Effect Of Microwave Irradiation Research Articles

Eco-friendly utilization of microwaves for extraction of dye from logwood and Its application onto silk

For minimizing the pollution associated with synthetic colorants, the world again is going to realize the benefits of natural colorants in applied fields such as textiles, food flavors, etc. As part of the ongoing research project, hematein is being investigated as a potential natural colorant derived from logwood chips, and its implementation on silk fabric is being investigated under the effect of microwave radiations. A number of dyeing variables, including pH, dyeing duration, temperature of the dye bath, volume of extraction, and salt concentration, have been investigated, and the effect of isolation medium has also been evaluated. For new shades with improved fastness ratings, extracts of various sustainable bio-mordants and chemical mordant such as salts of aluminum and copper, and tannic acid were also used. An experiment revealed that treating un-irradiated silk with 40 mL of methanolic extract with a pH of 2, irradiated for 6 min, produced outstanding outcomes when dyed at 90°C for 60 min. The dyeing process included the addition of 9 g of salt per 100 mL of solution as an exhausting agent. In these circumstances, the utilization of sustainable mordants has not only enhanced the ratings of color fastness but has also rendered the procedure more environmentally friendly and less polluting. Therefore, microwave radiation has great potential for extracting colorants from plants and effectively applying them to natural materials under decreased conditions.

Raman Thermometry for Temperature Assessment of Inorganic Transformations During Microwave Heating

ABSTRACTMicrowave heating is an intriguing method for the synthesis of inorganic solids offering a variety of advantages over conventional furnace heating, such as fast heating and cooling rates as well as volumetric and selective heating of precursors. However, there are many open questions regarding this “black‐box” process, and insights into the effect of microwave radiation on different types of solids are generally missing. In situ Raman spectroscopy is a powerful technique to unravel chemical transformations and identify intermediate species during microwave solid‐state syntheses. A major challenge is the temperature measurement under microwave conditions because (metallic) thermocouples cannot be used and optical pyrometry has significant drawbacks. In contrast, Raman thermometry is a viable method that relies on the temperature‐induced shift of Raman signals. Here, we use this method to estimate the temperature during microwave heating of a model system (titania) that undergoes a phase transition at temperatures >800°C. The estimation is derived from a flexible double exponential calibration function applied to Raman spectroscopic peak shifts in the temperature‐resolved furnace heating data, which was found to describe two titania modes (one anatase and one rutile) extremely well. Based on a detailed error and uncertainty analysis, we suggest options to further optimize Raman thermometry for use in high‐temperature microwave heating conditions.

MoS2 Decorated on 1D MoS2@Co/NC@CF Hierarchical Fibrous Membranes for Enhanced Microwave Absorption.

The design and development of high-quality electromagnetic waves (EMW) absorbing materials play a vital role in combating the escalating negative effects of microwave radiation and interference. Herein, MoS2@Co/NC@CF fibrous membranes are successfully fabricated by electrospinning technology and carbonization, and a molybdenum disulfide (MoS2) layer is synthesized on the surface of these fibers via hydrothermal method. The seed-assisted growth method not only effectively avoids the accumulation and improves the loading of ZIF-67 particles, so as to ensure that the magnetic components in the fibers are evenly distributed in a wider range, rather than only intermittently present in some sites. Meanwhile, the introduction of semiconductor MoS2 as the shell further optimizes the impedance matching and improves the EMW absorption performance of the carbon fibrous membranes: the minimum reflection loss (RLmin) is -67.56dB, and the maximum effective absorption bandwidth (EABmax) is further expanded to 6.56GHz (2.1mm, 11.44-18GHz). This work provides a feasible method for developing high-efficient EMW-absorbing materials.

Effects of Microwave Treatment on Alkyd-Varnished Wood Exposed to Outdoor Conditions

In this study, it was planned to investigate the effects of microwave irradiation (MW) prior to varnish applications on the pine wood samples, which are subjected to three months of outdoor exposure. The samples of 180W15s, 270W15s, 360W5s, and 360W15s showed lower water sorption properties than the control, while the rest of the samples showed higher sorption properties than the control sample. The lowest water sorption value was 12.50% (-3.85% lower than the control). It was found that post-microwave treated samples provide a 1–3 degree increases in resistance against selected cold liquids of distilled water, fruit juice, milk and coke under similar conditions. After three months of outdoor exposure of the samples, the surface scratch resistance of the samples was found to be 1 to 4 degrees softer than the control sample (HB to 3B pencil hardness properties). However, the cross-cut properties of the samples showed almost similar level of adhesion properties, mostly between 2 and 3 (control sample: 3), which was assumed to be not notable different from control, regardless of treatment conditions. It was found to have various discoloration properties of the samples which subjected to weathering procedure of post-microwave treated and alkyd-varnish aplied samples. But the larger-sized samples (A-type) have a higher and wider range for b* (yellowness) and a* (redness) values, while smaller-sized samples (a-type) showed a wider range and higher brightness (L*) properties. Moreover, A-type samples had higher total color difference values than a-types at similar treatment conditions. It is important to note that all measured samples show an ΔE >1.0 (metric) value, which means the discoloration after three months of outdoor exposure could be realizable when carefully examined by the human eye. The results clearly indicated that the post-microwave radiation before alkyd-varnish application on pine wood samples were some level influences regarding the selected properties. The resistance of selected household cold liquids and surface cross-cut properties were prominent for some samples. In spite of wide properties measured, no any clear trend was found between MW radiation and selected properties.

Microwave Irradiation as a Powerful Tool for Isolating Isoflavones from Soybean Flour

The use of microwave irradiation energy for isolating bioactive compounds from plant materials has gained popularity due to its ability to penetrate cells and facilitate extraction of intracellular materials, with the added benefits of minimal or no use of organic solvents. This is particularly significant due to the possibility of using extracts in the food and pharmaceutical industries. The aim of this work is to examine the effect of microwave irradiation on the extraction of three of the most important isoflavones from soybean flour, glycitin, genistin, and daidzin, as well as their aglycones, glycitein, genistein, and daidzein. By varying the extraction time, temperature, and microwave power, we have established the optimal parameters (irradiation power of 75 W for 5 min) for the most efficient extraction of individual isoflavones. Compared to conventional maceration and ultrasound-assisted extraction, the total phenol content of the extracts increased from 3.66 to 9.16 mg GAE/g dw and from 4.67 to 9.16 mg GAE/g dw, respectively. The total flavonoid content increased from 0.38 to 0.83 mg CE/g dw and from 0.48 to 0.83 mg CE/g dw, and the antioxidant activity increased from 96.54 to 185.04 µmol TE/g dw and from 158.57 to 185.04 µmol TE/g dw, but also from 21.97 to 37.16 µmol Fe2+/g dw and from 30.13 to 37.16 µmol Fe2+/g dw. The positive correlation between microwave extraction and increased levels of total phenols, flavonoids, and antioxidant activity demonstrates the method’s effectiveness in producing bioactive compounds. Considering the growing recognition of glycitein’s potential role in medical and pharmaceutical applications, microwave-assisted extraction under optimized conditions has proven highly efficient.

Study on the electromagnetic-thermal-mechanical coupling damage of concrete under microwave irradiation

The paper aims to explore the thermal response of three-dimensional random aggregate concrete model under microwave irradiation. The multi-field distribution in concrete by coupling of the electromagnetics, heat transfer and solid mechanics in COMSOL Multiphysics software under microwave irradiation was investigated. The results shown that the different in dielectric properties and thermal expansion coefficients between aggregate and mortar resulted in the generation of temperature gradients and stress concentration at interface. In addition, due to the larger expansion coefficient of aggregate compared to mortar, stress concentration was formed at interface, promoting the damage of concrete. Microwave power exhibited a notable influence on thermal accumulation and thermal stress. Higher microwave power correlating to higher growth rates of temperature and stress. The Von Mises stress in mortar was significantly greater than that in aggregate, as energy absorption reached a certain threshold, damage occurred in mortar. In addition, microwave frequency significantly influenced the distribution of electric field within the cavity, and also the energy conversion ratio of aggregate within concrete. The study could provide a comprehensive understanding of heating effects of microwave radiation on concrete, providing the mechanical basis for microwave-assisted concrete recovery.

Energy storage and fracture characteristics of brittle rock with rockburst proneness after microwave irradiation

Microwave irradiation has been considered a promising solution for high-temperature cracking rock. Most of the current researches are concentrated on investigating the effects of microwave irradiation on the physical and mechanical properties of rock. However, there is a paucity of reports on the application of microwave irradiation for controlling rockburst disasters. The novelty of this investigation lies in the utilization of microwave irradiation to modify the energy storage capacity and fracture characteristics of brittle rock with rockburst proneness. Based on the phenomenon of overheating in rock under microwave irradiation, the concept of progressive damage in granite was proposed for the first time. The weakening of energy storage capacity due to microwave irradiation was evaluated by defining an energy storage coefficient. A novel index for assessing the rockburst proneness of brittle rock was proposed. By combining this index with the strain energy release rate, the potential value of microwave irradiation in reducing the proneness and intensity of rockburst was explored. This study also introduced the concept of "sensitive stress level" which influences the closure state of cracks, and found that SSL and mechanical properties show high sensitivity to microwave power. A threshold power of 4.5 kW was identified, at which numerous parameters undergo significant changes.

Evaluating microwave energy impact on 3G snacks: A study on dielectric properties and expansion

Third-generation (3G) snacks, a food type of widespread interest in the industry, have a longer shelf life than second-generation (2G) snacks. The primary regeneration process for these snacks involves frying and microwaving. However, only a few studies have detailed the effects of microwave irradiation on these products. This study aims to analyse the influence of the type of material, compression, and microwave power on the expansion capabilities of the pellets. Four raw materials (rice flour, rice semolina, corn semolina, and wheat starch) were combined with water to achieve uniform moisture content and extruded into pellets with different compression ratios (1:1, 2:1, and 3:1). The elaborated samples were processed at different microwave powers (heating rates of 2 and 10 °C/s) using an instrument capable of accurately delivering microwave energy to food samples while monitoring key process parameters, including dielectric properties. Samples with high starch content, low protein content, and low fibre content, in conjunction with higher compression ratios exhibited a more pronounced expansion.

Tannin removal from Persian gum and investigation of physicochemical properties: Comparing different methods

Persian gum (PG) is a novel natural exudate gum and the main challenge regarding PG is tannin content of gum which limits its application in food and pharmaceutical industries. In fact, tannins are known as anti-nutrient compounds because they limit bioavailability of proteins and minerals. Hence, in this study, the effect of microwave radiation (180, 450, 600 W for 5 min), autoclaving (121 °C for 20 min), boiling (5, 10 and 15 min) and soaking either in water or saline solutions (mono- and divalent salts) was evaluated to remove tannins from Persian gum. Moreover, the effect of tannin removal on the physicochemical properties was investigated by evaluation of rheological properties (flow behavior and viscoelastic tests), zeta potential and Fourier transform infrared spectroscopy (FTIR) data. Our outcomes demonstrated that the highest tannin removal efficiency found to be 75.67 ± 0.25, 74.32 ± 0.54 and 67.08 ± 0.19 % which belonged to soaking in water (180 min), soaking in CaCl2 solution (1% w/v, 90 min) and boiling (15 min) treatments of brownish PG granules, respectively (p < 0.05). Interestingly, removal of tannin increased apparent viscosity of PG dispersion. Based on oscillatory tests, boiling treatment caused exhibition of solid-like behavior, in contrast to control sample. Tannin removal reduced zeta potential and the lowest reduction belonged to the gums soaked in water (from -32.3 to -28.7 mV); however, formation of ion-bridging in the presence of CaCl2 caused a remarkable decrease. FTIR analysis declared that in the boiled sample, a decrease was detected in vibration intensity within the range of 3200–3500 cm−1 (-OH groups) which can be due to heat degradation. Findings of the present research confirmed that soaking in water is a low-cost and practical method for tannin removal of PG, which almost had no negative effect on physiochemical properties of gum.

Effect of microwave irradiation on the synthesis of zeolite with ferrierite structure: Study of acid and catalytic properties

Ferrierite zeolite (FER) was synthesized under microwave conditions while varying the microwave exposure time from 6 to 12 h. For comparison, commercial FER and a FER zeolite synthesized by the conventional hydrothermal synthesis (72 h) were studied. The structure, texture, and acidic properties of the samples were investigated by XRD, low-temperature N2 adsorption, ICP-AES, SEM, and DRIFT spectroscopy using adsorption of CO, CD3CN and pyridine as probe molecules. The catalytic characteristics of the obtained zeolites were studied in the cyclocondensation reaction of 1,2-phenylenediamine and acetone to produce 1,5-benzodiazepine. The activity of the zeolites in this reaction was found to increase with increasing microwave exposure time. The FER-MW sample synthesized in 12 h showed the best results.

Microwave-assisted TBM cutter for efficient hard rock fracturing in high stress environments

Elucidating the effects and fundamental mechanisms of microwave-assisted mechanical excavation under high initial stress conditions is of paramount importance for enhancing the efficiency of deep resource extraction. In this study, indentation experiments were conducted on microwave-damaged rock under initial stress conditions using a tunnel boring machine (TBM) for the first time. By integrating acoustic emission, digital image correlation, and the discrete element method, we conducted a comprehensive analysis of the multifaceted effects of microwave irradiation and initial stress on rock fracturing. The rock-breaking efficiency was evaluated based on the volume of broken rock and the energy consumption. The indentation failure of the sample can be divided into three stages: microfracture closure, elastic deformation, and unstable crack propagation. The microwave irradiation reduced the peak load during the indentation process and simultaneously reduced the brittleness of the specimen. The experimental and simulation results jointly demonstrated the existence of an initial stress threshold in the rock fracturing process. When the initial stress is below the threshold, it suppresses the extension of rock fractures, which is unfavorable for rock fragmentation. When the initial stress exceeds the threshold, stress-induced rock failure occurs, which promotes rock fragmentation. A notable observation is that microwave irradiation alters the initial stress threshold of the rock, where a higher microwave power correlates with a lower initial stress threshold. This indicates that the optimal parameters for microwave equipment must be reconsidered when the initial stress changes. Methods for optimizing rock breakage at initial stress were suggested and examined.

Uptake of substances into living mammalian cells by microwave induced perturbation of the plasma membrane

Delivering foreign molecules and genetic material into cells is a crucial process in life sciences and biotechnology, resulting in great interest in effective cell transfection methods. Importantly, physical transfection methods allow delivery of molecules of different chemical composition and are, thus, very flexible. Here, we investigated the influence of microwave radiation on the transfection and survival of mammalian cells. We made use of an optimized microwave-poration device and analyzed its performance (frequency and electric field strength) in comparison with simulations. We, then, tested the effect of microwave irradiation on cells and found that 18 GHz had the least impact on cell survival, viability, cell division and genotoxicity while 10 GHz drastically impacted cell physiology. Using live-cell fluorescence microscopy and image analysis, we tested the uptake of small chemical substances, which was most efficient at 18 GHz and correlated with electric field strength and frequency. Finally, we were able to obtain cellular uptake of molecules of very different chemical composition and sizes up to whole immunoglobulin antibodies. In conclusion, microwave-induced poration enables the uptake of widely different substances directly into mammalian cells growing as adherent cultures and with low physiological impact.

Fe3C/Fe implanted hierarchical porous carbon as efficient electromagnetic wave absorber

The rapid development of communication technology has led to severe microwave pollution, which presents a challenge for microwave-absorbing composites. Current research suggests achieving superior microwave absorption requires the use of multi-component operation and ingenious structural design. Consequently, the present study has prepared continuous porous carbon (CPC) materials doped with large amounts of Fe3C/Fe nanoparticles (Fe@CPC) using carbonization and acid etching. By balancing the advantages of the above strategies, it is possible to address issues such as poor impedance match, single loss capacity, easy oxidation of magnetic metals/alloys, and the limited absorption bandwidth of conventional absorbing materials at the same time. The material exhibits a minimum reflection loss of −23.2 dB with an efficient absorption range of 5.3 GHz at 1.9 mm at a filler content of just 10 wt% in the paraffin matrix. In this paper, the samples with a continuous porous structure were prepared by a simple method, and the properties were excellent due to the appropriate preparation method and the synergistic effect of the multi-component composite. The porous structure facilitates the presence of a considerable number of active sites, which enables the loading of a substantial quantity of metal ions. Furthermore, nanoparticles are capable of aggregating and dispersing on the surface. This paper presents a theoretical framework for understanding the synergistic effect of microwave radiation through interfacial polarization and micro-scale magnetic interaction. Nevertheless, there are still obstacles to overcome in terms of achieving precise control over the structural design and ensuring the compatible integration of metal components.

Research on the safety risks of microwave irradiation on motion balance perception in electric power environments

To the microwave irradiation safety hazards caused by the co-construction of towers in smart grids, this paper investigates the effects of microwave irradiation in the power environment on the biological motion balance perception function. Firstly, simulation of microwave signals in the electric power environment, i.e., low-frequency harmonics and high-frequency carriers, were realized by signal modulation and applied in four types of behavior testing scenarios. Then, determining rats as target organisms to replace workers and randomly dividing into groups in proportion: open field, rotating rod fatigue, beam walking and forced swimming. Configuring radar with various parameters to match the electric power irradiation scene and stimulate rats, monitoring the abnormal behavior by image processing module, including posture, motion trajectory, distance, and other features. The experimental result showed that exposed to microwaves induce rats motor ability decline, balance perception imbalance, together with paralysis within long-term exposure, and its locomotor activity, coordination, posture control and reaction time all exhibit varying degrees of weakening. These findings indicate that microwave irradiation in electric power environment may pose significant health and safety risks for worker.

Effect of Microwave Radiation on the Southern Cowpea Bettle &lt;i&gt;Callosobruchus maculatus&lt;/i&gt; (F)

This study investigated the effect of microwave radiation at different power levels of 100, 300, and 600 w at different exposure durations of 60, 80, and 100 sec, against eggs, first-instar larvae, and adults of the southern cowpea beetle Callosobruchus maculatus (F). The results showed significant differences in mortality, and 600 w with exposure time of 100 sec being superior. There was 100% mortality of eggs, first-instar larvae and adult; the incubation period of the eggs increased with exposure. The germination of cowpea grains was not significantly affected.

Effect of microwave radiation on adult neurogenesis and behavior of prenatally exposed rats

Postnatal neurogenesis appears to be highly sensitive to environmental factors, including microwave electromagnetic radiation (MWR). Here, we investigated the impact of MWR during intrauterine development on juvenile and adult neurogenesis in the rostral migratory stream (RMS) and the dentate gyrus of the hippocampus in the rat brain, as well as its effect on animal behavior. Female rats were exposed to MWR at a frequency of 2.45 GHz for 2 hours daily throughout pregnancy. The offspring of irradiated mothers survived to either juvenile age or adulthood. The brains of the rats were subjected to morphological analysis, assessing cell proliferation and death in both neurogenic regions. In the RMS, the differentiation of nitrergic neurons was also investigated. The effect of MWR on behavior was evaluated in rats surviving to adulthood. Prenatal MWR exposure caused significant changes in the number of proliferating and dying cells, depending on the age of the animals and the observed neurogenic region. In addition, MWR attenuated the maturation of nitrergic neurons in the RMS in both juvenile and adult rats. Morphological alterations in neurogenesis were accompanied by changes in animals’ behavior. Affected neurogenesis and changes in animal behavior suggest a high sensitivity of the developing brain to MWR.

The influence of thermal radiation during microwave-assisted freeze-drying of pharmaceutical unit doses

New drying technologies for biologicals have recently been developed to accelerate the time-consuming batch freeze-drying (BFD) process. Among others, microwave-assisted freeze-drying (MFD) has been suggested as a faster and more effective drying technology. In this study, MFD cycles with the microwave radiation switched on and off were performed to assess the contribution of the microwave radiation to drying acceleration. It was found that thermal radiation emitted by the drying chamber walls was predominantly accelerating the drying of monodose placebos rather than microwave radiation. The combination of ultra-low chamber pressure, high thermal heat transfer and a short primary-to-secondary phase transition reduces drying times by more than 80 % compared to conventional BFD. In a second step, a design of experiment approach was used to assess the effect of thermal radiation versus microwave radiation and their combination, together with dosage properties such as fill volume and excipient concentration upon drying rate. The outcome showed the importance of high fill volume and high excipient concentration for an effective microwave contribution to the drying rate. Nevertheless, the drying acceleration for small pharmaceutical dosages with restricted solutes was mainly driven by thermal radiation rather than 2.45 GHz microwave radiation. The inability of ice to convert microwave energy into heat hampers the potential use of microwave freeze-drying for single-dose vaccines.

Effect of Microwave Radiation on the Properties of Hydrogel, Cork, Perlite, and Ceramsite.

The present work analyzes the effect of releasing physically bound water from hydrogel, cork, perlite, and ceramsite on materials exposed to microwave radiation and subsequently investigates possible changes in the physical properties of these materials (water absorption and thermal conductivity coefficient). The release of physically bound water from individual materials has potential practical applications in materials engineering, for example, in the internal curing of concrete, where individual aggregates could, under the influence of microwave radiation, release water into the structure of the concrete and thus further cure it. Experimental analysis was carried out with samples of the above-mentioned materials, which were first weighed and then immersed in water for 24 h. Then, they were weighed again and exposed to microwave radiation. After exposure, the samples were weighed again, left immersed in water for 24 h, and weighed again. The focus of the study was on the ability of the aggregates to release water due to microwave radiation and on the changes in the properties (water absorption, thermal conductivity coefficient) of these materials when exposed to microwave radiation. The samples were further monitored by digital microscopy for possible changes in the surface layer of the materials. The hydrogels show the highest water absorption (1000%) and the fastest water release (45 min to complete desiccation). After the release of water due to microwave radiation, their ability to absorb water is maintained. Of interest, however, is that in the case of almost complete removal of water from the soaked hydrogel, the original powdered state of the hydrogel is not obtained, but the outcome has rather a solid structure. In the case of cork, the water absorption depends on the fraction of the material.

Effect of Microwave Irradiation on Lead Adsorption Properties of Vermiculite with Different Particle Sizes.

The expansion of vermiculite using microwave irradiation is an environmentally friendly and efficient method that can enhance the material's adsorption performance. This study investigated the microwave irradiation of vermiculite with five different particle sizes (4/2/1/0.5/0.2 mm) and found that the adsorption capacity for Pb2+ increased with larger particle sizes. The equilibrium adsorption capacity reached 15.98 mg/g at 4 mm, representing a 45.01% improvement compared to 0.2 mm. The pseudo-second-order kinetic model effectively described the adsorption kinetics. No significant differences were observed in the specific surface area and pore size distribution of all samples. Thermogravimetric quantitative analysis revealed that larger particle sizes retained interlayer water more effectively. As the particle size decreased, the interlayer water content generally showed a decreasing trend. Fourier-transform infrared spectroscopy analysis also indicated that the -OH groups in larger particle sizes exhibited higher stability. The results suggest that the high content and stability of -OH groups may be key factors in the enhanced adsorption performance for Pb2+. This provides new insights for the preparation of environmentally friendly adsorbent materials rich in hydroxyl groups.

Effect of microwave irradiation and conventional heating on high pressure modified white finger millet starch hydrogel properties

High pressure modified (200 MPa and 400 MPa for 10 min) white finger millet starch hydrogels were prepared with three starch concentrations (12 %, 15 % and 18 % (w/v)), by conventional heat treatment (75 °C for 12 min) and microwave treatment (50 s at 900 W, surface temperature 75 °C). The prepared hydrogels were compared to native white finger starch hydrogels for understanding the effect of modification as well as the gel synthesis method. Effect of the storage period on physical stability was evaluated for ten days by evaluating weight loss, water activity, and color. The whiteness index of the prepared hydrogel intensified during the storage period, and water activity was reduced (0.99–0.976). While stored at 4 °C, the hydrogel weight decreased due to moisture migration. The results emphasize that treatment conditions, starch modification, and concentration significantly affected water absorption. The maximum gel strength was identified for conventional heat-induced 400 MPa high-pressure modified hydrogel stored for ten days. 1H NMR relaxation time showed microwave-induced gel synthesis had a shorter relaxation time. The gel microstructure helped to correlate the swelling and gel strength increment in the modified gel sample, as it had a higher wall thickness and a smaller pore size than heat-induced hydrogels. These findings help to conclude high pressure modified white finger millet starch hydrogel synthesised by microwave irradiation can be alternative to conventional heat gelatinisation method.