Microwave Electromagnetic Field Research Articles

Analysis of peculiarities of polymer matrix microstructure in PCMs formed under the influence of electrophysical effects

The microstructure of monolayer samples formed by 3D printing from composite prepregs reinforced with continuous carbon fiber, followed by treatment in a cured state by exposure to ultrasonic vibrations and a microwave electromagnetic field, has been studied. It has been shown that high-power ultrasonic exposure causes macro-changes, which are characterized by a decrease in the number and transverse dimensions of delaminations (cracks) from 0.05–0.1 mm to 0.01–0.02 mm and a decrease in the height of microrelief elements by almost an order of magnitude. Changes caused by exposure to a microwave electromagnetic field are more apparent when examining the end surface with an increase from ×1000 to ×10000. The control samples revealed fibers consolidated by binder in combination with unfilled gaps in a ratio of about 50:50, with individual globular fragments of frozen binder on their surface. The samples after microwave exposure revealed the presence of large areas without defects, completely uniformly filled with binder, fibers from all sides are in contact with the binder, in which there are voids no larger than 5 × 1.5μm in size. Greater orderliness of the structure of monolayers is most typical for samples with two-stage processing, including preliminary ultrasonic and subsequent.

Polymer composites with magnetically active Eu-substituted NiZn ferrite fillers

In this research, the influence of Eu substitution on structural, quasi-static as well as dynamic (electro)magnetic properties of nickel zinc ferrites has been studied. The correlation of increasing europium content in the substituted NiZn ferrite filler with constant concentration (60 vol%) and the frequency dispersion of the complex permeability in magnetically active composite samples has been explored as well. Eu-substituted nickel-zinc ferrites with chemical composition Ni0.3Zn0.7EuxFe2-xO4, where x changes from 0.00 to 0.10 (step 0.02) ions per formula unit (i./f.u.), have been selected for their high initial permeability and in general good other magnetic parameters. On contrary, non-substituted ferrite of this composition exhibits undesirably low Curie temperature inconvenient for the use of these materials even at room temperatures. Therefore, Eu has been selected as a substituent for its known ability to increase the Curie temperature of prepared ferrites. The ferrites have been synthesized by means of the conventional solid state reaction method including double sintering at the temperatures of 950 °C and 1200 °C and used as magnetically active fillers incorporated into the magnetic polymer composites. Polyvinylchloride (PVC) has been used as the polymeric matrix. In spite of substituent amount x being the only parameter changing intentionally, the behavior of both the ferrite filler (deterministic until the creation of the second, non-magnetic, phase above x = 0.04) and the ferrite/PVC composites is quite hard to explain, and validate quantitatively, on the basis of simple theoretical assumptions. Nevertheless, the experiments confirmed positive effect of europium on the increase of Curie temperature. Also, the peak frequency of the imaginary component of the complex permeability has been found to be very sensitive to x, thus offering an effective tool for tuning the high-frequency properties of the composites useable for various applications, especially the shielding of microwave electromagnetic fields.

Corrosion and heat-resistant SiCN/C as lightweight fibers for microwave absorption and electromagnetic field shielding in Ku-band

SiCN fibers are usually combined with metals to increase the magnetic loss in electromagnetic field (EMF) shielding, but this results in high weight density, easy corrosion, difficult treatment, and high cost of the material. This study proposes the manufacturing of corrosion and heat-resistant ceramic lightweight fibers containing in-situ synthesized carbon nanostructures (SiCN/C) with excellent EMF shielding in Ku-band (12.4–18 GHz). The samples showed differential trends of EMF shielding effectiveness in terms of reflectance, transmittance, and absorption behavior. Compared to SiCN fibers, the EMF absorption was two times greater when carbon was added to the SiCN matrix. A minimum reflection coefficient (S11) of −12 dB was observed for SiCN/C fibers, meaning a high shielding efficiency with >90 % of the EMF energy shielded. On the other hand, SiCN fibers showed a minimum S11 of −7 dB, resulting in a protection of 80 % against EMF energy. Computational simulations clarified the better features of SiCN/C in electromagnetic shielding compared to SiCN, which was ascribed to enhanced conduction loss derived from conductive free carbon, and dipole and interfacial polarization loss generated by defects. The fibers were resistant to acidic and basic environments and oxidation of up to 600 °C. Moreover, the addition of carbon precursor represented a weight decrease of 17 % for SiCN/C compared to SiCN fibers. This research will afford an alternative solution for the manufacturing of SiCN/C fibers with EMF absorption properties that can be used as lightweight materials in harsh environments.

Enhancement of photon–magnon coupling strength by inverted split-ring resonator at GHz

A series of inverse split-ring resonators (ISRR) loaded with an yttrium iron garnet (YIG) film were numerically and experimentally studied to provide strong photon–magnon coupling strength and cooperativity enhancement. An increase in the photon–magnon coupling strength and cooperativity has been achieved due to the simultaneous increase in the spatial overlapping between the ISRR microwave electromagnetic field magnetic component and the uniform magnon mode in the YIG, and the appearance of spatial areas with higher ISRR electromagnetic field magnetic component strength. Practically, this was reached for the ISRR by increasing the conducting gap length and changing the conducting gap shape by protrusions forming. Higher values of spin-number-normalized photon–magnon coupling strength gN and cooperativity C were reached in all cases for the ISRR with protrusion (compared with ISSR with identical conducting gap length but without protrusion). All resonators presented in this paper seem to be more prospective for the realization in quantum hybrid systems than conventional split-ring resonators and ISRR.

Theory design and dynamic testing of Magnetic Tunnel Junction (MTJ) spin microwave detection chip

The magnetic tunnel junction (MTJ) chip has recently been verified in numerous studies as a microwave detection or microwave radiation unit. In this paper, a theoretical model for a coplanar chip incorporating an MTJ for microwave detection is established, and it is shown how the electromagnetic characteristics of the MTJ varied with the frequency, amplitude, and phase of the microwave electromagnetic field in simulations and experiments. Based on several studies of our research, meaningful conclusions are provided to direct the processing and dynamic detection of microwave electromagnetic fields in MTJ chips. Initially, the micrometer-sized MTJ chip was fabricated by using a lithography process directly on the signal line of coplanar waveguide. It was found that the detection chip voltage (μV level) increased linearly with microwave power from 3 dBm to 20 dBm. The frequency of the microwave field and the static magnetic field along the easy axis cause the probe voltage of the chip to change in a wave-peak–valley curve, and the amplitude of the probe signal slightly increases with frequency. Additionally, theoretical and experimental results indicate that this is a combined result of spin magneto-resistance and ferromagnetic resonance absorption. In the experiments, two microwave beams were applied in opposite, and the resulting detection voltage clearly represented an interference effect. The test signal’s phase also changed according to a trigonometric function, with a maximum value varying between a few and several hundreds of μV. The aforementioned findings demonstrate that MTJs can theoretically and practically be utilized as spectrometers to detect microwave electromagnetic fields.

Microwave heat-induced aggregation behavior of fish myofibrillar protein: New insights from nano- and micro-structural observation

The interaction between electromagnetic microwave field and biomacromolecule is not commonly understood, and the existence of the ‘microwave effects’ has been controversial. Herein, the aggregation behavior of fish myofibrillar proteins (MPs) induced by microwave heating (MW) and water bath heating (WB) was studied by using a range of electron microscopy techniques, including scanning electron microscope, cryo-SEM, atomic force microscopy, transmission electron microscope, and cryo-electron microscope. Through these methods, we hope to explore this issue from a multi-scale and dimensional perspective. In this communication, the unusual aggregation behavior of salt-soluble MPs under microwave irradiation was reported for the first time by controlling the same time–temperature heating curve with WB, yielding a dispersive and irregular structure with smaller particle size, subsequently generated a more stable, denser, and well-structured network. However, regional agglomeration behavior is more remarkable in WB treatment, which can lead to structural instability. These findings explained why microwaves can obtain protein gel with superior gel strength than WB from the structural perspective.

Loss and revival of coherence in the interaction between a positron beam and a photon field

We study the interaction between a positron beam in the single-particle regime in an interferometric configuration and a microwave electromagnetic field. We discuss the conditions under which quantum interference can be affected by the field and we outline its possible experimental study in the framework of QUantum interferometry and gravitation with Positrons and LASers (QUPLAS) experiment.

Влияние температуры СВЧ нагрева отвержденного конструкционного эпоксиуглепластика на напряжения межслоевого сдвига

Studies of changes in the limiting stresses of interlayer shear during loading of cured carbon-filled plastic after exposure to a microwave electromagnetic field with a frequency of 2450 MHz and with different energy flux densities, taking into account the thermal factor and time, have been performed. It is shown that with a rational combination of energy flux density and time, (17—18) · 104 mcW / cm2 and 2 min, respectively, the values of the limiting voltages increase by an average of 17% as compared with the reference specimens.

Effect of interface bonding and properties of graphite/copper composites by microwave pressure sintering

The graphite/copper composites were prepared by different sintering processes. The effects of conventional sintering, microwave sintering, and microwave pressure sintering on the structure and properties of the composites was investigated. The results demonstrate that the microwave electromagnetic field can promote interfacial bonding of graphite and copper matrices, and pressure sintering may further promote interfacial bonding of the copper matrix and grain refinement, thereby improving the overall application performance of the composites. At a sintering temperature of 950 ℃, a holding time of 1 h, and a graphite volume fraction of 50 vol%, the physical and mechanical properties of the composites prepared by microwave pressure sintering were optimal when the pressure was 350 kPa. The internal thermal conductivity of the cross plane was 681.0 (W·m−1·K−1), the tensile strength was 32.57 MPa, and the elongation at break was 18.46%. It is proved that microwave pressure sintering is beneficial to improve the comprehensive properties of composites, and provides a new research idea for the preparation of graphite/copper composites with high thermal conductivity.

The Effect of a Microwave Electromagnetic Field on the Temperature Distribution in Composite Materials

The Effect of a Microwave Electromagnetic Field on the Temperature Distribution in Composite Materials

Research on liquid-phase catalytic thermolysis of high-viscosity oil samples being stimulated by microwave radiation in dynamic mode (in the order of discussion)

A significant part of Azerbaijan’s oil reserves are fields of high high-viscosity oil, being at younger stage of development, in conditions of low permeable reservoirs. Technogenic complications arising from the exploitation of such fields, create new requirements for oil production technologies, capable to increase the oil recovery of the already existing layers. This paper presents the results of a study of liquid-phase catalytic thermolysis stimulated by microwave radiation of samples of high-viscosity oil from the Balakhani-Sabunchu-Ramany (VI and XI horizons) and Kyurovdag fields, characterized by averaged values of density, respectively, 885 kg/m3, 908 kg/m3 and 923 kg/m3 at 20 oC. In dynamic mode in the presence of synthesized heterogeneous catalysts that intensively absorb the energy of the microwave electromagnetic field.

Effects of microwave on the structural and emulsifying properties and interfacial properties of oxidized soybean protein aggregates.

This research explored microwave treatment impact on the structuro-functional aspects of oxidized soy protein aggregates (OSPI). Data showed that oxidative treatment promoted the formation of high molecular weight aggregates through hydrophobic interactions, thereby disrupting the structure of natural soy protein isolates (SPI). Microwave treatment for an appropriate time (≤30s) caused the molecular structure of OSPI to open up and reduction in molecular weight and disulfide bond content, while absolute zeta potential increased. These modifications increased emulsifying capacity of OSPI, as well as the interfacial adsorption of protein. Longer microwave treatment times (>30s) caused OSPI to exhibit a tendency to aggregate in TEM and CLSM images. It indicated the appropriate microwave electromagnetic field effect and microwave heating effect could coordinatively regulate soy protein functional properties by modifying their aggregation behavior. The results provided new ideas for reducing resource waste, and further expanding soy protein application in the food industry.

Evaluation of the efficiency of microwave heating of soils

One of the innovative directions of heat treatment of soil in the technologies of decontamination from pesticides, oil products and disinfection is heating in a microwave electromagnetic field. Numerical studies testify to the effectiveness of the microwave treatment method. This is due to the peculiarities of the interaction of the microwave field with dielectric materials. Unique effects arise, such as the possibility of local heating, volume heating of the material, unidirectionality of pressure and humidity gradients. This contributes to the intensification of transfer processes and the possibility of energy savings. However, the challenge at present is to determine the processing regimes, including load mass, specific microwave field power, electric field strength, material layer thickness, and processing time, under which the microwave method will be energy efficient. Conducting multifactorial experimental studies allows determining the conditions of energy feasibility of microwave soil treatment. Therefore, the object of research is the process of heating a dense layer of soil under the action of a microwave electromagnetic field. The results of studies on the effect of microwave treatment of soil contaminated with organophosphorus pesticides, contaminated with petroleum products, and under what conditions the qualitative effect was obtained, as well as the results of the effect of the microwave field on the pathogenic microflora of the soil used for growing plants, were considered. The high quality of implementation of soil treatment technologies is determined. Energy efficiency was determined on the basis of data on temperature and moisture content, analysis of thermograms of microwave heating of chernozem and clay soil, analysis of the influence of material layer thickness, influence of dielectric properties and power of the microwave field. According to the results of thermal calculations, the values of the efficiency of the microwave chamber and the intensity of the electric field were determined, which are recommended as the basis for scaling in order to transfer the experimental results to industrial installations. During the research, specific experimental methods of research under microwave heating conditions, analytical methods of thermal calculations, developed by the authors of the experimental research methodology were used. Experimental studies were carried out on the installation created by the authors. The results of the research are intended for the wide implementation into practice of technological calculations of microwave chambers for heat treatment of soils, intensification of disinfection processes under the conditions of energy efficiency of the transformation of the energy of the microwave field into the internal energy of the soil.

Совместное использование ультразвуковой обработки и электрического поля СВЧ при дефростации мясного сырья

Purpose. Combined use of ultrasonic and microwave treatment potential evaluation in the meat raw materials defrosting in terms of efficiency and impact on functional and technological properties. Materials and Methods. Defrosting and evaluation of organoleptic and functional-technological properties of meat raw materials samples were performed in conditions of the complex analytical laboratory of Volga Region Research Institute of Manufacture and Processing of Meat-And-Milk Production. Analyses of qualitative characteristics were carried out in accordance with generally accepted methods in the food industry and actual national standards. The objects of the study were frozen samples of lean pork, сhicken breast meat, pork heart, beef liver. Results. In the research, a defrosting meat raw materials method, based on successive processing with microwave fields and ultrasonic vibrations in a solution of sodium chloride was studied. To obtain relevant results, other methods of defrosting frozen meat raw materials used in the food industry were also analyzed. It was found that the combined effect of the microwave electromagnetic field and ultrasonic treatment in an aqueous medium on meat raw materials in all the studied cases has a synergistic effect, thereby increasing the rate of defrosting. In comparison with the immersion method in meat raw materials located in the ultrasound field, moisture accumulation is slower. Supposedly, this occurs due to the hydration processes inhibition on the meat raw materials surface under the effect of ultrasonic cavitation in a liquid. Conclusion. The proposed method of defrosting can be considered promising in terms of reducing weight loss of meat raw materials. At the same time, ultrasonic treatment prevents the accumulation of excess moisture. Soaking in a solution of sodium chloride makes it possible to increase heat transfer and thereby avoid local overheating of the surface, and even increase the power of the microwave electromagnetic field. At the same time, this type of processing leads to a insignificant increase in hardness and darkening of the surface, which limits the raw materials possibilities use.

Using Modeling to Select the Type of Microwave Field Emitter for Dense-Layer Grain Dryers

The microwave field is used for drying and disinfecting grains during the pre-sowing seed treatment. The use of a microwave field in these installations leads to an increase in their productivity and a decrease in the energy consumed by them. In grain dryers, where the grain moves in a dense layer without being loosened, one of the challenges in using microwave fields is ensuring sufficient uniformity of the field distribution. In this article, waveguide design options that introduce microwave radiation into the grain layer are discussed. The objective of this study was to use application software to find the optimum type of transmitter from the three options presented. A mathematical simulation of the electromagnetic field distribution was performed with the use of CST Microwave Studio software 2019 in order to evaluate and compare horn-type, rectangular, and semicircular waveguides. The data on the standing wave ratio and radiation efficiency of these types of waveguides have been reported. The specific features of the microwave electromagnetic field distribution and radiation power in the output of these waveguides have been described. The results of mathematical simulations revealed that semicircular waveguides with slot-type radiators are preferable for processing dense grain layers.

Numerical simulation of the coupled multiphysics fields and reactions during the microwave pyrolysis of wood particles

Microwave heating has gained significant attention as an alternative to conventional methods for biomass pyrolysis. To investigate the electromagnetic-thermal-hydraulic-chemical processes during biomass pyrolysis under microwave irradiation, a three-dimensional comprehensive pyrolysis model was developed. The model numerically described the physicochemical processes of the electromagnetic wave propagation in the reactor, heat transfer and fluid flow inside porous wood particles, pyrolysis reactions, and phase changes. The model was validated by comparing the temperature profiles of biomass samples under varying microwave powers against literature data. The modeling results demonstrated that there was a strong interaction between the distributions of the microwave electromagnetic fields in the cavity and that inside the wood particles; these distributions changed with the size, shape, and location of the biomass sample in the cavity. Using the model, the thermal response of wood particles to microwave radiation was determined. The predicted results showed that a millimeter-sized wood particle was large enough to straddle multiple high-energy microwave regions in the cavity, resulting in more than one intraparticle hotspots. The transient dielectric loss inside wood particles is nonuniform due to the enhancement of the local relative permittivity by the local hotspots. The maximum permeability within the wood particles increases by an order of magnitude during microwave pyrolysis at 1 kW. The hotspots have a considerable influence on the structural homogeneity and stability of biochar due to the formation of large thermal and expansion stresses around the hotspot locations. Moreover, the energy efficiency (ηe) of converting microwave electromagnetic energy into the thermal energy of wood particles is sensitive to the input microwave power and particle shape. For instance, ηe ranges from 12.44% to 36.15% under the microwave powers of 0.8–1 kW for the pyrolysis of a cylindrical wood particle with aspect ratios of 0.25–2. This work provides the fundamental technical support for the industrial application of microwave pyrolysis.

Effect of blueberry (<i>vaccínium myrtíllus</i>) leaves extract, obtained by microwave heating on the dynamics of animal fat oxidation processes

The potential of antioxidant properties of blueberry leaves extract (vaccínium myrtíllus) that grows in the Trans-Baikal region has been studied in this work. In order to increase the efficiency of extraction of biologically active substances with antioxidant properties, this extract was obtained with the help of microwave field. The optimal parameters for the extraction of active substances from the blueberry leaves with the help of electromagnetic microwave field have been defined. The influence of the power of the electromagnetic field and the duration of the process of blueberry leaves extraction on the efficiency of extraction of biologically active polyphenolic substances has been studied. The following parameters of the technology for blueberry leaves extraction were obtained: extraction with a water-alcohol solution with a concentration of 40% in the ratio of raw materials to extractant as 1 to 5, with duration of stirring as long as 30 minutes, then the application of an electromagnetic field of microwave heating with a power of 850W for 8–10 minutes long. Blueberry leaves extract is a clear liquid with a high content of polyphenols, of rich brown color, tart taste, without bitterness. The antioxidant potential of the obtained extract has been studied. To do this, the extract has been added into the finely ground animal fat and left for storage in a closed dark container. During storage, the dynamics of the peroxide number has been measured, as this value characterizes the degree of lipid oxidation. It has been found that blueberry leaves extract inhibits the process of animal fat oxidation due to the action of biologically active substances that feature antioxidant properties.

Computational modeling of CO2 conversion by a solar-enhanced microwave plasma reactor

The use of renewable energy to convert carbon dioxide (CO2) into higher-value products can help meet the demand for fuels and chemicals while reducing CO2 emissions. Solar-Enhanced Microwave Plasma (SEMP) CO2 conversion aims to combine the scalability and sustainability of solar thermochemical methods with the high efficiency and continuous operation of plasmachemical approaches. A computational study of a built SEMP reactor operating with up to 1250 W of microwave power together with up to 525 W of incident solar power at atmospheric pressure is presented. The study is based on a fully-coupled 2D computational model comprising the description of fluid flow, heat transfer, Ar-CO2 chemical kinetics, energy conservation for electrons and heavy-species, electrostatics, and radiative transport in participating media through the discharge tube, together with the description of the microwave electromagnetic field through the waveguide and the discharge tube. Numerical simulations reveal that the plasma is concentrated near the location of incident microwave energy, which is aligned with the radiation focal point, and that CO2 decomposition is highest in that region. The incident solar radiation flux leads to more uniform distributions of heavy-species temperature with moderately greater values throughout most of the discharge tube. Modeling results show that, at 700 W of electric power, conversion efficiency increases from 6.8% to 10.0% with increasing solar power from 0 to 525 W, in good agreement with the experimental findings of 6.4% to 9.2%. The enhanced process performance is a consequence of the greater power density of the microwave plasma due to the absorption of solar radiation.

Microwave Modification of an Epoxy Basalt-Filled Oligomer to Improve the Functional Properties of a Composite Based on It.

The purpose of this work is to study the influence of the electric field strength of an electromagnetic wave with the maximum modifying effect on an epoxy basalt-filled oligomer, which is of great scientific and practical importance for the development of microwave oligomer modification technology. The optimal modes of microwave modification, under which the highest values of the mechanical properties of an epoxy basalt-filled polymer composite material are obtained, are identified: power of 400 W and an exposure time of 24 s. At the same time, the breaking stress in bending increases by 20%, the impact strength increases by 2 times, and hardness increases by 31%. A slight increase of 4.5% in heat resistance is noted compared to the composite obtained on the basis of an oligomer unmodified in the microwave electromagnetic field. The results of resistance to various aggressive environments are obtained, which show that the studied physical and mechanical characteristics of the epoxy basalt-filled material after exposure to an aggressive environment decrease by less than 14%, which corresponds to their good resistance to an aggressive environment. It is established that the effect of the microwave electromagnetic field on an epoxy basalt-filled oligomer is an effective modification method that improves physical and mechanical characteristics with a high level of temporal stability to climatic influences, with a coefficient of property retention of more than 90%.

Investigation of Microwave Electromagnetic Fields in Open and Shielded Areas and Their Possible Effects on Biological Structure.

The article's subject is the investigation of electromagnetic fields (EMF) of the microwave frequency band in a typical human living environment, especially in shielded areas. The point of view of electromagnetic field presence in the environment with the rapid increase in the level of the electromagnetic background is currently an essential point concerning population protection against the potential adverse effects of such EMFs. The authors focus on actual measurements, especially in shielded spaces frequently used in everyday life, such as elevator cabins and cars. The goal is a quantitative evaluation of the distribution of specific vector quantities of the EM field and a comparison with the currently valid hygiene standards. Measured values in shielded spaces show elevated levels in contrast to the open space. However, the values do not exceed limits set by considering the thermal effect on living tissues.