Interfacial Structure Research Articles

Global dynamics and topology of two-phase mixing layer flow through simultaneous gas and liquid velocity measurements

This study reports the first time-resolved particle image velocimetry characterization of a planar two-phase mixing layer flow, whose velocity field is measured simultaneously in gas and liquid streams. Two parallel air and water flows meet downstream of a splitter plate, giving rise to an initially spanwise invariant configuration. The aim is to elucidate further the mechanisms leading to the flow breakup in gas-assisted atomization. The complete experimental characterization of the velocity field represents a database that could be used in data-driven reduced-order models to investigate the global behaviour of the flow system. After the analysis of a selected reference case, a parametric study of the flow behaviour is performed by varying the liquid ( $Re_l$ ) and gas ( $Re_g$ ) Reynolds numbers, and as a consequence also the gas-to-liquid dynamic pressure ratio ( $M$ ), shedding light on both time-averaged (mean) and unsteady velocity fields. In the reference case, it is shown that the mean flow exhibits a wake region just downstream of the splitter plate, followed by the development of a mixing layer. By increasing both $Re_l$ and $Re_g$ , the streamwise extent of the wake decreases and eventually vanishes, the flow resulting in a pure mixing layer regime. The spectral analysis of the normal-to-flow velocity fluctuations outlines different flow regimes by variation of the governing parameters, giving more insights into the global characteristics of the flow field. As a major result, it is found that at high $Re_g$ and $M$ values, the velocity fluctuations are characterized by low-frequency temporal oscillations synchronized in several locations within the flow field, which suggest the presence of a global mode of instability. The proper orthogonal decomposition of velocity fluctuations, performed in both gas and liquid phases, reveals finally that the synchronized oscillations are associated with a low-frequency dominant flapping mode of the gas–liquid interface. Higher-order modes correspond to interfacial wave structures travelling with the so-called Dimotakis velocity. For lower gas Reynolds numbers, the leading modes describe higher frequency fingers shedding at the interface.

Optimizing Intermediate Adsorption on Pt Sites via Triple-Phase Interface Electronic Exchange for Methanol Oxidation.

For the most commonly applied platinum-based catalysts of direct methanol fuel cells, the adsorption ability toward reaction intermediates, including CO and OH, plays a vital role in their catalytic activity and antipoisoning in anodic methanol oxidation reaction (MOR). Herein, guided by a theoretical mechanism study, a favorable modulation of the electronic structure and intermediate adsorption energetics for Pt active sites is achieved by constructing the triple-phase interfacial structure between tin oxide (SnO2), platinum (Pt), and nitrogen-doped graphene (NG). From the strong electronic exchange at the triple-phase interface, the adsorption ability toward MOR reaction intermediates on Pt sites could be efficiently optimized, which not only inhibits the adsorption of CO* on active sites but also facilitates the adsorption of OH* to strip the poisoning species from the catalyst surface. Accordingly, the resulting catalyst delivers excellent catalytic activity and antipoisoning ability for MOR catalysis. The mass activity reaches 1098 mA mg-1Pt, 3.23 times of commercial Pt/C. Meanwhile, the initial potentials and main peak for CO oxidation are also located at a much lower potential (0.51 and 0.74 V) against commercial Pt/C (0.83 and 0.89 V).

Insight into the Grain Refining Mechanism of Al–Ti–C and the Interfacial Properties between the Inoculants and Aluminum

The grain refinement mechanism of Al–Ti–C grain refiners used in the casting procedure of aluminum has been studied by first‐principles calculation. Considering the controversy over Al3Ti, TiC, or Al3Ti–TiC as nucleation sites, the adsorption behavior of possible nucleation surfaces for Al atoms, including adsorption energies and adsorption sites, as well as the interfacial properties of Al/Al3Ti/TiC are calculated and compared. In the results, it is shown that the Al3Ti(112) surface has a stronger adsorption capacity for Al than TiC. By using the edge‐to‐edge matching crystallographic model and the calculation of the adsorption energy, it is found that the monolayer Al3Ti(112) can be stabilized on the TiC(100) surface, and the combination of TiC and monolayer Al3Ti can significantly improve the adsorption capacity of Al. Interfacial electronic structure analysis shows stronger chemical bonding between Al and Ti at the Al/Al3Ti/TiC interface compared to Al/Al3Ti, which explains that the monolayer Al3Ti covering the TiC surface has the strongest adsorption capacity for Al atoms. Therefore, it is speculated that TiC with a monolayer of Al3Ti covering the surface will serve as a potential nucleation site during grain refinement, which will provide a theoretical reference for future research work.

Boosted carbon electrocatalytic effect towards sensing and green energy applications by tailoring the catalyst-support interface on a nature-inspired solution

Carbon electrodes are widely accepted as very versatile platforms, with applications ranging from electrocatalysis to sensors and other devices, like fuel cells and water electrolyzers. However, there are still difficulties given that over time, at high potentials, the oxidation of carbon materials (as a catalyst and/or catalyst support) can play a detrimental role, undermining the efficiency and stability of the electrochemical processes and devices performance. In this paper, it is reported the research work followed by resourcing to electrochemical analytical techniques, like cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), along with complementary atomic force microscopy (AFM) and water contact angle (WCA) measurements. These techniques were used to characterise glass-type and paper-based carbon electrodes. On a nature-inspired solution, we took advantage of the different interfacial carbon-support hierarchical porous structures to boost the carbon electrocatalytic effect towards sensing the ferri/ferrocyanide redox couple ([Fe(CN)6]3-/4−) in aqueous solution. It is shown that the best results were achieved with carbon paper electrodes without wet proofing, given its hierarchical porous structure and absence of the insulating binder. This research endeavors to contribute to the ongoing advancements in the field of electrochemical green energy conversion by exploring innovative approaches and materials, with the ultimate aim of developing carbon substrates that not only enhance performance but also promote environmental sustainability.

In-situ topotactic synthesis of decahedron BiVO4/2D networks Bi2S3 heterojunctions for efficient Cr(VI) reduction: Improved charge separation and imaged at the single-particle level

Epitaxial heterostructure has an optimized interfacial electronic structure compared to the traditional random heterostructures. However, accurately monitoring the interfacial charge transfer dynamics remains a grand challenge. We report here that single-particle spectroscopy techniques address this challenge by performing photoluminescence (PL) lifetime imaging and spectral fitting of interfacial micro/nano regions. A novel facet-selective BiVO4/2D nano-network Bi2S3 heterostructure is synthesized by a simple hydrothermal method. Single-particle PL spectroscopy shows that the PL emission at the oriented epitaxial heterojunction interface in BVO/S-O is weakened, and the PL lifetime increases by 213 % and 105 % compared to a single BiVO4 and random heterojunction particles, respectively, indicating that the topological heterojunction interface effectively promotes the separation of charge carriers. In addition, the possible mechanism of photocatalysis was also discussed in detail. Our work reveals the advantages of unique spatial structures and topological epitaxial interfaces in charge separation, which has great prospects for photocatalytic applications.

Unraveling the interfacial structure of TA2 titanium-A36 steel composite plate and its corrosion behavior in marine environment

In this study, the microstructure and corrosion behavior of the interface of a titanium-steel composite plate were analyzed and compared with that of cladding material and steel substrate. The results showed that the interface exhibited a complex laminar structure. The mass losses after the salt spray test indicated an accelerated corrosion effect at the composite interface, and the effect diminished with the extension of corrosion time. A significant accelerated corrosion crack was observed at the interface after the corrosion test. Furthermore, the multiple corrosion mechanism was elaborated in combination with electrochemical activity test in different regions of the composite interface.

Synergistic photothermal catalytic oxidation of methanol and toluene mixture over Co-MOFs-derived catalyst: Interfacial and promotion effects

Herein, a series of Co/CoOx@CN nanocomposites with tunable synergistic interfacial structure were successfully obtained by a facile pyrolysis treatment. Among these nanocomposites, the nanocomposite pyrolyzed at 500 °C (denoted as Co/CoOx@CN-500) exhibited the best methanol photothermal catalytic activity (97% methanol conversion and 96% CO2 yield) under simulated solar irradiation. Compared with Co nanoparticles and Co@CN, Co/CoOx@CN-500 showed higher methanol photothermal catalytic activity. Moreover, the Co/CoOx@CN-500 also displayed a good ability to degrade methanol under outdoor natural solar. Such excellent photothermal activity mainly benefited from the strong interaction between the metals Co, CoOx and graphitic-carbon, which enhanced the photothermal effect by inducing the high work temperature, and the surface adsorb oxygen species of Co/CoOx@CN-500. Besides, the promotion effect of methanol on toluene oxidation was observed over Co/CoOx@CN-500 for the photothermal catalytic oxidation of the methanol and toluene mixture relative to their individual component. Water molecules did not affect the promotion effect of methanol on the photothermal catalytic oxidation of toluene. Reaction mechanism studies showed that 2-methylbenzaldehyde, the key intermediate formed by the reaction of formaldehyde generated by methanol oxidation and toluene, is the main reason for the improvement of the oxidation activity of toluene.

Microstructure and mechanical properties of SiCp/CF/Al hybrid composites with heterostructure constructed by macroscopic “core-shell” structure

Designing heterostructure is an effective way to comprehensively improve the strength-ductility of composites. However, the current methods of heterostructure integration consumes a large amount of energy. In this study, a macroscopic “core-shell” structure is designed with low cost and low energy consumption. The SiC particles (SiCp) and carbon fiber (CF) reinforced aluminum-based hybrid composite (SiCp/CF/Al) with heterostructure was fabricated utilizing the spark plasma sintering (SPS) method. The microstructure, interfacial structure, and mechanical properties of the SiCp/CF/Al before and after hot rolling were comprehensively investigated. The results revealed that the Vickers hardness values of the rich particle zone with high SiCp content were 54.32% and 48.10% higher than those of the poor particle zone before and after hot rolling, respectively. The synergistic strengthening effect of SiCp and CF significantly enhanced the yield strength and plasticity of the SiCp/CF/Al. Before and after hot rolling, the yield strength of SiCp/CF/Al was 242.68% and 173.16% of single CF-reinforced Al matrix composites, respectively. The extrinsic toughening was achieved through crack passivation and deflection at the interface of the rich particle zone and poor particle zone. Furthermore, the hindering and storing effects of the SiCp and CF on dislocations represented the primary intrinsic toughening mechanisms.

Generalized Substrate Screening GW for Covalently Bonded Interfaces.

An accurate description of the interfacial quasiparticle electronic structure is key to the design of heterogeneous materials. While the first-principles GW approach is state-of-the-art, the computational cost is high for large interface systems. This has led to the substrate screening GW approach for weakly coupled interfaces, which breaks down for covalently bonded interfaces. In this work, we present the generalized substrate screening GW approach, based on the following two considerations: (i) the contribution of the interfacial covalent bond to the polarizability can be efficiently calculated with a low energy cutoff; (ii) the contribution of the deprotonated adsorbate to the interface polarizability can be well approximated by that of the protonated molecule. Our approach is exemplified using interfaces formed between benzene-1,4-dithiol (BDT) and Au(111), which feature the widely used Au-S bonds in experiments. Our work provides a robust and simple scheme for accurate and efficient GW calculations of covalently bonded interfaces.

Carbide particle strengthened Cu/graphene composites in-situ fabricated by alloying

Interface structure plays a crucial role in enhancing the electrical conductivity and mechanical properties of copper/graphene composites, thereby influencing their potential applications. In this study, we introduced carbide-forming elements (Cr, Nb, W) and expected to generate nano carbide particles at the interface to improve the interface bonding by in-situ preparation. Among these, the CuCr/graphene composite exhibits the best performance with electrical conductivity of 97 % IACS and hardness of 82 HV. The cold-drawn wire possesses a high tensile strength of 518 MPa. At the Cu/graphene interface, an optimal quantity of nanometer chromium carbide (Cr3C2) particles in situ formed, enhancing the interface bonding and resulting in the composite achieving both high conductivity and high strength.

Achieving high thermal conductivity in CNTs@GF/Al laminates via a rapid and simple strategy

The present work developed a rapid and simple fabrication strategy to achieve the high thermal conductivity (TC) in graphite film (GF)/Al laminates. CNTs@GF prepared by spray flash technique was selected as reinforcement in Al matrix, then consolidated with Al foils by vaccum hot-pressing sintering. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy were used to evaluate the GF and interface structure. The results revealed that no interfacial reaction products were generated in the highly dense composites. Specially, due to the heat conduction channel and interlocking effects of CNTs on GF/Al interface, the laminated composite containing 56.5 vol% CNTs@GF showed an in-plane TC of 897 W (m k)−1 without bending strength sacrifice. The present work paves an efficient new way to design and fabricate GF/Al laminates for potential thermal management application.

Non-aqueous Liquid Electrolyte Additives for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have been recognized as one of the most promising new energy storage devices for their rich sodium resources, low cost and high safety. The electrolyte, as a bridge connecting the cathode and anode electrodes, plays a vital role in determining the performance of SIBs, such as coulombic efficiency, energy density and cycle life. Therefore, the overall performance of SIBs could be significantly improved by adjusting the electrolyte composition or adding a small number of functional additives. In this review, the fundamentals of SIB electrolytes including electrode-electrolyte interface and solvation structure are introduced. Then, the mechanisms of electrolyte additive action on SIBs are discussed, with a focus on film-forming additives, flame-retardant additives and overcharge protection additives. Finally, the future research of electrolytes is prospected from the perspective of scientific concepts and practical applications.

Electronic conductivity in metal-graphene composites: the role of disordered carbon structures, defects, and impurities

This paper explores the transport properties of aluminum-carbon composite material via ab initio methods. Interfacial and electronic dynamics of the aluminum-graphene interface structure were investigated using models of amorphous graphene added to an aluminum matrix. We examine the impact on electronic conduction caused by the presence of nitrogen impurities within the interfacial amorphous graphene layer. We elucidate the conduction mechanisms by using a projection of the electronic conductivity into space.

Effect of laser pre-treatment on adhesive joint performance and evaluation of interfacial strain distribution using mechanoluminescence

ABSTRACT In this study, factors that improve bonded joints structural response through laser surface pre-treatment on aluminum surfaces were investigated. Specifically, the focus was put on analyzing the laser treatment conditions, formation of the interface structure, and behavior of interface strength at the adhesive interface. The results revealed a specific range of laser treatment conditions in which tensile shear strength and fracture mode are stable. Although laser-treated adhesive joints showed cohesive failure similar to that observed in sandblasting or chemical treatment during the double cantilever beam test, the fracture toughness value was improved by a factor of 2 and 1.5, respectively. The laser-induced microstructure on the aluminum interface contributed to the improvement of fracture toughness. Furthermore, observation of the adhesive layer using a microscopic mechanoluminescence measurement system revealed that changes in the 3D structure of the interface significantly altered the stress luminescence pattern reflecting strain. As a result, direct visualization of interface strengthening via laser processing was achieved.

Study on microstructures, properties and mechanisms of sinter-joining refractory metal W[sbnd]30Si powders and sputtering targets by spark plasma sintering technique

The development of semiconductor integrated circuits has been limited by the low utilization rate of refractory metal sputtering targets. Spark plasma sintering (SPS) technology has shown great superiority in the sintering and joining of materials, which can be applied to the repair of waste targets and improve the utilization rate. In this study, SPS technology was used to sinter-join the high-purity refractory metal W30Si sputtering powder and the target for integrated circuits to determine the optimal repair process and repair mechanism. The morphological characteristics, grain size, relative density, and Vickers hardness of the repair layer (powder-sintered body) and the target under different joining times were analyzed, and the interface structure and properties of the W30Si joint were also studied. It was found that the W30Si joint was composed of WSi2 and Si phases. The grain size, relative density, and Vickers hardness of the W30Si powder-sintered body and targets increased with the joining time. When the joining time was 10 min (1200 °C), the W30Si joint formed a “zigzag” joining interface, and the bending strength, relative density, grain size, Vickers hardness, and thermal conductivity of the joint were similar to those of the pristine target. In addition, the physical model of SPS sintered and joined refractory metal powders and targets was constructed. Studies have shown that the sinter-joining consists of three stages: early stage, middle stage, and late stage. Among them, the middle stage included two steps that may occur simultaneously, namely the sintering of refractory metal powders and the joining of refractory metal powders with the target, involving pressure welding, micro-arc welding, resistance welding, and diffusion welding mechanisms. This work can provide theoretical guidance for the optimal design of the SPS repair process for refractory metal W30Si sputtering targets.

Chitooligosaccharide facilitated the Co-stabilization of ferritin-based dual-compartmental Pickering emulsions: The effect and contribution of chitooligosaccharide molecular weight

Ferritin based dual-compartmental Pickering emulsions possess great potential for co-encapsulating different cargos and facilitating their synergetic functionalities. However, the poor stability of such emulsions has greatly limited their practical application. Herein, the aim of this study was to fabricated a stable dual-compartmentalized emulsion through the self-assembly of Marsupenaeus japonicus ferritin (MF) and chitooligosaccharide (COS) into robust interfacial and continuous network structure. Compared to individual MF and COS, MF/COS assemblies exhibited great amphiphilicity and were easier to adsorb onto the oil/water interface, thus generating stable emulsion even at higher oil phase fraction (70%). Moreover, the different molecular weight (1000 Da, 1500 Da, and 3000 Da) of COS significantly affected the properties of MF/COS emulsions. Specifically, COS with molecular weight of 3000 Da (COS3000) displayed the best stability against creaming and phase separation during storage and thermal treatments. Rheological analysis confirmed that COS3000 can significantly improve the viscoelasticity and anti-deformation performance of MF/COS stabilized emulsion due to the long mainchain structure. Moreover, confocal laser scanning microscopy revealed that MF/COS assemblies can not only generate the interfacial layer but also form dense continuous phase networks. Besides, a combination of UV/Vis absorption spectrometry and chemical reagent interference analysis implied that electrostatic interactions, hydrogen bonding, and hydrophobic interactions were mainly involved in the intermolecular binding between MF and COS, and COS3000 with more charges and binding sites allowed for stronger interactions with MF at the oil/water interface and continuous network, resulting in a higher emulsion stability. Overall, this work highlighted that COS can significantly facilitate the co-stabilization of ferritin-based dual-compartmental emulsions, promoting their application for the co-encapsulation and delivery of different cargos.

Controlled Growth of Metal Atom Arrays on Graphdiyne for Seawater Oxidation.

Advanced atomic-level heterointerface engineering provides a promising method for the preparation of next-generation catalysts. Traditional carbon-based heterointerface catalytic performance rely heavily on the undetermined defects in complex and demanding preparation processes, rendering it impossible to control the catalytic performance. Here, we present a general method for the controlled growth of metal atom arrays on graphdiyne (GDY/IrCuOx), and we are surprised to find strong heterointerface strains during the growth. We successfully controlled the thickness of GDY to regulate the heterointerface metal atoms and achieved compressive strain at the interface. Experimental and density functional theory calculation results show that the unique incomplete charge transfer between GDY and metal atoms leads to the formation of strong interactions and significant heterointerface compressive strain between GDY and IrCuOx, which results in high oxidation performances with 1000 mA cm-2 at a low overpotential of 283 mV and long-term stability at large current densities in alkaline simulated seawater. We anticipate that this finding will contribute to construction of high-performance heterogeneous interface structures, leading to the development of new generation of GDY-based heterojunction catalysts in the field of catalysis for future promising performance.

Enhancing PEO coating on TC6 alloy through in-situ synthesis of MoSe2—Towards more efficient wear-reducing lubrication and wear resistance

Plasma electrolytic oxidation (PEO) has demonstrated significant enhancements in the mechanical properties and corrosion resistance of titanium alloys. Despite these advantages, the presence of micropores and microcracks in the coating can still detrimentally impact tribological properties. This paper introduces a novel approach involving the in-situ growth of a surface structure. The resulting interface structure exhibits outstanding tribological properties under a load of 3 N and a speed of 1.5 cm/s. In contrast to prior studies, improvements are made to the electrical parameters and electrolyte formula of Plasma electrolytic oxidation, facilitating the in-situ growth of MoSe2. This results in the formation of a lubricating layer and a robust TiO2 ceramic coating with excellent adhesion. A systematic analysis of friction, wear characteristics, reveals that MoSe2 in situ grow on the surface of the PEO coating, within micropores, microcracks, and crater structures after hydrothermal treatment. This process significantly enhances the microporous structure of the coating, with the MoSe2 film forming a dense and uniform interlocking layer with the PEO lower layer. Dry friction test experiments demonstrate a 33.7% reduction in friction coefficient and a 29% decrease in wear rate compared to the PEO sample, indicating the synergistic effect between the MoSe2 film and the PEO coating.

Concentration-Driven Interfacial Amorphization toward Highly Stable and High-Rate Zn Metal Batteries.

The interfacial structure holds great promise in suppressing dendrite growth and parasitic reactions of zinc metal in aqueous media. Current advancements prioritize novel component fabrication, yet the local crystal structure significantly impacts the interfacial properties. In addition, there is still a critical need for scalable synthesis methods for expediting the commercialization of aqueous zinc metal batteries (AZMBs). Herein, we propose a scalable concentration-controlled method for realizing crystalline to amorphous transformation of the Zn metal interface with exceptional scalability (>1 m2) and processing consistency (>30 trials). Theoretical and experimental analyses highlight the advantages of amorphous ZnO, which exhibits moderate adsorption energy, strong desolvation ability, and hydrophilicity. Employing the amorphous ZnO-coated zinc metal anode (AZO-Zn) significantly enhances the cycling performance, impressively maintaining 1000 cycles at 100 mA cm-2. The prototype AZO-Zn||MnO2@CNT pouch cell demonstrates a capacity of 15.7 mAh and maintains 91% of its highest capacity over 100 cycles, presenting promising avenues for the future commercialization of AZMBs.

Construction of oxygen-vacancy-rich 2D nitrogen-doped carbon nanosheets with CoFe@CoFe2O4 heterogeneous interfacial structure for rechargeable Zn–air batteries

Integration of cations doping by using unpaired high-spin electrons through the valence state substitution is deemed as a prospective strategy for construction of oxygen vacancies, regulation of inner electronic structures and enhancement of surface properties. Herein, an effective strategy is proposed to construct massive oxygen vacancies into 2D nitrogen-doped carbon nanosheets by the design of heterogeneous interfaces between CoFe alloy and CoFe2O4 nanoparticles. The valence state transition for Fe and Co endows electronic transfer capability and charge density around the oxygen atoms. The prepared CoFe-CoFe2O4@NCs-4 catalyst exhibits maximum content of oxygen vacancies (Density of Ovac 50.1 %). It shows excellent ORR activity with a half-wave potential of 0.83 V and OER overpotential of 320 mV. Reversible Zn-air batteries assembled by the CoFe-CoFe2O4@NCs-4 catalysts exhibit a power density of 106.32 mW cm−2 and durable stability (500 h at the current density of 10 mA cm−2), which also are superior to those of the commercial 20 wt% Pt/C + RuO2 catalyst. The excellent bifunctional catalytic performance can be attributed to synergistic effects between massive oxygen vacancies, ultrahigh specific surface area (545.9 m2 g−1) and heterogeneous interfacial structure. This work provides valuable insight into designing efficient bifunctional oxygen electrocatalysts for rechargeable Zn-air batteries.