Microwave Radiation Research Articles

Fracture characteristics and thermal damage mechanism of shale under microwave radiation

Fracture characteristics and thermal damage mechanism of shale under microwave radiation

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.

Feasibility Analysis for Predicting Indian Ocean Bigeye Tuna (Thunnus obesus) Fishing Grounds Based on Temporal Characteristics of FY-3 Microwave Radiation Imager Data

Efficient and accurate fishery forecasting is of great significance in ensuring the efficiency of fishery operations. This paper proposes a fishery forecasting method using a brightness temperature (TB) time series spatial feature extraction and fusion model. Using Indian Ocean bigeye tuna fishery data from 2009 to 2021 as a reference, this paper discusses the feasibility of fishery forecasting using FY-3 Microwave Radiation Imager (MWRI) Level 1 TB data. For this paper, we designed a deep learning network model for radiometer TB time series feature extraction (TimeTB-FishNet) based on the Convolutional Neural Network (CNN), Gated Recurrent Unit (GRU), and Attention mechanism. After expanding the dimensions of TB features, the model uses them together with spatiotemporal feature factors (year, month, longitude, and latitude) as features. By adding the GRU and Attention to the CNN, the CNN-GRU-Attention model architecture is established and can extract deep time series spatial features from the data to achieve the best results. In the model validation experiments, the TimeTB-FishNet model performed optimally, with a coefficient of determination (R2) of 0.6643. In the generalization experiments, the R2 also reached 0.6261, with a root mean square error (RMSE) of 46.6031 kg/1000 hook. When the sea surface height (SSH) was introduced, the R2 further reached 0.6463, with a lower RMSE of 45.1318 kg/1000 hook. The experimental results show that the proposed method and model are feasible and effective. The proposed model can directly use enhanced radiometer TB data without relying on lagging ocean environmental product data, performing deep temporal and spatial feature extraction for fishery forecasting. This method can provide a reference for the fishing of bigeye tuna in the Indian Ocean.

Green extraction of colorants from achiote seeds for dyeing mordanted nylon fabric

The extraction of sustainable colorants requires energy efficient technology for their eco-application in different fields. For current study on nylon fabric, the natural dye from achiote (Bixa orellana) has been extracted in aqueous and acidic media and valorized through microwave (MW) radiation. MW treatment has been applied to both extracted biomolecule and nylon fabric up to 10 min and the dyeing variables were optimized using statistical model. For getting permanent shades eco-salts of Al (III) and Fe (II) as well as biomolecules from waste plant materials (pomegranate and myrobalan) were utilized. ISO methods for assessment of colorfast shades have been employed. It was found that for nylon, by MW treatment of the dye material and polymeric stuff for 4 min, good color yield in terms of color strength (K/S=29.52) is obtained. It has been observed that when MW treated extract (pH=6) is employed at 40 °C for 55 min, good quality shade of high strength is obtained by using selected amounts of eco-chemical and organic molecules. It is concluded that MW treatment should be given to dyeing process for getting effective yield and tannin based green molecules as organic mordant can used to make dyeing process more ecofriendly and sustainable.

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.

A Sustainability Study upon Manufacturing Thermoplastic Building Materials by Integrating Chicken Feather Fibers with Plastic Waste

The article explains how to make thermoplastic construction materials by combining waste from chicken feathers with plastic waste. The initial phase focused on a new and environmentally friendly method of sterilizing raw feathers using microwave radiation inside sealed ovens with circulating air. Additionally, composites containing varying feather amounts using two different polymer matrices were fabricated through an injection process, followed by mechanical and physical tests on the samples. Because of their excellent characteristics, products made from a combination of chicken feather waste and plastic waste could effectively replace traditional wood–plastic composites that are polyvinyl chloride-based. The recycling technology was assessed for its environmental impact, and sustainability was proven economically and environmentally.

Induction of orbital currents and Kapitza stabilization in superconducting circuits with Laguerre-Gaussian microwave beams

We investigate the effects of a Laguerre-Gaussian (LG) beam on the superconducting state. We show that the vortex angular momentum of a LG beam affects the superconducting state and induces currents. The induction of the current by microwave radiation is illustrated on a Josephson loop and SQUID devices. In particular, we establish that coupling a dc SQUID to the ac magnetic flux of a LG beam can stabilize the π phase in the SQUID. This can happen via developing a global or local minimum in the effective potential at π. In the latter case, this happens via the Kapitza mechanism. Published by the American Physical Society 2024

Modeling Kinetics and Transport Mechanism Study of Poorly Soluble Drug Formulation in High Acidic Medium

Some medicinal particles are poorly soluble in highly acidic solutions, particularly those subjected to various production processes. Therefore, the present research investigated the kinetics and mechanisms of the drug release rate of newly formulated solid pills in a low pH medium. Three pills were prepared: one from a non-moisturized powder mixture (PILD) and the other two, PILC and PILM, from the dried powder mixtures, which were dried using hot-air heating and microwave radiation, respectively. These pills were subjected to drug release tests, and the outcomes were considered in the kinetics investigation using various models. Zero-order, Hixson–Crowell, First-order, Higuchi, Hopfenberg, Korsmeyer-Peppas, Logistic, and Peppas-Sahlin were the kinetic models used to inspect the release rate mechanism of these tablets. It was found that the Peppas-Sahlin and zero-order were the most reliable models to represent the drug release profile of all prepared pills with very high accuracy, estimated by R^2>0.99. The Hixon and first-order models were the weakest to characterize this work outcome. This work also applied these models to describe the controlling mechanism of the drug release for each prepared pill. It is detected that the non-Fickian diffusion and polymer chain relaxation control the PILC’s release behavior. However, case II transport and super case II transport with erosions is the dominant mechanism for PILD and PILM pills, respectively. Additionally, new semi-empirical models were modified to describe the kinetics of the solid release of those tablets with greater accuracy.

The role of microwave radiation in extractive desulfurization of real diesel fuel for green environment: an experimental and computational investigation

The process of removing sulfur compounds and aromatic compounds to produce clean fuel is an important and effective contribution to the processes of mitigating and adapting to climate change. In contrast, it is necessary to find an innovative way to remove sulfur and carcinogenic aromatic compounds because clean, low-sulfur diesel is commonly used in all countries of the world at the present time. Therefore, in this work, we have studied the effect of the microwave radiation power and the irradiation time with the use of more than one type of organic solvent; methanol, acetonitrile and ethyl acetoacetate; as an extractant and solvent to feed ratio impact on the removal of sulfur and aromatic compounds of a real diesel fuel feed which has 450 ppm sulfur content and 16 wt% aromatic Content. The results showed that the best solvent used during this work was ethyl acetoacetate. According to the results, high sulfur removal (≈ 92%) was accomplished with microwave-assisted extractive desulfurization technique under the following ideal conditions: the irradiation time is 7 min, the solvent feed ratio is 3:1 and the microwave intensity is 180 W. To reveal the mechanism of microwave-assisted extractive desulfurization via different organic solvents, a theoretical study including structural examination and interaction energy analysis on the interaction between dibenzothiophene (DBT) or dimethyl dibenzothiophene (DMDBT) and the different organic solvents was also conducted.

Mechanical and fracture characteristics of weak microwave-absorbing sandstone under microwave irradiation: influence of pore water

Microwave radiation is an effective method to weaken the strength of hard rock, but this weakening effect is not obvious enough for weak microwave-absorbing rocks. This work focuses on the role of water in amplifying the effect of microwaves on weak microwave-absorbing rocks, by examining the bursting characteristics of the rocks as well as their physical and mechanical properties before blasting. The experimental results show that when subjected to microwave irradiation, and the time taken for this bursting decreases with higher microwave power. In addition, the surface temperature of saturated sandstone gradually rises with increased irradiation power and duration. Under high microwave power, the uniaxial compressive strength (UCS) of heated saturated sandstone notably decreases within the same irradiation duration. When the microwave power is low, the UCS of saturated sandstone remains relatively unchanged over time. The UCS of dry sandstone exhibits no significant alteration under identical irradiation power and duration. In conclusion, sandstone shows no significant change in its physical and mechanical properties during brief exposure to low-power microwave irradiation in its dry state. As water within the sandstone undergoes a phase transition from liquid to gas due to microwave irradiation, the resulting steam pressure causes the sandstone to rupture.

Ionic Liquid as a Catalyst toward NIPU via a Microwave Radiation Process

Ionic Liquid as a Catalyst toward NIPU via a Microwave Radiation Process

Mechanism insights for impedance matching in split-ring resonator topologies under bio-medical scenarios

The utilization of microwave radiation has gained increasing importance in various biological applications. However, a significant challenge remains in the interaction between the microwaves and the human skin, primarily due to the impedance mismatch. Recently, the employment of split-ring resonator (SRR) topologies has become increasingly prevalent for addressing such a problem. Despite this, most existing literatures lack a comprehensive understanding of the underlying mechanisms. In this study, we follow Babinet’s principle and numerically study the dispersion relations of a single-split-ring resonator (S-SRR) and its complementary topology, single-complementary-split-ring resonator (S-CSRR). We focus on conducting the impedance analysis, along with far-field and near-field excitation characterizations. The results indicate that S-CSRR ensures an improved impedance matching, thereby significantly enhancing microwave power flow within the bio-tissue. A 2 × 2 array of S-CSRR is experimentally examined for validation. We demonstrate that the S-CSRR array enhances the total specific absorption rate (SAR) of a deeply-implanted-tumor-phantom by a factor of 1.95. Our work may provide a broader understanding towards impedance matching, which may facilitate the design of more efficient diagnostic tools in bio-medical field.

Comparative analysis of microwave radiation generated by the interaction between electron beam and plasma under different methods

This article presents a physical model that describes the interaction between surface electron beams and plasma. The dispersion relations for beam plasma interactions were derived using perturbation method and field matching methods. The study investigates how different parameters affect radiation frequency and bandwidth. The results indicate that as electron beam velocity increases, the associated kinetic energy also rises, leading to an increase in both the maximum radiation frequency and bandwidth at high frequencies. Conversely, the radiation bandwidth at low frequencies decreases. Similarly, a higher plasma density results in a greater maximum radiation frequency, but the high-frequency bandwidth decreases, while the low-frequency bandwidth increases. Additionally, when the electron density and electron velocity of the electron beam remain constant, increasing the plasma density can increase the microwave radiation frequency However, there exists a plasma density threshold, beyond which high-frequency electromagnetic waves are no longer radiated.

Study of Dielectric Properties of Binary Mixtures of n-Octanol and N,N-Dimethylformamide in Lower Microwave Radiation

Study of Dielectric Properties of Binary Mixtures of n-Octanol and N,N-Dimethylformamide in Lower Microwave Radiation

Microwave-induced alterations in the structure of coals at different metamorphic stages

Despite the global trend toward decarbonization, coal continues to play a significant role in energy production, as current renewable energy sources cannot fully meet the increasing global energy demand. The main objective of decarbonization is to reduce greenhouse gas emissions, especially carbon dioxide. Enhancing coal usage efficiency can help decrease these emissions. Electromagnetic activation of bituminous coal is already employed for dehydration, ash removal, desulfurization, and improving the grinding process of raw coal. This research aims to study the specifics of coal electromagnetic activation using microwave radiation and its effects on the physical and chemical processes occurring in coals at different metamorphic stages. The results suggest that this electromagnetic treatment leads to the destruction of hydroxyl groups and the formation of free hydrogen. Coals at higher metamorphic stages heat up faster due to their higher structural density. Coals at lower metamorphic stages take longer to heat up and require more processing time to be effective, while lower power levels are necessary to avoid mechanical breakdown. Activation time and coal particle size are significant factors; their optimal combination provides the maximum effect. These findings contribute to optimizing microwave treatment parameters for different coal types, potentially enhancing coal utilization efficiency and reducing environmental impact.

Evaluation of lignocellulatic activity of enzymes from microwave-irradiated Pleurotus sajor-caju cultivated with wheat straw

The production of lignocellulytic enzymes by microwave-radiated Pleurotus sajor-caju was assayed. Wheat straw was employed as substrate to P. sajor-caju for production of laccase, manganese peroxidase (MnPase), filter-paperase (FPase), carboxmethyl cellulase (CMCase), and cellulase (as evaluated using microcrystalline cellulose). P. sajor-caju exposed to 10 s of microwave radiation (MR) showed maximum growth with colony radius of 7.17 ± 0.45 cm, while with increasing the exposure time up to 50 s the growth decreased up to 2.67 ± 0.22 cm. Moreover, it failed to grow at 80 s of exposure time. Cellulase, MnPase, FPase, CMCase, and laccase activities were induced to 37 ± .0.54, 49 ± 2.36, 189 ± 2.12, 0.37 ± 0.06, and 1.58 ± 0.03 U/mL compared to that at control 31 ± 0.25, 46 ± 1.25, 177 ± 1.65, 0.28 ± 0.03, and 1.37 ± 0.12 U/mL, respectively as a result of P. sajor-caju exposure to 10 s of MR. As the exposure time increased, these enzymes activity decreased. Different levels of moisture with surfactant (polysorbate 80) were applied to optimize the enzymes activities at 10 s of exposure time. The optimum activities 3.15 ± 0.23, 0.62 ± 0.06, 269 ± 5.36, 65 ± 1.63, and 48 ± 0.98 U/mL were recorded for cellulase, MnPase, FPase, CMCase, and laccase, respectively at 70% of moisture and 0.15 mL/L of polysorbate 80.

Remarkable improvement in the NOx storage ability of Pd/SSZ-13 zeolite PNA via a facile pretreatment strategy

A facile strategy was employed to pretreat Pd/SSZ-13 zeolite obtained via the initial-impregnated method under a microwave field, aiming to greatly enhancing the NOx storage-release ability. By investigating the effect of microwave treatment parameters (power, atmosphere and time) on the improvement of PNA performance, the optimal conditions were determined (175 W, 10 % O2/N2, 15 min). Under these conditions, the Pd/SSZ-13 exhibited an enhanced NOx adsorption and desorption amount to 2.60 and 2.38 times, respectively, compared to the untreated sample after three cycles of NO-TPD. Deeper insights into the variations in Pd/SSZ-13 properties induced by the microwave radiation were clarified through a series of characterizations. The micropore surface area of Pd/SSZ-13 zeolite activated by microwave increased by 3.91 %, and the micropore volume also improved by 3.85 %, which might facilitate the adhesion of more active Pd species to the materials surface, and aid in the dispersion of PdOx clusters into the zeolite channels. After microwave activation, the average particle size of Pd decreased from 10.09 nm to 7.08 nm. Particularly, the content of Pd(II) species such as Pd2+, [Pd(OH)]+ and PdO as active NOx adsorption sites enhanced from 66.68 % to 68.93 %. Additionally, the microwave treatment not only increased the number of Lewis and Brønsted acid sites, but also strengthened the interaction between NOx molecules and the zeolite skeleton. The above reasons collectively promoted the NOx storage-release properties of Pd/SSZ-13 zeolite, showing that the microwave pretreatment is a highly efficient strategy for improving the performance of PNA materials.

A Comparative Study of Microwave Welding Using Multiwalled Carbon Nanotubes and Silicon Carbide Nanowhiskers as Microwave Susceptors

Recently, microwave welding has arisen as an advanced joining method due to its versatility and rapid heating capabilities. Among others, microwave susceptors play a crucial role in microwave welding, as different classes of microwave susceptors have distinct microwave heating mechanisms. In this work, polypropylene (PP) was utilized as a thermoplastic substrate and two types of microwaves susceptors, namely multiwalled carbon nanotubes (MWCNTs) and silicon carbide nanowhiskers (SiC NWs), were studied for microwave welding. The susceptor was first dispersed in acetone to form susceptor suspension. Next, the susceptor suspension was deposited onto the targeted area on substrate and paired with another bare PP substrate. The paired sample was then exposed to 800 W microwave radiation in a microwave oven. Afterward, the welded joint was evaluated using a tensile test and scanning electron microscopy to determine its joint strength and cross-section microstructure. The results showed that the joint strength increased as the heating duration increased. The welded joint formed using MWCNTs achieved a maximum strength of 2.26 MPa when 10 s was used, while the SiC NWs-formed welded joint achieved a maximum strength of 2.25 MPa at 15 s. This difference in duration in forming a complete welded joint can be attributed to the higher microwave heating rates and thermal conductivity of MWCNTs. However, increasing the heating duration to 20 s caused severe deformation at the welded joint and resulted in low joint strength. Overall, this study highlights the significance of understanding the microwave heating mechanism of different susceptors and provides essential insight into the selection of a microwave susceptor for microwave welding.

Moisture dependence of responses in physical–chemical property and CH4 ad-/desorption capability of coals to microwave radiation

For purpose of understanding feasibility of coalbed methane (CBM) production in practical water (H2O)-containing reservoirs by using microwave radiation, the dielectric property highly associated with microwave-absorbing and resultant temperature-rising capabilities of coals were addressed primarily; afterward, the temperature-rising rule of coals and its dependence on moisture were examined; finally, the impacts of moisture on changes about main physical–chemical property and resultant CH4 ad-/desorption performance of coals were investigated under microwave field. Results indicated that the coals display microwave-absorbing potential to raise temperature. The moisture initially increases the temperature-rising rate owing to its strong microwave-absorbing capability while decreases the final bulk temperature because of its endothermal evaporation. The resultant temperature decomposes and transforms minerals. Moreover, the temperature rise upgrades crystallite structure of the dried coals. As for the wetted coals, the rapid temperature rise disorders crystallite structure of the Sihe and Yima coals due to potential steam explosion. Furthermore, the radiation decreases the aromaticity and the total surface oxygenic groups of the dried coals; the moisture whittles down these decreasing trends. In general, the micro- and mesopore surface area and volume of the coals drops after radiation. The microwave radiation smooths pore surface of the wetted coals while roughens that of the dried coals. The complexity of the coal pore structure almost reduces after radiation. Besides, the microwave radiation significantly reduces the CH4 adsorption capability of the dried coals by 6.74–36.69%; the moisture further reduces the CH4 adsorption capability by 20.48–43.03%. Ultimately, the microwave radiation almost enhances the ad-/desorption hysteresis of CH4 on the dried coals while weakens that of the wetted coals. Such alterations depend on the responses of pore abundance and pore surface roughness to microwave. These findings confirm that microwave radiation is a promising option to produce CBM, particularly for H2O-bearing CBM reservoirs.

Synthesis of 1,2,4-triazole-based deep eutectic solvents modified nickel ferrite nanoparticles and their application in dispersive solid phase extraction of triazole pesticides prior to LC-MS/MS analysis

A dispersive solid phase extraction method using new magnetic nanoparticles based on nickel ferrite was introduced for the extraction of six triazole pesticides (penconazole, hexaconazole, tebuconazole, diniconazole, triadimefon, and difenoconazole) from water samples before liquid chromatography-tandem mass spectrometry analyses. Initially, a new deep eutectic solvent was synthesized with 1,2,4-triazole and n-octanol for surface modification of the nanoparticles easily achieved through microwave radiation. The nanoparticles morphology, magnetic properties, adsorption capacity, isotherms, and crystalline patterns of the sorbent were examined. The capability of the sorbent was evaluated by extracting the target pesticides from water samples showing significant differences in adsorption capacity and efficiency between the modified and non-modified nanoparticles. High extraction recoveries (68-86%) were achieved for the analytes using small amounts of the sorbent with low limits of detection (0.03-0.08 ng mL-1) and quantification (0.13-0.29 ng mL-1), a wide linear range (0.29-250 ng mL-1), and acceptable precision (relative standard deviations ≤6.9%).