Multiphase Structure Research Articles

Improved diffuse interface-immersed boundary method for three-dimensional multiphase fluids–structure interaction with moving contact lines

In the realm of numerical algorithms for investigating interactions between multiphase fluids and structure, the accurate computation of moving contact lines (MCLs) dynamics and the substantial computational resource demands bring challenges in three-dimensional simulations. In this study, an improved diffuse interface-immersed boundary method is proposed to efficiently investigate three-dimensional multiphase fluids–structure interactions. The present work commences with the development of the explicit correction scheme and the simplified Dirac function coefficient, designed to efficiently implement the immersed boundary technique. To validate the effectiveness and accuracy of the proposed method, the simulations of water entry and exit for a half-buoyant sphere are carried out, which conclusively demonstrate that the proposed method offers significant advantages in terms of both efficiency and accuracy, faithfully capturing the dynamic response of solid structures and the substantial deformation of free surfaces at the three-dimensional scale. Additionally, a comparative analysis of the results obtained using the proposed method for the free water exit of a hollow sphere against previous experimental data is conducted, highlighting the promising potential of the proposed method for applications.

Fabricating High Strength Bio-Based Dynamic Networks from Epoxidized Soybean Oil and Poly(Butylene Adipate-co-Terephthalate).

Amid the rapid development of modern society, the widespread use of plastic products has led to significant environmental issues, including the accumulation of non-degradable waste and extensive consumption of non-renewable resources. Developing healable, recyclable, bio-based materials from abundant renewable resources using diverse dynamic interactions attracts increasing global attention. However, achieving a good balance between the self-healing capacity and mechanical performance, such as strength and toughness, remains challenging. In our study, we address this challenge by developing a new type of dynamic network from epoxidized soybean oil (ESO) and poly(butylene adipate-co-terephthalate) (PBAT) with good strength and toughness. For the synthetic strategy, a thiol-epoxy click reaction was conducted to functionalize ESO with thiol and hydroxyl groups. Subsequently, a curing reaction with isocyanates generated dynamic thiourethane and urethane bonds with different bonding energies in the dynamic networks to reach a trade-off between dynamic features and mechanical properties; amongst these, the thiourethane bonds with a lower bonding energy provide good dynamic features, while the urethane bonds with a higher bonding energy ensure good mechanical properties. The incorporation of flexible PBAT segments to form the rational multi-phase structure with crystalline domains further enhanced the products. A typical sample, OTSO100-PBAT100, exhibited a tensile strength of 33.2 MPa and an elongation at break of 1238%, demonstrating good healing capacity and desirable mechanical performance. This study provides a promising solution to contemporary environmental and energy challenges by developing materials that combine mechanical and repair properties. It addresses the specific gap of achieving a trade-off between tensile strength and elongation at break in bio-based self-healing materials, promising a wide range of applications.

Novel collagen gradient membranes with multiphasic structures: Preparation, characterization, and biocompatibility

Scaffolds with multiphasic structures are considered to be superior for guided tissue regeneration. Two types of tilapia skin collagen gradient membranes (stepped gradient and linear gradient) with multiphasic structures were prepared by controlling the collagen concentrations and the freezing rates. The results revealed that collagen gradient membranes were more capable of guiding tissue regeneration compared to homogeneous membranes. These two gradient membranes featured a dense outer layer and a loose inner layer, with good mechanical properties as indicated by tensile strengths of more than 250 Kpa and porosities exceeding 85 %. Additionally, these membranes also showed good hydrophilicity and water absorption, with an inner layer contact angle of less than 91° and a water absorption ratio greater than 40 times. Furthermore, the multiphasic scaffolds were proved to be biocompatible by the acute toxicity assay, the intradermal irritation test and so on. Gradient membranes could effectively promote the adhesion and proliferation of fibroblasts and osteoblasts, through elevating the TGF-β/Smad signaling pathway by TGF-β and Smads, and activating the Wnt/β-catenin signaling pathway by LRP5 and β-catenin, similar to homogenous membranes. Therefore, collagen gradient membranes from tilapia skin show important application value in guiding tissue regeneration.

Improving tensile properties of glass fiber-reinforced epoxy resin composites based on enhanced multiphase structure: The modification of resin systems and glass fibers

Glass fiber-reinforced polymer (GFRP) composites have been widely used as reinforced materials in marine engineering due to their good corrosion resistance and economic benefits. However, the mechanical properties of GFRP are lower than that of composites reinforced by carbon and aramid fibers etc. Methods to improve the mechanical properties of GFRP received ongoing attention. GFRP have various mechanical properties due to the characteristics of its multiple phases. This study developed an optimized processing method based on multiphase structures for GFRP composites, significantly enhancing the tensile properties of GFRP laminates. The modified GFRP can be produced efficiently by this method to meet more utilization situations in marine engineering. The influence of curing agents, silane coupling agents (SCA)-treated glass fibers (GFs), and nanomaterials on GFRP's tensile properties was investigated. The findings reveal a 10.64 % increase in the characteristic load of GF bundles due to the improved bonding between fibers by SCA. Besides, the contact angle between SCA-treated GFs and epoxy resin shows a significant reduction (26.69 %). Variations in ply thickness and resin system distinctly influence the tensile properties and failure modes of GFRP laminates. Laminates with 4-ply GF fabrics facilitate more effective load transfer across the matrix-fiber boundary, yielding optimal tensile properties for GFRP. Epoxy/phenolic amine resin system with more reactive functional groups (-OH) enhances the fiber-resin bonding, further improving the tensile properties of GFRP. The enhancement mechanism of the multiphase structure in GFRP was elucidated by microscale characterization, indicating that the multiphase structures in GFRP, enhanced by SCA, nanomaterials, and functional curing agents, significantly improve its tensile properties.

Organisation design in megaprojects: A systematic literature review and research agenda

Megaprojects have a complex and evolving web of organisations arranged in a multilevel and multiphase structure, with intra- and inter-organisational boundaries evolving during the life cycle. This systematic review explores organisation design in megaprojects, identifying the processes for designing temporary megaproject organisational systems. The review analyses 141 full articles from a sample of 10,078 papers and presents three main contributions: the main theoretical lenses used to develop organisation design research in megaprojects, eight decision dimensions influencing organisation design choices, and the most common organisational capabilities. We present the Megaproject Organisation Design (MegaOD) Framework, as a structure to design organisational boundaries, and to identify the organisational dynamics (design, development, and redesign). We suggest four research streams to advance the design of complex organisations: 1. Design of megaproject ecosystems, 2. Degree of organisational interdependence, 3. Design for integration of product and organisational architectures, and 4. The role of organisational designers.

A Study of Interstellar Medium in the Line of Sight of Transient Neutron Star Low-Mass X-ray Binary, MXB 1659-298, by Timing and Spectral Analysis

This work is dedicated to the study of interstellar medium (ISM) along the line of sight (LOS) of the transient low-mass X-ray binary, MXB 1659-298, capitalizing the high resolving power of XMM-Newton in the soft energy range. We emphasized the analysis of reflection grating spectrometer (RGS) data in the energy range 0.5–2.15 keV, suitable for the study of ISM. The paper includes an explanation of why, in the soft X-ray energy range, only two observations (out of seven) were deemed eligible for analysis. Three absorption lines associated with highly ionized Fe XX (1s22p2-2p2 (3p) 4d), Si XIV (1s2-1s2p), and Mg XI (1s2-1s6p) were identified in the observations, with IDs of 8620701(2001) and 748391601(2015). These new absorption lines and the absorption edge due to the neutral oxygen K edge seen in the spectra validate the multiphase structure of ISM. The predominance of interstellar medium over the ionized absorber is established along the direction of the source. The equivalent hydrogen column density measured is nearly equal to the galactic HI value derived previously. The small value of the ionic column density of Fe, Si, and Mg in the site of the high-temperature region resembles previous findings.

Role of Quenching Temperature Selection in the Improvement of the Abrasive (Al2O3) Wear Resistance of Hybrid Multi-Component Cast Irons.

In this paper, enhancing the tribological characteristics of novel cast metallic materials-hybrid multi-component cast irons-by applying a strengthening heat treatment is described. The experimental materials were the cast alloys of a nominal composition (5 wt.% W, 5 wt.% Mo, 5 wt.% V, 10 wt.% Cr, 2.5 wt.% Ti, Fe is a balance) supplemented with 0.3-1.1 wt.% C and 1.5-2.5 wt.% B (total of nine alloys). The heat treatment was oil-quenching followed by 200 °C tempering. The quench temperature (QT) varied in the range of 900-1200 °C, with a step of 50 °C (with a 2-h holding at QT). The correlation of the QT with microstructure and properties was estimated using microstructure/worn surface characterization, differential scanning calorimetry, hardness measurement, and three-body-abrasive wear testing (using Al2O3 particles). The as-cast alloys had a multi-phase structure consisting of primary and/or eutectic borocarbide M2(B,C)5, carboborides M(C,B), M7(C,B)3, M3(C,B), and the matrix (ferrite, martensite, pearlite/bainite) in different combinations and volume fractions. Generally, the increase in the quenching temperature resulted in a gradual increase in hardness (maximally to 66-67 HRC) and a decrease in the wear rate in most alloys. This was due to the change in the phase-structure state of the alloys under quenching, namely, the secondary carboboride precipitation, and replacing ferrite and pearlite/bainite with martensite. The wear rate was found to be inversely proportional to bulk hardness. The maximum wear resistance was attributed to QT = 1150-1200 °C, when the wear rate of the alloys was lowered by three to six times as compared to the as-cast state. With the QT increase, the difference in the wear rate of the alloys decreased by three times. The highest abrasive resistance was attributed to the alloys with 1.1 wt.% C, which had a 2.36-3.20 times lower wear rate as compared with that of the reference alloy (13 wt.% Cr cast iron, hardness of 66 HRC). The effects of carbon and boron on hardness and wear behavior are analyzed using the regression models developed according to the factorial design procedure. The wear mechanisms are discussed based on worn surface characterization.

AGN-driven outflows in clumpy media: multiphase structure and scaling relations

AGN-driven outflows in clumpy media: multiphase structure and scaling relations

The Design and Fabrication of Engineered Tubular Tissue Constructs Enabled by Electrohydrodynamic Fabrication Techniques: A Review

AbstractElectrohydrodynamic processes have emerged as promising methods for fabricating polymetric fiber‐based artificial tubular tissues. Existing review articles focus on the biological applications and processing materials associated with electrohydrodynamic processes in artificial tubular constructs, while overlooking the design and fabrication of these constructs. To address this gap, this review article emphasizes the design and fabrication of tubular tissue constructs enabled by employing electrohydrodynamic processes. This article begins by presenting an overview of two electrohydrodynamic processes: solution electrospinning (SE) and melt electrowriting (MEW). It then delves into the control of the fiber diameter enabled by SE and MEW, offering insights into the manipulation of processing parameters to achieve desired fiber diameters. Additionally, the review highlights cutting‐edge strategies for electrohydrodynamic processes to create tubular structures with customized microarchitectures. This includes fiber alignment control for SE and pore morphology design for MEW. Moreover, the review covers the creation of customized macroscale tubular geometries through collector geometry design. Lastly, a comprehensive survey is presented for designing multiphasic tubular structures specifically for electrohydrodynamic techniques or in tandem with other techniques. The objective of this review is to offer a thorough understanding of the design considerations and potential applications of tubular structures fabricated by electrohydrodynamic processes.

Biomolecular condensates can enhance pathological RNA clustering.

Intracellular aggregation of repeat expanded RNA has been implicated in many neurological disorders. Here, we study the role of biomolecular condensates on irreversible RNA clustering. We find that physiologically relevant and disease-associated repeat RNAs spontaneously undergo an age-dependent percolation transition inside multi-component protein-nucleic acid condensates to form nanoscale clusters. Homotypic RNA clusters drive the emergence of multiphasic condensate structures with an RNA-rich solid core surrounded by an RNA-depleted fluid shell. The timescale of the RNA clustering, which drives a liquid-to-solid transition of biomolecular condensates, is determined by the sequence features, stability of RNA secondary structure, and repeat length. Importantly, G3BP1, the core scaffold of stress granules, introduces heterotypic buffering to homotypic RNA-RNA interactions and impedes intra-condensate RNA clustering in an ATP-independent manner. Our work suggests that biomolecular condensates can act as sites for RNA aggregation. It also highlights the functional role of RNA-binding proteins in suppressing aberrant RNA phase transitions.

Indentation response of multi-phase nanocrystalline NbWTi refractory multi-principal element alloy

NbWTi refractory multi-principal element alloy has been synthesized using powder metallurgy route. 40 h of mechanical alloying resulted in a single-phase alloy and subsequent spark plasma sintering transformed it into a multi-phase structure (1 BCC and 2 FCC phases). The alloy demonstrated an extremely high hardness of 12.29 ± 0.05 GPa at a load of 1000 g, along with excellent “density-normalized” hardness and indentation size effect. An indentation fracture toughness of 6.81 ± 0.16 MPa.m1/2 was measured using the cracks generated. Ultra-high absolute hardness, high “density-normalized” hardness and associated fracture toughness signifies the potential of this alloy for next generation structural engineering applications.

Achieving Homogeneous Microstructure and Superior Properties in High-N Austenitic Stainless Steel via a Novel Atmosphere-Switching Method

Powder metallurgy is widely used to fabricate high-nitrogen, nickel-free austenitic stainless steel. However, after sintering and nitriding, additional solution treatment is typically required to achieve uniform nitrogen distribution and a homogeneous austenite phase. This work proposes a novel method to eliminate the need for lengthy and high-temperature solution treatment by switching the nitrogen atmosphere to argon during the cooling process. The effects of different N2-Ar atmosphere-switching temperatures (750–1320 °C) on the phase composition, element distribution, microstructure, mechanical properties, and corrosion resistance of the studied steels were systematically investigated. Results show that cooling in the N2 atmosphere initially transforms the matrix to a fully austenitic structure enriched with nitrogen. Excessive nitrogen infiltration leads to Cr2N precipitation, inducing partial austenite decomposition and forming a multiphase structure comprising austenite, α-Fe, and Cr2N. Strategic switching from N2 to Ar reverses this reaction, yielding a high-nitrogen, chemically uniform austenitic structure. Specifically, switching at 1150 °C, the steel exhibits excellent mechanical properties and corrosion resistance, with a yield strength of 749 MPa, an ultimate tensile strength of 1030 MPa, an elongation of 38.7%, and a corrosion current of 0.06 mA/cm2, outperforming the steels cooled solely in N2 and subsequently solution-treated. This novel method offers advantages in cost reduction, energy saving, and operational effectiveness, highlighting its potential for broad industrial application.

An excellent combination of strength and ductility via hierarchical precipitation structures in Co-free medium-entropy alloys

A Co-free non-equiatomic Ni2·5CrFeAl0·25Ti0.25 medium-entropy alloy (MEA) with an excellent strength-ductility synergy was fabricated, which shows a multiphase structure composed of face-centered cubic (FCC), L12 (ordered FCC), and Cr-rich body-centered cubic (BCC) phase by thermomechanical processing. Specifically, the aged sample displays the outstanding yield tensile strength (YTS, ∼1188 MPa), ultimate tensile strength (UTS, ∼1560 MPa) and work-hardening rate (WHR, ∼4.5 GPa) values as well as an acceptable plasticity of ∼16.6%. Theoretical calculations suggest that precipitation strengthening significantly contributes to achieving the fascinating tensile strength among various strengthening contributors. Further analyses reveal that multiple nanoscale stacking-fault (SF) networks are activated during plastic deformation in the aged alloy. Accordingly, the dual effects consisting of the hierarchical precipitation structure and SF networks lead to the combination of excellent tensile strength and strain-hardening capacity.

Microstructural transformation and corrosion–cavitation behavior of ultrasonic nanocrystal surface modified nickel aluminum bronze (NAB)

In this study, nickel–aluminum bronze (NAB) is optimized by ultrasonic nanocrystal surface modification (UNSM), and its surface microstructural evolution, surface hardness, electrochemical corrosion behavior, and cavitation erosion behavior are investigated. The potentiodynamic polarization curves and electrochemical impedance spectra before and after UNSM treatment of NAB are measured using a typical three-electrode system. The cavitation erosion process is simulated through the vibration of ultrasonic waves underwater, and the cavitation erosion resistance performance of various specimens is evaluated. UNSM significantly refines the coarse and heterogeneous multi-phase structure of the cast NAB, providing a relatively uniform and dispersed structure. Simultaneously, severe plastic deformation rapidly increases micro-strains on the NAB surface, which effectively improves its surface hardness from 211 to 360 Hv. After UNSM treatment, the corrosion potential increases slightly; and the passivation potential and current decrease considerably, dropping from 207 to 103 mV and from 5.23 to 2.41 mA/cm2, respectively. This is primarily because of the slowdown of selective-phase corrosion and the uniform formation of an oxide film. Additionally, UNSM parameters affect corrosion potential by regulating surface roughness. A smoother surface corresponds to a higher corrosion potential at the same load. UNSM treatment significantly improves the cavitation corrosion resistance of NAB, primarily because an increase in hardness and uniform distribution of structure effectively slows the speed of crack formation and propagation, which is a result of the synergistic improvement of mechanical and corrosion resistance properties.

Geotectonic architecture beneath Northern Vietnam revealed by local earthquake tomography combining seismic data from multiple networks

Extrusion tectonics driven by the collision of Indian-Eurasian continents and the relative motion among microcontinents (e.g. South China, Simao-Indochina blocks) has led to multi-phase and complex geological activity and structures in Northern Vietnam. While extensively studied, its detailed crustal architecture in association with multiple large-scale shear zones and plate boundaries remains unclear and is key to resolving long-lasting tectonic debates. This study constructs the first 3-D regional S-wave velocity (Vs) model with consistent P-wave velocity (Vp) and Vp/Vs ratio models by jointly using the crustal and head waves (e.g. Pg/Sg and Pn/Sn phases) from an augmented earthquake catalog combining the Vietnam National Earthquake Catalog (VNCAT) and the data from multiple adjacent seismic networks. The quality of phase picking and earthquake location incorporating seismic data from various sources are carefully examined and collected for the tomographic inversion. We use a stepwise joint inversion scheme to subsequently constrain the earthquake location, 1-D and 3-D velocity models. The output models suggest that the Song Ma suture represents a better candidate for the Indochina-South China boundary rather than the Red River Shear Zone. The latter seems to act as a crustal structure while the former and the Dien Bien Phu Fault are likely lithospheric ones. Several other geologic features such as the Tu Le volcanic basin, the Song Hong basin, and the Day Nui Con Voi metamorphic complex are also clearly depicted and discussed in the model. This new set of the Vp, Vs, and Vp/Vs models could further contribute to better assessment to seismic hazards in the northern Vietnam.

Achieved strength-plastic trade-off in HfMoNbTaTi refractory high-entropy alloy via powder metallurgy process

The practical application of refractory high-entropy alloys (RHEAs) has been limited by their brittleness at room temperature. This study prepared fine-grained HfMoNbTaTi refractory high-entropy alloys using a powder metallurgy process combining mechanical alloying (MA) and spark plasma sintering (SPS). This method effectively addresses the issue of room temperature brittleness and achieves a favorable balance between strength and plasticity. The resulting sintered alloy comprises two body-centered cubic (BCC) solid solution matrices and a range of nanoprecipitates, including the γ-phase, σ-phase, and α-phase. With increasing sintering temperature, the average grain size increased from 0.45 μm (at 1400 °C) to 4.56 μm (at 1700 °C). Simultaneously, the content of the γ-phase gradually decreases due to the greater influence of mixing entropy. Under quasi-static loading, the fine-grained multiphase structure not only benefits from grain boundary strengthening and precipitation strengthening effects, but also enhances the deformation uniformity, ultimately improving both the strength and plasticity. At 1450 °C, the sintered alloy exhibited a compressive yield strength of 2325 ± 8.40 MPa and a plastic strain of 26.44 ± 1.17 %. These values represent a 35.73 % increase in yield strength and a 120.33 % increase in plastic strain compared to those of the as-cast alloy. The deformation process at room temperature is mainly governed by the multiplication of screw dislocations and cross-slips. In the middle and late stages of deformation, the grains exhibit a preferred orientation, further enhancing the plastic strain. In summary, this study presents a practical approach for overcoming the issue of room temperature embrittlement in RHEAs.

Architecting O3/P2 layered oxides by gradient Mn doping for sodium-ion batteries

O3 phase layered oxides are highly attractive cathode materials for sodium-ion batteries because of their high capacity and decent initial Coulombic efficiency. However, their rate capability and long cycling life are unsatisfactory due to the narrow Na+ transfer channel and irreversible phase transitions of O3 phase during sodiation/desodiation process. Constructing O3/P2 multiphase structures has been proven to be an effective strategy to overcome these challenges. In this study, we synthesized bi-phasic structured O3/P2 Na(Ni2/9Fe1/3Cu1/9Mn1/3)1-xMnxO2 (x = 0.01, 0.02, 0.03, 0.04, 0.05) materials through Mn doping during sodiation process. Benefiting from surface P2 phase layer with the enhanced Na+ transfer dynamics and high structural stability, the Na(Ni2/9Fe1/3Cu1/9Mn1/3)0.98Mn0.02O2 (NFCM-M2) cathode delivers a reversible capacity of 139.1 mA h g−1 at 0.1 C, and retains 71.4 % of its original capacity after 300 cycles at 1 C. Our work provides useful guidance for designing multiphase cathodes and offers new insights into the structure-performance correlation for sodium-ion cathode materials.

Biomolecular Condensates Can Enhance Pathological RNA Clustering.

Intracellular aggregation of repeat expanded RNA has been implicated in many neurological disorders. Here, we study the role of biomolecular condensates on irreversible RNA clustering. We find that physiologically relevant and disease-associated repeat RNAs spontaneously undergo an age-dependent percolation transition inside multi-component protein-nucleic acid condensates to form nanoscale clusters. Homotypic RNA clusters drive the emergence of multiphasic condensate structures with an RNA-rich solid core surrounded by an RNA-depleted fluid shell. The timescale of the RNA clustering, which drives a liquid-to-solid transition of biomolecular condensates, is determined by the sequence features, stability of RNA secondary structure, and repeat length. Importantly, G3BP1, the core scaffold of stress granules, introduces heterotypic buffering to homotypic RNA-RNA interactions and impedes intra-condensate RNA clustering in an ATP-independent manner. Our work suggests that biomolecular condensates can act as sites for RNA aggregation. It also highlights the functional role of RNA-binding proteins in suppressing aberrant RNA phase transitions.

Synergistic catalytic effect of LPSO structure and nano (Ni-TiO2)@C on hydrogen storage properties of Mg-Ni-Y alloy

Fine multiphase structure and LPSO structure are formed in the hydrogen storage alloy Mg88.7Ni6.3Y5 by microalloying with small amounts of Ni and Y elements. The catalyst (Ni-TiO2)@C is torn as a carbon layer encapsulating on the surface of the alloy particles by ball milling to form Mg88.7Ni6.3Y5+1 wt.% (Ni-TiO2)@C hydrogen storage composites. The Ni and TiO2 in the catalyst accelerate the dissociation of hydrogen molecules. The carbon carrier prevents the agglomeration of nanocatalysts Ni and TiO2. The alloy exhibited exceptional hydrogen ab/desorption kinetics. It can reach 80% hydrogen absorption saturation content within 1 min. The initial hydrogen desorption temperature has been reduced to 200 °C, and the dehydrogenation content is 4.26 wt.% at 250 °C. The adsorption energies of hydrogen atoms at different sites are calculated by Density Functional Theory (DFT). Synergistic catalytic effects were observed in LPSO and (Ni-TiO2)@C.

Multiphase riveting structure constructed by slight molybdenum for enhanced P3/O3 layer-structured oxide cathode material

Phase engineering has been efficiently employed to improve the performance of transition metal oxide cathode materials by alleviating the Jahn-Teller effects and optimizing the ions diffusion pathway. The second-order Jahn-Teller effects by slight molybdenum substitution was confirmed to activate a new phase formation and to construct a multiphase riveting structure. A P3/O3 riveting-structured NaNi0.3Mn0.52Mo0.03Cu0.1Ti0.05O2 cathode material was successfully synthesized for sodium ion batteries, which undergoes a reversible phase transition from P3/O3 → P3 → Hex.O3′ when charged to 4.25 V and most of the materials will transform into P3 phase after the first charge–discharge cycle. Due to the high reversibility and crystal structure stability, it indicates 155.0 mAh g−1 discharge capacity with a high up to 99.65 % initial Coulomb efficiency. This P3/O3 riveting structure can alleviate the rigid failure caused by phase transition. Meanwhile, O3/P3 phases provide the main storage sites for Na+ as skeletons and the existence of P3 phase provides a better diffusion pathway for ion transport.