Electrical Conductivity Properties Research Articles

Ku-band microwave absorbing properties of submicron monodisperse carbon spheres fabricated by hydrothermal synthesis and carbonization

Carbon materials have been widely used as the absorber for the stealth of military flight equipment in recent years. This study focuses on preparing submicron monodisperse carbon spheres (SMCS) by hydrothermal synthesis and subsequent carbonization. The influence of carbonization temperature (900 ℃, 1000 ℃, 1100 ℃, and 1200 ℃) on the microstructure, phase, specific surface area, pore size distribution, electrical conductivity, complex permittivity, and microwave-absorbing properties of SMCS in the Ku-band (12.4–18.0 GHz) is investigated. The graphitization degree, electrical conductivity, and complex permittivity of SMCS carbonized at 1100 ℃ are all the highest. The C-1100 in paraffin/composites shows a strong dielectric resonance loss, thus improving microwave-absorbing properties. The effective absorption bandwidth (RL < −10 dB) of C-1100 is 4.9 GHz and the minimum reflection loss (RL min) is −18.71 dB at 14.64 GHz with a matching thickness of 1.3 mm.

The effect of transition metal ion implantation on the structural and optical properties of few-layered borophene

Borophene, a monometallic two-dimensional layered material has gained significant attention due to its exceptional electrical and optical properties. Despite this, borophene layers tend to restack; retards ionic conductivity, imperative for practical applications. Thus, by introducing large-sized dopants into borophene nanosheets using an ion implantation technique has been acknowledged. Accordingly, herein, structural and electronic engineering of borophene has been done with implantation of copper (Cu) ions at various fluence rates (5 × 1012, 5 × 1013, 5 × 1014 and 5 × 1015 ions-cm−2 respectively) using 1μA current at a low energy of 80 keV. The Cu insertion between borophene interlayers prevents self-restacking; providing surfacial active sites with tunable work function and decreased band gap of pristine borophene, thereby increasing charge transport ability. Further, the structural properties of implanted borophene were characterized through Raman spectroscopy, FT-IR spectroscopy and optical properties using UV–Vis and photoluminescence studies. Also, I-V measurements were conducted to study the electrical properties. Hence, ion implantation helps in significantly enhance the electrical conductivity and transportation properties of borophene.

Synthesis of reduced graphene oxide and Nickel oxide/reduced graphene oxide composite materials for supercapacitor applications and their computational investigations

This study outlines the synthesis of reduced graphene oxide (rGO) and Nickel oxide/reduced graphene oxide (NiO/rGO) composite materials without the use of binders. The synthesis method involved microwave-assisted reduction using ascorbic acid (AA) and varying weight ratios of potassium hydroxide (KOH) to convert graphene oxide (GO) to rGO. The research investigates how adjusting the weight ratios of GO and KOH influences the electrical conductivity (EC) properties of the synthesized materials, particularly exploring the impact of KOH addition on the porosity growth in the rGO layers during fabrication. Various analytical techniques, including optical, vibrational, morphological, bonding, and network analysis, were employed to characterize the synthesized materials. The materials were evaluated as potential supercapacitor electrodes using electrochemical techniques such as cyclic voltammetry and A.C. impedance analysis, including Nyquist and Bode plots. The specific capacitance (CS) of rGO and NiO/rGO was determined to be 1400 Fg−1 at a scan rate of 0.005 Vs−1. The synthesis process avoided the use of hazardous reagents. Additionally, density functional theory (DFT) based computational analysis was conducted to support the experimental findings. The study documents the influence of incorporating NiO onto the surface of GO and rGO on the energy gap (Egap) and investigates the density of state (DOS) to understand the effect of MO-rGO interaction. Furthermore, frontier molecular orbital (FMO) contours were examined to analyze excitation qualities, and electron potential was visualized and mapped onto the electron density surface to gain insights into charge dispersion within the structures.

Effect of Torsional Load on Electrical and Mechanical Properties/Behaviour of Stretchable GNP-Ag Conductive Ink

Stretchable conductive inks (SCIs) have gained significant attention in recent years due to their potential applications in flexible and wearable electronics. Graphene nanoplatelet (GNP) hybridization conductive ink is a promising material for stretchable electronics due to its high electrical conductivity and excellent mechanical properties. However, the resistivity of GNP ink on flexible substrates can be affected by various factors, such as the torsion of the substrate. This paper aims to investigate the effect of torsional load in terms of the electrical and mechanical behaviour of hybridization conductive ink between GNP and Ag. The research was carried out on the formulation and performance of GNP hybrids using GNP and silver flakes (Ag). The GNP hybrid ink was printed on a copper substrate using a mesh stencil method and cured at 250 °C for an hour. The resistivity was evaluated at room temperature before and after the torsional tests in terms of electrical characteristics. The finding exposed that the resistivity values for each of the three samples of torsional tests significantly changed after 1000 cycles. Eventually, the resistance value at cycle 5000 rose due to the damaging impact of increasing the number of torsional cycles on the sample. In future work, it is recommended that the evaluation is made under temperature dependence and supported by SEM images.

Researches for higher electrical conductivity copper‐based materials

AbstractCopper and copper‐based materials are widely used in power electronics, automobiles, mechanical manufacturing and high‐tech manufacturing fields such as aerospace, telecommunications and integrated circuits owing to their comprehensive advantages in mechanical, electrical conductivity and processing properties. With the rapid development of technology, many emerging technical fields have introduced more challenging requirements for the electrical conductivity of copper. This article reviews the research status of high‐conductivity copper‐based materials and introduces three methods to improve electrical conductivity, including purification, alloying and addition of nanocarbon materials. We summarise the advantages, disadvantages and future development trends of methods for improving copper conductivity. The key to producing high‐conductivity copper‐based materials is development of low‐cost, continuous and stable processes.

Synthesis and novel applications of graphene fibers

The past decade has witnessed dynamic and fruitful developments of carbon materials. Particularly, graphene fibers emerge as a new type of carbon material directly composed of graphene sheets with unique structure, excellent electrical conductivity, strength, and lightweight properties, thus attracting increasing interest of scientists in multi-disciplines ranging from chemistry, materials science, biology to medical science. In this Perspective, we summarize latest progresses in the synthesis of graphene fibers and discuss their pros and cons. Then, various strategies for improving the mechanical, electrical, and thermal properties of graphene fibers are introduced in detail. Subsequently, recent applications of graphene fibers are highlighted, such as self-powered devices, photovoltaics, neural recording microelectrodes, etc., aiming to present the state of the art in this fast-growing field. Finally, the current limitation and future prospect of large-scale application of graphene fibers are also proposed. With the continuous development of materials and techniques, graphene fibers are projected to take more important roles in diverse fields in the future.

Tunability of impedance spectroscopy, electrical conductivity and optical properties of Cu-doped TiO2 nanostructures for optoelectronic device application

This paper details the successful fabrication of Cu-doped TiO2 nanostructures using a co-precipitation method. A thorough analysis of the structural and electrical characteristics of the nanostructure samples was carried out. It was found that all synthesized samples exhibited an anatase TiO2 structure. The XRD pattern indicated an average crystalline size of 23.19 nm for Cu-doped TiO2 nanostructures, whereas TiO2 nanostructures showed a size of 11.78 nm. The UV-Visible spectrum indicated a noticeable absorption band shift towards longer wavelengths, coupled with an increased absorption rate of light. Analysis of electrical conductivity showcased temperature-dependent variations in conductivity at high frequencies. Impedance spectroscopy unveiled improved conductivity upon the integration of Cu into TiO2 nanostructures. Nonetheless, at 300 K, copper doping resulted in a decline in electrical conductivity, whereas at elevated temperatures, Cu doping showed a increase in conductivity for the nanostructures samples. These findings underscore the potential and applicability of the nanostructures, showcasing improved AC conductivity and electrical characteristics, making them promising for various electrical applications.

Facile production of graphene-based ternary composite coatings on metallic bipolar plates

Graphene-based composite coatings can be applied on metallic bipolar plates (BPs) of PEMFC for corrosion protection and electron conduction, benefited from the high electrical conductivity, chemical stability and physical barrier properties of graphene. To reach the high electrical conductivity requirement, the composite coatings shall have high graphene content, which brings challenges including dispersion, processability and interface compatibility. In this work, polyisocyanate was grafted on graphene surfaces to enhance the compatibility with polyurethane (PU). Carbon black was introduced as conductive bridging, which filled in defects of graphene/PU coatings. The corrosion current density of the ternary composite coatings with 60 % functionalized graphene, 30 % PU and 10 % carbon black was 0.43 μA·cm−2 in H2SO4 solution of pH 3 at 80 °C, while the interfacial contact resistance was 6.75 mΩ·cm2 and the in-plane conductivity was 137.4 S·cm−1. The composite coatings provided an efficient and cost-effective solution for up-scaling production of metallic BPs.

Evaluation of Strain Sensors Based on Poly(acrylonitrile-co-butadiene) and Polypyrrole Synthesized by the Diffusion Method.

In this study, the functionality of an elastomer composite material containing polypyrrole (PPy) as a stress sensor was evaluated. The material was prepared using the swelling method by diffusing the pyrrole monomer into the elastomer before polymerization. To achieve adequate diffusion, organic solvents with affinity for the elastomer were used. The resulting materials were characterized by scanning electron microscopy (SEM), surface electrical resistance, and thermal and mechanical properties for application as a stress sensor. The simultaneous change in electrical resistance and tension stress was measured using a digital multimeter with electrodes connected to the jaws of a universal mechanical testing machine. The influence of stress cycles on the piezoresistivity of the composite materials was investigated. The obtained PPy/NBR composite presented a good combination of electrical conductivity and mechanical properties. The strain at break remained with mild variation after coating with PPy.

Advancing energy solutions: Carbon-based cementitious composites in energy storage and harvesting

The rapid progress of smart and sustainable cities has led to an increased demand for construction materials that possess functional capabilities in energy storage and harvesting. In light of this, a comprehensive literature review is conducted in this study to investigate the multifunctional properties exhibited by carbon-based cementitious materials. Specifically, the piezoelectric, thermoelectric, tensile, compressive, and flexural behaviors of carbon fiber (CF), graphene, graphite powder (GP), and carbon nanotubes (CNTs) are thoroughly examined through multi-scale research approaches. The electrical conductivity and mechanical properties of these carbon-based additives are analyzed in relation to their molecular structures. Evaluation results reveal that CNTs-based cementitious composites demonstrate 160 %–269 % superior multifunctional performance compared to their CF-based counterparts. Furthermore, the feasibility of potential applications of carbon-based cementitious composites in concrete construction is extensively discussed, encompassing diverse areas such as thermoelectric energy harvesting, intelligent structural adjustment, cathodic protection systems, snow and ice melting, electromagnetic shielding, and structural health monitoring. The research outcomes presented in this study offer a systematic evaluation of a wide range of carbon-based cementitious materials, providing valuable guidelines and recommendations for engineers.

Nanoscale-Confined Synthesis of 2D Metal Compounds for Electrochemical Applications.

2D metal compounds, such as transition metal dichalcogenides (TMDs), layered double hydroxides (LDHs), and MXenes, are emerging as important electrocatalyst materials in the transition to a sustainable energy future. Aided by their high surface area, electrical conductivity, and tunable electronic properties, these materials have provided a crucial research thrust in enhancing the efficiency of green hydrogen production, fuel cells, and carbon reduction processes. Most importantly, the synthesis of nanostructured 2D compounds, while challenging, is the key to optimizing their catalytic performance. Recent advancements in this field have highlighted the potential of 2D metal compounds in revolutionizing energy conversion technologies, which entails the discovery of new material compositions, the development of novel synthetic routes, and the integration of these materials into practical energy conversion systems. This review presents an overview of the distinctive characteristics of nanoscale-confined 2D metal compounds, the challenges encountered in their synthesis, and electrochemical applications.

Modeling and Experiments on Temperature and Electrical Conductivity Characteristics in High-Temperature Heating of Carbide-Bonded Graphene Coating on Silicon.

A novel non-isothermal glass hot embossing system utilizes a silicon mold core coated with a three-dimensional carbide-bonded graphene (CBG) coating, which acts as a thin-film resistance heater. The temperature of the system significantly influences the electrical conductivity properties of silicon with a CBG coating. Through simulations and experiments, it has been established that the electrical conductivity of silicon with a CBG coating gradually increases at lower temperatures and rapidly rises as the temperature further increases. The CBG coating predominantly affects electrical conductivity until 400 °C, after which silicon becomes the dominant factor. Furthermore, the dimensions of CBG-coated silicon and the reduction of CBG coating also affect the rate and outcome of conductivity changes. These findings provide valuable insights for detecting CBG-coated silicon during the embossing process, improving efficiency, and predicting the mold core's service life, thus enhancing the accuracy of optical lens production.

Effect of Mechanical Alloying Time on Microstructure, Hardness and Electrical Conductivity Properties of Cu-B4C Composites

This study aims to investigate the effect of mechanical alloying time on the microstructure, hardness, and electrical conductivity properties of copper (Cu) matrix boron carbide (B4C) reinforced composites. Cu-B4C composites with 2% B4C by volume were subjected to mechanical alloying processes for 0, 1, 5, 10, and 20 hours. The microstructure and phase formation of the composites were examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Hardness measurements of the composites were conducted using the microhardness measurement method, and density values were determined using the Archimedes principle. The electrical conductivity values of the samples were measured in terms of the international annealed copper standard (%IACS) based on the eddy current principle. SEM images revealed a more homogeneous distribution of B4C particles in the Cu matrix as the mechanical alloying time increased. Hardness values showed significant increases with the increasing mechanical alloying time, reaching the highest value in the 20 h milled sample with a 90.86 value. The effect on electrical conductivity values was noteworthy, with a measurement of 63% IACS at 0 hours and 25% IACS at 20 hours of mechanical alloying.

A Comparative Study of Single and Dual Sintering Processes of Metal Nanoparticles for Flexible Electronics Application

The introduction of metallic nanoparticles (NPs) has revolutionized the fabrication of flexible electronic devices. Metallic NPs have numerous applications in the electronics industry due to their unique shape and size‐dependent properties compared to their bulk counterparts. However, the application of metallic NPs requires additional post‐processing procedures to remove stabilizing agents and additives, to achieve superior electrical conductivity. Herein, the sintering of printed metal NP patterns, including silver (Ag) and copper (Cu) NPs, fabricated on flexible polyimide substrates is explored using single and dual sintering methods. The single sintering methods involve exposing the printed metal NPs to either laser irradiation or thermal treatment. In the case of the dual sintering methods, one approach is to subject the printed metal patterns to thermal treatment followed by laser irradiation, while the other approach involves exposing the printed metal patterns to laser irradiation followed by thermal treatment. Moreover, this study identifies and compares the effects of these various sintering methods on the physical, electrical, chemical, and mechanical properties of the Ag and Cu NP patterns. Finally, the study suggests that dual sintering methods are more effective in improving the electrical conductivity and mechanical properties of the NP patterns under optimized sintering conditions.

Conductive dual-network hydrogel-based multifunctional triboelectric nanogenerator for temperature and pressure distribution sensing

Conductive hydrogels are gaining attention in flexible electronics due to their high electrical conductivity and stretchable mechanical properties. Utilizing conductive hydrogels as electrodes in triboelectric nanogenerators (TENG) offers a promising avenue for developing versatile, flexible devices. However, the preparation of a multifunctional hydrogel-based TENG remains a challenging task. Here, a dual-network hydrogel TENG is denoted as DNH-TENG. It comprises poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS)/poly (vinyl alcohol) (PVA)/carboxylated multi-walled carbon nanotube (MWCNT-COOH) and offers the advantages of straightforward fabrication, versatile applications, and efficient output performance. Preparing a double network by combining a conductive network with a soft network improves the tensile properties but reduces its conductivity significantly. Further doping MWCNT-COOH with the dual-network leads to a conjugation effect and hydrogen bonding. This enhancement fortifies the hydrogel structure and augments the electrode's conductivity and mechanical properties. In single electrode mode, the DNH-TENG exhibits a short-circuit current of 16.2 μA, a transfer charge of 97.3 nC, and an open-circuit voltage of 270.5 V. Furthermore, DNH-TENG exhibits an impressive stretchability, allowing it to be extended to 566%. Using DNH-TENG's exceptional stretchability and ultrahigh sensitivity to mechanical and temperature stimuli, we designed DNH-TENG-based sensor arrays to showcase temperature and pressure distribution monitoring applications.

Optimizing preparation conditions and characterizing for CoxPt1-x alloy cylindrical nanowires fabricated by electrodeposition on nanoporous polycarbonate membranes

This study investigated the influence of the preparation conditions on the Co composition, crystal structure, and magnetic and electric conduction properties of cylindrical CoxPt1-x alloy nanowires having 0.08 ≤ x ≤ 0.90, which were electrodeposited on nanoporous templates. When prepared with an optimal concentration ratio of Co and Pt aqueous solutions and electrodeposition potentials, highly oriented crystal structures of fcc Co-Pt (111) was obtained in CoxPt1-x nanowires (0.58 ≤ x ≤ 0.80). Nanowires with (111)-oriented fcc Co-Pt crystals exhibited average lengths and diameters of 5.8–10.8 μm and 130 nm, respectively, and showed an easy axis of magnetocrystalline anisotropy in the longitudinal direction of the nanowire. These results indicate a direct correlation between the crystal structure and magnetic properties. The concentration ratio of Co and Pt in the electrolytes and the electrodeposition potentials for fabricating CoxPt1-x alloy nanowires using the diluted Co composition (0.08 ≤ x ≤ 0.25) were determined. These nanowires were polycrystalline and had a small saturation magnetization. Furthermore, the anisotropic magnetoresistance (AMR) for a single CoxPt1-x nanowire was measured to estimate the domain wall (DW) width in the single CoxPt1-x nanowire. The value of the magnetoresistance (MR) ratio for the single nanowire (0.58 ≤ x ≤ 0.80) with highly (111)-oriented fcc Co-Pt crystal was 0.082–0.23 %, and the estimated value of DW width was 17–25 nm. These findings provide valuable information for constructing three-dimensional magnetic memory devices.

Magnetron-Sputtered Long-Term Superhydrophilic Thin Films for Use in Solid-State Cooling Devices

Pulse-magnetron-sputtered long-term superhydrophilic coatings have been synthesized to functionalize the surfaces of solid-state cooling devices, e.g., electrocaloric heat pumps, where not only a complete wetting of the surface by a fluid is intended, but also fast wetting and dewetting processes are required. The coatings consist of a (Ti,Si)O2 outer layer that provides lasting hydrophilicity thanks to the mesoporous structure, followed by an intermediate WO3 film that enables the reactivation of the wettability through visible light irradiation, and a W underlayer which can work as a top electrode of the electrocaloric components thanks to its suitable electrical and thermal conductivity properties. Process parameter optimization for each layer of the stack as well as the influence of the microstructure and composition on the wetting properties are presented. Finally, water contact angle measurements, surface energy evaluations, and a contact line dynamics assessment of evaporating drops on the coatings demonstrate that their enhanced wetting performance is attributed not only to their intrinsic hydrophilic nature but also to their porous microstructure, which promotes wicking and spreading at the nanometric scale.

Coal-derived conductive pavement for winter de-icing: prototype, modeling, and simulation

Existing pavement de-icing methods result in high installation and maintenance costs, traffic delays, excessive weariness and corrosion, and negative environmental and safety impacts. To overcome these challenges, this paper presents an innovative pathway to designing and constructing smart self-heating pavements using a low-cost coal-char bearing asphalt material. The conductive asphalt incorporates coal char, i.e., a key byproduct of the coal pyrolysis process, into the Stone Mastic Asphalt (SMA) mixture. This asphalt containing coal-derived solid carbon exhibits highly tailorable electrical conductivity, satisfactory mechanical and thermophysical properties, and superior cost-efficiency as compared to other conductive pavement materials. The de-icing performance was also demonstrated by laboratory experiments on a bench-scale prototype. Furthermore, an efficient thermal network model was developed and validated by experiments to investigate the transient thermal behavior and energy performance of the Ohmic heating pavement system. The whole-year energy simulation case studies were conducted on a bridge pavement with an annual energy use of 24.6–1444.8 kWh/m2, showcasing its potential in field applications across cool humid, cold humid, and subarctic/arctic climate zones.

Role of cyclodextrin inclusion complexes assembled in the fast-dissolving structures of electrospun gelatin mats to extend the release of menthol

In this study, inclusion complexes (ICs) of menthol with various cyclodextrins (CDs) [α-CD, β-CD, γ-CD, (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD), and methyl-β-cyclodextrin (M-β-CD)] were prepared, and the ICs with the highest encapsulation efficiency were applied in the electrospun gelatin mats to extend the release of menthol. Electrospinning feed solutions were evaluated based on surface tension, zeta potential, electrical conductivity, and rheological properties. The diameter and morphology of the pure gelatin and the CDs-loaded gelatin mats were analyzed using microscopy (FESEM and AFM). The results confirmed that CD loading leads to a decrease in the diameter of the nanofibers. The longest disintegration time belonged to the gelatin mat containing the β-CD complex. Comparison of the FTIR spectrum and XRD patterns of gelatin mats containing menthol-loaded CD complexes with the pure compounds confirmed the successful encapsulation of menthol inside the cavity of the CD, and the disappearance of the crystalline state of electrospun gelatin mats. Applying the electrospun gelatin mats as a fast-dissolving structure for the menthol-loaded inclusion complexes increased its thermal stability. In the bioadhesive test, the lowest force required to separate the gelatin mat from the skin model was obtained in the menthol-containing β-CD gelatin mat (6.21 ± 1.01 g). The menthol release from the pure gelatin mats was much faster than the electrospun mats containing CD complexes. Peppas-Sahlin and Fickian diffusion (Case-I) were the best-fitted model and menthol release mechanism, respectively.

Effects of Cr2O3 doping on crystallization behavior and electrochemical properties of Li2O–Al2O3–TiO2–P2O5–SiO2 glass-ceramics

Bulk glass-ceramic solid electrolytes of the Li2O–Al2O3–TiO2–P2O5–SiO2 system were prepared by melt-quenching and one-step heat treatment method in this work. The effects of the gradual substitution of Al3+ by Cr3+ and the elevation of the heat treatment temperature on the phase composition, microstructure, and ionic conductivity of the solid electrolytes were systematically investigated. The results show that the major crystalline phase is LiTi2(PO4)3, and the conductivity of the glass-ceramics initially enhances and then decreases as the Cr2O3 content increases from 0 mol% to 3 mol%. The highest conductivity is obtained when the Cr2O3 content is 2 mol%, measuring 4.45 × 10−4 S/cm at 25 °C. Additionally, the mechanism of the surface exfoliation of the glass-ceramics and the enhancement achieved by doping with Cr3+ are explained according to microstructure analysis. This work provides a simple method to enhance the electrical conductivity and physical properties of LATP glass-ceramic solid electrolytes, which is of great significance for the design of lithium-ion solid electrolytes.