Surface Resistance Measurements Research Articles

Structural, Mechanical and Thermal Behaviour of MWCNT-PCS Hybrid Polymer Matrix Nanocomposites: An Extension Study of Graphene-Epoxy Polymer Matrix Nanocomposites

This study extends previous research on graphene-epoxy nanocomposites by investigating the thermal, mechanical, electrical, and chemical properties of multi-walled carbon nanotube (MWCNT)-reinforced polycarbosilane (PCS) hybrid polymer matrix nanocomposites. Building on the foundational work that demonstrated the enhanced performance of graphene-epoxy nanocomposites, this research explores the potential of MWCNTs as a superior reinforcing agent within the PCS matrix. The MWCNT-PCS nanocomposites were synthesized and characterized using a comprehensive suite of techniques, including X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, specific gravity analysis and surface resistance measurements. The results indicate that MWCNT-PCS nanocomposites exhibit improved thermal stability, higher degradation temperatures, and enhanced thermal conductivity, along with significant improvements in mechanical strength and lower surface resistance, indicating superior electrical conductivity. Additionally, the chemical interactions between MWCNTs and the PCS matrix were analyzed to assess the dispersion and bonding quality, contributing to the overall performance of the nanocomposites. These findings suggest that MWCNT-PCS nanocomposites are promising candidates for high-performance applications in aerospace, where thermal stability, mechanical strength, electrical conductivity and chemical stability are critical. This paper not only confirms the benefits of MWCNT reinforcement but also provides a direct comparison with graphene-epoxy nanocomposites, underscoring the advancements made in this ongoing research.

Shielded Pair Method for Beam Screen Surface Resistance Measurement at Cryogenic Temperature

The shielded pair resonator method is a useful tool in the measurement of accelerator components, such as the beam screens used in the Large Hadron Collider (LHC), the High-Luminosity (HL) LHC, or future accelerators. It can measure the resistive losses at several frequency points by separating the resistive losses on the sample from other sources of losses. We built a new resonator to be inserted into a superconducting dipole magnet (peak magnetic field of 9.5 T) and to measure the surface resistance of beam screens, such as LHC beam screens coated with amorphous carbon (a-C). The device can measure surface resistance at any temperature between 4.2 K and 300 K, in the frequency range of 400 MHz to 1600 MHz. We conducted the first surface resistance measurements of two a-C coated beam screens at 4.2 K and showed that the 200 nm to 400 nm titanium underlayer plus 50 nm a-C only has a limited effect on the surface resistance. This first result supports the choice of this coating as baseline for the HL-LHC triplets magnets upgrade. The resonator will have an important role in the characterization of next-generation beam screens, such as a beam screen with laser-engineered surface structure (LESS). Further measurements of the LHC beam screen in the presence of magnetic fields up to 9.5 T and throughout the full temperature range are going to be reported separately.

Spray-deposition of graphene/polymer thin coatings on polyimide sheets for lunar dust adhesion mitigation

NASA seeks to develop technologies to mitigate dust accumulation from planetary surfaces on robotic and human systems hardware during planned space exploration missions. With a return to the Lunar surface, lunar dust threatens the durability and reusability of components and vehicles due to its fine, jagged morphology and highly abrasive nature. Lunar dust consists of particles less than 60 μm in size that are chemically reactive, electrostatically and sometimes magnetically charged. Unique materials and technologies that reduce or mitigate lunar dust adhesion will be critical to support long duration missions and eventual sustained presence on the lunar surface. The goal of this work was to prepare dust resistant, space durable polymer films to satisfy dust accumulation mitigation needs for future NASA missions. In this regard, several graphene coated polyimide thin films have been developed with surface resistivity properties in the range of 103 Ω/sq to 1011 Ω/sq and evaluated for their dust adhesion performance. Raman spectroscopy was used to characterize and assess the quality of graphene ink coated sheets while surface resistivity measurements were used to assess electrical conductivity. Scratch testing and abrasion resistance measurements were used to evaluate overall abrasion performance. Water contact angle and optical microscopy were used to evaluate changes in surface topography and chemistry. Graphene coated polyimide surfaces with charge dissipative resistivity (106 Ω/sq) demonstrated a minimum in residual particle areal coverage compared to conductive and insulating surfaces.

Exploring the morphological surface resistance and optical absorption of thin black carbon nanotube films for electronic and optoelectronic devices

This study investigates the optical and electrical properties of thin black films of carbon nanotubes (CNTs) fabricated under various conditions to explore their potential integration as either a perfect broadband absorber or enhanced counter electrode. The study involves SEM measurements, surface resistance measurements, and UV–Vis. spectrometer analysis. The results show that the CNT thin films exhibit high electrical conductivity and strong light absorption across various wavelengths. Optically, we investigated the impact of varying the growth temperature and catalyst temperature on the absorption profile of the thin films. The fabricated and deposited CNTs showed broadband absorption spectra, reaching 92.8% of the commercial reference sample, covering both visible and near-infrared spectra. Alternatively, the morphological surface resistance for the CNT thin films recorded agonist commercial CNT samples and FTO-coated glass. An average surface resistance of 20.5 Ω/Sq.

High-Temperature Measurement Technology for Microwave Surface Resistance of Metal Materials

The resonant cavity method is a commonly used method for high-temperature testing of the complex permittivity of dielectric materials. When a resonant cavity is used for high-temperature testing, the microwave surface resistance of the cavity metal material will deteriorate due to factors such as oxidation reaction and thermal fatigue, resulting in a decrease in testing accuracy and repeatability. Therefore, when designing a high-temperature resonant cavity, the temperature response characteristics of the microwave surface resistance of the cavity metal material should be obtained in advance. In this paper, a high-temperature measurement method of microwave surface resistance of metal materials based on a separate cylindrical resonator is proposed, a mathematical model of microwave surface resistance inversion based on the resonator quality factor is established, and a high-temperature measurement system of microwave surface resistance is integrated. The reliability of the proposed method and system is verified through simulation and experiment. The measurement frequency covers 7-18 GHz, and the maximum test temperature reaches 500°C. Systematic error of microwave surface resistance measurement at room temperature is less than 3%.

Dielectric resonator to measure surface resistance of accelerator components at room temperature and 77 K

Dielectric resonator to measure surface resistance of accelerator components at room temperature and 77 K

Effects of the Ratio of Nano-Cu to Hydroxylated MWCNTs on Anticorrosion and Surface Conductivity of Cu/MWCNT Epoxy Coatings on a Steel Substrate

Epoxy coatings provide an economical and practical solution for combating steel corrosion. However, epoxy coatings have poor conductivity, resulting in the accumulation of electrostatic charges. The surface conductivity and anticorrosion properties of epoxy coatings can be improved by adding nano-Cu and hydroxylated multi-walled carbon nanotubes (MWCNTs). This paper investigates the impact of MWCNTs at different concentrations (2.5, 5%) and the ratio of nano-Cu to MWCNTs on the surface conductivity and anticorrosion properties of epoxy coatings on a steel substrate. The findings from the four-probe method of measuring surface resistance indicated that the surface resistivity of steel coated with an epoxy composite of 5% MWCNTs and 65% nano-Cu (Cu65/MWCNT5) was significantly lower, approximately by one order of magnitude, compared to steel coated with a 5% MWCNT (MWCNT5) epoxy coating. When the Cu65/MWCNT5-coated steel was immersed in a 3.5 wt % NaCl solution for 30 days, it was observed that there was a minimal effect on its surface resistivity. The inclusion of a high content of MWCNTs facilitates a more uniform distribution of Cu particles within the epoxy coatings, thereby improving the anticorrosion properties of these coatings on a steel substrate. This was further corroborated by the results of the polarization curves and electrochemical impedance spectroscopy, demonstrating that the Cu65/MWCNT5 epoxy coating on a steel substrate offers exceptional anticorrosion and barrier protection properties. The corrosion rate of steel with a Cu65/MWCNT5 epoxy coating was three orders of magnitude lower than that of steel with a Cu65/MWCNT2.5 epoxy coating, at 4.79 × 10−7 mm/year.

Increasing the Reliability of Formation Factor-Based Transport Property Prediction for High Performance Concrete Mixtures Through Innovative Matching Pore Solution Curing

Recent specifications for concrete bulk resistivity tests (ASTM C 1876 and AASHTO TP 119) recommend a submerged standard (simulated) pore solution (SPS, solution conductivity = 78.74 mS/cm) for curing concrete specimens. The rationale for the bucket test is that immersing concrete specimens in a soak solution similar to their pore solution would eliminate the need to determine pore solution resistivity for calculating the formation factor (FF) of concrete mixtures. However, the thermodynamic modeling predictions of 91-day pore solution concentration (PSC) for eight high performance concrete (HPC) mixtures evaluated in the current study showed SPS to be a close representation only for reference ordinary Portland cement (OPC) and binary silica fume mixtures. In contrast, the average PSC of Class F and Class C fly ash mixtures was approximately 12% to 20% lower and 20% to 40% higher, respectively, than the SPS. Accordingly, an innovative matching pore solution (MPS) curing approach was developed in which mixtures are grouped based on the influence of supplementary cementitious materials (SCMs), that is, their type and replacement levels of the long-term PSC of concrete mixtures and, thereby, cured in a simulated solution matching the average PSC of a particular group. Based on experimental work in the current study, HPC mixtures under MPS demonstrated a lower coefficient of variation (COV) and more comparable (<10% difference) bulk resistivity (BR) and surface resistivity (SR) measurements compared with SPS. Moreover, the MPS improved the reliability in FF determination and FF-based transport property prediction for HPC mixtures, as verified by lower mean absolute error and improved R2 between FF-predicted diffusion coefficients and experimental measurements.

Preparation of polyaniline‐poly(ethylene‐vinyl acetate) film: Resistivity in the ESD range

AbstractFilms of polyaniline (PANI) salt with poly (ethylene‐vinyl acetate) (EVA) with two different PANI salts, PANI‐methane sulfonic acid (PANI‐MSA) and PANI‐p‐toluene sulfonic acid (PANI‐PTSA) are prepared by solution processing technique for electrostatic discharge (ESD) application. PANI‐MSA/PANI‐PTSA salts were synthesized by emulsion polymerization pathway then dispersed the PANI salt in xylene solvent. EVA was dissolved in xylene solvent. Series of PANI salt/EVA films were prepared by mixing a particular amount of PANI dispersion to a fixed amount of EVA solution and evaporated the solvent. PANI‐EVA films were evaluated by tensile strength, elongation at break and surface resistivity measurements. The results of PANI‐MSA/EVA films are compared with the results of PANI‐PTSA/EVA films. Also, PANI‐MSA/EVA and PANI‐PTSA/EVA solutions are coated on different substrates and measured their electrical resistivity for ESD application. Morphological study and thermal behaviors of PANI‐MSA/EVA films are carried through FE‐SEM and TGA respectively. Sphere morphology of EVA changed to swollen sheet like morphology with the addition of PANI, and the spaces between the sheets increased with the increase in PANI content. The surface resistivity of the EVA‐PANI films are found to be in the range of 104–108 Ω sq−1, which is suitable for ESD application.

Fabrication and electrical, electrochemical characteristics of copper chloride-doped graphene films

In this study, the thin films of graphene (Gr) doped with copper (I) chloride (CuCl) were fabricated on a copper (Cu) substrate by chemical vapour deposition method at 1000oC in a mixture of gases (Ar, H2, and CH4) combined with annealing method at 220oC to vapourise CuCl powder. The morphology, structure, electrical, and electrochemical characteristics of the CuCl-doped Gr films (CuCl-Gr) were investigated via field emission scanning electron microscopy (FESEM), Raman spectroscopy, four-probe method and cyclic voltammetry. The results of Raman spectroscopy showed that there is a shift of the characteristic peaks (D, G and 2D) toward higher frequencies of the CuCl-Gr film compared to the pristine Gr film. The surface resistance measurement results exhibited that the CuCl-Gr film has a surface resistance of about 452 ohm/square (Ω/□), 2.02 times lower than that of the Gr film (913 Ω/□). The electrochemical characteristic measurement results in 3 mM Fe(CN)63-/4- with 0.1 M PBS proved that the peak response current of the gold electrode (AuE) coated with CuCl-Gr film is 21.2 μA, 1.6 times higher than that of the AuE coated with Gr. These research results showed a great potential of using CuCl-Gr film to cover the surface of working electrodes in increasing the conductivity and sensitivity of electrochemical sensors.

On Surface Resistivity Measurements of Thin Insulation Materials

Surface resistivity measurements are frequently used for material characterization. However, the influence of sample thickness is not covered sufficiently in ASTM D257 and IEC 62631-3-2 standards. In this work, electric field simulations and polarization–depolarization current (PDC) measurements are used to study the thickness dependence of such measurements. It is found that measurements according to the standards are not reasonable for low thickness (<1 mm) and high surface resistivity (>1013– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{14}}~ {\Omega } $ </tex-math></inline-formula> ). The dependence on thickness is shown to be mainly due to the different tangential electric field stress along the measured surface. Furthermore, indications for charge injection at high electric field stress inside the sample volume are found by a positive polarity of the depolarization currents. A novel electrode configuration for more accurate (more than one order of magnitude) and much less thickness-dependent surface resistivity measurements is proposed in this work and its benefits are demonstrated. It is also shown how the parasitic influence of an electrode holder can be effectively reduced by more than one order of magnitude when measuring surface resistivities. In addition, it is found that polarization times for steady-state surface resistivity values should be at least several minutes instead of the suggested 60 s from standards.

Volume relaxation of soda-lime silicate glasses below glass transition temperature

Structural relaxation is a widely known phenomenon that occurs in glassy systems, which still attracts strong industrial and research interest. Although the volume change associated with structural relaxation is well described by the Kohlrausch–Williams–Watts function, its origin, particularly from a glass structural viewpoint, is not clearly defined. To understand the behavior of structural relaxation, in this study, we performed volume relaxation evaluations, Raman spectroscopy assessments, and surface resistivity measurements before and after annealing at 50 K below the glass transition temperature Tg of soda-lime silicate glasses with the same Tg but different fragilities. The combined results indicated that the following changes in the glass structure occurred during the structural relaxation: (1) reorganization of the SiO2 network; (2) transfer of Na ions from the ion channel region into the SiO2 network region; and (3) segmentation of the ion channel region in the modified random network model.

Multifunctional silane-based superhydrophobic/impregnation treatments for concrete producing C-S-H gel: Validation on mockup specimens from European heritage structures

Many of the concrete structures that conform our modern cultural heritage are in need of repair and protective interventions. Silane-based impregnation treatments can be used to repair onset cracks and reinforce the surface due to their ability to produce silica and C-S-H gels, and can be modified by incorporating hydrophobic precursors to create multifunctional treatments that also protect from water ingress.Since the effectiveness of impregnation treatments is dependent on substrate properties and chemical-physical changes it may have experienced over time, validation using standard materials may not always be representative of on-site application. In this work, the effectiveness of three innovative silane-based impregnation treatments developed by our group (two of them combining superhydrophobic properties) was evaluated on mockup specimens, which simulate the properties of the cementitious materials from six different heritage structures across Europe, artificially aged to simulate weathering by three methods: carbonation, chloride ingress and physical damages (freeze–thaw and thermal cycles).The characterization of the treatments showed they are compatible in terms of chemical interaction, applicability and minimal aesthetical alterations. Surface resistance and ultrasound pulse measurements have been used to assess the improvement in mechanical properties. The incorporation of hydrophobic components and fumed silica has a relatively low impact over the mechanical properties while it significantly reduces water absorption and grants water repellent properties to the surface, giving rise to a superhydrophobic performance.

Методы исследования электрофизических характеристик эпитаксиальных слоев твердых растворов типа n/p-InxGa1–xAs для приборных структур большой площади

The production of epitaxial layers requires the search for simple, technologically advanced and accurate methods for assessing the basic properties of layers and compositions made from them. The issue is especially acute for developers of multistage photovoltaic converters (PVCs) for space applications, which are distinguished by a complex heterostructure, including 5 or more p-n junctions and a large area. The work carried out a search for an optimal method for studying the electrical characteristics of thin semiconductor layers of the n/p-InxGa1-xAs type with different doping levels. The main task is to measure the basic electrical characteristics in various ways: resistivity (conductivity), concentration of the main charge carriers, the dependence of the main electrical parameters on the type and level of doping and their comparison. Using the example of p- and n-type In0.01Ga0.99As solid solutions obtained by MOS-hydride epitaxy, a technique for studying the main electrical characteristics of epitaxial layers is proposed, taking into account the assessment of homogeneity on large-area samples. A comparison of the results obtained by various methods is presented: photoluminescence, non-contact measurement of surface resistance, Van der Pauw (Hall effect) and capacitance-voltage (electrochemical profiling (ECP), in situ control methods. Based on the results obtained and comparison with literature data, conclusions are drawn about the need, sufficiency and complementarity of methods for monitoring and studying semiconductor epitaxial structures.

Proposal: Apparatus for Sensing the Effect of Surface Roughness on the Surface Resistance of Metals

The root mean square surface roughness Rq of metals is detrimental in several microwave applications. Rq characterization methods are thus largely used and of great interest. In this work, a new dielectric loaded resonator (DR) design is proposed to evaluate the surface resistance variations of samples with different Rq. The new design is thought to make the measurement accuracy, usually strongly affected by the measurement repeatability, suitable for this study. We analyze the measurement method's sensitivity and accuracy in order to assess the possibility of using this new DR design for highly accurate surface resistance measurements sensitive to Rq variations.

Comparative Studies on the Electrical Properties of PEDOT:PSS Doped SNP Films and Hydrogels for Medical Electrode Applications

Poly (3,4-ethylene dioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) is a promising conductive polymer to be the next-generation electrode for medical purposes. However, PEDOT:PSS exhibits low conductivity (~1×10−3 S cm−1); hence, incorporating silver nanoparticles (SNP) with PEDOT:PSS will improve the electrical conductivity. This paper aims to investigate the electrical properties differences between PEDOT:PSS doped SNP-based films and hydrogels. The two different states of PEDOT:PSS/SNP serves its particular purpose as an electrode. Initially, the PEDOT:PSS/SNP solution was prepared by homogeneously mixing at constant stirring. Then, the solution was drop-casting onto a glass substrate to produce a film, while another part of the solution was undergoing a freeze-thaw method to produce hydrogel. Surface resistance measurement exhibits lower resistance values for a film (0.11 kΩ) than hydrogel (0.59 kΩ). A scanning electron microscope (SEM) was utilized to observe the morphology of the films, while an optical microscope (OM) observed the surface of the hydrogel since they are in different states. Fourier Transform Infrared (FTIR) spectra display prominent peaks that described the successful blending between PEDOT:PSS and SNP for both films and hydrogels. These findings demonstrate that varying processing methods of preparing PEDOT:PSS/SNP in films or hydrogels may influence its properties like the electrode, which should provide a valuable contribution to the bioelectronic areas.

A new method to electrical parameters identification of carbon fiber reinforced composites using lightning disturbances corresponding to subsequent return strokes

Carbon fiber reinforced polymers (CFRPs) are modern materials increasingly used in the aerospace industry due to its excellent mechanical properties but there is still a lot to do to improve their electrical capabilities. The paper presents a new prototype measurement system and method for identifying electrical parameters of conductive composites using both: low DC electrical signals and high-current impulses of lightning nature. Detail presentation of the measurement setup and used techniques was made on prepared three types of CFRP laminate samples consisting of five carbon fabric layers each with different contents of flame retardant and carbon black conductive additives. The 4-electrode and Van der Pauw methods were used for low voltage measurements of volume and surface resistivity. 15 kA high-current pulses have been applied to determine composite sample parameters such as equivalent volume and surface resistivity, surge impedance, current distribution and damage immunity to the effects of the lightning-type currents.

Study of Resistivity Distribution in Modified Surface Steel

This work focuses on making and studying steel conductors with inhomogeneous surface conductivity. Employing such materials (structures) for engineering the high-field pulsed magnets can provide them with enhanced durability. In this work, monotonically changing resistivity was realized by pack chromizing the medium-carbon steels, 30KhGSA and 40Kh, which were treated at 1000 °C in argon for 150 h under the Cr-load of 20 mg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> to obtain a diffuse layer with minimal carbides at the surface. An approach to investigate the resistivity distribution across a diffuse layer after steel chromizing is suggested and involves a stepwise surface grinding, resistance measurement, and analytical processing of experimental data. The resistivity profile obtained by this method is well described by the complementary error function. At the near-surface layer, 30KhGSA and 40Kh steels have almost the same values of resistivity, about 110– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$115 ~\mu $ </tex-math></inline-formula> Ohm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> cm, which is 2.9–4.3 times higher than that in the bulk depending on steel. A strong correlation, almost a linear dependence, of resistivity with the depth-derived chromium concentration in the material was found. The proposed method allows one to measure the depth-varied resistivity for ferrous alloys with proper accuracy, while it does not require complex measuring equipment compared with other ones.

Investigation of electrical and electromagnetic properties of quartz fiber reinforced polymer composite material by using modified paints with carbon nanoparticles (graphene/double-walled carbon nanotube)

Composite materials have many features to contribute to aircraft design but have low electrical conductivity. In this study, it is aimed to increase the electrical conductivity of FRP (Fiber Reinforced Polymer) composites used in different parts of the aircraft. The modified nanoparticles were added into the aircraft paint and applied on the composites used in the radome part of the aircraft, and it is aimed to either increase or keep the electromagnetic permeability stable. Firstly, the surfaces of the FRP composite samples were painted by Graphene and Double-Walled Carbon Nanotube (DWCNT) to reinforce the conductive nanoparticles at different ratios. Resistance measurements of the samples were made according to the Airbus “Electrical Surface Resistance Measurement” procedure and their electrical conductivity was calculated. The Non-Contact Measurement Method test setup was used to obtain information about the electromagnetic properties of the samples. As a result of the measurements, N3 (σ = 4.37x10−4 S/m, S21 = −15.81 dB) sample conforms the best with the objectives of ourstudy compared to electrical conductivity (N0, σ = 4.83x10−5 S/m) and electromagnetic permeability (N0, S21 = −15.83 dB) of the reference sample. The contact angle measurements were taken to determine the contact angle changes depending on the surface morphology and conductivity changes of the samples painted with different and varying amounts of nanoparticle doped paint. Additionally, measurements were taken with the FTIR-ATR instrument to make surface analysis of the samples.

Improvement of IEC Line-electrode for Surface Resistivity Measurement on Insulating Materials

Improvement of IEC Line-electrode for Surface Resistivity Measurement on Insulating Materials