Ideality of liquid structure: A case study for metallic alloy liquids
Abstract not provided
Ryu, Chae Woo↗
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Results for “glass structure”
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Simulation of Helium Flow Visualization Apparatus for Studies of Blanket Cooling in Fusion Reactors
Flow visualization is essential to understanding helium cooling performance. This article investigates helium flow visualization in an apparatus to support the design of the blanket first wall for a fusion reactor. Helium’s safety advantages make it an attractive coolant, but effective cooling and flow visualization remain challenging. Sophisticated simulations are conducted in different test sections to address three key areas in the design of a test apparatus and cooling channel enhancements: the influence of viewing glass windows on flow patterns, the impact of increased heating, and the effectiveness of cooling structures like baffles. Viewing glass windows introduce flow recirculation region bifurcation and flow asymmetry, affecting flow patterns and necessitating careful analysis in future experiments. Increased heating results in helium flow detachment from the heated surface, leading to hot spots. Cooling structures, particularly baffles, prove effective in maintaining consistent attachment to the heated surface, improving the heat transfer performance. Further, this study also examines a tunable parameter in the turbulence model, highlighting the importance of accurate model tuning for future fusion reactor cooling designs. With an imminent helium flow visualization facility, these simulations will be used to optimize cooling structures on the heated wall to improve flow attachment and heat transfer efficiency. This work serves as a first investigation of the helium flow visualization apparatus for blanket cooling enhancement in fusion reactor design.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Predicting the Dissolution Rate of Borosilicate Glasses using QSPR analysis based on molecular dynamics simulations
Quantitative Structure Property Relationship (QSPR) analysis based on molecular dynamics (MD) simulations is a promising approach for establishing the composition-property relationships of glass and other materials with complex structures. A series of 20 borosilicate and boroaluminosilicate glasses have been modeled by using MD simulations with recently developed effective potentials. Short- and medium-range structures of these glasses were analyzed and, based on these structural information, QSPR analysis of the initial dissolution rate (r0) was made and compared with measured r0 at 90°C and pH 9 using various structural descriptors such as percentage of bridging oxygen species, network connectivity and average ring size. The structural descriptors, Fnet, containing energetic information such as single bond strength and other structural information were also used. It was found that overall network connectivity, average ring size and Fnet give reasonable predictions of the r0 of studied glasses, given the conditions that the glasses are homogeneous and dissolve congruently. Modifying glass compositions to account preferential release of modifiers gives a better prediction for incongruently dissolving glasses. The results were compared with our recent work of predicting glass dissolution behavior from compositions using the topological-constraints-based models.
Du, Jincheng↗
Continuous polyamorphic transition in high-entropy metallic glass
Polyamorphic transition (PT) is a compelling and pivotal physical phenomenon in the field of glass and materials science. Understanding this transition is of scientific and technological significance, as it offers an important pathway for effectively tuning the structure and property of glasses. In contrast to the PT observed in conventional metallic glasses (MGs), which typically exhibit a pronounced first-order nature, herein we report a continuous PT (CPT) without first-order characteristics in high-entropy MGs (HEMGs) upon heating. This CPT behavior is featured by the continuous structural evolution at the atomic level and an increasing chemical concentration gradient with temperature, but no abrupt reduction in volume and energy. The continuous transformation is associated with the absence of local favorable structures and chemical heterogeneity caused by the high configurational entropy, which limits the distance and frequency of atomic diffusion. As a result of the CPT, numerous glass states can be generated, which provides an opportunity to understand the nature, atomic packing, formability, and properties of MGs. Moreover, this discovery highlights the implication of configurational entropy in exploring polyamorphic glasses with an identical composition but highly tunable structures and properties.
36 MATERIALS SCIENCE↗
In-situ investigation of the vibrational properties of H 2 O CO 2 -bearing and dry K-rich basaltic glasses at high pressure by mid infrared spectroscopy
Here, the vibrational properties of CO 2 –H 2 O-bearing and dry synthetic K-rich basaltic glasses were investigated at room temperature and pressures between 0.0001–5.5 GPa using the diamond anvil cell combined with in situ reflectance and transmittance Fourier Transform infrared micro-spectroscopy. The absorption coefficient a(v) calculated from the Kramers-Kronig relation shows that glasses are dominated by the Q 2 aluminosilicate unit followed by Q 1 , Q 3 . The variation in Q n concentration upon compression suggests that glasses undergo polymerization from ambient pressure to 2 GPa followed by less marked structural changes up to 4 GPa, above which the structure is further polymerized. Once decompressed, glasses retained a polymerized structure. Our results show that 1.03 wt% CO 2 -1.42 wt% H 2 O in a glass with 3.10 wt% K 2 O and 46.77 wt% SiO 2 prevent the formation of fully polymerized connections when cold-compressed. Our results can be used to explain the effect of volatiles and alkali on the rheology of natural basaltic magmas.
36 MATERIALS SCIENCE↗
Evolution of the structure and chemical composition of the interface between multi-component silicate glasses and yttria-stabilized zirconia after 40,000 h exposure in air at 800 °C
The chemical and structural stability of two commercial multicomponent silicate glasses (SCN and G6) in contact with yttria-stabilized zirconia (YSZ) was investigated after exposure times of up to 40,000 h in air at 800 °C. With exposure time, interfacial layers develop at the SCN-YSZ and G6-YSZ interfaces, which were characterized in detail using both quantitative chemical analysis and atomic-resolution imaging. At the SCN-YSZ interface, a Ca-Ba-Si-O reaction phase was found to grow by diffusion control. In G6-YSZ, Raman spectroscopy and electron microscopy revealed a disorganized interfacial reaction later between G6 and YSZ, and the occurrence of cubic to tetragonal to monoclinic phase transformations in YSZ. Finally, this microstructural evolution is discussed in terms of devitrification resistance of glass and diffusion processes at interfaces.
36 MATERIALS SCIENCE↗
Do Ionic Liquids Slow Down in Stages?
High impact recent articles have reported on the existence of a liquid–liquid (L–L) phase transition as a function of both pressure and temperature in ionic liquids (ILs) containing the popular trihexyltetradecylphosphonium cation (P 666,14 + ), sometimes referred to as the “universal liquifier”. The work presented here reports on the structural-dynamic pathway from liquid to glass of the most well-studied IL comprising the P 666,14 + cation. We present experimental and computational evidence that, on cooling, the path from the room-temperature liquid to the glass state is one of separate structural-dynamic changes. The first stage involves the slowdown of the charge network, while the apolar subcomponent is fully mobile. A second, separate stage entails the slowdown of the apolar domain. Whereas it is possible that these processes may be related to the liquid–liquid and glass transitions, more research is needed to establish this conclusively.
36 MATERIALS SCIENCE↗
Structural fragility and Curie-Weiss behavior distinguishing glass forming ability in Ti-based metallic alloys
Not Available
Mauro, N. A. (ORCID:0000000167978474)↗
Structural evolution of fused silica below the glass-transition temperature revealed by in-situ neutron total scattering
Not Available
Shi, Ying (ORCID:0000000241361086)↗
Pressure-induced local structural crossover in a high-entropy metallic glass
Explore the source record for details and available documents.
Zhang, Xin↗
Machine-Learned Quantification of Local Structure and its Effects in Fracture of Silica Glass.
Abstract not provided.
Hardin, Thomas↗
Deciphering the non-linear impact of Al on chemical durability of silicate glass
The role of Al in aluminosilicate glasses remains somewhat a mystery: at low concentrations, it increases the resistance to hydrolysis of the glass, whereas at high concentrations an opposite effect is observed. To understand the origin of the phenomenon on a fundamental atomistic scale, we performed 577 MD simulations and applied potential mean force (PMF) calculations to estimate the activation barriers for hydrolysis and to statistically correlate them with local structural features of the glass. Models of pure silicate and aluminosilicate glasses are constructed and investigated. PMF simulation results are further validated by the experimental measurements and revealed that Al is very easy to dissociate, but it also increases the glass chemical durability through significantly increasing both the strength of Si and network connectivity of the glass. In contrast, at high Al concentration, preferential dissolution of Al weakens the silicate network, which it supposes to strengthen, and so the glass resistance becomes poor. Through PMF calculations, we evaluated the activation barriers for dissociating bonds around Al as 0.49 eV, which is less than a half of the energy to dissociate bonds around Si in pure silicate (1.22 eV) and around Si in aluminosilicate glass (1.34 eV), all these energy differences being statistically significant. Molecular structural level investigation revealed that Si with Al as a second neighbor in the glass network has a significantly higher activation energy for dissociation than Si in pure silicate glass. Furthermore, the proposed approach opens the way to the development of quantitative predictive models of glass durability.
36 MATERIALS SCIENCE↗
Electronic bonding transitions in oxide glass above two megabar pressures
Inelastic x-ray scattering (IXS) of B 2 O 3 glass up to ∼2.2 Mbar reveals electronic bonding transitions in oxide glasses. B -edge IXS identifies the high-energy feature above ∼1.4 Mbar and a gradual increase in its intensity toward ∼2.2 Mbar, indicating the formation of hypervalent boron via electron polarization to oxygen atoms. The pressure-driven high energy shifts in O -edge IXS indicate pronounced electronic dispersion that increases upon densification of amorphous oxides above ∼2 Mbar. The extent of the energy shifts and enhanced polarization correlate with increasing atomic radius of cation in oxide glass, establishing the role of cation radius in electronic structures of amorphous oxides under compression. The results elucidate the electronic mechanisms behind the structural transformation in low- oxide glasses, where transitions to highly coordinated cations are hindered well above 1 Mbar, providing the origin of incompressibility of low- amorphous oxide under multi-Mbar compression. Published by the American Physical Society 2024
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Effect of network connectivity on behavior of synthetic Broborg hillfort glasses
There is wide industrial interest in developing robust models of long-term (>100 years) glass durability. Archeological glass analogs, glasses of similar composition, and alteration conditions to those being tested for durability can be used to evaluate and inform such models. Two such analog glasses from a 1500-year-old vitrified hillfort near Uppsala, Sweden have previously been identified as potential analogs for low concentration Fe-bearing aluminosilicate nuclear waste glasses. However, open questions remain regarding the melting environment from which these historic glasses were formed and the effect of these conditions on their chemical durability. A key factor to answering the previous melting and durability questions is the redox state of Fe in the starting and final materials. Past work has shown that the melting conditions of a glass-forming melt may influence the redox ratio value (Fe +3 /ΣFe), a measure of a glass's redox state, and both melting conditions and the redox ratio may influence the glass alteration behavior. Synthetic analogs of the hillfort glasses have been produced using either fully oxidized or reduced Fe precursors to address this question. In this study, the melting behavior, glass transition temperature, oxidation state, network structure, and chemical durability of these synthesized glass analogs is presented. Resulting data suggests that the degree of network connectivity as impacted by the oxidation state of iron impacted the behavior of the glass-forming melt but in this case does not affect the chemical durability of the final glass. Glasses with a lower degree of melt connectivity were found to have a lower viscosity, resulting in a lower glass transition temperature and softening temperature, as well as in a lower temperature of foam onset and temperature of foam maximum. This lower degree of network connectivity most likely played a more significant role in accelerating the conversion of batch chemicals into glass than the presence of water vapor in the furnace's atmosphere. Future work will focus on using the results from this work with outcomes from other aspects of this project to evaluate long-term glass alteration models.
36 MATERIALS SCIENCE↗
4 d element induced improvement of structural disorder and development of weakly reentrant spin-glass behavior in NiRuMnSn
The pursuit of efficient spin polarization in quaternary Heusler alloys with the general formula XX'YZ (where X, X', and Y are transition metals and Z is a p-block element) has been a subject of significant scientific interest. While previous studies showed that isoelectronic substitution of a 4d element in place of a 3d element in quaternary Heusler alloys improves the half-metallic ferromagnetic characteristics, our research here, on the quaternary Heusler alloy NiRuMnSn, reveals a strikingly different scenario. In this study, we present a detailed structural analysis of the material using x-ray absorption fine structure and neutron diffraction techniques which confirms the formation of a single-phase compound with 50:50 site disorder between Ni and Ru atoms at 4c and 4d sites. Contrary to expectations, our density functional theory calculations suggest a considerable decrease in spin polarization even in the ordered structure. Additionally, we report on the compound's exceptional behavior, displaying a rare reentrant spin-glass property below ~ 60 K, a unique and intriguing feature for quaternary Heusler-type compounds.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Spectroscopic evaluation of tribologically-induced changes in surface chemistry of Zr-based bulk metallic glass
Bulk metallic glasses (BMGs) are promising structural materials owing to their high elastic limit and yield strength-to-weight ratio. While BMGs also exhibit attractive tribological properties (e.g., high wear resistance), the scientific basis for this behavior is not yet established. In particular, tribologically-induced changes in surface chemistry upon sliding are still an open topic of research. Here, we evaluated by X-ray photoelectron spectroscopy (XPS) the evolution of the surface chemistry of Vitreloy 105 (a Zr-rich BMG) upon sliding under different contact conditions against a tungsten carbide countersurface. The spectroscopic results indicate that the relative fraction of the metallic elements in the near-surface region is not affected by the sliding speed when the applied contact pressure is lower than 1.37 GPa, while a decrease in metallic zirconium was observed at lower sliding speeds and higher applied contact pressure (i.e., 1.71 GPa). Based on the spectroscopic results, a model is proposed for the effect of mechanical stress on the extent of oxidation of the near-surface region of Zr-based BMGs. In conclusion, the results of this work provide novel insights into the surface phenomena occurring on BMGs upon sliding and add significantly to our understanding of the tribological response of this class of promising structural materials.
Bulk metallic glasses↗
Medium-Range Ordering in the Ionic Glass Electrolytes LiPON and LiSiPON
In this work, we provide an in-depth structural characterization of the amorphous ionic glasses LiPON and LiSiPON with high Li content. Based on ab initio molecular dynamics simulations, the structure of these materials is an inverted structure with either isolated polyanion tetrahedra or polyanion dimers in a Li+ matrix. Based on neutron scattering data, this type of inverted structure leads to a significant amount of medium-range ordering in the structure, as demonstrated by two sharp diffraction peaks and a periodic structural oscillation in the density function G(r). While this medium-range ordering is commonly observed in liquids and metallic glasses, it has not previously been observed in oxides. On a local scale, adding N and Si increases the number of anion bridges and polyanion dimer structures, leading to higher ionic conductivity. In the medium-range ordering, the addition of Si leads to more disorder in the polyanion substructure but a significant increase in the ordering of the O substructure. Finally, we demonstrate that this inverted structure with medium-range ordering results in a glassy material that is both mechanically stiff and ductile on the nanoscale.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗