In order to improve the quality of 3D printed raspberry preserves after post-processing,microwave ovens combining infrared and microwave methods were utilized.The effects of infrared heating temperature,infrared heati...In order to improve the quality of 3D printed raspberry preserves after post-processing,microwave ovens combining infrared and microwave methods were utilized.The effects of infrared heating temperature,infrared heating time,microwave power,microwave heating time on the center temperature,moisture content,the chroma(C*),the total color difference(ΔE*),shape fidelity,hardness,and the total anthocyanin content of 3D printed raspberry preserves were analyzed by response surface method(RSM).The results showed that under combining with the two methods,infrared heating improved the fidelity and quality degradation of printed products,while microwave heating enhanced the efficiency of infrared heating.Infrared-microwave combination cooking could maintain relatively stable color appearance and shape of 3D printed raspberry preserves.The AHP–CRITIC hybrid weighting method combined with the response surface test to determine the comprehensive weights of the evaluation indicators optimized the process parameters,and the optimal process parameters were obtained:infrared heating temperature of 190℃,infrared heating time of 10 min and 30 s,microwave power of 300 W,and microwave heating time of 2 min and 6 s.The 3D printed raspberry cooking methods obtained under the optimal conditions seldom had color variation,porous structure,uniform texture,and high shape fidelity,which retained the characteristics of personalized manufacturing by 3D printing.This study could provide a reference for the postprocessing and quality control of 3D cooking methods.展开更多
A microwave-H202 process for sludge pretreatment exhibited high efticiencies of releasing organics, nitrogen, and phosphorus, but large quantifies of H202 residues were detected. A uniform design method was thus emplo...A microwave-H202 process for sludge pretreatment exhibited high efticiencies of releasing organics, nitrogen, and phosphorus, but large quantifies of H202 residues were detected. A uniform design method was thus employed in this study to further optimize H202 dosage by investigating effects of pH and H202 dosage on the amount of 1-I202 residue and releases of organics, nitrogen, and phosphorus. A regression model was established with pH and H202 dosage as the independent variables, and H202 residue and releases of organics, nitrogen, and phosphorus as the dependent variables. In the optimized microwave-H202 process, the pH value of the sludge was firstly adjusted to 11.0, then the sludge was heated to 80~C and H202 was dosed at a H202 ：mixed liquor suspended solids （MLSS） ratio of 0.2, and the sludge was finally heated to 100~C by microwave irradiation. Compared to the microwave-H202 process without optimization, the H202 dosage and the utilization rate of H202 in the optimized microwave-H202 process were reduced by 80% and greatly improved by 3.87 times, respectively, when the H202：MLSS dosage ratio was decreased from 1.0 to 0.2, resulting in nearly the same release rate of soluble chemical oxygen demand in the microwave-H202 process without optimization at H202：MLSS ratio of 0.5.展开更多
Monodisperse spherical SiO2 particles were successfully synthesized in 2-propanol-H2O-NH3 system by the microwave hydrothermal method using ammonia as catalyst. To investigate the influences on the size of spherical S...Monodisperse spherical SiO2 particles were successfully synthesized in 2-propanol-H2O-NH3 system by the microwave hydrothermal method using ammonia as catalyst. To investigate the influences on the size of spherical SiO2 particles, factors such as ammonia concentration, reaction temperature, stirring intensity and reactants mol ratio have been studied. The orthogonal experiments were carried out. The as-prepared SiO2 particles were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, Fourier transform infrared spectroscopy （FTIR） and differential thermal analysis （DTA）. The results indicated that the size of SiO2 particles increased greatly with the increase in ammonia concentration, temperature and reactants mol ratio, but increased slightly with the increase in stirring intensity. Monodisperse spherical Si02 particles were amorphous with perfect sphere and uniform size. Hydroxyl was detected in SiO2. Kinetic parameters were calculated, and finally the reaction rate equation of dehydrated hydroxyl was obtained.展开更多
Novel red-emitting phosphors Sr2MgSi2O7：Eu3＋ were prepared by gel-combustion method assisted by microwave. The phase struc-ture and luminescent properties of as-synthesized phosphors were investigated by XRD and flu...Novel red-emitting phosphors Sr2MgSi2O7：Eu3＋ were prepared by gel-combustion method assisted by microwave. The phase struc-ture and luminescent properties of as-synthesized phosphors were investigated by XRD and fluorescence spectrophotometer, respectively. The results showed that the as-synthesized sample was Sr2MgSi2O7 with tetragonal crystal structure. The excitation spectrum of Sr2MgSi2O7：Eu3＋ was composed of two major parts： one was the broad band between 200 and 350 nm, which belonged to the charge transfer of Eu3＋-O2-; the other consisted of a series of sharp lines between 350 and 450 nm, ascribed to the f-f transition of Eu3＋. The emission spec-trum consisted of two emission peaks at 593 and 616 nm, which was attributed to 5D0→7F1 and 5D0→7F2 of Eu3＋, respectively. The concen-tration of Eu3＋ （x） had great effect on the emission intensity of Sr2-xMgSi2O7：Eu3＋x. When x varied in the range of 0.04-0.18, the intensity of emission peaks at 593 and 616 nm increased gradually with the concentration of Eu3＋ increasing. It was interesting that no concentration quenching occurred. Moreover, the luminescent intensity could be greatly enhanced with incorporation of charge compensator Li＋ ions.展开更多
Fe-based carbon materials are widely considered promising to replace Pt/C as next-generation electrocatalysts towards oxygen reduction reaction (ORR). However, the preparation of Fe-based carbon materials is still car...Fe-based carbon materials are widely considered promising to replace Pt/C as next-generation electrocatalysts towards oxygen reduction reaction (ORR). However, the preparation of Fe-based carbon materials is still carried out by conventional heating method (CHM). Herein, a novel microwave-assisted carbon bath method (MW-CBM) was proposed, which only took 35 min to synthesize Fe/Fe3C nanoparticles encapsulated in N-doped carbon layers derived from Prussian blue (PB). The catalyst contained large specific surface area and mesoporous structure, abundant Fe-Nx and C–N active sites, unique core-shell structure. Due to the synergistic effects of these features, the as-prepared Fe/Fe3C@NC-2 displayed outstanding ORR activity with onset potential of 0.98 VRHE and halfwave potential of 0.87 VRHE, which were more positive than 20 wt.% Pt/C (0.93 VRHE and 0.82 VRHE). Besides, Fe/Fe3C@NC-2 gave a better stability and methanol tolerance than Pt/C towards ORR in alkaline media, too.展开更多
A trust region method is proposed to solve the problem of microwave tomography,which is very difficult to be solved for its ill-posedness and nonlinearity. Compared with the Levenberg-Marquardt method, this method int...A trust region method is proposed to solve the problem of microwave tomography,which is very difficult to be solved for its ill-posedness and nonlinearity. Compared with the Levenberg-Marquardt method, this method introduces more a priori knowledge and might obtain better results, though the two methods are equal in some cases.展开更多
A passive and multi-channel microwave sounder onboard the Chang＇e-2 orbiter has successfully acquired microwave observations of the lunar surface and subsurface structure. Compared with the Chang＇e-1 orbiter, the Ch...A passive and multi-channel microwave sounder onboard the Chang＇e-2 orbiter has successfully acquired microwave observations of the lunar surface and subsurface structure. Compared with the Chang＇e-1 orbiter, the Chang＇e-2 orbiter obtained more accurate and comprehensive microwave brightness temperature data, which are helpful for further research. Since there is a close relationship between mi- crowave brightness temperature data and some related properties of the lunar regolith, such as the thickness, temperature and dielectric constant, precise and high resolution brightness temperature data are necessary for such research. However, through the detection mechanism of the microwave sounder, the brightness temperature data ac- quired from the microwave sounder are weighted by the antenna radiation pattern, so the data are the convolution of the antenna radiation pattern with the lunar brightness temperature. In order to obtain the real lunar brightness temperature, a deconvolution method is needed. The aim of this paper is to solve the problem associated with per- forming deconvolution of the lunar brightness temperature. In this study, we introduce the maximum entropy method （MEM） to process the brightness temperature data and achieve excellent results. The paper mainly includes the following aspects： first, we introduce the principle of the MEM; second, through a series of simulations, the MEM has been verified as an efficient deconvolution method; and third, the MEM is used to process the Chang＇e-2 microwave data and the results are significant.展开更多
Electromagnetic interference,which necessitates the rapid advancement of substances with exceptional capabilities for bsorbing electromagnetic waves,is of urgent concern in contemporary society.In this work,CoFe_(2)O_...Electromagnetic interference,which necessitates the rapid advancement of substances with exceptional capabilities for bsorbing electromagnetic waves,is of urgent concern in contemporary society.In this work,CoFe_(2)O_(4)/residual carbon from coal gasification fine slag(CFO/RC)composites were created using a novel hydrothermal method.Various mechanisms for microwave absorption,including conductive loss,natural resonance,interfacial dipole polarization,and magnetic flux loss,are involved in these composites.Consequently,compared with pure residual carbon materials,this composite offers superior capabilities in microwave absorption.At 7.76GHz,the CFO/RC-2 composite achieves an impressive minimum reflection loss(RL_(min))of-43.99 dB with a thickness of 2.44 mm.Moreover,CFO/RC-3 demonstrates an effective absorption bandwidth(EAB)of up to 4.16 GHz,accompanied by a thickness of 1.18mm.This study revealed the remarkable capability of the composite to diminish electromagnetic waves,providing a new generation method for microwave absorbing materials of superior quality.展开更多
This paper investigates a microwave heating method for the determination of chemical oxygen demand (COD) in seawater. The influences of microwave-power, heating time and standard substances on the results are studied....This paper investigates a microwave heating method for the determination of chemical oxygen demand (COD) in seawater. The influences of microwave-power, heating time and standard substances on the results are studied. Using the proposed method, we analyzed the glucose standard solution, the coefficient of variation being less than 2%. Compared with the traditional electric stove heating method, the results of F-test and T-test showed that there was no significant difference between the two methods, but the microwave method had slightly higher precision and reproducibility than the electric stove method. With the microwave heating method, several seawater samples from Jiaozhou Bay and the South Yellow Sea were also analyzed. The recovery was between 97.5% and 104.3%. This new method has the advantages of shortening the heating time, improving the working efficiency and having simple operation and therefore can be used to analyze the COD in seawater.展开更多
A Pt/graphene‐TiO2catalyst was prepared by a microwave‐assisted solvothermal method and was characterized by X‐ray diffraction,scanning electron microscopy,transmission electron microscopy,cyclic voltammetry,and li...A Pt/graphene‐TiO2catalyst was prepared by a microwave‐assisted solvothermal method and was characterized by X‐ray diffraction,scanning electron microscopy,transmission electron microscopy,cyclic voltammetry,and linear sweep voltammetry.The cubic TiO2particles were approximately60nm in size and were distributed on the graphene sheets.The Pt nanoparticles were uniformly distributed between the TiO2particles and the graphene sheet.The catalyst exhibited a significant improvement in activity and stability towards the oxygen reduction reaction compared with Pt/C,which resulted from the high electronic conductivity of graphene and strong metal‐support interactions.展开更多
As concepts closely related to microwave absorption properties,impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms.In this work,red...As concepts closely related to microwave absorption properties,impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms.In this work,reduction–diffusion method was innovatively applied to synthesize rare earth alloy Y_(2)Fe_(17).In order to regulate the electromagnetic parameters of absorbers,the Y_(2)Fe_(17)N_(3-δ)particles were coated with silica(Y_(2)Fe_(17)N_(3-δ)@SiO_(2))and absorbers with different volume fractions were prepared.The relationship between impedance matching,matching thickness,and the strongest reflection loss peak(RLmin)was presented obviously.Compared to the microwave absorption properties of Y_(2)Fe_(17)N_(3-δ)/PU absorber,Y_(2)Fe_(17)N_(3-δ)@SiO_(2)/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness,light weight,strong absorbing intensity,and broad bandwidth.Based on microwave frequency bands,the microwave absorption properties of the absorbers were analyzed and the related parameters were listed.As an important parameter related to perfect matching,reflection factor(√ε_(r)/μ_(r))was discussed combined with microwave amplitude attenuation.According to the origin and mathematical model of bandwidth,the formula of EAB(RL<-10 dB)was derived and simplified.The calculated bandwidths agreed well with experimental results.展开更多
Second harmonic generation(SHG),a fundamental and widely-studied phenomenon in nonlinear optics,has attracted significant attention for its ability to convert fundamental frequencies into their second harmonics.While ...Second harmonic generation(SHG),a fundamental and widely-studied phenomenon in nonlinear optics,has attracted significant attention for its ability to convert fundamental frequencies into their second harmonics.While the dominant SHG research has been focused on the optical and infrared regimes,its investigation in the microwave range presents challenges due to the requirements of materials with higher nonlinear coefficients and high-power microwave sources.Here,we provide an overview of methods together with underlying mechanisms for SHG in microwave frequencies,and discuss prospects and insights into the future developments of SHG-based technologies.The discussions on both numerical analyses and experimental studies will offer guidance for further SHG research and communication advancements in microwave regime.展开更多
SiC-Al2O3 composite powder was prepared by sol-gel and carbothermal reduction method. The powder synthesized was characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM) to confirm the phase forma...SiC-Al2O3 composite powder was prepared by sol-gel and carbothermal reduction method. The powder synthesized was characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM) to confirm the phase formation, and the thermodynamic analysis was performed systematically. Moreover, the variation of its microwave permittivity with different atomic ratio of Al/Si was investigated in the frequency range of 8.2-12.4 GHz. The results show that, the powder obtained consists of spherical particles of 300-400 nm in diameter, which are composed of SiC and Al2O3 microcrystal with the grain size of approximately 45 nm. The results of XRD accord with those of the thermodynamic analysis. It is impossible for Al atoms to dissolve in the lattice of SiC during the carbothermal reduction process. Along with the increase of atomic ratio of Al/Si in the xerogel, the amount of Al2O3 in the powder synthesized increases, which reduces bothε', the real part of complex permittivity, and tgδ(ε'/ε'), the dissipation factor, whereε' is the imaginary part of complex permittivity.展开更多
A new approach based on resonance technique and modified boundary ele-ment method is presented to calculate the impedance parameter matrix of a microwaveN-port network of waveguide structure.A two port network is take...A new approach based on resonance technique and modified boundary ele-ment method is presented to calculate the impedance parameter matrix of a microwaveN-port network of waveguide structure.A two port network is taken as a numerical ex-ample and the results show that the approach occupys the advantages of high accuracyand less computation effort.展开更多
In this research, cerium （III） nitrate hexahydrate （Ce（NO3）3·6H2O） and ammonium molybdate tetrahydrate （（NH4）6Mo7O24·4H2O） with Ce3＋-to-Mo6＋ molar ratio of 2：3 were dissolved in 40 ml different ...In this research, cerium （III） nitrate hexahydrate （Ce（NO3）3·6H2O） and ammonium molybdate tetrahydrate （（NH4）6Mo7O24·4H2O） with Ce3＋-to-Mo6＋ molar ratio of 2：3 were dissolved in 40 ml different solvents of deionized （DI） water, polyethylene glycol （PEG） and ethylene glycol （EG） to form different solutions which were followed by adjusting pH from the traditional values to 7.0 and 10.0 with 1 mol.L-1 sodium hydroxide （NaOH）. Subsequently, the solutions were processed by 270-W microwave-hydrother- mal/solvothermal method. Phase, morphology, vibrational modes and photonic properties were fully characterized by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, Fourier transform infrared spectroscopy （FTIR）, Raman spectrophotometry, ultraviolet-visible （UV-Vis） absorption and photoluminescence （PL） spectroscopy. The as-synthe-sized products were pure cerium molybdenum oxide （Ce2（MoO4）3） of nanoparticles clustered together as nano- plates in DI water and PEG solvents, and of spindle-like nanoparticles in EG solvent, including the presence of Ce-O-H mode and MoO4 units. The results show that direct energy gaps of the first two have the same value of 2.30 eV, and that of the last is 2.80 eV, including their blue emission at the same wavelength of 488 nm.展开更多
A simple and convenient method, free of template, has been proposed to synthesize hollow carambolashaped Ag2 S microspheres with Ag NO3, thiourea（TU）, Na Cl and diethanolamine as reagents using a microwave-assisted ...A simple and convenient method, free of template, has been proposed to synthesize hollow carambolashaped Ag2 S microspheres with Ag NO3, thiourea（TU）, Na Cl and diethanolamine as reagents using a microwave-assisted method, at low temperatures of below 100 ℃. Powder X-ray diffraction（XRD）,scanning electron microscopy（FESEM） and high resolution transmission electron microscopy（HRTEM）were employed to characterize the morphology and composition of those microspheres. The results indicated that the hollow carambola-shaped silver sulfide microspheres（with high purity and homogeneous morphology） were prepared by an Ostwald ripening process. A possible formation mechanism of hollow carambola-shaped Ag2 S microspheres was proposed.展开更多
Decoction of Kampo medicines plays an important role in clinical practice, especially in individualized treatment, while the inconvenience and a long time requirement of the decocting process are impediments to its wi...Decoction of Kampo medicines plays an important role in clinical practice, especially in individualized treatment, while the inconvenience and a long time requirement of the decocting process are impediments to its widespread use in Japan. In this study, we improved the decocting method by using a microwave oven such as those found in most kitchens. To validate the feasibility and safety of this new method, we decocted kakkonto, which is the most widely used formula in clinical treatment in Japan, and keishikabushito, which contains toxic components using a microwave oven. Regarding the contents of 8 characteristic components in the kakkonto decoction and the contents of 6 toxic components in the keishikabushito decoction as indices, and with the extraction and detoxification effects equal to those of the conventional decocting method as targets, we optimized the decocting conditions with Response Surface Methods. With this new method, it took 35 min to obtain almost the same extraction effect for kakkonto as with the conventional decocting method, which takes 40 min;meanwhile, it took only 45 min to detoxify keishikabushito, which takes 60 min using the conventional decocting method. Decocting Kampo medicines with a microwave oven is feasible and as safe as the conventional decocting method. It is a convenient, safe, time-saving method, and may be applied widely in clinical practice. This innovation should allow more patients to benefit from decoction and the individualized treatment it offers.展开更多
Abstract： Uniform Er3A15O12 spheres are of great value for fabricating optical ceramics. The highly monodisperse and size-controllable erbium aluminum garnet （EAG） precursors for transparent ceramics were successfu...Abstract： Uniform Er3A15O12 spheres are of great value for fabricating optical ceramics. The highly monodisperse and size-controllable erbium aluminum garnet （EAG） precursors for transparent ceramics were successfully synthesized through a new microwave process. The precursors constituted of ultrafine particles joining together by a hydroxyls formed compact network structure in the absence of SO42 , however, the morphologies of the precursors exhibited spheres with trace amount of SO42-. With manipulated programming of microwave irradiation parameters, narrow distributed particles of 40-50 nm were finally obtained by a separation of nu- cleation and nanocrystal growth. The mechanism behind the influence of microwave irradiation parameters on the growth of EAG precursors was preliminarily analysed. Easily dispersible and pure phase EAG were obtained at 950℃. The as-prepared EAG powders were used to fabricate transparent ceramics and transparent polycrystalline EAG ceramics were obtained under hydrogen furnace at 1750℃ for 8 h.展开更多
In this peper we have synthesized powder crystal form (Y,Gd) BO3:Eu(3+)Phosphors by microwave heating method. ItS structure belongs to hexagonal system with lattice parameters a=0.3796,c=0. 8835. Its excitation spetra...In this peper we have synthesized powder crystal form (Y,Gd) BO3:Eu(3+)Phosphors by microwave heating method. ItS structure belongs to hexagonal system with lattice parameters a=0.3796,c=0. 8835. Its excitation spetra peaks at 239.0nm and 240. 0nm monitored at the emission of 589nm and 612nm respectively, the half peak width is 40nm. Under 240nm excitation the phosphors show a strons oranse-red luminescence, the fluorescent intensity ratio for I589/I612 is 1.9/1展开更多
基金Supported by the National Natural Science Foundation of China(32072352)。
文摘In order to improve the quality of 3D printed raspberry preserves after post-processing,microwave ovens combining infrared and microwave methods were utilized.The effects of infrared heating temperature,infrared heating time,microwave power,microwave heating time on the center temperature,moisture content,the chroma(C*),the total color difference(ΔE*),shape fidelity,hardness,and the total anthocyanin content of 3D printed raspberry preserves were analyzed by response surface method(RSM).The results showed that under combining with the two methods,infrared heating improved the fidelity and quality degradation of printed products,while microwave heating enhanced the efficiency of infrared heating.Infrared-microwave combination cooking could maintain relatively stable color appearance and shape of 3D printed raspberry preserves.The AHP–CRITIC hybrid weighting method combined with the response surface test to determine the comprehensive weights of the evaluation indicators optimized the process parameters,and the optimal process parameters were obtained:infrared heating temperature of 190℃,infrared heating time of 10 min and 30 s,microwave power of 300 W,and microwave heating time of 2 min and 6 s.The 3D printed raspberry cooking methods obtained under the optimal conditions seldom had color variation,porous structure,uniform texture,and high shape fidelity,which retained the characteristics of personalized manufacturing by 3D printing.This study could provide a reference for the postprocessing and quality control of 3D cooking methods.
基金supported by the National Natural Science Foundation of China (No. 51008297)the Hi-Tech Research and Development Program (863) of China(No. 2007AA06Z347)the National Major Science & Technology Projects for Water Pollution Control and Management (No. 2012ZX07202-005)
文摘A microwave-H202 process for sludge pretreatment exhibited high efticiencies of releasing organics, nitrogen, and phosphorus, but large quantifies of H202 residues were detected. A uniform design method was thus employed in this study to further optimize H202 dosage by investigating effects of pH and H202 dosage on the amount of 1-I202 residue and releases of organics, nitrogen, and phosphorus. A regression model was established with pH and H202 dosage as the independent variables, and H202 residue and releases of organics, nitrogen, and phosphorus as the dependent variables. In the optimized microwave-H202 process, the pH value of the sludge was firstly adjusted to 11.0, then the sludge was heated to 80~C and H202 was dosed at a H202 ：mixed liquor suspended solids （MLSS） ratio of 0.2, and the sludge was finally heated to 100~C by microwave irradiation. Compared to the microwave-H202 process without optimization, the H202 dosage and the utilization rate of H202 in the optimized microwave-H202 process were reduced by 80% and greatly improved by 3.87 times, respectively, when the H202：MLSS dosage ratio was decreased from 1.0 to 0.2, resulting in nearly the same release rate of soluble chemical oxygen demand in the microwave-H202 process without optimization at H202：MLSS ratio of 0.5.
基金supported by the National Basic Research Program of China (Grant No.2007CB613603)
文摘Monodisperse spherical SiO2 particles were successfully synthesized in 2-propanol-H2O-NH3 system by the microwave hydrothermal method using ammonia as catalyst. To investigate the influences on the size of spherical SiO2 particles, factors such as ammonia concentration, reaction temperature, stirring intensity and reactants mol ratio have been studied. The orthogonal experiments were carried out. The as-prepared SiO2 particles were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, Fourier transform infrared spectroscopy （FTIR） and differential thermal analysis （DTA）. The results indicated that the size of SiO2 particles increased greatly with the increase in ammonia concentration, temperature and reactants mol ratio, but increased slightly with the increase in stirring intensity. Monodisperse spherical Si02 particles were amorphous with perfect sphere and uniform size. Hydroxyl was detected in SiO2. Kinetic parameters were calculated, and finally the reaction rate equation of dehydrated hydroxyl was obtained.
基金Project supported by the National Natural Science Foundation of China (20675023)
文摘Novel red-emitting phosphors Sr2MgSi2O7：Eu3＋ were prepared by gel-combustion method assisted by microwave. The phase struc-ture and luminescent properties of as-synthesized phosphors were investigated by XRD and fluorescence spectrophotometer, respectively. The results showed that the as-synthesized sample was Sr2MgSi2O7 with tetragonal crystal structure. The excitation spectrum of Sr2MgSi2O7：Eu3＋ was composed of two major parts： one was the broad band between 200 and 350 nm, which belonged to the charge transfer of Eu3＋-O2-; the other consisted of a series of sharp lines between 350 and 450 nm, ascribed to the f-f transition of Eu3＋. The emission spec-trum consisted of two emission peaks at 593 and 616 nm, which was attributed to 5D0→7F1 and 5D0→7F2 of Eu3＋, respectively. The concen-tration of Eu3＋ （x） had great effect on the emission intensity of Sr2-xMgSi2O7：Eu3＋x. When x varied in the range of 0.04-0.18, the intensity of emission peaks at 593 and 616 nm increased gradually with the concentration of Eu3＋ increasing. It was interesting that no concentration quenching occurred. Moreover, the luminescent intensity could be greatly enhanced with incorporation of charge compensator Li＋ ions.
基金supported by the National Natural Science Foundation of China (U1303291)the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT_15R46)
文摘Fe-based carbon materials are widely considered promising to replace Pt/C as next-generation electrocatalysts towards oxygen reduction reaction (ORR). However, the preparation of Fe-based carbon materials is still carried out by conventional heating method (CHM). Herein, a novel microwave-assisted carbon bath method (MW-CBM) was proposed, which only took 35 min to synthesize Fe/Fe3C nanoparticles encapsulated in N-doped carbon layers derived from Prussian blue (PB). The catalyst contained large specific surface area and mesoporous structure, abundant Fe-Nx and C–N active sites, unique core-shell structure. Due to the synergistic effects of these features, the as-prepared Fe/Fe3C@NC-2 displayed outstanding ORR activity with onset potential of 0.98 VRHE and halfwave potential of 0.87 VRHE, which were more positive than 20 wt.% Pt/C (0.93 VRHE and 0.82 VRHE). Besides, Fe/Fe3C@NC-2 gave a better stability and methanol tolerance than Pt/C towards ORR in alkaline media, too.
文摘A trust region method is proposed to solve the problem of microwave tomography,which is very difficult to be solved for its ill-posedness and nonlinearity. Compared with the Levenberg-Marquardt method, this method introduces more a priori knowledge and might obtain better results, though the two methods are equal in some cases.
基金Supported by the National Natural Science Foundation of China
文摘A passive and multi-channel microwave sounder onboard the Chang＇e-2 orbiter has successfully acquired microwave observations of the lunar surface and subsurface structure. Compared with the Chang＇e-1 orbiter, the Chang＇e-2 orbiter obtained more accurate and comprehensive microwave brightness temperature data, which are helpful for further research. Since there is a close relationship between mi- crowave brightness temperature data and some related properties of the lunar regolith, such as the thickness, temperature and dielectric constant, precise and high resolution brightness temperature data are necessary for such research. However, through the detection mechanism of the microwave sounder, the brightness temperature data ac- quired from the microwave sounder are weighted by the antenna radiation pattern, so the data are the convolution of the antenna radiation pattern with the lunar brightness temperature. In order to obtain the real lunar brightness temperature, a deconvolution method is needed. The aim of this paper is to solve the problem associated with per- forming deconvolution of the lunar brightness temperature. In this study, we introduce the maximum entropy method （MEM） to process the brightness temperature data and achieve excellent results. The paper mainly includes the following aspects： first, we introduce the principle of the MEM; second, through a series of simulations, the MEM has been verified as an efficient deconvolution method; and third, the MEM is used to process the Chang＇e-2 microwave data and the results are significant.
基金financially supported by the Key Project of Natural Science Research in Colleges and Universities of Anhui Province,China(No.2022AH050816)the Open Research Grant of Joint National-Local Engineering Research Centre for Safe and Precise Coal Mining(Nos.EC2023013 and EC2022018)+1 种基金the National Natural Science Foundation of China(No.52200139)the Introduction of Talent in Anhui University of Science and Technology,China(Nos.2021yjrc18 and 2023yjrc79)。
文摘Electromagnetic interference,which necessitates the rapid advancement of substances with exceptional capabilities for bsorbing electromagnetic waves,is of urgent concern in contemporary society.In this work,CoFe_(2)O_(4)/residual carbon from coal gasification fine slag(CFO/RC)composites were created using a novel hydrothermal method.Various mechanisms for microwave absorption,including conductive loss,natural resonance,interfacial dipole polarization,and magnetic flux loss,are involved in these composites.Consequently,compared with pure residual carbon materials,this composite offers superior capabilities in microwave absorption.At 7.76GHz,the CFO/RC-2 composite achieves an impressive minimum reflection loss(RL_(min))of-43.99 dB with a thickness of 2.44 mm.Moreover,CFO/RC-3 demonstrates an effective absorption bandwidth(EAB)of up to 4.16 GHz,accompanied by a thickness of 1.18mm.This study revealed the remarkable capability of the composite to diminish electromagnetic waves,providing a new generation method for microwave absorbing materials of superior quality.
文摘This paper investigates a microwave heating method for the determination of chemical oxygen demand (COD) in seawater. The influences of microwave-power, heating time and standard substances on the results are studied. Using the proposed method, we analyzed the glucose standard solution, the coefficient of variation being less than 2%. Compared with the traditional electric stove heating method, the results of F-test and T-test showed that there was no significant difference between the two methods, but the microwave method had slightly higher precision and reproducibility than the electric stove method. With the microwave heating method, several seawater samples from Jiaozhou Bay and the South Yellow Sea were also analyzed. The recovery was between 97.5% and 104.3%. This new method has the advantages of shortening the heating time, improving the working efficiency and having simple operation and therefore can be used to analyze the COD in seawater.
基金supported by the National Natural Science Foundation of China(21376113)the Jiangsu Specially Appointed Professor Projectthe Graduate Student Scientific Research Innovation Projects in Jiangsu Province(KYZZ15_0384)~~
文摘A Pt/graphene‐TiO2catalyst was prepared by a microwave‐assisted solvothermal method and was characterized by X‐ray diffraction,scanning electron microscopy,transmission electron microscopy,cyclic voltammetry,and linear sweep voltammetry.The cubic TiO2particles were approximately60nm in size and were distributed on the graphene sheets.The Pt nanoparticles were uniformly distributed between the TiO2particles and the graphene sheet.The catalyst exhibited a significant improvement in activity and stability towards the oxygen reduction reaction compared with Pt/C,which resulted from the high electronic conductivity of graphene and strong metal‐support interactions.
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFB3501300)the National Natural Science Foundation of China(Grant No.51731001)the Fund from the State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization’s Key Research and Development Projects。
文摘As concepts closely related to microwave absorption properties,impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms.In this work,reduction–diffusion method was innovatively applied to synthesize rare earth alloy Y_(2)Fe_(17).In order to regulate the electromagnetic parameters of absorbers,the Y_(2)Fe_(17)N_(3-δ)particles were coated with silica(Y_(2)Fe_(17)N_(3-δ)@SiO_(2))and absorbers with different volume fractions were prepared.The relationship between impedance matching,matching thickness,and the strongest reflection loss peak(RLmin)was presented obviously.Compared to the microwave absorption properties of Y_(2)Fe_(17)N_(3-δ)/PU absorber,Y_(2)Fe_(17)N_(3-δ)@SiO_(2)/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness,light weight,strong absorbing intensity,and broad bandwidth.Based on microwave frequency bands,the microwave absorption properties of the absorbers were analyzed and the related parameters were listed.As an important parameter related to perfect matching,reflection factor(√ε_(r)/μ_(r))was discussed combined with microwave amplitude attenuation.According to the origin and mathematical model of bandwidth,the formula of EAB(RL<-10 dB)was derived and simplified.The calculated bandwidths agreed well with experimental results.
基金supported by the National Natural Science Foun-dation of China(No.12274339).
文摘Second harmonic generation(SHG),a fundamental and widely-studied phenomenon in nonlinear optics,has attracted significant attention for its ability to convert fundamental frequencies into their second harmonics.While the dominant SHG research has been focused on the optical and infrared regimes,its investigation in the microwave range presents challenges due to the requirements of materials with higher nonlinear coefficients and high-power microwave sources.Here,we provide an overview of methods together with underlying mechanisms for SHG in microwave frequencies,and discuss prospects and insights into the future developments of SHG-based technologies.The discussions on both numerical analyses and experimental studies will offer guidance for further SHG research and communication advancements in microwave regime.
基金Project (50572090) supported by the National Natural Science Foundation of China
文摘SiC-Al2O3 composite powder was prepared by sol-gel and carbothermal reduction method. The powder synthesized was characterized by X-ray diffraction(XRD) and scanning electron microscopy(SEM) to confirm the phase formation, and the thermodynamic analysis was performed systematically. Moreover, the variation of its microwave permittivity with different atomic ratio of Al/Si was investigated in the frequency range of 8.2-12.4 GHz. The results show that, the powder obtained consists of spherical particles of 300-400 nm in diameter, which are composed of SiC and Al2O3 microcrystal with the grain size of approximately 45 nm. The results of XRD accord with those of the thermodynamic analysis. It is impossible for Al atoms to dissolve in the lattice of SiC during the carbothermal reduction process. Along with the increase of atomic ratio of Al/Si in the xerogel, the amount of Al2O3 in the powder synthesized increases, which reduces bothε', the real part of complex permittivity, and tgδ(ε'/ε'), the dissipation factor, whereε' is the imaginary part of complex permittivity.
文摘A new approach based on resonance technique and modified boundary ele-ment method is presented to calculate the impedance parameter matrix of a microwaveN-port network of waveguide structure.A two port network is taken as a numerical ex-ample and the results show that the approach occupys the advantages of high accuracyand less computation effort.
基金financially supported by Thailand's Office of the Higher Education Commission through the National Research University Project for Chiang Mai University
文摘In this research, cerium （III） nitrate hexahydrate （Ce（NO3）3·6H2O） and ammonium molybdate tetrahydrate （（NH4）6Mo7O24·4H2O） with Ce3＋-to-Mo6＋ molar ratio of 2：3 were dissolved in 40 ml different solvents of deionized （DI） water, polyethylene glycol （PEG） and ethylene glycol （EG） to form different solutions which were followed by adjusting pH from the traditional values to 7.0 and 10.0 with 1 mol.L-1 sodium hydroxide （NaOH）. Subsequently, the solutions were processed by 270-W microwave-hydrother- mal/solvothermal method. Phase, morphology, vibrational modes and photonic properties were fully characterized by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, Fourier transform infrared spectroscopy （FTIR）, Raman spectrophotometry, ultraviolet-visible （UV-Vis） absorption and photoluminescence （PL） spectroscopy. The as-synthe-sized products were pure cerium molybdenum oxide （Ce2（MoO4）3） of nanoparticles clustered together as nano- plates in DI water and PEG solvents, and of spindle-like nanoparticles in EG solvent, including the presence of Ce-O-H mode and MoO4 units. The results show that direct energy gaps of the first two have the same value of 2.30 eV, and that of the last is 2.80 eV, including their blue emission at the same wavelength of 488 nm.
基金supported by the Fundamental Research Funds for the Central Universities(No.2232013A3-05)the National Science and Technology Ministry(No.ID 2012BAK30B03)
文摘A simple and convenient method, free of template, has been proposed to synthesize hollow carambolashaped Ag2 S microspheres with Ag NO3, thiourea（TU）, Na Cl and diethanolamine as reagents using a microwave-assisted method, at low temperatures of below 100 ℃. Powder X-ray diffraction（XRD）,scanning electron microscopy（FESEM） and high resolution transmission electron microscopy（HRTEM）were employed to characterize the morphology and composition of those microspheres. The results indicated that the hollow carambola-shaped silver sulfide microspheres（with high purity and homogeneous morphology） were prepared by an Ostwald ripening process. A possible formation mechanism of hollow carambola-shaped Ag2 S microspheres was proposed.
文摘Decoction of Kampo medicines plays an important role in clinical practice, especially in individualized treatment, while the inconvenience and a long time requirement of the decocting process are impediments to its widespread use in Japan. In this study, we improved the decocting method by using a microwave oven such as those found in most kitchens. To validate the feasibility and safety of this new method, we decocted kakkonto, which is the most widely used formula in clinical treatment in Japan, and keishikabushito, which contains toxic components using a microwave oven. Regarding the contents of 8 characteristic components in the kakkonto decoction and the contents of 6 toxic components in the keishikabushito decoction as indices, and with the extraction and detoxification effects equal to those of the conventional decocting method as targets, we optimized the decocting conditions with Response Surface Methods. With this new method, it took 35 min to obtain almost the same extraction effect for kakkonto as with the conventional decocting method, which takes 40 min;meanwhile, it took only 45 min to detoxify keishikabushito, which takes 60 min using the conventional decocting method. Decocting Kampo medicines with a microwave oven is feasible and as safe as the conventional decocting method. It is a convenient, safe, time-saving method, and may be applied widely in clinical practice. This innovation should allow more patients to benefit from decoction and the individualized treatment it offers.
基金supported by Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Abstract： Uniform Er3A15O12 spheres are of great value for fabricating optical ceramics. The highly monodisperse and size-controllable erbium aluminum garnet （EAG） precursors for transparent ceramics were successfully synthesized through a new microwave process. The precursors constituted of ultrafine particles joining together by a hydroxyls formed compact network structure in the absence of SO42 , however, the morphologies of the precursors exhibited spheres with trace amount of SO42-. With manipulated programming of microwave irradiation parameters, narrow distributed particles of 40-50 nm were finally obtained by a separation of nu- cleation and nanocrystal growth. The mechanism behind the influence of microwave irradiation parameters on the growth of EAG precursors was preliminarily analysed. Easily dispersible and pure phase EAG were obtained at 950℃. The as-prepared EAG powders were used to fabricate transparent ceramics and transparent polycrystalline EAG ceramics were obtained under hydrogen furnace at 1750℃ for 8 h.
文摘In this peper we have synthesized powder crystal form (Y,Gd) BO3:Eu(3+)Phosphors by microwave heating method. ItS structure belongs to hexagonal system with lattice parameters a=0.3796,c=0. 8835. Its excitation spetra peaks at 239.0nm and 240. 0nm monitored at the emission of 589nm and 612nm respectively, the half peak width is 40nm. Under 240nm excitation the phosphors show a strons oranse-red luminescence, the fluorescent intensity ratio for I589/I612 is 1.9/1
