Polar Strength Research Articles

Surface Modification of ETFE Membrane and PTFE Membrane by Atmospheric DBD Plasma.

Fluorine resin membranes with excellent chemical resistance have great potential for the application of high-performance chemical protective clothing. However, it is difficult to integrate fluorine resins into other materials such as fabrics due to their lower surface energy and poor bondability, making the fabrication of composite fabrics and the further seal splicing challenging. In this study, atmospheric pressure dielectric barrier discharge (DBD) plasma in helium (He) and helium/acrylic acid (He/AA) mixture atmospheres were used to modify two kinds of fluorine resins, ethylene tetrafluoroethylene (ETFE) and polytetrafluoroethylene (PTFE) membrane. The surface chemical properties, physical morphology, hydrophilicity and adhesion strength of the fluororesin membranes before and after plasma treatments were systematically analyzed. The results showed that the plasma treatment can modify the membrane surface at the nanoscale level without damaging the main body of the membrane. The hydrophilicity of the plasma-treated membrane was improved with the water contact angle decreasing from 95.83° to 49.9° for the ETFE membrane and from 109.9° to 67.8° for the PTFE membrane, respectively. The He plasma creates active sites on the membrane surface as well as etching the membrane surface, increasing the surface roughness. The He/AA plasma treatment introduces two types of polyacrylic acid (PAA)—deposited polyacrylic acid (d-PAA) and grafted polyacrylic acid (g-PAA)—on the membrane surface. Even after ultrasonic washing with acetone, g-PAA still existed stably and, as a result, improved the polarity and adhesion strength of fluororesin membranes. This work provides useful insights into the modification mechanism of DBD plasma on fluorine resins, with implications for developing effective strategies of integrating fluorine resin membrane to chemical protective clothing fabrics.

Rossby Waves in Total Ozone over the Arctic in 2000–2021

The purpose of this work is to study Rossby wave parameters in total ozone over the Arctic in 2000–2021. We consider the averages in the January–March period, when stratospheric trace gases (including ozone) in sudden stratospheric warming events are strongly disturbed by planetary waves. To characterize the wave parameters, we analyzed ozone data at the latitudes of 50°N (the sub-vortex area), 60°N (the polar vortex edge) and 70°N (inner region of the polar vortex). Total ozone column (TOC) measurements over a 22-year time interval were used from the Total Ozone Mapping Spectrometer/Earth Probe and Ozone Mapping Instrument/Aura satellite observations. The TOC zonal distribution and variations in the Fourier spectral components with zonal wave numbers m = 1–5 are presented. The daily and interannual variations in TOC, amplitudes and phases of the spectral wave components, as well as linear trends in the amplitudes of the dominant quasi-stationary wave 1 (QSW1), are discussed. The positive TOC peaks inside the vortex in 2010 and 2018 alternate with negative ones in 2011 and 2020. The extremely low TOC at 70°N in 2020 corresponds to severe depletion of stratospheric ozone over the Arctic in strong vortex conditions due to anomalously low planetary wave activity and a high positive phase of the Arctic Oscillation. Interannual TOC variations in the sub-vortex region at 50°N are accompanied by a negative trend of −4.8 Dobson Units per decade in the QSW1 amplitude, statistically significant at 90% confidence level, while the trend is statistically insignificant in the vortex edge region and inside the vortex due to the increased variability in TOC and QSW1. The processes associated with quasi-circumpolar migration and quasi-stationary oscillation of the wave-1 phase depending on the polar vortex strength in 2020 and 2021 are discussed.

Survey Nonresponse and Mass Polarization: The Consequences of Declining Contact and Cooperation Rates

Recent studies question whether declining response rates in survey data overstate the level of polarization of Americans. At issue are the sources of declining response rates—declining contact rates, associated mostly with random polling mechanisms, or declining cooperation rates, associated with personal preferences, knowledge, and interest in politics—and their differing effects on measures of polarization. Assessing 158 surveys (2004–2018), we show that declining cooperation is the primary source of declining response rates and that it leads to survey overrepresentation of people who are more engaged in politics. Analyzing individual responses to 1,223 policy questions in those surveys, we further show that, conditional on the policy area, this survey bias overestimates or underestimates the partisan divide among Americans. Our findings question the perceived strength of mass polarization and move forward the discussion about the effect of declining survey response on generalizations from survey data.

Effect of capping layer on the ferroelectricity of hafnium oxide

In this work, we investigate the effect of a capping layer of aluminum oxide (AlOx) on dopant-free hafnium-oxide (HfO2) ferroelectric layer. According to our experimental results, the AlOx-capped HfO2 ferroelectric capacitor exhibits the significant improvement on ferroelectric polarization strength and also presents a comparable electrical stress resistance in comparison with control HfO2 ferroelectric capacitor with a very weak ferroelectric hysteresis. An additional nitrogen treatment on AlOx capping layer effectively alleviate the stress-induced generation of defect traps near the interface of tantalum nitride (TaN) electrode under negative-bias voltage stress. Therefore, the performance improvement can be ascribed to the introduction of AlOx capping layer and well-controlled nitrogen plasma treatment to improve interface traps and stabilize the ferroelectric phase transformation during high-temperature annealing process.

Persuading republicans and democrats to comply with mask wearing: An intervention tournament

Many people practiced COVID-19-related safety measures in the first year of the pandemic, but Republicans were less likely to engage in behaviors such as wearing masks or face coverings than Democrats, suggesting radical disparities in health practices split along political fault lines. We developed an “intervention tournament” which aimed to identify the framings that would promote mask wearing among a representative sample of Republicans and Democrats in the U.S. from Oct 14, 2020, to Jan 14, 2021 (N = 4931). Seven different conditions reflecting different moral values and factors specific to COVID-19—including protection from harm (self), protection from harm (community), patriotic duty, purity, reviving the economy, threat, and scientific evidence—were implemented to identify which framings would “win” in terms of promoting mask wearing compared to a baseline condition. We found that Republicans had significantly more negative attitudes toward masks, lower intentions to wear them, and were less likely to sign or share pledges on social media than Democrats, which was partially mediated by Republicans, compared to Democrats, perceiving that the threat of COVID-19 was lower. None of our framing conditions significantly affected Republicans' or Democrats' attitudes, intentions, or behaviors compared to the baseline condition, illustrating the difficulty in overcoming the strength of political polarization during COVID-19.

Diffusiophoresis in suspensions of highly charged soft particles.

Diffusiophoresis phenomenon of aoft particles suspended in binary electrolyte solutions is explored theoretically in this study based on the spherical cell model, focusing on the chemiphoresis component in absence of diffusion potential. Both the electrostatic and hydrodynamic aspects of the boundary confinement, or steric effect, due to the presence of neighboring particles are examined extensively under various electrokinetic conditions. Significant local extrema are found in mobility profiles expressed as functions of the Debye length in general, synchronized with the strength of the motion-inducing double layer polarization. Moreover, a seemingly peculiar phenomenon is observed that the soft particles may move faster in more concentrated suspensions. The competition between the simultaneous enhancement of the motion-inducing electric driving force and the motion-retarding hydrodynamic drag force from the boundary confinement effect of the neighboring particles is found to be responsible for it. The above findings are also demonstrated experimentally in a very recent study on the diffusiophoretic motion of soft particles through porous collagen hydrogels. The results presented here are useful in various practical applications of soft particles like drug delivery.

Structure and circuit modeling of frequency domain polarization characteristics for porous composite material

The relationship between the permittivity of a two-phase porous composite material and its structure forms the basis for the adjustment and analysis of the permittivity of the porous material. However, existing calculation models exhibit significant errors at low frequencies. A wide-frequency equivalent model is proposed in this paper based on the geometrical structural characteristics of porous materials, considering the effects of interface polarization and dielectric relaxation process. The relationship between the two-phase porosity material and the dielectric response of its framework and filling medium in a wide-frequency range can be calculated. Furthermore, the modified Cole–Cole model is adopted to analyze the dielectric spectrum characteristics of cellulose and aramid, thereby exhibiting the effects of polar bonds in the molecular structure and impurity ions in the material on the polarization strength and polarization process. The results obtained from this study can provide key parameters and a basis for the analysis of the polarization process of two-phase combined porous materials and the design of low-permittivity insulating paper.

Interface engineering to optimize polarization and electric breakdown strength of Ba2Bi3.97Pr0.03Ti5O18/BiFeO3 ferroelectric thin-film for high-performance capacitors

Electrostatic capacitors based on dielectrics are ubiquitous components for applications in modern electronics and electric power systems. However, the relatively low energy density of electrostatic capacitors, which is one or two orders of magnitude lower than that of the batteries, has greatly hindered the implementation of its in energy storage devices. Here, we propose a strategy to overcome the tradeoff between high polarizability and breakdown electric field, and attain great enhancement energy storage density in the lead-free (Ba2Bi3.97Pr0.03Ti5O18/BiFeO3)N (BBPT/BFO)N multilayer ferroelectric thin films with different BFO layers through interface engineering. The interface engineering could be utilized to concurrently modify both polarization and local electric field strength caused by the synergistic effect of multiple polar structures and electric field amplifying effect. Accordingly, the discharged energy density of the optimized (BBPT/BFO)1 ferroelectric thin-film capacitors as high as ∼ 79.3 J/cm3 with discharged efficiency exceeding ∼ 75 % are achieved. Combined with its fatigue-free, favorable temperature and frequency stabilities, the multilayer ferroelectric thin films of BBPT/BFO could be a promising dielectric material for practical energy storage applications.

Excellent energy storage performance of paraelectric Ba0.4Sr0.6TiO3 based ceramics through induction of polar nano-regions

Dielectric energy storage materials with congenitally high power densities and ultrafast discharge rates have been extensively studied for emergent applications. As a typical and traditional dielectric material, paraelectric Ba0.4Sr0.6TiO3 (BST) ceramic exhibits a moderate dielectric constant (εr), low dielectric loss and slightly nonlinear P–E hysteresis. However, its energy storage density (W) is extremely low because of its low maximum polarisation (Pmax) and weak breakdown strength (BDS). In this study, ferroelectric Na0.5Bi0.5TiO3 (NBT) was introduced into paraelectric BST to enhance energy storage performance. The results show that the introduction of NBT induced polar nano-regions (PNRs) in the paraelectric matrix, resulting in a slim hysteresis loop with low remnant polarisation (Pr) and high Pmax simultaneously. Furthermore, owing to a decrease in the oxygen vacancy concentration and an increase in the band gap energy, the BDS of the BST ceramic also significantly increased. As a consequence, a remarkable energy storage density (Wrec = 3.89 J/cm3) and a high energy storage efficiency (η = 83.8%) were realised in the 0.75Ba0.4Sr0.6TiO3-0.25Bi0.5Na0.5TiO3 (0.75BST–0.25NBT) ceramic under a practical electric field of 360 kV/cm. Moreover, the ceramic also exhibited an excellent current density (∼1029.7 A/cm2) and ultrahigh power density (∼128.7 MW/cm2). The attained energy storage performances indicate that the NBT-modified BST ceramics are promising materials for high energy storage capacitor applications field.

Electro-responsive electrorheological effect and dielectric spectra analysis of topological self-crosslinked poly(ionic liquid)s

By changing the amount of vinylimidazole grafted on phenyl ring, we designed and prepared a series of topological self-crosslinked poly(ionic liquid)s (TS-PILs) with different number of spacer arms by free radical polymerization. The influences of the number of spacer arms on the electrorheological (ER) effect of TS-PILs in insulating carrier liquid were studied by rheological test under electric stimulus and the influence mechanism was analyzed by broadband dielectric spectroscopy. It was found that the ER effect of TS-PILs containing organic counterion bis(trifluoromethane sulfonylimide) (TFSI-) increased with the increase of the number of spacer arms. Broadband dielectric spectra analysis showed that the increased ER effect with the number of spacer arms was attributed to the increase of interfacial polarization strength and the decrease of electrode polarization with the number of spacer arms. Activation energy analysis indicated that increasing the number of spacer arms could promote ion pair dissociation and ion number density but inhibit long-range movement of ions, which was responsible for the increase of interfacial polarization strength and the decrease of electrode polarization. The results provided a guidance insight for the design and preparation of high-performance crosslinked PIL-based ER materials.

Effects of annealing temperatures on energy storage performance of sol-gel derived (Ba0.95, Sr0.05) (Zr0.2, Ti0.8) O3 thin films

Dielectric polarization and breakdown strength of dielectrics generally show directly and inversely dependent upon their crystallization, respectively. Therefore, achieving the maximum energy storage density should be expected by controlling the crystallization. A serial of ferroelectric (Ba0.95, Sr0.05)(Zr0.2, Ti0.8)O3 (BSZT) thin films were prepared by the sol-gel method. Effects of annealing temperatures on the microstructure, dielectric and energy storage performance of the films were investigated. The results indicate that BSZT thin films annealed at 600 °C for 30 min demonstrate the highest recoverable energy density and efficiency (50.5 J/cm3 and 91.9%). Such superior energy storage performance is attributed to an ultrahigh electric breakdown strength (6.65 MV/cm) induced by the dense amorphous-nanocrystalline microstructure. This work creates a new way for optimizing the energy storage performance of dielectric thin films via balancing their dielectric polarization and breakdown strength at appropriate heating processing temperature.

An audit of geomagnetic field in polar and south atlantic anomaly regions over two centuries

There are several reports about the decrease of the magnetic field of our planet. Here, we present a detailed investigation of the geomagnetic field over past 200 years using magnetic field models (IGRF+gufm1) and ground magnetic field observations until 2020. There are two prominent regions of consistently decreasing geomagnetic field namely: the South Atlantic Anomaly (SAA) and the southern pole region. The SAA region with field decreasing at 30 nT/year drifting to the south-west, whereas, the southern pole region with field decreasing at the rate 13 nT/year steadily drifting to the north-west. The Earth’s polar (66°–90°) magnetic field was invariably higher around the south pole as compared to the field around the north pole. However, it is found that over the past few decades (since 1950), the average magnetic field in the southern polar region has decreased to such an extent that presently it is weaker than the northern polar magnetic field. This tendency of cross-over in the magnitudes of average polar magnetic field strength is also evident in the ground magnetic field observations. On the ground at Hermanus (station in the SAA region), the rate of decrease of the magnetic field is found to be much higher (98 nT/year) during 1950–2020. Such a significant decrease in the magnetic field at Hermanus could be associated with the splitting of the SAA as it is situated close to the second minima in the SAA region. It is found that the magnetic field gradients around the center of the SAA become shallower as we move towards the higher altitudes. Also, the center of the SAA steadily moves in the north-east direction with increasing altitude. Though the weakening of the geomagnetic field is not an impulsive phenomenon but can invoke serious concerns to our life, satellites, and climate in near future.

Theoretical study on the multiferroic materials In2FeX (X = V, Cr, Mn, Co, and Ni) O6 for high photovoltaics and photocatalysis performance

The double perovskite multiferroic materials Bi2FeCrO6 have a more remarkable improvement in magnetoelectricity, photovoltaic, and photocatalysis performance than BiFeO3. The novel double perovskite multiferroic materials In2FeX (X = V, Cr, Mn, Co, and Ni) O6 are designed to achieve superior performance (e.g., in ferroelectricity and magnetism photovoltaic and photocatalysis) by density functional theory. The calculation results show that In2FeXO6 (X = V or Cr) O6 could be metastable multiferroic material with high ferroelectric polarization strength, and the ferroelectricity is driven by In-O ions interaction. In2FeVO6 has a suitable bandgap and produces high photoelectric conversion efficiency as excellent ferroelectric photovoltaic materials. In2FeVO6 also absorbs visible light to drive water splitting to produce hydrogen under tensile strain by analyzing the band edge position. These calculation results could guide realizing considerable ferroelectric polarization strength, high photovoltaic performance, and photocatalytic hydrolysis hydrogen production.

Piezoelectric BaTiO3 with the milling treatment for highly efficient piezocatalysis under vibration

The hydrothermally-synthesized barium titanate (BaTiO3) nanofibers are mechanically milled and used to for the piezocatalytic RhB dye decomposition. It is found that the mechanical milling can improve the piezocatalytic performance of BaTiO3 nanofibers. With the increasing of the milling time from 0 to 120 min, the RhB dye decomposition ratio of BaTiO3 nanofibers first increases and then decreases. When the milling time is 30 min, for the 20 min vibration time, the RhB decomposition ratio of BaTiO3 is 94%, which is much higher than that (~65%) of the unmilled BaTiO3. On one hand, the enhancement in piezocatalysis of BaTiO3 may be originated from the exposure of active sites due to the increasement of the specific surface area after the mechanical milling. On the other hand, it is also found that the ferroelectric polarization strength of BaTiO3 nanofibers obviously increases after the mechanical milling, which is helpful to reduce the recombination of these positive and negative carriers in the catalytic process, resulting in the enhanced piezocatalysis performance. The mechanical milling provides a convenient, fast, and effective method for improving the piezocatalytic activity of BaTiO3 nanofibers.

Insight into the oil polarity impact on interfacial properties of myofibrillar protein

The interfacial behaviour of myofibrillar protein is critical to the stability of myofibrillar protein-stabilized oil in water emulsions. However, the effect of oil phase on the interfacial behaviour of myofibrillar protein and the resultant emulsion properties has not been widely analyzed. Therefore, this study was focused on exploring the relationship among oil polarity, the interfacial behaviour of myofibrillar protein and the emulsion physical stability. The results suggested that the surface load, interfacial pressure, diffusion rate, rearrangement rate and dilatational elastic modulus increased with the oil polarity decreasing. This was attributed to the larger extent of myofibrillar protein unfolding on the apolar interfaces which promoted the exposure of hydrophobic groups, leading to an increased protein-oil and protein-protein intermolecular interactions on the interface. However, the oil polarity barely affects the secondary structure of interfacial myofibrillar protein. Intriguingly, the emulsion physical stability was improved with the oil polarity increasing in a certain range despite the impaired viscoelasticity of interfacial film, possibly due to the lower interfacial tension of polar oils. A further increase in polarity exceeding the certain range contrarily reduced the emulsion stability, potentially due to the desorption and collapse of interfacial film. Our results demonstrated that oil polarity and mechanical strength of interfacial film should both be taken into consideration when studying emulsion stability. This knowledge could provide an in-depth understanding to reveal the underlying mechanism of how oil polarity affecting the interfacial behaviour of proteins and consequently the physical stability of the corresponding emulsions.

First Observational Evidence for the Role of Polar Vortex Strength in Modulating the Activity of Planetary Waves in the MLT Region

AbstractBased on the meteor winds measured at Mohe (MH; 53.5°N, 122.3°E) and the reanalysis data, we investigate the variations of planetary waves in the mesosphere and lower thermosphere (MLT) region during the 2019/2020 Arctic winter. Four stratospheric polar warmings, including two sudden stratospheric warmings (SSWs), are observed from November 2019 to March 2020. Quasi‐10‐day waves (Q10DWs) are found to be enhanced following three of these warmings in the zonal winds in the MLT region over MH, but unusually weak after the SSW in February 2020. The trigger mechanisms of the enhanced Q10DWs are investigated and the reason for the unusually weak Q10DWs in February is revealed. Upward propagations and in situ generations of Q10DWs are both limited during the February SSW. Our analysis indicates that Q10DWs in the MLT region in February 2020 are largely inhibited by the extremely strong polar vortex and a lack of mesospheric instability.

Capturing Carriers and Driving Depolarization by Defect Engineering for Dielectric Energy Storage.

The inevitable defect carriers in dielectric capacitors are generally considered to depress the polarization and breakdown strength, which decreases energy storage performances. Distinctive from the traditional aims of reducing defects as much as possible, this work designs (FeTi' - Vo••)• and (FeTi″ - Vo••) defect dipoles by oxygen vacancy defect engineering in acceptor doped Sr2Bi4Ti(5-x)FexO18 layered perovskite films with n-type leakage conductance. It is shown that oxygen vacancies effectively capture electrons (carriers) in n-type dielectrics to enhance the breakdown strength. Meanwhile, defect dipoles provide a driving field for depolarization to engineer the generation energy of domains and the domain wall energy, which effectively lowers the residual polarization Pr but not at the expense of the maximum polarization Pmax as relaxor ferroelectric regulations. Such defect engineering effectively breaks through the limitation, in which the energy storage density suffers from the trade-off relationship between polarization and breakdown strength. The Sr2Bi4Ti4.92Fe0.08O18 film with the proper oxygen vacancy content achieves a high energy density of 110.5 J/cm3 and efficiency of 70.0% at a high breakdown strength of 3915 kV/cm. This work explores an alternative way for breakthroughs possible in the intrinsic trade-off relationship to regulate dielectric energy storage by defect engineering.

Electrorheology and dielectric polarization of backbone, pendant and cross-linked poly(ionic liquid)s

Backbone, pendant and cross-linked poly(ionic liquid) (PIL) particles with the same ion pair and similar ion number density have been prepared and the electro-responsive electrorheological (ER) effect of their suspensions in insulating carrier liquid has been comparably studied by rheology and dielectric spectroscopy. It has found that the ER effect of cross-linked PILs is strongest and that of backbone PILs is weakest. Dielectric spectrum analysis has showed that the difference of ER effect is mainly due to the difference in the ion leakage and effective interfacial polarization of PIL particles under electric fields. Although the backbone PILs have the largest interfacial polarization strength, its ion leakage conductance is also largest and this results in its weakest ER effect. The cross-linked PILs well restrains the ion leakage conductance and the ER effect is largely enhanced. The difference in ion leakage conductance and ER effect is further related to the difference of PIL matrix structure according to X-ray diffraction characterization. This study clarified the influence of matrix structure on ER effect and dielectric polarization of PILs and provided a guidance for the design of PIL ER materials.

Ion Microprobe Study of the Polarization Quenching Techniques in Single Crystal Diamond Radiation Detectors.

Synthetic single crystal diamond grown using the chemical vapor deposition technique constitutes an extraordinary candidate material for monitoring radiation in extreme environments. However, under certain conditions, a progressive creation of space charge regions within the crystal can lead to the deterioration of charge collection efficiency. This phenomenon is called polarization and represents one of the major drawbacks associated with using this type of device. In this study, we explore different techniques to mitigate the degradation of signal due to polarization. For this purpose, two different diamond detectors are characterized by the ion beam-induced charge technique using a nuclear microprobe, which utilizes MeV energy ions of different penetration depths to probe charge transport in the detectors. The effect of polarization is analyzed by turning off the bias applied to the detector during continuous or discontinuous irradiation, and also by alternating bias polarity. In addition, the beneficial influence of temperature for reducing the effect of polarization is also observed. Finally, the effect of illuminating the detector with light is also measured. Our experimental results indicate that heating a detector or turning off the bias, and then applying it during continuous irradiation can be used as satisfactory methods for recovering the CCE value close to that of a prepolarized state. In damaged regions, illumination with white light can be used as a standard method to suppress the strength of polarization induced by holes.

Prediction of Amplitude of Solar Cycle 25 using Polar Field Strength at the Cycle Minimum

Observed strength of the Sun’s polar magnetic field is in anti-correlation with relative sunspot number in the 11- year solar cycle. We studied cross-correlation between smoothed monthly sunspot number and modulus of smoothed polar magnetic field strength for different time lags. Maximal correlation coefficient (0.689) is calculated for the time shift of approximately 5.2 years. Using observed strength of polar magnetic field as precursor we have forecasted amplitude of the next solar cycle 25. It was found that predicted amplitude of solar cycle 25 is 116  12 or 130  26 depending on the parameter we used as precursor: 1) maximal value of modulus of smoothed strength of mean polar field near the cycle minimum or 2) modulus of mean polar field strength averaged one year just before the cycle minimum, respectively.