Interface Morphology Research Articles

Instability mechanism and a fractal theory-based relative permeability model of immiscible two-phase displacement in rough fractures

The two-phase displacement in rock fractures is a critical scientific challenge in deep energy development projects, characterized by the intricate and dynamic flow patterns resulting from the complex fracture geometry and mutual interference between the two-phase fluids. The present study involves the construction of a three-dimensional rough fracture fine model using the fast Fourier transform and Gaussian distribution method. The phase field-finite element method is employed to simulate the dynamic displacement of water-oil flow and the evolution of the water-oil interface, aiming to investigate the impact of roughness, aperture, and wettability on the viscous fingering pattern observed in rough fractures. The numerical results indicate that the immiscible two-phase displacement presents a viscous fingering pattern at a high flow rate. Moreover, the greater the roughness is, the higher the number of fingering is, and the more volatile the change in displacement velocity is. The width of the wet-phase flow channel increases proportionally with the fracture aperture increasing. Furthermore, the morphology of immiscible two-phase interface within fractures is also influenced by the wetting angle, and the fingering, bifurcation, and crushing phenomena appear in the oil-wet state with the strong displacement interface instability. Finally, a fractal model of relative permeability for waterflooding in rough fractures is proposed based on the cubic law of flow and fractal dimension of aperture distribution, which has been validated through comparison with numerical results.

Machine learning-based study of dynamic shrinkage behavior during solidification of castings

Shrinkage cavities and porosity are the main defects generated during the solidification process of castings. The cause of these defects is the contraction of the alloy during solidification, with the last regions to solidify not receiving effective compensation from liquid metal, resulting in cavitation defects. Shrinkage cavities and porosity significantly reduce the mechanical properties of castings and shorten their service life, thus necessitating appropriate process elimination measures. Utilizing numerical simulation technology can effectively predict the shrinkage of castings during solidification and optimize the process based on simulation results, thereby reducing the occurrence of shrinkage defects, which is a low-cost and high-efficiency method. This paper presents a machine learning-driven dynamic mesh model to simulate the dynamic shrinkage behavior of castings during solidification. Cellular automata are used to simulate the solidification process of castings, dynamically marking the displacement of boundary points and calculating the displacement of other grids using RBF neural network algorithms and support vector machine algorithms, achieving dynamic simulation of the solidification process. The model was used to simulate the shrinkage cavity morphology of the Al-4.7%Cu alloy solidification process and corresponding casting experiments were designed for verification. Comparisons between simulation and experimental results indicate that this coupled method can effectively capture the deformation of castings caused by solidification shrinkage, the evolution of complex solid-liquid interface morphologies, and the deformation of internal grids within the castings. The simulation results have an error of no more than 2% compared to experimental results, providing a new approach for numerical simulation of the solidification process.

Optimizing explosive welding parameters of Al 5052 - WM - SiCp - Al 1100 composites through microstructural analysis and 3D welding window development

Explosive welding is a crucial technique for fusing metals and creating composite materials. This study investigates various combinations of Al 5052, wire-mesh, SiCp, and Al 1100 through explosive welding, adjusting welding parameters to alter cladded interface morphology. It evaluates resulting composites’ microstructure, tensile strength, shear strength, and impact resistance. Optimal welding outcomes occurred at a dynamic bend angle of 17.8 degrees. A wavelength to amplitude ratio of less than 8.4 shows improved clad strength. The maximum impact strength observed was 18.3 N-m in sample E22. The research introduces a 3D welding window, integrating kinetic energy, wavelength-to-amplitude ratio, and dynamic bend angle. This tool correlates microstructural attributes with material properties during the manufacturing process, enhancing understanding. The study emphasizes explosive welding’s potential and the importance of comprehending factors affecting product morphology and characteristics. The 3D welding window’s development offers promise in optimizing explosive welding and crafting tailored composites. Findings from this research are significant for the materials science and engineering community, offering insights crucial for advancement in the field.

Surface/Interface behaviour of atmospheric plasma sprayed NiTi alloy on stainless steel with the variation of critical plasma spray parameter

NiTi equiatomic composition is used in atmospheric plasma spraying (APS) machine to coat the stainless steel substrate. APS was conducted with varying critical plasma spraying parameters (CPSP) using NiTi powder as a coating element. After coating, the surface and interface morphology were characterised by XRD, SEM, and hardness tester. Higher CPSP yields better surface morphology. Surface roughness and porosity percentage decrease, and hardness increases from (455–844) Vickers hardness number with CPSP. The residual stress varies from 73 ± 1.1 MPa to −95 ± 1.9 MPa which shows the stress conversion of coating from tensile to compressive with an increase in CPSP. Coating failure occurs as a combined result of adhesion, cohesion and glue joint failure. At 865 CPSP, coating shows highest adhesion strength 42.13 MPa.

A novel approach for the removal of oxide film to achieve seamless joining during hot-compression bonding

The oxide film on the substrate surfaces can severely hinder the bonding quality during hot-compression bonding (HCB). To address the above issue, this investigation proposes a novel approach to enhance bonding quality by removing surface oxide film and encapsulating the interface to be bonded in sequence under vacuum. The principle of the approach was clarified, and an experiment platform used for implementing the approach was designed and developed. By considering 316H stainless steel as a testbed, the key parameter for laser ablation of the oxide films before HCB was determined. The HCB comparative experiments of substrates with or without treatment by the approach were carried out and the effectiveness of the approach was assessed by comparing the quality of bonding joints through interface morphologies and tensile properties. Results showed that a nearly seamless bond without thermal holding was achieved after adopting this approach. Further, it also showed improvement in the tensile properties both in elongation and the ultimate tensile strength (UTS). For instance, when using the proposed approach, the average UTS of 316H stainless steel joints improved from 371.17 MPa to 430.25 MPa whereas the average elongation increased from 26.41 % to 64.04 %. Although this investigation was directed to 316H stainless steel, the suggested approach can be applied to a wide range of other engineering materials to improve the joining quality.

Structure-performance relationship between denitration performance and catalytic interface morphologies of MnCeO /P84 catalytic filters

Structure-performance relationship between denitration performance and catalytic interface morphologies of MnCeO /P84 catalytic filters

Weld formation characteristics and strengthening mechanism of Al to steel laser-arc hybrid welding with additive manufactured Ni as transition layer

A novel Al to steel laser-arc hybrid welding with the additive manufactured of Ni as the transition layer was proposed. The millimeter-thick Ni transition layer effectively replaces the Fe-Al interface reaction with a Ni-Al interface reaction, significantly enhancing the joint mechanical performance. This paper systematically investigated the joint characteristics, including weld formation, interface microstructures, interface reaction mechanism, and mechanical properties. The results show that the laser-arc welding approach significant inhibits the dissolution of solid Ni in liquid Al and improve the stability of the welding process, resulting in good weld formation of the joint. At lower heat input, liquid Al bonds with solid Ni to form a brazed joining, resulting in an interface structure of Al/Al3Ni/Al3Ni2/Ni with an average reaction layer thickness below 2 μm. As the heat input increases, localized partial melting occurs above the solid Ni, forming compounds such as AlNi, Al3Ni2, Al3Ni, and residual Al. Mechanical property studies indicated that the joint strength and toughness were significantly improved. The highest tensile strength reached 195.6 MPa. Compared to joints without the Ni interlayer, the maximum tensile strength has improved by 87.5 %. Controlling Fe content within 5 % does not significantly deteriorate the interface morphology and tensile properties. The three point bending test shows that the transverse bending of the joint can reach 90° without cracks, and the longitudinal bending of the joint can reach 76.5°. The excellent mechanical properties of joint attributed to the toughness Al-Ni intermetallic compounds and their special scatter structure.

Experimental and theoretical analyses of the thermal conductivity of diamond /SiC composites with SiC matrix

Diamond/SiC composites with SiC matrix were prepared by using a liquid silicon infiltration method. The interface morphology and thermal conductivity of the composites have been analyzed by scanning electron microscopy (SEM), and a laser flash thermal conductivity test, respectively. The thermal resistance of the interface structures has been calculated by using the acoustic and diffusion mismatch models. After the addition of mono-sized SiC particles, an increased diamond content resulted in an increased thermal conductivity of the composites. After the addition of SiC with a graded mix-sized particle under fixed diamond content condition, although the residual Si content decreased, the thermal conductivity of the composites showed little changes. Furthermore, the thermal conductivity of the composites have been calculated by applying Cubic Structure (C-S) and Hasselman-Johnson (H-J) models. The result shows that the calculations based on the C-S model showed the best agreement with the experimental thermal conductivity of the experiments with the addition of mono-sized SiC particles compared to the results analyzed by the other calculation models. The calculations based on the H-J model showed the best agreement with the experimental thermal conductivity of the graded mix-sized SiC particles composites compared to results analyzed by the other calculation models.

Nonlinear Oxidation Behavior at Interfaces in Coated Steam Dual-Pipe with Initial Waviness and Cooling Temperature

A numerical simulation method is proposed to investigate the nonlinear growth of thermally grown oxide (TGO) on a novel coated steam dual-pipe system operating at 700 °C. Utilizing oxidation kinetics data from high-temperature water vapor experiments, the study examines interface stresses and morphology evolution, considering initial surface waviness and cooling temperature effects. The findings indicate that the parabolic law accurately describes the nonlinear growth of TGO during high-temperature water vapor oxidation, with the TGO growth oxidation rate constant being 4.5×10−4μm2/h. The growth rate of TGO thickness decreases with increasing oxidation duration. Stress concentrations are found to develop at TGO interfaces, particularly in regions with high curvature, and those with elevated wavy amplitudes. The primary factor influencing stress redistribution and morphology evolution is the wavy amplitude of the TGO. Additionally, variations in cooling temperature affect interface stresses along the axial direction of the pipe system during nonlinear oxidation, resulting in relatively minor changes in morphology.

(Invited) Integration and Optimization of 2D Transition Metal Dichalcogenides as Switching Layers in Memristors

Memristive devices possess the ability to dynamically adjust resistance based on previous voltage and current inputs. They represent a frontier in next-generation computational hardware, offering unparalleled potential for brain-inspired computing and neuromorphic engineering. Among the various configurations, electrochemical metallization (ECM) memristors feature a solid electrolyte layer sandwiched between two electrodes and perform resistive switching via filament formation (SET) and dissolution (RESET) [1]. Recent studies have focused on the integration of two-dimensional (2D) materials into the design of ECM memristors, aiming at improving performance and unlocking new functionalities [2-4]. 2D transition metal dichalcogenides and hexagonal boron nitride, in particular, are promising candidates for realizing memristors with ultra-low switching voltages, suitable for neuromorphic computing and artificial synapses [5, 6].In this talk, I will focus on vertical ECM memristor in crossbar configuration using chemical vapor deposited (CVD), atomic-thick MoSe2 as switching material, and Au/Cu as bottom/top electrodes. The devices exhibit nonvolatility and bipolar resistive switching behavior, with well-defined SET/RESET voltages (below 1V in absolute value) [7]. We performed atomic-scale investigations by transmission electron microscopy to unveil the filament formation mechanism within the MoSe2 layer. Our results shed light on the Cu/MoSe2 interface, particularly critical for memristor performance, providing key information on the intermixing and diffusion mechanisms of Cu atoms within the device structure.Furthermore, we studied the effect of XeF2 fluorination of the MoSe2 films to tune their surface properties and improve the ion transport kinetics across the interface with Cu. By carefully controlling the XeF2 process, we were able to induce structural and chemical modifications in the MoSe2, such as layer thinning and doping/implantation. This could provide a way of controlling the interface morphology and ultimately the performance and reliability of the memristive devices. Transport properties and X-ray photoelectron spectroscopy analyses provided insights into the fluorination-induced modifications on the MoSe2 surface, offering a framework for performance optimization. Overall, these findings rationalize the 2D materials-based ECM memristor operation and highlight the potential for advanced applications.

Does the substrate and a buffer layer have a greater influence on poly(3-hexylthiophene) films deposited by the chronocoulometry technique?

Abstract In this study, we investigate the interface morphology and optical properties of electrochemical poly(3-hexylthiophene) (P3HT) films deposited by electrochemical synthesis using the chronocoulometry technique on tin-doped indium oxide (ITO) and fluorine-doped tin oxide (FTO) and how the substrate used influences in the deposition of the films and their optical and morphological properties, as well as the buffer layer and the interface effect, with and without spin-coating films of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). P3HT polymeric films were synthesized and deposited via the oxidation of the 3-hexylthiophene (3-HT) monomer and characterized via Raman spectroscopy. The morphology and thickness of the P3HT layer present in the samples ITO/P3HT, FTO/P3HT, ITO/PEDOT:PSS/P3HT, and FTO/PEDOT:PSS/P3HT were carried out using atomic force microscopy (AFM). The optical and electronic gap energy of P3HT were calculated from UV‒Vis spectra and cyclic voltammetry curves, respectively. The photoluminescence (PL) spectra showed broad and asymmetrical line shapes fitted by multi-Gaussian functions identifying different emission species. Emission ellipsometry spectroscopy was performed to study the energy transference between adjacent polymer chains. Our results show a higher linear polarized light emitted by ITO/PEDOT:PSS/P3HT film, ∼37%, thus demonstrating a significant decrease in the energy transfer. Based on these results, the efficiency of organic solar cells can be improved via the interaction of the polymer/polymer interface.

Uniform anchoring of MoS2 nanosheets on MOFs-derived CoFe2O4 porous nanolayers to construct heterogeneous structural configurations for efficient and stable overall water splitting

Rational interfacial engineering and morphology modulation are recognized as effective strategies to modulate the electronic structure and improving the activity of spinel materials. In this paper, we report a strategy of Fe-induced creation of porous nanolayers of CoFe2O4 with unique morphology derived from MOFs by introducing ferrocene, and then constructed CoFe2O4/MoS2 heterostructures were fabricated by homogeneously anchoring MoS2 nanosheets onto the surface of CoFe2O4. The triple synergistic effect of heterogeneous interfaces, highly active Mo(IV) sites, and unsaturated S effectively accelerates the cycling process between Fe(III)/Fe(II) and Co(III)/Co(II), which in turn enhances the adsorption of reactive intermediates on the active sites, as further corroborates by density functional theory (DFT) calculations. As a result, the CoFe2O4/MoS2 heterostructured catalysts prepared without noble metals exhibit high catalytic performance, necessitating only 270 mV and 229 mV to achieve the current density of 100 mA·cm−2 for OER and HER respectively, which is superior to most of the reported catalysts of interest. In addition, when used in an alkaline electrolyzer, it provides a current density of 10 mA·cm−2 at 1.54 V cell voltage. This work provides a new way for the rational construction of bifunctional water electrolytic catalysts.

Microstructural Thermal Zones in Reaction of Nanoenergetics.

Despite the potential of nanoenergetics as promising energy sources with high energy densities and fast energy release, our limited ability to predict combustion speeds restricts the utilization of nanoenergetics. Here, we provide a comprehensive analysis of thermal microstructures subject to heterogeneous reactions and propose a new scaling for combustion wave speeds. To control reaction heterogeneity, two different particle interfacial morphologies of physically mixed and core-shell Al/CuO nanoparticles were synthesized. The combustion dynamics and temperature fields were obtained at micrometer-scale resolutions using high-speed and infrared cameras. Experiments showed that the core-shell Al/CuO exhibiting less reaction heterogeneity had a faster wave speed than the physically mixed counterpart, although the measured chemical reaction rates were lower. By employing the thermal structure analysis, we found that the shortened preheat zone and the lengthened reaction zone, attributed to the lower reaction onset temperature and reaction rate, led to the increased wave speed despite the lower reaction rate in the core-shell Al/CuO. From these analyses, we developed a new scaling that describes the combustion wave speeds in nanoenergetics based on intrinsic properties and thermal structures for both morphologies.

Influence of interface morphology on the magnetic damping of Al-sandwiched Permalloy thin films

Influence of interface morphology on the magnetic damping of Al-sandwiched Permalloy thin films

Improved Thermal Dissipation in a MoS2 Field-Effect Transistor by Hybrid High-k Dielectric Layers.

Transition metal dichalcogenides like MoS2 have been considered as crucial channel materials beyond silicon to continuously advance transistor scaling down owing to their two-dimensional structure and exceptional electrical properties. However, the undesirable interface morphology and vibrational phonon frequency mismatch between MoS2 and the dielectric layer induce low thermal boundary conductance, resulting in overheating issues and impeding electrical performance improvement in the MoS2 field-effect transistors. Here, we employed hybrid high-k dielectric layers of Al2O3/HfO2 to simultaneously reduce the interfacial thermal resistance and improve device electrical performance. The enhanced contact, greater vibrational phonon overlapping region, and stronger interfacial bonding force between the top Al2O3 layer and MoS2 promote the heat removal efficiency across the interface to the substrate. Under the same input power density, the temperature profile of the MoS2 transistor on the Al2O3/HfO2 has been largely reduced compared to that of the device on HfO2, with a maximum reduction of 49.5 °C. In addition, the field-effect mobility and current of MoS2 devices on the Al2O3/HfO2 high-k dielectric layers have been significantly improved, attributed to the depressed electron scattering and trap states at the interface. The design of the hybrid high-k dielectric layers provides an efficient solution to simultaneously improve the thermal and electrical performance of the two-dimensional devices.

Effects of Surface Roughness Obtained by Milling on Interface Bonding Quality for 316H during Metal Additive Forging

The metallurgical bonding quality of bonded joints is affected by the substrate surface condition in metal additive forging process, and the surface roughness serves as a critical indicator for the surface condition. Nevertheless, the effect of surface roughness obtained by milling on interface bonding quality(IBQ) remains unclear, resulting in the lack of effective evaluation criteria for surface roughness in the milling process. This study prepared samples with various surface roughness through milling, and introduced three parameters, Ra, Rc, and Rsm, to quantify surface roughness. The interfacial morphology, elemental distribution, and mechanical properties were used to characterize the IBQ, and the influence of surface roughness on the IBQ was finally revealed. The results show that a reduction in surface roughness obtained by milling leads to an improvement in interfacial bonding, more uniform elemental distribution, and enhanced mechanical properties, all of which were related to the size of the initial voids and the dynamic recrystallization mechanism of the bonding interface. And the interface bonding process with various surface roughness involves grain boundary bulging and continuous dynamic recrystallization mechanisms. Finally, the Ra 1.2 μm was recommended as the evaluation criteria in milling process, and a high-feed face milling cutter equipped with wiper edge was suggested for machining to achieve high-quality and high-efficiency cutting of the substrate. This study provide a theoretical basis and practical guidance for the efficient acquisition of substrate surfaces suitable for interface bonding in metal additive forging process.

Interplay of pore geometry and wettability in immiscible displacement dynamics and entry capillary pressure

Recent studies highlight the significant role of pore geometry and wettability in determining fluid–fluid interface dynamics in two-phase flow in porous media. However, current entry capillary pressure equations, rooted in the Young–Laplace equation, consider only cross-sectional details and apply wettability data measured on flat surfaces to complex three-dimensional (3D) pore structures, overlooking the coupled effect of contact angle and pore morphologies along the flow direction. This study employs the volume-of-fluid method to investigate the following: (a) How do combined effects of pore geometry and wettability control capillary pressure change, displacement efficiency, and residual saturations? (b) Can continuous two-phase flow be achieved at the pore scale? Through direct numerical simulations in constricted idealized-geometry capillary tubes and real pore structures, we vary the contact angle to characterize its impact on fluid–fluid interface morphology, entry capillary pressure (pce), and displacement efficiency. Our results show that during the drainage, pce temporarily decreases/turns negative under intermediate wettability conditions due to forced curvature rearrangement/reversal in the converging section. Local orientation angles along the flow direction are important in controlling the interface morphology and pce evolution. Moreover, intermediate contact angles enhance displacement efficiency due to curvature reversal, while insufficient corner flow during imbibition causes pore snap-off of the receding fluid, leading to higher residual saturation. The results challenge conventional methods in predicting entry capillary pressure, highlighting the need for incorporating 3D geometry in predictive models. Eventually, the insights underscore the importance of considering corner flow in controlling displacement efficiency within constricted geometries in pore network modelling studies.

Effect of various interlayers in NiTi to TC4 dissimilar joints by magnetic pulse welding

Magnetic pulse welding (MPW) has gained wide attention recently. In this paper, the connection of NiTi/TC4 dissimilar materials was achieved by adding pure Al, Cu, and Ni interlayers using MPW technology, and microstructure characterization and mechanical property tests were conducted to evaluate the joints. The results show that the atomic diffusion in the welding process plays a key role in the interface formation process. The interfacial morphology of joints consists of wavy and flat interfaces, and the mechanical interlocking of the wavy interface gives the joints excellent mechanical properties. The joints with the pure Al interlayer have the best mechanical properties, and the tensile shear force is 2.168 kN; the fracture forms of joints with different interlayers are all ductile fractures. In addition, the calculation results of the edge-to-edge crystal matching model show that the side with the high interface mismatch rate is where the joint failure problem occurs frequently.

Mechanical and failure behaviors of adhesively bonded dissimilar materials joints incorporating bio-inspired morphological irregularities

Adhesive dissimilar material joints between stainless steel grade 316L and polyethylene terephthalate glycol (PETG) plastic were examined, in which irregular interface morphologies inspired by natural sutures were incorporated. The joint interfaces exhibited various teeth-like, non-repetitive zigzag patterns based on a pseudo-randomization method and sutural interdigitation index. Effects of their irregularities on mechanical and failure characteristics of adhesive butt joints were studied by means of experiments and FE simulations. The cohesive zone model, Drucker-Prager plasticity model and ductile failure criterion were applied for the interface and PETG, respectively. Predicted load-displacement curves of joints with different teeth profiles were well validated. The degree of irregularity became higher to 20 %, 40 %, and 60 %, the joint strengths decreased by 1.47 %, 5.39 %, and 11.95 %, while the total energies to failure increased by 110.74 %, 129.33 %, and 161.23 %, accordingly. More inhomogeneous morphologies led to earlier local damage initiation, but enhanced damage evolution range by impeding abrupt joint separation. Smaller teeth angles provided higher joint strength, whereas significant declines of bonding strength were observed by too acute teeth angle due to excessive stress localization and resulting teeth breakage. The teeth angle of 45° enabled the superior joint performance owing to a proper combination of interlocking and large adhesive force under shear stress state. Finally, a key insight for designing an optimal dissimilar joint with morphological irregularities was provided.

Evolution of interface and surface morphology of WC/SiC multilayers with increase in number of bilayers

WC/SiC multilayer mirrors are promising elements for operation in the short wavelength range of hard X-rays and even gamma-rays. A set of WC/SiC multilayers with nominal bilayer thickness of 3.0 nm with 30, 50, 100, and 200 bilayers have been deposited by magnetron sputtering method. The evolution of interface and surface morphology with addition of the number of bilayers has been investigated. The methods of grazing incidence X-ray reflectivity, X-ray diffuse scattering, optical profiler, atomic force microscope, transmission electron microscopy and energy-dispersive X-ray spectroscopy have been used. It is found that the interface roughness plays a dominant role in interface imperfections of WC/SiC and it exhibits slight accumulation across the multilayers with the number of bilayers increasing. The surface roughness also increases in relatively high spatial frequency range as the number of bilayers has been added, due to the cumulative increase in interface roughness. The interface roughness accumulation ultimately contributes to the diminishment of optical performance of WC/SiC multilayers with a large number of bilayers. At the wavelength of 0.154 nm, a peak reflectivity of 69.2 % is achieved for a 100 bi-layer multilayer under the grazing incidence of approximately 1.5°, while lower reflectivity of 67.2 % for a 200 bi-layer multilayer.