Phase Volume Research Articles

Chemical reactions regulated by phase-separated condensates

Phase-separated liquid condensates can spatially organize and thereby regulate chemical processes. However, the physicochemical mechanisms underlying such regulation remain elusive as the intramolecular interactions responsible for phase separation give rise to a coupling between diffusion and chemical reactions at nondilute conditions. Here, we derive a theoretical framework that decouples the phase separation of scaffold molecules from the reaction kinetics of diluted clients. As a result, phase volume and client partitioning coefficients become control parameters, which enables us to dissect the impact of phase-separated condensates on chemical reactions. We apply this framework to two chemical processes and show how condensates affect the yield of reversible chemical reactions and the initial rate of a simple assembly process. In both cases, we find an optimal condensate volume at which the respective chemical reaction property is maximal. Our work can be applied to experimentally quantify how condensed phases alter chemical processes in systems biology and unravel the mechanisms of how biomolecular condensates regulate biochemistry in living cells. Published by the American Physical Society 2024

The Entropy of Mixing in Self-Assembly and the Role of Surface Tension in Modeling the Critical Micelle Concentration

A theory for the micelle formation of nonionic head-tail amphiphiles (detergents) in aqueous solutions is derived based on the traditional molecular thermodynamic modeling approach and a variant of the Flory–Huggins theory that goes beyond lattice models. The theory is used to analyze experimental values for the critical micelle concentration of n-alkyl-ß-D-maltosides within a mass action model. To correlate those parts of the micellization free energy, which depend on the transfer of hydrophobic molecule parts into the aqueous phase, with molecular surfaces, known data for the solubility of alkanes in water are reanalyzed. The correct surface tension to be used in connection with the solvent-excluded surface of the alky tail is ~30 mN/m. This value is smaller than the measured surface tension of a macroscopic alkane–water interface, because the transfer free energy contains a contribution from the incorporation of the alkane or alkyl chain into water, representing the change in free volume in the aqueous phase. The Flory–Huggins theory works well, if one takes into account the difference in liberation free energy between micelles and monomers, which can be described in terms of the aggregation number as well as the thermal de Broglie wavelength and the free volume of the detergent monomer.

Quality by Design Approach Driven Development and Validation of Reverse Phase‐High‐Performance Liquid Chromatography Methodology for Dual Quantification of Aspirin and Rivaroxaban

ABSTRACTClinical trials have shown that combining a modest dose of Rivaroxaban (RIV) with Aspirin (ASP) is more effective than ASP alone in reducing cardiovascular mortality, myocardial infarction, and stroke. A high‐performance liquid chromatography method developed using Quality by Design (QbD) effectively estimates ASP and RIV for routine pharmaceutical analysis. The Plackett‐Burman design assessed key factors including organic phase volume, mobile phase pH, flow rate, temperature, and injection volume using an Ishikawa fish‐bone diagram for risk assessment. These parameters were then optimized via Box‐Behnken design in 15 trials. The method meets the International Council For Harmonization standards with a mobile phase ratio of 45:55 (v/v) acetonitrile: buffer (pH 3, adjusted with orthophosphoric acid), a flow rate of 1 mL/min, a column temperature of 30°C, and an injection volume of 20 µL. A Phenomenex Luna C18 column (250 × 4.6 mm, 5 µm particle size) with detection at 251 nm ultra‐violet wavelength. The retention times of 4.54 min for ASP and 5.81 min for RIV were obtained. Validation confirmed linear ranges: 40–200 µg/mL for ASP and 2–10 µg/mL for RIV, with excellent recovery rates (ASP: 99.30%–101.9%; RIV: 98.52%–101.84%). Developed using QbD principles, the method proved specific, accurate, precise, sensitive, and robust for routine quality control of both compounds in pharmaceutical formulations.

Molecular Dynamics Simulation of the Viscosity Enhancement Mechanism of P-n Series Vinyl Acetate Polymer–CO2

Carbon dioxide (CO2) drive is one of the effective methods to develop old oil fields with high water content for tertiary oil recovery and to improve the recovery rate. However, due to the low viscosity of pure CO2, it is not conducive to expanding the wave volume of the mixed phase, which leads to difficulty utilizing the residual oil in vertical distribution and a low degree of recovery in the reservoir. By introducing viscosity enhancers, it is possible to reduce the two-phase fluidity ratio, expanding the degree of longitudinal rippling and oil recovery efficiency. It has been proven that the acetate scCO2 tackifier PVE can effectively tackify CO2 systems. However, little research has been reported on the microscopic viscosity enhancement mechanism of scCO2 viscosity enhancers. To investigate the influence of a vinyl acetate (VAc) functional unit on the viscosity enhancement effect of the CO2 system, PVE (Polymer–Viscosity–Enhance, P-3) was used as the parent, the proportion of VAc was changed, and the molecules P-1 and P-2 were designed to establish a molecular dynamics simulation model for the P-n-CO2 system. The molecules in the system under the conditions of 70 °C-10 MPa, 80 °C-10 MPa, and 70 °C-20 MPa were simulated; the viscosity of the system was calculated; and the error between the theoretical and simulated values of the viscosity in the CO2 system was relatively small. The difference between P-n molecular structure and system viscosity was analyzed at multiple scales through polymer molecular dynamics simulations and used the molecular radial distribution function, system density, accessible surface area, radius of gyration, minimum intermolecular distance, and minimum number of intermolecular contacts as indicators. This study aimed to elucidate the viscosity enhancement mechanism, and the results showed that the higher the proportion of VAc introduced into the molecules of P-n-scCO2 viscosities, the larger the molecular amplitude, the larger the effective contact area, and the greater the viscosity of the system. Improvement in the contact efficiency between the ester group on the P-n molecule and CO2 promotes the onset of solvation behavior. This study on the microscopic mechanism of scCO2 tackifiers provides a theoretical approach for the design of new CO2 tackifiers.

Phase‐separated Droplets Can Direct the Kinetics of Chemical Reactions Including Polymerization, Self‐replication and Oscillating Networks

AbstractPhase‐separated compartments can localize (bio)chemical reactions and influence their kinetics. They are believed to play an important role both in extant life in the form of biomolecular condensates and at the origins of life as coacervate protocells. However, experimentally testing the influence of coacervates on different reactions is challenging and time‐consuming. We therefore use a numerical model to explore the effect of phase‐separated droplets on the kinetics and outcome of different chemical reaction systems, where we vary the coacervate volume and partitioning of reactants. We find that the rate of bimolecular reactions has an optimal dilute/coacervate phase volume ratio for a given reactant partitioning. Furthermore, coacervates can accelerate polymerization and self‐replication reactions and lead to formation of longer polymers. Lastly, we find that coacervates can ‘rescue’ oscillating reaction networks in concentration regimes where sustained oscillations do not occur in a single‐phase system. Our results indicate that coacervates can direct the outcome of a wide range of reactions and impact fundamental aspects such as yield, reaction pathway selection, product length and emergent functions. This may have far‐reaching implications for origins of life, synthetic cells and the fate and function of biological condensates.

Ethyl levulinate regulates traditional sulfolane biphasic absorbent for energy-efficient CO2 capture

Traditional CO2 biphasic absorbents currently suffer from problems such as high initial phase separation loading, poor product distribution selectivity, and weak dynamic phase separation ability, which limit their potential for industrial applications. This study developed a biphasic absorbent regulated by dual physical solvents by introducing partial ethyl levulinate (EL) into a sulfolane biphasic system. The optimal composition of this system was 30 wt% 1-amino-2-propanol (MIPA), 20 wt% sulfolane and 30 wt% EL. Under dual physical solvent conditions, strong electrostatic attraction between MIPA and CO2 promoted generation of MIPA zwitterions and carbamate. Analysis of the interactions between different product components through electrostatic potentials and with an independent gradient model based on Hirshfeld's partitioning revealed only extremely weak van der Waals force-driven interactions between the reaction products and EL. These interactions substantially reduced the initial phase separation loading and offered precise control over phase transition behavior. Compared with MIPA/sulfolane system, the MIPA/sulfolane/EL system achieved a 48.9 % lower initial phase separation loading, an 11.6 % lower proportion of saturated rich phase volume, a 10.1 % higher CO2-rich phase loading, and a 6.7 % lower viscosity. The excellent dynamic phase separation performance was verified using a customized device and the energy consumption for CO2 regeneration decreased to 2.2 GJ/t CO2.

Differentiate adrenal lipid-poor adenoma from nodular hyperplasia with CT quantitative parameters: a feasibility study.

To explore the potential of CT quantitative parameters in differentiating adrenal lipid-poor adenoma (LPA) from nodular hyperplasia and evaluate diagnostic performance. Patients with LPA or nodular hyperplasia who underwent contrast-enhanced CT before adrenalectomy were analyzed retrospectively. The study included 128 patients (83 with LPA and 45 with nodular hyperplasia). Each lesion's unenhanced attenuation, portal-venous phase attenuation (CTp), and the portal-venous phase attenuation of the abdominal aorta were evaluated. We subsequently calculated absolute enhancement [a lesion's portal-venous phase attenuation minus unenhanced attenuation (in HUs)], relative enhancement (absolute enhancement divided by unenhanced attenuation), and the relative enhancement ratio [(absolute enhancement divided by abdominal aorta's portal-venous phase attenuation) ×100%]. Lesion number and size were recorded. Volume was assessed by ITK-snap software and the ratio of lesion volume to ipsilateral adrenal volume (volume ratio) was determined. Intergroup differences were analyzed using Student's t-test and chi-squared test. Logistic regression models were developed, and receiver operating characteristic (ROC) curves were constructed to determine the area under the ROC curve (AUC), sensitivity, and specificity. The model's performance was then compared against radiologists' subjective assessments, and the inter- and intra-reader agreement values among radiologists were calculated. Portal-venous phase attenuation, volume ratio, and lesion number were independent predictors of LPA. The logistic regression model incorporating CTp, volume ratio, and lesion number achieved an AUC of 0.835, with a sensitivity of 73.5% and a specificity of 80.0%. The radiologists' diagnostic specificity and accuracy appeared to be inferior to the model. The inter-reader agreement among radiologists ranged from 0.082 to 0.535, and the intra-reader agreement of two radiologists were 0.734 and 0.583. The portal-venous phase CT demonstrated potential in distinguishing LPA from nodular hyperplasia. The diagnostic performance of the model integrating CTp, volume ratio, and lesion number outperformed radiologists in terms of variability and reproducibility.

Effect of Recycled Asphalt Mixture and Solid Waste-Based Solidification Materials on Performance of Cold-Regenerated Asphalt Mixture

In this study, an aging asphalt mixture was regenerated by a waste-based rejuvenator and cemented by solid waste-based solidification materials (SSMs). A splitting test, wheel tracking test, and three-point bending test were conducted to evaluate the properties of the regenerated asphalt mixture (RAM). The results reveal that the properties of the asphalt mixture were not diminished or were moderately enhanced by the 30% substitution of RAP. With the substitution of RAP to 100%, the splitting tensile strength, dynamic stability, and splitting strength ratio were decreased by 13%, 15%, and 5%, respectively. With the 100% substitution of SSMs for cement, the compressive strength, dynamic stability, flexural strain, and splitting strength ratios of the RAM were increased by 40%, 32%%, 14%, and 8%, respectively. The lightweight components can be supplemented, and low-temperature deformation and interlayer flowability can be improved by the incorporation of the rejuvenator. The generation of hydrated calcium silicate and ettringite for SSMs is greater than those of cement. The massive generation of ettringite has been observed to increase the solid phase volume by 120%, which may facilitate a more complete filling of the remaining pores in the RAM due to water evaporation. The regeneration and cement on green and the high performance of the rejuvenator and the SSM markedly enhanced RAM performance.

Numerical Analysis of A Two-Phase Turbine: A Comparative Study Between Barotropic and Mixture Models

Abstract Two-phase turbines offer the potential to significantly enhance the performance of power generation and refrigeration systems. However, their development has been hindered by comparatively lower efficiencies resulting from additional loss mechanisms absent in single-phase turbines. To date, most multiphase CFD studies on turbomachinery have focused on condensation in the final stages of steam turbines, and on cavitation in hydraulic pumps and turbines. These applications, however, are not representative of the conditions in two-phase turbines, where a liquid-dominated mixture undergoes a large expansion ratio, leading to a significant increase in the gas phase volume fraction throughout the entire flow. This paper aims to identify a suitable modeling methodology for two-phase turbines. Our evaluation is centered around two models: the mixture model and the barotropic model. The validity and accuracy of these two modeling approaches is assessed using existing experimental data from a single-stage impulse turbine operating with several mixtures of water and nitrogen as working fluid. The results indicate that both the mixture and barotropic models are consistent and accurately predict the nozzle mass flow rate, yet, both models systematically overpredict the nozzle exit velocity and rotor torque. Adding correction terms for windage and unsteady pumping losses significantly improves the torque predictions, bringing them within the uncertainty range of the experimental data. In addition, refining the models to account for the effect of slip presents a promising avenue to enhance the prediction of nozzle exit velocity and overall performance of two-phase turbines.

Hot extrusion, tensile deformation behavior and deformation mechanism analysis of a wrought superalloy with a high γ′ phase volume fraction of 64 %

A hundred kilograms of GH4975 extrusion bar, featuring fine equiaxed grains, were successfully fabricated using electron beam smelting layer solidification(EBSL) and hot extrusion techniques. Subsequent analysis focused on the microstructure and tensile properties of the extruded bar. The study also delved into the influence of temperature on tensile deformation behavior and mechanisms of the alloy after standard heat treatment(SHT). The results revealed uniformity in precipitated phase size and morphology across the extruded bar, with grain size being the largest at the center and smallest at the edge. Tensile tests conducted at 20 °C and 650 °C show an obvious work hardening phenomenon, and the deformation mechanism is dominated by APB coupled dislocation pairs shearing. With the increase of deformation temperature, the work-hardening phenomenon gradually weakens, and SFs emerge as the primary deformation mechanism at 750 °C. As the deformation temperature further rises, cross slip, Orowan bypass and dislocation climbing gradually dominate. The fracture mode changes from brittle fracture to ductile and brittle mixed fracture, and ultimately to brittle fracture. Compared with the traditional preparation method, the hundred kilograms of GH4975 extrusion bar prepared by this technology still show better mechanical properties.

Phase volume correlation approach for overcoming decorrelation in three-dimensional phase-sensitive optical coherence elastography

The dynamic measurement range in phase-sensitive optical coherence elastography (PhS-OCE) is limited for the phase decorrelation induced by pixel-level displacements in precision measurement, where the consideration of the time-resolved incremental method and in-plane pixels tracking method is insufficient to recover the phase holistically. This work presented a phase volume correlation (PVC) approach to handle the phase decorrelation in three-dimensional PhS-OCE. By utilizing the ability of the discontinuous source diagram to quantify voxel phase correlation levels, the PVC establishes a wrapped phase-matching equation aimed at optimizing the number of volumetric source distributions. The three-dimensional pixel-level motions in the deformed phase space can be evaluated by solving the optimization model for phase matching, thereby enabling the reconstruction of the volumetric phase variation corrupted by decorrelation. The large deformations experiments including diffident loadings, i.e., stretching, three-point bending, and light-cured, verified the proposed PPVC approach's of feasibility, reliability, and stability. The contribution of this work can dramatically enhance the dynamic measuring range in three-dimensional PhS-OCE.

Study on the effect of Lorentz force on the nuclear reactor core melt stratification in electromagnetic cold crucible

To understand the effect of the Lorentz force on core melt stratification during experiments, a multi-physical field coupling model of electromagnetic induction, non-isothermal flow, and two-phase flow is established in this paper. The evolution of the layered core melt in the electromagnetic cold crucible is studied for different relative densities and phase volume fraction ratios between metal and oxide. The calculation results show that the coupling model can accurately describe the structural evolution of core melt. The Lorentz force cannot change the relative positions of the metal and oxide, but it can significantly affect the morphology of the core melt. If the density of the metal is less than that of the oxide, the Lorentz force causes the light metal with a small phase volume fraction to form a hemispherical shape in the top center of the crucible. As the phase volume fraction increases, the Lorentz force become weaker than those of gravity and buoyancy. The light metal is then flat. When the metal density is greater than the oxide density, the Lorentz force causes the heavy metal with a small phase volume fraction to appear as a hemisphere, but causes the heavy metal with a large phase volume fraction to appear as an ellipsoid in the lower part of the crucible.

Effect of salt and alkali on the viscoelastic behavior of noodle dough sheet with different wheat starch granule sizes

The underlying mechanisms of salt and alkali on the viscoelastic behaviors of noodle dough sheets with varied B/A-type starch ratios were investigated from water state, protein polymerization and conformation, and microstructure. The viscoelastic behaviors of dough sheets increased with increasing B/A-type starch ratio, regardless of the presence of salt and alkali, indicating the addition of salt and alkali did not change the effect law of starch granule size on dough viscoelasticity. The viscoelastic moduli of dough decreased in the presence of salt and alkali, and the effect was more obvious as the ratio of B/A-type starch decreased, which was mainly determined by the interactions of protein-protein, protein-starch, and starch-starch in dough systems. In the low ratio of B/A-type starch dough sheets, NaCl enhanced the non-covalent interactions and β-sheet structure, while alkali promoted the covalent cross-linking of protein. In the high ratio B/A-type starch dough samples, the big starch surface area provided by a high phase volume of starch granules led to the domination of starch-starch interactions over the protein phase, thus determining the viscoelastic behavior of dough. SEM images showed that NaCl caused the gluten to form a fibrous structure, while alkali induced a membrane-like and more closed structure. NaCl and alkali showed different influences on water distribution, molecular conformation, and network structure of dough sheets with varied B/A-type starch ratios and thus contributed to the different viscoelastic behaviors.

Enhanced emulsification properties of microalgae protein through gellan gum conjugation: Mechanistic insights and applications in curcumin encapsulation and delivery

The emulsification properties of microalgae protein (MP) are poor, especially under acidic and neutral conditions, which may limit the broad applications of MP in food processing. This study aims to explore the effects of gellan gum (GG) on the emulsification properties of MP. Firstly, MP-GG complexes were prepared and their structures characterized. Subsequently, MP-GG complexes stabilized emulsions were prepared and their stability evaluated. Finally, these emulsions were employed for the encapsulation and delivery of curcumin to evaluate their potential as an efficient nutrient delivery medium. Results indicated that MP-GG complexes were formed under various pH conditions, with pH 6 identified as optimal for complexes stability (zeta-potential value was −31 mV). UV–vis and fluorescence spectroscopy demonstrated that GG did not significantly alter the MP's structure but induced slight conformational changes, leading to the burial of some amino acid residues. Zeta potential measurements confirmed that MP-GG complexes were stabilized by strong electrostatic repulsions. The increase of GG content was conducive to providing more negative charge and promoting the dissolution and dispersion of the MP-GG complexes (MP: GG = 1: 1). Emulsions stabilized by MP-GG complexes exhibited smaller droplet sizes and improved stability compared to those stabilized by MP alone, especially at oil phase volume fractions of 60 % and 70 %. Rheological analysis indicated that GG enhanced emulsion stability by increasing viscosity, and higher oil phase volume fractions facilitated better MP-GG complexes adsorption on oil droplets, strengthening network structures of emulsions. During in vitro simulated gastrointestinal digestion, emulsions with a 70 % oil phase exhibited higher curcumin retention rate (31.09 %) and lower curcumin bioaccessibility (13.23 %) compared to those with a 60 % oil phase. This suggests that emulsions with higher oil phase volume fractions may be more suitable for colon-targeted curcumin delivery, with potential applications in promoting colon health. These findings confirm that the complexation of MP and GG was an effective way to improve the emulsification properties of MP. Emulsions stabilized by MP-GG complexes can serve as stable nutritional delivery systems for fat-soluble bioactive compounds.

Smart self-assembled polymeric-MMT/Moringa Oleifera L. particles by solvent replacement method

Obesity, stemming from metabolic syndrome and energy imbalance, is a common health concern characterized by excess energy consumption and fat buildup. Moringa Oleifera L. (MO), known for its anti-obesity properties, is extracted via Soxhlet extraction. MO is extracted using the Soxhlet extraction method. To evaluate the antioxidant properties of MO powder, several analyses were conducted, including the assessment of total phenolic content (TPC), total flavonoid content (TFC), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) activity, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) activity. The TPC and TFC, DPPH activity, and ABTS activity values were determined to be 386.7 mg GAE/g and 82.33 mg QE/g, 32.86 %, and 49.4 % respectively. To improve drug delivery, the freeze-dried MO powder was encapsulated within a polymeric carrier, poly(e-caprolactone) (PCL). Moreover, the incorporation of montmorillonite (MMT) into the MO-loaded PCL nanoparticles enhanced the encapsulation efficiency and drug loading of MO. Nanoprecipitation was employed as a method to produce the nanoparticles, and the effects of four key parameters were studied: the ratio of aqueous phase volume to organic volume (1.5 – 10), stirring speed (400 rpm – 1200 rpm), mass weightage of MO (1 % -5 %), and mass weightage of MMT (2 % - 5 %). Design Expert was utilized for full factorial analysis to assess the impact of these parameters on encapsulation efficiency and drug loading. The optimal formulation was achieved at the ratio of aqueous phase volume to the organic volume of 1.5, stirring speed of 400 rpm, mass weightage of MO at 1 %, and mass weightage of MMT at 5% The expected encapsulation efficiency is 91.33 % and drug loading is 6.49 %.

Effects of lanthanides on the structure and oxygen permeability of Ti-doped dual-phase membranes

The trade-off effect of the oxygen permeability and stability of oxygen transport membranes (OTMs) still exists in working atmospheres containing CO2. Herein, we reported a new series of 60 wt%Ce0.9Ln0.1O2-δ-40 wt%Ln0.6Sr0.4Fe0.9Ti0.1O3-δ (CLnO-LnSFTO, Ln = La, Pr, Nd, Sm, Gd, Tb) dual-phase OTMs by selecting different Ln elements based on the reported highly stable Ti-doped CPrO-PrSFTO. The effects of different Ln elements on the structure and oxygen permeability of Ti-doped dual-phase OTMs were systematically studied. Basically, as the atomic number of Ln elements increases, the unit cell parameters of both the fluorite phase and the perovskite phase become smaller. The unit cell volume and spatial symmetry of the perovskite phase are reduced, resulting in a reduction in oxygen permeability. The optimal CLaO-LaSFTO showed JO2 of 0.60 and 0.54 mL min−1 cm−2 with He and CO2 sweeping at 1000 °C, respectively. In addition, all CLnO-LnSFTO OTMs could work for more than 100 h with no significant performance degradation in a CO2 atmosphere, maintaining excellent stability. This work explores candidate OTM materials for CO2 capture and oxygen separation, as well as provides some ideas for addressing the trade-off effect.

Implications of in-ice volume scattering for radio-frequency neutrino experiments

Over the last three decades, several experimental initiatives have been launched with the goal of observing radio-frequency signals produced by ultra-high energy neutrinos (UHEN) interacting in solid media. Observed neutrino event signatures comprise impulsive signals with duration of order the inverse of the antenna+system bandwidth (∼10 ns), superimposed upon an incoherent (typically white noise) thermal noise spectrum. Whereas bulk volume scattering (VS) of radio-frequency (RF) signals is well-studied within the radio-glaciological communities, polar ice-based neutrino-detection experiments have thus far neglected VS in their signal projections. As discussed herein, coherent volume scattering (CVS, for which the phase of the incident signal is preserved during scattering) generated by in-ice neutrino interactions may similarly produce short-duration signal-like power, albeit with a slightly extended time structure, and thereby enhance neutrino detection rates, whereas incoherent (randomized phase) volume scattering (IVS) will persist for O(100 ns), appearing similar to thermal white noise and therefore reducing the measured Signal-to-Noise Ratio (SNR) of neutrino signals. Herein, we present the expected voltage profiles resulting from in-ice volume scattering as a function of the molecular scattering cross-section, for both CVS and IVS, and assess their impact on UHEN experiments. VS contributions are currently only weakly constrained by extant data; stronger limits may be obtained with dedicated calibration experiments.

Enhancing oxidation resistance of silicon nitride using a Ca2+ stabilizer

Silicon nitrides are widely used in ceramic heaters for combustion engines due to their high strength and wear resistance. However, their poor oxidation resistance at elevated temperatures limits their reliability. Oxidation products, such as silica and intermediate compounds from sintering additives, often suffer from microcracks due to phase transformation and volume expansion mismatch during thermo-mechanical cycles. Use of cation dopants to chemically stabilize the transformation of the oxidation front is proposed. This study investigated the effect of Ca2+ treatment on Si3N4 with MgO and Y2O3 sintering aids. The Si3N4 samples were coated with CaO and the phase composition, microstructure, and chemical distribution of the oxidation products were analyzed using XRD, SEM, TEM, STEM, and EDS. The oxidation coupon tests revealed that the CaO coating effectively protected Si3N4 from oxidation at 1300 ºC for 40h. Moreover, the microstructure analysis showed that CaO coating created more favorable microstructures which reduced oxidation reactions.

Heterogeneous phase deformation in a dual-phase tungsten alloy mediated by the tungsten/matrix interface: insights from compression experiments and crystal plasticity modeling

Tungsten heavy alloy (WHA) is a typical multiphase alloy material consisting of hard tungsten (W) and soft matrix (γ) phases. When loaded, the two phases deform quite differently due to the large difference in their mechanical properties. At present, our understanding of phase deformation and behavior in the multiphase context is relatively poor compared to the single phase case. Such insight is necessary, however, for the design of multiphase alloys having optimal phase microstructure and corresponding material behavior. By combining mechanical testing and crystal plasticity modeling, the relationship between phase microstructure and multiphase alloy deformation behavior is systematically investigated in this work. The results demonstrate that deformation in the W and γ phases is quite different and related to the contrast in material properties between the two phases. Deformation heterogeneity in the multiphase alloy is characterized by the strain gradient near/across the W/γ interface and differences in phase deformation states in relation to the contrast in phase material properties and phase volume fraction. It is found that dislocation pile-up and twinning are the main mechanisms mediating heterogeneous deformation in the region around W/γ interfaces. Based on this insight, a novel design strategy for multiphase alloys is proposed based on optimization of the contrast in phase mechanical properties and the phase volume fractions. This strategy can be employed to design new tungsten alloys and other multi-phase alloys.

Estimation of gas diffusion coefficient for gas/oil-saturated porous media systems by use of early-time pressure-decay data: An experimental/numerical approach

This paper presented a novel numerical method for estimating the gas diffusion coefficient based on the early-time pressure-decay data. Experimentally, “flooding–soaking” procedures were developed to perform the gas diffusion in an oil-saturated tight core under different gas phase volume conditions. After flooding, the capillary bundle model was used to calculate the oil–gas contact area. The early-time pressure-decay data of the gas phase were monitored and recorded during the soaking process. Theoretically, a non-equilibrium inner boundary condition coupled with the characteristics of experimental early-time pressure had been incorporated to develop a diffusion model for a gas/oil-saturated tight core system. Based on gas-phase mass balance equations and gas equation of state, the diffusion coefficients were optimized once the discrepancy between experimental data and numerical solutions was minimized. According to the estimated results in this study, the CH4 diffusion coefficients were 3.74 × 10−11 and 3.86 × 10−11 m2/s in tight core saturated with crude oil, respectively. Moreover, the oil–gas contact area significantly impacts the diffusion flux in oil-saturated porous media. Specifically, an additional 10% contact area results in a 75% increase in CH4 diffusion mass. In addition, with the application of our proposed model to CH4/bitumen and CO2/bitumen systems, the diffusion coefficients were in close agreement with the results reported in previous literature, indicating that the proposed model was applicable to both gas/liquid and gas/liquid-saturated porous media systems.