Electrical Properties Of Composite Materials Research Articles

Photocatalytic activity of polyaniline‐potassium doped nickel oxide nanocomposites: A comprehensive investigation on multifaceted properties

AbstractPolyaniline‐potassium doped nickel oxide nanocomposites (PANI/KNO) were efficiently synthesized via an in situ chemical oxidation method, meticulously confirmed by comprehensive x‐ray diffraction, Fourier transformation infrared spectroscopy, energy dispersive x‐ray spectroscopy, selected area electron diffraction, and x‐ray photoelectron spectroscopy analyses. The crystallite size and strain exhibited distinct behaviors, while field emission scanning electron microscopy revealed a blend of irregular spherical shapes and nanofibers, further confirmed by high resolution transmission electron microscopy. These composites exhibited significantly enhanced thermal stability, surpassing PANI by 1.39 times, and showcased a band gap exceeding 3 eV, along with multiple photoluminescence peaks at room temperature (RT). Moreover, their RT AC conductivity experienced a remarkable surge by 4.91 times compared to pure polyaniline. Jonscher's Power Law model and the Havriliak–Negami relaxation model are employed to elucidate the electrical properties of composite materials. The composites displayed nonDebye relaxation behavior with increased conductivity, as observed through impedance analysis, electrical modulus evaluation, and dielectric constant assessment. Additionally, evident superparamagnetic properties and multiple magnetic domains further contributed to their effectiveness. The PANI/KNO composite demonstrated photocatalytic efficiency, achieving over 90% degradation of methylene blue dye across four cycles, thus highlighting its superior photostability. Furthermore, investigations into its response to pH variations and scavenger activity underscored its immense potential for highly effective photocatalytic applications.

Random processes in modeling durability of building and structure

The problem of buildings and structures durability during their long-term operation in aggressive environments is discussed. It is closely connected with the problem of destruction of composite materials as a random process of birth, development, and death of defects at chemical corrosion. The content of the study is to analyze the influence of non-stationary chemical reactions occurring in real conditions on these processes. The analysis is carried out taking into account the incidental physical phenomena affecting corrosion, the most important of which is the diffusion of initial substances and reaction products occurring under different hydrodynamic conditions, i.e., the nature of fluid motion and its pressure which stimulates corrosion. The synthesis of three processes – chemical kinetics, diffusion, and hydrodynamics – allows us to study one of the possible scenarios of corrosion process development as a Markov process based on the statistical theory of the “weakest” link and the joint distribution of the random material and geometric parameters. Numerical analysis of changes in elastic and electrical properties of composite materials under these conditions allows us to substantiate the technology of non-destructive control of changes in the state of the structure. The research results are based on mathematical and statistical modeling.

APPLICATION OF CARBON-CARBON COMPOSITE MATERIALS FOR THE MANUFACTURE OF HIGH-TEMPERATURE HEATERS OF HEAT EXCHANGERS WITH AUTOMATIC TEMPERATURE CONTROL


 The article justifies the use of high-temperature heaters made of carbon-carbon composite material (CCCM) for the thermal unit of a silicon single crystal growth chamber. The conducted analysis confirms that the electrical properties of composite materials, specifically their specific resistance, allow for the creation of heating elements for high-temperature vacuum furnaces or furnaces operating in inert atmospheres at temperatures up to 2200°C.
 The use of heaters made from carbon-carbon composite material eliminates the main drawback of graphite heaters - uncontrolled energy dissipation during resistive heating due to the presence of transient electrical resistance at the junctions of graphite plates, and ensures a more uniform temperature field throughout the chamber volume. The capabilities in terms of the maximum permissible temperature of such a CCCM heater exceed the working temperature by more than two times, which also positively affects the service life.
 The modes of thermal processes occurring during crystal growth are determined by the technological process depending on the composition of the raw material and require high uniformity of heating in the working zone, high precision, and stability of the heater's temperature control. For precise temperature regulation, it is proposed to additionally measure the integral temperature in the chamber indirectly, which is based on measuring the electrical current passing through the heater, which is in thermodynamic equilibrium with the object. Thus, the heater is considered as a system susceptible to various thermal influences that determine the heat transfer process and the temperature change within the chamber and in the zone of the thermal unit's bricks.
 An improved structural diagram of a step-type extremal control system is proposed for automatic temperature control of a high-temperature heater using modern power electronics, sensors, microprocessors. To ensure speed and accuracy in temperature control, the pulse-phase control method implemented with modern specialized thermoregulator with PID-regulation was applied.
 Experimental tests conducted on the «Redmet-30» installation under factory conditions confirm the energy efficiency of using high-temperature heaters made of CCCM.

Fractal characterization of polyester based standard and single walled carbon nanotube modified composites

Abstract The electrical properties of composite materials over a wide frequency range are of great interest, not only for experimental applications, but also for theoretical studies such as fractal analysis. This study presents comparative analysis of alternating current (ac) conductivity and fractal structure characteristics in standard and single walled carbon nanotube (SWCNT) reinforced polymer composites based unsaturated polyester resin (UPR). The electrical characteristics of polymer matrices at 320 K have been analyzed as a function of frequency by impedance analysis method. It was found that the conductivity of the nanotube doped material in the dc conductivity region, which is the low frequency region, is independent of the frequency and takes a constant value. It was proved that conductivity obeys Jonscher’s power law toward the high frequency region. The standard sample showed an insulating behavior that exhibits continuous increase with increasing frequency. The images of the samples were obtained by scanning electron microscope (SEM) to reveal the relationship between the conductivity of the materials and their fractal properties. All samples were converted to binary format for calculations. Cellular particle density for each sample was determined according to scaling theory. Then, the surface coverage ratio, fractal dimensions, cluster densities, average cluster sizes and critical interface exponent values of the samples were calculated and compared with different samples in the literature. It was determined that the coverage ratio and fractal dimension increased when carbon nanotubes were added. In addition, it was observed that the interface critical exponent decreased when the carbon nanotube was doped.

Analysis of Load-Bearing Electrical Properties of Composite Materials Based on Homogenization Theory

In this study, the broadband dielectric spectrum of polyimide composites was examined using the homogenization theory. The findings demonstrate that the addition of boron nitride nanosheets (BNNSs) and silver nanoparticles (AgNPs) causes an increase in conductivity, dielectric constant, and dielectric loss of the composites but does not result in a surge in the three parameters; the results also demonstrate that an increase in temperature causes an increase in dielectric constant and dielectric loss of the composites. In addition, temperature has a bigger impact on the dielectric loss than it does on the dielectric constant. An increase in the amount of polarized charges and a shallower bulk trap depth can result from the addition of nanomaterials, according to research on thermally stimulated current in composite materials. The presence of the interfacial region, which made it simple to cause charge accumulation and simple to form conduction current, is primarily responsible for the significant increase in bulk conductivity of the composites at 50 Hz that occurred with the addition of more nanomaterials. The large rise in bulk conductivity of the composites at 50 Hz that happened with the addition of more nanomaterials is mostly due to the existence of the interfacial region, which made it simple to produce charge buildup and simple to form conduction current. The variation in volume conductivity when the doping ratio is less than 10 vol% is not significant due to AgNPs’ low concentration and ambiguous contribution to the conduction current. As the polarization temperature rises, the amount of polarization charges increases, but it has minimal effect on the bulk trap depth of the composites.

Preparation and Study the Electrical and Optical Properties for (PVA-PEG-Sr2O3) Nanocomposites

In the presented work, the optical and electrical properties of composite materials (PVA-PEG-Sr2O3) were measured, as the electrical properties were verified at various frequencies in range of 100 Hz-6 MHz. In addition, the experimental results showed that the increase in frequency causes a reduction in the dielectric loss (δ) and dielectric constant (ɛ), and there is an increase in ɛ due to the increase in the content of antimony oxide (Sr2O3). It increases with increasing frequency and decreases with increasing Sr2O3 content in PVA-PEG-Sr2O3 compounds, the result of the optical properties of the nanoparticles (PVA-PEG-Sr2O3) showed that the values transmittance and energy gap were reduced with the increases in the concentrations of Sr2O3 NPs, whereas the values related to extinction coefficient, absorption coefficient, optical conductivity, refractive index, and dielectric constant (imaginary, real) were increased with increase in the concentration of Sr2O3 NPs.

The effect of reinforcing with fibers and nanomaterials on the electrical properties of composite materials

Technological development depends mainly on the progress of materials so that materials must be able to withstand service conditions. Accordingly, we always move towards composite materials, by combining two or more materials and often have different properties, so that the two materials work together to give unique composite properties. The aim of this study is to study the electrical properties represented by insulation and electrical conductivity of composite materials (including epoxy (95%) and phenol formaldehyde (5%)) supported by graphite nanoparticles and glass fibers.

Photoelectric and Electrical Properties of Composite Materials Based on n-InSe and Graphite

Photoelectric and Electrical Properties of Composite Materials Based on n-InSe and Graphite

Electrical properties and fire resistance of LDPE/EVA/FLY ASH composite materials

This paper investigates the fire resistance and electrical properties of composite materials with a base polymer of ethylene vinyl acetate copolymers (EVA)-Low density polyethylene (LDPE) blending material and an additive of unmodified fly ash (FA) and modified by vinyltrimetoxysilane (MFA). The results of the fire resistance survey show that the LDPE/EVA/(FA and MFA) composite materials all have lower fire rates than the polymer blend LDPE/EVA. Fly ash particles have the potential to limit the combustion of organic polymers. Insulating properties and dielectric strength of LDPE/EVA/MFA composites are better than LDPE/EVA/FA composites. Unmodified fly ash and VTMS modified may partially reduce the insulation capacity of the polymer blend LDPE/EVA but remain within the requirements of good insulating materials.

Composite materials for printed electronics in Internet of Things applications

Printed electronics belongs to one of the most prominent electronics technologies allowing us to manufacture electronic components and devices on different kinds of substrate materials. This manufacturing technology reveals to have significant potential to be used in Internet of Things (IoT) applications. In this paper, composite materials which are suitable for the production of a variety of IoT devices are discussed. Particular attention was focused on metal- and carbon-based composite materials allowing us to form conductive parts of the IoT devices produced. Further, sensor and encapsulation materials were reviewed as well. These conductive and sensor materials comprised of micro- and nano-particles, such as silver, copper, graphene oxide and its reduced forms, carbon nanotubes, carbon black or graphene nanoplatelets. Based on the conducted analysis, it was stated that further investigations of curing methods, fillers materials and composition of composites are recommended to be carried out in order to study mechanical, thermal and electrical properties of composite materials required for IoT applications.

Dependence of electrical properties of composition material from the structure of the matrix

In the context of rising energy costs and the need to use new energy sources, works aimed at raising the surface temperature of heat radiators with reduced energy consumption are of particular importance, and it is especially important if these processes are also accompanied by the effects of self-stabilization. Bulk materials do not possess these properties. However, materials whose dielectric matrix is also an active element can provide up to 10 - 30% of the thermal energy that will be released in the material, thereby increasing the surface temperature and without increasing energy consumption. Therefore, the study of composite materials with different matrices is relevant.
 This article the influence of the matrix material on the electrical properties of composite materials was examined. It was established that the microstructure morphology of resistive materials changes significantly depending on the matrix type. In composites based on matrix AlN, for the entire range of concentrations HfC, conducting cluster is formed with a metallic conductivity. For composite systems Al2O3-HfC and Si3N4-HfC thermoactivated hopping conduction between nearest neighboring states observed. Thus, for materials based on Si3N4 matrix at temperatures up to 300°C observed reduction of charge carriers concentration with increasing temperature.
 The approximation of the temperature dependence of the electrical conductivity was carried out on the basis of the following possible variants of the nature of the electrical conductivity, namely: jump conductivity (nonlocalized states, localized states in the tails of conduction and valence bands, localized states near the Fermi level), tunneling.
 It can be assumed that the formation of conductive clusters occurred under the influence of two factors: magnetic field and mechanical loading. When using the AlN matrix, the influence of the magnetic field on the structure formation is smallest. This conclusion can be drawn from the fact that the formed conductive clusters have the appearance of a linear chain structure.

Influence of wear of carbon nanotube grown on carbon surfaces on the mechanical and electrical properties of composite materials

Carbon nanotubes grafted on carbon fibres are used to reinforce composite materials and improve their mechanical properties. The growth of the carbon nanotubes can be directly realized on the surface to obtain entangled carbon nanotubes, and the use of such reinforcements leads to increases in the mechanical properties of the composites. However, in an industrial-scale manufacturing process, different strains will be applied on the carbon nanotubes, such as friction stresses, causing the formation of a transfer film, which is always composed of carbon nanotubes without structural modification. In this study, the properties of composite materials formed by the growth of carbon nanotubes on carbon fibre reinforcement are determined in two different states of the carbon nanotubes: before the wear of the surface (carbon nanotubes entangled on the surface) and after the wear of the surface (carbon nanotubes in a transfer film state). The influence of the state of the carbon nanotubes on the electrical and mechanical properties of the composite materials is studied. No modification of the electrical and mechanical properties is observed, which means that an industrial-scale process that induces the formation of the transfer film does not modify the properties of the composite materials.

Mixed Matrix Membrane Performance Prediction for Gas Separation using Modified Models

Gas separation using membrane processes are potentially economical in industrial scale. Two parameters are used for analyzing the membrane separation performance: permeability and selectivity. There is a trade off between them for polymeric membranes that makes it impossible to increase both of them simultaneously. Molecular sieve membranes, on the other hand, exhibit high permeability and selectivity but are brittle in nature and costly. A new generation of membranes has made many hopes to use simultaneously both desired properties of polymers and molecular sieves in a structure called “mixed matrix membrane (MMM)” where a molecular sieve is incorporated within a polymer matrix. As other branches of science and engineering, having a tool to predict MMMs performance seems to be essential to save time and money for research and industrial applications. Many mathematical models were developed to predict MMMs performance based on separation performance of fillers and polymers. Maxwell model is the simplest model developed for prediction of electrical properties of composite materials but it is not perfect for all cases. Some modifications were performed on Maxwell model and some other modified models were developed for better prediction of MMMs separation performance. In this research, modified Maxwell and Bruggeman models were employed to predict gas separation performance of some MMMs in the current work and the results were acceptable for all non–ideal cases which might be occurred in MMMs structure.

Deposition Thickness Modeling and Parameter Identification for a Spray-Assisted Vacuum Filtration Process in Additive Manufacturing

To enhance mechanical and/or electrical properties of composite materials used in additive manufacturing, nanoparticles are oftentimes deposited to form nanocomposite layers. To customize the mechanical and/or electrical properties of the final composite material, the thickness of such nanocomposite layers must be precisely controlled. A thickness model for filter cakes created through spray-assisted vacuum filtration is presented in this paper, to enable the development of advanced thickness controllers. The mass transfer dynamics in the spray atomization and vacuum filtration are studied to derive solid mass, water mass, and filter cake thickness differential area models. A two-loop nonlinear constrained optimization approach is used to identify the unknown parameters in the model. Experiments involving depositing carbon nanofibers in a sheet of filter paper are used to measure the ability of the model to mimic the filtration process.

Determination of local resistivity in ceramic composites by electron microscopy

Ceramic composite materials with both conducting and insulating phases are widely used to tailor the electrical properties of ceramic components for use in heaters, LTCC-based sensors, and other applications. The electrical properties strongly depend on the homogeneity of distribution of the conducting component. Results of investigations on composites BN/TiB2, Si3N4/MoSi2, and ZrO2/Al2O3/Ti(C,N) using a low-voltage field-emission scanning electron microscope (FESEM) revealed a relationship between the phase contrast in the images and the local electrical conductivity, which made it possible to distinguish grains that made up the three-dimensional conductive network from isolated grains. With this information, the electrical properties of composite materials can be better understood and control of the reliability and aging of such materials is enabled.

РЕЗОНАТОР ФАБРИ–ПЕРО, ОБРАЗОВАННЫЙ ДВУМЯ ЭКРАНАМИ С ПРЯМОУГОЛЬНЫМИ ОТВЕРСТИЯМИ

PACS number: 41.20.–q Purpose: studies of electrodynamics properties of Fabry–Perot resonator formed by two parallel perfectly conducting screens of finite thickness with rectangular holes while its exciting by a plane wave. Design: operator method of diffraction problems solving based on the method of partial areas and the method of generalized scattering matrixes. Findings: The numerical modeling showed that module of the coefficient of plane wave reflection from the resonator is equal to zero at a fixed wavelength being prohibitive for segments of rectangular waveguides made in both screens. Here, a strong localization of electromagnetic field in the resonator volume is observed. Studying the frequencyselective properties of each screen individually it has been determined that there are no resonances of electromagnetic wave total transmission below the cut-off frequency of rectangular waveguides. It is found that with replacing one of the Fabry–Perot resonator mirrors by a solid metal plane, the amplitude of a plane wave in the resonator can increase by almost an order of magnitude as against the exciting field amplitude. Conclusions: Unique electrodynamic properties of the considered structure can find application in devices for amplifying or generating electromagnetic waves in millimeter and submillimeter bands, as well as in measuring electrical properties of composite materials with large losses. Key words: two-dimensional periodic screen, rectangular waveguide, Fabry–Perot resonator, reflection coefficient, ultraboundary waveguide Manuscript submitted 11.11.2015 Radio phys. radio astron. 2016, 21(1): 58-64 REFERENCES 1. EULER, M. and FUSCO, V., 2010. Frequency Selective Surface Using Nested Split Ring Slot Elements as a Lens with Mechanically Reconfigurable Beam Steering Capability. IEEE Trans. Antennas Propag . vol. 58, no. 10, pp. 3417–3421. DOI: https://doi.org/10.1109/TAP.2010.2055814 2. AZEMI, S. N., GHORBANI, K. and ROWE, W. S. T., 2012. 3D Frequency Selective Surfaces. Prog. Electromagn. Res . C. vol. 29, pp. 191–203. DOI: 10.2528/PIREC12033006 3. BANKOV, S. E., DUPLENKOVA, M. D. and FROLOVA, E. V., 2013. Eigenmodes of resonator on the basis of an electromagnetic crystal. Zhurnal Radioelektroniki . no. 7, pp. 1–27 (in Russian). 4. ZIRAN WU, WEI-REN NG, MICHAEL E. GEHM and HAO XIN., 2011. Terahertz electromagnetic crystal waveguide fabricated by polymer jetting rapid prototyping. Opt. Express . vol. 19, no. 5, pp. 3962–3972. DOI: https://doi.org/10.1364/OE.19.003962 5. ANTONENKO, J. V. and GRIBOVSKY, A. V., 2012. Polarization and Frequency-Selective Properties of a Double Screen of Finite Thickness with Coaxial-Sector Aperture. Radio Phys. Radio Astron . vol. 17, no. 3, pp. 276–281 (in Russian). 6. GRIBOVSKY, A. V., LYTVYNENKO, L. M. and PROSVIRNIN, S. L., 2000. Diffraction of Electromagnetic Waves on a Multi-Layer Structure of Metal Screens with Rectangular Holes. Radio Phys. Radio Astron . vol. 5, no. 2, pp. 166–170 (in Russian). 7. PEROV, A. O., KIRILENKO, A. A., DERKACH, V. N. and SALOGUB, A. N., 2015. System of two screens with the circular beyond the limits openings as the quasi-optical polarizer. Radiofizika i Elektronika . vol. 6(20), no. 3, pp. 3–10 (in Russian). 8. LITVINENKO, L. N. and PROSVIRNIN, S. L., 1984. Spectral operators of dispersion in the tasks of diffraction of waves on flat screens . Kyiv: Naukova dumka (in Russian). 9. GRIBOVSKY, A. V., PROSVIRNIN, S. L. and REZNIK I. I., 1997. Reflecting Phased Array Antenna Consisting of Rectangular Waveguides of Finite Depth. Radio Phys. Radio Astron . vol. 2, no. 1, pp. 52–60 (in Russian).

Single-walled carbon nanotube networks in conductive composite materials.

Electrically conductive composite materials can be used for a wide range of applications because they combine the advantages of a specific polymeric material (e.g., thermal and mechanical properties) with the electrical properties of conductive filler particles. However, the overall electrical behaviour of these composite materials is usually much below the potential of the conductive fillers, mainly because by mixing two different components, new interfaces and interphases are created, changing the properties and behaviours of both. Our goal is to characterize and understand the nature and influence of these interfaces on the electrical properties of composite materials. We have improved a technique based on the use of sodium carboxymethyl cellulose (CMC) to disperse single-walled carbon nanotubes (SWCNTs) in water, followed by coating glass substrates, and drying and removing the CMC with a nitric acid treatment. We used electron microscopy and atomic force microscopy techniques to characterize the SWCNT films, and developed an in situ resistance measurement technique to analyse the influence of both the individual components and the mixture of an epoxy/amine system on the electrical behaviour of the SWCNTs. The results showed that impregnating a SWCNT network with a polymer is not the only factor that affects the film resistance; air exposure, temperature, physical and chemical properties of the individual polymer components, and also the formation of a polymeric network, can all have an influence on the macroscopic electrical properties of the initial SWCNT network. These results emphasize the importance of understanding the effects that each of the components can have on each other before trying to prepare an efficient polymer composite material.

Real-Time Debonding Monitoring of Composite Repaired Materials via Electrical, Acoustic, and Thermographic Methods

The electrical properties of composite materials have been thoroughly investigated recently for the detection and monitoring of damage in carbon fiber-reinforced polymers (CFRPs) under mechanical loading. Carbon nanotubes are incorporated in the polymer matrix of CFRPs for the enhancement of their electrical properties. The electrical properties have shown to be sensitive to the damage state of the material and hence their monitoring provides the profile of their structural deterioration. The aim of the paper is the cross-validation and benchmarking of an electrical potential change monitoring (EPCM) technique against acoustic emission (AE) and lock-in thermography (LT). All techniques successfully identified damage and its propagation. Thermography was more efficient in quantifying damage and describing dynamically the debond topology, as it provided full 2D imaging of the debond in real time. EPCM was successful in providing quantitative information on debond propagation and its directionality. AE provided consistent information on damage propagation. All techniques identified three stages in the fatigue life of the interrogated coupons. The representation of the fatigue behavior as a function of life fraction, the correlation of AE data with EPCM and LT data, and most importantly the consistent behavior of all tested coupons allowed for both the direct and indirect cross-correlation of all employed methodologies, which consistently identified all aforementioned fatigue life stages.

Recovery estimation for over-current test of non-inductive fault current limiters using numerical analysis

When an HTS coated conductor (CC) is used as a conductor of a superconducting fault current limiter (SFCL), the CC is expected to be exposed to the over-current and temperature of the CC is expected to be increased rapidly by electrical joule heating. Because the CC is a composite tape, thermal and electrical properties of composite materials could affects over-current limiting capacity and recovery time of SFCL. This paper presents experimental and numerical results of over-current test and recovery time measurement test on four bifilar wound SFCL modules. The temperature transitions of the samples were estimated from total electrical resistance of the coils. We fabricated one bifilar solenoid coil and three bifilar pancake coils whose cryogenic conditions were different from the other coils. An numerical model was also fabricated to simulate the temperature transition and the numerical results were compared with experimental results.

THE ELECTRICAL RESPONSE OF AN INSULATING CIRCULAR DISK TO UNIFORM FIELDS

This paper presents a closed form solution for the electrical potential perturbation of a perfectly insulating flat circular disc embedded in a homogeneous half-space in a uniform primary electric field. This has applications to the detection of insulating underground targets such as hydrocarbon reservoirs or plastic mines, as well as to the electrical properties of composite materials. The solution method is an adaptation of Weber’s method for the potential around a charged conducting disk. It yields closed form analytic solutions for the electric and magnetic fields and by straightforward numerical integration, an easily evaluated numerical solution for the electric potential and an explicit solution for the electrical resistivity of a composite material consisting of a dilute concentration of such embedded disks in an otherwise uniform conductor.