Interface Response Research Articles

Ultra-Low Loading Fillers Induced Excellent Capacitive Performance in Polymer-Based Multilayer Nanocomposites under Harsh Environments.

Multilayer-structured nanocomposites are recognized as a prominent strategy for overcoming the paradox between the breakdown strength (Eb) and polarization (P) to achieve superior energy storage performance. However, current multilayer-structured nanocomposites involving substantial quantities of nanofillers (>10vol.%) for high dielectric constant as polarization layer will inevitably deteriorate mechanical properties and breakdown strength. Herein, an innovative approach is reported to breaking conventional rules by designing a multilayered polymer composite with ultralow loading of Al2O3 nanoparticles, i.e., 0.3vol.% for polarization layers and 2vol.% for insulation layers. By modulating the spatial distribution of Al2O3 nanoparticles in polymer, a significantly increased interfacial dipole response is induced, and deep interfacial traps are constructed to capture the mobile charges, thereby suppressing high-temperature conduction loss. The resulting multilayered polymer composite exhibits an unparalleled discharged energy density of 7.8 Jcm-3 with a charging/discharging efficiency exceeding 90% at 150°C. This work provides valuable insights into achieving superior capacitive performance in multilayer composite films operating under extreme conditions.

Interfacial microstructure evolution and mechanical response of TC19/Ti150 dissimilar joints obtained by diffusion bonding

The structure made by dissimilar titanium alloys can meet the differentiated requirements of performance for different parts, fully exerting their performance advantages during operation respectively, which holds significant technological and economic value. Here, we used diffusion bonding (DB) method to connect TC19 and Ti150 dissimilar titanium alloys in the temperature range of 810 °C–900 °C, and investigated the morphology, forming mechanism, deformation behavior and mechanical properties of the joints. The study showed that the interfacial voids disappeared with the increase of temperature, and the interfacial characteristics gradually evolved from the initial straight shape to a curved shape. The original bond line transformed into βTC19/αTi150 phase boundaries (PBs) and high-angle grain boundaries (HAGBs) formed by αTC19 and αTi150. No harmful intermetallic compounds were formed on the interface. The joint formation can be considered as a combination of three behaviors: plastic deformation, elemental diffusion and interfacial grain boundary migration (IGBM). In addition, it was observed that dislocation slip was the main deformation behavior of the joints. The dislocations generated in the both matrices were obviously accumulated at the interface during tensile deformation of the specimen, and the bonding interface hindered the dislocation transfer between two substrates. The room temperature uniaxial tensile results exhibited that the joints bonded at 810 °C and 840 °C were broken at the interface, showing poor mechanical properties caused by holes and straight interface. And yet the joints bonded at 870 °C and 900 °C occurred fracture on the Ti150 matrix. The strength of joints was comparable to that of the Ti150 matrix, indicating that the two dissimilar titanium alloys achieved a reliable bonding. This work provides valuable inspiration for the diffusion bonding process of titanium alloys with different microstructures.

Transient Chemo-Mechanical Model of Lithium Plating Impacted by External Pressure

To meet the ever-growing need for high capacity, fast-charge batteries, lithium anodes have been considered a direct upgrade to previous commercial anode materials thanks to their high gravimetric density and low coulombic efficiency. However, their implementation into crucial applications such as electric vehicles has been hindered by safety issues during and at the end of their operational lifetime. Over hundreds of cycles, nonhomogeneous plating and stripping of lithium on the anode surface encourages the growth of dendrites, which eventually lead to capacity loss, cell failure, and fire. The application of stack pressure has been found to mitigate dendrite growth to an extent; however, the impacts of long-term pressure application on lithium deposition, and subsequent lithium plastic deformation and creep, are not well understood. In this work, we present a novel method for accurately modeling the interplay between mechanical deformation and electrochemical deposition. We develop a 3D, finite-element, transient model of lithium plating and stripping at the mesoscale. A stack pressure is applied to a lithium anode in contact with a polymer separator, and the electrochemical response to an applied current density is evaluated. The lithium protrusion is then reshaped to model incremental plating or stripping, thus simulating the cumulative interfacial movement over a full charge-discharge cycle. Mechanical complexities of the materials, such as lithium plastic deformation and separator porosity, are accounted for. The interfacial response is studied with respect to applied stack pressure and assumed lithium yield strength. Through this work, the impacts of stack pressure on dendrite growth at the microscale are explored. The lithium yield strength assumption is found to be crucial for accurately predicting deposition behavior.Supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.

Interfacial Structures and Mechanical Response of Highly Viscous Polymer Melt on Solid Surfaces Investigated by Atomic Force Microscopy

Interfacial Structures and Mechanical Response of Highly Viscous Polymer Melt on Solid Surfaces Investigated by Atomic Force Microscopy

Electric-field activating on-surface tailored (OST) coarse polyester fibers for efficient airborne particle removal: Interfacial morphologies and electrical response

Fibrous filtration is the most-used method for indoor particulate matter (PM) removal. The filtration performances are governed by filters’ intrinsic geometries, displaying the tradeoff among efficiency, resistance, and lifespan. In this contribution, we provided a chemically-synthesized strategy to improve the performance of coarse filters while preserving their ultralow initial resistances. After elucidating PM-fiber interactions, the fibrous interfacial nano-morphologies were tailored by different dielectric coatings based on commercially-available substrates. Activated by fiber polarizing, the tuned morphologies with ∼100 nm surface roughness and enhanced electrostatic potential are considered the drivers of boosted filtration efficiency. In practice, a 10-mm-thick polydopamine (PDA)-MnOx coated polyester filter possessed an improved efficiency of 97.7 % for 300–500 nm particles, and the ultralow resistance of 11.2 Pa at 0.5 m/s filtration velocity. The strong surface adhesion facilitated long-term efficiency of 95.6 % in a continuous 25-day period without any decay. The nanoscale coatings, which were just one-thousandth in thickness of the fiber gaps, enabled more than 50-fold improvement of the filters’ quality factor. We further established dimensionless factors to evaluate the cost-performance effect. We expect the strategy and techniques can pave the way to better understand electrostatic air filtration, being competitive candidates in the air filtration community.

Thermally Conductive Elastomer Composites with High Toughness, Softness, and Resilience Enabled by Regulating Interfacial Structure and Dynamics.

The emerging applications of thermally conductive elastomer composites in modern electronic devices for heat dissipation require them to maintain both high toughness and resilience under thermomechanical stresses. However, such a combination of thermal conductivity and desired mechanical characteristics is extremely challenging to achieve in elastomer composites. Here this long-standing mismatch is resolved via regulating interfacial structure and dynamics response. This regulation is realized both by tuning the molecular weight of the dangling chains in the polymer networks and by silane grafting of the fillers, thereby creating a broad dynamic-gradient interfacial region comprising of entanglements. These entanglements can provide the slipping topological constraint that allows for tension equalization between and along the chains, while also tightening into rigid knots to prevent chain disentanglement upon stretching. Combined with ultrahigh loading of aluminum-fillers (90 wt%), this design provides a low Young's modulus (350.0kPa), high fracture toughness (831.5 J m-2), excellent resilience (79%) and enhanced thermal conductivity (3.20 W m-1 k-1). This work presents a generalizable preparation strategy toward engineering soft, tough, and resilient high-filled elastomer composites, suitable for complex environments, such as automotive electronics, and wearable devices.

Investigating the interfacial and bulk rheological properties of emulsions containing dry bean powder

This study aimed to investigate the impact of varying proportions of dry bean powder on the rheological properties of oil-in-water emulsions. Emulsions were formulated utilizing xanthan gum or dry bean powder across a range of concentrations, including 1%, 3%, 5%, and 7%. Additionally, a control emulsion (CTR) was formulated using xanthan gum exclusively. The rheological properties of the resulting emulsions, both linear and nonlinear, were characterized. Moreover, the correlation between microstructural attributes and the interfacial rheological response within these emulsion systems was thoroughly examined. A prominent observation was the occurrence of shear thinning, characterized by a reduction in viscosity under applied shear stress. Notably, the control emulsion (CTR) displayed the lowest interfacial viscosity values, whereas emulsions incorporating increasing proportions of dry bean powder demonstrated a proportional rise in interfacial viscosity. The highest consistency coefficient and apparent viscosity was recorded in the 7%DB sample with a value of 3.23 Pa.sn and 0.56 Pa.s, respectively. This suggests that emulsions formulated with dry bean powder may yield a more resilient interfacial film, attributed to the protein content inherent in dry beans. The establishment of a viscoelastic interfacial layer facilitated by dry bean powder in appropriate concentrations significantly contributes to the long-term stability of the emulsion. Unraveling the intricate relationship between interfacial behaviors holds paramount importance in advocating for the utilization of dry bean powder as a plant-based protein source. In conclusion, the incorporation of dry bean powder enhances the formation of interfacial films in O/W emulsions.

Characterizing Liquid Water in Deep Martian Aquifers: A Seismo‐Electric Approach

AbstractDeep Martian aquifers harboring liquid water could hold vital insights for current and past habitability. We show that with seismo‐electric interface responses (IRs) we can quantitatively characterize subsurface water on Mars. Full‐waveform simulations and sensitivity analyses across diverse Martian aquifer scenarios demonstrate the technique's effectiveness. In contrast to how seismo‐electric signals often appear on Earth, Mars' desiccated surface naturally removes co‐seismic fields and exposes useful IRs that allow us to characterize several aquifer properties. Changing the aquifer depth, thickness, or quantity changes the IR arrival times or shape: aquifer depth is a strong control on evanescent IRs, thickness affects the relative timing of IRs, and increasing the number of aquifers introduces more dipole sources to the waveform. Other factors, such as aquifer saturation, chemistry, and salinity, strongly affect IR amplitude but have minimal or no effect on waveform shape. Notably, for a deep low‐porosity aquifer, the salinity and brine chemistry (perchlorate vs. chloride) are the strongest controls on signal amplitude. Analyzing the effects of epicentral distance shows that radiating and evanescent IRs separate at large source‐receiver offset, allowing analyses of both signals and accurate event distance derivation. From this numerical investigation of the sensitivity of IRs to deep Martian aquifers, we anticipate future analyses of electromagnetic data from the InSight lander or future missions to Mars and other planets.

On the interfacial behavior of two-dimensional decagonal quasicrystal films with an adhesive layer due to thermal misfit

The interfacial behavior of a thin two-dimensional decagonal quasicrystal (QC) film bonded to a half plane with an adhesive layer is analyzed under thermal misfit. Under a perfect non-slipping contact condition at interface, a theoretical model is established based on the membrane assumption, with the governing integral–differential equations being constructed in terms of phonon interfacial shear stresses in one single and multiple films. Then, these governing equations are numerically solved by Chebyshev polynomials, obtaining the phonon interfacial shear and internal normal stresses as well as the longitudinal displacement in the QC film. Finally, the effects of neighboring films, material mismatch, adhesive layer, the geometry of QC film, and temperature variation are briefly discussed on the interfacial response. It is found that the adhesive layer plays as a softening medium which can greatly reduce the value of normal and shear stresses and weaken the singularity of shear stresses near the ends of films. These findings will be instructive to the accurate measurement and safety monitoring of QC films.

Fe-Doped Ni2P/NiSe2 Composite Catalysts for Urea Oxidation Reaction (UOR) for Energy-Saving Hydrogen Production by UOR-Assisted Water Splitting.

The development of efficient urea oxidation reaction (UOR) catalysts helps UOR replace the oxygen evolution reaction (OER) in hydrogen production from water electrolysis. Here, we prepared Fe-doped Ni2P/NiSe2 composite catalyst (Fe-Ni2P/NiSe2-12) by using phosphating-selenizating and acid etching to increase the intrinsic activity and active areas. Spectral characterization and theoretical calculations demonstrated that electrons flowed through the Ni-P-Fe-interface-Ni-Se-Fe, thus conferring high UOR activity to Fe-Ni2P/NiSe2-12, which only needed 1.39 V vs RHE to produce the current density of 100 mA cm-2. Remarkably, this potential was 164 mV lower than that required for the OER under the same conditions. Furthermore, EIS demonstrated that UOR driven by the Fe-Ni2P/NiSe2-12 exhibited faster interfacial reactions, charge transfer, and current response compared to OER. Consequently, the Fe-Ni2P/NiSe2-12 catalyst can effectively prevent competition with OER and NSOR, making it suitable for efficient hydrogen production in UOR-assisted water electrolysis. Notably, when water electrolysis is operated at a current density of 40 mA cm-2, this UOR-assisted system can achieve a decrease of 140 mV in the potential compared to traditional water electrolysis. This study presents a novel strategy for UOR-assisted water splitting for energy-saving hydrogen production.

Experimental study on progressive interfacial mechanical behaviors using fiber optic sensing cable in frozen soil

Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction. Optical frequency domain reflectometry (OFDR) based on Rayleigh scattering can be applied to monitor ground deformation in frozen soil areas, where the interface behavior of soil-embedded fiber optic sensors governs the monitoring accuracy. In this paper, a series of pullout tests were conducted on fiber optic (FO) cables embedded in the frozen soil to investigate the cable‒soil interface behavior. An experimental study was performed on interaction effects, particularly focused on the water content of unfrozen soil, freezing duration, and differential distribution of water content in frozen soil. The high-resolution axial strains of FO cables were obtained using a sensing interrogator, and were used to calculate the interface shear stress. The interfacial mechanical response was analytically modeled using the ideal elasto‒plastic and softening constitutive models. Three freezing periods, correlating with the phase change process between ice and water, were analyzed. The results shows that the freezing effect can amplify the peak shear stress at the cable-soil interface by eight times. A criterion for the interface coupling states was proposed by normalizing the pullout force‒displacement information. Additionally, the applicability of existing theoretical models was discussed by comparing the results of theoretical back‒calculations with experimental measurements. This study provides new insights into the progressive interfacial failure behavior between strain sensing cable and frozen soil, which can be used to assist the interpretation of FO monitoring results of frozen soil deformation.

Water molecules mute the dependence of the double-layer potential profile on ionic strength.

We present the results of molecular dynamics simulations of a nanoscale electrochemical cell. The simulations include an aqueous electrolyte solution with varying ionic strength (i.e., concentrations ranging from 0-4 M) between a pair of metallic electrodes held at constant potential difference. We analyze these simulations by computing the electrostatic potential profile of the electric double-layer region and find it to be nearly independent of ionic concentration, in stark contrast to the predictions of standard continuum-based theories. We attribute this lack of concentration dependence to the molecular influences of water molecules at the electrode-solution interface. These influences include the molecular manifestation of water's dielectric response, which tends to drown out the comparatively weak screening requirement of the ions. To support our analysis, we decompose water's interfacial response into three primary contributions: molecular layering, intrinsic (zero-field) orientational polarization, and the dipolar dielectric response.

A Micromechanical Study of Interactions of Cyanate Ester Monomer with Graphene or Boron Nitride Monolayer.

Polymer composites, hailed for their ultra-strength and lightweight attributes, stand out as promising materials for the upcoming era of space vehicles. The selection of the polymer matrix plays a pivotal role in material design, given its significant impact on bulk-level properties through the reinforcement/polymer interface. To aid in the systematic design of such composite systems, molecular-level calculations are employed to establish the relationship between interfacial characteristics and mechanical response, specifically stiffness. This study focuses on the interaction of fluorinated and non-fluorinated cyanate ester monomers with graphene or a BN monolayer, representing non-polymerized ester composites. Utilizing micromechanics and the density functional theory method to analyze interaction energy, charge density, and stiffness, our findings reveal that the fluorinated cyanate-ester monomer demonstrates lower interaction energy, reduced pull-apart force, and a higher separation point compared to the non-fluorinated counterpart. This behavior is attributed to the steric hindrance caused by fluorine atoms. Furthermore, the BN monolayer exhibits enhanced transverse stiffness due to increased interfacial strength, stemming from the polar nature of B-N bonds on the surface, as opposed to the C-C bonds of graphene. These molecular-level results are intended to inform the design of next-generation composites incorporating cyanate esters, specifically for structural applications.

Reducing the prosthesis modulus by inclusion of an open space lattice improves osteogenic response in a sheep model of extraarticular defect.

Introduction: Stress shielding is a common complication following endoprosthetic reconstruction surgery. The resulting periprosthetic osteopenia often manifests as catastrophic fractures and can significantly limit future treatment options. It has been long known that bone plates with lower elastic moduli are key to reducing the risk of stress shielding in orthopedics. Inclusion of open space lattices in metal endoprostheses is believed to reduce the prosthesis modulus potentially improving stress shielding. However, no in vivo data is currently available to support this assumption in long bone reconstruction. This manuscript aims to address this hypothesis using a sheep model of extraarticular bone defect. Methods: Initially, CT was used to create a virtual resection plan of the distal femoral metaphyses and to custom design endoprostheses specific to each femur. The endoprostheses comprised additively manufactured Ti6Al4V-ELI modules that either had a solid core with a modulus of ∼120GPa (solid implant group) or an open space lattice core with unit cells that had a modulus of 3-6GPa (lattice implant group). Osteotomies were performed using computer-assisted navigation followed by implantations. The periprosthetic, interfacial and interstitial regions of interest were evaluated by a combination of micro-CT, back-scattered scanning electron microscopy (BSEM), as well as epifluorescence and brightfield microscopy. Results: In the periprosthetic region, mean pixel intensity (a proxy for tissue mineral density in BSEM) in the caudal cortex was found to be higher in the lattice implant group. This was complemented by BSEM derived porosity being lower in the lattice implant group in both caudal and cranial cortices. In the interfacial and interstitial regions, most pronounced differences were observed in the axial interfacial perimeter where the solid implant group had greater bone coverage. In contrast, the lattice group had a greater coverage in the cranial interfacial region. Conclusion: Our findings suggest that reducing the prosthesis modulus by inclusion of an open-space lattice in its design has a positive effect on bone material and morphological parameters particularly within the periprosthetic regions. Improved mechanics appears to also have a measurable effect on the interfacial osteogenic response and osteointegration.

Modeling the progressive damage of cryogenic microdroplet tests using a temperature‐friction cohesive zone model

AbstractThe fiber/resin interfacial mechanical properties in low‐temperature environments are crucial for composite materials, and a temperature‐friction cohesive zone model is proposed in this paper. This model combines the temperature effect, the interfacial friction effect, and the interfacial debonding. The mechanical characteristics of the fiber/matrix interface are described using this model. The proposed model has been implemented in ABAQUS using the VUMAT subroutine. To verify this model, microdroplet debonding experiments were conducted at temperatures 298, 193, and 77 K. The results of the simulation and the experiment matched well. The proposed model takes temperature differences as a parameter and can characterize the interfacial mechanical response at different temperatures. In addition, the temperature, friction, interface parameters, and microdroplet size effects on the mechanical properties of the fiber/matrix interface were investigated. The results show that interfacial friction and temperature differences have a significant impact on the interfacial mechanical properties. The microdroplet size also has an influence on interfacial shear strength.Highlights A temperature‐friction cohesive zone model is proposed. Cryogenic microdroplet debonding tests were conducted. The finite element method results are stable and close to the regression line of tests. The temperature difference changes the stress state of the interface. The interfacial sliding friction force has a large dispersion.

The doped Pd on the crystal calculation and intermetallic property of low-temperature soldered ENEPIG substrates

The preparation of new solder joint materials for chip packaging by designing a variety of brazing material mixes has become one of the future research directions for solder joints. They added low melting point elements to traditional solder materials to prepare low-temperature hybrid solder to meet the low-temperature packaging trend. To improve the performance of low-temperature solder, adding some alloying elements can refine the grain, change the IMC morphology and size, and improve the joint strength to a certain extent. The design of the hybrid solder joint system needs to be based on different metal pads. There are various failure modes of interconnected solder joints on different metal pads. Therefore, the interfacial response, microstructure, and mechanical properties between different hybrid solder and different metal pads need to be studied to optimize the design of the hybrid solder joint system. This paper investigated hybrid low-temperature Sn–3Ag-0.5Cu/Sn–58Bi solder joints on Au/Ni/Cu (ENIG) and Au/Pd/Ni/Cu (ENEPIG) substrates. The addition of Pd elements can change the IMC morphology of hybrid solder joints and affect the fracture failure mode of the joints under shear, with a higher average shear strength at different process parameters than ENIG welded joints. Finally, the presence form of Pd elements in the solder joints was observed under TEM and the fracture mechanism was analyzed. The results showed that Pd atoms on ENEPIG pads can replace some Cu atoms to form (Cu, Pd)6Sn5 intermetallic compounds, distorting the lattice stripe to produce distortions. And compared to ENIG pads, the IMC morphology is pin-rod-like and finer, with more complex grain boundary paths between the grains of the hybrid solder.

Seismoelectric response of 2-D elastic/poroelastic coupled media: a phenomenological approach

SUMMARY In this paper, we address the study of the seismoelectric response of an elastic medium in contact with a poroelastic half-space. In particular, we advance in the understanding of the generation mechanism of the interface response (IR) and the evanescent electromagnetic (EM) fields occurring at the contact between both media, by proposing a seismoelectric phenomenological model (SPM). Essentially, the model consists of a sequence of electric dipoles that are activated successively, simulating the seismic-to-EM energy conversion taking place with the arrival of a seismic wave at the interface separating the media. We obtained SPM responses for different scenarios and acquisition configurations and compared them with responses computed using a code based on the finite-elements method, which solves the seismoelectric equations in the compressional P and vertical shear SV waves coupled with the transverse-magnetic (TM) fields (PSVTM) mode. The SPM successfully represents not only the evanescent wave but also the IR within the elastic medium. In particular, we show that the SPM is able to faithfully reproduce the relative amplitudes of both events and their radiation patterns with a minimum computational cost. In this way, it provides a novel insight in the study of the physical phenomenon behind the seismoelectric conversions.

Simulative and experimental study of metal/polymer interfacial dynamic shear response

Simulative and experimental study of metal/polymer interfacial dynamic shear response

Measurement Geometry and Hydrostatic Pressure‐Dependent Magnetoresistance in All‐Oxide‐Based Synthetic Antiferromagnets

AbstractThe electronic structure of constituent layers and the spin channel of propagating electrons are critical factors that affect the magnitude and sign of magnetoresistance (MR) in synthetic antiferromagnets (SAFMs), which are important for spintronic applications. However, for all‐oxide‐based SAFMs, where there is strong coupling between multiple degrees of freedom, spin transport becomes more complex and remains elusive. Here, using ultrathin half‐metallic manganite/doped ruthenate SAFMs as a model system, three sign reversals of MR are demonstrated accompanied by the crossover between underlying spin‐dependent transport mechanisms. Electron tunneling produces normal MR in the current‐perpendicular‐to‐plane (CPP) geometry at low temperatures, whereas carrier confinement causes inverse MR in the current‐in‐plane (CIP) geometry. Strikingly, CPP MR can undergo a temperature‐driven sign reversal due to resonant tunneling via localized states in the spacer. Moreover, hydrostatic pressure can modulate the interlayer exchange coupling and induce an asymmetric interfacial response to dramatically facilitate electron tunneling, driving a controllable sign reversal of CIP MR. These results provide new insights into understanding and optimization of MR in all‐oxide‐based SAFMs.

Evaluating the adhesion response of acrylonitrile-butadiene-styrene (ABS)/thermoplastic polyurethane (TPU) fused interface using multiscale simulation and experiments

This paper implements reactive forcefield molecular dynamics (MD) simulation to evaluate the mechanical performance of the fusion bond line formed between acrylonitrile butadiene styrene (ABS), and thermoplastic polyurethane (TPU). The simulated interfacial adhesion responses, as obtained from MD simulation, are further implemented as the interfacial properties between ABS and TPU in an upscaled cohesive zone-based finite element analysis (FEA) model for macroscopic response evaluation. Such upscaling enables fair comparison of the simulated macroscopic stress–strain response with experimental results obtained for 3D printed ABS/TPU hybrid samples with a fusion-bonded interface. Overall, the stress–strain response predicted from a FEA-based model shows a good correlation with the experimental data signifying good predictive efficacy of the simulation approach. Thus, by interactively linking the molecular structures of the polymers and the processing parameters with the macroscale interfacial adhesion response of the fusion bond line, the experimentally validated comprehensive approach presented in this paper paves the way for atomistic engineering of the molecular structures as well as efficient fine tuning of processing parameters to meet desired macro-scale performance needs besides enabling exploration of the mechanisms and atomistic origins of the interfacial damage at the fused bond line.