Large Capacitance Values Research Articles

Analisis Ripple Voltage pada Rangkaian Half-Wave Rectifier dan Full-Wave Rectifier Menggunakan Kombinasi Filter Kapasitor dan Resistor

The aim of this research is to investigate and analyze the ripple voltage in half wave and full wave rectifier circuits with a focus on the use of a combination of capacitor and resistor filters. This research is experimental research using Circuit Wizard. The tools and materials used include CT transformers, diodes, resistors, capacitors, multimeters, alternating power sources, and oscilloscopes. The research process begins by designing and implementing a circuit in the Circuit Wizard simulator according to the concept of half wave and full wave rectification with capacitor and resistor filters. The research results show that to produce a small ripple voltage, use large capacitance and resistance values. The best ripple voltage value produced is 0.6 V when using a 150 mF capacitor or 1000 Ohm resistor.

Physics-Based Modelling of Hybrid Cathode Li/CFx-SVO Batteries Under Pulse Discharge

Power sources of implantable cardioverter-defibrillators (ICD) require high energy density to ensure longevity and sufficient rate capability to provide high power pulses for treating abnormal heart rhythms. Such demands have led to the design of Li/CFx-SVO battery, which leverages the excellent energy density of carbon monofluoride (CFx) and power density of silver vanadium oxide (SVO) through the use of a CFx-SVO hybrid cathode. A phenomenological model based on porous electrode theory was previously developed for Li/CFx-SVO, but it overlooked phase separation in SVO, Li+ diffusion limitations in particles, and reaction heterogeneity across particles. It was thus unable to accurately predict the voltage over-recovery behavior during transitions from medium to low currents, capture relaxation behavior after high current pulses without the use of unrealistically large capacitance values, or interactions between active materials in the hybrid electrode.In this work, we present a computational model of Li/CFx-SVO battery based on Multiphase Porous Electrode Theory for hybrid electrodes (Hybrid-MPET). Hybrid-MPET framework allows us to model the phase separation during reduction of SVO, concentration gradients in SVO particles and the evolution of reaction heterogeneities across an ensemble of particles under different current rates. As a result, our Hybrid-MPET model excels at predicting voltage-capacity behavior under constant current or constant load discharge, is capable of providing physical explanation of voltage over-recovery and voltage relaxation, and captures the interactions between SVO and CFx particles during transient currents. The Hybrid-MPET models are validated against experimental data from Li/CFx-SVO batteries of different designs, and show consistent modelling capability across different electrode thickness, particle lengthscales, and discharge timescales. Our work demonstrates how physics-based models can help provide fundamental understanding of experimental phenomenon, and we further discuss how the Hybrid-MPET framework could open up new opportunities to study the performance of hybrid electrode batteries and support their engineering design in a broader range of devices. Figure 1

Phase field study on the flexoelectric response of dielectric–ferroelectric multilayers

We report a theoretical modeling of the flexoelectric response of dielectric–ferroelectric (DE–FE) multilayers based on phase field simulations in the framework of the Landau–Ginzburg–Devonshire (LGD) theory. The correlation between negative capacitance and flexoelectric response is revealed, and the single-domain and multi-domain models are compared. It shows that the dielectric layers drive the ferroelectric layer into a negative capacitance regime, and the flexoelectric response of the multilayer is maximal when the negative capacitance of the ferroelectric layer has a minimal absolute value. Moreover, the flexoelectric response peak will be shifted to a lower temperature by increasing the thickness of dielectric layer, indicating a possibility of achieving a stronger flexoelectric response at room temperature compared with that of pure ferroelectric. However, while the single-domain model shows that the flexoelectric response peak is simply shifted to a lower temperature with near constant peak value and width, the multi-domain model reveals a significant suppressing of the flexoelectric peak by the dielectric layer. This is attributed to the formation of the vortex domain state, which eases the depolarization effect and leads to large absolute value of negative capacitance of the ferroelectric layer. Our work provides new insights into flexoelectricity in ferroelectric heterostructures.

Manganese-based coordination framework derived manganese sulfide nanoparticles integrated with carbon sheets for application in supercapacitor

Manganese sulfide (MnS) with high specific capacitance and low-cost merits, has been investigated as a potential electroactive material for supercapacitor. However, in practical application, MnS has been suffering from some disadvantageous issues such as insufficient electrical conductivity, serious particle agglomeration as well as huge volume change during continuous charges and discharges, which resulted in a limited specific capacitance, shortened working life and inferior rate performance. Engineering electrode materials with controlled nanostructure and composition is pivotal to improve electrichemical performance of supercapacitors. This paper introduces a facile in situ sulfuration method to fabricate MnS/NSC composite with Mn-hexamethylene tetramine coordination framework as precursor. The results indicated that MnS nanoparticles were highly dispersed and incorporated into nitrogen, sulfur-doped carbon microsheets in MnS/NSC composite. Carbon matrix effectively dispersed and confined the MnS nanoparticles, thus inhibiting aggregation, relieving volume change and retaining structural integrity. Moreover, the 2D conductive carbon matrix reduced the diffusion distance for ions and ensured fast electron delivery. As a result, MnS/NSC electrode delivered a tremendously boosted electrochemical performance for supercapacitor. A large capacitance value about 1881.8F/g was achieved at 1A/g. Even cycling for 3000 loops at 40 A/g, MnS/NSC electrode retained a large capacitance of 404.3F/g. Furthermore, an asymmetric capacitor based on assembly of MnS/NSC composite cathode and activated carbon anode was fabricated. As tested under a current density of 0.1 A/g, it delivered a capacitance of ∼ 110.1F/g and achieved an energy density of 12.4 Wh kg−1 along with a power density of 3.03 kW kg−1. These results demonstrate the potential utilization of MnS/NSC composite as electrodes for energy conversion and storage devices and open up a route for material design for future energy storage devices.

Electrocution Risk of Capacitive Discharge Shocks: Application to Electric Vehicle Charging.

It is difficult to electrocute (induce ventricular fibrillation) with capacitive discharge shocks. With small capacitance values, the high voltages required for the necessary charge are rarely seen in industrial situations (e.g. electric vehicle charging stations). On the other hand, with large capacitance values, the discharge time is so great that the shock couples inefficiently with the cardiac cells. The update to IEC 60479-2 sets the C1 "mostly-safe" charge limit of 3 mC for a short "impulse function" pulse. We calculated the equivalent capacitor stored charge for an arbitrary capacitance value using the simple single membrane time constant model for the cardiac response. The peak membrane response was set equal to that of the 3 mC impulse function response to calculate the safe values for stored charge, voltage, and energy. The total stored charge, per se, cannot be used simplistically to estimate the danger of a capacitive discharge shock. A capacitive-discharge shock cannot be accurately compared to a rectangular shock with a duration equal to the shock time constant. The greater the capacitance, the larger the fraction of wasted charge in coupling to the heart and thus the shorter equivalent duration compared to the shock time constant. For a capacitive discharge shock this translates to a stored charge of 3 mC increasing up to 9 mC for a 10 capacitor using the assumed 575 load for an electric-vehicle (EV) charging station. In the area of interest for 1 - 10 the safe voltage ranges from 1300 to 4700 V, which includes the 1500-VDCscope of EV charger standard IEC 61851-23. For C > 100 the voltage asymptote is 700 V.

Electrochemical Capacitive Properties of Ny/PP/GO Electro-spun Composite Coating on Stainless Steel in Acid Media

Composite materials were manufactured to obtain singular properties to be used as in electrochemical driven energy systems. An electrochemical evaluation was performed on electro-spun nylon 6,6 fibers (Ny), with different concentrations of tetra-para-amino-phenyl porphyrin (PP) and graphene oxide (GO) composite coating over stainless steel (SS), immersed in 1M H2SO4 aggressive sulfuric acid solution. Different film coatings behavior was obtained and compared using electrochemical impedance spectroscopy (EIS). Also, cyclic voltametry (CV) were performed on nylon/PP/GO composite coating system at different scan rates, and over film covered carbon cloth. For the electro-spun composite coating on stainless steel EIS, lower electro-spinning times present higher impedance, hence some corrosion protection. For greater electro-spinning times, larger capacitance values were observed. These were possibly due to thicker coating or mass transport adsorption-diffusion process through the composite film, respectively. For the composite coating, porphyrins, and graphene oxide interaction present ionic conductivity, reducing the impedance and promoting proton formation, property which could be used in charge storage systems.

Operating Limits for Low-Capacitance Cascaded H-Bridge Static Compensators

The cascaded H-bridge (CHB) low-capacitance static compensator (LC-StatCom) has a limited inductive region compared to a conventional StatCom, both in balanced and unbalanced conditions, due to the inherent large oscillations on the capacitor voltages. This article presents a detailed analysis of the viable operating region in these converters that takes into account the inherent large oscillations. The analysis facilitates sizing of the dc-link capacitors to ensure that the StatCom is able to inject a given range of positive- and negative-sequence current. Though the analysis is generic and applicable to the CHB StatComs with relatively large capacitance values, it is more relevant in the LC-StatComs. In addition, the article derives reference steady-state signals that can be used as feedforward terms in LC-StatCom control loops to enhance the control performance. The article presents simulation and experimental results, in balanced and unbalanced conditions to corroborate the proposed analysis.

Enhancement of Ferroelectricity in 5 nm Metal-Ferroelectric-Insulator Technologies by Using a Strained TiN Electrode.

In this work, the ferroelectric characteristic of a 5 nm Hf0.5Zr0.5O2 (HZO) metal-ferroelectric-insulator-semiconductor (MFIS) device is enhanced through strained complementary metal oxide semiconductor (CMOS)-compatible TiN electrode engineering. Strained TiN top-layer electrodes with different nitrogen (N) concentrations are deposited by adjusting the sputtering process conditions. The TiN electrode with 18% N exhibits a compressive characteristic, which induces tensile stress in a 5 nm HZO film. A device with 18% N in TiN shows a higher remanent polarization (2Pr) and larger capacitance value than the compared sample, indicating that the strained TiN is promising for enhancing the ferroelectricity of sub-5 nm HZO devices.

Stretchable Transparent Supercapacitors for Wearable and Implantable Medical Devices (Adv. Mater. Technol. 1/2022)

Biocompatible Supercapacitor Using a novel microfabrication approach based on anodic aluminum oxide templates, Guoguang Rong, Mohamad Sawan, and co-workers fabricate a biocompatible supercapacitor in article number 2100608, with a large capacitance value, as well as good transparency, stretchability, and biocompatibility. This supercapacitor is intended to be used as a power source for flexible printed circuit to stimulate the brain's neural tissues.

A Bulk-Capacitance Reduction Method Using Self-Driven Thyristor for AC–DC Converters

Universal serial bus power delivery fast chargers equipped with wide-bandgap devices are driven to higher power density and efficiency. The indispensable high-voltage bulk capacitors used to smooth the rectifier output could take 40% of the total system volume due to the large capacitance value required. This letter discussed a capacitor reduction method using a self-driven thyristor scheme comprised of only three components in total. No extra control circuit is needed. Circuit analysis and design equations are presented, and the design results are implemented in a 60-W GaN-based active-clamp flyback converter. The measurement results on the prototype show a 36.4% reduction of the bulk-capacitor size with similar efficiency compared to the conventional solution.

The Influence of Anion Structure on the Ionic Liquids/Au (100) Interface by Molecular Dynamics Simulations.

The microstructure of electrical double layers (EDLs) of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4), 1-butyl-3-methylimidazoliumhexafluorophosphate ([Bmim]PF6), and 1-butyl-3-methylimidazoliumbis (trifluoromethylsulfonyl) imide ([Bmim]TFSI) were studied by quantum chemical calculation and molecular dynamics simulation. For the set of ionic liquids investigated here, we found some interesting universal laws due to differences geometry and electronic structure of anions. We show that the morphology of the three anions on the electrode surface is different due to the different geometric structure. The plane formed by the bottom three atoms of the symmetrically tetrahedral BF4- and the bottom atom of the symmetrically octahedral PF6- face the electrode whether the electrode is charged or not, while the conformation of twisted V-shaped TFSI- changes with different surface charges on the electrode. Meanwhile, we also demonstrate that the energy of highest occupied molecular orbital (EHOMO), the energy of lowest unoccupied molecular orbital (ELUMO) and their energies gap (ΔE) are very interesting due to different electronic structure of anions. Specially, the EHOMO, ELUMO, and ΔE were related to the electronegativity of the central atom in the case of the same symmetry on the neutral surface. The more electronegative the central atom is, the lower EHOMO, ELUMO and higher ΔE values are. However, on the charged surface, the interaction between anion and electrode is opposite to ΔE. Moreover, different arrangements of anion and cation are related to the interaction between particles. The stronger interaction leads a double-row structure and the weak interaction lead worm-like and island patterns on Au (100) surface. In general, we observed that the higher ΔE cause stronger interaction, which lead to different patterns on Au (100) surface. Meanwhile, we also confirmed that the stronger interaction between particles and electrode lead to the thinner effective EDL and a large differential capacitance value. These results provide a new perspective for double-layer structure in atomic and molecular level. This is helpful to deepen the understanding of the interface phenomena and characteristics of [Bmim]BF4, [Bmim]PF6, and [Bmim]TFSI on Au (100) system and provide theoretical basis for the application of these kind of systems.

Influence of Various Concentrations of Cetyltrimethylammonium Bromide on the Properties of Nickel Oxide Nanoparticles for Supercapacitor Application

In this paper, the impact of the crystallite sizes of nickel oxide nanoparticles (NiO NPs) on their efficiency for electrochemical capacitors (EC) has been investigated. NiO NPs were prepared without and with low and high concentrations (0.02[Formula: see text]M and 0.1[Formula: see text]M) of cetyltrimethylammonium bromide (CTAB) using the hydrothermal process that represent NiO, NiO-1, NiO-2, respectively. The crystallite size of NiO, NiO-1, NiO-2 NPs was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) analysis. The thermogravimetry/differential thermal analysis (TG/DTA) was used to investigate the thermal observation of as-prepared precursor to transform as NiO NPs. HRTEM revealed spherical seed-like morphologies, which consist of aggregated NiO-1 NPs with an average particle size of 9[Formula: see text]nm. The NiO-1 shows the large specific capacitance value of 168[Formula: see text]Fg[Formula: see text] at a current density of 0.5[Formula: see text]Ag[Formula: see text] compared with other NiO and NiO-2 NPs. The study suggests that the low concentration of surfactant CTAB of NiO NPs plays an important role in supercapacitor applications because of the smaller crystallite sizes of the materials as well as a large number of active sites for faradic reaction.

Stretchable Transparent Supercapacitors for Wearable and Implantable Medical Devices

AbstractRecent advances in wearable bioelectronics have driven various healthcare applications, such as the monitoring, sensing, and treating of various diseases. However, unsustainable batteries and toxic power solutions hinder their use at the skin interface or in vivo. As a promising power solution, supercapacitors have attracted the attention of researchers. However, there are still several drawbacks, such as the transparency, stretchability, biocompatibility, and flexibility of these materials, when these energy reservoirs are used as power supplies for skin‐interfaced electronics. In this work, a novel microfabrication approach for fabricating supercapacitors using anodic aluminum oxide templates is presented. In this work, a large capacitance value of 15.02 mF cm−2, as well as good transparency, stretchability, and biocompatibility are obtained. Thus, it is verified that the proposed supercapacitors are suitable as skin‐interfaced power solutions.

Electrochemical performance of N‐doped superporous activated carbons in ionic liquid‐based electrolytes

The electrochemical performance of nitrogen-doped and non-doped superporous activated carbons as electrodes for supercapacitors was assessed in organic and ionic liquid-based electrolytes. The nitrogen functionalization was carried out through post-modification treatments at mild conditions to produce N-doped activated carbons that preserve the microporosity of the pristine carbon material. The electrodes based on these materials provide large capacitance values (up to 150–180 F/g) in both 1 M Pyr14TFSI/PC and 1 M Pyr14BF4/PC due to their tailored porous texture, given by their well-developed microporosity and low mesopore volume. The electrochemical double layer capacitors based on these materials displayed outstanding capacitance (37–40 F/g and 14 F/cm3) and energy values (44–48 Wh/kg and 16–17 Wh/L). The nitrogen-doped activated carbons evidence high stability at positive and negative polarization potentials due the presence of specific N functionalities. The results prove that surface chemistry of carbon materials plays a key role on their degradation under high operation voltage conditions. The durability of the devices can be improved by doping carbon electrodes with selected nitrogen groups, such as nitrogen heterocycles and amine-like surface functionalities.

Capacitance Measurement of Cerium Oxide Thin Film Capacitors

IntroductionCerium oxide (CeOx) is an attractive material for large volume on-chip decoupling capacitors, owing to its high dielectric constant (k) of 28. Commonly, a definite frequency dispersion in the small-signal capacitance measurement is observed in the frequency sweep, and larger capacitance values can be obtained at low frequency in the kHz range. The dielectric relaxation is reported to originate from the interface polarization between the polycrystalline grains in the films. In this work, the thickness-dependent polarization and the capacitance measurement under a DC voltage application are characterized.Fabrication processCeOx films with thicknesses from 8 to 20 nm were deposited by e-beam evaporation on an n+Si substrate with a W layer atop. Another W layer was deposited on CeOx layers and patterned to form electrodes. After the Al back contact formation, the samples are annealed at 420oC.ResultsFig. 1 shows the frequency dispersion of the capacitors with different CeOx thicknesses measured at 0 V. The dielectric relaxation frequency shifts to higher frequency while thinning the thickness, which is useful for capacitor application. The transient current upon 1 V application is shown in fig. 2. After a high charge current, one can observe a decay in the transient current, indicating the delay in the polarization. The capacitance of the samples can be obtained by taking the integral of the charge current and is shown in fig. 3. Comparable capacitance values were obtained with the small-signal measurements. 2 to 3 times higher capacitance values can be achieved with respect to the ionic polarization.ConclusionHigh capacitance values measured in the small-signal setup were confirmed by direct current measurement by DC voltage application. An even higher capacitance can be obtained with the thinner film.

Charge transport mechanism in reduced graphene oxide/polypyrrole based ultrahigh energy density supercapacitor

In the present work, charge transport in graphene/polypyrrole supercapacitor which is relatively unexplored so far, is investigated to understand the respective contributions of graphene and polypyrrole, particularly, in the charge transport and storage capacity to improve the device properties. It is seen that the role of graphene is to increase the surface area and the charge carriers are mainly stored in the polypyrrole-modified graphene sheet, while the transport occurs primarily through polypyrrole backbone via overlapping large polaron tunneling mechanism. Electrochemical supercapacitor has been fabricated using this layered composite as electrode material to obtain large value (~ 931 F/g) of specific capacitance. Furthermore, the optimized material demonstrated an excellent energy density (46.6 Wh kg−1) at an ultra-high power density (469 W kg−1), indicating a promising potential for industrial applications as energy storage device.

Ultrawide Bandwidth Electromagnetic Wave Absorbers Using a High-capacitive Folded Spiral Frequency Selective Surface in a Multilayer Structure

A high-capacitive frequency selective surface (FSS) with a new structure of folded spiral conductors is proposed as the small-array periodicity and low-frequency resonance FSS for ultra-wide bandwidth absorbers in a multilayer structure. Due to the folded structure with long effective segments and a small gap, a large value of capacitance for the lowest resonating frequency is obtained. Through a combination of the high-capacitive spiral FSS with other conventional FSSs (square loop, square patch) with a medium- and high-frequency resonance, an ultra-wide absorption bandwidth (4.7–50.0 GHz for −10 dB reflection loss) is designed with a small total thickness of 7.0 mm, which is close to the theoretical limit (6.7 mm). Admittance analysis is conducted for better insight into the optimization procedure. The free space measurement with a test sample prepared by the screen printing method also demonstrates a wide-bandwidth absorption result (5.2–44.0 GHz for −10 dB reflection loss, total thickness = 6.5 mm), which is in good agreement with the simulation result. In addition, the angular stability of the proposed wide-bandwidth absorber is discussed for both TE and TM polarizations in association with unit cell periodicity and grating lobes.

Influences of Annealing on the Electrical Properties of Ba0,5Sr0,5TiO3

The research aims to investigate influences of annealing on the electrical properties of Ba0,5Sr0,5TiO3. Ba0,5Sr0,5TiO3 material which was annealed at 900°C for 1, 2 and 4 hours has better mechanical properties. It needs investigation for its electrical contribution, namely the correlation between grain and grain boundaries to values of resistance and capacitance. The changing of electrical properties was controlled by grain, grain boundary and the area between the sample and contact. The electrical properties of Ba0,5Sr0,5TiO3 were investigated by impedance spectroscopy in the room temperature. This method is able to separate the electrical and dielectric properties of the grain, grain boundary and the area between contact with the sample. ZsimpWin software was used to find out the equivalent electrical circuit, the resistance and capacitance value. It was observed that with the increase in annealing time the small grains resistance, the grain boundaries resistance, and the large grain capacitance value also increases. The resistance values of small grains and large grains were smaller than the grain boundaries resistance. The value of capacitance-resistance of the small grains and large grains were obtained values that tend to be smaller.

High Q-factor near infrared and visible Al2O3-based parallel-plate capacitor kinetic inductance detectors.

We designed, fabricated and characterized parallel-plate capacitor lumped-element kinetic inductance detectors (LEKIDs) to operate at near-infrared and optical wavelengths (0.3 -1 μm). The widely used interdigitated capacitor is replaced by a parallel-plate capacitor which, for a given resonance frequency, has a larger capacitance value within a much smaller space allowing to strongly reduce the size of the pixels. The parallel-plate capacitor LEKID array comprises 10 × 10 pixels. The inductive meander is patterned from stoichiometric 52 nm-thick TiN film (Tc ≈4.6 K). The parallel-plate capacitor is made of a TiN base electrode, Al2O3 dielectric and Nb upper electrode. More than 90 resonances out of 100 within the 0.994-1.278 GHz band were identified. The resonances exhibit internal Q-factors up to ∼370 000 at 72 mK. The array was illuminated using a white light and 890 nm monochromatic near infrared LEDs. The estimated quasiparticle lifetime is τqp≈13 µs.

Minimization of Switched Capacitor Voltage Ripple in a Multilevel Dodecagonal Voltage Space Vector Structure for Drives

A multilevel dodecagonal voltage space vector generation scheme for variable-speed drive applications with single-dc-link operation requires a large value of capacitance for cascaded H-bridge (CHB) filters, when operated at lower speeds. In existing schemes, the multilevel dodecagonal structure is obtained by cascading a flying capacitor inverter with a CHB. In this paper, a new scheme has been proposed to minimize the capacitance requirement for full speed operation by creating vector redundancies using modular and equal voltage CHBs. Also, an algorithm has been developed to optimize the selection of vector redundancies among the CHBs in order to minimize the voltage ripple of the floating capacitors. The proposed algorithm considers instantaneous capacitor voltages and phase currents for optimal selection of vector redundancies. A mathematical model for capacitor voltage deviation is presented, and the effectiveness of the proposed algorithm is verified in both the simulation and the experiment.