Distortion Of Interface Research Articles

Achieving enhanced toughness of a nanocomposite coating by lattice distortion at the variable metallic oxide interface

Ceramic coatings are in general a kind of brittle material because they are predominantly made up of ionic crystals that avoid dislocation motion caused by lattice distortion. In this regard, a remarkable toughened ZrO2/MgO nanocomposite coating is obtained by the plasma electrolytic oxidation (PEO) process and in-situ synthesized ZrO2 with quantitative control approach. It is revealed that the toughening behavior of the ZrO2/MgO coating is related to the coordination and diversion of lattice distortion at the metallic oxide interface, which induces distinct dislocation motion at the interface. The semicoherent interface between m-ZrO2 and MgO is verified to act as a buffer to realize toughening of the nanocomposite coating through dislocation slipping induced by lattice coordinated distortion. Simultaneously, significant interfacial lattice distortion transfer and dislocation pinning are discovered at the semicoherent interface between t-ZrO2 and MgO, which are beneficial to toughness enhancement of the nanocomposite coating. The results indicate that the toughening effect occurs along with dislocation slipping and pinning caused by lattice distortion of the ZrO2/MgO semicoherent interface, which enables the toughness of novel nanocomposite coating to reach 2.7 times of the traditional PEO coating.

Joining CFRP/Ti stacks by directed energy deposition: Surface topography effects on interface formation and bonding

Compared to traditional joining techniques, the directed energy deposition (DED) technique enables the fabrication of carbon fiber reinforced polymer (CFRP)/titanium (Ti) stacks with a tailored three-dimensional (3D) Ti structure. In this work, we designed and structured four surface topographies on Ti sheets to manipulate the CFRP/Ti contact surfaces. The effects of surface topography on interfacial formation mechanism were investigated by experimental and numerical approaches. The results found that the pores dominated interfacial structures in CFRP/Ti stacks without surface patterns, yet physical gaps played a vital role in line/grid-patterned CFRP/Ti stacks. The interfacial bonding strength significantly improved when applying as-patterned Ti sheets, which was attributed to the prevented slippage or shearing by penetrated grooves as well as alleviated interfacial residual stress and distortion. This paper uncovered the interfacial formation and bonding mechanisms of CFRP/Ti stacks with different surface topographies, paving a way for improving the mechanical performance of metal/polymer stacked components used in multiple industries.

Lattice Expansion and Electronic Reconfiguration of MnCu Oxide Catalysts for Enhanced Transfer Hydrogenation of Levulinate

Lattice-strained metal oxides often display enhanced catalytic activity and selectivity on activation of C–H, C═C, C═O, and O–H bonds in bio-oxygenates. However, limited experimental studies have been conducted on the structure sensitivity for tandem reactions, particularly on complicated surface redox chemical chain reactions over strained oxide materials. In this work, we employed transfer hydrogenation of levulinate as a representative example to illustrate how lattice strain affects tandem oxidation (dehydrogenation, C–H/O–H bond cleavage) and reduction (hydrogenation, C═O bond saturation) reactions. The key finding is that lattice strain at MnOx–CuOx boundaries within bimetallic MnCu oxides leads to a highly unsymmetrical strain across the interface and lattice distortion. Such unique behaviors further induce the Jahn–Teller effect for electronic reconfiguration and field split for Mn 3d orbitals. Thus, tandem H2 generation and hydrogenation of levulinate to valerolactone can occur much more efficiently with a fivefold enhancement over monometallic oxide catalysts. Detailed characterization of fresh and sintered catalyst samples further demonstrated the critical role of expansion of the Mn–O facet and phase segregation in facilitated chemical chain reactions. The design principles discussed in this work could be potentially applied for other non-noble oxide catalysts in energy and environmental fields.

Evolution of interfacial formation and configuration control of bicomponent fiber during full spinning process

As a result of the limitation of bicomponent spinning in which it is difficult to obtain the interface evolution of the fiber forming process and guarantee performance stability, numerical simulation was carried out to investigate the effect of cooling, melt viscosity, and inlet flow rate on the interface throughout the process. The results showed that the position deviation of the interface only occurred inside the orifice and the interface distortion continued until after extrusion, with the maximum deformation occurring during extrusion swelling. Based on sufficient multifield data obtained from the simulation, it was demonstrated that the interfacial curvature was governed only by the viscosity difference between individual components, and the position of the interface was determined by the mechanical energy of the bicomponent melt. Moreover, the curvature and the position of the interface can be adjusted indirectly by changing the viscosity ratio, which can be regulated by the flow ratio, bringing guidance for the full process control of the bicomponent fiber preparation.

Moisture-assistant chlorinated separator with dual-protective interface for ultralong-life and high-rate lithium metal batteries

Metallic lithium (Li) is among the most promising anodes due to their high theoretical capacity (3860 mAh g–1) and the lowest redox potentials (−3.04 V vs standard hydrogen electrode). However, the application of lithium metal batteries (LMBs) has encountered by the uncontrollable growth of Li dendrite and unstable solid electrolyte interface (SEI). Therefore, regulating a compositionally favorable and Li+-permeable SEI is crucial for the development of long-life LMBs. Previous studies have revealed the moisture as a detrimental inducement to cell degradation. Beyond current understanding, inorganic LiCl with adsorption of moisture is first applied to protect Li anode, where the hydrated and chlorinated separator has introduced LiF/artificial SEI dual-layer simultaneously with much improved cycle stability and interface compatibility over the non-hydrated counterparts. Meanwhile, the modified separator (with hydrated LiCl/poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) layer) has synergistically achieved the suppression of dendrite growth and interface distortion, restraining the decay of Li deposition/stripping for better cycle stability. Accordingly, the lifespan of modified Li|Li cell is extended to over 2700 h with improved rate capability, reduced overpotentials and high Coulombic efficiency (CE) of 99.5 %. Further, the moisture-assistant chlorinated separator is applied in energy-dense LMBs system, which allows for a stable and shuttle-free Li–S batteries with high sulfur utilization and chemically accelerated conversion kinetics. As a result, the dual-shield protected separator configuration synergistically fulfills high sulfur capacity of 1293.6 mAh g–1 at 0.1 C (1C = 1675 mA g−1), long-term Li–S cycle stability at 1 C and high-rate capability (582.2 mAh g–1 at 5 C). This contribution provides insights of implementing moisture-assistant chlorinated separator for Li anode protection and high-performance Li–S batteries.

A Novel Methodology for Robust Topology Optimization Considering Manufacturing Errors and Topology Deviations

In topology optimization (TO), the finally manufactured topology will inherently deviate from the optimized one due to both curved lines or smoothed surfaces being used in the real-world topology and the manufacture error (ME). Generally, such deviation or tolerance is called an uncertainty in the topology. However, the deviation of the built topology from the optimized one may result in degradation of the performance of the optimized solution for microscale magnetic devices. Therefore, robust optimization (RO) considering ME and topology deviations (TDs) has become a hot concern in TO problems. Consequently, it is demanding to develop feasible and efficient procedures for TOs considering MEs and TDs. In this respect, a novel methodology based on the min-cut theorem and Bezier curve (MCBC) is first proposed. Based on the min-cut-based methodology for deterministic TOs, the Bezier curve is proposed to generate interface distortion realistically. The numerical result on the TO of a magnetic actuator has demonstrated that the proposed methodology has a good ability to obtain optimized topology insensitive to MEs and TDs.

Graphene oxide-induced structural morphology and colloidal interaction at water–oil interface

Adsorption of amphiphilic monolayer graphene oxides (GOs) at oil–water interfaces can modify the interfacial structure and morphology, and in turn, influence their aggregating interactions and packing arrangement. A microscopic understanding of adsorption structures and interaction mechanisms for nanoscale GOs with varied chemical compositions at the interfaces can guide and improve the GO-related material preparation and micro-emulsification processes. Herein, all-atom molecular dynamics simulations were conducted for the structural morphologies and residing organizations of multiple GO nanosheets at the water-cyclohexane interface. The colloidal interaction was simulated as the potential of mean forces (PMF) between GO nanosheets at the interface. For the first time, the interfacial structural morphologies were revealed and correlated with the GO chemical compositions. GO nanosheets with more edge carboxyl groups, lower oxidation degrees, or lower hydroxyl proportion can lead to more uniform or homogeneous GOs packing, corresponding to weaker interface fluctuation or distortion. The PMF-based interactions can be applied to explain the GOs contacting performances at the interface, wherein the interfacial water plays a controlling role in regulating the GO interactions. Our simulation study provides new insights into the GO-induced liquid–liquid interface behavior.

Investigation of Electrical and Thermal Properties of Epoxy Resin/Silicon Carbide Whisker Composites for Electronic Packaging Materials

This article explores the potential of epoxy resin/silicon carbide whisker (EP/SiCw) composites (1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%) as the field-dependent conductivity (FDC) packaging materials for the high-voltage power modules by investigating their thermal and electrical properties at different temperatures. The cross-sectional morphology of the prepared materials is characterized by field emission-scanning electron microscopy (FE-SEM). The thermal analysis consists of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The electrical properties, such as dc conductivity, dielectric spectroscopy, thermally stimulated discharge current (TSDC), space charge distribution, and dc breakdown strength, are measured. The molecular orbital energy levels of the EP and SiCw monomers are calculated by quantum chemical calculation (QCC) to analyze the effect of EP interfacial trap sites on the electrical properties. The effect of the EP/SiCw interfacial charges and electrical field distortion on the electrical properties of the EP/SiCw composites with different filler content is investigated by the finite-element method (FEM) simulation. It is found that the 2 wt% EP/SiCw composite has a better thermal performance. The 1 wt% has lower real permittivity, lower trap density, lower space charge accumulation, and higher breakdown strength. The EP/SiCw composites have a higher trap level than the pure EP. The nonlinearity percolation threshold of the EP/SiCw composites is 3 wt%. As the filler content increases, the nonlinear conductivity coefficient of the EP/SiCw composites becomes higher, whereas the breakdown strength decreases due to the electric field distortion near the electrodes caused by the apparent hetero charge accumulation at high filler content.

A surface modification of KTa0.5Nb0.5O3 by APDS and its enhanced dielectric properties for polyimide nanocomposites

In this work, KTN-NH2/PI nanocomposites with high breakdown strength and low dielectric loss were obtained by modifying the KTa0.5Nb0.5O3 surface with 3-(2-aminoethylamino) propylmethyldimethoxysilane (APDS). Compared with KTN/PI, the loss tangent (tanδ) of KTN-NH2/PI was decreased. The breakdown strength (Eb) could reach to 242.12 kV/mm, which is about 1.49 times higher than that of KTN/PI. Based on the molecular dynamics simulation, the interaction between the modified KTN-NH2 and the PI matrix was higher than the KTN/PI, which would reduce the tanδ by restraining the dipole orientation polarizations. Moreover, the increase of hydrogen bonds improve the interfacial compatibility, which reduce the electric field distortion of organic-inorganic interface and improve Eb.

Micro-engineering based Structuring and Valorization of Lipid Foods

Microengineering-based structuring and valorization of lipid foods were investigated. First, to control the fatty acid composition of triglycerides, modified lipases were prepared using emulsifiers and fatty acids, and applied to interesterification of fats and oils. Stearic acid was suitable for lipase activation, showing high interesterification activity. The structure of stearic acid-modified lipase was first analyzed by small-angle X-ray scattering. Next, the membrane separation performance for crude oil was investigated using hydrophobic non-porous membranes. Degumming and decolorization tests for crude soybean oil were conducted, revealing that the rejection of phospholipids and the decolorization ratio were more than 95%, representing higher quality compared to conventional methods. Membrane application to used edible oil also showed better performance than the conventional adsorption method. For practical use, improvement of the permeate flux is needed. Finally, a technology was developed for preparing monodisperse emulsions using fabricated microchannels (MCs). Efficient emulsification was achieved using asymmetrically structured MCs. The slit structure caused large distortion of the oil-water interface, and the interfacial tension induced spontaneous droplet formation. Laboratory-scale MC emulsification equipment was industrialized and used for various applications.

Large-eddy simulations of flow past a circular cylinder near a free surface

Three-dimensional large-eddy simulations are carried out for flow past a cylinder beneath a deformable free surface at a fixed Reynolds number of Re = 7550. The results are examined for two Froude numbers of Fr=0.2 and 0.6 and a gap ratio of 0.4, to investigate the effects of the distortion of the free surface on the flow fields and hydrodynamics. At the low Froude number of Fr=0.2, the deformation of the free surface is small with little influence on the wake characteristics, and an alternative vortex shedding modulated by the free surface is detected in the wake. As the Froude number increases to 0.6, intense interface distortion occurs, which can be divided into three different regions: a hydraulic jump in the region of overtopping, a well-defined long-wavelength wave generation region in the large-scale recirculation zone near the free surface, and a water level recovery slope further downstream. The sudden change in flow regime from locally supercritical to subcritical allows the occurrence of the hydraulic jump. The induced surface waves behind the cylinder are ascribed to the shedding process of three shear layers, two of which are separated from the cylinder surface and one from the free surface. In addition, a jet-like flow originated from the gap between the free surface and the top of the cylinder occurs, exerting a downward thrust on the cylinder and pushing the wake away from the free surface. The Kármán vortex shedding in the wake is suppressed due to the interruption of the jet-like flow. The fluctuations of the wake turbulence and hydrodynamic forces are also suppressed to a low level.

The Microstructure of Fe-Based Laminated Metal Composite Produced by Powder Metallurgy.

Powder metallurgy (PM) is a versatile process to manufacture nearly net-shaped metallic materials in industry. In this study, the PM process was used to fabricate two Fe-based laminated metal composites (LMCs), Fe-4Ni-3Cr-0.5Mo-0.5C/Fe and 410/304L. The results showed that after sintering, the LMCs were free of interfacial cracks and distortion, indicating that the PM process is a feasible means for producing these LMCs. In the Fe-4Ni-3Cr-0.5Mo-0.5C/Fe LMC, the diffusion of C resulted in the generation of a continuous pearlite layer between the Fe-4Ni-3Cr-0.5Mo-0.5C and Fe layers and a ferrite/pearlite mixture in the Fe layer. In the 410/304L LMC, the difference in the chemical potentials of C between the 304L and 410 layers led to the uphill diffusion of C from the 410 layer to the 304L layer. A continuous ferrite layer was thus formed near the interface of the 410 layer. Furthermore, a martensite layer of about 50 μm thickness was generated at the interface due to the high Cr and Ni content.

Reverse Time Migration Based on the Pseudo-Space-Domain First-Order Velocity-Stress Acoustic Wave Equation

Reverse time migration (RTM) is an ideal seismic imaging method for complex structures. However, in conventional RTM based on rectangular mesh discretization, the medium interfaces are usually distorted. Besides, reflected waves generated by the two-way wave equation can cause artifacts during imaging. To overcome these problems, a high-order finite-difference (FD) scheme and stability condition for the pseudo-space-domain first-order velocity-stress acoustic wave equation were derived, and based on the staggered-grid FD scheme, the RTM of the pseudo-space-domain acoustic wave equation was implemented. Model experiments showed that the proposed RTM of the pseudo-space-domain acoustic wave equation could systematically avoid the interface distortion problem when the velocity interfaces were considered to compute the pseudo-space-domain intervals. Moreover, this method could effectively suppress the false scattering of dipping interfaces and reflections during wavefield extrapolation, thereby reducing migration artifacts on the profile and significantly improving the quality of migration imaging.

Enhancing the macroscopic polarization of CdS for piezo-photocatalytic water splitting

Piezo-photocatalytic hydrogen production from water splitting is emerging as a promising way to generate renewable energy, but is challenged by low efficiency and ambiguous understanding of mechanisms. Herein, the CdS phase junction (H/C-CdS) with interfacial structural distortion is applied for prominent piezo-photocatalytic H2 evolution for the first time. Density functional theory (DFT) and second harmonic generation (SHG) demonstrate that the superior macroscopic polarity in H/C-CdS originates from the distortion of CdS4 tetrahedron units at the interface between hexagonal CdS (H-CdS) and cubic CdS (C-CdS). The obvious enhanced macroscopic polarity of H/C-CdS largely boosts the separation of photogenerated electrons and holes with the elimination of the electrostatic screening produced in CdS phase junction. An encouraging piezo-photocatalytic H2 evolution rate of 3.19 mmol·g−1·h−1 is delivered by H/C-CdS in pure water in the absence of any co-catalyst, which is 1.4 and 5.3 times higher than those of H-CdS (2.31 mmol·g−1·h−1) and C-CdS (0.59 mmol·g−1·h−1), respectively. Additionally, the value-added oxidation product H2O2 is produced in piezo-photocatalysis. This work firstly discloses macroscopic polarization enhancement induced by phase junction system on improvement of piezo-photocatalytic H2 evolution of CdS.

Effect of Rapid Cold Stamping on the Evolution of Long Strip-Shaped Nanoprecipitation in Al-Cu-Mg Alloy.

High-resolution transmission electron microscopy (HRTEM), X-ray diffractometry (XRD), energy dispersive spectroscopy (EDS), and hardness testing are used to investigate the evolution of the long strip-shaped S' phase of spray-formed fine-grained Al-Cu-Mg alloy during rapid cold stamping deformation. The elongated S' phase of the extruded Al-Cu-Mg alloy is subjected to twisting, brittle fracturing, redissolution, and necking during rapid cold stamping deformation. As a result, the morphology, size, distribution, and orientation relationship with the matrix of the long strip-shaped S' phase changed significantly. The regularly distributed long strip-shaped nanoscale precipitates evolved into irregularly distributed short rod-shaped S' phases and diffusely distributed granular reprecipitates. The twist and brittle fracture of the long strip-shaped S' phase significantly increased the contact surface between the precipitated phase and the aluminum matrix, improved the interfacial distortion energy of the precipitated phase and the aluminum matrix, and promoted the redissolution of the S' phase. The supersaturation state is reached, thus resulting in reprecipitation, which then lowered the matrix free energy. The hardness of the extruded Al-Cu-Mg alloy increased from 54.2 HB to 128.1 HB during the rapid cold stamping process.

Fully coupled electrothermal and mechanical simulation of the production of complex shapes by spark plasma sintering

The obtention of an accurate mechanical model of the spark plasma sintering (SPS) requires the identification of creep parameters. Those parameters are usually determined experimentally, which involves several tests and could be a source of error for the model predictions. A numerical identification, based on only one SPS experiment per material, allowed the determination of the creep parameters of Al2O3 and TiAl samples. The resulting mechanical model was then coupled with an electro-thermal model of the system to obtain a fully coupled simulation of the SPS. This model can predict the densification behavior not only of simple pellets, but also of complex shape configurations. It accurately predicts the density gradients inside the complex sintered parts as well as the interface distortion during sintering. Thus, numerical simulation can be used as an efficient predictive tool to obtain fully dense objects with the desired geometry.

A mechanism for the amplification of interface distortions on liquid jets

Abstract

Capillary force on an 'inert' colloid: a physical analogy to dielectrophoresis.

“Inert” colloids are μm-scale particles that create no distortion when trapped at a planar fluid–fluid interface. When placed in a curved interface, however, such colloids can create interfacial distortions of quadrupolar symmetry – so-called “induced capillary quadrupoles.” The present work explores the analogy between capillary quadrupoles and electric dipoles, and the forces exerted on them by a symmetry-breaking gradient. In doing so, we weigh in on an outstanding debate as to whether a curvature gradient can induce a capillary force on an inert colloid. We argue that this force exists, for the opposite would imply that all dielectrophoretic forces vanish in two dimensions (2D). We justify our claim by solving 2D Laplace problems of electrostatics and capillary statics involving a single particle placed within a large circular shell with an imposed gradient. We show that the static boundary condition on the outer shell must be considered when applying the principle of virtual work to compute the force on the particle, as verified by a direct calculation of this force through integration of the particle stresses. Our investigation highlights some of the subtleties that emerge in virtual work calculations of capillary statics and electrostatics, thereby clarifying and extending previous results in the field. The broader implication of our results is that inert particles – including particles with planar, pinned contact lines and equilibrium contact angles – interact through interparticle capillary forces that scale quadratically with the deviatoric curvature of the host interface, contrary to recent claims made in the literature.

TiO2 surface oxygen vacancy passivation towards mitigated interfacial lattice distortion and efficient perovskite solar cell

It is known that there exist inherent oxygen vacancies which is reported to be negative to PSCs performance on the TiO2 film surface where contacts the gaseous phase while the manufacturing process. In this work, we clarified the role of surface oxygen vacancy on TiO2/perovskite interface structure, which would not only serve as trap states to capture generated electrons, but also cause perovskite crystal distortion and PbI bond broken due to the interfacial interaction, generating additional interfacial defects. In addition, by analyzing the interfacial carrier transport routes, the common reason behind the different carrier loss pathways was ascertained to be the oxygen vacancy. Hence, for reducing oxygen vacancies and its negative impact on the device performance, the surface passivation method with gaseous fluorine was proposed, both the DFT (density functional theory) calculation results and experimental approaches proved that the surface passivation method could effectively reduce the traps states, mitigate interface structure distortion and enhance the interfacial charge transfer. As a consequence, MAPbI3-based PSCs with surface passivation obtained a champion PCE of 20.43%, 7.7% higher than that (18.98%) of control device, and FA0.15MA0.85PbI3-based PSCs with surface passivation obtained a champion PCE of 21.16%, 6.2% higher than that (19.92%) of control device.

Rayleigh-Taylor instability in a spherical configuration: A viscous potential flow approach

In this paper, Rayleigh-Taylor (RT) instability at the spherical interface is analyzed through the potential flow theory of viscous fluids. The linear stability theory is utilized including normal mode procedure. The viscous, incompressible fluids are confined in the spherical shell and the interface distortion is expressed in terms of spherical harmonic functions. We achieve a quadratic equation for the illustration of instability/stability criterion. We also compute the highest growth of perturbations and corresponding mode. The Plane configuration results are recovered when the mode of perturbations is very large. Viscosity is found to stabilize the interface while the Weber number and Reynolds number have destabilizing nature.