Slow Polarization Research Articles

Metasurface‐Based Mueller Matrix Microscope

AbstractIn conventional optical microscopes, image contrast of objects mainly results from the differences in light intensity and/or color. Muller matrix optical microscopes (MMMs), on the other hand, can provide significantly enhanced image contrast and rich information about objects by analyzing their interactions with polarized light. However, state‐of‐the‐art MMMs are fundamentally limited by bulky and slow polarization state generators and analyzers. Here, the study demonstrates a metasurface‐based MMM, i.e., Meta‐MMM, which is equipped with a chip‐integrated, single‐shot metasurface polarization state analyzer (Meta‐PSA). The Meta‐MMM is featured with high‐speed measurement (≈2s per Muller matrix (MM) image), superior operation stability, dual‐color operation, and high measurement accuracy (measurement error 1–2%) for MM imaging. The Meta‐MMM is applied to nanostructure characterization, surface morphology analysis, and discovering birefringent structures in honeybee wings. The Meta‐MMMs hold the promise to revolutionize various applications from biological imaging, medical diagnosis, and material characterization to industry inspection and space exploration.

Meliorative dielectric properties in core@double-shell structured Al@Al2O3@PDA/PVDF nanocomposites via decoupling the intra-particle polarization and inter-particle polarization

Percolating polymeric composites present enormous potential owing to high dielectric constant (ε) which can be realized near the percolation threshold, but the accompanied large loss forbids their extensive use in practice. Great efforts have been devoted to coat conductive particles with an insulating shell for constrained dielectric loss, yet they markedly reduce ε. In this work, we explore poly(vinylidene fluoride) (PVDF) composites with a serial of core@double-shell Al@Al2O3@PDA (polydopamine) nanoparticles with various PDA shell thicknesses. It reveals that the high ε of the nanocomposites results from a fast intra-particle polarization and a slow inter-particle polarization. The formation of double-shell enables the independent control of the two polarizations always coupled in traditional percolating composites. Through facilitating intra-particle polarization and repressing inter-particle polarization, Al@Al2O3@PDA/PVDF can achieve a much higher ε and lower dielectric loss simultaneously, far exceeding the unmodified Al@Al2O3/PVDF. Moreover, the calculated activation energy of carrier migration in Al@Al2O3@PDA/PVDF is obviously higher than that in untreated nanocomposites, indicating enhanced charge-trapping capability in the core@double-shell nanofiller composites. This core@double-shell strategy offers a new paradigm for the design and preparation of percolating composites with desirable dielectric performances.

Structural characterization of LLDPE/MgO insulation composites in terms of space charge accumulation in an HVDC field

This study addresses the critical role of insulation materials in high-voltage direct current (HVDC) transmission systems, emphasizing the challenges associated with space charge accumulation and slow polarization effects. The primary objective of this study is to investigate the utilization of linear low-density polyethylene (LLDPE) in High Voltage Direct Current (HVDC) applications, with a focus on enhancing its performance through the incorporation of magnesium oxide (MgO) nanoparticles. The research employs various techniques, including X-ray diffraction, nuclear magnetic resonance, broadband dielectric spectroscopy, conductivity measurements and pulse electroacoustic measurements, to analyse the internal structure, crystallinity, and space charge dynamics of LLDPE/MgO nanocomposites. The results demonstrate that controlled MgO incorporation optimizes the internal electric field, improving the electrical properties without significantly altering the charge decay rate. The multidimensional approach of the study provides valuable insights into tailored modification of insulation materials for enhanced HVDC transmission performance, considering both electrical and structural aspects.

Mechanism and evaluation method of stress corrosion susceptibility of 904L stainless steel with optimized structure in seawater

The stress corrosion cracking (SCC) and the electrochemical behavior of 904 L stainless steel in a simulated seawater environment were investigated using slow strain rate testing (SSRT), electrochemical polarization, electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M-S) curves. The sensitive potential range of 904 L stainless steel was determined by the fast and slow scan potential polarization curve, is − 950 mVSCE ∼ 270 mVSCE. Moreover, with the negative shift of applied potential, the toughness fracture characteristic of the three kinds of steel is reduced, and the sensitization state steel is the most obvious reduction. Finally, a practical formula for evaluating the SCC susceptibility of 904 L stainless steel was developed by integrating data from SSRT and fast and slow scan polarization curves.

Novel Perovskite Structured Nd0.5Ba0.5Co1/3Ni1/3Mn1/3O3-δ as Highly Efficient Catalyst for Oxygen Electrode in Solid Oxide Electrochemical Cells.

Developing catalytic materials with highly efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is essential for lower-temperature solid oxide fuel cell (SOFC) and electrolysis cell (SOEC) technologies. In this work, a novel triple perovskite material, Nd0.5Ba0.5Co1/3Ni1/3Mn1/3O3-δ, has been developed and employed as a catalyst for both ORR and OER in SOFC and SOEC operations at relatively lower temperatures, showing a low polarization resistance of 0.327 Ω cm2, high-power output of SOFC up to 773 mW cm-2 at 650 °C, and a high current density of 1.57 A cm-2 from SOEC operation at 1.5 V at 600 °C. The relaxation time distribution reveals that Nd0.5Ba0.5Co1/3Ni1/3Mn1/3O3-δ could maintain a slow polarization process at the relatively low operating temperature, offering a significant antipolarization advantage over other perovskite electrode materials. The Nd0.5Ba0.5Co1/3Ni1/3Mn1/3O3-δ electrode provides a low energy barrier of about 0.36 eV in oxygen ion mobility, which is beneficent for oxygen reduction/evolution reaction processes.

Finite Modeling and Simulation of the Effects of Neutral Electrolytic Pickling Process Parameters on EN 1.4404 Steel Strips

Surface treatment via neutral electrolytic pickling (NEP) aims to remove oxide layers and scaling from stainless steel. The objective of this study was to investigate the factors that affect the energy efficiency of the process. This study developed a COMSOL Multiphysics model for the distribution of current across a bipolar steel strip by controlling the following parameters: Na2SO4 concentration, temperature, electrode-to-strip distance, and inter-electrode distance. Full factorial measurements of the electrolyte’s conductivity as well as the steel strip’s and the electrode’s polarization were conducted to provide data for the NEP model. Galvanostatic pulse measurements were performed to calculate transient times during pickling. According to the model, an applied voltage of less than 11 V was insufficient to polarize the steel strip to the potentials needed on both the anodic and cathodic sides. A higher voltage of 11–15 V resulted in anodic current densities of 600–1600 A m−2 and cathodic current densities of 700–2000 A m−2 on the steel strip. These current densities are within the range of previous experimental studies and industrial practices. The model showed that when a steel strip acts as a bipolar electrode, the current’s efficiency decreases, as only a fraction of the strip facing the anodes or cathodes is polarized sufficiently. The galvanostatic tests showed that anodic polarization of the steel strip is easier than cathodic polarization. The slow polarization in the cathodic direction can be improved by using a higher current density. The time needed to polarize stainless steel indicates that the strip’s velocity should be less than 1 m s−1 to give enough time for polarizing the steel strip.

Core@Double-Shell Engineering of Zn Particles toward Elevated Dielectric Properties: Multiple Polarization Mechanisms in Zn@Znch@PS/PVDF Composites.

Flexible dielectrics with large dielectric constant (ε') coupled with low loss are highly pursued in many applications. To bolster the ε' of raw Zn (zinc)/poly(vinylidene fluoride, PVDF) while maintaining pimping dielectric loss, in this study, the core@double-shell structured Zn@zinc carbonate (ZnCH)@polystyrene (PS) particles are first synthesized through a suspension polymerization of styrene, and then composited with PVDF to elevate the ε' and keep low loss of the composites. By optimizing the PS shells' thickness and tailoring the electrical resistivity of Zn@ZnCH@PS particles, both the slow inter-particle polarization and fast intra-particle polarization in the composites can be decoupled and synergistically tuned, thus, the Zn@ZnCH@PS/PVDF achieves a much higher ε' and lower dielectric loss, simultaneously, which far exceed the unmodified Zn/PVDF. Both experiment and theoretic calculation reveal that the double-shell ZnCH@PS not only induces and promotes multiple polarizations enhancing the composites' ε', especially at the optimized PS's thickness, but also maintains suppressed loss and conductivity thanks to their obvious barrier effect on long-range charge migration. The core@double-shell filler design strategy facilitates the development of polymer composites with desirable dielectric properties for applications in electronic and electrical power systems.

Effect of different defects on the polarization mechanism of (Nb,Ga) codoped TiO2 single crystals

Various defects have a profound impact on the dielectric properties and polarization mechanisms of (Nb,Ga) codoped TiO2 crystals. However, the research conducted in this area remains limited. To address this, we grew (Nb,Ga) codoped TiO2 crystals via the Verneuil method and investigated their dielectric properties under various atmospheric annealing conditions. Annealing in oxygen reduces the number of defects. In this case, the point defects associated with oxygen vacancies is unable to fully form the ideal complex defect clusters which can form effective pegging of free electrons. On the other hand, the defects are mainly in the form of simple defect clusters that causes hopping polarization. Annealing under mixed gas (Ar:H2 = 95%:5%) increases the number of defects and contains more free carriers, which migrate to the interface between the sample and the electrode, leading to interfacial polarization. Both hopping polarization and interfacial polarization are slow polarization, resulting in an increase in dielectric loss and a decrease in frequency stability. Annealing in air or nitrogen atmospheres forms ideal defect dipole clusters, where the electron-pinned defect dipoles (EPDD) are predominantly polarized, resulting in superior dielectric properties. It has been clarified that EPDD as the main polarization form can yield better dielectric properties. By focusing on single crystals as the research subject, we effectively eliminate the influence of grain boundaries, enabling a more accurate assessment of the effects of various crystal defects on dielectric properties. This study holds substantial implications for the advancement of TiO2-based dielectric materials, offering valuable insights into their performance optimization.

Out-of-plane polarization reversal and changes in in-plane ferroelectric and ferromagnetic domains of multiferroic BiFe0.9Co0.1O3 thin films by water printing

BiFe0.9Co0.1O3 is a promising material for an ultra-low-power-consumption nonvolatile magnetic memory device because local magnetization reversal is possible through application of an electric field. Here, changes in ferroelectric and ferromagnetic domain structures in a multiferroic BiFe0.9Co0.1O3 thin film induced by “water printing”, which is a polarization reversal method involving chemical bonding and charge accumulation at the interface between the liquid and the film, was investigated. Water printing using pure water with pH = 6.2 resulted in an out-of-plane polarization reversal from upward to downward. The in-plane domain structure remained unchanged after the water printing process, indicating that 71° switching was achieved in 88.4% of the observation area. However, magnetization reversal was observed in only 50.1% of the area, indicating a loss of correlation between the ferroelectric and magnetic domains because of the slow polarization reversal due to nucleation growth.

Engineering of core@double‐shell structured Zn@ZnO@PS particles in poly(vinylidene fluoride) composites towards significantly enhanced dielectric performances

AbstractPolymeric dielectrics with high dielectric permittivity (ɛ′) and low loss have momentous applications in energy storage devices. In this study, to concurrently improve the ɛ′ and restrain the loss of original Zn (Zinc)/poly(vinylidene fluoride, PVDF), the core@double‐shell structured Zn@ZnO(zinc oxide)@PS(polystyrene) particles were prepared and composited with the PVDF. The impacts of the dual shells on the dielectric properties and polarization mechanism of composites were explored by fitting the experimental data with a Havriliak–Negami (H–N) equation. The Zn@ZnO@PS/PVDF exhibit remarkably higher ɛ′ in comparison to the raw Zn and Zn@ZnO fillers owing to the induced multiple polarizations originating from the combined contributions of the α relaxation of PVDF, slow interparticle polarization and fast intraparticle polarization. More importantly, the ɛ′ of the composites remarkably increases with the PS shell’ thickness, while the loss is still kept at rather low levels owing to the PS shell’ barrier effect on long‐range charges migration. So, the introduction of the PS shell synchronously promotes both the interparticle and intraparticle polarizations in the Zn@ZnO@PS/PVDF composites toward enhanced dielectric properties. The developed strategy opens a novel path to the design and fabrication of polymer composites with desirable dielectric performances for applications in electronics and electrical industry.

Fully solution-processed carbon nanotubes thin film transistors and PMOS inverters on glass substrate

We report fully solution-processed thin film transistors and PMOS inverters fabricated on glass substrates using single-walled carbon nanotubes (SWCNTs) as active semiconducting material. All the electrodes (gate, source, and drain) were inkjet-printed using silver (Ag) as conductive ink. Spin coated poly-4-vinylphenol dielectric was optimized in terms of thickness and heating conditions for solution-processed SWCNTs thin film transistors to achieve a mobility equal to 0.81 cm2 V−1s−1. We will show that, hole traps at the dielectric-semiconductor interface are responsible for the hysteresis in the transfer curve, and controlled by the different sweep rate of the gate field. Drain-current transients under different bias conditions were studied and the increase in current occurs due to slow polarizations of residual dipolar groups in the dielectric. The adopted technology has been exploited to fabricate a PMOS inverter and studied for high gain and noise margin values at the supply voltage, V DD = −40 V.

Charge transport in semi insulating bulk 4H-Silicon carbide: Effect of metallization and wafer homogeneity

We investigated the effect of metallization and spatial homogeneity on the charge collection of sensors prepared from high purity semi-insulating 4H-SiC bulk wafer. We used Au, Ni, Cr or graphene electrical contacts subsequently prepared on the same chip. We also tested sensors prepared from different positions on the wafer. Laser-induced transient current technique (L-TCT) and alpha spectroscopy were used to characterize the charge transport in the sensors. It was found that different sensors polarize at DC bias in the time interval of 0.2–270 s. We observed significant deviation of current transients measured on the sensor with a graphene contact from the sensors with metal contacts, which is attributed to the surface plasmon formed on the graphene-SiC interface. We demonstrated that the sensor polarization is independent of the metallization, whereas it strongly depends on the location on the wafer from which the sensor was cut. This testifies to a significant spatial inhomogeneity of the wafer. We also tested the electrical current relaxation after step-DC biasing as a simple method for the characterization of the sensor polarization. We found that the relaxation profile has extremes in the similar positions as the L-TCT profiles of collected charge. We also showed that using pulse biased L-TCT we are able to choose suitable sensors with slow polarization and to design optimal pulsing conditions including necessary depolarization times for the alpha spectroscopy measurement and L-TCT techniques to achieve long-term stable charge collection. In case of 241Am alpha spectroscopy charge collection efficiency 5–24 % was observed. We framed up model depicting all observed phenomena assuming the space charge formation induced by a blocking cathode in an n-type material and related lifetime reduction. We evaluated the space charge formed in the sensors after 104 s biasing, which ranged from 1.7 × 1014 cm−3 to 7 × 1014 cm−3 in respective sensors.

Ultra-large dynamic range synaptic indium gallium zinc oxide transistors

Three-terminal neuromorphic transistors have garnered considerable attention owing to their superior learning and recognition capabilities in neural computing. For efficient and rapid computing of parallel arithmetic and unstructured large-sized data, a high-synaptic channel conductance (G) (i.e., synaptic weight) and large dynamic range (DR) (i.e., weight update) are necessary. In this study, we successfully fabricated high-performance and all-solution-processed synaptic transistors by employing a thiol–ene photoclick chemistry-based, cross-linked vinyl addition polynorbornene copolymer dielectric layer, poly(norbornene-co-5-vinyl-2-norbornene) (P(NB/VNB)) and sol-gel-derived indium gallium zinc oxide (IGZO) semiconducting channel layer. The molecular behaviors of free hydroxyl group in the dielectric layer formed via ultraviolet photo-induced thiol–ene click reactions of the polar cross-linker pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) allows slow dipole polarization effects on the IGZO channel layer. An exhaustive and systemic investigation of the surface physicochemical and electrical properties confirmed that the mutual interface coupling between the cross-linked P(NB/VNB) dielectric and IGZO semiconductor exhibited remarkable synaptic functionality with a high G (∼540 μS), large DR (∼6213), and long-term operational stability following excitation with 104 successive pulses that resulted in neural recognition accuracy of 87.11% based on the use of MNIST database set which is close to ideal value of 88%. This high-performance synaptic transistor based on all-solution-derived functional organic–inorganic hybrid stack layers can serve as a basis for the successful implementation of novel neuromorphic computing systems that satisfy the requirements for strong neuronal signal transmission and distinguishable multi-level data states.

Exploration of Erdaohe Silver Polymetallic Deposit in Inner Mongolia based on Induced Polarization Method

The exploration of Erdaohe Cu-Ag-Pb-Zn deposit in Zhalantun City, Inner Mongolia has entered the stage of blind exploration. It is a difficult problem at this stage whether common geophysical methods can find anomalies caused by 300∼1000 m or deeper Pb-Zn deposits in this area. Whether the problem is solved or not has a strong practical significance for the current and future prospecting work in this area. According to the theory of induced polarization sounding in time domain, it is considered in this paper that when the parameters such as high power, suitable device, and time delay are well coupled with the deep blind ore, it is possible to find anomalies caused by deep lead-zinc ore larger than 300 m. In order to prove the feasibility of the deep application of this method, the high-power induced polarization sounding experiment with different devices and different power supply cycles was carried out in Erdaohe copper-silver lead-zinc mine. The test results show that by adopting the measurement method of the encrypted equipotential device and selecting the appropriate polar distance, when the power supply period is 32 s, the time delay is 200 s and the sampling width is 200 s, a good deep lead-zinc mine anomaly can be found. The equipotential symmetrical quadrupole sounding MN/AB = 1/10 and the depth correction coefficient is 0.41 for inversion can accurately determine the anomaly location, which is worthy of popularization and application in this area. The ore bodies in this area are controlled by structures and distributed in lenticular layers along the fault footwall interlayer fracture zone. The ore bodies may change with the occurrence of the fracture surface. The characteristics of low resistivity, low slow, and high polarization of IP and single peak anomaly of IP sounding are important signs of lead-zinc prospecting in this area.

Binary-Synaptic Plasticity in Ambipolar Ni-Silicide Schottky Barrier Poly-Si Thin Film Transistors Using Chitosan Electric Double Layer.

We propose an ambipolar chitosan synaptic transistor that effectively responds to binary neuroplasticity. We fabricated the synaptic transistors by applying a chitosan electric double layer (EDL) to the gate insulator of the excimer laser annealed polycrystalline silicon (poly-Si) thin-film transistor (TFT) with Ni-silicide (NiSi) Schottky-barrier source/drain (S/D) junction. The undoped poly-Si channel and the NiSi S/D contact allowed conduction by electrons and holes, resulting in artificial synaptic behavior in both p-type and n-type regions. A slow polarization reaction by the mobile ions such as anions (CH3COO− and OH−) and cations (H+) in the chitosan EDL induced hysteresis window in the transfer characteristics of the ambipolar TFTs. We demonstrated the excitatory post-synaptic current modulations and stable conductance modulation through repetitive potentiation and depression pulse. We expect the proposed ambipolar chitosan synaptic transistor that responds effectively to both positive and negative stimulation signals to provide more complex information process versatility for bio-inspired neuromorphic computing systems.

Analogue of electromagnetically induced transparency inspired by bound states in the continuum and toroidal dipolar response in all-dielectric metasurfaces

Optical resonance cavity with high Q-factor is a paramount indicator of high-performance photonic devices. In this article, we present an all-dielectric metasurface composed of hollow cylindrical tetrameric clusters in the near-infrared region. Combining with the bound states in the continuum (BICs) theory, a distinct analogue of electromagnetically induced transparency (EIT) resonance arises. The squared inverse relationship between the Q-factor and the asymmetric parameters is calculated to corroborate the excitation of the quasi-BIC EIT pattern. By observing the distribution characteristics of the electromagnetic field in resonant mode and performing a multipole decomposition, the proposed metasurface can support magnetic dipole (MD), electric quadrupole (EQ) and toroidal dipole (TD) response simultaneously, which exhibits remarkable field confinement capability. The geometric parameters are adjusted to observe the variation of the dipole scattering energy. Subsequently, the transmission spectrum shows a peculiar pair of TD resonances, which possess remarkably dependence on polarization. The sensitivity and figure of merit (FOM) values of the sensor can reach 430 nm/RIU and 483 RIU−1. It is believed that the proposed metasurface may provide a constructive approach for slow light devices, high-performance sensors and polarization independent devices.

Corrosion behaviours of B + F dual-phase X80 pipeline steel in simulated near neutral and acidic soil solution

ABSTRACT Slow strain rate tensile corrosion (SSRT), immersion corrosion and polarisation behaviours of B + F dual-phase X80 pipeline steel in simulated near-neutral and acidic soil solutions were compared. The stress corrosion of X80 steel in acidic soil solution is more sensitive, whose mechanism is intergranular fracture induced by pitting. Crack nucleates at the bottom of corrosion pit and propagates along the weak path–grain boundary. In near-neutral soil solution, the crack is originated from a corrosion pit and propagated mainly transgranular. The parabolic velocity constant in immersion test and corrosion current of X80 steel in acidic soil solution is much higher, 40 and 2.7 times of those in near-neutral soil solution respectively. Dual-phase X80 steel has poor corrosion resistance in acidic soil solution. X80 steel in near-neutral soil solution corrodes in the form of an irregular corrosion pit at the bainite area, or a round corrosion pit near inclusions.

Dielectric Response Model for Transformer Insulation Using Frequency Domain Spectroscopy and Vector Fitting

This paper proposes a rational approximation-based approach to find positive real parameters for the extended Debye model (EDM), aimed at condition assessment of insulation systems of power transformers. The EDM can model the slow and fast polarization phenomenon, including relaxation mechanisms with different relaxation times within a composite dielectric material. In the proposed approach, the complex permittivity of the transformer’s composite insulation is approximated via rational functions, as given by the vector fitting (VF) software tool, and the EDM parameters are identified from the obtained poles/residues. To guarantee positive real parameters, i.e., a physically realizable circuit, VF is internally modified to calculate the final residues of the rational approximation via a constrained linear least-squares problem without resorting to further post-processing algorithms, as in existing methods, hence without affecting fitting accuracy. The effectiveness of the parametrized EDM is demonstrated in two ways: (a) by reconstructing frequency domain spectroscopy (FDS) curves provided via measurements in new oil-immersed power transformers and (b) by the comparison of the calculated polarization current given by EDM versus real measurements in time domain. The achieved fitting accuracy in most of the cases is above 99 percent for the reconstructed FDS curves, while the polarization current waveform is reproduced with good agreement.

Enhanced dielectric and thermal properties of Zn/PVDF composites by tailoring core@double-shell structured Zn particles

In this study, poly(vinylidene fluoride) (PVDF) composites containing a core@double-shell structured zinc (Zn) filler (i.e., Zn@ZnCH@ZnO) were synthesized. The primary focus is to investigate the effect of double shell on the polarization mechanism of composites by analyzing the dielectric properties and fitting the experimental data with a Havriliak–Negami (HN) expression. The results verify that the Zn@ZnCH@ZnO/PVDF composites exhibit prominently enhanced dielectric constant, suppressed loss and conductivity over pure PVDF and the pristine Zn/PVDF thanks to induced multiple polarizations generated in the core@double-shell configuration. The fitting curves reveal that the multiple polarizations are derived from the combined contributions of the α relaxation of PVDF, fast intra-particle polarization and slow inter-particle polarization. Furthermore, the thermal conductivity of Zn@ZnCH@ZnO/PVDF composites is enhanced by changing the amorphous ZnCH to crystalline ZnO shell promoting phonon transport. This work opens a new avenue to obtain comprehensively good performances of dielectric composites for potential application in microelectronics.

Dielectric relaxation induced by oxygen vacancies in Na0.5Bi0.5TiO3 ceramics

Dielectric permittivity was studied in ceramics of relaxor ferroelectric bismuth-sodium titanate Na0.5Bi0.5TiO3. The measurements were performed on as sintered and heat treated in vacuum samples. The diffuse dielectric anomalies associated with the structural phase transitions were observed in as sintered samples. The intense peak of permittivity (εmax ∼ 104) appeared after heat treating in vacuum. The anomaly of ε(T) was contributed by slow polarization processes (f < 10 kHz) and was non-stable, vanishing on heating in air up to ∼ 800 K. Temperature and frequency dependencies of ε were described by using Cole-Cole model with accounting thermally stimulated decay of the non-stable polarization. It is supposed that the dielectric anomaly is determined by space charge polarization mechanism. Oxygen vacancies VO•• and electrons localized on titanium ions Ti'Ti are assumed to be responsible for the phenomenon observed.