Application Of Microwave Technology Research Articles

New self-organised benzo[b]thiophene-based materials for GHz applications

ABSTRACT This research delves into the synthesis and characterisation of novel liquid crystal compounds derived from benzo[b]thiophene cores, focusing on their potential applications in microwave technology. Two synthetic strategies were developed to construct rigid cores, resulting in the successful synthesis of 10 compounds with varied terminal groups and lateral substituents. Correlations between molecular structure and mesomorphic properties were elucidated through extensive comparative analysis. Birefringence measurements and quantum chemical calculations further provided insights into the optical properties and polarisability anisotropy of the synthesised compounds. The results highlight the influence of structural diversity on the compounds’ suitability for microwave applications. Specifically, compounds featuring carbon–carbon triple bonds and polar terminal groups demonstrated enhanced birefringence and polarisability values, indicating their potential in microwave device fabrication. This study underscores the importance of molecular design in optimising liquid crystal materials for advanced technological applications.

Leveraging novel microwave techniques for tailoring the microstructure of energy storage materials

In the dynamic landscape of energy storage materials, the demand for efficient microstructural engineering has surged, driven by the imperative to seamlessly integrate renewable energy. Traditional material preparation methods encounter challenges such as poor controllability, high costs, and stringent operational conditions. The advent of microwave techniques heralds a transformative shift, offering rapid responses, high-temperature energy, and superior controllability. This review critically examines the nuanced applications of microwave technology in tailoring the microstructure of energy storage materials, emphasizing its pivotal role in the energy paradigm and addressing challenges posed by conventional methods. Notably, non-liquid-phase advanced microwave technology holds promise for introducing novel models and discoveries compared to traditional liquid-phase microwave methods. The ensuing discussion explores the profound impact of advanced microwave strategies on microstructural engineering, highlighting discernible advantages in optimizing performance for energy storage applications. Various applications of advanced microwave techniques in this domain are comprehensively discussed, providing a forward-looking perspective on their untapped potential to propel transformative strides in renewable energy research. This review offers insights into the promising future of leveraging microwaves for tailoring the microstructure of energy storage materials.

An applicator for high-power rock comminution using microwave technology in the megawatt range

Abstract The mining industry is heavily dependent on energy-intensive processes, such as rock breakage, which leads to significant operational costs. This paper explores microwave-assisted rock breakage as an innovative method to enhance the efficiency of comminution within the mining industry. It introduces a system that employs a Klystron microwave power source with a maximum output of 7.5 MW, using a $\mathrm{TM}_{010}$ single-mode cavity at 3 GHz, to channel energy inside a specially designed rock cavity. The paper emphasizes the importance of designing an efficient microwave cavity for this system, focusing on the cavity’s design and simulation. Through both simulated results (using HFSS software) and experimental observations, the study reveals the promising application of microwave technology in the field of mining. The simulated frequency response of the designed cavity (S11) is −22 dB, it demonstrates significant potential for reducing both energy consumption and associated costs. Additionally, the designed cavity is fabricated from aluminum and filled with polyether ether ketone material. The measured frequency response (S11) of the cavity at 3 GHz is −17 dB.

Structural and cation distribution analysis of Nickel-Copper/Nickel-Magnesium Substituted Lithium Ferrites

Lithium ferrite (Li0.5Fe2.5O4) shows significant promise in electrical and electronic engineering. It possesses a crystal spinel crystal structure denoted as AB2O4, with "A" and "B" representing specific tetrahedral and octahedral lattice sites respectively. Analysis of X-ray diffraction (XRD) patterns aligns well with the JCPDS card (no. 38-0259), confirming the spinel structure with the Fd3m space group. However, an additional peak at 211 in the basic lithium ferrite suggests a subtle Fd3m to the P4132 phase change with a minor secondary hematite phase. Investigating the cation distribution in these ferrites is crucial for further exploration of their magnetic and dielectric properties. These ferrites find widespread applications in microwave technology and magnetic and electric energy storage devices.

Advanced Microwave Strategies Facilitate Structural Engineering for Efficient Electrocatalysis.

In the dynamic realm of energy conversion, the demand for efficient electrocatalysis has surged due to the urgent need to seamlessly integrate renewable energy. Traditional electrocatalyst preparation faces challenges like poor controllability, elevated costs, and stringent operational conditions. The introduction of microwave strategies represents a transformative shift, offering rapid response, high-temperature energy, and superior controllability. Notably, non-liquid-phase advanced microwave technology holds promise for introducing novel models and discoveries compared to traditional liquid-phase microwave methods. This review examines the nuanced applications of microwave technology in electrocatalyst structural engineering, emphasizing its pivotal role in the energy paradigm and addressing challenges in conventional methods. The ensuing discussion explores the profound impact of advanced microwave strategies on electrocatalyst structural engineering, highlighting discernible advantages in optimizing performance. Various applications of advanced microwave techniques in electrocatalysis are comprehensively discussed, providing a forward-looking perspective on their untapped potential to propel transformative strides in renewable energy research. It provides a forward-looking perspective, delving into the untapped potential of microwaves to propel transformative strides in renewable energy research.

Microwave Treatment of Minerals and Ores: Heating Behaviors, Applications, and Future Directions

The application of microwave technology in mineral metallurgy is a transformative approach to ore processing that offers new ideas about the current progressive depletion of resources and the environmental impact of mineral processing. This review delves into the principles, applications, and future directions of microwave treatment in mineral and ore processing. Microwave technology, characterized by its unique advantages such as rapid and uniform heating, selective heating, and energy efficiency, stands in contrast to traditional heating methods. It directly interacts with materials at the molecular level, enabling volumetric heating. The review encompasses a wide range of applications, including ore pre-treatment, drying, mineral processing, hydrometallurgy, smelting, and reduction. It highlights the role of microwave treatment in enhancing metal recovery, reducing energy consumption, and improving processing speeds. Future research directions are identified, focusing on enhanced equipment design, process optimization, integration with conventional methods, and technological innovations. The comprehensive overview assists researchers, engineers, and decision-makers in understanding the potential of microwave technology in mineral metallurgy, emphasizing its contribution to innovation and sustainability in the sector.

Mechanistic insights into microwave-accelerated permeation through graphene-based membranes

Two-dimensional (2D) membranes, composed of stacked 2D nanomaterials, are increasingly utilized in separation fields due to their structured interlayer channels and ease of modification. The application of microwave technology to 2D membrane separation enhances permeability, but the unclear strengthening mechanism limits the further applications of this technique. This study aims to elucidate the fundamental principle behind microwave-accelerated permeability by investigating the performance of two distinct 2D membranes in response to microwaves: a microwave-transparent graphene oxide (GO) membrane and a microwave-absorbing GO-based membrane doped with molybdenum disulfide (MoS2-GO). Experimental results demonstrate that compared to conventional heating, microwave irradiation amplifies water and ethanol permeation flux through the GO membrane by 122% and 154%, respectively, without observed changes in membrane structure via SEM, XRD, and Raman analyses. In addition, the microwave accelerated permeation also occurs (by 110%) when Rhodamine B - aqueous solution was used as feed liquid, while the rejection rate was remained at above 99%, indicating the promising applications of microwave technology in sewage treatment. Further experiments show that the microwave-induced augmentation of water/ethanol permeation through the GO membrane was primarily governed by the dielectric loss values of the feed liquid. In contrast, this dependence vanished in the MoS2-GO membrane, indicating that accelerated permeation was mainly determined by the interaction between microwaves and diffusing molecules in the 2D channels, disrupted by microwave absorbing MoS2 in the latter case. These findings offer comprehensive insights into the enhancement of membrane permeation induced by microwave irradiation.

Application of microwave technology to extract pure sesame oil

The purpose of the study was to use microwave technology to extract pure sesame seed oils. The findings of investigations on how microwave treatment affects sesame seed yields for oil and cake are reported. It has been demonstrated that the radiation strength and duration of processing have a major impact on oil production. Studies have shown the possibility of increasing the yield of sesame oil, compared to obtaining oil with preliminary heat treatment of sesame seeds, by 1.97% by treating them with steam and subsequent treatment with microwave radiation for 12 minutes. In these circumstances, the oil output is 33.72%, the cake yield is 66.28%, and the moisture content is reduced to 3.77%. The oil content of the seeds, the intensity of the microwave radiation, and the length of the process are the primary factors affecting the amount of oil released. The best technical parameters have been determined, at which 33.72% of the oil and 66.28% of the cake are extracted.

Impact of holes in an interdigital parallel folded coupled line‐based wideband bandpass filter for X‐band applications

AbstractIn this paper, a study on the effects of strategically implemented holes in a miniaturized wideband bandpass filter (BPF) utilizing interdigital folded coupled lines is presented. First, the BPF is designed to produce the passband by introducing a fold in the coupled lines. The passband is centered at 9.3 GHz (X‐band), catering to radar applications. Coupled lines connected to a modified U‐shaped transmission line comprise the filter's design configuration. The novelty of the design resides in incorporating drilled holes along the coupled lines, which generate perturbations and resonant effects, resulting in enhanced impedance variations and improved filter performance. With the aid of electromagnetic analysis and simulation software, the coupled lines, U‐shaped transmission lines, and drilled hole diameters are all optimized. Vector Network Analyzer performs all the measurements and draws the comparisons. An increment of 22.58% is seen in return loss as it increases from −24 to −32 dB, and the insertion loss shows an increase of 16.74%. The proposed filter has been subjected to analytical study, simulation, and implementation, which have confirmed its exceptional return loss, favorable insertion loss, and compact dimensions. The research results make a valuable contribution to the development of miniaturized wideband BPFs, specifically focusing on their use in radar systems. In such systems, the ability to accurately and efficiently filter signals is paramount. The design insights and performance improvements presented in this study have significant implications for broader applications in microwave engineering and communication systems.

Effects of particle size and morphology on microwave cracking characteristics and cracking mechanism of three Fe-containing ores

Microwave irradiation is a potential technology for use in rock fracturing. It is of great significance for the application of microwave technology in metal mines to understand the microwave cracking characteristics of ores and the mechanism of microwave action of ores. Taking Hongtoushan copper ore, Sishanling iron ore, and Dandong gold ore as research objects, the microwave cracking characteristics of ores with different morphologies (bulk/particle samples) and particle sizes were investigated. The microwave action mechanism of ores was revealed based on dielectric properties and arc characteristics. The results show that the change in morphology of the ore affects the microwave cracking characteristics thereof. The failure of iron ore and gold ore is characterized by the generation of cracks and the crack direction is related to the ore morphology. The bulk copper ore is not damaged after microwave irradiation, but the damage to particles of copper ore is characterized by scorching or scorching and melting accompanied by cracks. The more power applied, the larger the particles, and the stronger the arcing. Compared with the type and morphology of ore, particle size has little effect on dielectric properties. The microwave action mechanism of bulk copper ore (smooth surface) is a reflection effect and that of bulk copper ore (rough surface) is a discharge effect. The microwave mechanism of action on particulate copper ore is the combined action of discharge and heating effects, which leads to fracture. The microwave mechanism of action on iron ore and gold ore is mainly one of heating. The research results provide guidance for the development of microwave ore-cracking equipment and the selection of the optimal heating sequence.

Application of Microwave Technology in Different Fields for Energy Saving and Emission Reduction

In today's world, security of energy supply and greenhouse gas emissions due to rising energy demand are seriously threatening sustainable energy development, and it is urgent to promote energy structure reform. Microwave, as a clean and environmentally friendly green energy source, has developed rapidly in recent years. Unlike traditional heating methods, microwave heating generates heat through the random motion of polar molecules. This results in microwave heating having the advantages of selective heating, fast temperature rise, easy control and high heating efficiency. This allows microwaves to make a contribution in advancing the reform. of the energy mix. This paper investigates the use of microwave technology in different industries to save energy and reduce emissions. It finds that in the ironmaking industry, microwaves can speed up the reduction time of iron ore, reduce carbon dioxide emissions, while making iron ore more easier to crush and magnetically sort during iron ore pretreatment process. In the food industry, microwaves can reduce the time required to cook and dry, and maximise the retention of nutrients in food. In the field of waste recycling, microwaves reduce the volume of bottom radioactive waste in a shorter time and improve the efficiency of desulphurisation of waste rubber. In the Budur reaction, microwaves reduce the temperature required for the reaction and increase the conversion of carbon dioxide. After summarising the advantages of microwave technology, this paper also analyses the current shortcomings of microwave technology, introduces microwave-related patents and concludes with an outlook on the future of microwave technology.

Dynamical modes in a vertical nanocontact-based spin Hall nano-oscillator

Spin-torque nano-oscillators (STNOs) with high nonlinear tunability can serve as nanoscale spin-wave emitters for high-speed magnon-based logic circuits and neural networks for promising new energy-efficiency computing. Although various STNOs have been modeled theoretically and characterized experimentally, there is a sustained effort to improve their coherence and nonlinear tunability. By using numerical simulation, here we explore the evolution rule of spectral characteristics and nonlinearities of the emitted coherent spin waves in a type of spin Hall nano-oscillator (SHNO) with a perpendicular magnetic anisotropy (PMA) coefficient ${K}_{u}$, which is based on a vertical nanocontact fabricated on an extended heavy metal/ferromagnet bilayer. There exist three distinct dynamic regimes with varying ${K}_{u}$. At the easy-plane anisotropy-dominated in-plane magnetized regime, the SHNO exhibits coexistence of the nonlinear self-localized spin-wave bullet mode with a significantly negative nonlinearity coefficient $\ensuremath{\aleph}$ and a secondary high-frequency quasilinear edge mode at higher current density. The latter excitation is supported by the energy transfer from the former via nonlinear coupling rather than the injected spin currents located in the center nanogap of the device. When the easy-plane shape anisotropy is effectively compensated by PMA, only a single quasipropagating spin-wave mode with a near-zero $\ensuremath{\aleph}$ is excited at lower current density, consistent with minimization of nonlinear damping due to the suppression of nonlinear mode coupling. For the out-of-plane magnetized SHNOs with ${K}_{u}$ above the demagnetization energy, a well-defined propagating spin-wave mode with a positive $\ensuremath{\aleph}$, characterized by a significant frequency blueshift and a rightward elongated spatial profile perpendicular to the in-plane component of the applied magnetic field, is observed. This detailed evolution diagram of auto-oscillating dynamics on the PMA coefficient ${K}_{u}$ provides a practical approach to selectively excite dynamical modes and optimize the spectral characteristics of the SHNO for applications in microwave technology and spin-wave logic.

Inverse Design of Dual‐Band Optically Transparent Metasurface Absorbers with Neural‐Adjoint Method

AbstractMassive applications of microwave technology have led to a large amount of electromagnetic pollution, which seriously interferes with the normal operation of communication systems in people's daily life. Optically transparent metasurface absorber is emerging as a promising candidate for solving this problem in some specific scenarios. When designing multiband metasurface absorbers, the coupling within the cell structure generally prevents the independent modulation of the absorption effect in each band. The rapid development of deep learning provides a new way for designing high‐performance metasurface. Here, a forward network model is built to predict the absorption spectrum of the metasurface absorber. In the network model, 1D (one‐dimensional) inverse convolution is used as the upsampling layer, which enables the network model to have a good prediction on small data sets while avoiding overfitting on large data sets. Based on the network model, a dual‐band optically transparent metasurface absorber is also designed by employing the neural‐adjoint (NA) method. The results taking advantage of deep learning method for high‐efficiency design of metasurface absorbers without considering the coupling effect, have shown great capability to optimize the absorption efficiency of different frequency bands independently, which may provide an alternative way to design other multiband microwave devices.

A flux-tunable YBa2Cu3O7 quantum interference microwave circuit

Josephson microwave circuits are essential for the currently flourishing research on superconducting technologies, such as quantum computation, quantum sensing, and microwave signal processing. To increase the possible parameter space for device operation with respect to the current standards, many materials for superconducting circuits are under active investigation. Here, we present the realization of a frequency-tunable, weakly nonlinear Josephson microwave circuit made of the high-temperature cuprate superconductor YBa2Cu3O7 (YBCO), a material with a high critical temperature and a very high critical magnetic field. An in situ frequency-tunability of ∼300 MHz is achieved by integrating a superconducting quantum interference device (SQUID) into the circuit based on Josephson junctions directly written with a helium ion microscope (HIM). Our results demonstrate that YBCO-HIM-SQUID microwave resonators are promising candidates for quantum sensing and microwave technology applications.

Evaluation of Microwave Synthesis of Ceramic Pigments Based on In Situ Dielectric Characterization.

The application of microwave technology for efficient and environmentally friendly synthesis of ceramic pigments is a successful and rapidly evolving area of research. However, a clear understanding of the reactions and their relationship with the material absorbance has not been fully achieved. The present study introduces an in situ permittivity characterization technique, which serves as an innovative and precise tool for assessing the microwave synthesis of ceramic pigments. Several processing parameters (atmosphere, the heating rate, raw mixture composition and particle size) were evaluated by studying the permittivity curves as a function of temperature to elucidate their effect on the synthesis temperature and the final pigment quality. The validity of the proposed approach was verified through correlation with other well-known analysis techniques, such as DSC or XRD, providing valuable information about the reaction mechanisms and the optimum conditions for the synthesis process. In particular, changes in permittivity curves were linked, for the first time, to undesired metal oxide reduction at too-high heating rates and could be used to detect pigment synthesis failures and ensure product quality. The proposed dielectric analysis was also found to be a useful tool for optimizing raw material composition for the microwave process, including the use of chromium with lower specific surface area and flux removal.

Current Status and Way Forward of Microwave Hybrid Heating in India: A Bibliometric Analysis

Automotive and aerospace industries are keen to employ unique techniques and novel materials to reduce weight and cost and improve part performance. The application of microwave technology in the processing of metallic materials is a relative breakthrough in this direction. Recently, microwave hybrid heating (MHH) has evolved to extend the technique's utility further. Several studies on MHH have been carried out worldwide in the last three decades, and India is the prime contributor. This article documents a systematic and bibliographic review of MHH (between 1998-2022) in the Indian scenario. For this purpose, 125 documents are chosen from Scopus Core Collection and analyzed using a bibliometric analysis tool. The research status is examined based on the time distribution of articles, geography, top-cited documents, citation mapping of journals and researchers, mapping of co-occurrence, analysis of authors' keywords, country-wise publications, and cluster assessment. The result establishes that India is dominating, followed by theUSA. Moreover, there is an increasing trend in the number of publications. A guideline is also included to revive the research community's interest to mature the process further.

Moisture measurement of tea leaves during withering using multifrequency microwave signals optimized by ant colony optimization

The rapid and accurate moisture content (MC) measuring of withering tea leaves faces multiple challenges. In this study, a self-developed microwave sensing system equipped with multifrequency-swept signals (2.00–10.00 GHz, an interval of 10.00 MHz) was used to measure the MC of withering tea leaves (16.25%–77.65%). Four kinds of hybrid-based ant colony optimizations were advanced to optimize microwave frequency signals, and the attenuation features at six frequencies (2.16, 3.42, 3.88, 4.48, 5.32 and 7.70 GHz) and phase shift features at four frequencies (2.84, 4.04, 7.88 and 8.43 GHz) were selected. Based on those optimized features, three primary models (support vector regression, extreme gradient boosting, and multi-layer perception) and one secondary model (decision tree) presented the best MC values (the average of mean absolute error was 0.349). The results showed the potential application of microwave technology in the MC monitoring in tea processing industry. • A microwave sensing system was developed for moisture detection in tea withering. • A hybrid-based ACO algorithm was designed to optimize the frequency features. • Attenuation and phase shift features correlated with MC were selected by MRACO. • The best MC detection was achieved by the stacking model of SVR, LGBM, and MLP.

Microwave-Absorbing Catalysts in Catalytic Reactions of Biofuel Production

Catalytic reactions in producing biofuels often face issues such as low product yield, low selectivity to preferred products and serious environmental issues which leads to the exploration of green technologies. Microwave technology is one of the green technologies that is widely applied in the field such as medical, food, signal processing or navigation, and has been reviewed for its potential in the catalytic reactions for biofuel production. With the application of microwave technology, its unique heating mechanism consists of magnetic field energy and electric field energy that enables the selective heating of materials, allowing rapid reaction and enhancement of catalytic performance of catalysts. In general, this review has discussed on the fundamentals and mechanisms of microwave technology with an in-depth discussion on the application of microwave-absorbing catalysts for biofuel production, especially in ammonia synthesis, bio-oil and 5-HMF production as well as methanation. Lastly, the challenges and future prospect of microwave-absorbing catalysts are included as well.

Polarization-dependent zero-plasma-permittivity, zero-permittivity, and zero-permeability gaps in a 1D photonic crystal composed of lossy double-negative and magnetic cold plasma materials

Theoretically, we have employed a transfer matrix to examine the tunable band structure and transmission properties of a one-dimensional photonic crystal that consists of periodic layers of a lossy double-negative index and magnetic cold plasma materials. Our study shows that the existence of unconventional photonic bandgaps (PBGs) is due to the material dispersion properties of double-negative and magnetic cold plasma layers and fundamentally differs from Bragg gaps, which arise due to an interference mechanism. The two new gaps, called zero-permittivity ( ε = 0 ) and zero-permeability ( μ = 0 ), near the frequency at which the permittivity and permeability of double-negative material change signs, have been found for non-zero incidence angles corresponding to p and s polarizations, respectively. These gaps can be easily tuned as well as enlarged by the application of an external magnetic field in both right-hand and left-hand polarization configurations. At a fixed magnetic field, ε = 0 and μ = 0 gaps corresponding to p and s polarizations, respectively, can be further enhanced by increasing the angle of incidence to higher values. Additionally, we have found a tunable zero-plasma-permittivity ( ε P = 0 ) gap close to the frequency at which the magnetic-field-dependent electric permittivity of a cold plasma layer changes sign at a non-zero incident angle corresponding to p polarization only. Finally, we present a way by which the zero-effective-phase gap, ε = 0 gap, and ε P = 0 gap can be joined together to produce an enlarged PBG at a non-zero incidence angle corresponding to p polarization only in the presence of an external magnetic field of value B L = 0.473 T . The proposed study may be used for designing of polarization triggered tunable optical devices in microwave engineering applications.

Immune Responses to Multi-Frequencies of 1.5 GHz and 4.3 GHz Microwave Exposure in Rats: Transcriptomic and Proteomic Analysis.

With the rapidly increasing application of microwave technologies, the anxiety and speculation about microwave induced potential health hazards has been attracting more and more attention. In our daily life, people are exposed to complex environments with multi-frequency microwaves, especially L band and C band microwaves, which are commonly used in communications. In this study, we exposed rats to 1.5 GHz (L10), 4.3 GHz (C10) or multi-frequency (LC10) microwaves at an average power density of 10 mW/cm2. Both single and multi-frequency microwaves induced slight pathological changes in the thymus and spleen. Additionally, the white blood cells (WBCs) and lymphocytes in peripheral blood were decreased at 6 h and 7 d after exposure, suggesting immune suppressive responses were induced. Among lymphocytes, the B lymphocytes were increased while the T lymphocytes were decreased at 7 d after exposure in the C10 and LC10 groups, but not in the L10 group. Moreover, multi-frequency microwaves regulated the B and T lymphocytes more strongly than the C band microwave. The results of transcriptomics and proteomics showed that both single and multi-frequency microwaves regulated numerous genes associated with immune regulation and cellular metabolism in peripheral blood and in the spleen. However, multi-frequency microwaves altered the expression of many more genes and proteins. Moreover, multi-frequency microwaves down-regulated T lymphocytes’ development, differentiation and activation-associated genes, while they up-regulated B lymphocytes’ activation-related genes. In conclusion, multi-frequency microwaves of 1.5 GHz and 4.3 GHz produced immune suppressive responses via regulating immune regulation and cellular metabolism-associated genes. Our findings provide meaningful information for exploring potential mechanisms underlying multi-frequency induced immune suppression.