Microwave Irradiation Research Articles

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.

Effects of Microwave, Infrared and Laser Beams on Physicochemical and Functional Characteristics of Cornstarch

Effects of Microwave, Infrared and Laser Beams on Physicochemical and Functional Characteristics of Cornstarch

One-Pot Synthesis of Sustainable Fluorescent Nanomaterials via Microwave Irradiation as a Probe for the Determination of Metformin in Pure and Pharmaceutical Dosage Forms: Greenness and Whiteness Metrics.

A rapid, green and sensitive technique for the determination of metformin determination was developed based on the direct fluorescence enhancement of carbon dots (CDs) induced by the cited drug. The water-soluble CDs were prepared via a one-pot synthesis from avocado peels using domestic microwave. The prepared CDs exhibited strong fluorescence at 405 nm after excitation at 320 nm with a quantum yield of 51%. The fluorescence of CDs was enhanced linearly by increasing the concentration of metformin within the range 0.5-25 μg/mL with limit of detection 0.087 μg/mL and limit of quantification 0.263 μg/mL. The designed probe was proved to be selective toward metformin in the presence of other drugs such as vildagliptin and alogliptin and also in the presence of excipients in the pharmaceutical dosage form. The suggested and reported methods were compared with the help of the whiteness and greenness tools, specifically the white analytical chemistry and analytical greenness metric tools, for assessing hazardous solvents and reagents used.

Green Synthesis of Silver Nanoparticles Using <i>Citrus sinensis</i> Peels Assisted by Microwave Irradiation as a Contrast Agents for Computed Tomography Imaging

Contrast agents are extensively used to enhance the quality of images in computed tomography (CT) scans for brain exams, vascular imaging, and full-body imaging. Recent data indicate that iodine-based contrast agents have brief durations of blood circulation and may lead to harmful toxicity effects. This study aims to produce silver nanoparticles using environmentally friendly synthesis techniques facilitated by microwaves. The characteristics of nanoparticles have been studied using UV-vis, FTIR, XRD, and TEM techniques. The TEM analysis reveals that the silver nanoparticle has an average diameter of 9 nm and exhibits a spherical shape. The contrast-to-noise ratio (CNR) values of silver nanoparticles at 100, 150, and 200 mg/L concentrations are 35.79, 48.16, and 74.66, respectively. In comparison, iodine exhibits CNR values of 28.57, 34.69, and 48.56 at the same concentrations. The CNR values for tube currents of 140, 160, and 180 mA are 37.83, 44.98, and 48.26, respectively. In contrast, the CNR values in silver nanoparticles are 63.64, 75.32, and 81.67. The results obtained from the different concentrations and tube currents clearly demonstrate that silver nanoparticles have a higher CNR than iopamidol. Hence, silver nanoparticles have significant potential as contrast agents.

Box-Behnken design optimization of 2D Ti3C2Tx MXene nanosheets as a microwave-absorbing catalyst for methylene blue dye degradation

The 2D MXene Ti3C2Tx was synthesized from the precursor MAX phase Ti3AlC2 by etching the Al layer using hydrofluoric acid. Different Characterization techniques were employed to investigate the properties of the synthesized Ti3C2Tx. The degradation of methylene blue (MB) dye under microwave irradiation in the presence of the prepared 2D MXene was studied. It was found that the synthesized Ti3C2Tx was an excellent microwave catalyst for MB dye degradation, and results obtained were promising. Using this approach, the dye was almost wholly degraded with a degradation efficiency of 99.85 % in only 10 min without adding any oxidant. The degradation was found to follow the pseudo-first-order kinetic model, and the rate constants obtained varied from 0.10 and reached up to 0.67 min−1. The effect of pH, initial MB concentration and catalyst dosage on the MB dye degradation rate has been studied. It was found that carrying out the reaction at pH values ranging from 2 to 10 did not obviously affect its rate. On the other hand, lower initial MB dye concentrations and higher catalyst dosages significantly increased the degradation rate. The high degradation efficiency was found to be maintained for up to five successive catalytic cycles, ensuring the high stability of the synthesized 2D MXene Ti3C2Tx as a catalyst. Optimization of parameters affecting the degradation process was studied using response surface methodology (RSM). According to the Box-Behnken design, the optimal degradation efficiency (99.92 %) could be achieved by adding 21.24 mg of 2D Ti3C2Tx MXene catalyst and using an initial MB dye concentration of 53.06 ppm (mg/L) during a reaction time of 11.93 min.

Microwave-assisted dehydration of strontium hydroxide octahydrate: Experimental study and kinetic modeling analysis

In this context, the present study proposes the use of microwave irradiation to improve the dehydration rate and efficiency of strontium hydroxide octahydrate (Sr(OH)2·8H2O) without introducing contaminants. This study revealed that the use of microwave irradiation to dehydrate Sr(OH)2·8H2O is feasible and surprisingly efficient. The effects of this approach on important parameters were investigated using response surface methodology (RSM). The results revealed that the microwave dehydration process follows a linear polynomial model. In addition, compared with the heating time and material thickness, the microwave-assisted dehydration of Sr(OH)2·8H2O is sensitive to the microwave power and not to the material mass. The relative dehydration percentage reached 99.99% when heated in a microwave oven at 950 W for just 3 min. In contrast, a relative dehydration percentage of 94.6% was reached when heated in an electric furnace at 180 °C for 120 min. The XRD spectra also revealed that most of the Sr(OH)2·8H2O transformed into Sr(OH)2 after dehydration via microwave irradiation, whereas a significant portion of the Sr(OH)2·H2O remained after conventional electric dehydration. The experimental data were fitted and analyzed via the thin-layer drying dynamics model, and the results indicated that the dehydrating behavior of Sr(OH)2·8H2O could be well described by the Page model.

Influence of localized thermal effect of microwave heating on the carbothermic reduction process of ZnFe2O4

As an environmentally efficient method, microwave heating has been proposed to recover Zn from electric arc furnace dust (EAFD) recently. During the process, microwave irradiation has been shown to promote the reaction by lowering the reaction temperature and activation energy, in addition to providing efficient heat. However, the mechanism by which microwave heating promotes the zinc removal reaction of EAFD remains unclear. Thus, this study focused on ZnFe2O4, the primary component of EAFD, and developed an electromagnetic-thermal-chemical reaction coupling model to investigate the factors influencing the carbothermic reduction process of ZnFe2O4 and analyze the promoting mechanism of the microwave on the reaction. The main results indicate that the localized thermal effect, determined by the microwave distribution, exacerbates temperature differences and leads to non-uniform reaction behavior inside the sample. Increasing microwave power and graphite addition enhances the localized thermal effect, worsening field uniformity. In the simulation, the localized thermal effect of microwave heating reduced the activation energy of the zinc removal reaction to 252.97 kJ/mol, with an R2 reaction model. The assistance of the non-thermal effect in enhancing ion diffusion leads to a significant decrease in the activation energy observed in the actual microwave heating experiments.

Influence of Sulfur Addition on The Physical and Photocatalytic Properties Biosynthesized Se-doped ZnO Nanoparticles

Abstract The objective of this study was to investigate the influence of Sulfur (S) addition to selenium-doped zinc oxide (Se-ZnO) nanoparticles on their physical properties and photocatalytic activity. S,Se-ZnO sample was prepared by adding 1wt% sulfur onto 4%Se-ZnO nanoparticles. In the synthesis procedure, microwave irradiation was used as heating power and matoa leaf extract was used as a bioreductor. The nanoparticles were characterized using UV-Vis Spectroscopy, X-ray diffraction (XRD), and Field Emission Scanning Electron Microscopy (FESEM). The calculated band gap energies of Se-ZnO and 1% S,Se-ZnO are 2.38 eV and 2.62 eV, respectively. Both samples exhibit a hexagonal wurtzite structure. FESEM image of addition S reveals flower petal flake formations and decrease particle size of 187 nm. The photocatalytic activity of nanoparticles was evaluated through 4-nitrophenol (4-NP) degradation under UV-C irradiation. 1% S,Se-ZnO exhibits high photocatalytic efficiency compared to Se-ZnO, with a degradation percentage of 85.09% after 60 min and a reaction rate of -0.0315 min−1. Based on these results, the addition of S on Se-ZnO biosynthesized shows improve physical properties and efficient photocatalytic materials for pollutant removal.

Construction of novel dual wave-absorbing ZnFe2O4/CNTs nanoparticles with more hotspots for enhanced microwave-induced catalytic activity：Performance and mechanism

In this study, novel dual wave-absorbing ZnFe2O4/CNTs nanoparticles were successfully fabricated using a microwave hydrothermal method and applied for enhanced microwave-induced catalytic degradation of bisphenol A (BPA) in aqueous solution. The effects of various process parameters, including Fe3+ concentration (mass ratio of ZnFe2O4 to CNTs), MW irradiation time, MW power, initial BPA concentration, and catalyst dose on the degradation process were thoroughly assessed. The results indicate that ZnFe2O4/CNTs nanoparticles effectively utilize MW energy to generate more hot spots and exhibit superior MW catalytic activity at a 1.0:10.0 mass ratio (ZnFe2O4:CNTs), due to the synergistic effect between ZnFe2O4 nanoparticles and CNTs under MW irradiation. Additionally, hydroxyl radicals (·OH) play a major role in the degradation process, while superoxide radicals (·O2−) and holes (h+) play relatively minor roles. Potential intermediates and degradation pathways in the ZnFe2O4/CNTs/MW system have also been identified. Thus, the integrated ZnFe2O4/CNTs/MW technology shows great promise for treating environmental endocrine disruptors (EEDs) in water and wastewater.

Microwave Chemistry as a Candidate of Electrification Technology toward Carbon Neutrality—Microwave Magnesium Smelting as an Example

Microwave Chemistry as a Candidate of Electrification Technology toward Carbon Neutrality—Microwave Magnesium Smelting as an Example

Ciprofloxacin degradation over Co3O4 catalysts by the microwave-assisted persulfate oxidation: a critical role of coordination composition

The combination of catalysts and microwave (MW) effects presents an emerging approach for persulfate (PS) activation, while the effect of active sites of catalysts on the synergistic reaction remains poorly understood. Here, we regulated the coordination composition of Co3O4 by strategically controlling the oxygen atmosphere during fabrication. We found that Co3+ and Co2+ acted as reactive centers for microwave absorption and catalytic activation of persulfate, respectively. By altering the ratio between Co3+ and Co2+, we explored the Co3O4 (2.23)-550 catalysts with significantly improved synergistic activity for degrading ciprofloxacin (CIP), which was 33.0 and 26.8 times higher than PS- Co3O4 (2.23)-550 (without microwave) and MW- Co3O4 (2.23)-550 (without persulfate), respectively. Meanwhile, Co3O4 (2.23)-550 catalyst (0.5mgL-1) showed the highest degradation rate of CIP 92.6% (0.5mgL-1) within 10min under microwave. According to the radical identification and intermediate analysis, the efficient degradation of CIP was ascribed to both free radical and non-free radical pathways. Thus, this work raises new insights into the structure-activity relationship of catalysts, and provides an efficient way to eliminate antibiotics via synergistic catalysis.

Recovery of carbon fiber from carbon fiber reinforced polymer waste via microwave molten-carbonate pyrolysis

In recent years, the increased use of carbon fiber-reinforced polymer (CFRP) composites has led to a significant rise in waste production. To address this issue, a recycling method using microwave molten salt pyrolysis-oxidation has been proposed to efficiently process CFRP and obtain regenerated carbon fibers (RCFs) under the combined effect of microwave and Na2CO3/K2CO3/Li2CO3 composite molten salt. The mechanism of microwave molten salt pyrolysis was examined in conjunction with the pyrolysis products (pyrolysis oil and gas), furthermore, the microwave molten salt pyrolysis process was optimized. The causes of the changes in the mechanical characteristics and wettability of carbon fibers (CFs) were additionally investigated and analyzed. The RCFs recovered from previous composite materials were processed into new composite materials and mechanically tested to assess their reusability. The study found that using microwave pyrolysis at 350°C for 10 min followed by oxidation at 450°C for 20 min resulted in recovered carbon fibers (RCFs) that retained 98.81 % of the tensile strength of the virgin carbon fibers (VCFs). Additionally, the RCFs showed a tensile modulus enhancement of 14.70 %, with the recovery ratio of carbon fibers as high as 98.44 %. Pyrolysis generates combustible gases like hydrogen (H2), carbon monoxide (CO), and alkanes, alongside products primarily composed of phenols and aromatic compounds. The recycling method can quickly recover high-performance carbon fibers and valuable pyrolysis by-products from CFRP waste, making them highly valuable for resource recycling and the sustainable development of carbon fiber materials.

Microwave-assisted synthesis of silver nanoparticles using extract of unbaked cilembu sweet potato

Abstract Silver nanoparticle (AgNP) is one of attractive nanomaterials for biomedical applications, such as electroactive scaffold, antimicrobial treatment, anticancer therapy, and wound healing. Previously, AgNP was successfully synthesized using extract of Cilembu sweet potato (CSP) only if the extract was baked in oven at 120 °C for 60 minutes, which is an energy-intensive and time-consuming process. In this study, AgNPs was fabricated using unbaked extract of CSP with employing fast microwave heating instead of baking process. Microwave irradiation time were varied (0, 30, 60 and 90 seconds) to know the influence of microwave irradiation time on particles size and morphology of the obtained AgNPs. The obtained samples were evaluated using UV-Visible spectroscopy, dynamic light scattering and transmission electron microscopy to know the surface plasmon resonance characteristic, average particles size and morphologies of the obtained AgNPs respectively.

Understanding the kinetics of waste plastic catalytic pyrolysis under microwave irradiation for enhanced resource valorization

The increasing accumulation of ABS plastic waste poses significant environmental challenges, necessitating efficient methods for its disposal and recycling. The pyrolysis of the ABS plastic waste was performed under various heating programs including constant heating rate (27.5, 42.2 and 65 K min−1), and sample-controlled reaction rate (0.01 min−1) to obtain the TG curves using the in-house developed microwave assisted thermogravimetric analyzer. Fe-impregnated SiC was used as thermal and chemical catalyst, while neat SiC played only thermal catalyst role. The modified Sestak-Bergren equation used to model the TG data by Pearson’s linear correlation and associated parameters n = 1.129 and m = 0.27 was achieved. The comparison of normalized form of the conversion function (f (α)/f (0.5)) with the most common models of solid-state reactions showed that random scission model (L2) was the most suitable approach to physically explain the pyrolysis of ABS plastic waste. Furthermore, by applying isoconversional kinetic analysis, the variation of activation energy (Eα) with conversion value was approximately constant. The Eα obtained was 140.5 and 63.7 kJ/mol with SiC and Fe/SiC, respectively. These findings hold practical implications for industrial applications or waste management strategies, particularly when considering the developed microwave-assisted real-time TGA-pyrolysis, which can enhance the efficiency and sustainability of plastic waste recycling processes.

Interface/Dipole Polarized Antibiotics-Loaded Fe3O4/PB Nanoparticles for Non-Invasive Therapy of Osteomyelitis Under Medical Microwave Irradiation.

Due to their poor light penetration, photothermal therapy and photodynamic therapy are ineffective in treating deep tissue infections, such as osteomyelitis caused by Staphylococcus aureus (S. aureus). Here, a microwave (MW)-responsive magnetic targeting composite system consisting of ferric oxide (Fe3O4)/Prussian blue (PB) nanoparticles, gentamicin (Gent), and biodegradable poly(lactic-co-glycolic acid) (PLGA) is reported. The PLGA/Fe3O4/PB/Gent complex is used in combination with MW thermal therapy (MTT), MW dynamic therapy (MDT), and chemotherapy (CT) to treat acute osteomyelitis infected with S. aureus-infected. The powerful antibacterial effect of the PLGA/Fe3O4/PB/Gent is determined by the synergistic effects of heat and reactive oxygen species (ROS) generation by the Fe3O4/PB nanoparticles under MW irradiation and the effective release of Gent at the infection site via magnetic targeting. The antibacterial mechanism of the PLGA/Fe3O4/PB/Gent under MW irradiation is analyzed using bacterial transcriptome RNA sequencing. The MW heat and ROS reduce the activity of the protein transporters on the bacterial membrane, along with the transport of various ions and the acceleration of phosphate metabolism, which can lead to increased permeability of the bacterial membrane, damage the ribosome and DNA, and accompany the internal protein efflux of the bacteria, thus effectively killing the bacteria.

Environmental and Convenient Construction Strategy to Obtained New Supreme Series of Fused 1,2,4-Triazalo System Incorporating N-Acetyl Quanazole

The presentation goal is to develop new procedures for regioselective synthesis of unusual series of heterocyclic compounds (2-8) derived from N-acetyl guanazole (1) which received a great deal of attention due to it's unique properties. N-acetyl guaunazole used as active precursor to obtained two type of fused 1,2,4-triazole system. The first one including grinding for (1 min.) of a mixture consist of N-acetyl guanazole , malononitrile and substituted benzaldehlyde through direct one-pot multicomponent reaction to achieve a new series of 1,2,4-trazolo[1,5-a,4,3-a]bispyrimidine (2-7). Whereas, the second one involved firstly the conversion of N-acetyl gluanazole to the corresponding Schiff base (8-13) accelerated by microwave irradiation (MWI) for few minutes, then they will underwent intercyclization reaction with phenyl isothiocynate and also acceclerated by grinding then by microwave irradiation to afford 1,2,4-triazolo[1,5-a,4,3-a] bistriazine (14-18).

Sintering behavior of alumina by microwave hybrid sintering

Microwave sintering is considered an ideal sintering process due to its rapid heating rate, low energy consumption, and uniform temperature distribution between the interior and surface. However, the difficulty of using a dilatometer and the lack of systematic research have hindered the investigation of activation energy and grain growth kinetics during microwave sintering. In this study, we examined the internal heating mechanism of microwave hybrid sintering, its sintering behavior, and its applicability to commercial processes such as tape casting. The results demonstrated that microwave hybrid sintering reduces the activation energy for both shrinkage and grain growth, confirming the presence of the "microwave effect." This study underscores the potential of microwave hybrid sintering for commercial applications, especially for large ceramic components.

Photocatalytic Degradation of Transition Metal (Ni) Doped ZnS Nanoparticles Synthesized via Simple Solvothermal Route

Ni doped ZnS nanoparticles were obtained using the simple Solvothermal Microwave Irradiation (SMI) method in this research. This technique is cost-effective and results in a high level of uniformity in particle size. The sample's structural characteristics were examined utilizing XRD Technique, FESEM image, Elemental analysis of the as prepared sample obtained from EDX spectrum and their optical characteristics analysed by using UV-Visible absorption study. The XRD pattern of Ni doped ZnS nanoparticles were to obtain their crystallite size (D), lattice constant (a), and volume of the unit cell (V). As the concentration of Ni dopant increased (0, 2.5, 5.0) M %, the values of the lattice constant decreased, leading to an overall decrease in the volume of the unit cell. FESEM images reveals the sample have uniform surface morphology and EDX analysis give evidence for element Zn, Ni, S presents in the sample. Ni doped ZnS nanoparticle dimension strongly influences their optical characteristics. The optical bandgap, as obtained from UV-Vis measurements, ranges from 3.54 eV to 3.50 eV with doping concentrations varying from 0 M% to 5.0 M% .This adjustment in optical properties suggests that Ni-doped ZnS nanoparticles have diverse applications in optoelectronics, sensors, UV detectors, and as an efficient photocatalyst for degrading pollutants in water. The efficiency of the degradation of Methylene Blue dye by Ni doped ZnS nanoparticles was found to be 75.19%.

ZnSnS Nanoparticles Synthesized by Simple SMI Technique for Photocatalytic Application

Photocatalysis, driven by semiconductor nanoparticles under visible or ultraviolet light, has emerged as a powerful and sustainable approach for environmental remediation and clean energy production. In this study, we investigate the photocatalytic potential of tin (0, 2, 4, 6, 8, 10) mole % alloyed with zinc sulfide (ZnSnS) nanoparticles as efficient catalysts for various environment and energy-related applications. ZnSnS nanoparticles were produced via a simple microwave irradiation technique. Comprehensive structural characterization through X-ray diffraction (XRD), FESEM, EDAX and HRTEM confirmed the successful incorporation of tin atoms into the ZnS crystal lattice. Optical study indicated significant blue shifts in the absorption edge, extending the light absorption into the visible region, a key advantage for photocatalytic applications. Photocatalytic experiments were conducted to evaluate the performance of Zn-alloyed SnS nanoparticles in degrading organic pollutants and hydrogen evolution from water splitting reactions. Our results revealed remarkable enhancements in photocatalytic activity. The enhanced efficiency can be credited to the creation of fresh energy levels within the bandgap, aiding in the separation and movement of charges, and also to the heightened light absorption caused by the reduced bandgap. Furthermore, stability tests indicated the durability of (ZnSnS) nanoparticles, making them suitable candidates for long-term applications in real-world environments. The observed photocatalytic activity enhancements hold promise for addressing environmental issues, including wastewater treatment, air purification, and hydrogen production for clean energy.

Facile Synthesis and Characterization of Pure and Bi-doped ZnS Nanoparticles for Photocatalytic Application

In the present research, a simple solvothermal microwave irradiation (SMI) method has been adopted for the preparation and synthesis of pure and Bi doped ZnS nanoparticles using zinc acetate, bismuth acetate, thiourea and ethylene glycol were utilized as precursors. As-synthesized pure and Bi doped ZnS nanoparticles were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDAX), ultraviolet-visible (UV-vis) spectroscopy and Field emission scanning electron microscopy (FESEM). From the XRD and EDAX studies, crystallite size, lattice parameter and analysis of the elemental compositions are calculated and analyzed respectively. The UV-vis spectra revealed that the optical band gap energy of pure and Bi doped ZnS nanoparticles was calculated. The FESEM shows that the average particle size spherical and agglomerated of as-synthesized pure and Bi doped ZnS nanoparticles sizes were decreased. In addition, the photocatalytic activity of pure and Bi doped ZnS nanoparticles was studied with methylene blue dye in an aqueous solution under UV light irradiation; the 5.0 mol % of Bi doped ZnS nanoparticles dye degradation efficiency of the sample was calculated as 75% in 120 minutes.