Multiphase Interface Research Articles

Nanophase-separated ternary PdAgCu nanotubes with rich interfaces for enhanced formic acid oxidation reaction

Herein, a facile strategy for the preparation of PdAgCu ternary nanotubes (NTs) is introduced by using Cu nanowires (NWs) as sacrificial templates along with an acid-leaching treatment. Since the phase separation between Ag and Cu, the obtained PdAgCu NTs is made up of various nanosphases including pure Ag, Cu, bimetallic PdCu and PdAg nanoalloys, instead of PdAgCu trimetallic nanoalloys. By adjusting the types of solvents during synthesis, the surface morphology of PdAgCu NTs can be tuned from smooth (S-PdAgCu NTs) to rough (R-PdAgCu NTs). Both S-PdAgCu NTs and R-PdAgCu NTs exhibit excellent electrocatalytic performances for formic acid oxidation reaction (FAOR). Remarkably, the mass activity of S-PdAgCu NTs for FAOR can reach up to 4307 mA mgPd-1 at peak potential, which is 8.5 times higher than that of commercial Pd (506 mA mgPd-1). The impressively enhanced activity should be ascribed to the synergistic effect of Pd with Cu or Ag and the multi-phase interface engineering, which is resulting from the tight position relationships among different monometallic or bimetallic alloy nanophases.

An improved smoothed particle hydrodynamics method for modeling multiphase flows

Multiphase flows are prevalent in both natural and engineered systems. The study of multiphase flow problems using numerical simulation is challenging due to the presence of high nonlinearities and moving interfaces. In this paper, an improved multiphase smoothed particle hydrodynamics (SPH) model is proposed for simulating multiphase flows. In the improved multiphase SPH model, an improved interface repulsive force model is proposed to reduce the interpenetration of particles at the multiphase interface and make the multiphase interface smooth and clear, and an improved kernel gradient correction is introduced to optimize the computational results. In addition, the particle shifting technology is applied to make the particle distribution uniform. Five numerical examples including the Rayleigh–Taylor instability, non-Boussinesq lock-exchange problem, square droplet deformation, single bubble rise, and circular droplet oscillation are investigated to verify the correctness and effectiveness of the improved multiphase SPH model. The results demonstrate that the improved multiphase SPH approach is effective in modeling multiphase flows.

Factors influencing residual air saturation during consecutive imbibition processes in an air-water two-phase fine sandy medium – A laboratory-scale experimental study

The residual air saturation plays a crucial role in modeling hydrological processes of groundwater and the migration and distribution of contaminants in subsurface environments. However, the influence of factors such as media properties, displacement history, and hydrodynamic conditions on the residual air saturation is not consistent across different displacement scenarios. We conducted consecutive drainage-imbibition cycles in sand-packed columns under hydraulic conditions resembling natural subsurface environments, to investigate the impact of wetting flow rate, initial fluid state, and number of imbibition rounds (NIR) on residual air saturation. The results indicate that residual air saturation changes throughout the imbibition process, with variations separated into three distinct stages, namely, unstable residual air saturation (Sgr-u), momentary residual air saturation (Sgr-m), and stable residual air saturation (Sgr). The results also suggest that the transition from Sgr-u to Sgr is driven by changes in hydraulic pressure and gradient; the calculated values followed the following trend: Sgr > Sgr-u > Sgr-m. An increase in capillary number, which ranged from 1.46 × 10−7 to 3.07 × 10−6, increased Sgr-u and Sgr-m in some columns. The increase in Sgr ranged from 0.034 to 0.117 across all the experimental columns; this consistent increase can be explained by water film expansion at the primary wetting front along with a strengthening of the hydraulic gradient during water injection. Both the pre-covered water film on the sand grain surface and a pore-to-throat aspect ratio of up to 4.42 were identified as important factors for the increased residual air saturation observed during the imbibition process. Initial air saturation (Sai) positively influenced all three types of residual air saturation, while initial capillary pressure (Pci) exhibited a more pronounced inhibitory effect on residual air saturation, as it can partly characterized the initial connectivity of the air phase generated under different drying flow rates. Under identical wetting flow rate conditions, Sgr was higher during the second imbibition than during the first imbibition due to variations in initial fluid state, involving both fluid distribution and the concentration of dissolved air in the pore water. In contrast, NIR did not have an obvious effect on the three types of residual air saturation. This work aims to provide empirical evidences and offer further insights into the capture of non-wetting phases in groundwater environments, as well as to put forward some potential suggestion for future investigations on the retention and migration of contaminants that involves multiphase interface interactions in subsurface environments.

Breakdown and interface dynamics of pulsed discharge plasma across air-water interface: From single to repetitive stimulation

Pulsed discharge in the vicinity of a multi-phase interface, where a discontinuity of physical properties exists, can be a joint problem of both electro- and thermo-physics. This study shows a comprehensive analysis of electric breakdown across an air-water interface and its successive multi-physical effects. The scenario is constructed via a pair of pin electrodes positioned on both sides of the interface, and the transient discharge is analyzed using high-speed backlight photography synchronized with electrical and optical diagnostics. It is observed that the corona/streamer develops from either side of the pin electrode. Electrostatic instability causes the interface to fluctuate and a water column to form above the interface. By increasing the applied voltage, discharge evolves from “dielectric barrier” mode (pin to interface) to “through breakdown” mode (pin to pin). Once the conductive channel bridges two electrodes, electric power of ∼40 kW peak and deposited energy of 100 mJ will be injected into the channel and promote the “streamer-spark” transition, resulting in a crown-like splash (100 m s-1) near the interface and cavity formation. As the quenching of diffused plasmas, the over-expanded splash (5 mm in diameter) would be re-compressed by the ambient air. Particularly, the shrinkage of the thin water film of the splash can reach a 20 mm jet near the axis and develop Rayleigh-Taylor instability, along with the formation of micro-jets eruption during the convergent collision. More sophisticated interactions will appear at higher repetitive frequency (>100 Hz), where the perturbation caused by one pulse will influence the next, namely the “memory” effect. Furthermore, periodic loading on the interface effectively changes the cavity characteristics, showing an attractive prospect in fluid control applications.

Constructing interfacial polarization to improve electrocatalytic nitrogen reduction reactions in polyoxometalates-based metal-organic framework-derived Fe7S8-WS2-Co9S8 multi-phase heterostructures

Electrocatalytic nitrogen (N2) reduction to produce ammonia (NH3) has received increasing attention. It is urgent to design highly active and environmentally friendly catalysts due to present electrocatalysts still suffering from poor stability and low catalytic efficacy. In this work, Fe7S8-WS2-Co9S8 multi-phase heterostructures are prepared by using a template-directed assembly approach. The uniform distribution of Fe7S8-WS2-Co9S8 nanosheets derived from polyoxometalate-based metal-organic frameworks (POMOFs) largely provides more reactive active sites and improves the enrichment efficiency of N2. Multi-phase heterojunction interface between Fe7S8, WS2 and Co9S8 enhances the interfacial polarisation and leads to electron transfer from WS2 to Fe7S8 and Co9S8, and further facilitated the reduction of N2 in the electron-rich Fe7S8, resulting in an ultrahigh NH3 yield of 51.21 μg·h·mgcat.−1 and a Faradaic efficiency of 34.12 %. Density Functional Theory (DFT) calculations indicate that Fe sites are favorable sites for N2 adsorption in Fe7S8-WS2-Co9S8 composites, and Fe7S8-WS2-Co9S8 is most likely to catalyze nitrogen reduction via the distal pathway. The current investigation provides a perspective for developing multi-phase heterogeneous catalysts for electrocatalytic NH3 from N2.

Yttrium induced formation of new pores in an as-cast nickel-based single crystal superalloy

Pores are the most fatal defects in single crystal superalloys, which severely deteriorates the mechanical properties. Yttrium (Y) has been applied in commercial superalloys, but its effect on the morphology change of casting pores is not clear. This work focuses on the effect of Y on the evolution of pores formed after directional solidification in a second-generation superalloy. SEM, TEM and XRT were used to characterize the pores, and Thermo-Calc was used to calculate the surface tension change during the solidification process. Results show that, besides the formation of two types of conventional shrinkage pores during solidification, new types of pores, i.e., Type III and Type IV, due to the addition of Y element to 0.5 wt% in superalloy, were also observed. The formation of Type III pore could be ascribed to the surface tension drop in the liquid phase, which enhances the wettability at the solid/liquid interface, and promotes the mobility of liquid phase, due to the incorporation of Y element. The formation of Type IV pore is due to the simultaneous formation and growth of M23C6 and Ni3Al in the Ni5Y phase, triggering the formation of closed zone with a small but irregular shape at the multi-phase interface.

Rational Design of Transition-Metal-Based Catalysts for the Electrochemical 5-Hydroxymethylfurfural Reduction Reaction.

The electrochemical reduction reaction (HMFRR) of 5-hydroxymethylfurfural (HMF) has emerged as a promising avenue for the utilization and refinement of the biomass-derived platform molecule HMF into high-value chemicals, addressing energy sustainability challenges. Transition metal electrocatalysts (TMCs) have recently garnered attention as promising candidates for catalyzing HMFRR, capitalizing on the presence of vacant d orbitals and unpaired d electrons. TMCs play a pivotal role in facilitating the generation of intermediates through interactions with HMF, thereby lowering the activation energy of intricate reactions and significantly augmenting the catalytic reaction rate. In the absence of comprehensive and guiding reviews in this domain, this paper aims to comprehensively summarize the key advancements in the design of transition metal catalysts for HMFRR. It elucidates the mechanisms and pH dependency of various products generated during the electrochemical reduction of HMF, with a specific emphasis on the bond-cleavage angle. Additionally, it offers a detailed introduction to typical in-situ characterization techniques. Finally, the review explores engineering strategies and principles to enhance HMFRR activity using TMCs, particularly focusing on multiphase interface control, crystal face control, and defect engineering control. This review introduces novel concepts to guide the design of HMFRR electrocatalysts, especially TMCs, thus promoting advancements in biomass conversion.

Binder-Free Intertwined Si and MnO2 Composite Electrode for High-Performance Li-Ion Battery Anode.

Silicon is considered as the most felicitous anode material candidate for lithium-ion batteries on account of abundant availability, suitable operating potential, and high specific capacity. Nevertheless, drastic volume expansion during the cycle impedes its practical utilization. Herein, Si and MnO2 (Si-MO) constructed the binder-free intertwined electrode that is reported to effectively improve upon the cycling stability of Si-based materials. The Si-based electrode without a binder has good electrical conductivity, strong adhesion to the substrate, and ample space for mitigating volume expansion. The incorporation of MnO2 establishes a multiphase interface, which mitigates the electrode volume expansion, and supports the electrode structure. Furthermore, MnO2 (∼1230 mAh g-1 theoretical capacity) synergistically enhances the overall capacity of the composite electrodes. Consequently, the Si-MO composite electrode exhibits a reversible specific capacity of 1300 mAh g-1 at 420 mA g-1 and remarkable cycling performance with a specific capacity of 830 mAh g-1 after 500 cycles. In particular, a reversible specific capacity of 837 mAh g-1 at 4200 mA g-1 is achieved and remains stable during 200 cycles. This work provides a potentially feasible way to achieve the Si-based anode commercialization for LIBs.

A high-order simulation method for compressible multiphase flows with condensed-phase explosive detonation in underwater explosions

This study introduces an efficient method designed for the simulation of compressible multiphase flows associated with explosive detonation, primarily in the context of underwater explosions. The proposed approach integrates three core components: the compressible Euler equations, the level-set equation, and the program burn model. Spatial terms of the compressible Euler equations undergo discretization using a fifth-order accuracy weighted essentially non-oscillation reconstruction, while the third-order total variation diminishing Runge–Kutta scheme manages the temporal terms. The level-set method ensures accurate tracking of the multiphase interface. To detail the transition from solid, non-reactive explosives to gaseous detonation products in the condensed charge's detonation reaction zone, the program burn model based on Zeldovich, von Neumann, Doering theory. The efficacy and accuracy of the incorporated program burn model and the multiphase interface capture method are employed through four benchmark tests, exhibiting excellent agreement with previously published data from alternative numerical methods or commercial software. In conclusion, applying the proposed method to four distinct engineering scenarios facilitates a comprehensive understanding of the inherent dynamics associated with detonation and shock wave generation and propagation.

Decoupled electron-phonon transport in Ag2Se thermoelectric materials through constructing TiO2/MoS2 co-decorated cell-membrane-mimic grain boundaries.

Ag2Se has emerged as a promising n-type thermoelectric material; however, its application is limited mainly due to the strongly coupled charge carrier and phonon transport. Enhancing phonon scattering by constructing interfacial complexes often results in low carrier mobility due to its strong carrier scattering resulting from the high energy barrier at the multiphase interface. Inspired by the cell membrane with selective permeability, we construct bio-mimic grain boundaries with TiO2 and MoS2 co-decoration in Ag2Se to decouple electron scattering from strong phonon scattering. The nanostructured TiO2 with a high dielectric constant screens the interfacial Coulomb potential, ensuring efficient carrier transport and reducing the grain boundary barriers, while the few-layer MoS2 provides significant phonon scattering to further reduce the thermal conductivity. This method effectively enhances the zT value of Ag2Se by as much as 60% and also can significantly enhance the theoretical output performance of the thermoelectric device, which highlights the effectiveness of the bio-mimic grain boundary engineering strategy.

The stress response mechanisms and resistance change of chlorine-resistant microbial community at multi-phase interface under residual antibiotics in drinking water distribution system

The presence of multiple trace amounts of antibiotics in drinking water has recently drawn much attention. However, synergistic effects between disinfectants and antibiotics often occur in pipeline due to the presence of residual disinfectants. How this interaction affects the drinking water microbial community remains unknown. Herein, reactors with 2 h of hydraulic retention time (HRT) were constructed to simulate the drinking water distribution system (DWDS), and the antibiotics were continuously discharged to the reactor. Sulfamethoxazole (SMX) was used as a representative antibiotic, and treatment protocols with and without disinfectants were compared. High-throughput sequencing and metagenome were used to study the microbial community and function in polyethylene (PE) and ductile cast iron (DI) (protected by cement mortar lining) pipes. By measuring the enzyme activity and ATP content, we found that disinfectant exposure could not only increase the secretion of biofilm EPS, but also improve the bacterial activity to a certain extent. The synergistic effect of antibiotics and disinfectants could increase the activity of oxidative stress-related enzymes in microbial communities, and the main effect was antibiotic stress. This study not only provides insights into how to inhibit the transmission process of antibiotic resistance genes (ARGs) in biofilm in DWDS, but also provides enlightenment for the harm of ARGs in all carriers where biofilms may exist in water plants.

Multiphase interface coupling of Ni-based sulfide composites for high-current-density oxygen evolution electrocatalysis in alkaline freshwater/simulated seawater/seawater.

Constructing highly efficient electrocatalysts is vital to enhance oxygen evolution reaction (OER) performance at industrially relevant current densities. Herein, three-phase coupled Ni3S2/r-NiS/h-NiS composites are grown in situ on Ni foam (NNSN/NF) via a one-step solvothermal approach. The as-prepared composites need overpotentials of only 377 mV, 451 mV and 476 mV at 1000 mA cm-2 for the OER in alkaline freshwater, simulated seawater and seawater, respectively. In addition, the optimized catalyst exhibited long-term durability at 300 mA cm-2. Our work clarifies designing and preparing cost-effective Ni-based sulfide electrocatalysts for the OER in alkaline freshwater/simulated seawater/seawater under industrially relevant current densities.

Study on self-healing mechanism of magnetic nano-powders functionalized fiber reinforced thermoplastic composites

At present, a variety of methods have been developed to realize the self-healing function of fiber-reinforced composites. However, the intrinsic mechanism of material damage recognition and self-healing initiation still lacks systematic research. In this paper, GF/(FeNip/PP) composites with multistage structures were prepared to study the self-healing properties and the mechanism of fiber-reinforced thermoplastic composites. The addition of a small amount of FeNip without affecting the melting peak temperature of the PP matrix (i.e., without reducing the use temperature of PP) can increase the electromagnetic loss (tanδ) of the composites by about 40% and the thermal conductivity by 36%. The cyclic stretching times of GF/(FeNip/PP) composites after microwave healing are doubled at 50% to 60%σmax load. It is indicated that FeNip endows the GF/PP composites with good microwave healing performance, and the purposeful repair can effectively extend the service life of the material. In addition, the self-healing mechanism of GF/(FeNip/PP) composites is discussed in detail from the aspects of microstructure change, multiphase interface effect, entropy enthalpy effect, starting and ending of self-healing procedures, etc. The magnetothermal effect, “entropy consumption” effect, and polymer chain diffusion are the fundamental reasons for the self-healing function of fiber reinforced thermoplastic composites.

Two birds with one stone: Functionalized wood composites for efficient photocatalytic hydrogen production and solar water evaporation

Maximizing solar energy utilization is a persistent challenge in photo catalysis, which determines sustainable solar-driven photocatalytic process. Photo thermal-coupled photo catalysis is considered as a promising solution to tackle the issues of sustainable energy scarcity and environmental pollution by harvesting the full-spectrum solar energy. Herein, a highly efficient photo thermal-accelerated photo catalysis system is elaborately established, in which the assembled carbonized stick/Nb2C MXene evaporator can heat water into vapor and the integrated g-C3N4 photocatalyst further enables high-efficiency photocatalytic hydrogen production. The designed hyperboloid wood-based architecture possesses a multiphase interface of water steam/catalyst/hydrogen to reduce the transport resistance of hydrogen gas in liquid and ultimately maximize the output of hydrogen energy. Consequently, this coupled photothermal-photocatalytic system achieves a stable solar evaporation rate of 2.16 kg m-1 h-1 under one sun irradiation and highly efficient hydrogen-evolving rate of 3096 µmol g-1 h-1. This work paves a way to explore the improvement of photocatalytic hydrogen production by synergic photothermal effect for potential applications in renewable solar energy utilization and hydrogen production.

Local volume-conservation-improved diffuse interface model for simulation of Rayleigh–Plateau fluid instability

The Rayleigh–Plateau instability is a typical multi-phase fluid interface problem which is driven by the surface tension. After the break-up of a liquid thread, the satellites droplets will appear. To prevent the disappearance of small droplets due to interfacial length minimization, we present a new Cahn–Hilliard-type diffuse interface model to improve the conservation of local volume. By coupling with the incompressible Navier–Stokes equations, the fluid flow-coupled binary system and its axisymmetric form are derived. The pressure projection method and the semi-implicit time-marching method are used to discretize the fluid equations and the diffuse interface equations in time. In the axisymmetric domain, the finite difference method is used to perform the spatial discretization. The fully discrete solution algorithm is introduced in detail. The numerical experiments show that the proposed model has better local volume conservation than the classical Cahn–Hilliard model. The qualitative comparison with a real experiment indicates that the proposed model has a good potential to simulate the coating problem of a cylindrical fibre with a liquid film.

Constructing Multiphase-Induced Interfacial Polarization to Surpass Defect-Induced Polarization in Multielement Sulfide Absorbers.

The extremely weak heterointerface construction of high-entropy materials (HEM) hinders them being the electromagnetic wave (EMW) absorbers with ideal properties. To address this issue, this study proposes multiphase interfacial engineering and results in a multiphase-induced interfacial polarization loss in multielement sulfides. Through the selection of atoms with diverse reaction activities, the multiphase interfacial components of CuS (1 0 5), Fe0.5 Ni0.5 S2 (2 1 0), and CuFe2 S3 (2 0 0) are constructed to enhance the interfacial polarization loss in multielement Cu-based sulfides. Compared with single-phase high-entropy Zn-based sulfides (ZnFeCoNiCr-S), the multiphase Cu-based sulfides (CuFeCoNiCr-S) possess optimized EMW absorption properties (effective absorption bandwidth (EAB) of 6.70GHz at 2.00mm) due to the existence of specific interface of CuS (1 0 5)/CuFe2 S3 (2 0 0) with proper EM parameters. Furthermore, single-phase ZnFeCoNiCr-S into FeNi2 S4 (3 1 1)/(Zn, Fe)S (1 1 1) heterointerface through 400°C heat-treated is decomposed. The EMW absorption properties are enhanced by strong interfacial polarization (EAB of 4.83GHz at 1.45mm). This work reveals the reasons for the limited EMW absorption properties of high-entropy sulfides and proposes multiphase interface engineering to improve charge accumulation and polarization between specific interfaces, leading to the enhanced EMW absorption properties.

A one-pot method to prepare a multi-metal sulfide/carbon composite with a high lithium-ion storage capability

Because of their high electrochemical activity, good structural stability, and abundant active sites, multi-metal sulfide/carbon (MMS/C) composites are of tremendous interest in diverse fields, including catalysis, energy, sensing, and environmental science. However, their cumbersome, inefficient, and environmentally unfriendly synthesis is hindering their practical application. We report a straightforward and universal method for their production which is based on homogeneous multi-phase interface engineering. The method has enabled the production of 14 different MMS/C composites, as examples, with well-organized composite structures, different components, and dense heterointerfaces. Because of their composition and structure, a typical composite has efficient, fast, and persistent lithium-ion storage. A ZnS-Co9S8/C composite anode showed a remarkable rate performance and an excellent capacity of 651 mAh·g−1 at 0.1 A·g−1 after 600 cycles. This work is expected to pave the way for the easy fabrication of MMS/C composites.

Multiphase interface engineering based on porous manganous oxide toward broad-band microwave absorption

Herein, the porous manganous oxide-based ternary nanocomposites were successfully obtained by combining the in-suit deposition of ZIF-67 and the following thermolysis technology. The synergistic contributions of dipole polarizations, multi-interface induced space charge polarizations, and conductive loss induced by Co particles give the nanocomposites exceptional microwave absorption (MA). Consequently, MnO/Co/C ternary composites presented a strong reflection loss (RL), reaching -51.83 dB at 2.17 mm. Furthermore, the effective absorption bandwidth (EAB) reached 5.6 GHz at 1.9 mm. When adjusting the adding ratio of Co/Mn to 10:1, the EAB achieved 5.68 GHz, nearly covering the whole Ku band. Besides, radar cross-sectional (RCS) simulations verify the MA capabilities and potential use of the materials. This work provides a convenient way to construct manganous oxide-based nanocomposites for high-efficiency MA and radar monitoring.

Tuning phase structure and electrochemical hydrogen storage properties of A5B19-type La–Y–Ni–Mn-based superlattice alloys by partial Al substitution

Rare earth-based superlattice alloys are essential anodes for high-performance nickel-metal hydride (Ni-MH) batteries. This study aimed to improve the overall electrochemical hydrogen storage properties of (La0.33Y0.67)5Ni18.1-xMn0.9Alx alloys by adjusting the Al content. The alloys predominantly consist of the 2H–Pr5Co19 phase, with Al atoms mainly occupying the 12k2 site at the [AB5]-1/[AB5]-2 boundary and subsequently the 12k1 site at the [A2B4]/[AB5]-1 boundary. As a result, a minimum subunit volume difference of 2.08 Å3 is observed at x = 0.6. Therefore, the Al substitution is responsible for the decrease in the dehydriding plateau pressure and the increase in discharge capacity. Among them, the alloy (La0.33Y0.67)5Ni17.5Mn0.9Al0.6 presents a discharge capacity of 361.2 mAh/g, a higher capacity retention S200 of 69.80 %, and better rate performance owning to the enhanced hydrogen diffusion rate through the multi-phase interface. This work demonstrates the potential of the (La0.33Y0.67)5Ni17.5Mn0.9Al0.6 alloy as high-performance Ni-MH battery anode.

Enhancing the cycle life of rechargeable Zn-air batteries via in-situ growth FeNi layered double hydroxide on Co3O4 air electrode

As a promising secondary battery, the short cycle life of Zn-air batteries (ZABs) severely limits their further application. The traditional air electrode could not maximize the OER activity of air electrode due to the existence of multiphase interface. In this work, FeNi layered double hydroxide (FeNi-LDH) without further hydrophobic treatment as main OER catalyst was in-situ grown on the initial Co3O4 air electrode (Ketjen Black as conductive carbon) surface by electrochemical deposition method. With a FeNi-LDH as main OER active component, assembled ZABs delivered an enhance cycle life of 38.1 h, 3.15 times than initial Co3O4 air electrode (12.1 h). The significant increase in cycle life is mainly due to the lower charging voltage caused by the FeNi-LDH layer with better OER catalytic activity than Co3O4, which reduces the ORR site inactivation and carbon oxidation rate. Therefore, after using multiwalled carbon nanotubes with better oxidation resistance as the conductive carbon instead of Ketjen Black and increasing the mass loading of Co3O4 air electrode from 2.0 to 4.0 mg cm−2, the FeNi-LDH layer can increase ZABs cycle life from 61.4 to 218.3 h. The in-situ electrodeposition FeNi-LDH on traditional air electrode strategy provides a simple method for enhancing the cycle life of ZABs.