Electrical Conductivity Behavior Research Articles

Effect of graphite fillers on electrical and thermal conductivity in epoxy-based composites: Percolation behavior and analysis

This work investigated a method for producing epoxy-based composites using various graphite fillers, such as natural, synthetic, and thermally expanded graphite. The study aimed to determine the impact of the filler type, size, and volume fraction on the composites’ thermal and electrical conductivity. Results indicate that the percolation model accurately represents electrical and thermal conductivity behavior, with graphite fillers forming conductive clusters in the polymer matrix. The percolation threshold for electrical conductivity varies between 2.8 and 8.5 vol.%, while for thermal conductivity, it ranges from 5.0 to 18.0 vol.%, which is twice that of electrical conductivity. This observation is due to both the electron transfer tunneling effect and the necessity of higher filler content to facilitate effective phonon transport. Notably, composites filled with thermally expanded graphite exhibit lower percolation thresholds. Understanding percolation behavior facilitates the prediction and optimization of composites with specific electrical and thermal properties for diverse applications.

Analysis of the electrical conductivity and activation energies of bismuth titanate (Bi4Ti3O12)

In this study, bismuth titanate (Bi4Ti3O12) was synthesized from pure solid compounds and structurally characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The electrical properties were evaluated by measuring the electrical conductivity of Bi4Ti3O12 at various oxygen partial pressures (pO2 = 10−5 and 10−8 atm) and temperatures (450 °C-750 °C). The electrical conductivity behavior was assessed during the heating and cooling processes. The material activation energies were determined based on the heating curve, which displayed Arrhenius-type behavior and activation energy slope changes, which could be attributed to point defects. When the temperature was increased from 450 °C to 750 °C at oxygen partial pressures pO2 = 10−5 atm, the electrical conductivity increased by about 62.9 %, whereas when the temperature decreased from 750 °C to 450 °C, the electrical conductivity was reduced by 35.95 %. The electrical behavior of Bi4Ti3O12 was analyzed by establishing its electrical conductivity and chemical activity under different oxygen partial pressures and heating-cooling conditions can allow the synthesis of materials with attractive characteristics for electronic applications.

Bayesian inference of hysteretic behavior of unfrozen water content and electrical conductivity in saturated frozen rocks

Electrical conductivity is a fundamental geophysical parameter of electrical and electromagnetic techniques. It is widely used to non-intrusively assess and monitor physical and chemical properties in cold regions (i.e., liquid water saturation, ice content, salinity, and temperature). However, the significant hysteretic behavior observed in the temperature-dependent physical properties of frozen porous media (i.e., unfrozen water saturation and electrical conductivity) remains difficult to interpret during freezing and thawing processes. Such hysteretic characteristics are mainly associated with the connectivity and irregularity of the pore network. In this study, a physically-based model is developed to consider micro-scale heterogeneities in finite-size percolation during the freezing and thawing processes using an upscaling procedure. We introduce two simple parameters to describe the constrictivity and irregularity of the pore network: the radial factor and length factor of the pore throats within the capillaries. The proposed model accounts for the hysteretic mechanisms, upscaling single-pore hysteresis at the individual pore scale and pore irregularity hysteresis at the pore network scale. Furthermore, we use a series of experimental datasets to test the proposed hysteretic model. Our findings show an excellent agreement between the predicted values and the experimental dataset, indicating that our new physically-based models can effectively predict and interpret hysteretic behaviors in the temperature-dependent physical parameters of frozen rocks during freezing and thawing processes.

Aspect ratio-dependent volume resistivity in unidirectional composites: Insights from electrical conduction behavior

The electrical properties of carbon fibers serve as the foundation for the multifunctional applications of carbon fiber-reinforced composite structures. In scenarios that exploit the electrical characteristics of materials, accurate estimation of electrical resistivity stands as a critical factor. This study endeavors to elucidate the electrical conduction behaviors in unidirectional composites with different fiber orientation angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) and aspect ratios, thereby deriving the volume resistivity within an arbitrary Cartesian coordinate system. Employing thermal infrared imaging technology and finite element analysis, we identified distinctive electrical conduction behaviors associated with aspect ratios in carbon fiber composite plates. Notably, a critical aspect ratio exists wherein the diagonal yarn is the only conductive path between two electrodes. Below this critical threshold, no direct conductive path exists, and current flows through the shortest distance between parallel yarns. Conversely, beyond the critical aspect ratio value, multiple yarns form conductive paths between the two electrodes. Based on the electrical conduction behavior of unidirectional composites under different angles and aspect ratios, the volume resistivity with finite boundaries was derived and examined under an arbitrary Cartesian coordinate basis.

Research on cadmium-injected manganese ferrite made through the sol-gel method, focusing on its structure, magnetic properties, electrical conductivity, and electrochemical behavior

Cadmium was integrated into Manganese ferrite (Mn1-xCdxFe2O4) nanofine particles via the sol-gel method for potential sensing uses. The X-ray diffraction (XRD) revealed that the particles contained a cubic spinel structure and FTIR spectroscopy was employed to identify the metal-oxide (MO) stretching, bending and stretching vibrations. The purity of the samples and the surface feature were scrutinized using an energy dispersive X-ray (EDAX) spectrum and scanning electron microscope (SEM). The magnetic properties were examined as ferromagnetic found through a vibrating sample magnetometer (VSM). An LCR meter gives information on dielectric constants (ε’ & ε’’), loss (tanδ) with AC conductivity (σAC), and cyclic-voltammetry was used to evaluate the electrochemical properties, including voltage/current responses (V/I), Nyquist frequency, voltage/current response to SCR, and phase angle as a function of frequency. From the results the magnetic, dielectric, electrochemical behavior and etc., can be interpreted and discussed extensively.

The influence of graphene oxide on the microstructure and properties of ultrafine-grained copper processed by high-pressure torsion

New metal matrix nanocomposites with enhanced thermal stability were produced in a three step process consisting of mechanical milling, spark plasma sintering and High-Pressure Torsion (HPT). The nanocomposites consisted of a copper matrix and the addition of 1 wt% Graphene Oxide (GO) as a reinforcement. A nanocrystalline microstructure, enhanced hardness and improved thermal stability were achieved. The grain size of the nanocomposites was ∼55 nm which is almost four time smaller than for Cu HPT at 210 nm. Hardnes and ultimate tensile strength of the nanocomposites reach 250 Hv and 700 MPa, respectively, which was more than three times higher than for the initial material. The most important result is that the nanocomposites remained ultrafine-grained up to 500 ⁰C whereas the Cu HPT fully recrystalized after annealing at 300 ⁰C The report also includes an investigation of the electrical conductivity of the copper-based composite which was slightly better than for copper after HPT together with the wear behaviour of this material. This is one of the first reports on copper reinforced with graphene oxide composites produced by HPT and it gives information on its thermal stability, electrical conductivity and wear behaviour together with the microstructural characteristics and mechanical properties.

Phase and defect structures of MnO2‐doped 75BiFeO3–25BaTiO3 ceramics and their effects on electrical properties

AbstractBismuth ferrite (BiFeO3)‐based high‐temperature piezoelectric ceramics have high Curie temperatures and excellent thermal stability; however, their applications are limited by inadequate piezoelectric performance due to large coercive fields and high leakage conduction. This study investigates the impact of MnO2 doping on the phase transition, defect structure, domain morphology, as well as the dielectric, ferroelectric, and electrical conduction behaviors of 75BiFeO3–25BaTiO3 ceramics sintered under an oxygen atmosphere. A structural transformation from distorted rhombohedral to pseudo‐cubic symmetry was observed with increasing MnO2 content, accompanied by domain fragmentation. MnO2 doping at an appropriate level inhibited defects such as and . Regarding electrical properties, the reduction in rhombohedral distortion and enhancement in the pseudo‐cubic phase after MnO2 doping resulted in decreased remanent polarization and electrostrain, which could potentially hinder piezoelectric response. However, appropriate MnO2 doping effectively reduced leakage conduction, significantly enhancing the poling efficiency of the ceramics. The maximum d33 value of 107 pC/N and kp of 0.36 were achieved at an MnO2 doping content of 0.1 wt.%. Excessive MnO2 addition may generate defect dipoles, as indicated by increased coercive field (Ec) and dielectric loss. The observed increase in high‐temperature resistivity with MnO2 content is primarily attributed to reduced grain size and increased concentration of mobile defects. This study provides valuable insights for further research on the application of 75BiFeO3–25BaTiO3 systems in high‐temperature piezoelectric devices.

Electrical conductivity of Ni ferrite nanofluids: An experimental study on the effects of temperature, volume fraction, and base fluid

This study investigates the electrical conductivity of NiFe2O4 nanofluids in water and ethylene glycol (EG) as base fluids, aiming to understand how varying volume fractions (φ= 0 %, 0.1 %, 0.25 %, 0.45 %, 0.7 %, and 1 %) and temperatures (20–70°C) influence electrical conductivity. NiFe2O4 nanoparticles were synthesized using the chemical co-precipitation method and characterized through X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), and Energy Dispersive Spectroscopy (EDS). The results revealed that at 70°C, the electrical conductivity of NiFe2O4-water nanofluid increased by 1100 % within the volume fraction range of 0–1 %. For NiFe2O4-EG nanofluid, the increase in electrical conductivity was even more significant, reaching 1235 % within the same volume fraction range. Similarly, at a 1 % volume fraction within the temperature range of 20–70°C, the electrical conductivity of NiFe2O4-water nanofluid increased by 136 %, while for NiFe2O4-EG nanofluid, it was 370 %. These findings indicate that both temperature and volume fraction significantly enhance the electrical conductivity of the nanofluids, with a more pronounced effect observed in the NiFe2O4-EG nanofluid compared to the NiFe2O4-water nanofluid. The study validated Shen et al.'s model for electrical conductivity in nanofluids, contrasting with Maxwell's model. The novelty of this work lies in the comprehensive analysis of the electrical conductivity behavior of these nanofluids, which has not been extensively reported in the literature. These findings have potential applications in heat transfer enhancement and magnetic-targeted drug delivery.

Investigation of electrical conductivity and oxygen relaxation behavior for BaBi0.98Sr0.02Nb5-xTixO15-δ ceramics

Investigation of electrical conductivity and oxygen relaxation behavior for BaBi0.98Sr0.02Nb5-xTixO15-δ ceramics

Electrical conductivity behaviour of aqueous solutions of methylene blue at different temperatures using impedance spectroscopy

Electrical conductivity behaviour of aqueous solutions of methylene blue at different temperatures using impedance spectroscopy

Bridging papermaking and hydrogel production: Nanoparticle-loaded cellulosic hollow fibers with pitted walls as skeleton materials for multifunctional electromagnetic hydrogels

Electromagnetic hydrogels have attracted significant attention due to their vast potential in soft robotics, biomedical engineering, and energy harvesting. To facilitate future commercialization via large-scale industrial processes, we present a facile concept that utilizes the specialized knowledge of papermaking to fabricate hydrogels with multifunctional electromagnetic properties. The principles of papermaking wet end chemistry, which involves the handling of interactions among cellulosic fibers, fines, polymeric additives, and other components in aqueous systems, serves as a key foundation for this concept. Notably, based on these principles, the versatile use of chemical additives in combination with cellulosic materials enables the tailored design of various products. Our methodology exploits the unique hierarchically pitted and hollow tube-like structures of papermaking grade cellulosic fibers with discernible pits, enabling the incorporation of magnetite nanoparticles through lumen loading. By combining microscale softwood-derived cellulosic fibers with additives, we achieve dynamic covalent interactions that transform the cellulosic fiber slurry into an impressive hydrogel. The cellulosic fibers act as a skeleton, providing structural support within the hydrogel framework and facilitating the dispersion of nanoparticles. In accordance with our concept, the typical hydrogel exhibits combined attributes, including electrical conductivity, self-healing properties, pH responsiveness, and dynamic rheologic behavior. Our approach not only yields hydrogels with interesting properties but also aligns with the forefront of advanced cellulosic material applications. These materials hold the promise in remote strain sensing devices, electromagnetic navigation systems, contactless toys, and flexible electronic devices. The concept and findings of the current work may shed light on materials innovation based on traditional pulp and paper processes. Furthermore, the facile processes involved in hydrogel formation can serve as valuable tools for chemistry and materials education, providing easy demonstrations of principles for university students at different levels.

Design, structural, and electrical conduction behavior of Zr-modified BaTiO3-BiFeO3 perovskite ceramics

This study employs the solid-state reaction method to synthesize [(Ba0.7 Bi0.3) (Ti0.7-y Zry) Fe0.3] O3 (y = 0.0, 0.2, 0.3, 0.4, 0.6) for investigating their structural and DC conduction behavior. XRD analysis suggests a perovskite phase for all the compositions having a cubic crystal structure. Initially, average crystallite size increases for y ≥ 0.3 and then decreases for y = 0.4. The temperature-dependent DC electrical conductivity demonstrated the semiconducting nature for all the compositions. The introduction of Zr modifies the material’s structure and electrical properties evident in the observed variations in crystallite size and conductivity behavior. These findings contribute to the understanding of Zr-modified [(Ba0.7 Bi0.3) (Ti0.7-y Zry) Fe0.3] O3 ceramics, shedding light on their potential applications in semiconductor devices and solid-state electronics. The investigation underscores the importance of tailoring composition parameters for fine-tuning material characteristics, opening avenues for optimized utilization in electronic and energy-related technologies

Highly conductive and durable nanocomposite hard coatings of carbon fiber reinforced thermoplastic composites against lightning strikes

The growing use of thermoplastic composites (TPCs) like low-melting polyaryletherketone (LM-PAEK) matrices reinforced with unidirectional carbon fiber (CF) in aircraft structures presents a significant challenge in terms of lightning strikes and electromagnetic interference shielding during aircraft operations. This is due to the weak electrical conductivity of TPC structures, which results in widespread damage when struck by lightning. The repair and maintenance of these extended damaged sites can increase operational costs and loss of flights. Several lightning strike protection (LSP) systems have been developed and implemented to address these concerns. This study evaluated a highly conductive coating with a low filler rate for its effectiveness as an LSP solution for TPCs on exterior aircraft surfaces. The TPC panel without any coatings was first studied. Subsequently, the level of conductivity was increased by incorporating the nanoscale conductive fillers, silver-coated copper (Ag/Cu) nanoflakes, with a silver content of 20 wt.% (Ag20/Cu) and 30 wt.% (Ag30/Cu), correspondingly, into the coating at two loadings of 55 wt.% and 70 wt.% in an epoxy carrier for the surface coatings. The behavior of electrical and surface conductivity was thoroughly examined to understand the impact of Ag/Cu with a high aspect ratio and the effectiveness of the LSP solution. In addition, the spray-coated TPC panels underwent rigorous Zone 2A lightning strike testing using simulated lightning current, in agreement with the industry standard of Society of Automotive Engineers (SAE) Aerospace Recommended Practice (ARP) 5412B. Despite the higher resistance due to the lower conductive coating weight, the TPC panels with Ag30/Cu at loading of 70 wt.% achieved better results than those with Ag30/Cu at loading of 55 wt.%. This is evidenced by the minor structural delamination and CF breakage on the front surface, which proposes a new economic route for a sustainable post-processed LSP system in the aviation industry.

Influence of Thermal Aging on Space Charge Characteristics and Electrical Conduction Behavior of Cross-Linked Polyethylene Cable Insulation.

The aging of cable insulation presents a significant threat to the safe operation of cables, with space charge serving as a crucial factor influencing cable insulation degradation. However, the characteristics related to space charge and conduction current behavior during thermal aging remain unclear. This study focused on the thermal aging of cross-linked polyethylene (XLPE) material and utilizes a combined pulse electro-acoustic (PEA) and conduction current testing system to analyze the space charge and conduction current characteristics in the sample under varying electric fields and temperatures. The average charge density, short-circuit residual electric field, electric field distortion rate, and conduction current were studied. The findings indicate that the space charge in the samples following thermal aging is predominantly governed by the injected charge. The amorphous region of XLPE decreases, while the cross-linking degree increases after aging, thereby facilitating charge carrier migration within the sample and reducing the generation of charge carriers through thermal pyrolysis. The minimum temperature required for charge injection is reduced by thermal aging. Furthermore, modifications in conduction current, residual electric field, and average charge density indicate that thermal aging has the potential to alter the microstructure and trap characteristics of XLPE. This study provides empirical evidence to elucidate the underlying mechanism of cable insulation aging.

Treatment efficiency and recovery in sand filters for on-site wastewater treatment: Column studies and reactive modelling

This study examined the adsorption capacity and treatment efficiency of sand filters in on-site treatment systems for cold climate regions. The effects of different operating conditions, porosity and kinetics parameters were investigated in column experiments and COMSOL Multiphysics® modelling, to comprehensively reveal the mechanisms and optimize treatment efficiency of nitrogen (N) and phosphorus (P) removal in a field tidal flow constructed wetland (TFCW), treating effluent from a package treatment plant with P filter material. The results from column experiments with sand showed that Total-P adsorption rate was dependent on feed water quality (Septic tank >0.77 ± 0.06 g kg−1; Biotreatment >0.41 ± 0.07 g kg−1; Reactive material Polonite® <0.18 ± 0.07 g kg−1). In the field TFCW trial, Total-P adsorption in the top layer (>1.42 ± 0.55 g kg−1) and middle layer (>1.06 ± 0.51 g kg−1) was twice that in laboratory columns, due to strong interaction with the air-water interface and use of fluctuated domestic wastewater solutions. The breakthrough curve (BTCs) of the coarse sand matched the physical behaviour of tracer electrical conductivity (EC) in effluent from the sand column experiments. The modelling results demonstrated that high filter porosity and low hydraulic load were significant factors for optimal removal of NH4–N, Total-N, PO4–P, Total- P in the top layer (>99.95 ± 0.03 %, 44.37 ± 28.75%, 70.89 ± 28.30%, 76.18 ± 20.3%), middle layer (>98.94 ± 1.77%, 18.23 ± 23.04%, 76.62 ± 28.73%, 65.40 ± 31.85%) and deep layer (>99.99 ± 0.02%, 65.50 ± 20.64%, 75.53 ± 23.16%, 41.54 ± 28.81%) in the TFCW system, respectively. The results show that on-site wastewater treatment in cold climate TFCW can be applied as a technology to polish effluent from a three-step pretreatment system. However, hydraulic optimization is an important factor for the design of the TFCW to receive a successful long-term operating system.

Comparison of Electrical Conductivity and Schottky Behavior of 4‐[2‐(9‐anthryl)vinyl]pyridine Based Two 1D Coordination Polymers of Zn(II) and Cd(II)

AbstractWith the increase in demand of electronic devices in the modern civilization, research in material science is being projected to grow in faster rate. In this facet, coordination polymer (CP) based electronic device is one of the promising candidates to the material researchers. Herein, two new Zn(II) and Cd(II) based one‐dimensional (1D) CPs, denoted as [Zn(4‐avp)2(5‐nip)] ⋅ (solvent)x (1) and [Cd(4‐avp)(5‐nip)(CH3OH)] (2) have been synthesized using relatively less explored highly conjugated polycyclic aromatic hydrocarbon (PAH) based monodentate ligand, 4‐[2‐(9‐anthryl)vinyl]pyridine (4‐avp) and bidentate linker 5‐nitroisophthalic acid (H25‐nip). In this instance, the CP 1 creates 1D chain polymer, while CP 2 is made up with 1D ladder polymer. It is interesting to note that both the CPs exhibit semiconducting nature and generate metal‐semiconductor (MS) junction Schottky barrier diodes (SBDs). However, Cd‐based CP 2 shows higher charge transport as compared to Zn‐CP 1, which could be due to stronger π⋅⋅⋅π contacts as well as larger size of Cd metal in CP 2. The experimental results are well corroborated with theoretical density of states (DOS) calculations.

Design and Optimization of NR-Based Stretchable Conductive Composites Filled with MoSi2 Nanoparticles and MWCNTs: Perspectives from Experimental Characterization and Molecular Dynamics Simulations.

Stretchable conductive composites play a pivotal role in the development of personalized electronic devices, electronic skins, and artificial implant devices. This article explores the fabrication and characterization of stretchable composites based on natural rubber (NR) filled with molybdenum disilicide (MoSi2) nanoparticles and multi-walled carbon nanotubes (MWCNTs). Experimental characterization and molecular dynamics (MD) simulations are employed to investigate the static and dynamic properties of the composites, including morphology, glass transition temperature (Tg), electrical conductivity, and mechanical behavior. Results show that the addition of MoSi2 nanoparticles enhances the dispersion of MWCNTs within the NR matrix, optimizing the formation of a conductive network. Dynamic mechanical analysis (DMA) confirms the Tg reduction with the addition of MWCNTs and the influence of MoSi2 content on Tg. Mechanical testing reveals that the tensile strength increases with MoSi2 content, with an optimal ratio of 4:1 MoSi2:MWCNTs. Electrical conductivity measurements demonstrate that the MoSi2/MWCNTs/NR composites exhibit enhanced conductivity, reaching optimal values at specific filler ratios. MD simulations further support experimental findings, highlighting the role of MoSi2 in improving dispersion and mechanical properties. Overall, the study elucidates the synergistic effects of nanoparticles and nanotubes in enhancing the properties of stretchable conductive composites.

Investigation of electronic, ferroelectric and local electrical conduction behavior of RF sputtered BiFeO3 thin films

Most of the applied research on BiFeO3 (BFO) focuses on magnetoelectric and spintronic applications. This calls for a detailed grasp of multiferroic and conduction properties. BFO thin films with (100) epitaxial growth has been deposited on a LaNiO3 (LNO) buffered Pt/Ti/SiO2/Si(100) substrate using RF magnetron sputtering. The film formed at 15 mTorr, 570 °C, and with Ar/O2 4:1 had a reasonably high degree of (100)-preferential orientation, the least surface roughness, and a densely packed structure. We obtained ferroelectric loops with strong polarization (150 μC cm−2). The leakage current density is as low as 10–2 A cm−2 at 100 kV cm−1, implying that space-charge-limited bulk conduction (SCLC) was the primary conduction channel for carriers within BFO films. Local electrical conduction behavior demonstrates that at lower voltages, the grain boundary dominates electrical conduction and is linked to the displacement of oxygen vacancies in the grain boundary under external electric fields. We hope that a deeper understanding of the conduction mechanism will help integrate BFO into viable technologies.

An electro-mechanical contact model for particulate systems

This study presents an electro-mechanical contact model to investigate the electrical response within a particulate system under mechanical loading. The model considers the electrical resistance across particle-to-particle and particle-to-wall contacts by formulating bulk and contact resistances, separately. Hertz and Holm's models are utilised for the contact resistance in the overlapping region. The bulk resistance for a particle is estimated considering particle geometry transformations during the compression. The proposed electro-mechanical contact model is verified and validated against published analytical solutions and experimental data. Finally, the contact model is applied to simulate a high-pressure torsion test to investigate the influence of three different materials on the electrical conduction properties of the system after particle fragmentation. The intensity distributions of electric potential, current and resistance of the granular system are analysed at both particle and system scales. An electroactivity index is proposed for evaluating the contribution of each fragment sieve cut on the bulk electrical conduction behaviour.

Micro contact modeling of electrical current conduction behavior between carbon fiber yarns

Electrical contact conduction between carbon fiber yarns is one of the important current conduction paths inside carbon fiber composites and is easily affected with fabric reinforcement structure and manufacturing process. Here we proposed a micro contact model to predict the contact resistance and to reveal the current conduction behavior between carbon fiber yarns. The model takes into account tunneling effect and yarn geometric structure. The fiber contact probability between yarns was determined based on the statistical characteristic of the fiber height on the yarn surface. The relationship between the yarn contact resistance in plain weave fabric and out-of-plane force was measured and the experimental results agree well with the model. We found that the current conduction between yarns depends on contact conduction between fibers and the contribution of tunneling conduction is negligible. The proposed micro contact model provides insight into the current conduction behavior between carbon fiber yarns and is meaningful for the electrical conductivity design of carbon fiber composites.