Surface Resistance Measurements Research Articles

Influence of nitrogen ion implantation on surface charge accumulation and dissipation of polytetrafluoroethylene

To suppress the accumulation of charge on the surface of polytetrafluoroethylene (PTFE) material, radio frequency nitrogen plasma was generated to perform plasma immersion ion implantation (PIII) on the PTFE surface to improve its surface properties. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), water contact angle measurement, surface resistivity measurement and surface potential attenuation measurement were performed on the samples of PTFE material before and after injection to analyze the changes in surface composition and physical properties of PTFE samples after ion implantation treatment. Based on the theory of isothermal surface potential attenuation, the energy levels and density distributions of the surface traps were calculated. The results show that after nitrogen ion implantation, the main change in the chemical composition of the surface of the PTFE material is the destruction and conversion of its own molecular structure, and part of the CF2 structure is transformed into the CF and CF3 structures, resulting in shallower trap levels on the sample surface. The results also show that the water contact angle rose to about 140°, which is about 27° higher than that of the unprocessed sample. The surface resistivity drops to 3×1015 Ω, which is two orders of magnitude lower than that of the unprocessed samples. After 1 min of corona discharge on the surface, the amount of accumulated charge on the surface of the PTFE material processed with nitrogen ion implantation decreased, and the rate of dissipation increased. This is because the lower surface trap level is conducive to surface charge trapping, and the reduction in surface resistivity also promotes the dissipation process of surface charge along the surface. The curve of trap level distribution on the surface of PTFE sample also confirmed this.

Improvement of the adhesion of conductive poly(m-toluidine) onto chemically reduced-wool fabrics.

Wool has disulphide bonds containing-hydrophobic external keratin layers, which act as a barrier for the modification through coating with hydrophilic materials. For that reason, in this work, to ensure a dense and homogenous conductive polymer coating onto the wool, the fabrics were subjected to the reduction process in the aqueous alkaline medium containing agents that can attack these disulphide bonds. Then, one of the polyaniline derivatives, poly(mtoluidine) (PMT), was coated onto wool by in situ polymerization of m-toluidine sulphate using ammonium persulfate (APS) as an oxidant. The effects of conditions, such as the composition of reduction-bath and types of dopants were investigated, on the mass increase (%) and surface resistivity of the composite. The reduction pretreatment of wool with sodium hydrosulphide significantly improved the coating density, conductivity, and colour shade of PMT on the surface, compared to an untreated one. The coating stability of PMT/wool composite was examined by rubbing test and detergent washing, through surface resistivity measurements. The changes in structural and surface properties of wool fabrics were determined with ATR-FTIR, contact angle, and optical microscopic techniques, respectively. The performance of PMT/wool composite was also examined in the electromagnetic shielding effectiveness (EMSE) measurements within 30 MHz-3 GHz.

Volume and Surface Resistivity Measurement of Insulating Materials Using Guard-Ring Terminal Electrodes

Recently, eco-friendly energy conversion policies have been being promoted through de-nuclearization and de-coal. For this purpose, a super grid should be built to optimize sustainable renewable energy resources such as solar and wind power. Accordingly, considering the various problems such as technology and cost, a system for efficient energy transmission is required. Hence, research is being actively conducted to apply it, owing to the development of the high voltage direct current (HVDC) system. Among HVDC systems, the cable system is extremely important, in addition to the measurement of the dielectric breakdown strength, space charge, and volume resistivity of insulating materials. The existing resistivity measurement method measures both the volume and surface resistivity using a three-terminal electrode that is used in the international standards of American Society for Testing and Materials (ASTM) D 257 and International Electrotechnical Commission (IEC) 60093. However, the circuit configuration differs depending on the measurement of the volume and surface resistivity; moreover, when a DC voltage is applied to the insulator, a charging current flows and there are multiple samples to be measured, which takes a considerable amount of time. Therefore, in this study, we proposed a new type of resistivity measurement system that is based on the existing three-terminal electrode system. Furthermore, we produced a system capable of simultaneously measuring the volume and surface resistivity. Finally, using this system, we compared and analyzed the volume and surface resistivity of five insulating materials.

Negative apparent resistivities in surface resistivity measurements

Apparent resistivity is traditionally defined as the resistivity of a hypothetical homogeneous half-space that would yield the same response as that measured over the real earth with the same acquisition parameters. Negative apparent resistivity contradicts this definition of apparent resistivity as we cannot physically attain a homogeneous medium with negative resistivity. However, we often encounter negative apparent resistivity in field data acquisition; it is regarded as the effect of measurement error or noise. In this paper, we re-investigated the idea that negative apparent resistivity, especially in the dipole-dipole measurement, can be caused by a natural geological structure even when the earth is isotropic and flat, and the survey line is straight. The results from 3D numerical modelling revealed that negative apparent resistivity in the dipole-dipole measurement can be encountered particularly when the resistivity contrast between the conductive body and background medium is extraordinarily high. Moreover, negative apparent resistivity can occur only when the current source is very close to one side of the conductive body, like in the mise-ả-la-masse case, and the potential dipole is placed at the opposite side of the body.

Fabrication and Characterization of MWCNTs by Syngas and Temperature Conditions

The morphologies, bulk densities, and synthesis yields of multi‐walled carbon nanotubes (MWCNTs) were analyzed by optimizing the catalyst, syngas, and synthesis temperature, which are key factors in the production of MWCNTs. In addition, MWCNTs were applied to polymer composites, and their electrical conductivities were evaluated through surface resistance measurements. The catalyst used in this process was a deposition precipitation method that offers favorable uniformity of loading through the liquid phase process and provides the advantage of controlling the shape using a support. Furthermore, physical and electrical analyses were performed in the range from 650 to 725°C using ethylene, butane, and liquefied petroleum gas (LPG) syngas. The results showed that the optimal synthesis yield and electrical conductivity of ethylene and butane were observed at 675°C, while those of LPG syngas were observed at 700°C. This implies that the aggregate diameter and bundle length tend to decrease under the most optimal conditions.

Ultralow Surface Resistance via Vacuum Heat Treatment of Superconducting Radio-Frequency Cavities

We report on an effort to improve the performance of superconducting radiofrequency cavities by the use of heat treatment in a temperature range sufficient to dissociate the natural surface oxide. We find that the residual resistance is significantly decreased, and we find an unexpected reduction in the BCS resistance. Together these result in extremely high quality factor values at relatively large accelerating fields Eacc ~20 MV/m: Q0 of 3-4x10^11 at <1.5 K and Q0 ~5x10^10 at 2.0 K. In one cavity, measurements of surface resistance versus temperature showed an extremely small residual resistance of just 0.63+/-0.06 nOhms at 16 MV/m. SIMS measurements confirm that the oxide was significantly dissociated, but they also show the presence of nitrogen after heat treatment. We also present studies of surface oxidation via exposure to air and to water, as well as the effects of very light surface removal via HF rinse. The possibilities for applications and the planned future development are discussed.

AN INVESTIGATION ON SURFACE RESISTIVITY OF POLYPROPYLENEFABRICS MODIFIEDWITHIONICLIQUIDS

In this study, polypropylene fabric was modified with two types of ionic liquids such as 1- ethyl-2,3- dimethylimidazolium ethyl sulfate (EIL) (2, 6, 10 %w/v in ethanol) and methyl-trin-butylammonium methyl sulfate (10, 15, 20 %w/v in ethanol)at different concentrations. Before modification, the fabrics were pre- treated with chromic acid to activate the surface. The effect of the modifications was investigated by thermogravimetric analysis, surface resistivity measurements and scanning electron microscopy. The pre- treatment changed surface resistivity from 1010 to 1013 ohm/sq. The modifications with the ionic liquids decreased surface resistivity of the PP fabrics short and long-term periods in the range of 106 - 108 ohm/sq. Increasing the concentration of the ionic liquids can be considered as an efficient way to reduce the surface resistivity of PP. Thermal stability of the PP altered after modification. It was observed that a coating layer formed on surface of the fabric and in the gaps of the yarns of P P with modification. This environmentally- friendly method can be used as an alternative way for improving conductivity of PP fabrics generally characterized by their high surface resistivity.

Detection of the Soft Soil at the Slope Area using Geoelectrical Resistivity Method

The landslide occur commonly in the slope zone area. The landslide may cause the damage and lose the wealth. This research aimed to detect the soft soil zone of the landslide area using geolectrical resistivity method. The geoelectrical resistivity survey was conducted using Wenner configuration with a total of 40 electrodes. Interpretation of the geolectrical model was improved trhough the direct surface resistivity measurement. The geoelectrical resistivity model shows the relatively low resistivity value at the near surface. The low resistivity value indicates that the soil is not solid and it is possible the water seep to the pore of the soil. The relatively higher resistivity value indicates that the soil is relatively compact and thus, the water is relatively hard to enter the pore. The soft zone of the soil at the slope is clearly observed and possible to slide down whenever water intervene the soil condition.

Analysis of in-service composite insulators used in overhead railway traction

Polymeric based Composite insulators are extensively used for overhead rail electric traction system; these insulators play an important role in the traction electrification which supply power to the locomotives of train. Traction insulators are subjected to a variety of stresses, like mechanical, electrical, environmental, etc., these stresses act in unison, degradation and subsequent failure of traction insulator influences the safety of traction power supply system. To understand the phenomena of degradation and in-service aging, experimental investigations are conducted on in service traction insulators to identify and analyze the structural changes occurred in the field for a specified time, the insulators are of composite silicone polymeric materials rated for 25 kV. The electrical performance on the insulator samples is investigated using leakage current analysis and surface resistance measurements under normal and fog/moisture conditions using a specifically designed fog test chamber. The structural changes are studied by using Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDAX), Fourier Transform Infra-Red (FTIR) and wettability measurements. The study highlights the in-depth analysis conducted on the performance of service insulators compares with the fresh, also suggests mitigation methods to overcome the probable failures in the field. Some interesting results obtained from the study are analyzed and presented.

Performance of Composite Insulators Used for Electric Transmission under Extreme Climatic Conditions

Composite or polymeric insulators are being used in various parts of the world for high-voltage transmission and distribution lines. In some parts of India, places in the states like Rajasthan and Gujarat experience an increase in the daytime temperature up to 50 degrees C, while the nighttime temperature reduces as low as 3-5 degrees C. Because of these extreme temperature variations along with electric stress and humidity conditions, composite insulators have to perform well over their lifetime to ensure the reliability of the transmission network. In the present work, experimental conditions are simulated with temperature variation from 50 to 3-5 degrees C along with electrical stress, humidity variation, pollution, and ultraviolet radiations. Accelerated aging studies with these stresses are conducted to understand the degradation on the insulator similar to the field conditions. Surface resistivity measurements, leakage current analysis, and surface degradation studies using thermogravimetric analysis, scanning electron microscopy, energy-dispersive x-ray, and Fourier transform infrared spectroscopy (FTIR) are conducted. Some interesting results obtained from the study are presented. Experimentation under extreme conditions with polluted insulators showed considerable degradation which was inferred from the material testing analysis. The insulator slabs on which electrical stress was not applied showed a considerable peak at 1500 cm(-1) in the FTIR spectra, indicating the generation of low molecular weight PDMS chains from the bulk due to UV aging and thermal stress, while the degradation pattern of non-polluted sample was severe compared to the slab treated but was considerably less severe in comparison with the polluted insulator sample exhibiting pollution can considerably increase degradation rate.

The anisotropic structure of electro conductive leather studied by Van der Pauw method

Determining the surface resistance of electro conductive refined natural leather materials is in the focus of this paper. Natural leather samples are initially transformed to conductive by applying chemical treatment process known as polymerization. Due to the existence of various techniques for measuring electrical resistance of conductive materials, we are focused on measuring surface resistance by arranging four electrodes in the edges of square leather samples, also known as Van der Pauw method. Improving the results accuracy, we use a multi-variant electrode placement over the sample edges. The result is the average of all results gained for different placements. Moreover, we use this electrode placement technique to analyse the anisotropy of conductive samples. The results of this research provide important knowledge about leather chemical treatment and its electrical proprieties.

Biodegradable blends of graphene quantum dots and thermoplastic starch with solid-state photoluminescent and conductive properties

Polymer composites based on blends of graphene quantum dots (GQDs) with thermoplastic starch (TPS) were prepared by melt-extrusion combined with hot pressing. The GQDs/TPS films were characterized as potential novel, high-performance, and ecofriendly composites replacing traditional non-biodegradable plastic packaging materials. GQDs stock solutions of different concentrations were incorporated into TPS matrices in order to analyze the solid-state fluorescent properties and conductive properties of GQDs/TPS films. The fluorescent, conductive, morphological, mechanical, and optical properties of the GQDs/TPS films were characterized by ultraviolet–visible spectroscopy, surface resistance measurement, scanning electron microscopy, Fourier-transform infrared (FT-IR) spectroscopy, tensile testing, and X-ray diffraction (XRD). FT-IR studies indicated hydrogen bonding between the oxygen-containing groups on GQDs surfaces and the –OH groups in the TPS. The mechanical testing results showed the optimum GQDs loading of 10.9 wt% in the blend. XRD and TEM studies indicated uniform graphene dispersions in the TPS matrix for ≤10.9 wt% GQDs loading; further increases in loading caused agglomeration. The maximum photoluminescence intensity and conductivity of the materials were obtained at 10.9 wt% GQDs loading. These materials have potential applicability in flexible optoelectronic packaging materials.

Quantum jamming transition to a correlated electron glass in 1T-TaS2.

Distinct many-body states may be created under non-equilibrium conditions through different ordering paths, even when their constituents are subjected to the same fundamental interactions. The phase-transition mechanism to such states remains poorly understood. Here, we show that controlled optical or electromagnetic perturbations can lead to an amorphous metastable state of strongly correlated electrons in a quasi-two-dimensional dichalcogenide. Scanning tunnelling microscopy reveals a hyperuniform pattern of localized charges, whereas multitip surface nanoscale conductivity measurements and tunnelling spectroscopy show an electronically gapless conducting state that is different from conventional Coulomb glasses and many-body localized systems. The state is stable up to room temperature and shows no signs of either local charge order or phase separation. The mechanism for its formation is attributed to a dynamical localization of electrons through mutual interactions. Theoretical calculations confirm the correlations between localized charges to be crucial for the state's unusual stability.

Evaluation of recycled nano carbon black and waste erosion wires in electrically conductive concretes

Increasing number of studies have focused on the materials to impart electrical conductivity into concretes. Yet, economical concerns hinder the use of conductive materials in large-scales. This study investigates the performance of electrical conductive additives obtained from waste materials on the mechanical and conductive behavior of concretes. 36 different concrete mixtures containing carbon fiber (CF), recycled nano carbon black (RNCB), waste wire erosion (WWE) and steel fiber (SF) were prepared. Carboxymethyl cellulose was used as the fiber distributor. Mechanical behavior of specimens were characterized through compressive and flexural tests along with impact experiments. Bulk and surface resistance measurements were performed for electrical conductivity analysis of concrete specimens. SEM analysis were carried out to display the amount and morphology of porosities inside concrete. Our results indicate that RNCB has significant effect on the reduction of electrical resistance when used in combination with other fillers. Besides, WWE were shown to be effective in the reduction of resistivity both in the use of alone and combined with small amount of CF. Our cost analysis reveals that electrical conductive concretes (ECON) prices can be diminished up to 40% through utilizing waste materials without the sacrifice of mechanical properties.

Electrical resistivity and thermal conductivity properties of graphene‐coated woven fabrics

ABSTRACTIn this study, it was aimed to develop electrically and thermal conductive textiles surfaces. Pretreated polyester fabrics were coated with nano graphene powders at different concentration rates (50, 100, and 200 g/kg) by knife over roll technique. Electrical resistivity, thermal conductivity, thickness and mass per unit area measurements, bending rigidity, and abrasion resistance tests of coated fabrics were performed. Surface resistivity measurements of coated fabrics were made according to ASTM D 257 standard with Keithley 8009 Resistivity Test Fixture. Surface electrical resistivity values of coated fabrics decreased with increasing concentration rates. Of note, 2.53 × 104 Ω/sq surface resistivity value was obtained at 200 g/kg graphene concentration rate. Thermal conductivity measurements of coated fabrics were made according to JIS R 2618 standard with Quick Thermal Conductivity Meter (QTM‐710). Thermal conductivity property of fabrics improved depending on graphene concentration. The highest thermal conductivity value (0.4243 W/mK) was obtained at 200 g/kg graphene concentration rate. One of the most important results of the study was that a maximum weight loss of 0.40% was observed in the abrasion resistance test even after 100 000 cycles. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48024.

Resistivity profile of epitaxial layer for the new ALICE ITS sensor

Wafers with different epitaxial layer thicknesses of 12, 18, 20, 25, 30 and 40 μm and high resistivities ranging from 0.03 to 8.0 kΩ⋅cm have been investigated in this study. To verify their properties, surface resistivity measurement, scanning electron microscopy inspection and spreading resistance profiling have been performed. The results indicate that wafers with a 25-μm epitaxial thickness are well-suited to our requirements for use as a starting material for ALPIDE chip production in the ALICE ITS upgrade project.

Failure analysis of BMC insulators used for third rail traction system

Bulk molding compound (BMC) or Glass Reinforced plastic (GRP) composite insulators are extensively used for the third rail electric traction system. The performance of these insulators primarily depends on the local environmental conditions that cause degradation over a period of time. Degradation leads to partial arcing which grow more severe and can generate combustion that ignites flammable debris, smoke including fires resulting in service interruptions and safety risks of the third rail traction system. In the present investigations, exhaustive analysis is conducted to understand the root cause of degradation and arcing on the field aged insulators rated for 750Vdc. Leakage current and surface resistance measurements are conducted under dry, wet and contaminated conditions. Further to better interpret Physico-chemical analysis are conducted using Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDAX) and Fourier Transform Infra-Red (FTIR) spectroscopy to investigate surface morphology and chemical changes in the samples, also Thermo-Gravimetric Analysis (TGA) is performed to find the thermal characteristics of the insulator. Interesting results obtained from the investigations clearly present evidence to loss of epoxy material from the bulk eventually leading to the exposure of glass fibers causing degradation, arcing and failure of the insulators. The study further highlights the essential procedures to be edopted to locate, isolate, and better anticipate failures of BMC insulators used in third rail traction system.

Constructing the Apparent Geological Model by Fusing Surface Resistivity Survey and Borehole Records.

We constructed an apparent geological model with resistivity data from surface resistivity surveys. We developed a data fusion approach by integrating dense electrical resistivity measurements collected with Schlumberger arrays and wellbore logs. This approach includes an optimization algorithm and a geostatistic interpolation method. We first generated an apparent formation factor model from the surface resistivity measurements and groundwater resistivity records with an inverse distance method. We then converted the model into a geology model with the optimized judgment criteria from the algorithms relating the apparent formation factors to the borehole geology. We also employed a non-parametric bootstrap method to analyze the uncertainty of the predicted sediment types, and the predictive uncertainties of clay, gravel, and sand were less than 5%. Overall, our model is capable of capturing the spatial features of the sediment types. More importantly, this approach can be arranged in a self-updated sequence to enable adjustments to the model to accommodate newly collected core records or geophysical data. This approach yields a more detailed apparent geological model for use in future groundwater simulations, which is of benefit to multi-discipline studies.

A study on the dielectric response of polyethylene-metal oxide nanocomposites for electrical insulation in HVDC cables

Abstract Metal oxide nanoparticles such as MgO and SiO2 have been investigated as fillers in low density polyethylene. The surface modification of the oxide nanoparticles were done with functional methyl, ethyl, hexadecyl or octylsilane. The distribution and dispersion of the nanoparticles in the LDPE is determined by SEM (Scanning Electron Microscopy). Studies were carried out by measuring surface resistivity, volume resistivity. Fourier Infrared spectrometer for identifying the functional groups. Dielectric response studies were carried out using spectroscopic techniques like Dielectric spectroscopy (dielectric loss angle, permittivity, capacitance measurements as a function of frequency from few mHz upto 1 kHz). The surface and volume resistivity of nanocomposites have increased by one order compared to neat LDPE samples. Higher concentrations of nanoparticles have resulted in lower withstanding stresses probably due to decrease in crystallinity with filling concentration. TMMS treated nanoparticle composite show better performance compared PEMAH treated nanocomposite. The dielectric response study on nanocomposites show there is no change in permittivity upto 1 Hz, but slightly increase in value below 1 Hz and upto 0.001. It is presumed that large amount of charges migrate into and go through the LDPE. On the contrary Nano composites can inhibit the charges to inject into the interior of the composite and make most of the charges gather on the surface of the sample.

Characterizing the Distribution of Microwave Surface Resistance of HTS Film Based on Metal Ring

This paper presents a novel method for measuring the microwave surface resistance distribution of high-temperature superconducting thin films by a dielectric resonator with a metal ring. After calibration, the effect of metal ring loss on measurement accuracy is negligible. The measurement resolution is determined by the internal diameter of the metal ring, which makes the design of the device more flexible. Therefore, measurement with high resolution and convenience can be achieved simultaneously by using a metal ring with proper size and operating at a relatively low frequency. A test device working at 32 GHz with TE01(1 + δ) mode was developed. Its resolution is a circular area with a diameter of 5 mm and an area of 19.6 mm2. The unloaded quality factor of the test device is more than 140,000, when it is loaded by the calibration cavity. The test device has a relative uncertainty of less than 6%, which complies with the uncertainty (20%) specified by the international standard for the microwave surface resistance measurement of high-temperature superconducting (HTS) thin film. The surface resistance distribution of a 2-in. YBCO/LAO/YBCO superconducting film sample was measured by this test device.