow rate mainly affects the SiO₂ distribution. An improved injection condition is put forward finally, which is much better than the reference case; the average for the temperature and SiO₂ concentration on the deposition surface is increased, respectively, by 23 K and 0.018 mol/m³, and sufficient homogeneity is maintained.