Use Of Microwave Energy Research Articles

Microwave radiation of space and prospects for its use in quantum propulsors

Using the original approach developed in recent years – supramolecular physics of the environment, the results of considering the contribution of physical optics processes to the formation of induced microwave radiation are presented.The two most powerful cosmic thermal sources: the background (relict) flux in the absolute millimeter maximum of the spectrum, and the mm-wave radio flux from Sun are considered. The postulate of A. Einstein about the emergence of an induced emission quantum in a medium with established thermal equilibrium is taken into account. This made it possible to quantitatively substantiate, based on the principles of the similarity theory of G.S. Golitsyn, a scheme for the use of microwave energy of the interstellar/interplanetary medium during space flights. Based on the physics of collisions, in the proton transfer reaction of the main simple hydrides in interstellar/interplanetary molecular clouds, it is proposed to take into account the possibility of the manifestation of an additional channel for the maser effect in such a medium (first considered by V.A. Ambartsumian in 1979) due to the close location of electronically excited Rydberg levels for molecules in these clouds. The pioneering work of N.S. Kardashev on the study of Rydberg transitions during the emission of recombination radio lines was taken into account. Due to the efforts of astronomers from the Lebedev Physical Institute and the State Astronomical Observatory of the Russian Academy of Sciences (at Pulkovo), this work led to the discovery of the microwave flux from deep space objects. Real energy and schemes for using a microwave quantum propulsor device with the ability to choose the direction of flights are discussed.

Analysis of Microwave-Induced Damage in Granite Aggregates Influenced by Mineral Texture

The use of microwave energy to recycle high-quality coarse aggregates from waste concrete or assist hard rock breakage in underground building engineering is promising. Controlling or promoting the damage of coarse aggregates, i.e., hard rocks, under microwave irradiation is a crucial issue faced by these techniques. Understanding the damage mechanisms of hard rocks exposed to microwaves is thus urgent. Fracture toughness is a significant mechanical parameter of rocks that reflects their ability to resist crack propagation and damage evolution. In this study, the fracture toughness degradation of microwave-heated granite was investigated by combining experimental investigations and numerical simulations. A three-point-bending (TPB) experiment was conducted on granite specimens after microwave irradiation. A coupled electromagnetic–thermal–mechanical model considering the actual mineral texture of the granite specimen was established. The evolution of the temperature gradient and stress field near the initial notch tip were investigated. The results suggest that the microwave-induced maximum temperature gradient and stress in granite are at the plagioclase–quartz (Pl–Qtz) interfaces or inside the Pl near the boundary. The region of cracking initiation was defined as the damage zone, which could be obtained by comparing the microwave-induced thermal stress with the critical value. The fracture toughness degradation, which corresponds to the evolution of the damage zones, can be divided into two stages. A relatively rapid decrease in fracture toughness in the first stage is primarily caused by the spread of the scattered damage zones along the Pl–Qtz interfaces; subsequently, a gentler fracture toughness degradation results mainly from the extension of the previous damage zones.

Thermocoagulation of resection surfaces of parenchymal organs using a new source of ultrahigh frequency energy (experimental study)

Relevance. Modern surgery is characterized by the use of various technical means to perform classical surgical techniques - separation and connection of tissues, hemostasis. The study of the applicability of new surgical devices and the search for technological techniques are an important task.The aim of the study: to evaluate the capabilities of the developed device based on microwave energy for hemostatic coagula­tion of resection surfaces of parenchymal organs.Materials and methods. The method is based on the principle of converting microwave energy into heat when it is absorbed in biological tissue. The choice of the microwave range is due to the higher efficiency of power supply to the heat­ing area. Based on the prototype of a medical microwave complex developed in 2011 for thermal effects on biological tissues (RF Patent 2481080. 2011), a prototype of a microwave coagulator for working with parenchymal organs was created. The device was tested on the paren­chymal organs of large laboratory animals under conditions of preserved and switched off blood flow in various energy supply modes. Tissue samples from coagulated lesions were studied histologically.Results. At the site of exposure of the applicator-coagulator to the parenchymal organ, a zone of coagulation changes appears. A clear dependence of the size of coagulation necrosis on the time and power of exposure was noted. When the blood flow is turned off, the necessary stable hemostasis is achieved by shorter exposure time of the coagulator antenna on the surface of the organ.Conclusions. The most effective and reliable hemostasis is achieved on the liver parenchyma. The use of temporary vascular isolation, especially on the kidneys and spleen, involves a single use of microwave energy to stop bleeding. By changing the power and duration of exposure, it is possible to dose the thermal load on biological tissue with great precision. This adjustment allows you to select the operating mode for each specific case. The obtained results of the experiment of the described system during surgery for the purpose of hemostasis in parenchymal bleeding.

Multiphysics simulations of uniaxial compression applied to various rock samples subject to microwave pretreatment

PurposeAmong the various applications involving the use of microwave energy, its growing utility within the mining industry is particularly noteworthy. Conventional grinding processes are often overburdened by energy inefficiencies that are directly related to machine wear, pollution and rising project costs. In this work, we numerically investigate the effects of microwave pretreatment through a series of compression tests as a means to help mitigate these energy inefficiencies.Design/methodology/approachWe investigate the effects of microwave pretreatment on various rock samples, as quantified by uniaxial compression tests. In particular, we assign sample heterogeneity based on a Gaussian statistical distribution and invoke a damage model for elemental tensile and compressive stresses based on the maximum tensile stress and the Mohr–Coulomb theories, respectively. We further couple the electromagnetic, thermal and solid displacement relations using finite element modeling.Findings(1) Increased power intensity during microwave pretreatment results in decreased axial compressive stress. (2) Leveraging statistics to induce variable compressive and tensile strength can greatly facilitate sample heterogeneity and prove necessary for damage modeling. (3) There exists a nonlinear trend to the reduction in smax with increasing power levels, implying an optimum energy output efficiency to create the maximum degradation-power cost relationship.Originality/valuePrevious research in this area has been largely limited to two-dimensional thermo-electric models. The onset of high-performance computing has allowed for the development of high-fidelity, three-dimensional models with coupled equations for electromagnetics, heat transfer and solid mechanics.

Monosaccharide composition of lignocellulosic matrix—Optimization of microwave-assisted acid hydrolysis condition

Compositional analysis of polysaccharides is crucial in many applications of analytical chemistry, and typically involves hydrolysis as initial step, to break glycosidic bonds and release individual monosaccharide units. We developed a new method for the microwave-assisted acid hydrolysis of polysaccharides, here applied for determining the composition of the polysaccharide fraction within the lignocellulosic matrix of Pinus sylvestris. The optimisation of reaction conditions was carried out using a GC–MS method after a double-step sugar derivatization process.Under the optimized conditions, specifically, employing 2 M TFA, 40 min, and 120 °C, a high depolymerisation yield was achieved with minimal degradation. Furthermore, the amount of polysaccharides detected in pine wood aligns with the results in existing literature, substantiating the determined chemical composition.The synergy of microwave-assisted acid hydrolysis and full factorial design not only facilitated the determination of the optimal hydrolysis conditions but also enabled the assessment of the parameters influencing the polysaccharide hydrolysis process and their relationships. This approach made it feasible to achieve maximum hydrolysis efficiency while minimizing analyte degradation, employing a method that reduces environmental impact through the use of microwave energy. This strategy effectively reduced the required reaction temperature, time, and reagent quantities.

Analysis of the influence of the type of heat transfer on the dynamics of the ignition processes of wood biomass particles under complex heating conditions

The article presents the results of theoretical and experimental studies of the processes of wood particles ignition under heating conditions typical for furnace devices operating using the circulating fluidized bed technology. The characteristics and conditions of ignition processes under radiation, radiation-convective and radiation-convective-microwave heating are compared. According to the results of the experiments, it was found that the use of microwave energy to accelerate the ignition of wood biomass particles is most effective at moderate temperatures of the combustion medium (at Tg≤870 K). Such conditions, as a rule, are formed in furnace devices that operate using boiling and circulating layer technologies. Based on the results of the analysis of the regularities established in the experiments, a mathematical model of the processes of ignition of a particle of wood biomass under conditions of complex radiation-convective-microwave heating has been developed. Using the method of quasi-stationary "thermal" approximation developed by the authors, an approximate analytical solution of the essentially nonlinear problem of ignition of wood biomass particles under conditions of complex heating is obtained. A comparative analysis of the theoretical and experimental values of the ignition delay time showed their good agreement. The results of the performed studies illustrate the possibility of a sufficiently significant reduction in the ignition delay times of wood biomass particles when using microwave radiation in addition to "conventional" sources of heating fuel particles in the furnace space in the temperature range at which the minimum concentration of anthropogenic nitrogen oxides in fuel combustion products is ensured.

СВЧ-УСТАНОВКИ С КАМЕРАМИ ГИБРИДНОГО ТИПА ДЛЯ ОБРАБОТКИ СЕЛЬСКОХОЗЯЙСТВЕННЫХ КУЛЬТУР, ДИЭЛЕКТРИЧЕСКИХ И ПОЛИМЕРНЫХ МАТЕРИАЛОВ

A classification of areas of agriculture in which the energy of microwave electromagnetic oscillations is used for processing materials is proposed. The possibility of forming a new field based on the use of microwave installations on hybrid-type working chambers has been shown, which will allow an agricultural producer to enter the commodity market not only with agricultural products, but also with polymer materials with new properties obtained through non-thermal microwave modification in the technological block of Microwave installations. A comparison has been made of studies on the use of microwave energy in technological processes in a market economy. The practical significance of the given analysis of the use of microwave energy in agriculture is indicated.

The use of high frequency microwaves in absolute palaeomagnetic intensity experiments

The Microwave Palaeointensity System at the University of Liverpool has developed, over 30 years, into the current third generation version; a combined 14 GHz microwave resonant cavity and superconducting quantum interference device magnetometer integrated microwave system. The use of microwave energy minimises the bulk temperatures required to demagnetise and remagnetise palaeomagnetic material, thereby limiting the significant problem of thermo-chemical alteration of magnetic minerals. Here we review the microwave palaeointensity approach, including its development, technical details, modern usage and results. We have carried out a comprehensive analysis of 20 palaeointensity studies, published between 2008 and 2022, where data collected using the microwave system may be compared with various other methods at the site level. An assessment of microwave results revealed no statistical bias compared to thermal, and known field data. We also present results from a new controlled experiment which tests the ability of the microwave to accurately recover weak, ancient palaeointensities when strongly overprinted. We conclude that the microwave system can be used for the primary method of determining accurate absolute palaeointensities or as part of a multi-method approach, and is well suited to a wide range of material from archaeomagnetic samples to ancient rocks.

СОЧЕТАНИЕ МИКРОВОЛНОВОЙ ТЕХНОЛОГИИ С ЗОЛЬ-ГЕЛЬ МЕТОДОМ С АВТОГОРЕНИЕМ ДЛЯ ПОЛУЧЕНИЯ КАТАЛИЗАТОРОВ НИЗКОТЕМПЕРАТУРНОГО ОКИСЛЕНИЯ МОНООКСИДА УГЛЕРОДА

The results of a study of the reaction of carbon monoxide oxidation on double and triple cobalt-containing oxide catalysts obtained by the sol-gel method with auto-combustion and the use of microwave technology are presented. The conditions for combining microwave treatment with the sol-gel method with auto-combustion are established. The use of microwave energy to "ignite" the gel without further prolonged irradiation, the catalytic activity of the obtained oxide systems in the oxidative conversion of carbon monoxide is comparable to the activity of similar samples obtained by the sol-gel method with traditional combustion

Microwave heating of biomass waste residues for sustainable bioenergy and biomass materials preparation: A parametric simulation study

Sustainable bioenergy and biomass materials preparation from biomass waste residues using microwave heating has attracted widespread attention. However, the microwave heating process still has limitations of uneven temperature distribution and low energy conversion efficiency. This study constructed a coupled electromagnetic and heat transfer model for the microwave heating of waste tobacco stem (TS) biomass using COMSOL Multiphysics® software. The microwave heating behavior of TS biomass was predicted using the finite element method for different parameters, and this model has been experimentally verified to be dependable with a maximum relative error of less than 10%. Simulation results show that hot spots caused by interface polarization and standing waves generate inhomogeneous temperature distributions. The microwave cavity design with two waveguides and controlled frequency changes can improve microwave energy absorption and heating uniformity. A suitable microwave power can improve efficiency and reduce energy consumption during heating. Meanwhile, the TS biomass with 30% moisture content and in the cavity's low region (0–10 cm) can make maximum use of microwave energy, and the average and maximum energy efficiency achieve 59.15% and 87.79%, respectively. The results provide technical support and new perspectives for preparing sustainable bioenergy and biomass materials from waste TS biomass via microwave irradiation.

Effect of processing conditions (conventional heating, microwave, chilling, and freezing) on the stability of some bioactive compounds of jujube fruit

The common processing techniques may cause losses in nutritional quality and phytochemical content of processed fruits. In the present research, the jujube fruit was processed by various methods including conventional heating (at 80 and 95 °C), microwave (600 W for 1 min), chilling (at 1 and 2 months), and freezing (at -18 °C for 1 year). Then, the effects of various common processing conditions were investigated separately on some bioactive compounds (e.g., total phenolic content, total monomeric anthocyanin content, individual anthocyanins, and individual organic acids) of jujube fruit. The microwave method in comparison with the conventional heating caused a slight significant (P < 0.05) decrease in the total monomeric anthocyanin and the total phenolic content (about 5.7% and 3.1%, respectively). The cyanidin-3,5-diglucoside was determined as the major anthocyanin in jujube fruit, while its degradation was more pronounced in the conventional heating at 80 °C (24.2%) compared to the microwave (2.7%), chilling for 2 months (20.1%), and freezing processes (8.4%). In general, malic, citric, succinic, and ascorbic acids were the most predominant organic acid in the jujube fruit. The ascorbic acid was one of the most sensitive organic acids of jujube fruit to processing methods. According to the results, the use of microwave energy and freezing treatment could be effective for the preservation of the natural organoleptic characteristics and bioactive compounds of jujube fruit.

Silica-Fiber-Reinforced Composites for Microelectronic Applications: Effects of Curing Routes

For curing of fiber-reinforced epoxy composites, an alternative to thermal heating is the use of microwave energy, which cures quickly and consumes less energy. Employing thermal curing (TC) and microwave (MC) curing methods, we present a comparative study on the functional characteristics of fiber-reinforced composite for microelectronics. The composite prepregs, prepared from commercial silica fiber fabric/epoxy resin, were separately cured via thermal and microwave energy under curing conditions (temperature/time). The dielectric, structural, morphological, thermal, and mechanical properties of composite materials were investigated. Microwave cured composite showed a 1% lower dielectric constant, 21.5% lower dielectric loss factor, and 2.6% lower weight loss, than thermally cured one. Furthermore, the dynamic mechanical analysis (DMA) revealed a 20% increase in the storage and loss modulus along with a 15.5% increase in the glass transition temperature (Tg) of microwave-cured compared to thermally cured composite. The fourier transformation infrared spectroscopy (FTIR) showed similar spectra of both the composites; however, the microwave-cured composite exhibited higher tensile (15.4%), and compression strength (4.3%) than the thermally cured composite. These results illustrate that microwave-cured silica-fiber-reinforced composite exhibit superior electrical performance, thermal stability, and mechanical properties compared to thermally cured silica fiber/epoxy composite in a shorter time and the expense of less energy.

Microwave assisted green synthesis of carbon dots from sweet flag (Acorus calamus) for fluorescent sensing of 4-nitrophenol

In this piece of work, a simple and cost-effective fluorescence sensor for the detection of 4-nitrophenol (4-NP) was developed from natural resource, sweet flag (Acorus calamus) through greener route by the use of microwave energy. 4-NP is identified as a potential water pollutant by EPA which can exert several hazardous effect in humans and other aquatic organisms and hence lower level detection of 4-NP is highly demanding. The as obtained carbon dots with excitation dependent fluorescence behaviour, designated as SFCDs, produced a noticeable quenching in fluorescence on interacting with 4-NP. Therefore, a simple and time-saving fluorescence sensing for the detection of 4-NP was developed. The observed turn-off in fluorescence of SFCDs with 4-NP was investigated through different experiments and finally accredited to a combination of both static quenching and inner filter effect (IFE). The proposed probe selectively detect the 4-NP with LOD of 0.207 µM and linear range of 0–14.28 µM, the detection limit was found to be lower than allowed concentration of this pollutant in drinking water. Furthermore, the same method has been practically applied for detecting 4-NP in natural water resources with good level of recovery percentages. As a whole, the developed method gives value addition to the sweet flag for the first time by its direct materialization through a completely greener route without using any hazardous chemicals. The good level of precision and accuracy with detection limits in micromolar range are promising to use the system as a fluoroprobe for detecting 4-NP, a primary pollutant found in natural water resources.

Increasing of bakelite binder strength due to use of microwave energy in heat treatment of semi-finished abrasive tools

The results of a study of the influence of the type of heat treatment on the strength and structural characteristics of an abrasive tool on a bakelite bundle are presented. The prospects of using microwave energy in the production of polymer composites are noted. In particular, the use of microwave heat treatment makes it possible to reduce the duration of the technological cycle, specific energy consumption and increase the strength of the finished product.

The effect of microwave energy on sintering of an austenitic stainless steel reinforced with boron carbide

Microwave heating has emerged as an alternative to traditional sintering methods because it consumes less energy and requires shorter processing times. The use of microwave energy in the processing of austenitic stainless steel AISI 316L reinforced with dispersed boron carbide particles was investigated in this study. Different processing parameters were used to investigate the effect of sintering time and temperature, as well as the weight percentage of the ceramic added to the steel matrix, on the final material properties. The compressibility curve, elastic relaxation, and geometric density of green compacts were used to investigate their physical properties. The Archimedes method was used to determine density, and the statistical treatment of analysis of variance was used to determine porosity. Images obtained using optical microscopy and scanning electron microscopy revealed the formation of a second phase in different volumes. The results showed that 1100 °C and a 15-minute plateau were sufficient to sinter the material. AISI 316L samples containing 3 wt.% boron carbide demonstrated greater volumetric formation of secondary phases, resulting in a significant increase in the hardness of the austenitic composite developed.

Investigation of Dyeing Properties of Mohair Fiber Dyed with Natural Dyes Obtained from Candelariella reflexa

ABSTRACT The current study reports on using ascorbic acid as a possible substitute for improving fastness properties of natural dyes. In the mordanting process, microwave energy, which is a part of the sustainable and ecological production approach, was used. Renewable natural dye source Candelariella reflexa, which is a genus of lichen, was obtained from the trunk of Pinus nigra. Mohair fiber was dyed with natural dye extracted from Candelariella reflexa by using a conventional method. Before dyeing, mohair fiber was subjected to the premordanted process with iron (III) chloride (FeCl3) using microwave energy. In order to determine the effect of mordanting process parameters on dyeing properties, the mordanting process was performed with different concentrations and durations. In the dyeing process, ascorbic acid was added at different concentrations in the dyeing bath to improve the light fastness of samples. After the dyeing process, spectrophotometric features, light, and rubbing and washing fastness of samples were investigated. The color strength, washing, light, and rubbing fastness of dyed mohair fiber improve slightly with the premordanting process and by adding ascorbic acid. The spectrophotometric measurement results show that color coordinates vary from the mordanting time and amount of ascorbic acid. Furthermore, the use of microwave energy in the mordanting process leads to saving of energy and time. Besides, in this study, a machine learning-based model exploiting the artificial neural network (ANN) was developed for prediction of dyeing properties of mohair fiber dyed with natural dyes obtained from Candelariella reflexa. Experimental data obtained through various tests were first used to feed the proposed ANN, and then the trained ANN was validated and tested for the aim of prediction. The study results show that the proposed model can successfully predict most of the dyeing properties of mohair fiber. Therefore, this model can be used as an effective tool to estimate dyeing characteristics of mohair fiber.

Evaluation of the Use of Microwave Energy on The Reduction of Iron Ore and Steelmaking Mill Scale Composite Self-Reducing Mixtures

With the growing industrialization, there is a constant increase in the world demand for steel, causing an increase on extraction of low-grade iron ores, which bear high levels of impurities. A feasible alternative is the use of residues from steel rolling processes (steelmaking mill scale) generated in the steel industry, which are composed of iron oxides consisting mainly of wustite (FeO), hematite (Fe2O3) and magnetite (Fe3O4). In line with the recycling of wastes, the application of heating by microwave energy in ironmaking processes consists in a promising new method developed in recent decades and is considered a cleaner technique. Therefore, this study aims to evaluate the self-reduction of mixtures composed of iron ore and steelmaking mill scale as iron source, together with coke fines as carbon source, heated using microwave energy. Through the rotational central composite design technique, it was possible to evaluate the best conditions for the use of steelmaking scale residue as well as the effect of the applied microwave energy power. The results indicated that the developed process has relevant utility with up to 41.48% of reduction obtained. The outcomes contribute to a better understanding of iron recovery from steelmaking residues in reduction processes using microwave energy for heating, providing significant insight for the development of new clean technologies.

Application of graphite rods in producing Inconel 625 (UNS N06625) joints through the use of microwave radiation energy

Microwave energy is very efficiently being harnessed to join metallic materials these days. Although, use of microwaveenergy to join metallic materials is in its initial stage but, it has led to an outstanding development in the field of manufacturing. In this research work, joining of Inconel 625 (UNS N06625) without any filler material has been performed with the help of a novel process by harnessing microwave energy from a 900 W microwave applicator. Major novelty of thiswork is the application of graphite rods in accelerating the joining process based on the use of microwave radiation energydue to which it could become possible to join the Inconel specimens without using any filler powder. Selective microwave hybrid heating has been performed using six graphite rods and the process time taken for successful joining of Inconel625 specimens has been 360s. Three repetitions have been done using the mentioned process parameters. Mechanical characterization of the developed joints has been done with the help of Vickers micro-hardness tester and tensile testingmachine. The mean microhardness of the joints has been observed to be 325.1 HV at the joint region which came out to be 10.32 % more than that of the base alloy. The mean ultimate tensile strength has been observed to be 319.9 MPa with mean elongation of 5.3% which has been observed to be less than that of the base alloy.

Study of the high heating efficiency and uniformity by multi-port sweep frequency microwave irradiations

As a clean energy, microwaves have been widely used in thermal engineering. However, in the traditional microwave heating process, it is difficult to obtain high heating efficiency and uniformity. In this paper, a novel multi-port sweep frequency heating method is proposed to solve this problem. Multi-physics modelling and experiment are carried out to study the mechanism, efficiency, and uniformity of multi-port sweep frequency heating. The simulation and experimental results agree well, which demonstrates the proposed method can make heating more efficient and uniform. In addition, important factors affecting the heating efficiency and uniformity are also discussed, including the multi-port and frequency sweep effects, the polarization direction of the electromagnetic waves, and the bandwidth of the sweep frequency. This study can help us make better use of microwave energy.

Preparation of Activated Carbon from Bagasse by Microwave-Assisted Phosphoric Acid Activation

This research focuses on the utilization of bagasse as activated carbon (AC) under microwave-assisted phosphoric acid activation. The AC was activated using various frequencies of microwave energy combined with phosphoric acid before the carbonization process. Results indicated that the AC obtained from bagasse under microwave-assisted phosphoric acid had improved properties, i.e. fixed carbon, surface area, and iodine adsorption capacity. However, the loss of AC properties could be attributed to microwave energy exceeding a limit of 800 W. The optimum activated condition in this research was the use of microwave energy 500 W assisted phosphoric acid, which had fixed carbon, surface area, and iodine adsorption capacity at 88.34 ± 0.67 %, 781 m2/g, and 852 ± 6.0 mg/g, respectively.&#x0D; HIGHLIGHTS&#x0D; &#x0D; Microwave energy and phosphoric acid is applied to pretreat bagasse&#x0D; Bagasse pretreatment by microwave-assisted H3PO4 enhances the properties of AC&#x0D; Optimum condition is pretreatment by phosphoric acid and microwave energy at 500 W&#x0D; &#x0D; GRAPHICAL ABSTRACT