Conductivity Hysteresis Research Articles

Dynamic thermal and mass transport in PEM fuel cells at elevated temperatures and pressures: A 3D model study

Next-generation proton-exchange membrane fuel cells (PEMFCs) encounter significant challenges at elevated temperatures (OTs) and pressures (OPs) due to local thermal and mass fluctuations. In this study, a three-dimensional transient model was developed to analyze these dynamics by incorporating the effects of the microporous layer and variations in the coolant temperature along the channel. The results indicate that increasing the OT from 80 °C to 90 °C decreases the output voltage by 34–78 mV, increases voltage undershoot/overshoot by 0.2–16.6 mV, and raises the temperature difference between the cathode catalyst layer (cCL) and coolant from 1.2 to 2.1 °C, leading to more irregular temperature fluctuations in the cCL. These effects stem from the increased gas–liquid water outflow within the cCL that induces membrane dehydration, particularly in the electrolyte near the channel. Consequently, the lag in proton conduction relative to the oxygen reduction reaction (ORR), as quantified by the newly introduced Damköhler number, has emerged as a critical factor that influences both heat transfer and reaction kinetics. Conversely, increasing OPs from 130 kPa [anode]/120 kPa [cathode] to 400 kPa [anode]/390 kPa [cathode] improves output voltage by 50–150 mV and reduces proton conduction hysteresis by 12–54 % under dynamic loads. This improvement is linked to higher O2 concentration and membrane water facilitated by a 0.6–2 °C decrease in cCL temperature. However, the rise in OPs also results in an increased voltage undershoot/overshoot due to greater fluctuations in the membrane water content, ultimately leading to additional power loss. These findings are crucial for optimizing PEMFC performance under extreme conditions and advancing fuel cell technology.

Research on the strength influence and crack evolution law of layered backfill based on macro and meso mechanical response

This article analyzes the effects of inclined angle (IA), filling times (FTs) and cement tailings ratio (CTR) on the uniaxial compressive strength (UCS) and crack development law of layered cemented backfill (LCB) using various research methods, including indoor experiments, numerical simulation, and computed tomography (CT) scanning. The research shows: (1) In the indoor experiments, it was observed that increasing the IA, increasing the number of FTs, and decreasing the CTR had a significant weakening effect on the UCS of the specimens. The greater the IA, the more pronounced the separation and dislocation of the layered contact surface, resulting in a significant increase in macroscopic cracks at the bottom. As the FTs increases, the center of gravity of the failure of the LCB gradually moves downwards. This causes the damage and failure time to advance, and the peak stress to change from one main crack to multiple main cracks. (2) During the numerical simulation, compressive stress accumulates and increases around the pores in the layered contact surface. Microcrack aggregation occurs on the contact surface, and downward expansion and extension. The peak strain energy decreases as the IA increases with the FTs. The number of shear cracks increased more at 20° to 30° than at 0° to 20°. The strain energy of the 0° specimen is the highest, while that of the 30° specimen is the lowest. (3) The CT scan shows that the LCB is affected by stress conduction hysteresis. When the bottom backfill is in the stage of crack evolution, the top backfill is in the stage of compaction.When the LCB reaches the peak stress, both the bottom and middle layers of the backfill lose load-bearing capacity, and the top layer of the backfill has no cracks. This paper provides reference value and research ideas for the destruction of backfill that contain layered defective structures.

Electrical Tracking of the Mott Insulating Kitaev Magnet using Graphene/α‐RuCl3 Heterostructure

AbstractElectrical signatures for quantum magnetic phases of α‐RuCl3 sensed by an adjacent graphene field‐effect transistor (FET) are reported. The gate‐voltage dependence of the graphene FET reveals p‐type doping beneath α‐RuCl3 caused by the charge transfer due to the work function difference. Furthermore, the gate‐voltage hysteresis exhibits a marked change in the transport behavior with the temperature variation. The high‐T simple paramagnetic phase and the low‐T zigzag antiferromagnetic phase of α‐RuCl3 exhibit negligible hysteresis. In sharp contrast, a huge hysteresis of the graphene FET at intermediate temperatures is observed. The possibility that the observed conductance hysteresis is associated with the intriguing continuum excitations of the thermally induced Kitaev paramagnet state is discussed. The results show that the proximity effect‐based electric approach can be utilized for investigating charge‐neutral quasiparticles in quantum magnetic insulators.

Electrical, dielectric, and ferroelectric characteristics of Bi4Ti2.9Se0.1O12

The current communication addresses structural, impedance, conductivity, dielectric permittivity, tangent loss, and ferroelectric hysteresis of selenium doped bismuth titanate (Bi4Ti2.9Se0.1O12) synthesized by a solid-state reaction technique. XRD profile reveals the formation of orthorhombic unit cell structure (B2ab space group) in Bi4Ti2.9Se0.1O12. Partial doping of Se (10%) makes significant modifications in the electrical and dielectric characteristics, which are investigated over discrete frequencies (1 kHz–1 MHz) and temperatures (27–300 °C). The compound exhibits comparatively low value of the tangent loss at 1 MHz frequency. The ferroelectric hysteresis loop of the compound confirms the non-centrosymmetric arrangement of elements at room temperature, and the value of remanent polarization makes the compound suitable for memory applications.

Printed sustainable elastomeric conductor for soft electronics

The widespread adoption of renewable and sustainable elastomers in stretchable electronics has been impeded by challenges in their fabrication and lacklustre performance. Here, we realize a printed sustainable stretchable conductor with superior electrical performance by synthesizing sustainable and recyclable vegetable oil polyurethane (VegPU) elastomeric binder and developing a solution sintering method for their composites with Ag flakes. The binder impedes the propagation of cracks through its porous network, while the solution sintering reaction reduces the resistance increment upon stretching, resulting in high stretchability (350%), superior conductivity (12833 S cm−1), and low hysteresis (0.333) after 100% cyclic stretching. The sustainable conductor was used to print durable and stretchable impedance sensors for non-obstructive detection of fruit maturity in food sensing technology. The combination of sustainable materials and strategies for realizing high-performance stretchable conductors provides a roadmap for the development of sustainable stretchable electronics.

Production and Study of Electrical Characteristics for one of the Dual Estelline Polymers

This study involved the development of a poly-2,4-hexamine-1,5 diol. Conductivity mechanics were investigated by tracking voltage-current characteristics, conductivity (time-current), and conductor motion as a function of temperature between 313 and 353 ok. The principal slopes of (I-t) curves reveal that an increase in temperature results in a rise in conductivity and conductor-carrier mobility (mobility µ). In addition, the activation energy was determined to be 0.897 via a calculation based on the curve formed by (-1/T). Also, the hysteresis of electrical conductivity at different temperatures was studied while the voltage stayed the same.

Modulation of Voltage-Gating and Hysteresis of Lysenin Channels by Cu2+ Ions.

The intricate voltage regulation presented by lysenin channels reconstituted in artificial lipid membranes leads to a strong hysteresis in conductance, bistability, and memory. Prior investigations on lysenin channels indicate that the hysteresis is modulated by multivalent cations which are also capable of eliciting single-step conformational changes and transitions to stable closed or sub-conducting states. However, the influence on voltage regulation of Cu2+ ions, capable of completely closing the lysenin channels in a two-step process, was not sufficiently addressed. In this respect, we employed electrophysiology approaches to investigate the response of lysenin channels to variable voltage stimuli in the presence of small concentrations of Cu2+ ions. Our experimental results showed that the hysteretic behavior, recorded in response to variable voltage ramps, is accentuated in the presence of Cu2+ ions. Using simultaneous AC/DC stimulation, we were able to determine that Cu2+ prevents the reopening of channels previously closed by depolarizing potentials and the channels remain in the closed state even in the absence of a transmembrane voltage. In addition, we showed that Cu2+ addition reinstates the voltage gating and hysteretic behavior of lysenin channels reconstituted in neutral lipid membranes in which lysenin channels lose their voltage-regulating properties. In the presence of Cu2+ ions, lysenin not only regained the voltage gating but also behaved like a long-term molecular memory controlled by electrical potentials.

A Low‐Hysteresis and Highly Stretchable Ionogel Enabled by Well Dispersed Slidable Cross‐Linker for Rapid Human‐Machine Interaction

AbstractIonic conductive soft materials for mimicking human skin are a promising topic since they can be thought of as a possible basis for biomimetic sensing. In pursuit of devices with a long working range and low signal delay, conductive materials with low hysteresis and good stretchability are highly demanded. To overcome the challenges of highly stretchable conductive materials with good resilience, herein a chemical design is proposed where polyrotaxanes act as topological cross‐linkers to enhance the stretchability by sliding‐induced reduced stress concentration while the compatible ionic liquid is introduced as a dispersant for low hysteresis. The obtained ionogels exhibit versatile properties more than low hysteresis (residual strain = 7%) and good stretchability (550%), and also anti‐fatigue, biocompatibility, and good adhesion. The low hysteresis is attributed to lower energy dissipation from the well‐dispersed polyrotaxanes by compatible ionic liquids. The mechanism provides a new insight in fabricating highly stretchable and low‐hysteresis slide‐ring materials. Furthermore, the conductivity of the ionogels and their responses to strains and temperatures are measured. Benefiting from the good conductivity and low hysteresis, the ionogel is applied to develop a wireless communication system to realize rapid human‐machine interactions.

Electromagnetic absorption behavior regulation in bimetallic polyphthalocyanine derived CoFe-alloy/C 0D/2D nanocomposites

Efficient tuning of electrical and magnetic property of a material is of great importance in its functional material design, mechanism understanding, and application expanding. In this work, we propose an efficient strategy for the electromagnetic absorption (EMA) behavior regulation of bimetallic polyphthalocyanine (PPc) derived CoFe-alloy/C nanocomposites. Through the adjusting of calcination temperature and Fe/Co atomic ratio, the microstructure (0D/2D nanocomposite), electrical conductivity, magnetic property, and EMA behavior can be efficiently tuned. After optimization, the efficient absorption bandwidth of CoFe-alloy/C achieves 7.64 GHz, while the maximal absorption gets close to −60 dB, exhibiting superiority to most reported carbon related materials. It is thought that the absorbing mechanism of CoFe-alloy/C is mainly ascribed to the combination of conductance loss, multiple polarization, resonance phenomenon, and hysteresis loss. This research greatly expands the application scope of PPc derivatives, and provides an efficient way to understand the interaction between material and electromagnetic waves.

BaTiO3/NixZn1−xFe2O4 (x = 0, 0.5, 1) Composites Synthesized by Thermal Decomposition: Magnetic, Dielectric and Ferroelectric Properties

To investigate the influence of spinel structure and sintering temperature on the functional properties of BaTiO3/NixZn1−xFe2O4 (x = 0, 0.5, 1), NiFe2O4, ZnFe2O4, and Ni0.5Zn0.5Fe2O4 were in situ prepared by thermal decomposition onto BaTiO3 surface from acetylacetonate precursors. As-prepared powders were additionally sintered at 1150 °C and 1300 °C. X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) coupled with electron dispersive spectroscopy (EDS) were used for the detailed examination of phase composition and morphology. The magnetic, dielectric, and ferroelectric properties were investigated. The optimal phase composition in the BaTiO3/NiFe2O4 composite, sintered at 1150 °C, resulted in a wide frequency range stability. Additionally, particular phase composition indicates favorable properties such as low conductivity and ideal-like hysteresis loop behavior. The favorable properties of BaTiO3/NiFe2O4 make this particular composite an ideal material choice for further studies on applications of multi-ferroic devices.

Quantification of solute transport in a fracture-matrix system using geoelectrical monitoring

Solute transport in fracture is easy to diffuse into the matrix due to the permeability of the matrix. The quantification of solute concentration is particularly important during diffusion and is a challenge for the management of pollutants in a fracture-matrix system. In this paper, sodium chloride as solute, the geoelectrical technology was combined with high density electrical method and conductivity acquisition method to conduct a series of sandbox experiments. In the center of the sandbox is a fracture, and on both sides of the fracture is the matrix. The fracture and matrix in the sandbox form a fracture-matrix system. Loading-flushing process of sodium chloride solution in fracture-matrix system was monitored in real-time and non-destructive. The effect of matrix porosity and flow velocity on solute transport in fracture-matrix system was investigated. The results showed that: 1) Mass transfer rate coefficient (α) and fracture/matrix porosity ratio (β), and tailing exponent of residence time distribution (ω) were quantified by pairing bulk electrical conductivity (BEC) and fluid electrical conductivity (FEC), without the requirement of inverse model calibration. In contrast, the single electrical method still lacks resolution or is not representative in determining solute transport parameters in fracture-matrix system. 2) The matrix porosity had a significant effect on solute transport in fracture-matrix system. With the increase of porosity, the mass transfer rate coefficient (α) increased and the residence time in the matrix decreased. 3) An increase of flow velocity led to a decrease of residence time in the matrix and an increase in mass transfer rate coefficient (α). The solute transport in fracture-matrix system can be quantified by electrical conductivity hysteresis. The results can provide a basis for the management of solute transport in fracture-matrix system

Precise Drift Tracking for In Situ Transmission Electron Microscopy via a Thon-Ring Based Sample Position Measurement.

Visualizing how a catalyst behaves during chemical reactions using in situ transmission electron microscopy (TEM) is crucial for understanding the activity origin and guiding performance optimization. However, the sample drifts as temperature changes during in situ reaction, which weakens the resolution and stability of TEM imaging, blocks insights into the dynamic details of catalytic reaction. Herein, a Thon-ring based sample position measurement (TSPM) was developed to track the sample height variation during in situ TEM observation. Drifting characteristics for three commercially available nanochips were studied, showing large biases in aspects of shifting modes, expansion heights, as well as the thermal conduction hysteresis during rapid heating. Particularly, utilizing the TSPM method, for the first time, the gas layer thickness inside a gas-cell nanoreactor was precisely determined, which varies with reaction temperature and gas pressure in a linear manner with coefficients of ~8 nm/°C and ~50 nm/mbar, respectively. Following drift prediction of TSPM, fast oxidation kinetics of a Ni particle was tracked in real time for 12 s at 500°C. This TSPM method is expected to facilitate the functionality of automatic target tracing for in situ microscopy applications when feedback to hardware control of the microscope.

Magnetic field-driven particle assembly and jamming for bistable memory and response plasticity.

Unlike classic synthetic stimulus-responsive and shape-memory materials, which remain limited to fixed responses, the responses of living systems dynamically adapt based on the repetition, intensity, and history of stimuli. Such plasticity is ubiquitous in biology, which is profoundly linked to memory and learning. Concepts thereof are searched for rudimentary forms of "intelligent materials." Here, we show plasticity of electroconductivity in soft ferromagnetic nickel colloidal supraparticles with spiny surfaces, assembling/disassembling to granular conducting micropillars between two electrodes driven by magnetic field B. Colloidal jamming leads to conduction hysteresis and bistable memory upon increasing and subsequently decreasing B. Abrupt B changes induce larger conduction changes than gradual B-changes. Periodic B pulsing drives to frequency-dependent facilitation or suppression of conductivity compared to exposing the same constant field. The concepts allow remotely controlled switching plasticity, illustrated by a rudimentary device. More generally, we foresee adaptive functional materials inspired by response plasticity and learning.

Maple Leaf Inspired Conductive Fiber with Hierarchical Wrinkles for Highly Stretchable and Integratable Electronics.

Stretchable and durable conductors are significant to the development of wearable devices, robots, human-machine interfaces, and other artificial intelligence products. However, the desirable strain-insensitive conductivity and low hysteresis are restricted by the failure of stretchable structures and mismatch of mechanical properties (rigid conductive layer and elastic core substrate) under large deformation. Here, based on the principles of fractal geometry, a stretchable conductive fiber with hierarchical wrinkles inspired by the unique shape of the maple leaf was fabricated by combining surface modification, interfacial polymerization, and improved prestrain finishing methods to break through this dilemma. The shape and size of wrinkles predicted by buckling analysis via the finite element method fit well with that of actual wrinkles (30-80 μm of macro wrinkles and 4-6 μm of micro wrinkles) on the fabricated fiber. Such hierarchically wrinkled conductive fiber (HWCF) exhibited not only excellent strain-insensitive conductivity denoted by the relative resistance change ΔR/R0 = 0.66 with R0 the original resistance and ΔR the change of resistance after the concrete strain reaching up to 600%, but also low hysteresis (0.04) calculated by the difference in area between stretching and releasing curve of the ΔR/R0 strain under 300% strain and long-term durability (>1000 stretching-releasing cycles). Furthermore, the elastic conductive fiber with such a bionic structure design can be applied as highly stretchable electrical circuits for illumination and monitors for the human motion under large strains through tiny and rapid resistance changes as well. Such a smart biomimetic material holds great prospects in the field of stretchable electronics.

High temperature ionic and electronic conductivity in MgPSZ

The high temperature ionic (σi) and n-type electronic conductivity (σn) of 7.5 mol% MgO-doped partially stabilized ZrO2 (7.5MgPSZ) were determined using 4 probe total conductivity (in air, 800–1600 °C), and oxygen concentration cell open circuit voltage measurements (1200–1600 °C). The latter involved two distinct cell configurations (Al or Cr-based electrodes versus air). The σn values of 4.78 × 10−4 S.cm−1 at 1600 °C (extrapolated to pO2 = 1 atm) and activation energy of 424.0 kJ.mol−1 are hereby reported for the first time. The observed ionic conductivity of 0.60 S.cm−1 at 1600 °C and activation enthalpy of 119.5 kJ.mol−1 for the 1400–1600 °C temperature range are both within upper ranges reported for other PSZ materials. This high activation enthalpy suggests a strong defect association between oxide-ion vacancies and acceptor dopant, exceeding typical values observed with trivalent dopants. The reasons for wide literature data ranges on ionic transport are discussed taking into consideration the variable phase content, phase composition, and potential non-equilibrium conditions observed in experiments. The specific case of hysteresis in conductivity versus temperature curves is analyzed in detail. Complementary structural and microstructural characterization, besides thermal expansion behavior, are used to support the analysis of electrochemical performance.

Gate-Tunable Magnetism and Giant Magnetoresistance in Suspended Rhombohedral-Stacked Few-Layer Graphene.

Conventionally, magnetism arises from the strong exchange interaction among the magnetic moments of d- or f-shell electrons. It can also emerge in perfect lattices from nonmagnetic elements, such as that exemplified by the Stoner criterion. Here we report tunable magnetism in suspended rhombohedral-stacked few-layer graphene (r-FLG) devices with flat bands. At small doping levels (n ∼ 1011 cm-2), we observe prominent conductance hysteresis and giant magnetoconductance that exceeds 1000% as a function of magnetic fields. Both phenomena are tunable by density and temperature and disappear at n > 1012 cm-2 or T > 5 K. These results are confirmed by first-principles calculations, which indicate the formation of a half-metallic state in doped r-FLG, in which the magnetization is tunable by electric field. Our combined experimental and theoretical work demonstrate that magnetism and spin polarization, arising from the strong electronic interactions in flat bands, emerge in a system composed entirely of carbon atoms.

Salinity and sodicity can cause hysteresis in soil hydraulic conductivity

Soil salinization and sodification can cause severe damage to soil structure, with important implications for irrigated agriculture. Knowledge of the extent to which degradation in soil structure due to salinization and sodification is reversible, however, is still lacking. The objective of our study is to examine how the history of solute composition affects the degree of reversibility in saturated hydraulic conductivity (Ksat). We systematically investigate the effects of salinity (electrolyte concentration) and sodicity (sodium adsorption ratio) on Ksat, for three soils of varying clay content. The soil column experiments yielded hysteresis graphs, in which Ksat does not go back to its original value after initial decay. We developed indices to quantify the degree of Ksat degradation and reversibility, and found that contrary to our expectations, high susceptibility to degradation does not always correlate with low capability to rehabilitate. Measurements of soil swelling helped us discern when degradation was mainly caused by swelling or clay dispersion. Our findings underscore the need for understanding hysteresis caused by salinity and sodicity, aiming at better management of agricultural soils for sustainable long-term use.

Diurnal and seasonal dynamics of the electrical conductivity of water of the northeastern part of the Great Vasyugan Mire (Western Siberia)

In this study, we determined the diurnal and seasonal dynamics of the electrical conductivity of waters of the northeastern part of the Great Vasyugan Mire in Western Siberia. Our studies showed that the electrical conductivity of the waters for the period of April to September 2016 was characterised by a value of 35 μS/cm, and the seasonal amplitude was 25 μS/cm. In seasonal dynamics, there are three maximums of electrical conductivity in waters. The first maximum was formed in April (48 μS/cm) and is associated with snowmelt water supply. The second one was observed in May after the complete thawing of the peat deposit (39 μS/cm), and the third was observed at the end of July as a result of biochemical processes in the peat deposit (43 μS/cm). Our studies have shown the electrical conductivity hysteresis during time intervals from 3–5 to 6–10 days electrical conductivity remains constant despite the change in hydrometeorological conditions (water table level, temperature).

Solvent-free adhesive ionic elastomer for multifunctional stretchable electronics

Intrinsically stretchable and transparent ionic conductors are of great interest due to their promising applications in flexible and wearable electronics. However, hydrogels/organogels based devices suffer from instability due to liquid evaporation or leakage. Herein, we present a solvent-free ionic elastomer (IE), featuring high transparency (>92%), stretchability (300%), ionic conductivity (0.07 mS/cm), adhesiveness (61 N/m), thermal stability (300 °C), and negligible mechanical hysteresis, which endows implementation capacity in multifunctional stretchable electronics. The IE-based robust strain sensors (both resistive and capacitive) show linear sensitivities in the range of 0–150% strain and long-term stability. Moreover, a reversible wide-range temperature sensor is presented showing remarkable sensitivity in the range of 30–55 °C sustained under 50% stretching. The temperature-strain effect on the IE-based sensor is insignificant, ensuring an accurate sensing capability. Thanks to its self-adhesiveness, a fully integrated, stretchable motion energy harvester as well as a skin-like thin triboelectric sensor array using IE as the electrode are further designed to demonstrate efficient human motion energy harvesting with a peak power density of 3.6 W/m2 and self-powered tactile sensing. The results provide strategies towards potential applications of developed IE in healthcare monitoring systems, biomechanical energy harvesting, soft robotics, and human-machine interfaces.

Numerical evaluation of the effects of asymmetric membrane heat conductivity and moisture adsorption hysteresis on the performance of air-to-air membrane enthalpy exchanger

Effects of tangential heat conduction and moisture adsorption hysteresis of the membrane on the heat recovery performance of cross-flow and counter-flow membrane enthalpy exchangers are investigated numerically. The accuracy of the numerical simulation model is evaluated by predicting an experimental case and a reasonable accuracy is achieved. It is found that the temperature profile at the membrane surface is significantly influenced by the tangential heat conduction in the membrane. The variation of temperature profile at the membrane surface results in variations of the convective heat resistance and the sensible heat effectiveness. Simulation results demonstrate that the sensible heat effectiveness firstly increases and then decreases with the increasing membrane heat conductivity. The optimal membrane heat conductivity is about 0.1 ∼ 1 W m−1 K−1. Two types of the moisture adsorption hysteresis are assumed and expressed by simple expressions. It is found that the moisture adsorption hysteresis decreases the moisture diffusion flux across the membrane and accordingly decreases the latent heat effectiveness obviously for both counter-flow and cross-flow patterns. Current results indicate that membranes with large heat conductivity are not beneficial for sensible heat recovery and membranes with small adsorption hysteresis are beneficial for latent heat recovery.