Search

Biomass pyrolysis is the most effective process to convert abundant organic matter into value-added products that could be an alternative to depleting fossil fuels. A comprehensive understanding of the biomass pyrolysis is essential in designing the experiments. However, pyrolysis is a complex process dependent on multiple feedstock characteristics, such as biomass consisting of volatile matter, moisture content, fixed carbon, and ash content, all of which can influence yield formation. On top of that, product composition can also be affected by the particle size, shape, susceptors used, and pre-treatment conditions of the feedstock. Compared to conventional pyrolysis, microwave-assisted pyrolysis (MAP) is a novel thermochemical process that improves internal heat transfer. MAP experiments complicate the operation due to additional governing factors (i.e. operating parameters) such as heating rate, temperature, and microwave power. In most instances, a single parameter or the interaction of parameters, i.e. the influence of other parameter integration, plays a crucial role in pyrolysis. Although various studies on a few operating parameters or feedstock characteristics have been discussed in the literature, a comprehensive review still needs to be provided. Consequently, this review paper deconstructed biomass and its sources, including microwave-assisted pyrolysis, and discussed the impact of operating parameters and biomass properties on pyrolysis products. This paper addresses the challenge of handling multivariate problems in MAP and delivers solutions by application of the machine learning technique to minimise experimental effort. Techno-economic analysis of the biomass pyrolysis process and suggestions for future research are also discussed. [ABSTRACT FROM AUTHOR]

The plasma emission spectrum and polycrystalline diamond growth within 4 inches was studied by using a microwave plasma chemical vapor deposition (MPCVD) equipment with a microwave frequency of 2.45 GHz and a power of 10 kW, a 4-inch free-standing diamond thick film was prepared, and the growth uniformity, crystal quality at different positions, room temperature thermal conductivity, ultraviolet-visible-near infrared spectral transmittance and dielectric properties of diamond film were characterized. The results show that the freestanding diamond films are prepared with good uniformity and crystallinity at 10 kW power with high concentration and chemical activity of carbon and hydrogen active particles within the plasma diameter of about 100 mm. The thermal conductivity at room temperature reaches more than 1894 W/m·K, the infrared transmittance reaches more than 70%, the dielectric constant is 5.5, and the dielectric loss is 5.9 × 10−5. This study provides a theoretical possibility for the preparation of large-area high-quality diamond films in low-power MPCVD equipment.

Oil fuels derived from fossils are non-renewable, so over time, they will run out and have a negative impact on air pollution. To overcome this, there is a need for environmentally friendly alternative fuels from renewable sources such as biodiesel. This research used microwave heating with a CaO catalyst. NaOH-impregnated snail shells and active carbon support. This research aims to determine the effect of power on the conversion of candlenut seed oil into biodiesel using the NaOH/CaO/CA catalyst both in terms of compliance with the SNI 7182-2015 standard and analysis using GC-MS (Gas Chromatography-Mass Spectrometry). The synthesis of the NaOH/CaO/CA catalyst was carried out through wet impregnation and calcination at a temperature of 500°C and analyzed using gas sorption analysis (GSA). Then proceed to the transesterification process, where the power for microwave heating was varied to 300, 450, and 600 watts with a mole ratio of esterified oil and methanol, namely 1:10 for 3 minutes. The analysis results of the NaOH/CaO/CA catalyst using the GSA instrument have a surface area of 9.306 m2/g, pore volume of 0.033 cc/g, and pore diameter of 14.043 nm. Meanwhile, the results of the biodiesel analysis showed that the optimum biodiesel yield was 85.625% at 600 watts of power and had a kinematic density and viscosity that met the SNI 7182-2015 biodiesel standards. Analysis of biodiesel characteristics using GC-MS showed that the three most optimum biodiesel components were hexadecanoic acid, methyl ester (22.664%), 9,12-Octadedecadienoic acid (Z,Z)-, methyl ester (30.176%) and 9-Octadecenoic acid (Z)-, methyl ester (38.656%).

Oil fuels derived from fossils are non-renewable, so over time, they will run out and have a negative impact on air pollution. To overcome this, there is a need for environmentally friendly alternative fuels from renewable sources such as biodiesel. This research used microwave heating with a CaO catalyst. NaOHimpregnated snail shells and active carbon support. This research aims to determine the effect of power on the conversion of candlenut seed oil into biodiesel using the NaOH/CaO/CA catalyst both in terms of compliance with the SNI 7182-2015 standard and analysis using GC-MS (Gas Chromatography-Mass Spectrometry). The synthesis of the NaOH/CaO/CA catalyst was carried out through wet impregnation and calcination at a temperature of 500°C and analyzed using gas sorption analysis (GSA). Then proceed to the transesterification process, where the power for microwave heating was varied to 300, 450, and 600 watts with a mole ratio of esterified oil and methanol, namely 1:10 for 3 minutes. The analysis results of the NaOH/CaO/CA catalyst using the GSA instrument have a surface area of 9.306 m2/g, pore volume of 0.033 cc/g, and pore diameter of 14.043 nm. Meanwhile, the results of the biodiesel analysis showed that the optimum biodiesel yield was 85.625% at 600 watts of power and had a kinematic density and viscosity that met the SNI 7182-2015 biodiesel standards. Analysis of biodiesel characteristics using GC-MS showed that the three most optimum biodiesel components were hexadecanoic acid, methyl ester (22.664%), 9,12-Octadedecadienoic acid (Z,Z)-, methyl ester (30.176%) and 9-Octadecenoic acid (Z)-, methyl ester (38.656%). [ABSTRACT FROM AUTHOR]

In the world of industrial drying processes, foam mat microwave drying is a significant and valuable approach. Its advantages include increased drying effectiveness, preservation of product quality, energy and cost savings, flexibility in application, and improved safety. Development of Nagpur mandarin juice powder is tedious and time-consuming due to its bitter test and less total soluble solid, therefore the present research carried out with the process parameters for microwave drying include microwave power levels (180, 360, 540, 720, and 900 W) and drying bed thicknesses (2, 4, and 6 mm). Foamed juice is produced using soy protein isolate (2.10 %), GMS (2.75 %), CMC (1.75 %), and sugar (5.10 %), with whipping times of 8 min. Additional foaming agents include guar gum (0.45 %), soy protein isolate (3.30 %), and sugar (10 %) with whipping times of 6 min. The optimal conditions for drying Nagpur mandarin juice were determined through analysis using Design-Expert 11.0.4.1 software. These conditions include 540 W of microwave power, a drying bed thickness of 3 mm, and the use of a foaming agent comprising 2.10 % soy protein isolate, 2.75 % GMS, 1.75 % CMC, and 5.10 % sugar, with an 8-min whipping period. Under these optimized conditions, the resulting powder exhibited the following characteristics: color b value of 19.59, ΔE (change in color) of 6.24, acidity of 0.40 %, ascorbic acid content of 36.64 mg/100 g, water activity of 0.26, drying time (in minutes), and overall acceptability rating of 7.77. These findings highlight the effectiveness of the optimized process parameters in achieving desirable quality attributes for Nagpur mandarin juice powder production.

This study investigates the optimization of microwave-assisted extraction (MAE) condition for phenolic antioxidants from Gossampinus malabarica flowers by response surface methodology (RSM) using a central composite design (CCD). The best combinations of microwave power (MP), solid to liquid (S-L) ratio, ethanol concentration and time were identified through MAE using RSM from G. malabarica flowers. The manipulation of process variables significantly influenced the extraction of bioactive compounds (BCs), with the MP and S-L ratio demonstrating high significance in the extraction of BCs. The optimized extraction conditions consisted of an MP of 1,000 W, a S-L ratio of 1:100, an ethanol concentration of 20 % (w/v), and an extraction time of 20 s, resulting in the highest extraction yield, extractable phenolic compounds, DPPH antioxidant activity and total flavonoid content. The actual experimental results are closely associated with the predicted values, affirming the efficacy of RSM in optimizing the phenolic extraction process from G. malabarica flowers.

This article explores the optimization of microwave-assisted extraction (MAE) technology for the extraction of turmeric oil. The study used response surface methodology (RSM) to analyze the effects of process variables on the oil yield and quality. The results indicated that hexane was a more effective solvent compared to petroleum ether, and the optimal conditions for extraction were a microwave power of 300 watts and an extraction time of 20 minutes. The study concludes that MAE is a safe, efficient, and economically feasible method for turmeric oil extraction, with potential applications in various industries and medical science. [Extracted from the article]

Microwave-assisted freeze drying (MFD) is particularly suited for drying heat-sensitive materials. However, optimizing process parameters is time-consuming due to lengthy individual experiments. This study investigates the feasibility of partial MFD for parameter studies, with the process being terminated after removing 20 wt% of the water contained. The proposed approach reduces the time required for parameter evaluation by 92.0% compared to complete MFD. It also enables the evaluation of the samples' drying homogeneity. A subsequent parameter study based on partial MFD was then conducted to evaluate the effects of chamber pressure, microwave power, and microwave frequencies on the drying kinetics and drying homogeneity. Lowering the average chamber pressure from 0.87 mbar to 0.19 mbar reduced the process duration by 18.8%. An increase in the dissipated specific microwave power from 0.048 W/g to 0.143 W/g reduced the duration by 46.7%. The targeted application of frequencies increased the average energy efficiency to as high as 92.4%, contributing to a shortened process duration of up to 51.2%. Only the application of multiple frequencies caused a notable increase in drying homogeneity. In summary, this study demonstrates the feasibility and time-saving benefits of partial drying for parameter studies in MFD and potentially different types of drying processes. [ABSTRACT FROM AUTHOR]

The aim of this study is to use the response surface methodology (RSM) to mathematically model the response parameters and emission of greenhouse gases (GHG) and optimize the drying variables for a carrot dried with the microwave method using various pretreatments. To this end, the influence of the drying parameters (independent), such as microwave power and slice thickness dried by two pretreatments of ultrasonication at 30 °C for 10 min and blanching at 70 ℃ for 2 min, was explored on the dependent (response) parameters including the thermal properties (drying time, effective moisture diffusion coefficient (Deff), specific energy consumption, energy efficiency, quality features (color changes and shrinkage), and GHG emission (including CO2 and NOx). It should be mentioned that the emission of GHG was determined based on the energy consumption of various types of power plants such as the gas turbine steam power turbine, and combined cycle turbines using various fuels such as natural gas, heavy oil, and gas oil. The results indicated that the ultrasonication and blanching pretreatments can decrement the drying time (linearly), energy consumption (linearly or quadratically), shrinkage(quadratically), and color changes(quadratically) and enhance the Deff (linearly) and energy efficiency (linearly or quadratically) in all samples with R2 > 0.86. Moreover, the shortest drying time (42 min), lowest SEC (9.51 MJ/kg), and GHG emission ((4279.74 g CO2 in the combined cycle turbines plant, and 18.16 g NOX in the gas turbine plant) with natural gas for both plants) were recorded for the samples pretreated with blanching while the lowest color changes (13.69) and shrinkage (21.29) were observed in the ultrasonicated samples. Based on the optimization results, a microwave power of 300 W and steam power turbine of 2 mm were the best variables with a desirability of about 80% which resulted in the highest-quality products at the lowest GHG emission. [ABSTRACT FROM AUTHOR]

Biomass is a promising resource for the production of renewable energy, liquid fuels, and chemicals. Microwave pyrolysis is one of the directions of multifunctional conversion of raw materials. In the present work, the effect of microwave power on the characteristics of sawdust pyrolysis is studied. With an increase in power, the maximum yield of combustible gases increased, and a large proportion of the total pyrolysis time included the useful time for the release of gases. An increase in power affected the yield of individual gases non-linearly and on a different scale. The average yield of CO and CO2 remained practically unchanged when the microwave power was increased from 840 to 1760 W. However, with a further increase in power to 2200 W, there was a significant increase in the average yield of CO and CO2 (2.5 and 1.4 times, respectively). An increase in power by 2.6 times contributed to an increase in the average yield of CH4 by 5 times and H2 by 3.8 times. The increased power of microwaves contributed to the degassing of wood and intensification of secondary pyrolysis reactions, which resulted in a decrease in the mass of the solid residue by 5.3 times and a decrease in the liquid product yield by 2.7 times. A comprehensive analysis using MCDA showed that an increase in energy costs with an increase in microwave power is integrally compensated by an improvement in pyrolysis performance. So, when the power was varied from 840 W to 2200 W, the pyrolysis efficiency indicator increased by 1.3–2.2 times, considering the growth in energy consumption. [ABSTRACT FROM AUTHOR]

In this study, it was aimed to bring the bone broth-based sauce into powder form by microwave assisted hot air drying method and to determine the drying characteristics of this product. Bone broth-based sauces were dried at the drying temperatures of 60, 70 and 80 °C, and at the microwave powers of 90, 180 and 360 W, until a moisture content of 10% (dry basis). The moisture ratio (MR) was significantly influenced by the drying temperature and microwave power. Ten kinetic models were selected to evaluate MR data, with regard to adjusted regression coefficient (R2), the reduced chi-square (χ2) and root mean square error (RMSE). Midilli and Page models exhibited a better fit for the drying kinetics of bone broth-based sauce than the other drying models tested. In addition, the effective moisture diffusivity (Deff) and activation energy (Ea) values were 1.27 × 10−7 m2/s and 27 kJ/mol, respectively. Consequently, these results can be used to simulate the microwave assisted hot air drying of bone broth-based sauce and improve the efficiency of the drying process. [ABSTRACT FROM AUTHOR]

The study investigated the effects of different microwave vacuum freeze-drying powers (100–500 W) on the emulsifying properties and structural characteristics of egg white protein, which is of great significance in enhancing the added value of EWP and promoting its application. Emulsification analysis revealed that the emulsification performance was significantly influenced by microwave power and reached its maximum at 300 W. Fourier-transform infrared spectroscopy (FT-IR) and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) analyses showed that microwave vacuum freeze-drying treatment altered the secondary structure of EWP without changing its peptide structure. Fluorescence measurements indicated that the maximum fluorescence emission intensity decreased, and the maximum emission wavelength shifted towards blue as the power increased. Particle size, zeta potential, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) analyses showed that the average particle size of EWP reached the minimum value of 1203.66 nm, the absolute value of zeta potential reached the maximum value of 41.35 mV, and the thermal stability was strongest, with a more uniform and loose structure observed at 300 W. Texture profile analysis (TPA) showed that appropriate power treatment significantly enhanced the chewiness and viscoelasticity of egg white protein. Therefore, appropriate power treatment could effectively improve the emulsifying properties and stability. [ABSTRACT FROM AUTHOR]

Discovery of the capacity of microwave energy to heat materials was a major milestone in the history of technology and scientific research. This discovery led to the development of many devices and processes that have replaced conventional heating methods, thereby reducing reliance on fossil fuels and reducing atmospheric CO 2 emissions. Over the past two decades the use of microwave heating for processing of non-dielectric metals, metal powders alloys have increased markedly and includes sintering, melting, joining, cladding, drilling, and 3D printing. These developments have used a wide range of experimental procedures, and the use of microwave power has resulted in significant benefits over conventional heating methods. These benefits include a many-fold decreases in processing times and energy consumption, as well as improved microstructural characteristics and mechanical properties of the processed material. This review provides a comprehensive overview of the state-of-the-art of microwave processing of metals, metal powders and their alloys and focuses on important process parameters such as heating mechanisms, electromagnetic properties of metals, the factors affecting these parameters and applications to metal processing. Requirements for efficient metal processing using microwave power are presented including metal properties, microwave susceptors, insulators, ceramic containment structures and temperature measurement methods that all play roles in the development of microwave processing of metals and metal alloy materials. Current challenges and issues in equipment design parameters and various processing methods to facilitate commercial implementation of metal processing at larger scales are investigated. [Display omitted] • Microwave heating: a sustainable approach for processing metallic materials. • Understanding microwave heating and the factors influencing metal processing. • Evolution and growth of the microwave processing applications of metals. • Proposal of forty pairings of NW-MWSC with molten metals for MW processing tools. • Challenges and opportunities in microwave metal processing. [ABSTRACT FROM AUTHOR]

Power sensor nonlinearity contributes significantly to the increase of the microwave power measurement uncertainty. Current methods for sensor calibration do not provide correction of the results, due to the sensor nonlinearity. The paper describes an improved method and an automated measuring system based on it for power sensor calibration that enables the correction of the results, taking into account amplitude and frequency dependent nonlinearity. The novel calibration method is based on the application of high-linearity thermistor power transfer standard. The power sensor calibration process is fully automated and improved by applying the automated measuring system, PC and VEEpro software. Performed calculation of the calibration measurement uncertainty and the analysis of power measurement uncertainty budget indicate that the new calibration method allows the correction of sensor nonlinearity and contributes to significant reduction of the microwave power measurement uncertainty, ranging from 15,8% to 40,5%. Experimental results and validation confirm the applicability of the improved calibration method and prove the existence of significant dependence of sensor nonlinearity on the power level, but also on the frequency of the measured microwave power.

Basic aluminum sulfate desorption desulfurization, as a renewable desulfurizer and rich in high-purity SO2, had attracted extensive attention at home and abroad. In order to enhance the desorption performance, the effects of microwave power and desulfurization rich liquid flow on desorption performance were studied under the microwave dynamic desorption system. The results show that the dynamic desorption system operated stably and has good desorption effect under the continuous action of microwave. The desulfurization rich liquid can be stably maintained at the target desorption temperature in the desorption bottle, while a lower temperature level can be obtained in the desorption buffer bottle to eliminate the influence of thermal desorption. Under certain desulfurization rich liquid flow and microwave power, high microwave power and desulfurization rich liquid flow could significantly promote the desorption performance. The desorption ratio at the desorption end point reaches more than 72. 26% and 71. 64% and the desorption rate reaches more than 1. 874 5 × 10 - 4 mol / (L·min) and 2. 443 5 × 10 - 4 mol / (L·min). Under high microwave power, the heating rate, desorption ratio, and desorption rate are significantly improved, and the non-thermal effect of microwave desorption is more prominent. High desulfurization rich liquid flow increases the circulation ratio and prolongs the effective action time of microwave, which is beneficial to the improvement of desorption ratio and desorption rate. [ABSTRACT FROM AUTHOR]

The aim of this study is to use the response surface methodology (RSM) to mathematically model the response parameters and emission of greenhouse gases (GHG) and optimize the drying variables for a carrot dried with the microwave method using various pretreatments. To this end, the influence of the drying parameters (independent), such as microwave power and slice thickness dried by two pretreatments of ultrasonication at 30 °C for 10 min and blanching at 70 ℃ for 2 min, was explored on the dependent (response) parameters including the thermal properties (drying time, effective moisture diffusion coefficient (Deff), specific energy consumption, energy efficiency, quality features (color changes and shrinkage), and GHG emission (including CO2 and NOx). It should be mentioned that the emission of GHG was determined based on the energy consumption of various types of power plants such as the gas turbine steam power turbine, and combined cycle turbines using various fuels such as natural gas, heavy oil, and gas oil. The results indicated that the ultrasonication and blanching pretreatments can decrement the drying time (linearly), energy consumption (linearly or quadratically), shrinkage(quadratically), and color changes(quadratically) and enhance the Deff (linearly) and energy efficiency (linearly or quadratically) in all samples with R2 > 0.86. Moreover, the shortest drying time (42 min), lowest SEC (9.51 MJ/kg), and GHG emission ((4279.74 g CO2 in the combined cycle turbines plant, and 18.16 g NOX in the gas turbine plant) with natural gas for both plants) were recorded for the samples pretreated with blanching while the lowest color changes (13.69) and shrinkage (21.29) were observed in the ultrasonicated samples. Based on the optimization results, a microwave power of 300 W and steam power turbine of 2 mm were the best variables with a desirability of about 80% which resulted in the highest-quality products at the lowest GHG emission.

Biomass is a promising resource for the production of renewable energy, liquid fuels, and chemicals. Microwave pyrolysis is one of the directions of multifunctional conversion of raw materials. In the present work, the effect of microwave power on the characteristics of sawdust pyrolysis is studied. With an increase in power, the maximum yield of combustible gases increased, and a large proportion of the total pyrolysis time included the useful time for the release of gases. An increase in power affected the yield of individual gases non-linearly and on a different scale. The average yield of CO and CO2 remained practically unchanged when the microwave power was increased from 840 to 1760 W. However, with a further increase in power to 2200 W, there was a significant increase in the average yield of CO and CO2 (2.5 and 1.4 times, respectively). An increase in power by 2.6 times contributed to an increase in the average yield of CH4 by 5 times and H2 by 3.8 times. The increased power of microwaves contributed to the degassing of wood and intensification of secondary pyrolysis reactions, which resulted in a decrease in the mass of the solid residue by 5.3 times and a decrease in the liquid product yield by 2.7 times. A comprehensive analysis using MCDA showed that an increase in energy costs with an increase in microwave power is integrally compensated by an improvement in pyrolysis performance. So, when the power was varied from 840 W to 2200 W, the pyrolysis efficiency indicator increased by 1.3–2.2 times, considering the growth in energy consumption.

Microwave curing technology has been widely used in resin and its composite materials. In order to study its effect for curing unsaturated polyester resin (UPR) composites containing calcium carbonate (CaCO3) filler, this paper first investigated the influence of microwave power and microwave irradiation time on the curing characteristics of UPR. Then, CaCO3 particles were added to the UPR to investigate the microwave curing effect of the UPR composites containing the CaCO3. The results showed that microwave irradiation could heat the UPR sample evenly, and rapidly cause the chain growth reaction, thus greatly shortening the curing time. The curing degree and products of the samples after microwave curing were consistent with that of the thermal curing. The addition of CaCO3 particles could increase the heating rate of the UPR composites, which would accelerate the curing rate of the UPR. However, higher microwave power could lead to pore defects inside the UPR composites with higher CaCO3 content, resulting in a lower strength. Thus, the compactness of the samples should be improved by reducing the microwave power and prolonging the microwave treatment time. [ABSTRACT FROM AUTHOR]

The optimum hole diameter of a ring reflector was experimentally investigated using an axial virtual cathode oscillator (vircator) to enhance its microwave power. The ring reflector enhances the microwave power from the axial vircator by forming a cavity. The ring reflector was installed 9 mm behind the anode. The optimum hole diameter of the ring reflector was analyzed through simulations and experiments by changing the diameter from 60 mm to 160. PIC simulations show that the maximum peak microwave power was generated when the hole diameter was 116 mm and enhanced by 210%. The experiments show similar results to the simulations. The largest peak maximum power was 23.67 MW when the hole diameter was 120 mm. The simulations show that the dominant microwave frequency was formed between 5.33 GHz and 6.7 GHz. The experiments show that the dominant microwave frequency was formed between 5.3 GHz and 5.8 GHz. The frequency trend was approximately similar to that of the simulation results. However, the trend depending on the hole diameter was not as obvious as in the simulations. Although the frequency change was not as clear as in the simulations, experiments show that the hole diameter of the ring reflector affects the vircator operation. [ABSTRACT FROM AUTHOR]

The study investigated the effects of different microwave vacuum freeze-drying powers (100–500 W) on the emulsifying properties and structural characteristics of egg white protein, which is of great significance in enhancing the added value of EWP and promoting its application. Emulsification analysis revealed that the emulsification performance was significantly influenced by microwave power and reached its maximum at 300 W. Fourier-transform infrared spectroscopy (FT-IR) and sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) analyses showed that microwave vacuum freeze-drying treatment altered the secondary structure of EWP without changing its peptide structure. Fluorescence measurements indicated that the maximum fluorescence emission intensity decreased, and the maximum emission wavelength shifted towards blue as the power increased. Particle size, zeta potential, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) analyses showed that the average particle size of EWP reached the minimum value of 1203.66 nm, the absolute value of zeta potential reached the maximum value of 41.35 mV, and the thermal stability was strongest, with a more uniform and loose structure observed at 300 W. Texture profile analysis (TPA) showed that appropriate power treatment significantly enhanced the chewiness and viscoelasticity of egg white protein. Therefore, appropriate power treatment could effectively improve the emulsifying properties and stability.

High-quality diamond prepared by microwave plasma chemical vapor deposition (MPCVD) has application prospects in many high-precision fields. The film deposition experiments were carried out using microwave power 9 kW. The chamber pressures are 13 kPa, 14 kPa, 15. 5 kPa, and 17 kPa, respectively. It was found that the deposited films under pressure of 15. 5 kPa and 17 kPa exhibit abnormal growth in the central region, which is manifested as an obvious stepped bulge in the center. Surface morphology and film quality of the film were analyzed by SEM and Raman in order to reveal the reason for the abnormal deposition in the center of the film. Meanwhile, the deposition process was modeled, the power density and flow field distribution were calculated and analyzed by numerical simulation. The results show that at the same power, increasing the chamber pressure and compressing the plasma will lead to more dense growth in the central region of the film than that in the edge region and obvious steps in the central region of the diamond film, due to the short mean free path and insufficient diffusion capacity. The overall growth rate, uniformity and quality of the film will decrease after exceeding pressure limit. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Northwest A & F University - Natural Science Edition is the property of Editorial Department of Journal of Northwest A&F University (Natural Science Edition) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In contrast to conventional casting, casting using in situ microwave route is an advanced and promising technique of bulk metal casting wherein bulk metal is heated and melted in microwave radiations at 2.45 GHz. In this present work, AA-6063 is used as a charge material at three microwave powers of 600 W, 750 W and 900 W. The process uses three susceptor materials—stone charcoal, wood charcoal and SiC—and solidification is done at two levels as closed and open cavity. The optimization of the process parameters has been done through Taguchi technique. Microstructure and microindentation hardness studies of the developed casts divulged that smaller equiaxed grains could be obtained in densely cast samples 15 and 9. In these cast samples, the presence of intermetallic phases of Al2Mg3, MgZn2, Mg2Si, Al2Mg was observed; however, the cast sample 18 contains intermetallic phases of Al2Mg, MgZn and Al2Mg3. It was found from this work that the grain structure and intermetallic precipitates in the developed cast depend primarily on solidification environment, microwave power and susceptors. Microindentation hardness of the cast sample 18 in the present study was about 166 HV that is higher than the other developed casts. The characterization of developed casts in terms of microstructure, elemental analysis, porosity, XRD and fractography is analyzed. The results reveal that the rapid solidification and increased microwave power alter elemental composition, distribution and size of eutectic phases resulting in increase in the microindentation hardness. [ABSTRACT FROM AUTHOR]

Bu çalışmada, baharatlanmış hindi dilimleri farklı sıcaklıklarda (60 ve 70°C) ve mikrodalga güçlerinde (sabit ürün ağırlığında 0, 180 ve 360 W) kurutulmuş ve bu kurutulmuş dilimlerin fiziksel, kimyasal, mikrobiyolojik ve duyusal kalite karakteristikleri belirlenmiştir. Bu koşullarda kurutulmuş hindi dilimlerinin ortalama nem içeriği %25, aw değeri 0.72, pH değeri 6.02 ve tiyobarbitürik asit reaktif maddeleri (TBARS) değeri 15.77 µmol MDA/kg idi. Örneklerin kesilme kuvveti değerinin, sıcaklık artışına bağlı olarak 56.14 N'ye, mikrodalga gücündeki artışa bağlı olarak 59.12 N'ye yükseldiği tespit edilmiştir. Ayrıca, mikrodalga gücü arttıkça örneklerin L* değerinin önemli düzeyde (p < 0.01) azaldığı bulunmuştur. Buna ilaveten, mikrobiyal kalite 70°C kurutma sıcaklığı ve 360 W mikrodalga gücü uygulanan örneklerde daha iyi olmuştur. [ABSTRACT FROM AUTHOR]

The aim of present work was mainly to study the influence of blanching-freezing pre-treatment on moisture removal characteristics of potato during microwave drying process. The influence of microwave power and the samples thickness was also assessed. For this purpose, microwave powers of 100, 350 and 550 W were practiced to dry discoid shape samples of fresh and blanched-frozen potatoes with a constant diameter of 20 mm and different thicknesses of 5, 10 and 15 mm. The obtained results revealed that time required to dehydrate treated potatoes was significantly (P < 0.05) shorter than the fresh ones. The moisture diffusivity of the fresh and blanched-frozen potatoes was determined to be in the range of 9.13 × 10−9‒7.93 × 10−8 and 9.89 × 10−9‒9.36 × 10−8 m2 s−1, respectively where enhanced with the both increasing power level and samples thickness. The average energy required to instigate water diffusion inside the treated samples with 5, 10 and 15 mm thickness was obtained to be 0.463, 0.379 and 0.331 W g−1, respectively while the values for fresh samples were 0.505, 0.466 and 0.413 W g−1, respectively. [ABSTRACT FROM AUTHOR]

Bi-metallic nanoparticles (NPs) have appeared to be more efficient as antimicrobials than mono-metallic NPs. The fungus Aspergillus terreus-mediated synthesis of bi-metallic Ag-Cu NPs was optimized using response surface methodology (RSM) to reach the maximum yield of NPs. The optimal conditions were validated using ANOVA. The optimal conditions were 1.5 mM total metal (Ag + Cu) concentration, 1.25 mg fungal biomass, 350 W microwave power, and 15 min reaction time. The structure and shape of the synthesized NPs (mostly 20–30 nm) were characterized using several analytical tools. The biological activities of the synthesized NPs were assessed by studying their antioxidant, antibacterial, and cytotoxic activity in different NP concentrations. A dose-dependent response was observed in each test. Bi-metallic Ag-Cu NPs inhibited three clinically relevant human pathogens: Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomonas aeruginosa. Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus were inhibited less. The DPPH and hydrogen peroxide scavenging activities of the NPs were high, reaching 90% scavenging. Ag-Cu NPs could be studied as antimicrobials in different applications. The optimization procedure using statistical analyses was successful in improving the yield of nanoparticles. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To reduce thermal processing hazards (TPHs), microwave baking has been extensively used in food thermal processing. In this study, the influence of microwave power and microwave time on the formation of TPHs and their precursors was explored in microwave-baked biscuits. The results indicated that the content of acrylamide, 5-hydroxymethylfurfural, methylglyoxal, and 3-deoxyglucosone increased linearly with the extension of microwave time (2, 2.5, and 3 min) and microwave power (440, 480, and 520 W). There was a significant correlation between the four TPHs. 3-Deoxyglucosone may directly or indirectly participate in the formation of the other three TPHs. The relationship between TPH levels with some heat-induced sensory characteristics was analyzed. The correlation between the sensory characteristics and the content of TPHs is L* > a* > hardness > Water activity (AW). The correlation coefficients between L* value and the four TPHs are −0.950, −0.891, −0.803, and −0.985. Furthermore, the content of TPHs produced by traditional baking and microwave baking under the same texture level was compared. Compared with traditional baking (190°C, 7 min), microwave baking at 440 W for 3 min successfully decrease methylglyoxal, 3-Deoxyglucosone, acrylamide, and 5-hydroxymethylfurfural content by 60.75, 30.19, 30.87, and 61.28%, respectively. Traditionally baked biscuits, which had a more obvious color, as characterized by lower L* value, larger a* and b* values, are more susceptible to the formation of TPHs. Therefore, microwave baking can reduce the generation of TPHs.

In this study, the drying kinetics and quality characteristics of microwave-assisted hot air dried beef chips were investigated. For this purpose, beef slices were treated with spice mixture (4 g/100 g beef) and then dried with 2 different air temperature (60 and 70 °C) and 3 different microwave power (0, 90 and 180 W at fixed product weight). Drying process was terminated when moisture content of samples went below 15% and then drying kinetics and quality characteristics of the beef chips were analyzed. Drying time of beef chips reduced due to the increase in the microwave power and temperature whereas Page model was the most suitable model for identifying drying kinetics. It was also noted that average moisture content of microwave-assisted hot air dried beef chips was 12.8% (dry basis), water activity (aw) value was 0.70, pH value was 5.8 and thiobarbituric acid reactive substances (TBARS) value was 30.48 µmol MDA/kg. It was further found that those beef chips that were dried at high temperature (70 °C) and microwave power (180 W) had darker color (higher a* value) and shorter, thicker and harder (high cutting force). Moreover, it was finally noted that such fast drying samples had better microbial and sensory quality. [ABSTRACT FROM AUTHOR]

The present work outlines the synthesis of prismatic shaped zinc oxide (ZnO) nanostructures through microwave combustion method using different microwave power (160, 320, 480, 640, and 800 W) using Zinc nitrate as a precursor and ethylene glycol as solvent. The structural characterization of the synthesized ZnO nanostructures has been accessed by X-ray diffraction study (XRD), Field emission scanning electron microscopy (FE–SEM), UV-Visible spectroscopy (UV-Vis), energy-dispersive analysis using X-rays (EDAX) and photoconductivity technique. The XRD and FE–SEM results confirmed that the crystal size and growth of ZnO nanostructures depended on the heating of microwave powers. EDAX shows the existence of Zn and O in the synthesized ZnO microstructures. The optical properties and band gap studies were undertaken by UV-Visible spectroscopy. I–V characterization study was performed to determine the electrical property of ZnO films. [ABSTRACT FROM AUTHOR]

Microwave curing technology has been widely used in resin and its composite materials. In order to study its effect for curing unsaturated polyester resin (UPR) composites containing calcium carbonate (CaCO3) filler, this paper first investigated the influence of microwave power and microwave irradiation time on the curing characteristics of UPR. Then, CaCO3 particles were added to the UPR to investigate the microwave curing effect of the UPR composites containing the CaCO3. The results showed that microwave irradiation could heat the UPR sample evenly, and rapidly cause the chain growth reaction, thus greatly shortening the curing time. The curing degree and products of the samples after microwave curing were consistent with that of the thermal curing. The addition of CaCO3 particles could increase the heating rate of the UPR composites, which would accelerate the curing rate of the UPR. However, higher microwave power could lead to pore defects inside the UPR composites with higher CaCO3 content, resulting in a lower strength. Thus, the compactness of the samples should be improved by reducing the microwave power and prolonging the microwave treatment time.

The present work deals mainly with dehydration characteristics of onion slices. Microwave power levels of 100, 350, 550 and 750 W was practiced to dry onion slices with thicknesses of 2.5, 5, 7.5 and 10 mm. The results showed that moisture diffusivity and specific energy consumption of the process increased with both increasing microwave power and the samples thickness, and ranged from 0.82 × 10−8 to 6.13 × 10−8 m2 s−1 and from 0.82 to 5.43 MJ kg−1water, respectively. The average activation energy varied in the range of 1.28–1.77. Furthermore, for simulation of drying process and to predict the moisture removal behavior of the samples, multi-layer feed-forward (MLF) artificial neural network (ANN) was employed. Practicing different networks and based on statistical parameters, the best topology, transfer functions and training algorithms were determined. The results revealed that, as a powerful tool, ANN modeling could be effectively used to predict drying kinetics and determine the moisture content of the samples. [ABSTRACT FROM AUTHOR]

Effects of microwave power on the sensory properties (taste and aroma), chemical composition (catechins, caffeine, crude protein, and amino acid), active composition (flavones, triterpene, polysaccharide, and ergosterol) and antioxidant properties (superoxide free radical and hydroxyl radical scavenging abilities, reducing power) of Ganoderma lucidum fermented sea-buckthorn tea were investigated. G. lucidum fermented sea-buckthorn tea was dehydrated using microwaves at three power settings: 125, 250, and 500. After microwave treatment, a statistically significant difference in the chemical composition, active composition and antioxidant capacity (p < 0.05) of teas dried at different power settings was found. These results indicate that 250 W microwave treatments could effectively release and activate active components, improving the antioxidant activity of fermented tea. [ABSTRACT FROM AUTHOR]

Innovative titania nanostructures were synthesized via efficient and prolific liquid phase deposition route and efficiently utilized for catalytic degradation of Eosin Y. The as-synthesized TiO2@ITO nanostructures were subjected to various characterization tactics that confirmed the efficacious fabrication of nanostructures. The minute size of particles around 5–6 nm having anatase crystalline phase and concrete like morphology was greatly revealed by atomic force microscopy, XRD, and SEM, respectively. The resulting nanoconcretes were employed for photocatalytic degradation of Eosin Y dye in aqueous medium. The effects of various experimental parameters such as the reducing agent concentration, sunlight, time, catalytic dose, and microwave power were investigated for the potential photocatalytic degradation. The proposed TiO2@ITO nanostructures showed potential photocatalytic efficiency then previously reported nanomaterial for degradation of toxic Eosin Y dye; it shows approximately 99.8% dye degraded within 50–60 s using only 100 μg of nanocatalyst under optimized conditions. Owing to minute size, topography and electron–hole pair abilities TiO2@ITO nanostructures suggest an exceptional icon at the commercial level for successful degradation of toxic pollutants. Graphical abstract [ABSTRACT FROM AUTHOR]

In the world of industrial drying processes, foam mat microwave drying is a significant and valuable approach. Its advantages include increased drying effectiveness, preservation of product quality, energy and cost savings, flexibility in application, and improved safety. Development of Nagpur mandarin juice powder is tedious and time-consuming due to its bitter test and less total soluble solid, therefore the present research carried out with the process parameters for microwave drying include microwave power levels (180, 360, 540, 720, and 900 W) and drying bed thicknesses (2, 4, and 6 mm). Foamed juice is produced using soy protein isolate (2.10 %), GMS (2.75 %), CMC (1.75 %), and sugar (5.10 %), with whipping times of 8 min. Additional foaming agents include guar gum (0.45 %), soy protein isolate (3.30 %), and sugar (10 %) with whipping times of 6 min. The optimal conditions for drying Nagpur mandarin juice were determined through analysis using Design-Expert 11.0.4.1 software. These conditions include 540 W of microwave power, a drying bed thickness of 3 mm, and the use of a foaming agent comprising 2.10 % soy protein isolate, 2.75 % GMS, 1.75 % CMC, and 5.10 % sugar, with an 8-min whipping period. Under these optimized conditions, the resulting powder exhibited the following characteristics: color b value of 19.59, ΔE (change in color) of 6.24, acidity of 0.40 %, ascorbic acid content of 36.64 mg/100 g, water activity of 0.26, drying time (in minutes), and overall acceptability rating of 7.77. These findings highlight the effectiveness of the optimized process parameters in achieving desirable quality attributes for Nagpur mandarin juice powder production., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

In the present research, microwave drying process of potato slices were thermodynamically analyzed and evaluated. During the experiments, potato slices with thicknesses of 3.5, 5, 7 and 9 mm were dried using powers of 200, 400, 600 and 800 W. Specific energy consumption was obtained to be the range of 0.83‒3.29 MJ kg-1, and significantly increased (p < 0.05) with increasing samples thickness. Energy efficiency of the process (13.23‒35.59) was significantly (p < 0.05) improved with increasing microwave power and decreasing samples thickness. Average specific energy loss of the process varied from 0.69 to 2.71 MJ kg-1. Exergy efficiency and sustainability index of the process changed from 10.03 to 28.17 % and from 1.11 to 1.39, respectively. In General, according to the results obtained in this research, practicing higher microwave powers to dry thinner samples improved the thermodynamical performance and reduced the environmental footprints of the process. [ABSTRACT FROM AUTHOR]

Bi-metallic nanoparticles (NPs) have appeared to be more efficient as antimicrobials than mono-metallic NPs. The fungus Aspergillus terreus-mediated synthesis of bi-metallic Ag-Cu NPs was optimized using response surface methodology (RSM) to reach the maximum yield of NPs. The optimal conditions were validated using ANOVA. The optimal conditions were 1.5 mM total metal (Ag + Cu) concentration, 1.25 mg fungal biomass, 350 W microwave power, and 15 min reaction time. The structure and shape of the synthesized NPs (mostly 20–30 nm) were characterized using several analytical tools. The biological activities of the synthesized NPs were assessed by studying their antioxidant, antibacterial, and cytotoxic activity in different NP concentrations. A dose-dependent response was observed in each test. Bi-metallic Ag-Cu NPs inhibited three clinically relevant human pathogens: Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomonas aeruginosa. Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus were inhibited less. The DPPH and hydrogen peroxide scavenging activities of the NPs were high, reaching 90% scavenging. Ag-Cu NPs could be studied as antimicrobials in different applications. The optimization procedure using statistical analyses was successful in improving the yield of nanoparticles.

For homogeneous microwave heating in a microwave cavity with multiple 2.45 GHz microwave generators, power‐controlled phase‐shifting mode is proposed in this Letter. The proposed microwave heating system consists of a multimode microwave cavity in which dielectric materials are placed to be heated, four phase‐shifting WR‐340 waveguides for different phase excitation, four 1 kW magnetrons that produce microwave power at 2.45 GHz, and a power supply with a system controller for the magnetron output power controls. Using the proposed power‐controlled phase‐shifting mode, uniform heating distribution is achieved by reducing the hot and cold spots in the microwave cavity. The proposed experiments demonstrated that in comparison to a conventional mode with simultaneous multiple inputs, the proposed mode can achieve an improved heating uniformity of ∼64.4%.

The flower‐like and hexagonal flake‐like ZnO microstructures were synthesised by a microwave method using ammonia water and sodium hydroxide as precipitant, respectively. The products were characterised by scanning electron microscopy, high‐resolution transmission electron microscopy, X‐ray diffraction and photoluminescence. The photocatalytic activity of the flower‐like and hexagonal flake‐like ZnO microstructures was evaluated by the degradation of methyl orange (MO) under ultraviolet (UV) light irradiation. The results indicated that the best flower‐like ZnO microstructure was obtained when the experimental conditions were [Zn2+] = 0.025 mol l−1, [Zn2+]:[NH3·H2O] = 1:1.5, microwave power = 231 W. Under the same reaction conditions, hexagonal flake‐like ZnO can be obtained by using sodium hydroxide as precipitant. The MO in aqueous solution was completely eliminated by flower‐like ZnO after 120 min of UV light irradiation. Under identical conditions, the degradation of MO in aqueous solution was completely finished within 150 min in the presence of hexagonal flake‐like ZnO. The flower‐like ZnO sample showed an enhanced photocatalytic activity compared with the hexagonal flake‐like ZnO for the MO degradation, which could be attributed to the presence of more active centres and hence can have more opportunities to contact with MO molecules. [ABSTRACT FROM AUTHOR]

Pilot studies were performed on the identification of drying conditions in the microwave field leading to the obtaining of dry biomass with humidity in the range of 5… 8%, starting from initial humidity of 14… 20%. Sets of tests were performed with biomass sample masses of 5 and 10 kg for which the applied microwave power was varied, recording: variation of drying time with microwave power, average value of the final moisture in the sawdust (7.075, 60.6%) and variation of power density with drying time. The existence of the direct relationship between the applied power density and the drying time allows the optimization of energy consumption. Thus, one can choose the amount of biomass to be dried at a target humidity, while setting the equipment at the appropriate power of the process. [ABSTRACT FROM AUTHOR]

Advancement in the field of biomass and bioenergy has pulled in researchers to produce biofuels derived from naturally accessible feedstock by adopting diverse innovative approaches in biomass pretreatment. In this study, pyrolysis of micro algae with downstream processing of biomass from the resonator cavity under atmospheric pressure was conducted and hydrogen production produced under different microwave power was analyzed. With the increase in microwave power, the hydrogen gas yield accounted to be as twice as that at lower power, where the concentration of produced hydrogen accounts for about 30.80%, 33.20%, and 37.58% at microwave power levels of 800, 900 and 1000 W. It was also observed that no methane was produced in this study since most of the methane produced from microwave plasma conversion has reacted with CO 2 and produced CO and H 2 , hence dropped in the concentration of CO 2 with decline in power intensity. • Biomass was fed with downstream processing from resonator cavity. • Increase in Microwave power increases the yield of Hydrogen. • Concentration of CO 2 dropped as the power decreases. • Organic compound present contains mainly cellulose and the sum of H 2 , CO 2 and CO. [ABSTRACT FROM AUTHOR]

In this paper, a new design of microstrip power limiter which is based on microstrip technology and zero bias Schottky diode is introduced. In this context, the FR‐4 substrate that was characterized by dielectric permittivity (4.4), dielectric thickness (1.6 mm), and the HSMS 286k Schottky diode is used to design the proposed power limiter. The planar resonators are designed, optimized, and simulated with the shunting of the HSMS 286k diodes by using Schematic solver integrated in ADS from Agilent Technologies. The simulation results are significant in terms of high impedance matching, strong insertion of the low power, and good limitation ratio of the high power. The proposed power limiter is fabricated and tested in the measurement part. It is observed that the results are in agreement with the numerical analysis in terms of matching, isolation, and power limitation. The achieved microwave power limiter offers simple construction, small size (44 × 40 mm2), wide bandwidth, and good limitation ratio less than 10 dBm when the input power reaches 30 dBm. [ABSTRACT FROM AUTHOR]

The relativistic magnetron is one of the most attractive high‐power microwave sources, due to its compactness with high efficiency. It can generate hundreds of megawatts of microwave power in the L‐ and S‐bands. However, the efficiency of the magnetron is often limited due to the mode stability. In this Letter, three‐dimensional particle‐in‐cell simulation suggests even further increase of total efficiency of the magnetron can be realised via mode stabilisation using a self‐excited extended interaction in a collector region. A six‐vaned radial relativistic magnetron with a single radial output port powered by 400 kV, <10 kA electron beam with a 70 ns pulse demonstrates >900 MW with an efficiency of ∼48%. This improvement is attributed to the mode locking of operating π‐mode by a power‐boosted TE315 mode excited in the extended cavity. [ABSTRACT FROM AUTHOR]

• Solid recovered fuel has a poor public perception and its use is declining. • To improve its quality, use, and perception, better quality test methods are needed. • There were no significant differences in sample transportation temperature. • 5 g samples were found to be more appropriate for ash content analysis. • Minimum acid digestion conditions were 600 W, 10 min of reaction time at 180 °C. Management of solid recovered fuel (SRF) in South Korea is unique from most other countries in that it is based on a single standard. All SRFs are distributed at the same price irrespective of their performance, resulting in utilization problems and a low degree of acceptance among consumers. Moreover, the difficulty of temperature maintenance during transportation, excessive ash content, and the use of inappropriate microwave acid digestion methods pose challenges to SRF reliability. To address these issues, we compared the relevant management statuses in South Korea with those of the international community and reviewed the effects of the transportation temperature, ash content, and microwave acid digestion technique. The moisture, ash, sulfur, and chlorine contents as well as the lower heating values (LHVs) of all the samples from South Korea were found to be below the standard [international] thresholds, and they were barely influenced by the transportation temperature. In addition, 5 g samples were found to be more appropriate for ash content analysis than the 20 g samples used in South Korea, with the former producing smaller standard deviations. The optimal microwave acid digestion conditions were also determined to be a reaction time with nitric acid of >10 min, temperature of 180 °C, and microwave power of 600 W. The results of this study highlight the need for revising the SRF test methods used in South Korea, to boost the market and enhance quality reliability. [ABSTRACT FROM AUTHOR]

The objective of this work was to study the dehydration of skim cheese through different methods, in particular by hot air, microwave and freeze-drying, in order to assess which of these methods would be more suitable for the development of a new product (cheese snack). For the three processes of dehydration, several temperatures, powers and times were used, respectively. The drying time was optimized to allow the water activity of the final product to be between 0.3 and 0.4. The color and texture of the product obtained by the three processes were evaluated, and the nutritional analysis (protein, lipids, ash) of the product dried by hot air at 52 ºC and by microwave at 750 W and 850 W was performed. The sensory analysis of the microwave dehydrated products was also carried out. The results obtained revealed that the temperature played a relevant role in the drying time and the hardness of the product. In the dehydration by microwave, the power of 850 W resulted in a lower drying time and a better color preservation, but in a high hardness of the samples. Among the three processes studied, the microwave drying was the fastest for the water removal from the cheese.