Glass Viscosity Research Articles

A New Approach Toward Extreme Thermal Stability of Femtosecond Laser Induced Modifications in Glasses

AbstractImprinting thermally stable transformations by femtosecond laser in glass would benefit the development of optical sensors dedicated to harsh environments including combustors, nuclear reactors, aircraft engines, or metal/ceramic manufacturing processes. While glass brings undeniable assets over refractory crystalline materials like shaping ability (e.g., optical fiber form), one key challenge is to prevent the erasure of induced transformations at high temperatures and for long periods. In this article, the role of glass composition and viscosity to achieve modifications stable at high temperatures is first reviewed, providing a comprehensive roadmap for engineers in optics and photonics. While silica appears to be the candidate of choice, it is revealed that binary aluminosilicates can compete and sometimes surpass it. The hypothesis is formulated and investigated that a hybrid glass‐crystalline nano‐structuring can imprint ultra‐stable modifications inside glass. Laser‐induced modifications in Al2O3‐SiO2 and ZrO2‐Al2O3‐SiO2 glasses reveal a partial crystallization, shaped into a lamellar structure and orientable with laser light polarization. These birefringent structures can withstand temperatures up to 1300 °C for 30 minutes. Even after erasure, a positive index contrast persists, up to 1650 °C for binary 60Al2O3‐40SiO2 (mol%). This is the first observation of this kind of persisting index contrast, paving the way to ultra‐stable glass‐based optical waveguiding.

Modeling viscosity of commercial glass melts: Adam–Gibbs equation and Gaussian process regression

ABSTRACT A statistically designed property database of six commercial glass families is leveraged to develop models relating viscosity to temperature and composition. Specialized models for each glass family were designed based on the Adam–Gibbs equation. We show that the whole range of viscosity data of one glass family from 100 to 1012 Pa s can be accurately modeled using one composition-dependent and two composition-independent parameters when glass transition temperature and viscosity at that temperature are independently determined. Generalization to a broader composition space using the same approach leads to a loss of accuracy compared to specialized models. However, this can be mostly negated when Gaussian process regression is used to estimate the compositional dependence of configuration entropy and fragility exponent parameters of the Adam–Gibbs equation.

Finite element software for forming processes of glass containers

AbstractA two‐dimensional (2D) axisymmetric numerical model, based on the finite element method, for glass containers forming processes is presented. Glass forming processes involve coupled thermomechanical phenomena in which heat transfer and viscous flow are dependent, as glass viscosity is highly dependent on temperature. During the overall process glass changes from a molten state to a solid state. Therefore, adequate cooling conditions must be set appropriately. From the numerical point of view, the modeling must be robust so as to adjust to the different sequenced stages. Remeshing techniques requiring adequate data transfer, as well as, different thermal and mechanical contact conditions between glass and molds must be taken into account. Also, effective treatment of the incompressible conditions associated with glass flow must be dealt with. The aim is to set the better process parameters so that the final containers have the required geometrical shape and thickness distribution. A numerical model was conducted addressing all these issues and a thickness distribution comparison with real industrial products was performed.

Experimental investigations on B2O3-Al2O3-SiO2 glass-ceramics with different K2O/Na2O ratios for sealing to Kovar alloy

This work studied the effects of the K2O/Na2O ratio on the viscosity of B2O3-Al2O3-SiO2 parent glass and the microstructure, physical, and chemical properties of the resulting glass-ceramics after heat treatment. Additionally, the effect of sealing temperatures on the sealing strength of glass-ceramics-to-Kovar was studied. The results show that the viscosity of parent glass increases with the increase in the R (R=n(K2O)/[n(Na2O)+n(K2O)]) value, and the viscous activation energy of BAS parent glass is about 262.65–293.85 KJ/mol. After heat treatment, the parent glass precipitates the main crystalline phase of Al0.52Zr0.48O1.74 (PDF#53–0294) and ZrO2 (PDF#37–1484). As the R value gradually increases, the thermal expansion coefficient of glass-ceramics initially decreases before increasing within the range of 44.74×10−7 to 52.29×10−7 ℃−1. The density follows a similar trend, fluctuating between 2.40 and 2.45 g/cm3. Meanwhile, the resistivity of the glass-ceramics steadily increases from 1×1012.07 to 1×1014.82 Ω·cm. Moreover, the resistivity of GcN-3 (R=1/2) sample remains excellent at high temperatures, maintaining 3.94×109 Ω·cm at 600 ℃. Subsequently，the BAS glass-ceramics sample GcN-3 (R=1/2) was sealed with Kovar alloy at temperatures range from 930 to 970℃. With the increasing of sealing temperature, the sealing strength increased from 0.51 to 2.10 MPa. In the process of sealing, with the increase of temperature, the iron in the Kovar alloy and the silicon in the glass-ceramics diffused to produce effective sealing and formed different sealing layers. The sealing area was observed to consist of four distinct regions: the matrix alloy, the alloy iron-deficiency area, the iron-rich glass-ceramics and the matrix glass-ceramics.

Effect of MgO addition on the structural evolution, crystallization and properties of self-glazed ceramics sintered from granite sludge

Recycling of granite sludge has both economic and environmental benefits. In this paper, high glossiness self-glazed ceramics were prepared from granite sludge with the addition of TiO2, Ca(OH)2 and MgO by combining two-step sintering and low-temperature crystallization. The effect of MgO addition on the phase evolution, crystallization and properties of the glazed ceramics was studied to reveal its role in the diopside precipitation. With increasing MgO content, the reduced glass viscosity accelerates the dissolution of quartz and anorthite into the liquid glass phase, resulting in a decrease in flexural strength above 1 % MgO. Meanwhile, the addition of MgO increases the non-bridging oxygen to lower the glass transition temperature. The increase in the Al/Si ratio of the glass phase and the mixed alkaline earth effect contribute to an increase in the crystallization temperature. After thermal treatment at 950 °C, the precipitated diopside increases the crystallinity of the glazed glass-ceramic from 6.4 % to 19.3 % at 3 % MgO, resulting in a surface glossiness of 99.7 GU and a flexural strength of 64.1 MPa. High glossiness self-glazed ceramics with an aesthetic appearance could be used in decorative building tiles for scalable utilization of granite sludge.

Effect of composition on the thermal properties and structure of M-Al-Si-O-N glasses, M = Na, Mg, Ca

The primary objective of this study is to explore the relationship between the composition, structure, and thermal characteristics of M-Al-Si-O-N glasses, with M representing sodium (Na), magnesium (Mg), or calcium (Ca). The glasses were prepared by melting in a quartz crucible at 1650 °C and AlN precursor (powder) was utilized as a nitrogen source. The measured thermal properties studied were glass transition temperature (Tg), crystallization temperature (Tc), glass stability, viscosity, and thermal expansion coefficient (α). The findings indicate that increasing the aluminum content leads to higher glass transition, crystallization temperatures, and viscosities. In contrast, fragility values increase with the Al contents, while modifier elements and silicon content influence thermal expansion coefficient values. FTIR analysis revealed that in all glasses, the dominant IR bands are attributed to the presence of Q2 and Q3 silicate units. The effect of Al is observed as a progressive polymerization of the silicate network resulting from the glass-forming role of Al2O3. In most samples, the Q4 silicate mode was also observed, strongly related to the high Al content. Overall, the study shows that the complexity of composition-property correlations where the structural changes affect the properties of Mg/Ca-based oxynitride glasses has potential implications for their use in various technological fields.

A novel Gd2O3–Al2O3–SiO2 glass-ceramics substrate material with comprehensive performance

A novel Gd2O3–Al2O3–SiO2 glass-ceramics (GAS GCS) for substrate application was prepared using the melt-quenching method. The present study pay attention to investigate the crystallization and sintering behaviors, phase compositions, micromorphology, dielectric and mechanical properties of GAS glass-ceramics. An appropriate amount of Gd2O3 diminished the glass viscosity while enhancing structural stability, thereby reducing the activation energy for crystallization and sintering. This contributed to the GAS GCS achieve dense microstructure and high crystallinity. X-ray diffraction (XRD) and Raman spectroscopy analyses confirmed the presence of high-density crystal phases, namely Gd2SiO5 and Gd2Si2O7, which significantly contribute to the enhanced density of the samples. Moreover, a positive correlation was observed between the dielectric constant and crystallinity. Notably, the GAS GCS composition of 41 wt% Gd2O3-21.3 wt% Al2O3-37.7 wt% SiO2 exhibited optimal properties, including a flexural strength of 243.4 MPa, Vickers hardness of 7.77 GPa, elastic modulus of 154.02 GPa, coefficient of thermal expansion of 5.9 × 10−6/°C, dielectric constant of 7.43, and dielectric loss of 4.05 × 10−3. These outstanding characteristics position it as a promising candidate for substrate materials.

Influence of Ca(OH)2 modification on the pore structure and properties of porous glass-ceramics stepwise sintered from granite sludge

The utilization of granite sludge offers significant economic and environmental advantages. This study focuses on preparing porous glass-ceramics from Ca(OH)2-modified granite sludge through a two-step sintering process comprising dense sintering and high-temperature foaming, with the addition of 1 % SiC powder as a foaming agent. The impact of foaming temperature and Ca(OH)2 addition on the structure, compressive strength, specific strength, and thermal conductivity of the porous glass-ceramics is examined. Incorporating the Ca(OH)2 modifier reduces the glass's viscosity and effectively eliminates micropores on the pore walls. The former promotes foaming and increases porosity, while the latter increases the specific strength of porous glass-ceramics. Increasing both the foaming temperature and the Ca(OH)2 concentration reduces glass viscosity and promotes mineral dissolution, facilitating the foaming process. However, the specific strength of the porous glass-ceramics initially increases before decreasing due to pore coalescence and excessive mineral dissolution. Theoretical evaluations of compressive strength and thermal conductivity indicate that porous glass-ceramics possess a closed-cell pore structure. Porous glass-ceramic made from granite powder containing 3.5 % Ca(OH)2 and foamed at 1240 °C exhibits an apparent density and porosity of 0.73 g/cm3 and 67.1 %, respectively. The compressive strength and thermal conductivity are 14.2 MPa and 0.422 W/(m·K) respectively, with a peak specific strength of 19.4 kN·m/kg. This innovative process enables the scalable recycling of granite sludge into energy-saving building materials.

Crystal growth in oxide melts—From CALPHAD thermodynamic modeling to statistical prediction

Using a thermodynamic database approach (CALPHAD), thermodynamic parameters of crystal growth of 31 stoichiometric and non-stoichiometric glasses are calculated. Together with these parameters, the measured growth rates, taken from both literature and in-house measurements, are interpreted in the framework of four interface-controlled growth models: normal, screw-dislocation, 2D growth and a combination of the latter two. A multiple linear regression model is used to explain the maximum crystal growth rate and viscosity at the liquidus temperature with the above growth mechanisms. This finding seems to reflect a general trend and can therefore be used to avoid unintentional devitrification phenomena or to derive their temperature-time range based on the sole knowledge of glass viscosity and liquidus temperature. In future research, it can also help to reduce the experimental workload required for the development of novel glasses and glass-ceramics.

Effect of Chemical Composition on the Thermoplastic Formability and Nanoindentation of Ti-Based Bulk Metallic Glasses.

A series of Ti41Zr25Be34-xNix (x = 4, 6, 8, 10 at.%) and Ti41Zr25Be34-xCux (x = 4, 6, 8 at.%) bulk metallic glasses were investigated to examine the influence of Ni and Cu content on the viscosity, thermoplastic formability, and nanoindentation of Ti-based bulk metallic glasses. The results demonstrate that Ti41Zr25Be30Ni4 and Ti41Zr25Be26Cu8 amorphous alloys have superior thermoplastic formability among the Ti41Zr25Be34-xNix and Ti41Zr25Be34-xCux amorphous alloys due to their low viscosity in the supercooled liquid region and wider supercooled liquid region. The hardness and modulus exhibit obvious variations with increasing Ni and Cu content in Ti-based bulk metallic glasses, which can be attributed to alterations in atomic density. Optimal amounts of Ni and Cu in Ti-based bulk metallic glasses enhance thermoplastic formability and mechanical properties. The influence of Ni and Cu content on the hardness of Ti-based bulk metallic glasses is discussed from the perspective of the mean atomic distance.

Effect of B2O3/SiO2 molar ratio and B2O3 content on viscosity and structure of B2O3–SiO2–Al2O3–Na2O–TiO2 glass lubricant

AbstractGlass lubricant with a suitable viscosity is essential for producing high‐quality titanium products by the hot extrusion process. In this study, a novel lubricant of B2O3–SiO2–Al2O3–Na2O–TiO2 (BSANT) glass was proposed, where the effects of B2O3/SiO2 molar ratio (B/Si) and B2O3 content on viscosity and structure were investigated. The results showed that the BSANT glass viscosity was gradually decreased, and the viscous activation energy was decreased by 20.24% with an increased B/Si ratio from 0.415 to 0.719. This was attributed to the decreased amounts of Q3, [BO4], [AlO4], and bridging oxygen (BO) in the network structure, which in turn resulted in a decreased network degree of polymerization. When B2O3 content was increased from 18.70 to 33.12 mol.%, the melt viscosity value at 950 ℃ was decreased by 64.51%, and the viscous activation energy was reduced by 15.82%. Boron anomalies were also observed in glass melts with the B2O3 content from 28.28 to 33.12 mol.%. The mechanisms responsible for this phenomenon were thoroughly discussed in the study. Additionally, a comparison and discussion of the applications of glass lubricants in metal hot working were presented. A glass lubricant with a specific composition was recommended for use in hot extrusion process within the temperature range of 950–1100°C due to its relatively stable viscosity properties.

Correlation between the Chemical Structure of (Meth)Acrylic Monomers and the Properties of Powder Clear Coatings Based on the Polyacrylate Resins.

This paper presents studies on the influence of the chemical structure of (meth)acrylic monomers on the properties of powder coatings based on polyacrylate resins. For this purpose, a wide range of monomers were selected-2-hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), n-butyl acrylate (nBA), tert-butyl acrylate (tBA), dodecyl acrylate (DA), ethyl acrylate (EA) and benzyl acrylate (BAZ)-for the synthesis of the polyacrylate resin. The average molecular mass and molecular mass distribution of the synthesized resins were measured by gel permeation chromatography (GPC). The glass transition temperature (Tg) and viscosity of polyacrylate resins were determined by using differential scanning calorimetry (DSC) and a Brookfield viscometer. These parameters were necessary to obtain information about storage stability and behavior during the application of powder clear coatings. Additionally, DSC was also used to checked the course of the low-temperature curing reaction between the hydroxyl group contained in the polyacrylate resin and the blocked polyisocyanate group derived from a commercial agent such as Vestanat B 1358/100. The properties of the cured powder clear coatings were tested, such as: roughness, gloss, adhesion to the steel surface, hardness, cupping, scratch resistance, impact resistance and water contact angle. The best powder clear coating based on the polyacrylate resin L_HEMA/6MMA/0.5nBA/0.5DA was characterized as having good scratch resistance (550 g) and adhesion to the steel surface, a high water contact angle (93.53 deg.) and excellent cupping (13.38 mm). Moreover, its crosslinking density (CD) and its thermal stability was checked by using dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA).

Lifespan prediction procedure of volume nanogratings imprinted by femtosecond laser in optical glasses

Volume nanogratings imprinted by infrared femtosecond laser in oxide glasses exhibit a characteristic birefringent signature, which translates into measurable retardance. Upon thermal annealing, such signature is progressively erased, typical of nanograting erasure. In this work, we propose a procedure to predict the lifespan of nanogratings by two main approaches: 1/ numerical modeling of optical retardance ageing using the Rayleigh-Plesset equation, and 2/exploiting VAREPA (VAriable REaction PAthways) framework fed by simulated ageing data. By considering experimental time – temperature annealing conditions, the modeled retardance is gathered as a function of demarcation energy to build a so-called Master Curve and then compared to accelerated ageing experiments. The erasure constant rate k0 can be determined for 8 commercial optical glasses. Based on a distributed Rayleigh-Plesset model, k0 and activation energy distribution are linked to glass viscosity and its temperature dependency. Finally, we discussed the restrictions on VAREPA application for an accurate lifetime prediction. This work provides guidelines for the future development of nanogratings based devices and applications, including optical data storage, birefringent devices, and optical sensors, through a judicious choice of glass composition and associated properties.

Effect of temperature aging of thermoset UD prepregs on inter‐ply friction behavior and formability in prepreg compression molding process

AbstractLimited material out‐life of thermoset prepregs is unavoidable attributed to the slow crosslinking reaction between molecules and curing agents. Previous studies have explored the effects of temperature aging on the final mechanical properties of composites, but have been limited by the processing mismatch in compression molding. The research primarily focuses on the effects of forming temperature and ply angle of prepreg on inter‐ply friction behavior at various aging levels. The importance of inter‐ply friction on the forming quality is further discussed through the L‐shaped specimens forming with prepreg compression molding (PCM) process. Firstly, a comprehensive influence of aging on the properties of resin including cure kinetics, gel point, glass transition temperature (Tg) and viscosity of UD prepreg are characterized and discussed. And then, the influence of factors including resin aging, forming temperature and prepreg ply orientation on the inter‐ply friction are discussed. It can be found that the aging of prepreg reduce 26.47% of inter‐ply friction resistance under room temperature, and the increase of temperature can reduce inter‐ply friction resistance by 79.31%. Finally, the effect of aging on the forming quality is researched by PCM formed L‐shaped components. Results indicated that fresh prepreg with 20°C and prepreg with an aging level of 0.4 performed at 95°C exhibited poor formability, while prepreg with aging level of 0.2 at 95°C exhibited the best forming property. In general, this study provides a basic explain and a practical suggestion to the reuse of room temperature aging thermoset prepregs in PCM process.Highlights A comprehensive of basic properties of aged resin were characterized, as the basic principle for inter‐ply friction behavior analysis. The gel point and final mechanical properties of prepreg were tested, for judging the aged materials whether could be used continuously. The inter‐ply friction behaviors of aged prepregs under various forming temperatures were investigated. The influence of layup orientations on the inter‐ply frictional performance with various aging levels were explored. The effect of aging and forming temperature on the PCM formability were studied and a practical suggestion to the reuse of aged thermoset prepregs in PCM process was given.

Density, Surface Tension, and Viscosity of Molten Ni‐Based Superalloys Using the Maximum Bubble Pressure and Oscillating Crucible Methods

Accurate data on the high‐temperature thermophysical properties, which are density, surface tension, and viscosity, are indispensable for performing high‐precision casting simulations of Ni‐based superalloys. Viscosity is the most important thermophysical property for thermofluidic analysis. However, measuring the viscosity of an alloy, which is lower than that of molten glass, is difficult, and experimental viscosity data are limited. Herein, the density of Ni‐based superalloys is measured using the maximum bubble pressure (MBP) method to determine viscosity. The viscosity is evaluated using the oscillating crucible method. The surface tension is simultaneously measured using the MBP method. In these results, the average density values [kg m−3] of Alloy 65, Alloy 718, Alloy WA, and Alloy 720 are 7.52 × 103, 7.43 × 103, 7.82 × 103, and 7.52 × 103, respectively. The average surface tension values [N m−1] of Alloy 65, Alloy 718, Alloy WA, and Alloy 720 are 1.55, 1.54, 1.47, and 1.51, respectively. The fitting equations of the molten Ni‐based superalloys are as follows. 1) Alloy 65: ; 2) Alloy WA: ; 3) Alloy 720: ; 4) Alloy 718: .

On the effect of stress on the nonequilibrium viscosity of glasses

On the effect of stress on the nonequilibrium viscosity of glasses

Sm-composition engineering of (Hf, Zr, Ta, Sm)B2 high-entropy diborides for superior oxidation resistance

Herein we realize the development of (Hf, Zr, Ta, Sm)B2 high-entropy diborides (HEBs-Sm) with superior oxidation resistance by engineering the compositions of Sm. Specifically, HEBs-Sm with 0–25 mol% Sm contents are first fabricated via borothermal reduction and hot-pressing sintering. Then the HEB-18Sm is predicted to possess the best oxidation resistance at 1473–1773 K via machine learning based on the oxidation depth. Ab initio molecular dynamics simulations indicate that moderate (Sm, Hf, Zr, Ta)2O3 oxidation product facilitates the formation of a three-dimensional skeletal structure in B2O3, which increases the viscosity of B2O3 glass and therefore improves the oxidation resistance of HEBs-Sm.

Thermal performance of glass-based seals for reversible solid oxide cell: Effect of Al2O3 ceramic addition on the crystallization behavior

Al2O3 ceramic addition in glass significantly influenced thermal performance during sealing process in RSOC stack. The effect of Al2O3 ceramic on crystallization behavior, phase compositions, microstructure, and viscosity of glass were discussed. With increasing Al2O3 ceramic content, the crystallization activation energy of glass gradually increased. The crystallization behavior of glass was effectively suppressed with Al2O3 ceramic addition. The glass with 20 wt% Al2O3 ceramic exhibited that the content of BaAl2Si2O8 crystallization phase remained at around 45 wt% after heat-treated at 750 °C for 300 h. The controlled hexagonal BaAl2Si2O8 crystallization content combining with Al2O3 ceramic in seals effectively adjusted viscosity at about 105.1 Pa s and 107.2 Pa s during 700 °C–900 °C. During sealing process, the moderate Al2O3 ceramic and BaAl2Si2O8 were embedded in glass matrix acting as frame to enhance structural stability. Simultaneously, the glass phase owned proper fluidity, which could infiltrate components and ceramic without wide flow and release thermal stress during sealing.

Microwave dielectric characterization and densification mechanism analysis of CaO‐B2O3‐SiO2 glass–ceramic/Al2O3 composites for LTCC applications

AbstractIn this study, nine component points were designed based on a CaO‐B2O3‐SiO2 (CBS) glass system with a high boron content, and CBS glass/Al2O3 composites were developed for low‐temperature co‐fired ceramic (LTCC) applications. Furthermore, the densification process, phase compositions, microstructures, and properties were investigated. The results indicated that the softening of glass and interfacial reaction between the glass and Al2O3 were the two most important factors affecting LTCC's densification process. The real‐time shrinkage rate of LTCC during sintering was simulated using the thermal shrinkage curve and combined with DTA and X‐ray diffraction. It was proven that the formation of the CaAl2(BO3)O phase contributed to the reduction in glass viscosity and promoted the formation of a dense structure. The LTCC composite with 30 vol% glass sintered at 850°C exhibited a coefficient of thermal expansion of 4.55–6.35 ppm/◦C, εr of 3.5–5.0, and a minimum tan δ of 0.0018 at 15 GHz. Therefore, these properties make the CBS–LTCC more suitable for high‐frequency applications.

Structural evolution and mechanical properties of SiO2-Al2O3-MgO-B2O3 glasses with partial substitution of MgO by MgF2

SiO2-Al2O3-MgO-B2O3-MgF2 glasses were prepared using a high-temperature melting method, and their amorphous nature was confirmed through X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS) and magic angle spinning nuclear magnetic resonance (MAS-NMR) were used to investigated structural changes in the glass. It is found that substituting MgO with MgF2 disrupted the Si-O and Al-O networks in the high-temperature glass melt structure, reducing the degree of glass network polymerisation and viscosity. During cooling and annealing, moderate amounts of fluoride ions (F−) promoted the linkage of a partially fragmented glass network by converting [BO3] and [AlO5] into [BO4] and [AlO4]. An increased F− content improved the mechanical properties of the glass, including flexural strength, Young's modulus, and hardness, which peaked at 157.50 MPa, 95.21 GPa, and 838.57 HV with 2 mol% MgF2 substitution. These findings advance our understanding of the behavior of MgF2-substituted glass.