Interfacial Conductance Research Articles

In-situ grown CNTs decorated SiCNWs for enhancing electromagnetic wave absorption efficiency

The uniform growth of carbon nanotube (CNT)-decorated SiC nanowires (SiCNWs) to form a three-dimensional (3D) network can significantly enhance the interfacial polarization effect, making it a promising electromagnetic (EM) wave-absorbing material. Nevertheless, the dispersion of CNT-decorated SiCNWs is challenging. In this study, CNT/SiCNWs composites are successfully synthesized by the in situ growth of CNTs at different annealing temperatures under a N2 atmosphere. Specifically, the CNT-decorated SiCNWs form a 3D network by vapor-liquid-solid (VLS) mechanism. The relative complex permittivity of the CNT/SiCNWs composites notably increases with increasing in temperature, adjusting the microstructure and dielectric properties. When the annealing temperature is 900 °C, the minimum reflection coefficient (RCmin) of the CNT/SiCNWs composites decreases from -34.7 to -44 dB with the thickness of the composites increasing from 3.5 to 3.9 mm. The effective absorption bandwidth (EAB) includes 4.2 GHz in the X band of 8.2–12.4 GHz. The results indicate that the CNT/SiCNWs composites exhibit superior EM wave absorption, which is facilitated by the interfacial polarization, dipole polarization, and conduction loss. The 3D network offers multilayer channels for multiple reflections and the scattering energy of the EM waves. Therefore, the CNT/SiCNWs composites are promising high-efficiency microwave-absorbing materials.

Thermal behavior of the ZrB2 skeleton infiltrated with Cu and CuCrZr alloy

This paper presents the thermal behavior of ZrB2 skeletal material (38% porosity) infiltrated with pure Cu or CuCrZr alloy. Gas-assisted pressure infiltration technology was used to prepare the composites. Thermal diffusivity, density and specific heat measurements were used to calculate the thermal conductivity—the room temperature values of the Cu-ZrB2 and the CuCrZr-ZrB2 material were 157 W m−1 K−1 and 146 W m−1 K−1, respectively, and they decreased with increasing temperature. Analysis of the results showed significant influence of the interface on the thermal conductivity of the CuCrZr-ZrB2 composite. The results indicate that the improved interfacial conductivity was formed due to the presence of the Zr in both the copper alloy and the ceramic skeleton. During infiltration, Zr atoms diffused from the liquid metal to the interface between the metal and the matrix. Here, they created a layer that had metal-related properties. The layer improved wettability of the interface and at the same time the thermal conductivity of the whole composite. The values were compared with the data of the Cu–graphite composite made by the powder metallurgical route where heat transfer through the interface approaches zero. Obtained experimental data were analyzed using the Differential Effective Media (DEM) technique, showing high thermal conductance of the interface between the CuCrZr metal matrix and ceramic skeleton.

Novel Au nanoparticles-inlaid titanium paper for PEM water electrolysis with enhanced interfacial electrical conductivity

Novel Au nanoparticles-inlaid titanium paper for PEM water electrolysis with enhanced interfacial electrical conductivity

Electrolyte-free graphite electrode with enhanced interfacial conduction using Li+-conductive binder for high-performance all-solid-state batteries

Electrodes supported by conductive binders are expected to outperform ones with inert binders that potentially disturb electronic/ionic contacts at interfaces. Unlike electron-conductive binders, the employment of Li+-conductive binders has attracted relatively little attention due to the liquid electrolyte (LE)-impregnated electrode configuration in the conventional lithium-ion batteries (LIBs). Herein, an all-solid-state electrolyte-free electrode where electrolyte components are completely excluded is introduced as a new tactical electrode construction to evaluate the effectiveness of the Li+-conductive binder on enhancing the interfacial conduction, ultimately leading to high-performance all-solid-state batteries (ASSBs). Conductive lithium carboxymethyl cellulose (Li-CMC) is prepared through an optimized two-step cation-exchange reaction without physical degradation. The electrolyte-free graphite electrode employing Li-CMC as the binder shows strikingly improved areal and volumetric capacity of 1.46 mAh cm−2 and 490 mAh cm−3 at a high current rate (1.91 mA cm−2) and 60 °C which are far superior to those (1.07 mAh cm−2 and 356.7 mAh cm−3) using Na-CMC. Moreover, systematic monitoring of the lithiation dynamics inside the electrolyte-free electrode clarifies that the interfacial Li+ conduction is greatly promoted in the Li-CMC electrode. Complementary analysis from in-depth electrochemical measurements and multiscale simulations verifies that serious internal resistance from impeded interparticle diffusion by inert binders can be substantially mitigated using Li-CMC.

Thermal and mass transfer resistance at a liquid-gas interface of an evaporating droplet: A molecular dynamics study

Thermal and mass transfer resistance at a liquid-gas interface could strongly affect the evaporation of a micro/nanodroplet. One of the challenges in the investigation of heat and mass transfer across liquid-gas interfaces is that there are two heat transfer modes, namely, evaporation and heat conduction, at an evaporating liquid surface. Interfacial heat conduction was often overlooked in the analysis of evaporation of a liquid droplet. In this work, we derive the analytical expressions for the resistance to the heat and mass flow across a liquid-gas interface of an evaporating droplet from the kinetic theory of gases and verify the theoretical predictions by comparing them to molecular dynamics simulation results. The modeling results show that the temperature jump across the evaporating droplet surface is mainly associated with interfacial heat conduction rather than evaporation, and the vapor density near the liquid-gas interface is determined by the resistance to mass transfer, i.e., evaporation, at the interface. Using the expressions for interfacial thermal and mass transfer resistance, we formulate the temperature jump and vapor density boundary conditions at an evaporating droplet surface and determine the scenario under which the conventional assumptions of continuous temperature profile and saturated vapor at the liquid-gas interface become invalid.

Physical nature of size effects in TiAlNiAu/GaN ohmic contacts to AlGaN/GaN heteroepitaxial structures

The size effect observed in TiAlNiAu/GaN ohmic contacts (OCs) makes itself evident in the dependence of their relative electrical characteristics R SH , R SK , ρ and geometrical parameter L T on the LTLM test line width Wk . The paper explores the geometry of relief (topography) irregularities and their interface conductivity, indicating the great significance of the fractal geometry for the description of the electrophysical and device characteristics. The regularities discovered can be of great practical importance in terms of OC development and optimization for micro-/nanoelectronics demands.

Regulating Interfacial Spin Hall Conductivity with Ferroelectricity.

We report a new physical phenomenon of active and enhanced control of the spin Hall conductivity (SHC) in a family of metal-ferroelectric multilayers. Rather than the direction of the built-in electric field, such ferroelectric regulation of SHC originates from the drastic change of the interfacial electronic state along with its intrinsic Berry phase near the Fermi level due to the distinct hybridization between the metal film and substrate when the ferroelectric polarization reverses. Using Pt/PbZrTiO3 multilayers as a representative model, we demonstrate the controllability of a large magnitude and even the sign of SHC in the Pt film at the two interfaces with an antitype conducting carrier in a ferroelectric substrate. The interfacial Rashba effect plays a role in contributing to the change of SHC through spin-projected band analysis. The present work makes a fundamental theoretical discovery and opens up a new direction to manipulate spin-charge conversion of thin-film layered structures by ferroelectricity, which is crucial for designing future electric and spintronic devices.

SH wave vibration in functionally graded porous piezoelectric composite loaded with Newtonian conductive/non-conductive liquid

This study concentrates on the propagation pattern of shear horizontal (SH) waves on the conductive liquid-loaded porous piezoelectric media. Porous piezoelectric media is composed of fluid saturated functionally graded porous piezoelectric material (FGPPM) plate and functionally graded piezoelectric material (FGPM) half-space. The functional grading is assumed to be exponential for the FGPPM layer and quadratic for the FGPM layer respectively, along the direction of thickness. The mechanical imperfection is considered at the interface of the two media. The dispersion and the attenuation curve have been plotted to describe the impact of various parameters, namely gradient parameter of both the piezoelectric material, thickness of FGPPM plate, imperfect interface parameter, relative permittivity and conductivity of the liquid medium. Also, different modes for both the dispersion and attenuation curves have been delineated to get a better insight. Dispersion equations for non-conductive liquid loaded piezo-composite have also been obtained for both electrically open and short circuit conditions. To validate the present outcome, the geometry is reduced to special cases and the outcome is matched with pre-existing results. This article may find its application in better understanding of SAW devices incorporated with liquid layer.

Thermal model for time-domain thermoreflectance experiments in a laser-flash geometry

Time-domain thermoreflectance (TDTR) is a well-established pump–probe method for measuring thermal conductivity and interface conductance of multilayers. Interpreting signals in a TDTR experiment requires a thermal model. In standard front/front TDTR experiments, both pump and probe beams typically irradiate the surface of a multilayer. As a result, existing thermal models for interpreting thermoreflectance experiments assume that the pump and probe beams both interact with the surface layer. Here, we present a frequency-domain solution to the heat-diffusion equation of a multilayer in response to nonhomogeneous laser heating. This model allows analysis of experiments where the pump and probe beams irradiate opposite sides of a multilayer. We call such a geometry a front/back experiment to differentiate such experiments from standard TDTR experiments. As an example, we consider a 60nm amorphous Si film. We consider how signals differ in a front/front vs front/back geometry and compare thermal model predictions to experimental data.

Effect of interfacial spin mixing conductance on gyromagnetic ratio of Gd substituted Y3Fe5O12

Due to its low intrinsic damping, Y3Fe5O12 and its substituted variations are often used for ferromagnetic layer at spin pumping experiment. Spin pumping is an interfacial spin current generation in the interface of ferromagnet and non-magnetic metal, governed by spin mixing conductance parameter G↑↓. G↑↓ has been shown to enhance the damping of the ferromagnetic layer. The theory suggested that the effect of G↑↓ on gyromagnetic ratio only comes from its negligible imaginary part. In this article, we show that the different damping of ferrimagnetic lattices induced by G↑↓ can affect the gyromagnetic ratio of Gd-substituted Y3Fe5O12.

Simple and sensitive nitric oxide biosensor based on the electrocatalysis of horseradish peroxidase on AuNPs@metal-organic framework composite-modified electrode.

Fe-based metal–organic framework (MIL-101(Fe)) was synthesized through a simple solvothermal synthesis and then used to prepare the AuNPs-decorated MIL-101(Fe) nanocomposite (APPPM(Fe)) by a multi-step layer-by-layer assembly process. Benefited from the porous structure of MIL-101(Fe) and the multilayer assemble process, the loading amount of AuNPs on APPPM(Fe) was enhanced and exhibited a fine biocompatible interface and high conductivity. Through the intense Au–S bond, high loading amount of horseradish peroxidase was immobilized on APPPM(Fe) and the native bioactivity of HRP was kept to realize its direct electrochemistry. From the electrochemical kinetics, the constructed biosensor displayed fast electron transfer and good electrocatalysis activity for the detection of nitric oxide (NO) with wide linear range from 0.033 to 5370 μM and a low detection limit of 0.01 μM (3 σ) as well as fine stability, reproducibility and specificity. According to results of real sample analysis, the proposed electrochemical biosensor offers fast and simple detection of NO in real serum. Therefore, the present strategy definitely provided a potential application prospect in NO clinic detection and disease therapy.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s00604-022-05268-8.

Nickel Coated Polyester Sponge for Delaying the Specific Aggregation of Fine Particles Induced by Negative Air Ions.

Negative air ions (NAIs) produced by corona discharge is often used for indoor air purification; however, the specific aggregation of suspended particles caused by NAIs, especially fine particles (FPs), needs to be considered. Here, a nickel coated conductive sponge (NCCS) was used as the main adsorption interface for delaying the obstinate aggregation caused by NAIs on another surface. The specific aggregation of FPs is caused by the directional transfer of electric charge, and the oxidation characteristic of NAIs results in the surface reaction of FPs simultaneously. The conductivity and roughness of the adsorption interface determine the migration direction and enrichment number of FPs, respectively. Nickel coated conductive sponge with high conductivity and high specific surface area can effectively adsorb the FPs affected by NAIs and can effectively delay the specific aggregation on the surface of indoor objects.

Enhanced subterahertz spin-current transients via modulation of cross-sublattice damping in uniaxial antiferromagnets

We present an analytical model to compute the subterahertz (sub-THz) spin current transients injected from the insulating uniaxial antiferromagnet (AFM) into the adjacent nonmagnetic layer excited by spin pumping under the antiferromagnetic resonance condition, where both intra- and cross-sublattice damping parameters are treated on an equal footing. As expected, the sub-THz spin-pumping signal decreases with larger intra-sublattice damping dissipation. Interestingly, it is found that the amplitude of the spin current transient is enhanced with increasing cross-sublattice damping. On the other hand, the spin pumping is reduced by increasing the cross-sublattice spin-mixing conductance. These trends indicate that the intrinsic origin of the cross-sublattice damping in the bulk AFM enhances the spin current transients while its extrinsic origin, directly related to the interfacial cross-sublattice spin-mixing conductance, has the opposite effect. Our results suggest the important role of the previously neglected cross-sublattice damping in modulating the sub-THz spin current pulses for ultrafast spintronic applications.

Ferroelectric Engineered Electrode-Composite Polymer Electrolyte Interfaces for All-Solid-State Sodium Metal Battery.

To enhance the compatibility between the polymer‐based electrolytes and electrodes, and promote the interfacial ion conduction, a novel approach to engineer the interfaces between all‐solid‐state composite polymer electrolyte and electrodes using thin layers of ferroelectrics is introduced. The well‐designed and ferroelectric‐engineered composite polymer electrolyte demonstrates an attractive ionic conductivity of 7.9 × 10–5 S cm–1 at room temperature. Furthermore, the ferroelectric engineering is able to effectively suppress the growth of solid electrolyte interphase (SEI) at the interface between polymer electrolytes and Na metal electrodes, and it can also enhance the ion diffusion across the electrolyte‐ferroelectric‐cathode/anode interfaces. Notably, an extraordinarily high discharge capacity of 160.3 mAh g–1, with 97.4% in retention, is achieved in the ferroelectric‐engineered all‐solid‐state Na metal cell after 165 cycles at room temperature. Moreover, outstanding stability is demonstrated that a high discharge capacity retention of 86.0% is achieved over 180 full charge/discharge cycles, even though the cell has been aged for 2 months. This work provides new insights in enhancing the long‐cyclability and stability of solid‐state rechargeable batteries.

Tuning of the microstructural and electrical properties of undoped BaTiO3 by spark plasma sintering

The distribution of oxygen vacancies in BaTiO3 specimens can greatly affect material electrical properties. Spark plasma sintering followed by annealing in controlled pO2 atmospheres offers the potential to control the oxygen vacancy distribution. Impedance spectroscopy has been used to study the electrical characteristics of undoped BaTiO3 specimens prepared at 1200 °C under a pressing pressure of 5 MPa and 50 MPa using spark plasma sintering (SPS). For both samples, at temperatures greater than 750 °C, the total conductivity is determined by the bulk conductivity (σb), while at temperatures between 550 °C–750 °C the total conductivity is determined by the grain boundary conductivity (σgb). Below 550 °C, the total conductivity is determined by the BaTiO3–Pt interface conductivity (σel). The bulk, grain boundary and electrode interface resistances and activation energies are lower for samples sintered and pressed at 50 MPa, compared to specimens sintered and pressed at 5 MPa. Plots of grain boundary conductivity (σgb) vs. oxygen partial pressure (pO2) (log(σgb) vs. log(pO2)), over the temperature range 517 °C–683 °C, have slopes of approximately 4.0 indicating that doubly charged oxygen vacancies (VO••) are located at the grain boundaries. The grain boundary region and BaTiO3–Pt interface conductivities are highly sensitive to the oxygen partial pressure. Therefore, SPS sintered BaTiO3 specimens that have been subjected to controlled annealing could be used to tailor BaTiO3 dielectric properties, as well as have potential applications in high temperature O2 sensing. Furthermore, analysis of a.c. conductivity using the Jonscher model reveals that the governing charge transport mechanism is via quantum mechanical tunneling (QMT), which operates at temperatures when grain boundaries control the total conductivity. The mechanism switches to the correlated barrier hopping (CBH) model at temperatures when the bulk controls the total conductivity.

Interface-driven spin pumping and inverse Rashba-Edelstein effect in FeGaB/Ag/BiSb multilayers

Spin-orbit-coupling (SOC) plays a critical role in spin-to-charge conversion (SCC) mechanism. The SCC process is usually investigated by injecting a spin current from ferromagnet (FM) into a large SOC normal metal (SOC-NM) and then measuring the voltage generated by inverse spin Hall effect (ISHE). Recently, a new mechanism of SCC at inversion symmetry breaking interfaces between topological insulators (TIs) and magnetically ordered materials has been introduced, which is driven by the inverse Rashba-Edelstein effect (IREE). Motivated by this result, we have investigated the IREE effect of a simple binary three-dimensional TI Bi85Sb15 (BiSb). The model system used here is a trilayer of FeGaB/Ag/BiSb with different Ag thickness made insitu with a combination of dc magnetron sputtering and pulsed laser ablation. The SCC efficiency has been evaluated by measuring ferromagnetic resonance (FMR) driven ISHE voltage and extraction of the Gilbert damping (α) and interfacial spin mixing conductance (g↑↓) from the FMR line shape analysis. It is interesting to note that the charge current (Ic) increases with Ag thickness. This observation indicated that the IREE process at the Ag/BiSb interface dominates over ISHE in the bulk of BiSb film. The conversion efficiency of IREE is determined by calculating the IREE length (λIREE), which increases with the thickness of the Ag layer. These findings offer a method to generate and detect the IREE in a room temperature deposited heterostructure using simple coplanar waveguide setup.

Vertical organic phototransistors realized by femtosecond laser ablation patterned metal/insulator bilayer source electrodes: Performance and numerical modeling

Compared with their conventional lateral counter parts, vertical organic phototransistors (VOPTs) have the advantage of fast response speed due to short channel lengths, and may find wide applications in the field of high speed photo detection. By operation of VOPTs, the source electrode plays the vital role. We report on fabrication, characterization and analysis of VOPTs with pulsed laser ablation patterned Al/LiF bilayer source electrode. A maximal photoresponsivity of 760 mA/W, external quantum efficiency ( EQE ) of 145%, specific detectivity of 1.6 × 10 11 Jones were obtained for un-optimized devices. For describing the output characteristics of the devices, a rough numerical model was developed by combining the theory of thermionic emission at metal/organic interface and space charge limited current conduction. • We innovatively achieved the manufacture of vertical channel field-effect transistors by using a porous metal/insulator bilayer source electrode. • We patterned the porous electrode by femtosecond laser ablation. • We proposed a phenomenological device model to getting quantitative insight into the working mechanism of VOPTs. • The un-optimized device in this work showed a maximal photoresponsivity of 760 mA/W, EQE of 145%, specific detectivity of 1.6 × 10 11 Jones.

Bridging Evolution of the Solvation Sheath to Rigid‐Soft Coupling and Low‐Resistance Solid Electrolyte Interface for Fast‐Charging and Ultrastable Bi Anode

AbstractThe key issue holding back the application of Bi‐based lithium‐ion battery (LIB) is the rigorous requirements of low interfacial resistance, superior mechanical stability, and high ion conductivity of solid electrolyte interface (SEI). In this work, inspired by human musculoskeletal tissues, a multifunctional SEI with low interfacial resistance and synergistic rigid‐soft features is in situ constructed through the interfacial evolution of PF6 anion‐derived solvation sheath at the Bi anode, facilitating Li ion conductivity, and SEI/electrolyte interface wettability, alleviating the enormous volumetric expansion of Bi anodes, and offering superior Bi/SEI/electrolyte compatibility during long‐term cycles. Attributed to these superiorities, an unprecedented cycling stability can be obtained, i.e., 94.4% capacity retention at 2.6 C after 1000 cycles and 89.6% capacity retention at 5.2 C after 1300 cycles. When this anode is coupled with a LiFePO4 cathode, the full cell delivers superior cyclability with 85.2% capacity retention at 0.6 C after 100 cycles. This research provides new insight into handling the interfacial compatibility and fast‐charging issues of Bi‐based LIB.

Corrosion-resistant and interfacial conductive AlTiVCrMo high-entropy alloy and (AlTiVCrMo)Nx high-entropy ceramics coatings for surface modification of bipolar plates in proton exchange membrane fuel cells

Metal bipolar plates (BPPs) are candidates with great promise to replace conventional carbon-based BPPs. However, the drawbacks caused by the corrosion and passivation of metal bipolar plates need to be addressed urgently. In present study, corrosion-resistant and interfacial conductive high-entropy alloy and ceramic coatings possess great potential in the application of surface modification of bipolar plates in proton exchange membrane fuel cells (PEMFCs). An original co-filtered cathodic vacuum arc deposition (C-FCVAD) is designed to prepare AlTiVCrMo high-entropy alloy (HEA) and (AlTiVCrMo)Nx high-entropy ceramic (HEC) coatings with different nitrogen content, and their feasibility as surface modification methods of bipolar plates is investigated by analyzing the microstructure, corrosion properties, interfacial conductivity and hydrophobicity of the coatings. The obvious body-centered cubic (BCC) structure can be observed in HEA coating, and amorphous structure is gradually formed as the nitrogen content increases to 28.12 at. %. Finally, polycrystal structure is formed when nitrogen content reached the maximum. The electrochemical corrosion and interfacial contact resistance (ICR) results significantly demonstrate that the coatings have enhanced corrosion resistance and conductivity. The bipolar plates with AlTiVCrMo HEA and (AlTiVCrMo)Nx HEC coatings as surface modification methods have good application potential in PEMFCs operating environment.

Cu particles confined in three-dimensional open porous carbon foam monolith as highly efficient electrode for electroreduction of nitrate with significant alleviation of nitrite

Electroreduction of nitrate is a promising approach and attracting increasing attention in recent years. However, most studies focus on conventional planar electrodes whose flat structure causes limited mass transfer and low nitrate reduction efficiency. Herein, we prepared a novel Cu-containing particle-embedded 3D open porous carbon foam monolith (3D-PCF) electrode for electroreduction of nitrate. The 3D-PCF was prepared by foaming of molten sucrose, followed by dehydration and carbonization. Then Cu-containing particle was in-situ fabricated on the 3D-PCF using a hydrothermal procedure and a subsequent annealing treatment. Benefitting from the advantages of 3D open porous architecture, highly active interface and excellent electron conductivity of the carbon skeleton, the optimized electrode exhibited 99.9% nitrate removal efficiency in 1 h and 100 % N2 selectivity with the aid of chlorine oxidation in 3 h. The reduction rate of the optimized electrode was about 2.44 times of the 3D Cu foam (15 pieces of Cu foam with the same size as the optimal electrode). Impressively, the catalyst enabled significant alleviation of nitrite because the 3D-PCF substrate could eliminate nitrite rapidly. This work highlights the promise of preparing highly efficient electrocatalyst for efficiently and selectively removing nitrate through supporting of active material onto a 3D monolith substrate.