Internal Polarization Research Articles

Intercalation-Induced Interlayer and Defect Engineering in Ti3C2Tx MXene for Ultralow-Reflection Electromagnetic Interference Shielding.

Interlayer and defect engineering significantly affects the electrical conductivity and electromagnetic interference (EMI) shielding of Ti3C2Tx MXene. Previous studies have prioritized the size of the intercalant over its synergy with chemical affinity, limiting the elucidation of the intercalation mechanism and the precise control of the interlayer spacing (d-spacing). Herein, we synthesize MXene aerogels with a tunable d-spacing and defect density using a series of amine molecules of different sizes and chemical affinities as intercalants and cross-linkers. Particularly, the intercalation of p-phenylenediamine (PPD) increases the d-spacing of MXene from 0.960 to 1.642 nm. Simultaneously, the increased d-spacing contributes to an increased defect density within the Ti-Ti layer. Hence, the PPD@MXene aerogel exhibits reduced surface electric field intensity and increased internal polarization loss, resulting in absorption-dominated EMI shielding. The absorptivity reaches 0.92, far exceeding the reported shielding materials, with a shielding effectiveness of 50.4 dB. This study provides a theoretical foundation and preliminary guidance for the development of interlayer-engineered MXene shielding materials.

In situ surface oxygen vacancy effect synergistic with internal polarization effect in BiFeO3 for photoelectrochemical detection of T4 DNA ligase

In situ surface oxygen vacancy effect synergistic with internal polarization effect in BiFeO3 for photoelectrochemical detection of T4 DNA ligase

A reversible positive and negative photoconductivity behavior modulated by polarization effect

Negative photoconductive devices exhibit a significant reduction in conductivity under illumination, enabling high-contrast optical modulation and promising great potential in optics. In this study, an ITO/BFCO/TiO2/FTO device was simply fabricated through a synergistic application of sol-gel and magnetron sputtering techniques. Interestingly, the ferroelectric polarization can be reversibly modulated by a low bias voltage in the ITO/BFCO/TiO2/FTO device, thereby exhibiting bipolar voltage dependent reversible behavior of positive and negative photoconductivity. This mechanism has been discussed, where the combined effect of illumination and applied voltage induces internal polarization reversal in Bi2FeCrO6, leading to a transition in the resistance state from low to high. This transition results in an elevation of the energy band, thereby impeding the migration of charge carriers. Additionally, femtosecond laser transient absorption spectroscopy reveals redshift in the initial absorption peak, indicating changes in the band structure induced by illumination, crucial for understanding carrier dynamics in a non-equilibrium state.

Thermoelastic polarization and other effects in polar semiconductors

Electrical polarization and associated effects are now gaining importance for electronics due to growing application of wide-bandgap polar semiconductors such as gallium arsenide and gallium nitride. The internal polarity of the structure of such semiconductors has significant impact on millimeter wave losses as well as on the technological features and application of electronic devices based on polar semiconductors. It has been shown that any piezoelectric has an intra-crystalline polar moment, even if the piezoelectric crystal does not belong to the pyroelectric symmetry. A new effect of thermoelastic polarization in polar-neutral crystals is described and a number of possibilities for its implementation are discussed. The experimental study of the internal polarity in piezoelectrics is provided by the partial limitation of thermal strain method. It is believed that thermoelastic polarization must be taken into account in the technology of polar semiconductors as enabling creation of integrated sensors based on them.

Asymmetric linear conjugated polymers for stable H2O2 photosynthesis via internal polarization

Asymmetric linear conjugated polymers for stable H2O2 photosynthesis via internal polarization

Effects of Preparation Conditions on Performance of PES:PEG Flat Sheet Membrane for MG Dye Separation

This study deals with the morphology and performance properties of a novel thin flat sheet ultrafiltration membrane; Malachite Green (MG) dye filtration behavior was evaluated in the cross-flow filtration system. The prepared membranes included the incorporation of 16 wt. % of polyether sulfone (PES)/DMF and 5 wt.% of Polyethylene Glycol (PEG) via the phase inversion process. Adding PEG decreased the internal concentration polarization, improved the membrane hydrophilicity, changed pore morphologies, and enhanced membrane performance. The SEM and AFM tests were used to characterize the composition and structure of the membrane. With different casting conditions, the membrane shape changed. The effect of membrane thickness (100, 150, and 200) µm and coagulation bath properties temperature (15, 25, and 35) °C and composition DMF (10, 20, 30 %) in water on the fabricated membrane were investigated. To evaluate the membrane filtration performance, the fabricated membranes were applied in an ultrafiltration system to treat Malachite Green dye solution at a concentration of (10 ppm) as a model pollutant. Based on the obtained results, the ideal membrane parameters were150 µm in thickness, 35°C in temperature, and 10% in composition DMF; the removal efficiency was observed to be (94.5%, 93%, and 99.5%) while the permeate flux (45, 35 and 30) LMH, respectively.

MoS2 loaded cotton stalk based porous carbon with high N content improves the electrochemical performance of Li[sbnd]S batteries

The high-performance composite material of C/S with N-doping and MoS2 loaded is prepared using cotton stalks as precursors. The intrinsic mechanism of N doping and loaded MoS2 for improving battery performance was investigated. Both addition of N and MoS2 can increase the graphitization degree, reducing the specific surface area and pore volume of porous carbon. The combination of both has a synergistic effect on enhancing the graphitization degree and increasing the content of N and MoS2 in porous carbon. However, it also demonstrates a stronger inhibition for the specific surface area and pore volume by limiting the development of pore structure below 10 nm. In terms of electrochemical performance, co-addition of N and MoS2 can better improve the electrochemical performance, which further reduce the internal polarization and increase the diffusion rate of lithium ions. The specific capacity was retained of 694.8 mAhg−1 after 100 cycles at 0.5C, which increase 43.08 % and 27.60 % compared with single N doping and loaded MoS2, respectively. Even at a high current of 2C, it still shows a high specific capacity of 719.6 mAhg−1. By characterization the cathode after the cycle test completed, the porous carbon prepared by co-addition of N and MoS2 has higher catalytic activity for the conversion of polysulfide. Higher content of N and MoS2 and excellent degree of graphitization in porous carbon after co-addition are key factors for improved performance.

Analysis on Electrocaloric Effect in (Ba, Sr)TiO3 Ferroelectrics Near Phase Transition Temperature

In recent years, there has been attention towards cooling systems utilizing the electrocaloric effect (ECE) as micro-cooling elements in small electronic devices such as smartphones. ECE is the phenomenon where the internal polarization structure of a material changes due to the application or removal of an electric field, resulting in a change in entropy and thus delivering absorption or generation of heat. As ECE is driven via utilizing the external electric field, it exhibits high compatibility with electronic devices owing to lower power consumption rather than the electric current driven applications.There are various dielectric materials that can be utilized for ECE. Commonly used ferroelectrics include macro-domain types, where domain walls with aligned spontaneous polarization generate dielectric properties through their vibrations, and relaxor types, where Polar Nanoregions (PNRs) with alignment of polarization in several unit cells exhibit dielectric properties through oscillations induced by an external electric field. The entropy variation in these mentioned polarizations under an external electric field delivers the temperature change, owing to the Maxwell's relation.ECE in ferroelectrics is known to be maximized near the phase transition temperature (Curie temperature, T c) and the dielectric maximum temperature (T m) [1]. Considering the Maxwell's relation,ΔT due to the electrocaloric effect (ECE), the contributions to ΔT through the polarization P can be interpreted as the combination of two contributions; the growingpolarization represented by dielectric permittivity and the spontaneous polarization (P bias). The former is expected to reflect the effect of the polarization structure. However, these contributions have not been quantified separately. In order to elucidate the mechanism, i.e., the reason for the ECE anomaly at the T c and the T m, the mentioned ΔP contributions need to be separately analyzed. In this study, we performed the direct and indirect ECE measurements and analyzed the two contributions. For the directmeasurement, we utilized the lock-in thermography technique which enables the accurate temperature change under a ac field [2]. The indirect measurement was performed by analyzing the temperature-dependences of the dielectric permittivity and the spontaneous polarization acquired from the electric field-polarization measurement simultaneously performed with the direct measurement. For the evaluation in this study, we employed the (Ba,Sr)TiO3 based ferroelectric materials exhibiting a relatively high ECE. The directly evaluatedΔ T of the BST exhibited its maximum near the T c as expected. The analysis showed that in a low electric field region, the factor determining the Δ T is the temperature dependence of the spontaneous polarization, which can be found fromthe peak temperature of differentiation P bias. In contrast, with increasing the electric field, the contribution of dielectric permittivity to the Δ T is increased, which shifts the peak temperature of ECE to a higher temperature.This analysis can be utilized to a variety of the ECE materials, yielding to the quantitative understanding of the each contribution (P bias and dielectric constant) to the apparentΔ T under a dc field.AcknowledgementThe authors are grateful to Prof. Ken-ichi Uchida for providing a series of the facility and the equipment related to the direct ECE measurement.[1] J.Li et al. J. Phys. Energy 5 , 2023, 024017[2] Ryo Iguchi et al. Appl. Phys. Lett. 122, 2023, 082903

Tocqueville and Democratic Historical Consciousness

ABSTRACT This article assesses to what extent the future of democratic liberty depends upon its citizens employing a proper approach to the past, by analyzing Tocqueville’s views of three kinds of historical consciousness—aristocratic, revolutionary, and democratic. It is argued that democracies require certain aristocratic assumptions about historical dynamics to cultivate a historical consciousness that fosters liberty. Key to this is the belief in the human capacity to influence the trajectory of history. Tocqueville’s historical approach, which blends aristocratic and democratic elements, is identified as the most effective method for tempering the fatalistic tendencies of the democratic point of view. Thus, for democracies to maintain liberty, citizens should recognize the dual role of general causes and human agency in directing the course of historical events. Tocqueville’s insights on the effects of historical consciousness on the future of democratic liberty remain particularly relevant today when Western democracies confront internal polarization and external anti-democratic challenges, whether neoliberal, illiberal, populist, or fascist.

A Piezocatalysis Strategy to Enable Efficient Redox in Solid‐State Battery

AbstractPiezocatalysis is considered to be a favorable catalytic technology by utilizing external mechanical stimulation to promote the specific redox reactions. The application of piezocatalysis in batteries is promising but faces formidable challenges. Herein, the operation principles of piezocatalysis were successfully demonstrated by constructing solid‐state Li−Se and Li−S battery models with interfacial stress accumulation. Lead zirconate titanate with an ultra‐high piezoelectric coefficient was applied as the piezoelectric catalyst. The uniformity of the dipole orientation in materials was essential for achieving piezocatalysis in batteries. The accumulated high‐stress converts to piezopotential for catalyzing most reaction processes in batteries, while the rapid stress change prevents the internal charge reorganization, ensuring continuous efficient catalysis. The internal stress change alters the internal polarisation strength, driving excess screening charge to participate in the electrochemical reaction. Under piezocatalysis, solid‐state Li−Se batteries exhibited a initial discharge capacity of 670.9 mAh g−1 (99.4 % of the theoretical value) at 0.1 C, and Li−S batteries showed a capacity of 1463 mAh g−1 at 0.2 C, which was still maintained up to 1084 mAh g−1 at an elevated rate of 0.5 C. This piezocatalysis strategy provides a strong theoretical basis and design specification for enhancing Li−Se and Li−S battery reaction kinetics.

A Piezocatalysis Strategy to Enable Efficient Redox in Solid-State Battery.

Piezocatalysis is considered to be a favorable catalytic technology by utilizing external mechanical stimulation to promote the specific redox reactions. The application of piezocatalysis in batteries is promising but faces formidable challenges. Herein, the operation principles of piezocatalysis were successfully demonstrated by constructing solid-state Li-Se and Li-S battery models with interfacial stress accumulation. Lead zirconate titanate with an ultra-high piezoelectric coefficient was applied as the piezoelectric catalyst. The uniformity of the dipole orientation in materials was essential for achieving piezocatalysis in batteries. The accumulated high-stress converts to piezopotential for catalyzing most reaction processes in batteries, while the rapid stress change prevents the internal charge reorganization, ensuring continuous efficient catalysis. The internal stress change alters the internal polarisation strength, driving excess screening charge to participate in the electrochemical reaction. Under piezocatalysis, solid-state Li-Se batteries exhibited a initial discharge capacity of 670.9 mAh g-1 (99.4 % of the theoretical value) at 0.1 C, and Li-S batteries showed a capacity of 1463 mAh g-1 at 0.2 C, which was still maintained up to 1084 mAh g-1 at an elevated rate of 0.5 C. This piezocatalysis strategy provides a strong theoretical basis and design specification for enhancing Li-Se and Li-S battery reaction kinetics.

Energy harvesting through the triboelectric nanogenerator (TENG) based on polyurethane/cellulose nanocrystal

This study investigates how physical and mechanical properties affect the performance of triboelectric nanogenerators (TENGs). Polyurethane (PU) was prepared using two methods: (i) one-step PU (non-chain extended polyurethane) and (ii) two-step PU (chain extended polyurethane) via the prepolymer method; both types were filled with different concentrations of nanocrystalline cellulose. Mechanical properties significantly influence the deformation at the material interface that occurs during contact or friction. Key surface characteristics, including surface energy, geometry, and physicochemical properties, affect the effective contact area and potential distribution. One-step PU with 0.1 % CNC demonstrates a maximum capacitance of 29.20 pF, a voltage of 2.04 V, an electric current of 0.43 µA and power of 0.89 µW, representing a 74.5 % increase in power compared to the neat one-step PU, exhibits significant potential for TENG applications. Performance improvements are associated with lower concentrations of cellulose nanocrystals, enhanced hydrogen bonding, and beneficial surface energy. The observed enhancements in output are attributed to improved internal polarization from well-dispersed crystalline nanocellulose, increased crystallinity of the soft segment, and reduced charge transfer mechanisms due to amino groups in the chain extender. However, the impact of the molecular structure and conformation of polyurethanes on triboelectrification remains unclear, highlighting the need for theoretical models and experimental data. This research provides a practical approach for developing stretchable triboelectric materials with enhanced mechanical properties, emphasizing the importance of considering factors such as mechanical parameters, nanofiller content, and surface physicochemical properties to optimize TENG design.

Large internal stress induced nonlinear current-voltage behavior in nanodiamond strengthened ZnO ceramics

The modulation of the electrostatic potential barrier at grain boundaries determines the performance of many ceramic-based electronics such as varistors. However, conventional protocols relying on complex doping and annealing processes inevitably increase the inhomogeneity of microstructure, which may jeopardize the performance stability and mechanical reliability in service. Instead of doping, herein we demonstrate an effective strategy to modulate the potential barrier in ZnO-based low-voltage varistors by exploiting internal stress-induced piezoelectric polarization. The local residual stress as large as ~1 GPa can be created in the ZnO matrix by incorporating ultra-stiff nanodiamond particles using a cold sintering process. As a result, the composite with only 2 wt% of nanodiamond exhibits a prominent nonlinear current-voltage response at a low switch voltage of 15.7 V/mm, which is ascribed to the depressed barrier height induced by the distinct effects of positively and negatively charged polarization on grain boundaries. More strikingly, the large internal stress can significantly enhance the strength of the composite by more than 230% compared with the monolith, owing to the highly strengthened grain boundaries and crack-tip bridging from prestressed nanodiamonds. These findings add internal stress as a new dimension to design mechanically robust ceramic electronics with high performance.

Computational Fluid Dynamics Modeling of Pressure-Retarded Osmosis: Towards a Virtual Lab for Osmotic-Driven Process Simulations.

Pressure-Retarded Osmosis (PRO) is an osmotically driven membrane-based process that has recently garnered significant attention from researchers due to its potential for clean energy harvesting from salinity gradients. The complex interactions between mixed-mode channel flows and osmotic fluxes in real PRO membrane modules necessitate high-fidelity modeling approaches. In this work, an efficient CFD framework is developed for the 3D simulation of osmotically driven membrane processes. This approach is based on a two-way coupling between a CFD solver, which captures external concentration polarization (ECP) effects, and an analytical representation of internal concentration polarization (ICP). Consequently, the osmotic water flux and reverse salt flux (RSF) can be accurately determined, accounting for all CP effects without any limitations on the geometrical complexity of the membrane chamber or its flow mode/regime. The proposed model is validated against experimental data, showing good agreement across various PRO case studies. Additionally, the model's flexibility to simulate other types of osmotically driven processes such as forward osmosis (FO) is examined. Thus, the contributions of ECP and ICP effects in local osmotic pressure drop along the membrane chamber are comprehensively compared for FO and PRO modes. Finally, the capability of the CFD model to simulate a lab-scale PRO module is demonstrated across a range of Reynolds numbers from low-speed laminar up to turbulent flow regimes.

A high performance of thin film composite based on dextran substrate for effective removal of heavy metal ions

A high performance thin film composite forward osmosis (FO) membrane with dextran as additive in support layer has been developed for effective heavy metal ions removal for the first time. The proposed FO process consists of a thin film composite (TFC) FO membrane made from interfacial polymerization on a high porous and hydrophillic polysulfone embedded dextran support to minimize the internal concentration polarization effect. The created substrates were characterized in terms of surface chemistry and morphology prior to performance evaluation. The support layer incorporating with dextran exhibited lower contact angle and high porosity as an ideal support layer for FO process. Moreover, the ridge-and-valley structure of TFC membranes made with support layers containing larger openings, long finger-like voids and macrovoids was more noticeable for the active layers, according to high-resolution scanning electron microscopy. The removal of metals were demonstrated, water fluxes were around 13 L/m2.h and rejection were above 95 %. The performance of developed membrane was then showed greater water flux and rejection in comparison to the commercial TFC.

The Internal Socio-Economic Polarization of Urban Neighborhoods: The Case of the Municipality of Nice

In continuity with the research on social segregation and the phenomenon of urban gentrification, this article examines the cohabitation patterns of populations with diametrically opposed incomes within the same neighborhood, typically observed in the city center. This phenomenon is defined here as internal socio-economic polarization. It is measured through the combination of two original indexes (poverty and wealth indexes) constructed based on income deciles per consumption unit for the year of 2017. The analysis focuses on the municipality of Nice, characterized by a low demographic dynamic, a relative concentration of seniors, and a strong tourist attractiveness, particularly in the highly polarized neighborhoods that occupy almost the entire city center. This study is complemented by a principal component analysis summarizing the characteristics of the population and housing stock in the neighborhoods of Nice. The main objective of this research is to identify and locate polarized neighborhoods within the urban context of Nice, to analyze the distinctive traits of their population and housing stock, and, finally, to highlight potential trends in the population’s socio-economic status. Moreover, the economic trajectories of polarized neighborhoods, in connection with their population and housing characteristics (such as the secondary use of a portion of the housing stock, often low-quality old buildings, social housing, and the overrepresentation of retirees), help explain the forms of socio-economic polarization observed in these neighborhoods (such as the indications of gentrification, unfinished gentrification, and sustainable cohabitation).

Broad spectrum catalysis using Ca3Sn2S7 Ruddlesden-Popper perovskite under multi-stimulus

Advanced oxidation processes emerged as effective alternatives to traditional approaches. The efficacy of these methods significantly depends on the intrinsic properties of a catalyst material. Semiconductor materials with robust photo absorption alongside inherent polarization emerged as subjects of great interest. In this study, we synthesized two-dimensional Ca3Sn2S7 nanosheets oriented as Ruddlesden-Popper type perovskite structure. The optimal compositions of these nanosheets exhibit excellent physical and optical characteristics while varying Sn ratios significantly impact the properties. Impressively, these compositions boast a wide optical window that spans from the visible to the far infrared region, featuring a narrow bandgap of approximately 0.6 eV. Band potentials in a positive regime make it highly favorable for the oxidation process. The electrochemical analysis further validates high mobility with low resistance in both compositions. The catalytic efficiency of the synthesized nanosheets is evaluated using rhodamine-B. Three energy sources, i.e., visible light, laser, and ultrasound vibrations, decomposed 96 %, 90 %, and 78 %, respectively, in 30 min. Remarkably accelerated degradation rates are achieved under each stimulus, owing to the presence of oxidative optical bands, large surface area, and potential internal polarization within the nanosheets. Preliminary findings strongly indicate the immense potential of this compound in catalytic and photovoltaic applications.

Impact of Asymmetric Microstructure on Ion Transport in Ti3C2Tx Membranes.

Consolidation or densification of low-dimensional MXene materials into membranes can result in the formation of asymmetric membrane structures. Nanostructural (short-range) and microstructural (long-range) heterogeneity can influence mass transport and separation mechanisms. Short-range structural dynamics include the presence of water confined between the 2D layers, while long-range structural properties include the formation of defects, micropores, and mesopores. Herein, it is demonstrated that structural heterogeneity in Ti3C2Tx membranes fabricated via vacuum-assisted filtration significantly affects ion transport. Higher ion permeabilities are achieved when the dense "bottom" side of the membrane, rather than the porous "top" side, faces the feed solution. Characterization of the membrane reveals distinct differences in flake alignment, surface roughness, and porosity across the membrane. The directional dependence on permeability suggests that one region of the membrane experiences stronger internal concentration polarization, potentially suppressing permeability through the porous side of the membrane.

Challenges of forward osmosis desalination processes using hydrogels as draw agents

The present study aims to investigate the properties, identification, and comprehension of the obstacles encountered in the forward osmosis process when utilizing a hydrogel drawing agent (FO-HG). Furthermore, a comparison is made between the FO-HG system and conventional forward osmosis systems employing a salt solution drawing agent. The comparison and evaluation of the swelling process of hydrogel and the kinetics of water penetration are conducted in both un-constrained and constrained states. Furthermore, the investigation and analysis are carried out to determine the presence or absence of internal concentration polarization (ICP) and external concentration polarization (ECP) phenomena. These phenomena are studied in situations with and without mixing, as well as in different orientations of the membrane (FO-mode and PRO-mode). The impact of these phenomena on the water flux of the systems FO-HG and FO-NaCl is also examined. An evaluation is conducted to determine the influence of the amount and size of hydrogel used as a draw agent in the FO-HG system on the water flux. The results of the study reveal that smaller hydrogel particles in the FO-HG system exhibit a higher flux compared to larger particles. Additionally, it is observed that the water flux in PRO-mode is unexpectedly higher when salt water is used as feed solution. This phenomenon can be ascribed to a counter-osmotic effect, originating from the FO state. Despite the high water absorption capacity of hydrogel and its potential as an ideal drawing agent in the forward osmosis process, the results demonstrate that the flux of the FO-HG system is inferior to that of the FO-NaCl system. Finally, the focus is on resolving the low flux issue by suggesting a process involving multiple cycles throughout day and night. We investigate the influence of hydrogel particle size, membrane surface, hydrogel layer thickness, as well as swelling and deswelling time in one cycle. The swelling time displays a peak at an optimal absorption duration, while the deswelling time does not show a similar optimal point, highlighting the difference between swelling and deswelling phenomena. Therefore, the hydrogels' high absorption capacity alone is insufficient for achieving desalination success. The research findings emphasize the high importance of synthesis of a membrane with minimal resistance, enabling a high water flux and suitable selectivity.

АНАЛІЗ ВПЛИВУ ІНДИВІДУАЛЬНИХ ХАРАКТЕРИСТИК КОМІРОК LiFePO4 НА ПАРАМЕТРИ РОБОТИ АКУМУЛЯТОРНИХ ЗБІРОК

The article analyzes the influence of the individual characteristics of lithium-iron-phosphate (LiFePO4) cells on the overall efficiency, stability and duration of operation of battery assemblies. The influence of such parameters as internal resistance, polarization resistance and capacity on the operation of battery assemblies under different load regimes and changes in temperature conditions was studied. It was found that these parameters can vary significantly between cells within the same assembly, which leads to an imbalance during the operation of the battery system. Such an imbalance causes an uneven distribution of charge between the cells, which reduces the overall performance of the system, accelerates the degradation of the cells and shortens their service life. To overcome these problems, the use of active balancing methods based on Unscented Kalman Filter (UKF) algorithms was proposed. The application of UKF allows for dynamic evaluation of the state of charge (SOC) of each cell and adjustment of system parameters in real time, which provides more accurate management of battery assemblies in conditions of variable external factors such as temperature and current loads. Special attention is paid to online identification of battery parameters, such as polarization resistance and capacity, which change over time due to cell aging. The conducted studies confirmed that constant monitoring of temperature regimes is critically important for maintaining stable operation of battery cells, preventing overheating and ensuring uniform load distribution. The performed simulation confirmed the effectiveness of the application of adaptive methods of balancing and temperature control, which allows to increase the reliability and overall performance of battery assemblies.