Effects Of Microwave Irradiation Time Research Articles

The Effect of Microwave Irradiation on the Synthesis of Graphene from Battery Waste on Capacitance Properties

Supercapacitor material is an alternative in energy storage. Supercapacitors are charge storage devices that have a high energy density, fast charge/discharge rates, long service life, wide operating temperature range, and are environmentally friendly. Graphene is a nanomaterial that can be used as a supercapacitor because it has high conductivity and a large surface area, but graphene can experience agglomeration so it can affect its capacitance properties. The microwave-assisted method can be used in the synthesis of graphene. Several microwave-based techniques are becoming more popular for producing graphene and altering it. Due to its quick, precise, uniform, and volumetric heating, microwave heating is a promising method for the thermochemical treatment and reduction of graphene oxide to graphene. This research aimed to examine the effect of microwave irradiation time on the capacitive properties of graphene synthesis as a supercapacitor. Graphene oxide (GO) can be reduced into graphene quickly and easily using microwave pulses lasting 15 to 30minutes to produce high-quality graphene fabrication. The characterization test was performed using UV-Vis, FTIR, SEM-EDX and cyclic voltammetry (CV). As a result, the optimum time is 25 minutes, and it showed an absorption peak at the 282 nm wavelength dan the CV analysis showed that the graphene has double capacitor properties with a specific capacitance of 140.7 F/g in 20 mV/s. Besides, the result of SEM indicated that graphene could be formed successfully. Its potential applications are also illustrated by emphasizing its usage as electrode material. Finally, its main challenges and prospects are considerably pointed out.

Effect of microwave irradiation time on structural and optical properties of ZnS nanoparticles

In this communication, we report the synthesis of ZnS nanoparticles by chemical precipitation of Zn2+ ions with S2- ions in aqueous solution. Freshly formed ZnS nanoparticles (NPs) in colloidal suspension were microwave irradiated for different time intervals in a domestic microwave oven. Effect of microwave irradiation (MWI) time on microstructure, surface morphology and optical properties of NPs are studied using various characterization tools. The structural analysis confirms the influence of MWI time on cubic and crystalline nature of the samples which are in good agreement with selected area electron diffraction (SAED) pattern. The size of the NPs increased with increase in time of MWI. The size increase is consistent with literature reports that microwave irradiation accelerates not only the nucleation but also crystal growth. The band gap of the material tends to decrease as a function of irradiation time. The role of MWI time on surface defect removing process is also explained in detail.

Ultra-Fast Growth of ZnO Nanorods on Cotton Fabrics and Their Self-Cleaning and Physiological Comfort Properties

The main aim of the present study was to investigate the effect of microwave irradiation time on the photocatalytic and physiological comfort characteristics of zinc-oxide-nanorod-coated cotton fabrics. An ultra-fast technique was employed to grow the zinc oxide nanorods on cotton fabrics using a microwave-assisted hydrothermal method. The axial (length) and lateral (diameter) growth of the zinc oxide nanorods was observed to increase with microwave irradiation time. The ZnO nanorods uniformly and entirely covered the cotton fibers. The surface morphology, topography and chemical characteristics of the ZnO nanorods were investigated by scanning electron microscopy (SEM), EDS analysis, X-ray diffraction (XRD), atomic force microscopy (AFM) and inductively coupled plasma-optical emission spectrometry (ICP-OES). The degradation of orange II dye under UV light irradiation was observed to assess photocatalytic self-cleaning and solution discoloration ability. The ZnO-nanorod-coated cotton fabrics exhibited excellent photocatalytic activity, as the stains of orange II dye disappeared predominantly within 4 h and the coated fabrics became almost white after 6 h. Analyses of thermal properties, water vapor permeability (WVP), air permeability and stiffness were also performed to investigate the physiological comfort of the ZnO-nanorod-coated fabrics. The thermal conductivity and thermal absorptivity were observed to increase with an increase in the size and density of the ZnO nanorods. Moreover, non-significant reductions in water vapor permeability and air permeability were observed with application of the ZnO nanorods. The stiffness of the ZnO-nanorod-coated cotton fabric increased due to the complete coverage of fibers by the uniform growth of the ZnO nanorods. The ZnO-nanorod-coated cotton fabrics also showed good washing durability and reusability.

Rapid synthesis of silver nanowires during the polyol-microwave method and COMSOL multiphysics simulation of electromagnetic heating

To date, various methods have been used to synthesize silver nanowires, but some require long reaction times. In this work, we synthesized widely used silver nanowires with high efficiency and with the least time and energy during the polyol-microwave method. Also, the effects of microwave irradiation time, silver nitrate concentration, and type of etching agent on the shape and size of nanostructures were investigated experimentally. In fact, the shape and production efficiency of silver nanowires were controlled and the optimal conditions were obtained at the microwave irradiation time of 210 s. The characterization of the silver nanowires showed that silver nanowires with an average diameter of 80 nm and an average length of 20 µm can be produced with high efficiency under optimal conditions. Finally, for the first time, in the microwave-based synthesis method, electromagnetic heating was studied and simulated with the help of the “finite element” method implemented by the COMSOL Multiphysics software. The results showed that with increasing time, the temperature increases, and as a result, the number density of glycolaldehyde reducing agents increases. This could also explain the fast growth of silver nanowires during this method.

Early-stage road property improvements of cold recycled asphalt emulsion mixture with microwave technology

Cold recycled asphalt emulsion mixture (CRAEM) is widely used in construction and building materials. However, it is necessary to improve road performance at an early curing age for quickly open traffic. In this work, early-stage road properties (at 3 or 7-day curing age) of CRAEM with different heat treatment method (room temperature treatment, oven treatment and microwave treatment) were investigated and compared. The morphology and demulsification behavior of CREAM were also investigated with environmental scanning electron microscope (ESEM) and optical microscopy. Back propagation (BP) neural networks were used to simulate indirect tensile strength (ITS) of CRAEM after microwave irradiation. The gray correlation analysis (GCA) was used to compare the effects of microwave irradiation time on early-stage road properties of CRAEM. The results show that mechanical property is improved due to microwave irradiation. BP neural network can accurately predict early-stage mechanical properties of CRAEM. Microwave radiation has a positive effect on improving the water stability of CRAEM, but the improvement on TSR of CREAM is limited. The linear model can predict dynamic stability of CRAEM under different microwave parameters. The crack resistance at low temperature by microwave radiation is limited. Microwave radiation not only accelerates cement hydration, but also promotes the demulsification of asphalt emulsion. Microwave radiation has the highest influence on rutting resistance at high temperature and ITS performance of CRAEM; while its effect on water stability and crack resistance at low temperature of CRAEM is relatively less.

Effect of Microwave Irradiation Time on Microwave-Assisted Weak Acid Protein Hydrolysis

Horse heart myoglobin (MYG) and bovine serum albumin (BSA) were hydrolyzed by microwave-assisted weak-acid hydrolysis for 10, 20, 30, 40, 50, and 60 min using 2% formic acid (FA) at 100°C. Generally, the number of identified peptides increased with increasing irradiation time, indicating that the duration of microwave irradiation is linked to the efficiency of hydrolysis. For MYG, irradiation for 60 min provided the highest number of identified peptides, the greatest sequence coverage values and the highest MASCOT score values among the investigated irradiation times. Irradiation of BSA for 50 min, however, yielded a greater number of peptides than irradiation for 60 min due to the generation of miscleaved peptides after microwave irradiation for 50min.

Cleaner conversion of bamboo into carbon fibre with favourable physicochemical and capacitive properties via microwave pyrolysis combining with solvent extraction and chemical impregnation

Bamboo was converted into carbon fibre using a novel approach combining microwave pyrolysis, solvent extraction, and chemical impregnation. The employment of solvent extraction and chemical impregnation transformed natural bamboo into bamboo fibre with yield of 64 wt% that comprised of 87 wt% cellulose, 4 wt% lignin and 9 wt% hemicellulose deemed desirable for conversion into carbon fibre. The subsequent use of microwave pyrolysis transformed the bamboo fibre to form carbon fibre; the effects of microwave irradiation time and microwave power (two key process parameters) on properties of carbon fibre were investigated. Microwave pyrolysis provides a rapid heating rate (30 °C/min) with relatively shorter process time (20 min) compared to that performed by conventional pyrolysis method, thus leading to a relatively lower electric consumption and providing a potentially cost-saving and energy-efficient approach to produce carbon fibre. The production and properties of carbon fibre produced were affected by irradiation time and microwave power. The carbon fibre obtained was detected to have high fixed carbon (80 wt%), carbon element (87%), high BET surface area (475 m2/g) and fibres in small diameter (≤1 μm). It also shows desirable features comprising low content of moisture (<6 wt%), inorganic elements of Na, K, S, Mg (≤5%) and ash (1 wt%), allowing the carbon fibre to have more active sites and making it a cleaner product rather than polluting the environment whereas a high ash content could lead to undesired catalytic reactions and emission of potentially hazardous metallic components present in the ash. Combined with the detection of positive capacitive behaviour, the carbon fibre shows great potential to be used as an electrode for energy storage application. The results disclose that microwave pyrolysis combining with solvent extraction and chemical impregnation can be a cleaner approach to transform bamboo into carbon fibre with favourable physicochemical and capacitive properties.

Microwave-assisted Synthesis of ZnO Nanoparticles Stabilized with Gum Arabic: Effect of Microwave Irradiation Time on ZnO Nanoparticles Size and Morphology

The conventional heating methods of nanoparticle synthesis regularly depend on the energy inputs from outer heat sources that resulted high energy intake and low reaction competences. In this paper ZnO nanoparticles stabilized with gum arabic are synthesized using precipitating method assisted by simple and cost effective microwave heating technique. The objective of this work is to investigate the effect of microwave irradiation time towards ZnO nanoparticles morphology and size. The effect of microwave irradiation time has been investigated at 2, 4, 6, and 10 minutes. Dynamic Light Scattering (DLS) was employed to measure the size of ZnO nanoparticles. Ultraviolet–Visible spectroscopy (UV-vis), Fourier-Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD) were used for the characterization of the ZnO nanoparticles. UV-vis absorption spectrum was found in the range of 350 nm indicating the absorption peak of ZnO nanoparticles. FTIR spectra showed peaks range from 424 to 475 cm–1 which indicating standard of Zn–O stretching. The presence of (100), (002), and (101) planes were apparent in the XRD result, indicating the crystalline phase of ZnO nanoparticles. The increase in the microwave irradiation time affected the processes of nucleation and crystal growth promoted larger ZnO nanoparticles size. Microwave irradiation time at 2 minutes was selected as the best microwave irradiation time for smallest ZnO nanoparticles averaging about 168 nm sizes based on DLS analysis.

Impact on optical, electrical and antibacterial response of microwave irradiated silver nanoparticles

Silve spectroscopy, Fourier transform infrared spectroscopy (FTIR), photoluminescence, Raman spectroscopy, X-ray powder diffraction (XRD), scanning and transmission electron microscopy (SEM–TEM), zeta potential and dynamic light scattering (DLS). The presence of surface plasmon resonance (SPR) band (416 nm) confirmed fabrication of AgNPs. The effect of microwave irradiation time showed that the size, shape and stability of AgNPs depend on increasing of peak intensity with increasing reaction time. FTIR spectrum confirmed the possible functional group in the product indicating presence of PVP. The enlargement in the size and agglomeration of nanoparticles were prevented by r nanoparticles (AgNPs) have been formulated using microwave irradiation from non-aqueous solution of silver nitrate (AgNO3) and poly (N-vinyl-2-pyrrolidone) (PVP) as a stabilizer. Ethanol has also been reacted like a reducer for microwave irradiation process which is quite rapid, homogeneous and efficient. The as synthesized AgNPs was further characterized by ultraviolet–Visible (UV–Vis)encapsulation of PVP during the reaction. XRD spectra illustrated that AgNPs are higher crystalline having face-centered cubic surface. The morphological analysis found that the AgNPs are homogeneous and spherical with the size of 18 ± 5 nm. The zeta potential measurement affirms the higher stability of AgNPs due to its negatively charged surface. The prepared AgNPs also exhibited electrical properties obeying the ohm’s law and significantly antimicrobial activities against Escherichia coli due to the small size.

A green and energy-saving microwave-based method to prepare magnetic carbon beads for catalytic wet peroxide oxidation

A green and energy-saving method was proposed to fabricate magnetic carbon (Fe@CS) beads (diameter: 0.5–1 mm) as Fenton-like catalyst and to simultaneously regenerate saturated activated carbon. Chitosan (CS) was used as the precursor of carbon, and tremendous heat produced during the regeneration of activated carbon by microwave irradiation (600 W) was utilized for carbonization within 2 min. The effects of microwave irradiation time and iron/CS mass ratio on Fe@CS were evaluated through various characterization methods, such as iron content, phase, microstructure, degree of graphitization, and associated Fenton-like catalytic activity. Fe3O4 and slight Fe(0) were the main iron species in Fe@CS beads. The microstructure of Fe@CS beads presented a hollow nanosphere structure and the Fe3O4 nanoparticles were uniformly embedded in the carbon layer. The Fe@CS/H2O2 Fenton-like system managed to efficiently degrade acid orange II even in a wide pH range of 3–9. Hydroxyl radical was proven by electron spin resonance spectroscopy as the dominant active species. The crystal or catalytic activity of Fe@CS hardly changed after five cycles. Moreover, the catalytic activity was enhanced after each cycle because the surface bound iron and increased iron leaching (<2 mg/L in first four cycles). The stability could be restored (decreased iron leaching) easily through a convenient regeneration process. In conclusion, this study proposed a novel and facile method for preparing reusable heterogeneous Fenton-like particle catalysts, providing valuable insights for the green, energy-saving and reusable applications of catalysts.

Nanostructured ternary metal chalcogenide-based binder-free electrodes for high energy density asymmetric supercapacitors

An essential way to enhance the energy density of a supercapacitor(SC) is to use high capacitance electrode materials via developing binder-free electrode with porous and hierarchical nanostructures. Herein, we demonstrated the use of copper antimony sulfide (Cu3SbS4) nanowires directly grown on Ni foam (using a microwave-irradiation process) as a binder-free positive electrode for SCs. The growth mechanism, effect of microwave irradiation time on the morphology and electrochemical properties of Cu3SbS4 on Ni foam were discussed in detail. The cyclic voltammetric studies (using three-electrode test) of Cu3SbS4/Ni-5 electrode showed the presence of Type-C battery-like charge-storage properties. The Cu3SbS4/Ni-5 electrode delivered a high specific capacity (835.24 mA h g−1) as obtained from the charge-discharge analysis (at a current density of 2.5 mA cm−2). Further, the device specific properties of the Cu3SbS4/Ni-5 positive electrode was examined via fabricating asymmetric supercapacitors (ASCs) using two different negative electrodes viz. (i) planar-graphene, and (ii) binder-free copper molybdenum sulfide anchored on Ni foam (Cu2MoS4/Ni) electrodes, respectively. The electrochemical analyses of the fabricated ASCs revealed that the Cu3SbS4/Ni-5║Cu2MoS4/Ni ASC possess almost 3.0-fold higher energy density compared to the Cu3SbS4/Ni-5║graphene ASC. The Cu3SbS4/Ni-5║Cu2MoS4/Ni ASC delivered a high specific device capacitance of 213.6 F g−1 with a remarkable energy density (58.15 Wh kg−1), maximum power density (6363.63 W kg−1), and better cycle-life. The use of two different binder-free electrodes in the Cu3SbS4/Ni-5║Cu2MoS4/Ni ASC results in their superior performance metrics over the reported ASCs, thus, highlighting their potential applications towards next-generation supercapacitors.

Effect of Microwave Irradiation Time on Structure, Morphology, and Supercapacitor Properties of Functionalized Graphene

To reveal the effects of microwave irradiation on the structure, morphology, and supercapacitor performance of p-phenylenediamine (PPD)-functionalized graphene materials (FG), FG was synthesized by using PPD as a functional modifier with the combination of hydrothermal reflux and microwave irradiation. The results showed that microwave irradiation could realize rapid reduction of functionalized graphene oxide (FGO). With increase of the irradiation time, the structural defects decreased while the sp2 plane domains increased. Moreover, the lamellae began to decompose into small aggregates. Before microwave irradiation treatment, FGO exhibited good supercapacitor performance with superior specific capacitance of 614.2 F g−1 at 0.5 A g−1. However, after microwave irradiation, the supercapacitor performance of FG got worse, and the configuration types of nitrogen atoms in the FG structure changed significantly. These results indicate that microwave irradiation is not conducive to improvement of the supercapacitor performance of FG.

RETRACTED: Microwave-assisted synthesis and characterization of WOx nanostructures for gas sensor application

Abstract Tungsten oxide (WO x ) nanoparticles were synthesized by a facile and eco-friendly microwave-assisted hydrothermal method without need for using any surfactant. A thorough investigation was performed in order to elucidate the effects of microwave irradiation time (10, 20 and 30 min) on the structural, morphological and optical properties of the as-prepared WO x . Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) of the samples revealed the presence of irregular nanosized particles containing some well-structured rod shape particles. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that these nanoparticles are crystallines with mean crystalline size of about 16 nm exhibiting both monoclinic and orthorhombic WO x crystal structures. The optical properties were investigated by using ultraviolet visible spectroscopy (UV-VIS) and photoluminescence (PL). A blue-shifted optical absorption spectrum with an enhanced defects emission was observed when it was compared to bulk spectrum of WO 3 . Thermal-aged WO x nanoparticles at mild temperature (350 °C) were also used to fabricate conductometric gas sensors Gas sensing tests showed excellent performance towards ethanol monitoring for each synthesized material. In particular, the highest sensitivity was obtained for the sensor based on WO x synthesized by 10 min irradiation time (S10). At the optimal operating temperature of 300 °C, the S10 sensor showed a response R a /R g = 8.5 towards 100 ppm ethanol with fast response time of 10 s, in addition to an excellent selectivity against common interfering gases.

SiO2 caped Fe3O4 nanostructures as an active heterogeneous catalyst for 4-nitrophenol reduction

A simple, economic and one pot synthetic protocol was followed to synthesize Fe3O4 nanostructures using partial oxidation co-precipitation method under aerobic conditions. After synthesis, the nanostructures were coated with tetraethyl orthosilicate for stabilization purpose. Later on, these nanostructures were characterized by fourier transformed infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, electron dispersive X-ray spectroscopy and atomic force microscopy to examine their size, shape and crystalline structure. The synthesized SiO2/Fe3O4 nanostructures with fine semi-spherical textures showed high heterogeneous catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol using sodium borohydride (NaBH4) under microwave radiations. The effect of Different parameters such as concentration of reducing agent (NaBH4), quantity of catalyst applied and the effect of microwave irradiation time was evaluated to obtain good results for 4-nitrophenol reduction. The 99.5% 4-nitrophenol reduction was achieved by using 100 µg of SiO2/Fe3O4 nanocatalyst in a short reaction time. Furthermore, the 4-nitrophenol reduction process utilizing SiO2/Fe3O4 nanostructures as catalyst was very economical and efficient in term of ease of synthesis, low raw materials expenditure and fast recovery/separation of the catalyst using external magnetic field. Besides these characteristics the SiO2/Fe3O4 nanocatalyst is environment-friendly and bio compatible due to its extremely low toxicity. Based on the above characteristics, the SiO2/Fe3O4 nanocatalyst can find some potential applications as heterogeneous catalyst in environmentally and industrially important reactions.

Improvement on slurry ability of lignite under microwave irradiation

Under 900W, the effects of microwave irradiation time on the solid concentration, rheology and static stability of lignite water slurry (LWS) were investigated. The results showed that with the gradual increase of microwave irradiation time the hydrated film on lignite became thinner and it contributed to the maximum solid concentration of lignite increased from 51.63% to 55.30% (irradiated for 12min). At the same time, the oxygen/carbon and hydrogen/carbon atomic ratios decreased, the moisture content and oxygen-containing functional groups gradually removed, and the lignite surface became smooth. The changes of these interfacial properties improved the pseudo-plasticity and reduced the yield stress of LWS. Besides, the changes in lignite surface caused larger dispersant adsorption on lignite surface and therefore enhanced the static stability of LWS.

Green Process for Extraction of Mangiferin from Mangifera indica Leaves

This work deals with the extraction of mangiferin from the Mangifera indica leaves using water as a solvent for the first time making it more economical than other extraction methods studied till date. The effect of various extraction methods like microwave assisted extraction, sequential batch extraction has been performed and optimized. Effect of microwave irradiation time, solute to solvent ratio, microwave power, and soaking time on the yield of targeted component was studied and optimized. The maximum extraction yield of 55 mg/g was obtained at optimum microwave assisted extraction conditions like water as an extracting solvent, extraction time 5 min, solid to solvent ratio 1:20 and microwave power of 272 W. The extraction yield obtained with microwave was compared with the sequential batch extraction and soxhlet extraction. It is found that microwave increased the yield of extraction in a short span of time and also reduced the solvent requirement as compared to the conventional methods.

Rapid Synthesis of Silver Nanoparticles by Microwave-Polyol Method with the Assistance of Latex Copolymer

Highly stable and monodispersed silver nanoparticles with uniform morphology have been successfully prepared by microwave (MW) irradiation within a few seconds from the mixture of silver nitrate, ethanol and latex copolymer. The aqueous emulsion of latex copolymer acts as both reducing and stabilizing agent. To the best of our knowledge, it was the first time that the effect of MW irradiation time and latex concentration on the silver nanoparticle preparation and properties was analyzed. The formation of silver nanoparticles was confirmed by Ultraviolet–visible spectroscopy and transmission electron microscopy (TEM). The UV–Vis spectra are marked by the characteristic surface plasmon absorption band in the range 410–420 nm. From TEM images, silver nanoparticles were observed to be spherical with sizes ranging from 4 to 10 nm. Electron diffraction patterns on selected area, indicated that the silver nanoparticles are crystalline with face centered cubic structure.

Microwave synthesis of pure and doped cerium (IV) oxide (CeO2) nanoparticles for methylene blue degradation.

Cerium (IV) oxide (CeO2), samarium (Sm) and gadolinium (Gd) doped CeO2 nanoparticles were prepared using microwave technique. The effect of microwave irradiation time, microwave power and pH of the starting solution on the structure and crystallite size were investigated. The prepared nanoparticles were characterized using X-ray diffraction, FT-Raman spectroscopy, and transmission electron microscope. The photocatalytic activity of the as-prepared CeO2, Sm and Gd doped CeO2 toward degradation of methylene blue (MB) dye was investigated under UV light irradiation. The effect of pH, the amount of catalyst and the dye concentration on the degradation extent were studied. The photocatalytic activity of CeO2 was kinetically enhanced by trivalent cation (Gd and Sm) doping. The results revealed that Gd doped CeO2 nanoparticles exhibit the best catalytic degradation activity on MB under UV irradiation. For clarifying the environmental safety of the by products produced from the degradation process, the pathways of MB degradation were followed using liquid chromatography/mass spectroscopy (LC/MS). The total organic carbon content measurements confirmed the results obtained by LC/MS. Compared to the same nanoparticles prepared by another method, it was found that Gd doped CeO2 prepared by hydrothermal process was able to mineralize MB dye completely under UV light irradiation.

Novel g-C3N4/Ag2SO4 nanocomposites: Fast microwave-assisted preparation and enhanced photocatalytic performance towards degradation of organic pollutants under visible light

Graphite carbon nitride (g-C3N4)/Ag2SO4 nanocomposites, as highly enhanced visible-light-driven photocatalysts, were prepared by a fast microwave-assisted method. The resulting g-C3N4/Ag2SO4 nanocomposites were characterized by X-ray diffraction, energy dispersive analysis of X-rays, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, Fourier transform-infrared spectroscopy, and ultraviolet–visible diffuse reflectance spectroscopy techniques. Moreover, charge separation efficiency was studied by photoluminescence measurements. Photocatalytic activity of the g-C3N4/Ag2SO4 (40%) nanocomposite in degradation of rhodamine B, methylene blue, and fuchsine is about 6, 3.8, and 3.3-folds greater than that of the g-C3N4 under visible-light illumination. Effect of microwave irradiation time, calcination temperature, and scavengers of the reactive species on the degradation reaction was also evaluated. The enhanced photocatalytic activity was mainly ascribed to the matching band energies of g-C3N4 and Ag2SO4 which leads to an improved separation of photogenerated electron-hole pairs. Finally, the optimized nanocomposite was recycled for five times without remarkable decrease of the photocatalytic activity.

Effect of microwave irradiation on the grinding characteristics of Ximeng lignite

The grinding characteristics of untreated and microwave-treated Ximeng lignites (XLs) were investigated, and the effects of microwave irradiation time, particle size range, and initial moisture were studied. The mass fraction and particle size distribution of the fine ground product with <0.154mm particle size range of untreated and microwave-treated XLs were obtained. According to the analysis results of proximate, scanning electron microscopy and nitrogen absorption, the dominant mechanisms that improved the grindability of XL with high moisture under microwave irradiation included the rapid removal of moisture within the XL and the destruction of the pore structure induced by the steam jet flow generated with moisture removal. Microwave irradiation could improve the grindability of XL with high moisture, thus increasing the breakage rate of microwave-treated XL and mass fraction of the fine ground product significantly. The particle size distributions of the fine ground products of untreated and microwave-treated XLs changed slightly. With increasing microwave irradiation time, initial moisture, and particle size range of XL, the increment in the grindability of microwave-treated XL increased. When XL was treated at low microwave power, the microwave irradiation time was extended properly to avoid the accumulation of moisture on the surface. Therefore, the grindability of microwave-treated XL improved significantly.