International Journal of Applied Glass Science最新文献

Infrared graded-index (GRIN) lenses are desirable for realizing miniaturization and lightweight of infrared imaging systems. Chalcogenide glasses have excellent infrared transparency, good rheological property, and large refractive index range, making them preferred materials for infrared GRIN lenses. In this work, aiming to find thermally matched chalcogenide compositions with high refractive index contrast for preparing GRIN glasses by the stacking diffusion approach, we investigated characteristic temperature, thermal expansion coefficient and refractive index of Ge-As-Se and Ge-As-Se-Te glasses, optimized the glass compositions, and evaluated the feasibility of preparing GRIN glass using the optimized chalcogenide glass powders. It is found that Ge₂₀As₂₀Se₂₀Te₄₀ and Ge₁₂As₂₂Se₆₆ glasses have similar softening temperature (247°C vs. 249°C), reasonably difference of thermal expansion coefficient (3.8 ppm/K), and large refractive index contrast (∼.48). The glass powders with composition xGe₂₀As₂₀Se₂₀Te₄₀-(1-x) Ge₁₂As₂₂Se₆₆ can be hot-pressed into glass disks with good transmittance at the same temperature and pressure. Graded refractive index profile is formed near the interface between the layers after the co-pressed glass is thermally treated. These results demonstrate the prospect of the compositions for preparing infrared GRIN glasses.

Glass sagging is a subsequent process to the CVD process used for large-size and high-purity silica glass synthesis. Physical phenomena taking place in this process are complicated which need an in-depth understanding for better control. In this paper, a comprehensive study is conducted for the sagging process using a level-set and enthalpy-porosity coupled model. With this model, the deforming behavior of glass ingot and evolution of OH uniformly distributed region are well predicted. Then, two performance indices (the effective yield rate and maximum extension radius of OH uniformly distributed region) are proposed based on different applications, and important factors, including geometrical parameters (the ingot initial length, crucible diameter and pedestal height) and operating parameter (the heater power allocation scheme), are explored for their effects on the two indices. The orthogonal test design method is adopted to further determine the collective effects of the four factors. According to the range analysis results, the initial ingot length has the greatest effect, while the crucible diameter has the least effect on the effective yield rate; and for the maximum extension radius, the crucible diameter becomes the major factor, while the pedestal height is the most insensitive factor. The corresponding optimal schemes are proposed for the two indices finally, which are believed to provide useful guidance for improving the sagging process.

The Gladstone–Dale relation is among one of the many formulae put forward in the 19th century to try and relate the index of refraction and density of a material. Compared to other relations of the time, the Gladstone–Dale relation is advantageous as it is relatively simple to use. It has been suggested that the Gladstone–Dale relation can be used as a reliable way to calculate the index of refraction for oxide glasses because of the additive nature of the relation, making it ideal for glass compositions. The reliability of the Gladstone–Dale relation with regards to its use in glass science has been explored. Various oxide glass systems that use different network formers, conditional network formers, modifying oxides, and dopants have been obtained from the literature to determine the reliability of the relation with regards to index-of-refraction calculations. The benefits and faults of the relation are discussed, and it was found that it is not universally applicable for all glass compositions.

Nucleation behaviors in glasses/supercooled liquids (SCLs) such as lithium disilicate Li₂O–2SiO₂, cordierite Mg₂Al₄Si₅O₁₈, fresnoite Ba₂TiSi₂O₈, and K₂O–Nb₂O₅–GeO₂/TeO₂ glasses were analyzed and discussed from the interfacial energy γ at SCL–nucleus interfaces and nanoscale composition fluctuations. Based on the fragility concept for SCLs and the intrinsic origin of γ, the magnitude order of γ(fragile SCL) < γ(strong SCL) was proposed to be a crucial guide for an understanding of high homogeneous nucleation rates and prominent nanocrystallization. The role of nucleating agent TiO₂/ZrO₂ in accelerating the nucleation rate in cordierite-based and β-spodumene-type Li₂O–Al₂O₃–SiO₂-based glasses was discussed from the new perspective of γ(homoepitaxial-like nucleation) < γ(heteroepitaxial-like nucleation). Ferroelectric nanocrystals such as Sr_xBa_1–xNb₂O₆ in borate glasses and fluoride nanocrystals such as CaF₂ are also well understood from the proposed guidelines. The present article provides a new perspective for nucleation in glasses/SCLs, contributing to the comprehensive composition design of new innovative glass-ceramics.

As glass batch is charged into an electric melter, a cold cap forms on the glass melt surface. Heat transfer to the cold cap from the molten glass below and the melter atmosphere above determines the melting rate. A mathematical model of the cold cap and the experimental kinetic data of the feed-to-glass conversion that were collected for several simulated low-activity and high-level waste melter feeds allowed us to develop relationships between the internal structure of the cold cap, its properties, its thickness, and the internal heat transfer. This contribution shows the distribution of major crystalline phases and the cumulative evolution of gases within the cold cap. It also examines the temperature, conversion degree, and heating rate the melter feed is experiencing during the passage through the cold cap and their effects on the cold-cap bottom temperature and morphology, which are important for the computational fluid dynamics simulations of melters.

Herein, the crystallization behavior of a Li₂O–Al₂O₃–SiO₂ (LAS) glass system with the addition of ZrO₂ and SnO₂ as nucleating agents was investigated using X-ray diffraction, differential scanning calorimetry, four-dimensional scanning transmission electron microscopy, and X-ray absorption fine-structure measurements. At lower heat-treatment temperatures, the addition of ZrO₂ and SnO₂ afforded a ZrSnO₄ solid solution (SS), whereas at higher heat-treatment temperatures, the ZrSnO₄ SS decomposed, affording tetragonal ZrO₂ and tetragonal SnO₂. LAS-based crystalline phases, such as β-quartz and β-spodumene phases SS, were formed after the formation of the ZrSnO₄ SS. ZrSnO₄ SS particles a few nanometers in size were present in contact with the β-quartz SS particles a few dozen nanometers in size. This suggests that the ZrSnO₄ SS served as a crystal nucleus for the β-quartz SS, promoting its growth.

Rendering transparent materials extreme wettability, for example, superhydrophobicity or superhydrophilicity, has received considerable attention during the past decades. While fabrication of superhydrophobic glass with high processing efficiency and low production cost has always been a challenge. In this work, a laser-based surface functionalization process that combines ultraviolet (UV) nanosecond laser texturing and silicone oil-assisted heat treatment was employed to render glass superhydrophobicity with high process throughput. The wettability transition is attributed to the combined effects of laser texturing that induces hierarchical surface micro/nanostructures and silicone oil-assisted heat treatment that alters surface chemistry and lowers surface energy. The surface transmittance of the laser-based surface functionalized glass samples in the visible spectrum was experimentally measured and analyzed. The laser-based surface functionalized glass sample also exhibited long-term stability in air, mechanical robustness and good self-cleaning property. More importantly, the developed process shows both high process efficiency and cost effectiveness and has potential for applications where superhydrophobic glass is required.

The influence of Al₂O₃ addition on the precipitation of NaYF₄ crystals in oxyfluoride glasses has been investigated through the thermal, structural, and optical characterization of the parent glasses and corresponding glass–ceramics (GCs). The high-resolution transmission electron microscopy analysis of the GC with 5 mol% of Al₂O₃ shows the presence of phase-separated droplets about 69 nm in size containing several NaYF₄ nanocrystals with the diameter of about 10–15 nm. Raman and magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy were used to examine the structural changes attributed to the addition of Al₂O₃. The ¹⁹F MAS-NMR analysis indicated that fluorine atoms are present in different chemical environments (Na–F, Na–Si–F, Na–Al–F, and NaYF₄). The increasing amount of Al₂O₃ reduces the crystallization of NaYF₄ phase due to the increased fraction of fluorine bound in Na–Al–F environments. The visible luminescence investigation of the glasses and GCs demonstrated that the intensity of Er³⁺ ions emission transitions in the GCs was higher than that of the parent glass. This difference was attributed to the presence of Er³⁺ ions bound in NaYF₄ crystalline phase. Further evidence that the Er³⁺ ions were present in NaYF₄ phase was provided by the fact that the excited level Er³⁺:⁴S_3/2 lifetime was increased in GCs as compared to parent glass.

The control of humidity between certain limits is essential to avoid the alteration of historical objects, such as unstable historical glasses. However, the usual limits can be altered due to the presence of volatile organic compounds. This work presents the results of the exposure of soda, potash, and mixed-alkali silicate glasses to neutral and acidic (formic) atmospheres with ∼30%, ∼70%, and ∼100% relative humidity. The hygroscopic capacity of the glass was analyzed by gravimetry, and the surface alteration was evaluated by infrared spectroscopy, optical microscopy, and ion chromatography. In all glasses, the alteration begins with alkali ions’ lixiviation followed by the silica network's hydrolytic attack. The results showed that soda and mixed-alkali silicate glasses exhibit similar behavior, while the potash-lime one experienced the fastest degradation due to its composition. Results also confirmed that high humidity increased the alteration rate causing a higher hygroscopicity and reactivity of glasses. Finally, acidic environments promoted the ion-exchange reaction at high humidity, accelerating the lixiviation of alkaline ions and promoting the diffusion of water into the glass network.

In France, high-activity level wastes resulting from nuclear fission are conditioned in a homogeneous sodium-aluminoborosilicate glass by high-temperature vitrification. The tolerance of even a small fraction of crystals could enable an increase in the waste loadings, in addition to promoting process flexibility. If the waste loading were to be increased in French nuclear glass, cerianite (CeO₂) crystals could precipitate. In this study, we investigated the cerianite crystallization in a simplified nuclear glass melt at different temperatures, Ce₂O₃ wt%, and shear conditions. Furthermore, the evolution of the viscosity along with cerianite precipitation was followed. It was found that Ce₂O₃ is highly soluble in the glass melt, as even for a Ce₂O₃ wt% as high as 10% wt, the cerianite fraction in dynamic conditions at 1100°C after 8 h of crystallization was less than 1% vol. In addition, shear strongly accelerates cerianite crystallization and a high Ce₂O₃ content can engender the precipitation of highly branched dendrites. The evolution of the cerianite fraction did not significantly affect the viscosity of the glass melt. Finally, unlike what has been observed in the well-known platinum group metal (PGM)-bearing melts, a glass melt containing .8 vol% of cerianite crystals remains Newtonian.