Solid-liquid Region Research Articles

Molecular-Level Understanding of Phase Stability in Phase-Change Nanoemulsions for Thermal Energy Storage by NMR Spectroscopy.

Phase change materials (PCMs) are latent heat storage materials that can store or release thermal energy while undergoing thermodynamic phase transitions. Organic PCMs can be emulsified in water in the presence of surfactants to enhance thermal conductivity and enable applications as heat transfer fluids. However, PCM nanoemulsions often become unstable during thermal cycling. To better understand the molecular origins of phase stability in PCM nanoemulsions, we designed a model PCM nanoemulsion system and studied how the molecular-level environments and dynamics of the surfactants and oil phase changed upon thermal cycling using liquid-state nuclear magnetic resonance (NMR) spectroscopy. The model system used octadecane as the oil phase, stearic acid as the surfactant, and aqueous NaOH as the continuous phase. The liquid fraction of octadecane within the nanoemulsions was quantified noninvasively during thermal cycling by liquid-state 1H single-pulse NMR measurements, revealing the extent of octadecane supercooling as a function of temperature. The mean droplet size of the PCM nanoemulsions, measured by dynamic light scattering (DLS), was correlated with the liquid content of octadecane to explain phase instability in the solid-liquid coexistence region. Quantitative 13C single-pulse NMR experiments established that the carbonyl surfactant head groups were present in multiple distinct environments during thermal cycling. After repeated thermal cycling, the 13C signal intensity of the carbonyl surfactant head groups decreased, indicating that the surfactant head groups lost molecular mobility. The results explain, in part, the origin of phase instability of PCM nanoemulsions upon thermal cycling.

Elucidation and verification of cracking behavior in additive manufacturing of alloy 718 based on fractography

This study identified a cracking that occurred continuously in the built direction of an additive manufactured part of alloy 718 by the laser metal deposition method and clarified the cracking behavior. The solidification microstructure of alloy 718 was evaluated by EDS, EPMA, and extraction residue, and it was found that Laves phase, Ti carbides, and Al oxides were formed between the dendrite microstructures. A fracture surface analysis of the cracks revealed that the cracking in the additive manufacturing was hot cracking associated with the liquid film and that the cracking occurred along the grain boundaries. The fracture surface at the beginning of the cracking showed a solidification cracking fracture surface. The experimental investigation for crack propagation during additive manufacturing and the analytical evaluation of the mechanical state around the cracking using thermal elastic-plastic analysis elucidated the cracking behavior during additive manufacturing. If the cracking exists at the fusion boundary, it is suggested that the cracking initiates from the solid-liquid interface towards the solidification direction. Moreover, tensile strain occurred around the cracks during additive manufacturing, particularly the strain was biggest at the crack edge on the fusion boundary. Therefore, the continuous cracking that occurred beyond each layer in the additive manufacturing of alloy 718 in this study can be considered solidification cracking, and its behavior can be further explained as a notch extension cracking that starts from the solidification cracking and continuously occurs in the solid-liquid coexistence temperature region.

Study on the metallurgical mechanisms of inclusions in the FGH4096 alloy during electron beam smelting

In this study, the metallurgical mechanisms of inclusions during electron beam smelting (EBS) of a FGH4096 powder superalloy was investigated. The macroscopic morphology of the ingots, as well as the composition and structure of inclusions were studied. The effect of electron beam smelting parameters on the cooling rate, O/N content, number density and size of inclusions have been revealed. Besides, the mechanisms for inclusions removal and formation were elucidated. The results show that inclusions in the final solidification zone are mainly oxides (simple tetragonal CrO2, hexagonal Al2O3, and face-centered cube TiN), whereas the complex inclusions and carbon nitrides with Al2O3 and TiN as the nucleation cores are mainly present in the matrix. With the increase in smelting power and time, both the cooling rate and O/N content decsrease, and the smelting power shows a greater impact on the cooling rate. The number density of total inclusions increases with the increase in the smelting power. As the smelting time increases, the number density of total inclusions decreases, while the size of complex inclusions and carbon nitrides increases. This is attributed to the combined effect of cooling rate and O/N concentration in the alloy under different smelting parameters. Thermodynamic calculations indicate that Al2O3 forms in the solid-liquid phase region. The precipitation of TiN occurs when the alloy solidifies, and its precipitation temperature is higher than that of TiC. The lattice mismatch between Al2O3 and TiN is 8.14%, while that between TiC and TiN is 6.94%, which effectively promotes the heterogeneous nucleation of complex inclusions and carbon nitrides. The formation mechanisms of complex inclusions and carbon nitrides provide a theoretical basis for purification of superalloys by electron beam metallurgy.

Effect of distribution shape on the melting transition, local ordering, and dynamics in a model size-polydisperse two-dimensional fluid

Abstract We study the effect of particle size polydispersity (δ) on the melting transition (T *), local ordering, solid–liquid coexistence phase and dynamics of two-dimensional Lennard–Jones fluids up to moderate polydispersity by means of computer simulations. The particle sizes are drawn at random from the Gaussian (G) and uniform (U) distribution functions. For these systems, we further consider two different kinds of particles, viz., particles having the same mass irrespective of size, and in the other case the mass of the particle scales with its size. It is observed that with increasing polydispersity, the value of T * initially increases due to improved packing efficiency (ϕ) followed by a decrease and terminates at δ ≈ 8% (U-system) and 14% (G-system) with no significant difference for both mass types. The interesting observation is that the particular value at which ϕ drops suddenly coincides with the peak of the heat capacity (CP ) curve, indicating a transition. The quantification of local particle ordering through the hexatic order parameter (Q 6), Voronoi construction and pair correlation function reveals that the ordering decreases with increasing δ and T. Furthermore, the solid–liquid coexistence region for the G-system is shown to be comparatively wider in the T–δ plane phase diagram than that for the U system. Finally, the study of dynamics reveals that polydisperse systems relax faster compared to monodisperse systems; however, no significant qualitative differences, depending on the distribution type and mass polydispersity, are observed.

Improved microstructure and mechanical properties by in-situ formed nano borides of high-Nb TiAl composites under ultrasound in the solid-liquid two-phase region

To form in situ nano-borides in the solid-liquid two-phase region, Ti46 A l8Nb2·6C0.8TaxB alloys were prepared under ultrasound to improve the microstructural and mechanical properties. The morphology and distribution of borides and the characteristics of lamellar colonies were observed with scanning and transmission electron microscopy and X-ray diffraction; these analyses revealed the influence of borides on microstructural evolution and improved strength and plasticity. The borides that form are elongated and spherical. As the B content increases, the borides gradually spheroidise, and nano-borides precipitate on the lamellar phase. There are a large number of dislocations around the borides to form stacking faults and dislocation walls. The average size of the lamellar colonies decreases from 26.9 to 19.3 μm. The increase in boride nucleation sites as the B content increases and ultrasound-mediate breaking of primary borides are the reasons for forming B27-type borides. The increase in nucleation particles refines the lamellar colony. The compressive strength increases from 2058 to 2299 MPa, and the strain increases from 25.2% to 32.3% when the addition of B increases from 0% to 1.2%. The significantly improved mechanical properties are due to uniformly distributed nano-borides that hinder the movement of dislocations to form stacking faults and dislocation walls and refinement of the lamellar colonies.

Complex oiling-out behavior of procaine with stable and metastable liquid phases.

During the crystallization of a solute from solvent(s), spontaneous liquid-liquid phase separation (LLPS) might occur, under certain conditions. This phenomenon, colloquially referred to as "oiling-out" in the pharmaceutical industry, often leads to undesired outcomes, including undesired particle properties, encrustation, ineffective impurity rejection, and excessively long process time. Therefore, it is critical to understand the thermodynamic driving force and phase boundaries of this phenomenon, such that rational strategies can be developed to avoid oiling-out or minimize its negative impact. In this study, we systematically evaluated the oiling-out behavior of procaine, a low melting point drug, in the solvent systems heptane, and ethanol-heptane as a function of temperature and solvent composition. In the procaine-heptane binary system, we observed a region where the LLPS is metastable with respect to crystallization, which is most commonly observed in the crystallization of modern active pharmaceutical ingredients (APIs); however, we also identified a region of the phase diagram where the LLPS is stable with respect to crystallization, and therefore will persist indefinitely. In the procaine-ethanol-heptane ternary system we identified five different regions, including a homogeneous liquid (L) region, two solid-liquid (SLI and SLII) regions, a liquid-liquid (LILII) region, and a solid-liquid-liquid (SLILII) region. The binary and ternary phase diagrams were also predicted using a state-of-the-art thermodynamic model: the SAFT-γ-Mie equation of state, and the results were compared with experimental data. Our findings highlight the complexity of oiling-out behavior. This work also represents a combined modeling and experimental platform to identify phase boundaries that will enable rational selection of strategies to crystallize active pharmaceutical ingredients with oiling-out risks.

Purification and Fractionation of Lignin via ALPHA: Liquid-Liquid Equilibrium for the Lignin-Acetic Acid-Water System.

In order to effectively practice the Aqueous Lignin Purification with Hot Agents (ALPHA) process for lignin purification and fractionation, the temperatures and feed compositions where regions of liquid-liquid equilibrium (LLE) exist must be identified. To this end, pseudo-ternary phase diagrams for the lignin-acetic acid-water system were mapped out at 45-95 °C and various solvent: feed lignin mass ratios (S:F). For a given temperature, the accompanying SL (solid-liquid), SLL (solid-liquid-liquid), and one-phase regions were also located. For the first time, ALPHA using acetic acid (AcOH)-water solutions was applied to a lignin recovered via the commercial LignoBoost process. In addition to determining tie-line compositions for the two regions of LLE that were discovered, the distribution of lignin and key impurities (the latter can negatively impact lignin performance for materials applications) between the two liquid phases wasalso measured. As a representative example, lignin isolated in thelignin-rich phase was reduced 7x in metals and 4x in polysaccharides by using ALPHA with a feed solvent composition of 50-55% AcOH and an S:F of 6:1, with said lignin being obtained at a yield of 50-70% of the feed lignin and having a molecular weight triple that of the feed.

Application of graded phase change materials for solar energy inter-seasonal storage heating and thermal storage characteristics

Abstract In this paper, firstly, the heat transfer characteristics of the stepped phase change accumulator are studied, and the location of the solid-liquid phase interface is determined by the phase fraction in a fixed grid scheme, while the phase change heat transfer process is simulated using Fluent. Secondly, for the phase change heat transfer problem, the enthalpy-porosity method in the Solidification/Melting model is used to treat the solid-liquid mixed paste region of the phase interface as a porous media region, and the evaluation system is constructed in terms of heat storage and discharge efficiency, heat storage, and heat recovery efficiency. Then the mathematical model, boundary conditions and solution parameters of the stepped phase change heat accumulator are set, and the data analysis of the effect of the pool height-to-diameter ratio on the heat storage in the solar inter-seasonal storage heating system is carried out by using ANSYSCFD software. The results show that the heat storage of the system also shows an overall increasing trend with the increase of the pool height-to-diameter ratio, and the heat storage of the system increases faster when the height-to-diameter ratio increases from 0.2 to 1.0 in sequence, and the heat storage of the system increases less when the height-to-diameter ratio changes between 0.9 and 1.8, and basically tends to be stable. This study realizes the graded heat storage and graded heat use of solar energy, which is useful for the research of solar heat supply and heat storage.

In-situ observation of microstructure evolution and improvement of distribution of reinforcing particles to reveal dual-enhancement mechanisms of strength and plasticity for Ti48Al2Cr2Nb3C alloy

To achieve a more uniform distribution of the reinforcing particle and then refine them, ultrasonic treatment (UT) performs in the liquid-solid two-phase region for a certain time of Ti48Al2Cr2Nb3C alloys. The influence of uniformly distributed reinforcing particle on the microstructure evolution process is revealed through in-situ observation and the mechanism of simultaneous improvement of strength and plasticity is revealed. Results show that UT effectively eliminates the B2 phase by facilitating solute diffusion. UT successfully disperses Ti2AlC agglomerations and suppresses the formation of the network γ phase. The capillary and cavitation effects induced by UT contribute to the uniform distribution of Ti2AlC, leading to a reduction in Al enrichment between Ti2AlC clusters and subsequent elimination of the network γ phase. In the as-cast alloy, the presence of extensive dislocations near Ti2AlC is attributed to melt shrinkage during solidification. A significant number of nano-twins are observed in the vicinity of Ti2AlC after UT. This transformation is facilitated by the generation of Frank-Read sources induced by UT, which promote dislocation slip and twin formation. The compressive strength and strain of Ti48Al2Cr2Nb3C exhibit notable enhancements, increasing from 2088.7 MPa to 27.6% to 2422.4 MPa and 33.0%, respectively. The uniform distribution of Ti2AlC effectively mitigates stress concentration-induced particle breakage, while the presence of twins provides protection against dislocation-induced damage. These improvements enhance the load-bearing capacity of Ti2AlC, thereby improving the mechanical properties of Ti48Al2Cr2Nb3C alloy.

Improvement of microstructure and acquirement of excellent mechanical properties of high-Nb Ti2AlC/TiAl alloy by Ta under ultrasonic action in solid-liquid zone

To promote element diffusion in the solid-liquid two-phase region, optimize solidification microstructure, and improve the matching degree of strength and toughness, Ti–46Al–8Nb-2.6C-xTa (at. %) alloys were prepared by arc melting under the action of ultrasound. The lamellar colony, precipitate phase, elements distribution, and related mechanisms were analyzed. Results show that the relative content of the γ phase decreases, while the relative content of the α2 phase and Ti2AlC phase increases as the addition of Ta increases. The coarse long rod-shaped Ti2AlC transforms into short rod-shaped particles. The lamellar colony size reduces from 32.1 to 18.6 μm, the lamellar spacing reduces from 1.4 to 0.7 μm, and the aspect ratio of Ti2AlC reduces from 5.8 to 2.5 as the addition of Ta increases from 0 to 1.0 at. %. The acoustic streaming effect of ultrasound promotes the diffusion of tantalum in the solid-liquid two-phase region for a certain ultrasonic processing time. Tantalum is a heterogeneous nucleation particle of Ti2AlC particles and causes composition supercooling at the forefront of the solidification interface, which is the main reason for refining the microstructure. Compressive strength increases from 1996 to 2596 MPa and the strain increases from 25.4 to 29.3% as the addition of Ta increases from 0 to 0.6 at. %. The main reasons for improving the properties of alloy are the refinement of the microstructure and the formation of a large number of dislocations.

Molecular dynamics simulation of the evaporation of thin liquid sodium film on the conical nanostructure surface

Deeply understanding the evaporation of the nanoscale thin liquid film on the nanostructure substrates is significant for further constructing the novel wick structure with nanostructure surfaces, which would be used in the optimal design of the sodium heat pipe. For this purpose, this paper investigates the evaporation of thin liquid film on conical nanostructured surfaces by the molecular dynamics method. A cuboid evaporation system is constructed. It consists of the bottom solid substrate and thin liquid sodium film. A flat solid wall is set as the reference. By changing the nanoscale cone's number and height, five conical nanostructure surfaces are built. The number of gas atoms and the total energy of fluid atoms are observed respectively. The evaporation rate and the average heat flux (q) of six cases are compared. The conical nanostructure suppresses evaporation. With the roughness of the conical nanostructures, the evaporation rate decrement maximum can reach 83% and the q decrement maximum can reach 58%. Based on the thermal resistances in the solid-liquid contact region, the D (Self-diffusion coefficient), and the peak values of RDF (Radial distribution function), the mechanisms of the conical nanostructure surfaces are analyzed. The suppressing effects of the conical nanostructure surfaces are achieved by weakening the heat conduction in the solid-liquid contact region and mitigating the collision heat transfer of liquid atoms.

Migration Behavior of Inclusions at the Solidification Front in Oxide Metallurgy.

Distribution of inclusions plays an essential role in inducing intracrystalline ferrite, and the migration behavior of inclusions during solidification has a significant influence on their distribution. The solidification process of DH36 (ASTMA36) steel and the migration behavior of inclusions at the solidification front were observed in situ using high-temperature laser confocal microscopy. The annexation, rejection, and drift behavior of inclusions in the solid-liquid two-phase region were analyzed, providing a theoretical basis for regulating the distribution of inclusions. Analysis of inclusion trajectories showed that the velocity of inclusions decreases significantly as they near the solidification front. Further study of the force on inclusions at the solidification frontier shows three situations: attraction, repulsion, and no influence. Additionally, a pulsed magnetic field was applied during the solidification process. The original dendritic growth mode changed to that of equiaxed crystals. The compelling attraction distance for inclusion particles with a diameter of 6 μm at the solidification interface front increased from 46 μm to 89 μm, i.e., the effective length for the solidification front engulfing inclusions can be increased by controlling the flow of molten steel.

The evaporation of nanoscale sodium liquid film on the non-ideal nanostructure surface: A molecular dynamics study

The nanoscale liquid sodium film inside the microporous wick structure is of great importance to understanding the evaporation mechanism of the sodium heat pipe. The novel optimized wick structure is made of several layers of special screen. The surface of each screen exhibits a nanostructure type. Some non-ideal nanostructures may result from experimental faults or limits. And they will have an effect on the evaporation of film. In the present study, molecular dynamics is adopted to investigate this effect. The simulation system consists of the liquid sodium film and the solid surface. The flat surface is set as the reference. Based on the three non-ideal shapes of deposition, the sinusoidal nanostructures, conical nanostructures, and spherical nanostructures are built. The results indicate that the evaporation is suppressed by the above nanostructure surfaces. The weakening effect is through three forms: the potential gradient of the liquid film is intensified and the evaporation difficulty is increased; the heat transfer in the solid-liquid contact region is impeded; the collision heat transfer inside the liquid film is affected due to the delay of the aggregation variation between liquid atoms.

Based on Phase Change Materials of Research on Compressor Tip Clearance Control

The reduction of tip clearance height of the compressor has an important influence on the improvement of compressor efficiency. The goal of tip clearance control technology is to reduce clearance height. Firstly, the phase change principle of phase change materials is analyzed. Under temperature excitation, when the phase change material is in the solid-liquid two-phase region, the volume of the phase change material will change with temperature. A phase change mechanism for tip clearance control was developed, and the clearance control scheme was designed. Finally, the feasibility of the gap control scheme is verified by the gap control function experiment.

A molecular dynamics approach to investigate effect of pressure on asphaltene self-aggregation

Asphaltene aggregation is a serious issue in the oil industry that negatively affects the production, transportation, and exploitation of oil, causing considerable costs. In the past few years, the experimental analysis of asphaltene aggregation has been a fascinating topic; however, a laboratory study that can assess the asphaltene aggregation behaviors at high pressures will be a costly and high-risk project. In this paper, molecular dynamics (MD) simulations are used to investigate the influence of pressure on the asphaltene aggregation phenomenon. The employed asphaltene in this research is Gachsaran asphaltene (obtained from an Iranian oilfield) with archipelago geometry. The aggregation number, radial distribution function (RDF), potential of mean force (PMF), cohesive energy, solubility parameter, mean square displacement (MSD), diffusion coefficient, relative concentration, potential energy, and radius of gyration are analyzed based on the data and results obtained from the output trajectory files. It is concluded that the number and the average size of asphaltene aggregates significantly decrease with increasing pressure because the pressure delays the growth of asphaltene aggregates by enhancing the asphaltene solubility parameter. The associated energies of asphaltene molecules at 35, 90, and 135 bar are calculated to be −15.7834, −15.7571, and −15.7249 kJ / mol, respectively. It is found that the tendency of asphaltene molecules to aggregate reduces upon an increase in pressure. Face-to-face interactions are more likely than T-shaped and offset stacking for this asphaltene sample because of the more aromatic nuclei in the asphaltene structure than the aliphatic chains, which increase the strength of the π-π interactions. It is also observed that by increasing pressure, the movement and vibration of asphaltene increase and then decrease by further increase in pressure. According to the asphaltene onset envelope diagram, the asphaltene molecules at 35 bar are located in the solid–liquid region. As the pressure increases to 90 bar, the asphaltene passes the upper asphaltene onset point zone. It can be concluded that when asphaltene is in the solid–liquid region, the mobility and displacement of molecules increase with increasing pressure. In the upper asphaltene onset point zone, the tendency of molecules to move is reduced. The MD results are consistent with the laboratory data.

Parametric study for the induced electric current of an electromagnetically driven flow

In this work, the electric scalar and the magnetic vector potential magnetohydrodynamic formulations are implemented in the COMSOL Multiphysics software for the simulation of an electrovortex flow in a cuboid vessel. The flow is generated by a Lorentz force produced by the interaction of a direct electric current, which is injected through two solid electrodes located on the top and bottom of the vessel and an external magnetic field generated by one or a pair of permanent magnets. A good comparison between numerical and experimental velocity profiles reported by the workgroup is observed. The induced electric current fields obtained from Ohm's and Ampere's laws are explored in the solid electrodes and liquid metal regions. A parametric study for the interaction parameter in the range of 1 ≤ N ≤ 50 is presented. For both formulations, the same induced electric current distributions were obtained. Interestingly, for a pair of magnets, the induced electric current distribution is symmetric and the penetration of its main component into the solid electrodes increases with N, whereas for one single magnet, the induced current is non-symmetric and its penetration is small. Results also indicate that depending on the MF there are zones, where the induced electric current is small and the velocity is high. For a pair of magnets, this behavior is observed close to the interface of the LM-solid electrodes. Tables 2, Figs 10, Refs 43.

Selective separation and recovery of selenium from copper anode slime by compound leaching followed by sulfate roasting

In this research, selenium was selectively separated and recovered from copper anode slime by a hydrometallurgical-pyrometallurgy union process. In the first compound leaching process with H2SO4, HCl and NaCl media, the pre-removal of As, Sb, and Bi was achieved, and the removal efficiencies were 85 %, 83 %, and 91 %, respectively. Selenium was effectively enriched by approximately 200 % after first compound leaching. Sulfate roasting method was used to selectively separate selenium in the second stage. In this study, more than 99.39 % of selenium was separated with concentrated sulfuric acid amount to first leaching residues ratio (H2SO4/ first compound leaching residues ratio) of 0.30 mL/g at 500 °C for 25 min, which enabled selenium to be selectively separated from the other elements. The kinetics of sulfation roasting of Se-enriched residues show that the selective separation of selenium conforms to the Avrami multiphase liquid–solid region reaction, the activation energy of the reaction is 28.118 kJ/mol, and the reaction efficiencies equation is k = 3.607e-3382/T, indicating that it is internal diffusion-controlled.

Examination of the cerium α-ε phase transition under dynamic loading with x-ray diffraction

Recent examination of the cerium Hugoniot with pyrometry and x-ray diffraction (XRD) has revealed a narrow solid-liquid two-phase region. It has been suggested that nonequilibrium melting may be occurring along the Ce Hugoniot, with either melt kinetics or a sluggish \ensuremath{\alpha}-\ensuremath{\epsilon} transition impeding the transition. In particular, the kinetics of the \ensuremath{\alpha}-\ensuremath{\epsilon} is unknown and the location of the phase boundary is in dispute. Static measurements suggest a nearly vertical phase boundary that intersects the Hugoniot at 6--7 GPa. This lies in direct conflict with dynamic measurements along the Hugoniot observing \ensuremath{\alpha}-Ce through incipient melt. This work presents dynamic experiments using XRD to examine the behavior of the \ensuremath{\alpha}-\ensuremath{\epsilon} phase transition. The results show that the \ensuremath{\alpha}-\ensuremath{\epsilon} phase transition occurs through a tetragonal distortion, with the transition beginning at temperatures below the solid Hugoniot. Following the initial deviation from an ideal fcc structure, the $c/a$ ratio is found to gradually increase with no steady value observed in the \ensuremath{\epsilon} phase within the range of these experiments (below 17 GPa). Multiple diffraction patterns captured during the peak stress state show no significant change in $c/a$ ratio prior to uniaxial release, upon which Ce reverts to an fcc structure. The results indicate that the \ensuremath{\alpha}-\ensuremath{\epsilon} transition occurs rapidly, both on loading and release. An examination of the $c/a$ ratio with increasing temperatures suggests 11.5 GPa as a lower bound for the location of the \ensuremath{\alpha}-\ensuremath{\epsilon}-liquid triple point.

Effect of testing conditions on the nanomechanical behavior of surface and inner core of as-cast Zr-base bulk metallic glassy plates

We report the effect of testing conditions on the nanomechanical behavior of the surface and inner core of as-cast plates of Zr41·2Ti13·8Cu12·5Ni10Be22.5, Zr52·5Cu18Ni14·5Al10Ti5, Zr58·5Cu15·6Ni12·8Al10·3Nb2.8 and Zr55Cu30Ni5Al10 bulk metallic glasses (BMGs). A series of instrumented nanoindentation experiments have been performed under control loading rate (CLR) mode at various maximum applied load (Pmax) in between 100 and 500 mN, and under control strain rate (CSR) mode at strain rates in between 0.001 and 1.0/s at Pmax = 500 mN on length-width (LW) surface and thickness-width (TW) inner core of 2 mm thick as-cast plates. The solid-liquid like regions in the glassy structure affects the deformation mechanism of BMGs as the liquid like regions triggers the activation of the shear transformation zones (STZs), which promotes formation of shear bands at various testing conditions. The nano-micromechanical behavior has been evaluated in terms of indentation size effect (ISE), strain rate sensitivity (m) and activation volume (V*) under CLR and CSR modes for LW and TW planes. The effect of testing conditions on the rate sensitivity and deformation mechanism have been discussed in terms of size and dynamics of STZs by considering the presence of solid-liquid like regions in the glassy structure. It has been noticed that hardness and rate sensitivity values have decreased and STZ size has increased with increasing Pmax for both the planes of all the studied BMGs.

Thermal transport mechanism at a solid-liquid interface based on the heat flux detected at a subatomic spatial resolution.

Heat flux is a fundamental quantity in thermal science and engineering and is essential for understanding thermal transport phenomena. In this study, the heat flux in a solid-liquid interfacial region is obtained in a three-dimensional (3D) space at a subatomic spatial resolution based on classical molecular dynamics, yielding a 3D structure of the heat flux between the solid and liquid layers in contact. The results using the Lennard-Jones potential reveal the directional qualities of the heat flux, which are significantly dependent on the subatomic stresses in the structures of condensed phase systems. The heat flux and stress at the subatomic scale are related to the macroscopic transport quantities, which can be obtained using distribution functions; the stress and energy flux properties at the subatomic scale are comprehensively investigated using a single-interaction-based stress and energy flux to determine the origin of the thermal transport mechanism at the solid-liquid interface. The findings reveal that the density of states due to the stress caused by a single interaction exhibits a bandlike behavior. The net energy transport comprises positive and negative energy transport inside and outside the band. In addition, this is related to the intrinsic transport property of the atoms and molecules at the solid-liquid interface at the subatomic scale. The difference between the energy transport rates when a solid atom in the vicinity of the interface is near to or far from the liquid phase is the origin of the energy transport mechanism at the solid-liquid interface. 3D analysis of the heat flux and stress is carried out by varying the interaction strengths between the liquid molecules and solid atoms at the solid-liquid interface. This reveals that the directional quality of transport quantities is high at strong interaction strengths, thus indicating enhanced thermal transport. Furthermore, the influence of the temperature gradient in the system suggests that the energy transport imbalance between inside and outside the stress band in a high-stress field at the subatomic scale induces the net thermal transport across the interface in the nonequilibrium state.