Local Conductivity Research Articles

Solvent Mediated Interfacial Microenvironment Design for High-Performance Electrochemical CO2 Reduction to C2+ Products.

Electrochemical CO2 reduction (CO2RR) in membrane electrode assembly (MEA) represents a viable strategy for converting CO2 into value-added multi-carbon (C2+) compounds. Therefore, the microstructure of the catalyst layer (CL) affects local gas transport, charge conduction, and proton supply at three-phase interfaces, which is significantly determined by the solvent environment. However, the microenvironment of the CLs and the mechanism of the solvent effect on C2+ selectivity remains elusive. Herein, a tailored interfacial structure is designed by introducing a solvent-mediated catalyst-ionomer-solvent microenvironment. The acetone surface promotion strategy is beneficial for the unfolded ionomers to uniformly coat the catalysts, which contributes to enhancing interfacial hydrophobicity and inhibiting hydrogen evolution. Furthermore, molecular dynamics (MD) simulation and in situ ATR-SEIRAS are employed to elucidate the appropriate interfacial network with a balanced distribution of CO2 and H2O. The uniform and continuous network in acetone is advantageous for CO2-to-C2+. The optimized structure favors the production of C2+ products in Cu-based MEA, exhibiting a high C2+ faradaic efficiency (FE) of 80.27% at 400mA cm-2.

Scanning microwave impedance microscopy and its applications: A review

Scanning microwave impedance microscopy (sMIM) has become a powerful tool for nanoscale characterization, utilizing microwave frequencies to probe the material properties of diverse systems with remarkable spatial resolution. This review offers an in-depth analysis of the foundational principles, technological advancements, and broad applications of sMIM. By harnessing near-field microwave interactions between a sharp metallic probe and the sample, sMIM enables simultaneous acquisition of both real (resistive) and imaginary (capacitive) components of the reflected signal, providing detailed insights into the local permittivity and conductivity of materials at the nanoscale. We address critical challenges, including impedance matching, probe–sample interactions, and the influence of environmental factors such as surface water layers and meniscus formation on resolution and contrast. Recent advancements in finite element modeling and the application of lumped-element circuit models have further enhanced the precision of signal interpretation, enabling more accurate analysis of complex systems. This review highlights sMIM’s wide-ranging applications, from material science and semiconductor diagnostics to biological systems, showcasing its ability to perform non-destructive, high-resolution imaging down to the single-digit nanometer scale. These capabilities position sMIM as an indispensable tool for advancing future innovations in nanotechnology and related fields.

Cavitation dynamics and thermodynamic effect of R134a refrigerant in a Venturi tube.

Cavitation plays a crucial role in the reliability of components in refrigeration systems. The properties of refrigerants change significantly with temperature, thereby amplifying the impact of thermodynamic effects. This study, based on the Large Eddy Simulation (LES) method and the Schnerr-Sauer (S-S) cavitation model, investigates the transient cavitating flow characteristics of the R134a refrigerant in a Venturi tube (VT). The bubble number density in the S-S model was improved based on the experimental data of pressure and temperature. Simulation results indicate that there are two shedding modes of cavitation clouds in R134a refrigerant. One is induced by the combined action of reentrant flow and the vortices centrifugal force, while the other is generated by the central jet of the mainstream and the reverse jet produced by the collapsing cavitation bubbles. Furthermore, the thermodynamic effects of the refrigerant exert a certain inhibitory effect on cavitation, revealing the causes of instability in the refrigerant cavitation interface and the shedding characteristics of cavitation clouds. The relationship between local sound speed, flow velocity, and heat conduction rate in the cavitation region was studied, unveiling a time-lag in temperature changes relative to pressure changes in the intensive cavitation region. This study provides insights into the complex cavitation dynamics, especially in R134a refrigerant systems, and provides an approach for accurately predicting and managing cavitation in various industrial applications.

Disclosing the contribution of vacancy defects to thermal transport at a liquid-Al/graphene adhesion interface.

The adhesion properties of liquid-solid interfaces are of fundamental importance in the performance and design of nanodevices. Modulating interfacial thermal transport has the potential to enhance interfacial heat dissipation in nanodevices. Herein, the adhesive characteristics of the liquid-solid interface formed by liquid-Al/graphene are reported using molecular dynamics, and the intrinsic mechanism of interfacial adhesion evolution and energy-heat transport is revealed. Specifically, an increase in temperature significantly reduces the adhesion and thermal transport capacity. Concurrently, the expansion of vacancy defects strengthens the interfacial adhesion property. This is due to the fact that the enlarged vacancy defects enhance the local contact and interfacial thermal conductance (ITC) between the atoms, thereby optimizing interfacial energy transport. The augmented ITC facilitates interfacial energy-heat exchange and phonon participation rate (PPR), and thus increases interfacial phonon modes and further reinforces the adhesion strength. This paper elucidates the evolution of interfacial adhesion characteristics of liquid-Al/graphene, providing substantial guidance for a more comprehensive understanding of energy transport at the liquid-solid interface.

Non-local thermal transport impact on compressive waves in two-temperature coronal loops

Context. Observations of slow magnetoacoustic waves in solar coronal loops suggest that in hot coronal plasma, heat conduction may be suppressed in comparison with the classical thermal transport model. Aims. We link this suppression with the effect of the non-local thermal transport that appears when the plasma temperature perturbation gradient becomes comparable to the electron mean-free-path. Moreover, we consider a finite time of thermalisation between electrons and ions so that separate electron and ion temperatures can occur in the loop. Methods. We numerically compared the influence of the local and non-local thermal transport models on standing slow waves in one- and two-temperature coronal loops. To quantify our comparison, we used the period and damping time of the waves as commonly observed parameters. Results. Our study reveals that non-local thermal transport can result in either shorter or longer slow-wave damping times in comparison with the local conduction model due to the suppression of the isothermal regime. The difference in damping times can reach 80%. For hot coronal loops, we find that the finite equilibration between electron and ion temperatures results in an up to 50% longer damping time compared to the one-temperature case. These results indicate that non-local transport will influence the dynamics of compressive waves across a broad range of coronal plasma parameters with Knudsen numbers (the ratio of mean-free-path to temperature scale length) larger than 1%. Conclusions. In the solar corona, the non-local thermal transport shows a significant influence on the dynamics of standing slow waves in a broad range of plasma parameters, while two-temperature effects come into play for hot and less dense loops.

ЦИФРОВАЯ И РЕНТГЕНОЛОГИЧЕСКАЯ ОЦЕНКА ВАРИАБЕЛЬНОСТИ АНАТОМО-ТОПОГРАФИЧЕСКИХ ПАРАМЕТРОВ ПОДГЛАЗНИЧНОГО ОТВЕРСТИЯ (ОБЗОРНАЯ СТАТЬЯ)

The variability of the craniometric parameters of the infraorbital foramen of the anterior surface of the body of the upper jaw is noted in a large number of scientific publications, which indicates the need for an individual approach when assessing the shape, the number of additional holes in the area of the infraorbital foramen, the location of this anatomical formation of the facial skeleton in relation to the lower edge of the orbit, and the bones of the cavity nose and alveolar process, and many scientific researchers note that the location of the infraorbital foramen on the right and left sides differs in level, there are often different shapes of the infraorbital foramen and additional canals are also found either on the right or on the left side and their shape also differs from each other from a friend. All this affects the effectiveness of local conduction anesthesia in the area of the infraorbital foramen, so digital and radiological assessment using cone beam computed tomography will help ensure the accuracy and safety of this type of conduction anesthesia.

Inhomogeneous Nanoscale Conductivity and Friction on Graphite Terraces Explored via Atomic Force Microscopy

The interplay of conductivity and friction in layered materials such as graphite is an open area of investigation. Here, we measure local conductivity and friction on terraces of freshly cleaved highly oriented pyrolytic graphite via atomic force microscopy under ambient conditions. The graphite surface is found to exhibit a rich electrical landscape, with different terraces exhibiting different levels of conductivity. A peculiar dependency of conductivity on scan direction is observed on some terraces. The terraces that exhibit this dependency are also found to show enhanced friction values. A hypothesis based on tip asymmetry and the puckering effect is proposed to explain the findings. Our results highlight the non-triviality of the electrical and tribological properties of graphite on the nanoscale, as well as their interplay.

Local optical conductivity of strain solitons in bilayer graphene with arbitrary soliton angle

Local optical conductivity of strain solitons in bilayer graphene with arbitrary soliton angle

Scanning Microwave Impedance Microscopy for Characterization of Graphene Systems Encapsulated by Hexagonal Boron Nitride

Scanning microwave impedance microscopy (sMIM) is a near‐field technique that enables the characterization of conductive materials with a resolution down to 1 nm. In hexagonal boron nitride (hBN)‐encapsulated devices, microwaves emitted from the sMIM tip penetrate and reach with the underlying 2D materials, allowing for the mapping of local conductivity variations. Using twisted bilayer graphene, it is demonstrated that this technique can characterize moiré patterns through hBN flakes up to 2.5 nm thick. Additionally, it is showed that sMIM can distinguish between conductive and insulating materials in samples encapsulated by hBN layers exceeding 15 nm. A key finding is that signal decay due to encapsulation is intrinsically linked to the tip's condition. This work overcomes limitations in the application of twistronics, enabling the verification of the periodicity of moiré patterns in high‐quality encapsulated devices between electrical contacts.

Synthesis, Thermal Stability, and Proton-Conductivity of the Mixed-Cation Phosphate with One-Dimensional Tunnels Formed by PO4 Tetrahedral Rings

The Benitoite-type phosphate, KMg1-x H2 x (PO3)3·yH2O, is a promising material as a solid electrolyte for automotive fuel cells due to its high proton conductivity from room temperature to 500°C1). The Benitoite-type KMg1-x H2 x (PO3)3·yH2O has a layered structure stacking the units formed by the units formed by P3O9 ring and those composed of (KO6)(MgO6) octahedral units. The P3O9 ring forms one-dimensional tunnels with a cage large enough to occupy H2O(or H3O+), which would provide proton conduction pathway. However, the correlation between the local structure and proton conductivity of this material has not yet been investigated. In this study, with the aim of further improving proton conductivity, we synthesized Benitoite-type phosphate with new compositions by introducing protons as charge compensation by replacing Mg2+ with Li+.KMg1-x Li x H x (PO3)3·yH2O were synthesized by a coprecipitation method. In the X-ray diffraction patterns for the samples with x = 0 - 0.3, the formation of the single phase of Benitoite-type structure with the space group P-6c2 was confirmed. Both the a and c axes tend to decrease with x in these compositions reflecting the formation of a solid solution. Fig.1 shows FT-IR spectra of KMg1-x Li x H x (PO3)3·yH2O. In the FT-IR spectra, the absorption peaks corresponding to the vibrational modes of POH and OH became relatively stronger for x, suggesting an increase in the proton contents in the samples. The lattice shrinkage by replacing Li+(0.76 Å) with an ionic radius larger than Mg2+(0.72 Å) would be caused by increasing of hydrogen bonds in the structure. In the TG/DTA measurement, the dehydration reactions from room temperature and 150°C were observed, and the water content increased with increasing x. This is suggested that the acidity of the framework is enhanced by the introduced protons, causing water molecules tend to incorporate into the crystal structure as Lewis bases. The shape of the pellet with x > 0.1 was not retained after retained under 80% relative humidity at room temperature.The conductivity of samples was measured by using AC impedance method. The impedance plots for the sample depict a part of semicircle due to the grain boundary and spike caused by the electrode contribution. The total resistance was determined from the intersection of the spike and the real axis, and the conductivity was calculated. The proton conductivity of the sample with x = 0.1 was higher than that of x = 0 under a humidified N2 gas flow (P H2O = 3 kPa). the sample with x = 0.1 showed high proton conductivity exceeding 10-3 S cm-1 from room temperature to 500 ℃, and the highest value of 1.9×10-2 S cm-1 was observed at 200°C under a humidified N2 gas flow( P H2O = 3 kPa). Only the sample with water of crystallization exhibited high conductivity, which suggests domination of proton diffusion via water of crystallization. The conductivity of the Li-substituted Benitoite tends to show higher proton conductivity than Mg-deficiency sample at the same proton content.Reference1) Y. Matsuda, et al, Dalton Trans., 50, 7678 (2021).AcknowledgementThis research was partially supported by Kanto Branch of the Electrochemical Society of Japan, JSPS KAKENHI Grant Number 24K08584 and 21K05246. Figure 1

Revealing Structure-Property Correlations in New Solid Electrolyte Materials for All-Solid-State-Batteries Using Synchrotron X-Ray Analysis

There have been enormously increasing demands for developing next-generation Li-ion batteries with enhanced energy & power density and safety features compared with the current state-of-the-art LIB technology. Such advances necessitate the successful development and implementation of the new cathode, anode, and (solid)electrolyte materials. In this regard, understanding the structure-property correlation of advanced battery materials has now become a central aspect of battery research. Synchrotron-based x-ray techniques such as x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) have been identified as ideal and powerful tools for in situ studies of lithium-ion battery materials. This presentation will discuss how such advanced characterization tools can be employed in the diagnostic study of battery materials to reveal the working and failure mechanism. I will present the application of various synchrotron x-ray tools, including pair distribution function (PDF) analysis and tender x-ray absorption spectroscopy, to investigate sulfide and halide-based solid-electrolyte materials. The correlation between local atomic structure changes and ionic conductivity will be discussed.

Carrier localization in defected areas of (Cd, Mn)Te quantum well investigated via Optically Detected Magnetic Resonance employed in the microscale

In this work, we study the impact of carrier localization on three quantities sensitive to carrier gas density at the micrometer scale: charged exciton (X+) oscillator strength, local free carrier conductivity, and the Knight shift. The last two are observed in a micrometer-scale, spatially resolved optically detected magnetic resonance experiment (ODMR). On the surface of MBE-grown (Cd,Mn)Te quantum well we identify defected areas in the vicinity of dislocations. We find that these areas show a much lower conductivity signal than the pristine part of the sample, while Knight shift values remain approximately unchanged. We attribute this behavior to carrier localization in the defected regions.

Emerging Spatiotemporal Dynamics in Multiterminal Neuromorphic Nanowire Networks Through Conductance Matrices and Voltage Maps

AbstractSelf‐organizing memristive nanowire (NW) networks are promising candidates for neuromorphic‐type data processing in a physical reservoir computing framework because of their collective emergent behavior, which enables spatiotemporal signal processing. However, understanding emergent dynamics in multiterminal networks remains challenging. Here experimental spatiotemporal characterization of memristive NW networks dynamics in multiterminal configuration is reported, analyzing the activation and relaxation of network's global and local conductance, as well as the inherent spatial nonlinear transformation capabilities. Emergent effects are analyzed i) during activation, by investigating the spatiotemporal dynamics of the electric field distribution across the network through voltage mapping; ii) during relaxation, by monitoring the evolution of the conductance matrix of the multiterminal system. The multiterminal approach also allowed monitoring the spatial distribution of nonlinear activity, demonstrating the impact of different network areas on the system's information processing capabilities. Nonlinear transformation tasks are experimentally performed by driving the network into different conductive states, demonstrating the importance of selecting proper operating conditions for efficient information processing. This work allows a better understanding of the local nonlinear dynamics in NW networks and their impact on the information processing capabilities, providing new insights for a rational design of self‐organizing neuromorphic systems.

Electric-Field Control of the Local Thermal Conductivity in Charge Transfer Oxides.

Phonons, the collective excitations responsible for heat transport in crystalline insulating solids, lack electric charge or magnetic moment, which complicates their active control via external fields. This presents a significant challenge in designing thermal equivalents of basic electronic circuit elements, such as transistors or diodes. Achieving these goals requires precise and reversible modification of thermal conductivity in materials. In this work, the continuous tuning of local thermal conductivity in charge-transfer SrFeO3-x and La0.6Sr0.4CoO3-x oxides using a voltage-biased Atomic Force Microscopy (AFM)tip at room temperature is demonstrated. This method allows the creation of micron-sized domains with well-defined thermal conductivity, achieving reductions of up to 50%, measured by spatially resolved Frequency Domain Thermoreflectance (FDTR). By optimizing the oxide's chemical composition, the thermal states remain stable under normal atmospheric conditions but can be reverted to their original values through thermal annealing in air. A comparison between Mott-Hubbard and charge-transfer oxides reveals the critical role of redox-active lattice oxygen in ensuring full reversibility of the process. This approach marks a significant step toward fabricating oxide-based tunable microthermal resistances and other elements for thermal circuits.

Black Jamun Fruit Peel Extract Modified Gum Acacia Biopolymer Suitable for Energy Device Applications via Charge Transfer Enhancement

The visible light absorption capabilities, along with its electrical characteristics, of a low-cost, plant-based, biopolymer, gum acacia, have been chemically modified by tailoring its defect concentrations via pH modification, where the acid solvent of fruit (peel) extracts of jamun was used to influence the chemical structure by reactive modification. Ultraviolet-visible and photoluminescence spectroscopy of the gum acacia biopolymer treated with the extracted anthocyanin from jamun peel showed a prominent, characteristic red shift in the visible spectrum range. Impedance spectroscopy analysis showed the occurrence of localized ionic conduction. The bulk conductivity of the modified specimens increased due to the profound release of conducting ions in the water-swollen network. The reactively modified biopolymer could be used in multiple fields of material science, specifically in energy device applications, viz., photovoltaics (PV), by utilizing its cost effectiveness and photolytic effectiveness. 2nd, as a polymer electrolyte and dye-sensitised solar cells (DSSCs) material by utilizing its capacity of gel formation. In our research described in this article, the underlying charge transfer mechanism for such responses was examined after crosslinking in the organic dyes extracted from the peel of jamun fruit with gum acacia.

First photon-counting detector computed tomography in the living crocodile: a 3D-Imaging study with special reference to amphibious hearing.

Crocodiles are semi-aquatic animals well adapted to hear both on land and under water. Currently, there is limited information on how their amphibious hearing is accomplished. Here, we describe, for the first time, the ear anatomy in the living crocodile using photon-counting detector computed tomography (PCD-CT) and 3D rendering. We speculate on how crocodiles, despite their closed ear canals, can use tympanic hearing in water that also provides directional hearing. A Cuban crocodile (Crocodylus rhombifer) underwent photon-counting detector computed tomography (PCD-CT), under anesthesia and spontaneous respiration. In addition two seven-month-old C. rhombifer and a juvenile Morelet´s crocodile (Crocodylus moreletii) underwent micro-computed tomography (µCT) and endoscopy. One adult Cuviérs dwarf caiman (Paleosuchus palpebrosus) was micro-dissected and video-recorded. Aeration, earflap, and middle ear morphology were evaluated and compared after 3D modeling. PCD-CT and µCT with 3D rendering and segmentation demonstrated the anatomy of the external and middle ears with high resolution in both living and expired crocodiles. Based on the findings and comparative examinations, we suggest that the superior earflap, by modulating the meatal recess together with local bone conduction, may implement tympanic hearing in submerged crocodiles, including directional hearing.

Stochastic and alternating pacing paradigms to assess the stability of cardiac conduction

Reentry, the most common cause of severe arrhythmias, is initiated by slow conduction and conduction block. Hence, evaluating conduction velocity and conduction block is of primary importance. However, the assessment of cardiac conduction safety in experimental and clinical settings remains elusive. To identify markers of conduction instability that can be determined experimentally, we developed an approach based on new pacing paradigms. Conduction across a cardiac tissue expansion was assessed in computer simulations and in experiments using cultures of neonatal murine cardiomyocytes on microelectrode arrays. Simulated and in vitro tissues were paced at a progressively increasing rate, with stochastic or alternating variations of cycle length, until conduction block occurred. Increasing pacing rate led to conduction block near the expansion. When stochastic or alternating variations were introduced into the pacing protocol, the standard deviation and the amplitude of alternating variations of local conduction times emerged as markers of unstable conduction prone to block. In both simulations and experiments, conduction delays were prolonged at the expansion but increased only slightly during the pacing protocol. In contrast, these markers of instability increased several-fold, early before block occurrence. The first and second moments of these two metrics provided an estimation of the site of block and the accuracy of this estimation. Therefore, when beat-to-beat variations of pacing cycle length are introduced into a pacing protocol, the local variability of conduction permits to predict sites of block. Our pacing paradigms may have translational applications in clinical cardiac electrophysiology, particularly in identifying ablation targets during mapping procedures.

Two-dimensional electronic conductivity in insulating ferroelectrics: Peculiar properties of domain walls

Ferroelectrics such as LiNbO3 (LN) are wide-band-gap insulators that may show a high local electric conductivity at the domain walls (DWs). The latter are interfaces separating regions of noncollinear polarization, which can be manipulated to build integrated nanoelectronic elements. In the present work, we model different DW types in LN from first principles. Our models reveal the DW morphology and shed light on their electronic properties: A strong band bending is predicted for charged DWs, leading to local metallicity. Defect trapping at the DW may further enhance the electric conductivity. Published by the American Physical Society 2024

An investigation on magnetic-fluid heat transfer in square tube under constant, oscillating electromagnetic fields

ABSTRACT In this work, a magnetic fluid (Fe3O4/water) moving through a square tube in a steady-state and fluctuating electromagnetic field was investigated experimentally. The relevant parameter effects are considered, including rotating direction, flux, frequency, and frequency on the heat removal ability and flow resistance. The electromagnetic field induces the particles to move to the square tube wall, greatly influencing the boundary layer disturbance. A greater electromagnetic flux and rotating direction enhance nanoparticle turbulence intensity and local thermal conductivity. Compared to when it is fixed, the Nu of an electromagnetic field oscillating at 1.25 hz, 2.3 µT, is 9.16% more. Additionally, compared to the other modes, the Nu is greater by 3.41% when the mixed mode of the electromagnetic field rotates at 1.25 hz and 0.5 µT. The heat-removal capacity may be significantly increased by increasing the electromagnetic flux and frequency, which raises the Nu. The f is also further increased by the disruption of electromagnetic flow.

Investigation on in-situ thermal behavior of tunnel surrounding rock based on the thermal probe test

Heat-transfer mechanism of energy tunnel is different from that of conventional borehole heat exchanger, where the thermal flux flows along perpendicular to the tunnel circumferential direction. However, the existing measurement methods cannot directly detect the in-situ thermal behavior and thermal conductivity of surrounding rock of tunnel circumferential direction. Hence, a thermal probe test (TPT) equipment was developed and the TPT was performed to investigate the in-situ thermal behavior of surrounding rock, the thermal conductivity measurement methods of tunnel surrounding rock was proposed and compared with laboratory measurement methods. The results showed that the developed TPT equipment achieved to directly detect the in-situ thermal behavior and thermal conductivity of circumferential surrounding rock. There was a significant variation in thermal response curves of different test areas due to the fact that joint development affected the transfer paths of the thermal flux, the temperature difference between test point 1 and test point 2 could reach up to 11.4 °C. The thermal conductivity tested by TPT was reliable and reflected the in-situ thermal behavior, the deviation was 6.99 % and 1.08 %, respectively, compared with laboratory measurement results. The joint development of the surrounding rock had a major impact on the thermal conductivity, where the thermal conductivity ranged from 0.66 to 2.91 W/m K in the 1# borehole and 1.96 to 3.66 W/m K in the 2# borehole. The local thermal conductivities were difficult to apply to an energy tunnel design, hence, the comprehensive thermal conductivity model of surrounding rock with joints was proposed based on series–parallel theory and was simplified according to the heat-transfer mechanism of energy tunnel. The comprehensive thermal conductivity model provided a new idea for obtaining the heterogeneity of thermal-physical properties of tunnel surrounding rock, which improved performance predictions and optimized design strategies for energy tunnel projects, enhancing their efficiency and reliability in various applications.