Electrical Sheet Research Articles

Multiparameter Modeling and Analysis of Mechanical Cutting Process of Grain-Oriented Silicon Steel

The process of mechanical cutting of magnetic materials has many advantages in the form of high efficiency, no generation of thermal stresses or the possibility of shaping materials taking into account long cutting lines. In the literature, there are models that allow to control the technological quality of the mechanical cutting process, e.g. in terms of the obtained quality of the cut surface. However, there is a lack of data on the selection of technological parameters of the mechanical cutting process of grain-oriented silicon electrical sheets in terms of the obtained quality of the cut surface and the obtained magnetic properties of the workpiece. The paper presents a solution to the gradient optimization problem combining issues from the field of structural and magnetic analyzes. Using obtained relationships and results, it is possible to control cutting process to obtain high cut surface quality with minimum deterioration of magnetic properties.

Enhanced thermoelectric performance of graphene based nanocomposite coated self-powered wearable e-textiles for energy harvesting from human body heat.

The demand for highly flexible and self-powered wearable textile devices has increased in recent years. Graphene coated textile-based wearable devices have been used for energy harvesting and storage due to their outstanding mechanical, electrical and electronic properties. However, the use of metal based nanocomposites is limited in textiles, due to their poor bending, fixation, and binding on textiles. We present here reduced graphene oxide (rGO) as an n-type and conductive polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as a p-type material for a wearable thermoelectric nanogenerator (TEG) using a (pad–dry–cure) technique. We developed a reduced graphene oxide (rGO) coated textile-based wearable TEG for energy harvesting from low-grade human body heat. The conductive polymer (PEDOT:PSS) and (rGO) nanocomposite were coated using a layer by layer approach. The resultant fabric showed higher weight pickup of 60–80%. The developed textile based TEG device showed an enhanced Seebeck coefficient of (25–150 μV K−1), and a power factor of (2.5–60 μW m−1 K−1). The developed TE device showed a higher potential to convert the low-grade body heat into electrical energy, between the human body temperature of (36.5 °C) and an external environment of (20.0 ± 5 °C) with a temperature difference of (2.5–16.5 °C). The wearable textile-based TEG is capable of producing an open circuit output voltage of 12.5–119.5 mV at an ambient fixed temperature of (20 °C). The rGO coated textile fabric also showed reduced electrical sheet resistance by increasing the number of dyeing cycles (10) and increased with the number of (20) washing cycles. The developed reduced graphene oxide (rGO) coated electrodes showed a sheet resistance of 185–45 kΩ and (15 kΩ) for PEDOT:PSS–rGO nanocomposites respectively. Furthermore, the mechanical performance of the as coated textile fabric was enhanced from (20–80 mPa) with increasing number of padding cycles. The thermoelectric performance was significantly improved, without influencing the breath-ability and comfort properties of the resultant fabric. This study presents a promising approach for the fabrication of PEDOT:PSS/rGO nano-hybrids for textile-based wearable thermoelectric generators (TEGs) for energy harvesting from low-grade body heat.

Unveiling the Mechanism of Polymer Grafting on Graphene for Functional Composites: The Behavior of Radicals.

Polymer-graphene composites have attracted significant attention; however, their formation mechanisms are a focus of debate. This work tries to clarify how grafting occurs on graphene by electron spin resonance techniques. As a result, two pathways are found. One passes through the radicals formed by cleaving CO bonds on graphene are transferred to monomers, then grafting and polymerization proceed. Another mechanism passes through the oxy-radicals, which react with monomers in solution and finally react with carbon radicals on graphene. Based on the mechanism, various types of polymer-graphene composites are prepared, and applied to electrical conductive sheets, basic catalysts, and acidic catalysts.

Pyrolytic carbon from Novolac Epoxy resin compressed before photocrosslinking and pyrolysis

The so-called SU-8 formulation, originally designed as a negative photoresist, has become the gold standard for the fabrication of microelectromechanical systems (MEMS) due to its relatively versatile processability and to the unique set of properties of the carbon obtained from pyrolysis of the patternable Bis-Phenol A Novolac Epoxy (BPNE) oligomer contained therein. Here, we investigate the possibility of increasing the degree of graphitization and electrical conductivity of BPNE-derived carbon by mechanically compressing the uncured oligomer pre-pyrolysis. BPNE sheets were casted, compressed and photocrosslinked to “freeze” the material in a strained configuration before carbonization. The electrical sheet resistance was determined using the four-point probe technique. The relative sp2/sp3 content and the degree of crystallinity were compared by Raman and XRD spectroscopy. It was hypothesized that applying compressive loads of up to 2000 kg at 90°C would suffice to increase the crystallite size and the mesoscale order of the percolated graphenic carbon network by promoting the alignment of the aromatic segments from the phenolic groups before pyrolysis. However, negligible variations in the resistivity and sp2-carbon microstructural features were observed when compressing millimetric sheets of BPNE as compared to uncompressed samples, suggesting that higher forces and temperatures may be required to synthesize BPNE-derived glass-like carbon materials with a slightly more graphitic character.

Enhancing the Utilization of Porous Li4Ti5O12Layers for Thin-Film Lithium-Ion Batteries

Thin-film lithium-ion batteries (TFBs) are promising components for powering rigid and mechanically flexible electronic devices. The production of such all-solid-state power units is yet complex and cost-intensive, and the performance is to be improved. Because binders are often absent in TFBs, it is a key issue to retain the mechanical stability and reversible discharge capacities upon mechanical bending. One approach to reduce contact losses upon cell-bending may be the fabrication of electrodes with controlled residual porosities. The remaining voids could buffer occurring volume changes during cycling of typical cathode materials. To systematically approach the fabrication of long-living high-performance flexible TFBs, this work addresses the relationship between different residual porosities of pure TFB electrodes and their electrochemical performance in flat TFB systems. Crystalline and phase-pure Li4Ti5O12 (LTO) thin-film electrodes were deposited in situ with the flame spray pyrolysis technique and compressed at two different pressures. Zero-strain LTO has been chosen as a model material because it enabled us to understand the sole impact of porosity on electrochemical performances without interfering volume changes. Our results showed that denser LTO particle networks were accompanied by a larger number of LTO particle contacts. Also, the LTO contact densities to the neighboring interfaces in a TFB cell have increased. The improved electrode contacting led to reduced electrical sheet resistivities and significantly increased practicable capacities. Future projects will require the substitution of LTO with high-voltage cathode materials to maximize energy densities. Cycling under statically and dynamically bent condition will answer whether tuned residual porosities are useful for the production of long-living flexible TFBs.

Flexible graphene paper electrode prepared via polyvinyl alcohol-assisted shear-exfoliation for all-solid-state polymer supercapacitor application

Herein, an environmentally-benign, facile, efficient, low-cost, scalable fabrication process of achieving flexible graphene paper electrode at ambient conditions is reported. By means of high-shear exfoliation of graphite in aqueous polyvinyl alcohol (PVA), the graphene/PVA dispersion is prepared. Various characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, etc.) confirm that the resulting dispersion is with the presence of high-quality, single to few-layered graphene sheets with thickness up to 1.68 nm, lateral size of 0.5–2 μm, and low defect density (ID/IG = 0.09). Further, the applicability of the in-situ exfoliated graphene/PVA dispersion is demonstrated for the fabrication of flexible conductive paper electrodes through a simple intermittent soaking-drying approach. The graphene paper electrode possesses an electrical sheet resistance of 15 Ω sq−1, without any additional annealing treatment and conductive additives. Finally, the graphene paper electrode is integrated with ionic-liquid incorporated PVA polymer electrolyte to develop the all-solid-state supercapacitor. It imparts a considerable specific capacitance of 222.96 F g−1 along with ~60% capacitance retention and ~100% coulombic efficiency after 6000 charge–discharge cycles. Meanwhile, the polymer electrolyte exhibits a remarkable ionic conductivity (4.63 × 10−4 S cm−1) together with a wide electrochemical stability window (5.1 V), favorable for device applications. The unique interwoven nanoporous conductive network of PVA-stabilized exfoliated graphene provides fast diffusion pathways to electrolyte ions, thus significantly enhancing the charge-storage performance.

Simple analytical method for determining electrical resistivity and sheet resistance using the van der Pauw procedure

This work reports an analytical method for determining electrical resistivity (ρ) and sheet resistance (RS) of isotropic conductors. The method is compared with previous numerical solutions and available experimental data showing a universal behavior for isotropic conductors. An approximated solution is also reported allowing one to easily determine ρ and RS for samples either with regular or arbitrary shapes.

Binder‐Free High‐Performance MXene Supercapacitors Fabricated by a Simple Electrospray Deposition Technique

AbstractIn this work, an electrospray deposition (ESD) technique is applied to fabricate binder‐free porous 2D MXene (Ti3C2Tx) electrodes for supercapacitor applications. As a result of the crumpling of MXene flakes induced by the capillary force during drying, a porous structure is formed between MXene flakes within the electrode which leads to the formation of channels for rapid ion‐diffusion. Together with binder‐free networks of highly electrical conductive MXene sheets, these ion diffusion channels greatly improve the rate capability of the electrospray MXene electrode. Cyclic voltammetry measurements show that micron‐thickness electrodes retain their capacitive rectangular‐shaped curves even at a very high scan rate of 10 000 mV s−1 in KOH electrolyte. A specific capacitance as high as 400 F g−1 is also recorded in H2SO4 electrolyte and this high specific capacitance maintains 85% of its value when the scan rate is increased to 1000 mV s−1. Furthermore, the electrospray MXene electrode shows good cycle stability in H2SO4 without a binder. About 90% of the capacitance is maintained after 10 000 charge–discharge cycles at a current density of 15 A g−1. All of these results show that the ESD MXene electrodes are a promising candidate for supercapacitor applications that require both high capacitance and enhanced rate capability.

The Effect of Structural Material Parameters on the Operational Characteristic of Traction Drives for EV Applications

In this article, the effect of structural material parameters of nongrain-oriented (NO) electrical steel on the driving cycle losses and torque-speed characteristics of electrical traction drives for electric vehicle (EV) applications is studied. The operating point distribution in different driving cycles affects the iron losses and magnetization behavior. As a result, the ideal material choice not only depends on the machine design and topology but also on the application requirements. Structural material parameters of electrical steel, that is, alloying, sheet thickness, grain size, and crystallographic texture, are measures to modulate the magnetic properties. Their effect on iron-loss components is studied for seven industrial NO electrical steel grades. Two traction drives and four driving cycles are evaluated with respect to the structural material parameters as application examples.

THE EFFECT OF PEPPERMINT AROMATHERAPY ON REDUCING PAIN IN POST OPERATING SECTIO CAESAREA PATIENTS AT LEUWILIANG HOSPITAL, BOGOR

A preliminary study conducted on December 9, 2017 at the Leuwiliang Hospital in Bogor District from 9 respondents who experienced pain in the sectio Caesarea post obtained 5 respondents with severe controlled pain criteria and 4 respondents with moderate pain. The 9 respondents after being given peppermint aromatherapy showed that 5 respondents with severe pain criteria controlled, experienced changes in the level of pain to moderate pain. While the other 4 respondents with pain criteria were experiencing changes 3 including mild pain and 1 other respondent remained. From these data, it is possible that there is a difference in the level of pain before giving peppermint aromatherapy and after peppermint aromatherapy administration. This study aims to determine the effect of peppermint aromatherapy on changes in pain levels in caesarean section surgical patients in the Bogor District. The Type of this research is Quasi experiment with non-rendometed pretest and posttest control group design method. The location of the study was at the Leuwiliang Hospital Bogor on April 13, 2018. The number of samples was 32 respondents, patients with postoperative caesarean section with purposive sampling. The tools used in data collection are electric aromatherapy furnaces and observation sheets. The data analysis technique is bivariate analysis with the SPSS program. The results of this study reported differences in the level of pain before and after treatment of peppermint aromatherapy in the intervention group in patients with postoperative caesarean section with a P value = 0,000 (<0.05) with an average decrease of 4.00. There was no difference in pain level at 6 hours and 12 hours post anesthesia in the control group with a P value = 0.317 (> 0.05). Tthe conclusion is that the influence of peppermint aromatherapy on changes in pain level in patients with sectio caesarean surgery P value = 0,000 (<0.05).

Performance Characteristics of Single-Phase Self-Excited Induction Generators with an Iron Core of Various Non-Grain Oriented Electrical Sheets

This paper deals with the computation of the performance characteristics of the single-phase self-excited induction generator by field–circuit method. It presents and compares previously unpublished results—self-excitation and no-load characteristics of the generator for different rotor speeds, and complete load steady-state performance characteristics for various types of the core materials. The discrepancies between the performance characteristics of the generator for the catalog’s magnetization curves of different types of electrical sheets and for an actual magnetic core of the generator for self-excitation transients and load steady-state are presented. The results may be useful for designing new constructions of single-phase self-excited induction generators.

THE IMPACT OF SHEAR GAP SIZE ON THE QUALITY OF THE SHEARED SURFACE IN ELECTRICAL STEEL SHEET BLANKING

The quality of the sheared surface when blanking, also known as die-cutting, is the result of several factors. Based on current knowledge about blanking, the following technological parameters – shear gap size, blunting of the shearing tool, lubrication in the shearing process, and deformation rate – can be considered as decisive parameters on the quality of the sheared surface. The main material characteristics include yield strength, tensile strength, ductility, and ferrite grain size. The paper is focused on the influence of the shear gap on the quality of the shear surface of electrical sheets with different chemical composition and different mechanical properties. The quality of the cutting surface was characterized by the size of the plastic cutting area. The relationships between the size of the shear gap, which ranged from 1 to 7% of the thickness of the cut material and the size of the plastic shear area, were evaluated and measured macroscopically.

Effects of Manufacturing Processes on Core Losses of Electrical Machines

Manufacturing processes such as cutting, welding and shrink fitting are known to degrade the magnetic properties of the electrical sheet during the manufacturing of electrical machines. These effects are often neglected at the design stage and lead to large errors in the simulated and measured core losses of the electrical machine. This article studies the comparative impact of different manufacturing processes on the stator core losses of a typical industrial motor. Both simulations and measurements indicate a significant impact of manufacturing processes on the stator core losses. A dummy blocked rotor test setup is used to measure the stator core losses. As a result of different manufacturing processes, the stator core losses increased by 23% in the studied machine at the rated condition. The effect on the stator core losses was higher at lower flux levels. Finally, it was shown that the inclusion of the effect of manufacturing processes significantly improved the simulation accuracy of the core losses. A quantification and segregation of the effect of cutting, welding and shrink fitting is also presented for the studied machine.

Improvement in structural, electrical, and optical properties of Al-doped ZnO nanolayers by sodium carbonate prepared via solgel method

The significant improvement in crystallinity, electrical, and optical properties of aluminum-doped zinc oxide (AZO) thin films was attained by Na doping. Both Al and Na contents were introduced into ZnO host via facile and cost-effective solgel method. Ultra-thin films of Na-doped AZO (NAZO), with thickness of about 40 nm, were deposited on glass substrates via spin-coating technique. The obtained results showed low sodium incorporation reduces the crystal strain which in turn leads to increase crystallite size from 31 nm for AZO to 49 nm for 2 at% Na-doped AZO layer. In addition, 2 at.% of Na doping, that was determined as an optimum level of doping concentration, decreased the macroscopic surface roughness (MRs) without notable changes in surface micro-cracks, leading to remarkable enhancement of the layer conductivity (about 54%). On the other hand, high concentration of sodium content (10 at%) increased the crystal strain and reduced the crystallinity order of AZO layer which resulted in high MRs and also high electrical sheet resistance. Optical dispersion curve and real and imaginary parts of dielectric constant were obtained using our precise method. More interestingly, 2 at% of Na doping led to an increase in transparency of AZO layer in the visible range, while its extinction coefficient (light power absorption) was enhanced which can be regarded as advantage for such thin films. Therefore, the optimum Na content can provide higher optical absorption even with higher transparency by reducing the light scattering and reflection. This finding provides a useful procedure to prepare transparent oxide semiconductor layers with noticeable light absorption, which is very interesting for various applications such as solar cells and anti-reflection coatings.

Electronic Structure of Nitrogen- and Phosphorus-Doped Graphenes Grown by Chemical Vapor Deposition Method.

Heteroatom doping is a widely used method for the modification of the electronic and chemical properties of graphene. A low-pressure chemical vapor deposition technique (CVD) is used here to grow pure, nitrogen-doped and phosphorous-doped few-layer graphene films from methane, acetonitrile and methane-phosphine mixture, respectively. The electronic structure of the films transferred onto SiO2/Si wafers by wet etching of copper substrates is studied by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy using a synchrotron radiation source. Annealing in an ultra-high vacuum at ca. 773 K allows for the removal of impurities formed on the surface of films during the synthesis and transfer procedure and changes the chemical state of nitrogen in nitrogen-doped graphene. Core level XPS spectra detect a low n-type doping of graphene film when nitrogen or phosphorous atoms are incorporated in the lattice. The electrical sheet resistance increases in the order: graphene < P-graphene < N-graphene. This tendency is related to the density of defects evaluated from the ratio of intensities of Raman peaks, valence band XPS and NEXAFS spectroscopy data.

The Onset of 3D Magnetic Reconnection and Heating in the Solar Corona

Abstract Magnetic reconnection, a fundamentally important process in astrophysics, is believed to be initiated by the tearing instability of an electric current sheet, a region where magnetic field abruptly changes direction. Recent studies have suggested that the amount of magnetic shear in these structures is a critical parameter for the switch-on nature of magnetic reconnection in the solar atmosphere, at large spatial scales. We present results of visco-resistive magnetohydrodynamic simulations of magnetic reconnection in 3D current sheets with conditions appropriate to the solar corona. We follow the evolution of the linear and nonlinear 3D tearing instability. We find that, depending on the parameter space, magnetic shear can play a vital role in the onset of significant energy release and plasma heating. Two regimes in our study exist, dependent on whether the current sheet is longer or shorter than the wavelength of the fastest growing mode, thus determining whether subharmonics are present in the actual system. In one parameter regime, where the fastest growing parallel mode has subharmonics, the subsequent coalescence of 3D plasmoids dominates the nonlinear evolution, with magnetic shear playing only a weak role in the amount of energy released. In the second parameter regime, where the fastest growing parallel mode has no subharmonics, only strongly sheared current sheets, where 3D effects are strong enough, show any significant energy release. We expect both regimes to exist on the Sun, and so our results have important consequences for the question of reconnection onset in various solar physics applications.

Thin Films in Triboelectric Nanogenerators for Blue Energy Harvesting: Fabrication, Characterization, and Modeling

Renewable energy attracts many researchers as the non-renewable one has negative environmental impacts and limited availability. One of the main types of renewable energy is the blue energy where electricity is generated by water waves using triboelectric nanogenerators (TENGs). Thin films play an important role in the performance and therefore the efficiency of TENGs as they represent the electrodes between which electrons move producing electricity. In order to increase the generated electricity from TENGs, the properties of these electrodes should be modified. Therefore, in this paper, nano- and micro-size thin films are fabricated and characterized by measuring the geometrical parameters and electrical properties. Thin films are fabricated using aluminum with thicknesses 0.5 μm and 1.5 μm on acrylic substrate and 0.5 μm copper film on different types of dielectric materials including PVC and polystyrene. Atomic force microscopy is used to measure the geometrical parameters of the fabricated films including thickness and surface roughness. Also, Gwyddion software is used for the grain size evaluation. On the other hand, Keithley is used for measuring the electrical properties including electrical conductivity and sheet resistance. It is found that the electrical conductivity of aluminum films is inversely proportional to the thickness. The corresponding measured values of the electrical conductivity of the fabricated thinner and thicker aluminum films equal 1.7 x 107 (Ω.m)-1 and 1.4×107 (Ω.m)-1, respectively. Whereas, the electrical conductivity of the fabricated copper film equals 8.8×107 (Ω.m)-1. In addition, the temperature effects on the electrical conductivity are studied. Finally, simulation of a TENG using COMSOL software is accomplished in order to evaluate the electrical outputs of potential, charge, and energy.

Fatigue and the electrical resistance of silver nanowire networks

Silver nanowire networks on polymeric substrates have applications for flexible displays. However their electrical sheet resistance, Rs, increases with increasing flexural strain cycles. A percolation model gives Rs=Rn(c¯)−2, where c¯ is the mean network coverage and Rn is the network resistance, determined by the dimensions and electrical resistance of the individual nanowires. Network resistance is independent of coverage and increases with strain cycles, showing two clear regimes following the onset of damage after about 100 cycles. The results indicate that fatigue damage is dominated by a loss in network connectivity rather than a change in the electrical properties of individual nanowires.

Indium-free large area Nb-doped SnO2 thin film as an alternative transparent conducting electrode

Niobium doped tin oxide (NTO) thin film deposited via facile chemical spray pyrolysis technique on to a large area (10 × 10 cm2) glass substrate exhibits better optical and electrical properties. The structural, surface, optical and electrical properties were analyzed by means of XRD, XPS, AFM, SEM-EDS, Hall Effect, and four-point probe techniques. The deposited NTO thin film was found to possess a maximum average transmittance value around 75% due to enhanced optical bandgap (3.77 eV) by Nb-dopant effect. The variation of sheet resistance of the large area (10 × 10 cm2) coated thin film over the entire region was studied at every 1 × 1 cm2 area. The film doped with 1.5 wt% of Nb content showed improved carrier concentration (9.33 × 1019 cm-3), higher free carrier mobility (39.4 cm2/V·s), improved electrical resistivity (1.69 × 10-3 Ω cm) and low sheet resistance (26.5 Ω/□). The temperature dependent electrical measurement was carried out from 200 to 450 °C in steps of 50 °C to understand the resistance stability of the film. In addition to these studies, we report the surface work function of NTO thin film to identify its suitability in optoelectronic devices. The estimated electrical properties confirm the substitution of Nb5+ in Sn site of SnO2 lattice. Our results indicate the optimized NTO thin film to possess promising optical and electrical transport properties to serve as a better indium-free alternate transparent conducting electrode in various optoelectronic devices.

Processing–structure–property relationship in direct laser writing carbonization of polyimide

AbstractDirect laser writing carbonization (DLWc) of polyimide has recently emerged as a versatile method for facile fabrication of a variety of functional devices. Up‐to‐date, there is still a lack of comprehensive and in‐depth experimental studies to understand the processing‐structure–property relationship involved in this promising technique. With assistance of methylene blue adsorption as an in situ porous structure characterization method along with scanning electron microscopy, Raman scattering spectroscopy, X‐ray photoelectron spectroscopy, and electrical property measurements, we systematically investigate the multiscale structure evolution and the electrical sheet resistance of the carbon lines fabricated by DLWc at varied laser processing conditions. The key processing parameters being investigated included: laser power (P), laser beam scanning speed (S), distance of laser beam waist to the surface of polyimide film (D), and their combined effect—the averaged areal laser energy density—(E). Quantitative relationships are established between these processing parameters and the specific surface area, the porosity, the degree of perfection of the layered carbon or graphitic basic structure units, as well as the electrical sheet resistance of the carbon lines created by DLWc. The comprehensive and quantitative processing‐multiscale structure–electrical property relationships for DLWc established in this study expect to be useful for better understanding the complicated photo‐thermally induced polyimide pyrolysis/carbonization process.