Phase Interface Research Articles

Liquid-solid interface polymerization: A simple approach for efficient polyamide/polyethylene thin film composite total heat exchange membranes construction

A simple liquid-solid interface polymerization (LSIP) strategy was developed to prepare high performance polyamide (PA) based thin film composite (TFC) total heat exchange membranes (THEMs) to avoid the use of organic solvents and surfactant during the inverse phase interface polymerization processes between piperazine (PIP) and 1,3,5-benzenetricarbonyl trichloride (TMC) on porous polyethylene (PE) substrates. The non-polar organic solvent in the TMC organic phase coated on the surface of the PE surfaces was completely removed beforehand by evaporation to form polar TMC solid coating on the PE surfaces and facilitate the quick spreading of lately added aqueous PIP solutions, forming dense and highly cross-linked PA separation layers with superior total heat recovery efficiency and CO2 barrier property. The effects of TMC loading level, PIP concentration, and LSIP reaction time on the structure and performance of PA/PE-TFC THEMs were systematically investigated, leading to the formation of THEMs 0.20P-0.10T-6 with ultra-low CO2 permeance of 0.9 GPU, and high sensible heat exchange efficiency of 94.3 %, water vapor flux of 2128 g m−2·24 h−1, and enthalpy exchange efficiency of 76.8 %.

The selection mechanism of mineral bridges at the interface of stacked biological materials for a strength-toughness tradeoff

The strength-toughness tradeoff in biological materials such as nacre and bone is essentially due to their stacked microstructures formed by hard and soft phases. In some of these materials, purely soft phase acts as interface layers linking hard phases (platelets), while in some others, hard-phase bridges exist in the soft phase to form a hybrid interface. In order to disclose the selection mechanism of such different interface structures in biological materials, a novel shear-lag model with an interface consisting of alternatively distributed elasto-plastic (soft) and brittle-elastic (hard) segments is proposed. Using this model, solutions of tensile stress and tensile displacement in hard platelets and shear stresses in soft and hard interfacial segments are analytically achieved. Effects of the hybrid interface on the effective mechanical performances of the composite are analyzed, the results of which are well consistent with the existing experimental observations in biocomposites and bio-inspired composites. The most important finding is that the fracture strain of the soft phase has a decisive effect on the selection of a purely soft-phase interface or a hybrid interface of hard and soft phases in stacked biological materials in order to realize a tradeoff between strength and toughness. When the failure strain of the soft phase is relatively small, such as nacre, the purely soft-phase interface is too weak to transfer enough load to the platelet, and hard bridges are necessarily required to reinforce the interface and guarantee an efficient load transfer. When the soft phase has a sufficiently large failure strain, such as bone, the purely soft-phase interface is tough enough to sustain a large shear deformation, realizing an efficient load transfer and adequate utilization of all constituents, while an additional hard bridge is not conducive to the composite toughness due to its reducing effect on the interfacial shear deformation. The results not only help people gain a deeper understanding of the secrets behind the construction of different interfaces in biological materials, but also provide useful guidance for interface optimization design in strong and tough artificial materials.

Effects of drawing speed on microstructure and properties of Cu-Ni-Si alloy clad AA8030 alloy composites prepared by continuous casting composite technology

The Cu-Ni-Si alloy clad AA8030 alloy rod was prepared by continuous casting composite technology with gradient-varying drawing speeds, and the influences of drawing speed on the casting quality and microstructure of Cu-Ni-Si alloy clad AA8030 alloy rod were systematically studied. The drawing speed at which satisfactory continuous casting quality could be obtained was 90–120 mm/min. Meanwhile, axial columnar grains favorable for subsequent plastic processing were obtained, although the angle between columnar grains and axial direction increased with the increases of drawing speed. Moreover, with the drawing speed increasing from 90 mm/min to 120 mm/min, the thickness of composite interfacial layers was significantly increased, and the morphology of interfacial phases was gradually changed. The Cu-Ni-Si alloy cladding layer was cut from the composite to perform solution and aging experiments. The results showed that the solid solution effect of the as-cast Cu-Ni-Si alloy was consistent with that of the solution-treated Cu-Ni-Si alloy because of the rapid cooling characteristics of continuous casting composite technology, which solved the problem that the composite rod could not be solution treated as a whole due to the lower melting point of the Al core.

Electrolyte matching design for carboxylic acid-based organic K-storage anode

Carboxylic acid-based organic anodes are emerging as sustainable alternatives to traditional inorganic materials for potassium-ion batteries (PIBs), owing to their potential to improve both sustainability and K-storage performance. Herein, a readily available 4-fluorobenzoic acid (4FA) supported on ordered mesoporous carbon (4FA/CMK3) is proposed as a novel K-storage anode material. Importantly, we extensively investigated the compatibility of various electrolytes with the 4FA/CMK3 anode, focusing on electrolytes with tunable solvation structures to optimize electrode/electrolyte interfacial electrochemistry. A significantly decreased amount of free solvent in the optimized ether-based electrolytes compared to conventional ester-based electrolytes provides excellent compatibility with the modified 4FA/CMK3 anode, which promotes the formation of salt anion-derived interfacial phases, thereby improving K-storage performance. As a result, the optimized 4FA/CMK3||KFSI/DME storage system delivered a reversible capacity of 164 mAh/g with Coulombic efficiency above 99.8 % after 500 cycles at high current density of 200 mA/g. These excellent electrochemical properties are attributed to the synergistic effects of 4FA modification and electrolyte solvation structure modulation, which collectively mitigate the dissolution issues of organic actives and improve the cycling life of PIBs. This work presents a novel vision for designing PIBs with high energy density and long cycle life based on carboxylic acid-based organic electrodes.

NiMoO4 containing O-vacancy cooperated with bimetallic sulfides as efficient bifunctional electrocatalyst for overall water splitting

MoS2 is a potential transition metal sulfide (TMS) with excellent performance for hydrogen evolution reaction (HER) in acidic medium. However, MoS2 has poor stability owing to its metastable properties and therefore is easily oxidized to MoO3 which can hinder the HER process. In this work, MoO3 on the surface of the TMS is transformed to NiMoO4 with plentiful oxygen vacancies (Ov) favorable for HER and oxygen evolution reaction (OER) by an acid treatment to form an Ov-containing transition bimetallic sulfide/oxide catalyst (Ov-NiMoO4@Ni3S2-MoS2-rGO-NF, denoted as NiMoO4@NiMoS-rN). The electrocatalyst shows exceptional performance for HER and OER in terms of increased intrinsic activity, electron transfer efficiency, reaction kinetics and durability on account of the Ov, synergistic effect among different phases and bimetallic active sites. The overpotentials of NiMoO4@NiMoS-rN electrode when achieving 10 mA cm−2 are 45 mV and 195 mV towards HER and OER in alkaline, respectively, and the performance holds nearly unchanged during a 50-h stability test. When assembled to a two-electrode system, the current density of 10 mA cm−2 can keep steady for 50 h without degradation. The strategy combined by phase transition, interface and defect engineering via a facile method provides a practical idea for design and modulation of bifunctional electrocatalysts.

Improvement of silicon and epoxy phase interface by constructing rigid interpenetrating networks based on bismaleimide to enhance ablative, mechanical and thermal properties

Polysiloxanes are widely used in the preparation of ablative-resistant resins due to their tailored reactivity and ceramisable properties. Nevertheless, the mechanical and thermal properties may be negatively impacted by the presence of flexible chain segments and poor compatibility. In this study, the phase interface of silicon between epoxy was improved by a rigid interpenetrating crosslinked network constructing by bismaleimide. The pyrolysis of the silicone was inhibited and the oxidation resistance of the resin was enhanced. Both graphitization and ceramisation of the char layer during ablation are significantly improved. This endows the modified resin with outstanding ablative properties, with mass and linear ablation rates reduced to 0.0666 g/s and 0.0512 mm/s, respectively, which exceed those of some conventional ablative-resistant resins. Remarkably, the thermal and mechanical properties are significantly enhanced benefiting from the rigid crosslinked network and improved phase interfaces. Moreover, the destruction of mechanical properties of composites in high temperature environments caused by organosilicones has been effectively addressed. Bismaleimide/silicone co-modified epoxy resins can be used not only as ablative-resistant coatings, but also for the preparation of fire-resistant carbon fibre composites, providing a novel approach to the production of cost-effective, recyclable structural integrated materials for thermal protection.

Liquid-liquid reactions performed by cellular reactors

Liquid-liquid reactions play a significant role in organic synthesis. However, control of the phase interface between incompatible two-phase liquids remains challenging. Moreover, separating liquid acid, base and oxidants from the reactor takes a long time and high cost. To address these issues, we draw inspiration from the structure and function of cells in living organisms and develop a biomimetic 3D-printed cellular reactor. The cellular reactor houses an aqueous phase containing the catalyst or oxidant while immersed in the organic phase reactant. This setup controls the distribution of the phase interface within the organic phase and increases the interface area by 2.3 times. Notably, the cellular reactor and the aqueous phase are removed from the organic phase upon completing the reaction, eliminating additional separation steps and preventing direct contact between the reactor and acidic, alkaline, or oxidizing substances. Furthermore, the cellular reactor offers the advantages of digital design feasibility and cost-effective manufacturing.

Research on the characteristics of a new microbubble generator based on the Venturi tube

Microbubbles play a crucial role in various industries due to their advantages, such as small diameter, stable phase interface, and large specific surface area. Consequently, microbubble generators have entered a period of development. Among various microbubble generators, the Venturi tube stands out for its simple structure and high foaming efficiency. However, it still faces drawbacks, such as significant variations in particle size. Therefore, a new microbubble generator that utilizes the Venturi tube is currently being investigated. The tail of Venturi tube is connected with Tesla valve. According to the number and position of Tesla valves, various structures are formed: single-segment, multi-segment, and multi-segment same-side or different-side Tesla valves. Various structural characteristics are compared using Fluent software, and the optimal structural dimensions are determined using the Response Surface Methodology (RSM). The results show that the symmetrical distribution on both sides of Tesla valve is the best, and the proportion of microbubbles can be increased to 90%. The optimal dimensions are found to be an inclination angle (α3) of 34°, an inclination length (L8) of 29 mm, and a displacement length (L9) of 0. The optimized new structure is tested, and the reliability of the simulation results is verified.

Numerical simulation of droplet characterized by Rolie–Poly model with finite extensibility passing through cylinder obstacles

The deformation and rupture of viscoelastic droplet passing through cylinder obstacles in a microchannel are investigated using OpenFOAM. The constitute relationship of droplet is modeled by the Rolie–Poly model with finite extensibility, and the two-phase interface is tracked by the volume of fluid method. The effects of capillary number (Ca), the distance between cylinders (l1), relaxation time ratio (ξ), Weissenberg number (Wi), etc., on droplet deformation and rupture are mainly explored. When Ca decreases, the symmetry of droplet rupture changes and three behaviors of the droplet, i.e., symmetrical rupture, asymmetrical rupture, and non-rupture, can be captured. Further research shows that the stagnation area formed between cylinders is broken with the increase in l1, where the two sub-droplets merge again. Viscoelastic droplet with a smaller relaxation time ratio ξ is more likely to extend into thin and durable filament. Especially, when ξ=0.2, the filament will break many times during the stretching process. During above-mentioned two kinds of development, the normal stress difference develops obviously at the places, where the filament breaks or the sub-droplets combine together. This may imply that the normal stress difference facilitates the rupture and coalescence of droplets. In addition, with the increase in elasticity, the normal stress difference tends to develop at the phase interface.

Interface structure of α-Mg/14H-LPSO: First-principles prediction and experimental study

The interfacial structure of the α-Mg/14H-LPSO phase in rare earth-including magnesium alloy was investigated via high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging and first-principles calculations of density-functional theory. Eleven possible interfacial models were constructed according to the different terminations of the LPSO phase, and the corresponding interfacial energies were calculated, from which the four most stable structures (Ter1-MgY-hollow, Ter2-Zn-hollow, Ter3-MgYII-hollow and Ter4-Mg-bridge) were obtained. The interfacial phase diagrams related to the Y chemical potentials were obtained from the calculations, and the most stable interfacial structure was evaluated. Ter1-MgY-hollow and Ter2-Zn-hollow have the lowest interfacial energies in the range of −0.7 eV < ΔμY < −0.6 eV, where fluctuating change of state is the minimized and the interface is the most stable. The separation work of the two models was calculated to predict the bonding strength of the structures at both ends of the interface. The calculation results show that the maximum interfacial separation work is 1.45 J/m2 for the interface model of α-Mg and 14H-LPSO phase structure with Ter2-Zn-hollow termination.

Deep-sea glass sponges-like hollow porous ceramic fiber aerogel: Fabrication, anti-shrinkage and thermal insulation

Ceramic aerogels prepared using the polymer-derived ceramics (PDCs) route were extensively applied in the thermal insulation field with lightweight and high-temperature resistance. However, ceramic aerogels were susceptible to weight loss and volume shrinkage at high temperatures, leading to the collapse of the aerogel structure and a reduction in thermal insulation performance. In this paper, inspired by the skeletal structure of deep-sea glass sponges, hollow porous MHP-SiC-CA ceramic fiber aerogel was prepared by electrostatic spinning. The anti-shrinkage property of ceramic fiber aerogel was improved through the circular and spindle-shaped pores on the surface of hollow fibers. The gas-solid phase interface was increased by the abundant nanopore structure, leading to enhanced reflection and refraction of thermal radiation within the aerogel. The heat conduction and heat convection of the aerogel were reduced with the hollow and porous structure. The results presented that the ceramic fiber aerogel exhibited excellent anti-shrinkage properties, high specific strength, and ultra-low thermal conductivity. The material was expected to provide novel perspectives for the development of ceramic fiber aerogels applicable to ultra-high-temperature environments.

Polarization at the compositional interface in Nb-doped metastable TiO2-SnO2 solid solutions

Polarization architecture was incorporated into metastable Nb-doped TiO2-SnO2 to deliver electron accumulation at the localized TiO2-SnO2 compositionally fluctuating interface. Specimens were quenched from various holding temperatures to ambient temperatures in air to avoid bimodal decomposition into TiO2 and SnO2 endmembers. At the lowest sintering temperature of 1,400 °C, the mixed phase containing TiO2- and SnO2-rich compositions existed as an intermediate state to the single-phase solid solution. The phase boundary became more ambiguous with increasing sintering temperatures, and the compositional fluctuation size reduced to single nanometers at 1,500 °C. The permittivity due to the interfacial polarization, ε interface, increased steadily with increasing sintering temperature. The larger ε interface values at higher temperatures are attributed to the greater density of the compositionally fluctuating phase interface, which leads to greater electron accumulation at the energy barrier between the two semiconducting layers.

Creation of fully degradable and mechanically robust poly(4-hydroxybutyrate) films by filling modified starch

Chemically synthesized poly(4-hydroxybutyrate) (P4HB) is a new generation of biomass-derived and degradable semi-crystalline polymer with good comprehensive properties, but high costs limit its application. Starch, as an inexpensive natural polymer, can reduce the cost of P4HB products. However, starch lacks thermoplastic behavior and has poor compatibility with P4HB, thus its extensive use will inevitably impair the mechanical properties of P4HB. In this study, the ball-milling starch grafting process is adopted, which can simultaneously solve the two major deficiencies of starch, and the prepared ball-milling starch-g-polycaprolactone (BSt-g-PCL) has thermoplasticity and better compatibility with P4HB. BSt-g-PCL can melt near 55 °C, and the interweaving of its molecular chains with P4HB reduces the binding energy (Einteraction) of both, making the phase interface blurred or even disappear. Therefore, the elongation at break retention (REB) of P4HB/BSt-g-PCL can increase from 37.1 % to 74.3 % compared to P4HB/starch at the same filling (70 Phr). Additionally, BSt-g-PCL can exert the effect of accelerating P4HB degradation and still make it maintain excellent anti-aging ability. The ball-milling starch graft process provides a simple and effective method for the preparation of inexpensive fully biodegradable P4HB composite films with excellent mechanical properties.

Addition of AlO(OH) nanoparticles to assist stabilizing emulsion for digital light processing lightweight but robust porous alumina ceramics

It is proposed here that introducing AlO(OH) nanoparticles to build a wide range of particle size distribution to assist stabilizing emulsion and regulate its properties is an important prerequisite for using Pickering emulsion as digital light processing (DLP) feedstock. Combined with DLP, porous alumina ceramics with hierarchical porosity composed of macro-pores from the designed model (based on body-centered cubic lattice) and micro-pores formed by emulsion droplet, can be prepared by adjusting the microstructure of framework via changing AlO(OH) content, oil-to-water ratio and dispersant content. The AlO(OH) addition facilitates the further filling of particles at the phase interface of emulsion, thus increasing the viscosity and reducing the pore size. Porous alumina ceramics exhibit an average pore size distribution of 4.71 μm–6.06 μm, porosity of 71.92%–78.60 %, and relatively high compressive strength ranging from 5.02 MPa to 10.36 MPa, demonstrating a combination of high porosity and excellent mechanical properties.

Sorption kinetics of vermiculite-K2CO3 in thermochemical energy storage: Model evaluation and mechanism exploration

Thermal energy storage technology is crucial for building heating and domestic hot water supply, playing an essential role in optimizing energy utilization. Hydrated salts have emerged as prominent materials for thermochemical energy storage (TCES), with their sorption kinetics directly impacting thermal energy conversion efficiency. This study experimentally analyzes the microstructure and sorption performance of the EV/K2CO3 composite sorbent. Numerical analysis methods are employed to evaluate the validity of various sorption kinetics models and to elucidate the sorption mechanism and potential limitations of the composite sorbent. The findings indicate that EV can disperse K2CO3 salt particles while preserving a porous structure, thereby improving the sorption kinetics efficiency and stability of the EV/K2CO3 composite sorbent. At low relative pressure, EV/K2CO3 demonstrates a chemical adsorption mechanism, with nucleation models accurately predicting its sorption behavior, primarily limited by the nucleation and growth of hydrated salt crystals. At moderate relative pressure, EV/K2CO3 exhibits a mechanism involving both chemical adsorption and solution absorption, with diffusion models and the first-order model showing higher prediction accuracy, primarily limited by diffusion within or outside the product layer. At high relative pressure, EV/K2CO3 primarily undergoes solution absorption, with geometric contraction models and the first-order model displaying good predictive performance, primarily limited by the reaction phase interface. This study enhances comprehension of the sorption mechanism of the EV/K2CO3 composite, providing a scientific foundation for the development of high-performance TCES materials suitable for building and environmental applications.

Self-adaptive and time divide-and-conquer physics-informed neural networks for two-phase flow simulations using interface tracking methods

Physics-informed neural networks (PINNs) are emerging as a promising artificial intelligence approach for solving complex two-phase flow simulations. A critical challenge in these simulations is an accurate representation of the gas–liquid interface using interface tracking methods. While numerous studies in conventional computational fluid dynamics (CFD) have addressed this issue, there remains a notable absence of research within the context of PINNs-based two-phase flow simulations. Therefore, this study aims to develop a robust and generic PINNs for two-phase flow by incorporating the governing equations with three advanced interface tracking methods—specifically, the Volume of Fluid, Level Set, and Phase-Field method—into an improved PINN framework that has been previously proposed and validated. To further enhance the performance of the PINNs in simulating two-phase flow, the phase field constraints, residual connection and the time divide-and-conquer strategies are employed for restricting neural network training within the scope of physical laws. This self-adaptive and time divide-and-conquer (AT) PINNs is then optimized by minimizing both the residual and loss terms of partial differential equation. By incorporating the three different interface tracking methods, it efficiently handles high-order derivative terms and captures the phase interface. The case of single rising bubble in two-phase flow is simulated to validate the robustness and accuracy of the AT PINNs. The simulation's accuracy is evaluated by comparing its performance in terms of velocity, pressure, phase field, center of mass, and rising velocity with that of conventional PINNs and CFD benchmarks. The results indicate that the AT PINNs coupled with these interface tracking methods offers a satisfactory performance in simulating rising bubble phenomenon.

Enhancing interfacial compatibility and ionic transportation kinetics in lithium-rich manganese oxide via magnetron sputtering conformal coating with amorphous LiPON

This study presents the application of magnetron sputtering for the conformal coating of lithium phosphorus oxynitride (LiPON) onto lithium-rich manganese oxide (LRM) materials, aiming to enhance their electrochemical performance through a cost-effective and time-efficient strategy. The LRM with approximately 0.058 % mass loading of LiPON coating (LRM-2) exhibited remarkable reversible capacities of 173.9 mAh/g and 192.5 mAh/g over 200 cycles at 25 °C and 60 °C, respectively, under 1 C charge/discharge current density. Comprehensive characterization studies revealed that LiPON modification significantly improved lithium ionic conductivity, interfacial ion transport kinetics, and interface compatibility with the electrolyte. The stable cathode-electrolyte interface effectively mitigated structural damage to LRM particles, suppressed interfacial oxygen release-induced phase transformation, and stabilized the material’s microstructures. Our sputtering-based conformal coating strategy is easily accessible and low-cost, with significant commercial application potential, offering a promising universal approach for enhancing the electrochemical performance of LRM cathode powder materials.

Enhancing the Concentration Capability of Nonsupported Electrically Driven Liquid-Phase Microextraction through Programmable Flow Using an All-In-One 3D-Printed Optosensor: A Proof of Concept.

A versatile millifluidic 3D-printed inverted Y-shaped unit (3D-YSU) was prototyped to ameliorate the concentration capability of nonsupported microelectromembrane extraction (μ-EME), exploiting optosensing detection for real-time monitoring of the enriched acceptor phase (AP). Continuous forward-flow and stop-and-go flow modes of the donor phase (DP) were implemented via an automatic programmable-flow system to disrupt the electrical double layer generated at the DP/organic phase (OP) interface while replenishing the potentially depleted layers of analyte in DP. To further improve the enrichment factor (EF), the organic holding section of the OP/AP channel was bifurcated to increase the interfacial contact area between the DP and the OP. Exploiting the synergistic assets of (i) the continuous forward-flow of DP (1050 μL), (ii) the unique 3D-printed cone-shaped pentagon cross-sectional geometry of the OP/AP channel, (iii) the bifurcation of the OP that creates an inverted Y-shape configuration, and (iv) the in situ optosensing of the AP, a ca. 24 EF was obtained for a 20 min extraction using methylene blue (MB) as a model analyte. The 3D-YSU was leveraged for the unsupervised μ-EME and the determination of MB in textile dye and urban wastewater samples, with relative recoveries ≥88%. This is the first work toward analyte preconcentration in μ-EME with in situ optosensing of the resulting extracts using 3D-printed millifluidic platforms.

Study of Phase Transformations and Interface Evolution in Carbon Steel under Temperatures and Loads Using Molecular Dynamics Simulation

Carbon steel materials are widely used in mechanical transmission. Under different temperature and pressure service conditions, the microscopic changes of stress and strain that are difficult to detect and analyze by experimental means will lead to failure deformation, thus affecting their operational stability and life. In this study, the molecular dynamics method is used to simulate the heating–cooling phase transition process of common carbon steel materials. Austenite transformation temperatures of 980 K (0.2 wt.%) and 1095 K (0.5 wt.%) are acquired which is determined by the volume hysteresis before and after transformation, which is consistent with the results of JMatPro phase diagram analysis. The internal stress state of the material varies between compressive stress and tensile stress due to the change of phase structure, and the dislocation characteristics during the phase transition period are observed to change significantly. Then, an α/γ two-phase interface model is constructed to study the migration of the phase interface and the change of the phase structure by applying a continuously changing external load. At the same time, the transition pressure of α→ϵ is obtained with a value of 37 GPa under three different initial loads showing the independence of the initial load and the historical path. Based on the molecular dynamics simulation and the phase diagram calculation of the carbon steel, the analysis method for the microstructure transformation and the stress–strain behavior of the phase interface under the external load can provide a reference for the design of microstructure and mechanical properties of alloy steel in the future.

Effect of dissolved oxygen on corrosion behavior and mechanism of X70 pipeline steel in simulated low temperature bentonite-containing alkaline chloride environment

Effect of dissolved oxygen (DO) on the corrosion behavior of X70 pipeline steel in low temperature bentonite-containing alkaline chloride environments was comprehensively investigated. The cathodic reduction reaction is inhibited and corrosion current density gradually descent as the DO decreases, resulting in a significant improvement in the corrosion resistance of X70 pipeline steel. The content of Fe3O4 and α-FeOOH in the corrosion products film increases, refinement of rust grains and crack decreases effectively suppressing the penetration of corrosive substances. Pitting initiates within ferrite grains and at phase interface, while reducing the DO can restrain the chemical dissolution of MnS to retard the pit initiation.