Glass Formation Research Articles

Pressure dependence of intermediate-range order and elastic properties of glassy Baltic amber.

Amber is a unique example of a fragile glass that has been extensively aged below its glass transition temperature, thus reaching a state that is not accessible under normal experimental conditions. We studied the medium-range order of Baltic amber by x-ray diffraction (XRD) at high pressures. The pressure dependences of the low-angle XRD intensity between 0 and 5 Å^{-1} were measured from 0 to 7.3 GPa by the energy-dispersive XRD. The first diffraction peak at 1.1 Å^{-1} and ambient pressure has a doublet structure consisting of the first sharp diffraction peak (FSDP) at 1.05 Å^{-1} and the second feature at 1.40 Å^{-1}. The peak position and the width of the FSDP increase as the pressure increases, while the intensity of the FSDP decreases. Below P_{0}=2.4 GPa, the rapid increase of the FSDP peak position was observed, while above P_{0}, the gradual increase was observed. Below P_{0}, voids and holes in a relatively low-density state are suppressed, whereas above P_{0}, the suppression becomes mild. Such a change suggests the crossover from the low- to high-density state at P_{0}. There is a close correlation between the pressure dependence of XRD and previously reported sound velocity results. The correlation between the mean-square fluctuation of the shear modulus on the nanometer scale and fragility in amber and other glass formers is also discussed.

Anomalies in the temperature dependences of the time constant of various glass-forming substances

In this work the new precise method for describing the temperature dependences of glass formers which is based on the use of the power law function (JNCS 555 (2021) 120618) is proposed. Analysis of practical temperature dependences using the proposed method made it possible to detect subtle anomalies of fragile relaxation which cannot be detected by other means. Three different types of anomalies were found: cluster-to-cluster (CTC), fragile-to-fragile (FTF), and strong-to-fragile (STF) transitions. The CTC and FTF transitions are described for the first time. The CTC transition is accompanied by changes in activation energy with constant fragility; FTF transition due to changes in fragility and activation energy, as well as the STF transition. The processes occurring in the vicinity of transition points are explained from the point of view of the cluster model.

Breaking the vitrification limitation of monatomic metals.

The question of whether all materials can solidify into the glassy form proposed by Turnbull half a century ago remains unsolved. Some of the simplest systems of monatomic metals have not been vitrified, especially the close-packed face-centred cubic metals. Here we report the vitrification of gold, which is notoriously difficult to be vitrified, and several similar close-packed face-centred cubic and hexagonal metals using a method of picosecond pulsed laser ablation in a liquid medium. The vitrification occurs through the rapid cooling during laser ablation and the inhibition of nucleation by the liquid medium. Using this method, a large number of atomic configurations, including glassy configurations, can be generated simultaneously, from which a stable glass state can be sampled. Simulations demonstrate that the favourable stability of monatomic metals stems from the strong topological frustration of icosahedra-like clusters. Our work breaks the limitation of the glass-forming ability of matter, indicating that vitrification is an intrinsic property of matter and providing a strategy for the preparation and design of metallic glasses from an atomic configuration perspective.

Stress-tunable abilities of glass forming and mechanical amorphization

Mechanical amorphization, a widely observed phenomenon, has been utilized to synthesize novel phases by inducing disorder through external loading, thereby expanding the realm of glass-forming systems. Empirically, it has been plausible that mechanical amorphization ability consistently correlates with glass-forming ability. However, through a comprehensive investigation in binary, ternary, and quaternary systems combining neutron diffraction, calorimetric experimental approaches and molecular dynamics simulation, we demonstrate that this impression is only partly true and we reveal that the mechanical amorphization ability can be inversely correlated with the glass forming ability in certain cases To provide insights into these intriguing findings, we present a stress-dependent nucleation theory that offers a coherent explanation for both experimental and simulation results. Our study identifies the intensity of mechanical work, contributed by external stress, as the key control parameter for mechanical amorphization, rendering the ability to tune this process. This discovery not only unravels the underlying correlation between mechanical amorphization and glass-forming ability but also provides a pathway for the design and discovery of new amorphous phases with tailored properties.

Observation of a Reversible Order-Order Transition in a Metal-Organic Framework - Ionic Liquid Nanocomposite Phase-Change Material.

Metal-organic framework (MOF) composite materials containing ionic liquids (ILs) have been proposed for a range of potential applications, including gas separation, ion conduction, and hybrid glass formation. Here, an order transition in an IL@MOF composite is discovered using CuBTC (copper benzene-1,3,5-tricarboxylate) and [EMIM][TFSI] (1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide). This transition - absent for the bare MOF or IL - provides an extended super-cooling range and latent heat at a capacity similar to that of soft paraffins, in the temperature range of ≈220°C. Structural analysis and in situ monitoring indicate an electrostatic interaction between the IL molecules and the Cu paddle-wheels, leading to a decrease in pore symmetry at low temperature. These interactions are reversibly released above the transition temperature, which reflects in a volume expansion of the MOF-IL composite.

Impact of atomic packing and electronic structure on icosahedral short-range order and glass-forming ability of Zr–Cu metallic glasses

ABSTRACT Chemical and topological short-range ordering are important for glass formation in metallic alloys. Yet, it remains little understood from the viewpoint of the electronic bonding among the constituent elements of the alloys. In this work, we study CuxZr100−x, (46 ≤ x ≤ 70) metallic glasses, where the atomic packing efficiency and the electronic structure of the full icosahedra, the key short-range order structures, have been investigated in detail. To capture a realistic picture of the electronic bonding in the icosahedra in the as-quenched metastable state, DFT study of the electronic structure of the icosahedra extracted from classical molecular dynamics simulation is carried out. Results for the CunZr13−n , (4 ≤ n ≤ 9) clusters reveal that Cu6Zr7, Cu7Zr6 and Cu8Zr5 are the most abundant, electronically stable in Cu50Zr50 , Cu58Zr42 and Cu64Zr36, respectively. These three clusters also exhibit pseudo-gap in the density of states at the Fermi level – a feature linked with glass-forming ability according to the nearly-free electron approach. The partial density of states demonstrates the effect of small changes in the stoichiometry of the clusters on the s, p and d states of Cu and Zr in Cu–Cu and Cu–Zr bonding and hence, the stability of the clusters.

Non-isothermal crystallization behavior of Cr50Fe6Co7Mo14C15B6Y2 metallic glass with super high content of Cr and integrated merits

In present work, non-isothermal crystallization behavior for novel Cr50Fe6Co7Mo14C15B6Y2 metallic glass (MG) with super high content of Cr and excellent merits was investigated by differential scanning calorimeter and X-ray diffraction. Both of the Kissinger and Ozawa methods show that the present glass transition is much harder than other transitions for a much larger apparent activation energy (E). While, the growth process of present second crystallization event is the easiest process, since it possesses the smallest E. Meanwhile, the local activation energy established by Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall methods both exhibit a trend of increasing to the maximum value at first and then gradual decrease until the finish of the crystallization, indicating that the difficulty increases until to the maximum at first and then gradually decreases during crystallization. Moreover, all the local Avrami exponent n(x) possesses a value of about 0 <n(x) < 1.5, implying a crystallization with pre-existing nuclei for present non-isothermal crystallization. Furthermore, the glass formation melt of present MG is considered as an intermediate one with moderate thermal stability. Additionally, the alloy firstly changes from monolithic MG to a composite of amorphous matrix superimposed with the main crystalline phases ((Fe,Cr)23(C,B)6, (Cr2.5Fe4.3Mo0.1)C3, Fe3Mo3C, FeC and some unknown phases), and then the remained amorphous matrix thoroughly changes to these crystalline phases with enriched crystal planes and fraction during crystallization. The results can supply basic data for designing valid crystallization strategy to tune performances of metallic glasses with high content of Cr.

Nearly close-packed atomic arrangements in BaTi2O5 glass

Recent advancements in glass synthesis have led to the creation of novel oxide glasses without tetrahedral corner-sharing networks. Of particular interest are glasses with high atomic packing densities, showcasing improved functionalities. Conventional analyses revealed the presence of not only four-coordinated polyhedra but also five- or six-coordinated polyhedra, which are connected via corner-sharing, edge-sharing, or face-sharing linkages. This study adapted the reduced atomic arrangement (RAA) method to analyze densely packed oxide glasses. The RAA method revealed a near-close-packed structure within a 10 Å range throughout BaTi2O5 glass, with Ba2+ and O2− ions arranged accordingly. Moreover, the structural model derived from relaxing the closest-packed arrangement via molecular dynamics simulations faithfully replicated the X-ray diffraction data. These findings suggest that minor deviations from the closest-packed atomic arrangement can initiate glass formation without corner-sharing tetrahedral networks. The RAA method proves highly effective in understanding glass formation mechanisms in unconventional oxide glasses.

ИЗУЧЕНИЕ ОСОБЕННОСТЕЙ СТЕКЛООБРАЗОВАНИЯ ЭМАЛЕВЫХ ФРИТТ ДЛЯ СТАЛЬНЫХ ОБЛИЦОВОЧНЫХ ПАНЕЛЕЙ

Cladding of buildings and structures, combining decorative, protective and thermal insulation functions, is currently in great demand in the construction industry. One of the effective areas for using vitreous and glass-crystalline enamel coat-ings is the protection of steel cladding panels for construction purposes. Therefore, there is a need to create and widely implement competitive enamel-coated panels made in Russia with specified properties. The work identifies the areas of glass formation and constructs a composition diagram in the SiO2–B2O3–Na2O–RxOy system of glass areas, which are the basis for the production of ground and top enamels. The physicochemical patterns of glass formation in the Na2O–B2O3–Al2O3–SiO2–RxOy system for the production of enamel coatings have been established by varying the values of the connectivity indicators of the aluminum-boron-silicon-oxygen framework.

Dynamical Facilitation Governs the Equilibration Dynamics of Glasses

Convincing evidence of domain growth in the heating of ultrastable glasses suggests that the equilibration dynamics of supercooled liquids could be driven by a nucleation and growth mechanism. We investigate this possibility by simulating the equilibration dynamics of a model glass during both heating and cooling between poorly and well-annealed states. Though we do observe the growth of domains during heating, we find that domains are absent during cooling. This absence is inconsistent with classical nucleation theory. By comparing the equilibration dynamics of our glass with that of two models with kinetic constraints, we demonstrate that dynamical facilitation generically leads to heating driven by domain growth and cooling without domains. Our results provide strong evidence that dynamical facilitation, not nucleation and interfacial-tension-driven domain growth, is the driving mechanism for the equilibration dynamics of glass formers. Published by the American Physical Society 2024

Synchronously improving glass forming ability and mechanical properties by Pd alloying Zr-Al-Cu bulk metallic glass

In this work, the influences of Pd addition on the glass-forming ability (GFA), thermal behaviors, mechanical properties and microstructure of the Zr60Al10Cu30 bulk metallic glasses (BMGs) were systematically investigated. Our study shows that proper addition of Pd can simultaneously improve the GFA, strength and plasticity of BMGs. The BMGs with Pd contents of 2.5 at.% and 5 at.% exhibit high GFA of 10 mm and 12 mm, high strength of 1852 MPa and 1858 MPa, and good plasticity of 4.3 % and 5.9 %, respectively, all of them are much higher than those of Zr60Al10Cu30 BMGs. It is revealed that alloying BMGs with proper Pd promotes the formation of a higher degree of icosahedral clusters, which is responsible for improved GFA and strength, and simultaneously encourages a decrease in the volume of shear transition zone (STZ) and the amount of imperfect ordered packing (IOP) clusters, which are responsible for the enhanced plasticity. Our findings indicate that the synergistic effect of short-range ordered structures induced by alloying amorphous alloys plays an important role in simultaneously improving the GFA and mechanical properties, providing valuable insights for BMG design.

The scandium effect in Gd-rich BMGs: How and why does this ingredient work better than others?

Scandium is commonly known as a superior modifier for most alloys and compounds, substantially improving their phase stability and physical properties, as well as glass-forming ability. A special case is rare-earth based magnetic metallic glasses, which are an unique platform for intra-elemental substitution due to the chemical affinity of the lanthanides, yttrium and scandium. The latter, used as an alloying additive and being the smallest atom among the entire family, can drastically affect structure formation and magnetism in these metallic glasses. The main issue is that its modifying role is not well understood due to scarce information on the scandium effects in such rare-earth systems. This study is focused on thermal and magnetic analysis of some popular Gd-based BMGs redesigned with minor Sc additives. Here, we consider temperature behavior of specific heat capacity and entropy functions for both amorphous and crystalline phases to estimate the scandium effect on GFA and thermal stability of the glasses. As well, we inspect magnetic and magnetocaloric properties of these BMGs to understand whether this very expensive metal can radically improve the alloy magnetism and make these materials suitable for potential applications.

Unifying the temperature dependent dynamics of glass formers.

Strong changes in bulk properties, such as modulus and viscosity, are observed near the glass transition temperature, Tg, of amorphous materials. For more than a century, intense efforts have been made to define a microscopic origin for these macroscopic changes in properties. Using transition state theory (TST), we delve into the atomic/molecular level picture of how microscopic localized unit relaxations, or "cage rattles," evolve to macroscopic structural relaxations above Tg. Unit motion is broken down into two populations: (1) simultaneous rearrangement occurs among a critical number of units, nα, which ranges from 1 to 4, allowing a systematic classification of glass formers, GFs, that is compared to fragility; and (2) near Tg, adjacent units provide additional free volume for rearrangement, not simultaneously, but within the "primitive" lifetime, τ1, of one unit rattling in its cage. Relaxation maps illustrate how Johari-Goldstein β-relaxations stem from the rattle of nα units. We analyzed a wide variety of glassy materials and materials with a glassy response using literature data. Our four-parameter equation fits "strong" and "weak" GFs over the entire range of temperatures and also extends to other glassy systems, such as ion-transporting polymers and ferroelectric relaxors. The role of activation entropy in boosting preexponential factors to high "unphysical" apparent frequencies is discussed. Enthalpy-entropy compensation is clearly illustrated using the TST approach.

Orientational ordering and correlation in quasi-one-dimensional hard-body fluids due to close-packing degeneracy.

We study the orientational ordering properties of some quasi-one-dimensional hard-body fluids, where the anisotropic particles are confined to a straight line, while they are free to rotate in a plane. We examine a class of models where the close-packing structure is degenerate, i.e., the highest possible density can be realized with different orientational ordering. We find that the close-packing degeneracy always gives rise to a diverging orientational correlation, which can be a marker of phase transition, glass formation, and jamming. In the case of isotropic or partially ordered phases at the close-packing density, the diverging orientational correlation indicates a tendency for being a strongly ordered nematic phase. However, the orientational divergence in the perfect nematic phase shows that the particles must rotate in concert to go from one closely packed structure to another.

Sulphuric precipitates in novel titanium-based, sulphur-bearing bulk metallic glass – a BMG composite?

ABSTRACT New titanium-based metallic glasses containing sulphur as a key element have recently been developed and are the subject of ongoing research related to the effects of sulphur introduction into glass-forming alloy systems. Here we report on the formation of sulphuric precipitates during solidification of a Ti40Zr35Cu17S8 alloy and on the occurrence of secondary intermetallic compound crystallization starting in sulphur-depleted zones around the precipitates. The alloy is a promising metallic glass for use as a structural and biomedical material as it shows a high yield strength and good corrosion resistance paired with a low density. The role of sulphur for the glass formation in the Ti-Zr-Cu-S system is discussed and specimens quenched into different structural states are investigated by means of high-energy synchrotron diffraction and electron microscopy. The electron microscopic findings reveal that sulphuric precipitates precede the crystallization of an intermetallic (Ti, Zr)2Cu phase, which is the primary phase when sulphur is not present in the system and thus lead to a higher glass-forming ability. The sulphuric precipitates are found in specimens of various casting thickness and differ in their volume percentages depending on the size of the cast sample, while the secondary phase (Ti, Zr)2Cu crystallizes heterogeneously in the interfaces between the sulphuric precipitates and the local matrix.

Temperature and composition dependence modeling of viscosity and electrical conductivity of low-activity waste glass melts

The development of models that accurately relate the properties of a glass melt to its temperature and composition is important for glass formulation, melter control, and modeling the melt flow, refractory corrosion, and production rate. Using a database consisting of more than 4,000 data points measured between 900 °C and 1250 °C for over 600 unique low-activity waste glass compositions, we developed models for the melt viscosity and electrical conductivity. Models based on the Gaussian process regression approach outperformed models based on the Vogel–Fulcher–Tammann equation according to four standard metrics and yielded reliable prediction intervals. The models found primarily linear effects between properties and individual components, except for the effect of the Na2O mass fraction on the electrical conductivity. The effects were found to be consistent with current theories on physical processes involved with those properties.

Current and Future Perspectives of Bioactive Glasses as Injectable Material.

This review covers recent compositions of bioactive glass, with a specific emphasis on both inorganic and organic materials commonly utilized as matrices for injectable materials. The major objective is to highlight the predominant bioactive glass formulations and their clinical applications in the biomedical field. Previous studies have highlighted the growing interest among researchers in bioactive glasses, acknowledging their potential to yield promising outcomes in this field. As a result of this increased interest, investigations into bioactive glass have prompted the creation of composite materials and, notably, the development of injectable composites as a minimally invasive method for administering the material within the human body. Injectable materials have emerged as a promising avenue to mitigate various challenges. They offer several advantages, including minimizing invasive surgical procedures, reducing patient discomfort, lowering the risk of postoperative infection and decreasing treatment expenses. Additionally, injectable materials facilitate uniform distribution, allowing for the filling of defects of any shape.

Are Critical Fluctuations Responsible for Glass Formation?

The dynamic heterogeneities occurring just before the transition to the glassy phase have been named as the cause of amorphization in supercooled systems. Numerous studies conducted so far have confirmed this hypothesis, and based on it, a widely accepted solution to the puzzle of glass transition has been developed. This report focuses on verifying the existence of a strong pretransitional anomaly near the glass transition Tg. For this purpose, supercooled liquid-crystalline systems with a strong rod-like structure were selected. Based on the obtained experimental data, we demonstrate in this article that the previously postulated dynamic heterogeneities exhibit a critical characteristic, meaning a strong pretransitional anomaly can be observed with the described critical exponent α=0.5. Due to this property, it can be concluded that these heterogeneities are critical fluctuations, and consequently, the transition to the glassy state can be described based on the theory of critical phenomena. To measure the pretransitional anomaly near Tg in supercooled liquid-crystalline systems, broadband dielectric spectroscopy (BDS) and nonlinear dielectric effect (NDE) methods were applied. The exponent α provides insight into the nature and intensity of critical fluctuations in the system. A value of α=0.5 suggests that the fluctuations become increasingly intense as the system approaches the critical point, contributing to the divergence in specific heat. Understanding the role of critical fluctuations in the glass transition is crucial for innovating and improving a wide range of materials for energy storage, materials design, biomedical applications, food preservation, and environmental sustainability. These advancements can lead to materials with superior properties, optimized manufacturing processes, and applications that meet the demands of modern technology and sustainability challenges.

Effect of La2O3 on the optical, thermal, structural and radiation shielding properties of TeO2–ZnO–BaO glasses

Influence of lanthanum oxide (La2O3) on various properties of melt quenched zinc barium tellurite glasses (TeO2–BaO–ZnO) have been investigated. Lanthanum was limited to 10 mol% beyond which the glass formation ability was affected leading to crystallization in the proposed tie-line. Glass transition temperature improved with lanthanum oxide incorporation, while the density and energy band gap values showed a minimum at 5 mol%. The observed variation with lanthanum oxide doping was clearly elucidated from Raman spectral data, which indicated their influence in modifying the host ternary glass network. Radiation shielding parameter calculations showed a larger mass and linear attenuation coefficients for glasses doped with 10 mol% lanthanum oxide, indicating the influence of heavier oxides in improving the shielding properties and consequently acting as replacement candidate for toxic lead-based compounds.

Glass Formation in Ring Polymer Melts Having Variable Knot Complexity and Molecular Mass

Glass Formation in Ring Polymer Melts Having Variable Knot Complexity and Molecular Mass