The preparation of microsized hematite powder from ferrous sulfate using microwave calcination was investigated based on the TG/DTG curves. The decomposition of industrial ferrous sulfate under air atmosphere was divi...The preparation of microsized hematite powder from ferrous sulfate using microwave calcination was investigated based on the TG/DTG curves. The decomposition of industrial ferrous sulfate under air atmosphere was divided into three stages, and a ferrous sulfate sample added with 15% Fe_2O_3 could strongly absorb microwave energy. Therefore, preparing hematite powder from ferrous sulfate using microwave calcination was feasible. Hematite was obtained under the following optimized conditions: calcination temperature, 850 °C; microwave power, 650 W; and sample amount, 40 g. The obtained hematite satisfied the first-grade quality requirements. The total ferrum value was more than 58%, and the total sulfur and phosphorus contents were less than 0.5% and 0.2%, respectively. X-ray powder diffraction and scanning electron microscopy were used to characterize the structure and morphology of microsized hematite powder. The particles were non-spherical in shape, and the average particle size distribution was 10.45 μm. This work provides new potential applications for waste ferrous sulfate.展开更多
The effects of microwave sintering and conventional H2 sintering on the microstructure and properties of W-15Cu alloy using ultrafine W-15Cu composite powder fabricated by spray drying ＆ calcining-continuous reductio...The effects of microwave sintering and conventional H2 sintering on the microstructure and properties of W-15Cu alloy using ultrafine W-15Cu composite powder fabricated by spray drying ＆ calcining-continuous reduction technology were investigated. In comparison to the conventional HE sintering processing, microwave sintering to W-15Cu can be achieved at lower sintering temperature and shorter sintering time. Furthermore, higher performances in microwave sintered compacts were obtained, but high microwave sintering temperature or long microwave sintering time could result in coarser microstructures.展开更多
In order to understand the physical mechanism of multipactor discharge on dielectric window surface under high power microwave （HPM） excitation in vacuum, an electron movement simulation model based on the particle-...In order to understand the physical mechanism of multipactor discharge on dielectric window surface under high power microwave （HPM） excitation in vacuum, an electron movement simulation model based on the particle-in-cell （PIC） Monte Carlo （MC） is built in this paper. The influences of microwave electromagnetic field and electrostatic field from dielectric surface charging are simultaneously considered in this model. During the simulation, the emission velocity and angle distribution of secondary electrons from the dielectric surface are taken into account. The movement trajectories of electron clusters under complex field excitation are obtained. The influences of emergence angle and microwave electromagnetic parameters on the electron movement are analyzed. It is found that the emergence angle of electrons from the surface has significant effect on its movement, and both the impact energy and return time of electrons oscillate periodically with the phase of microwave field. The number of secondary electrons and induced electrostatic field from multipactoring are also investigated. The results reveal that both values oscillate periodically at twice the microwave frequency, which is due to the electron impact energy oscillating with microwave period. A schematic diagram is proposed to explain the periodical oscillation phenomena.展开更多
A series of Pd/γ-Al_(2)O_(3) hybrid catalysts were prepared by impregnation and subsequent calcination under microwave irradiation.The catalysts were used for direct synthesis of dimethylether(DME)from syngas.The res...A series of Pd/γ-Al_(2)O_(3) hybrid catalysts were prepared by impregnation and subsequent calcination under microwave irradiation.The catalysts were used for direct synthesis of dimethylether(DME)from syngas.The results show that calcination under microwave irradiation improved both the activity and selectivity of the catalysts for DME synthesis.The optimum power of the microwave was determined to be 420 W.Under such optimum conditions,CO conversion,DME selectivity and time space yield of DME were 60.1%,67.0%,and 21.5 mmol$mL-1$h^(-1),respectively.Based on various characterizations such as nitrogen physisorption,X-ray diffraction,COtemperature-programmed desorption,and Fourier transform infrared spectral analysis,the promotional effect of the microwave irradiation on the catalytic property was mainly attributed to both the higher dispersion of Pd and the significant increase in the adsorption on the CO-bridge of Pd.Microwave irradiation with very high power led to the increase in CO-bridge adsorption and thereby decreased the catalytic activity,whereas the coverage by metallic Pd of the active sites on acidicγ-Al_(2)O_(3) significantly occurred under microwave irradiation with very low power,resulting in a decrease in the selectivity to DME.展开更多
The incremental improved Back-Propagation （BP） neural network prediction model using the Levenberg-Marquardt algorithm based on optimizing theory is put forward, which can solve the problems existing in the process ...The incremental improved Back-Propagation （BP） neural network prediction model using the Levenberg-Marquardt algorithm based on optimizing theory is put forward, which can solve the problems existing in the process of calcinations for ammonium diuranate （ADU） by microwave heating, such as long testing cycle, high testing quan- tity, difficulty of optimization for process parameters. Many training data probably were offered by the way of increment batch and the limitation of the system mem- ory could make the training data infeasible when the sample scale was large. The prediction model of the nonlinear system is built, which can effectively predict the experiment of microwave calcining of ADU, and the incremental improved BP neural network is very useful in overeoining the local minimum problem, finding the global optimal solution and accelerating the convergence speed.展开更多
基金Project(2013AA064003)supported by the National Technology Research and Development Program of ChinaProject(51564033)supported by the National Natural Science Foundation of ChinaProject(2016FA023)supported by the Yunnan Applied Basic Research(CNMRCUXT1403)State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization,Kunming University of Science and Technology,China
文摘The preparation of microsized hematite powder from ferrous sulfate using microwave calcination was investigated based on the TG/DTG curves. The decomposition of industrial ferrous sulfate under air atmosphere was divided into three stages, and a ferrous sulfate sample added with 15% Fe_2O_3 could strongly absorb microwave energy. Therefore, preparing hematite powder from ferrous sulfate using microwave calcination was feasible. Hematite was obtained under the following optimized conditions: calcination temperature, 850 °C; microwave power, 650 W; and sample amount, 40 g. The obtained hematite satisfied the first-grade quality requirements. The total ferrum value was more than 58%, and the total sulfur and phosphorus contents were less than 0.5% and 0.2%, respectively. X-ray powder diffraction and scanning electron microscopy were used to characterize the structure and morphology of microsized hematite powder. The particles were non-spherical in shape, and the average particle size distribution was 10.45 μm. This work provides new potential applications for waste ferrous sulfate.
基金Funded by the Project for Science and Technology Plan of Wuhan City(200910321092)the Youth Science Plan for Light of the Morning Sun of Wuhan City (200750731270)
文摘The effects of microwave sintering and conventional H2 sintering on the microstructure and properties of W-15Cu alloy using ultrafine W-15Cu composite powder fabricated by spray drying ＆ calcining-continuous reduction technology were investigated. In comparison to the conventional HE sintering processing, microwave sintering to W-15Cu can be achieved at lower sintering temperature and shorter sintering time. Furthermore, higher performances in microwave sintered compacts were obtained, but high microwave sintering temperature or long microwave sintering time could result in coarser microstructures.
基金supported in part by the National High Technology Research and Development Program of China
文摘In order to understand the physical mechanism of multipactor discharge on dielectric window surface under high power microwave （HPM） excitation in vacuum, an electron movement simulation model based on the particle-in-cell （PIC） Monte Carlo （MC） is built in this paper. The influences of microwave electromagnetic field and electrostatic field from dielectric surface charging are simultaneously considered in this model. During the simulation, the emission velocity and angle distribution of secondary electrons from the dielectric surface are taken into account. The movement trajectories of electron clusters under complex field excitation are obtained. The influences of emergence angle and microwave electromagnetic parameters on the electron movement are analyzed. It is found that the emergence angle of electrons from the surface has significant effect on its movement, and both the impact energy and return time of electrons oscillate periodically with the phase of microwave field. The number of secondary electrons and induced electrostatic field from multipactoring are also investigated. The results reveal that both values oscillate periodically at twice the microwave frequency, which is due to the electron impact energy oscillating with microwave period. A schematic diagram is proposed to explain the periodical oscillation phenomena.
基金supported by the Special Fund for Major State Basic Research Project(Grant 2005CB221204-G)the Fund from the Natural Science Foundation of China for Innovative Research Group(Grant 50921002)+1 种基金the Research Fund from Key Laboratory of Coal Processing&Efficient Utilization,Ministry of Education(Grant CPEUKF08-09)Yong Teacher Research Foundation from China University of Mining&Technology(Grant OH080254).
文摘A series of Pd/γ-Al_(2)O_(3) hybrid catalysts were prepared by impregnation and subsequent calcination under microwave irradiation.The catalysts were used for direct synthesis of dimethylether(DME)from syngas.The results show that calcination under microwave irradiation improved both the activity and selectivity of the catalysts for DME synthesis.The optimum power of the microwave was determined to be 420 W.Under such optimum conditions,CO conversion,DME selectivity and time space yield of DME were 60.1%,67.0%,and 21.5 mmol$mL-1$h^(-1),respectively.Based on various characterizations such as nitrogen physisorption,X-ray diffraction,COtemperature-programmed desorption,and Fourier transform infrared spectral analysis,the promotional effect of the microwave irradiation on the catalytic property was mainly attributed to both the higher dispersion of Pd and the significant increase in the adsorption on the CO-bridge of Pd.Microwave irradiation with very high power led to the increase in CO-bridge adsorption and thereby decreased the catalytic activity,whereas the coverage by metallic Pd of the active sites on acidicγ-Al_(2)O_(3) significantly occurred under microwave irradiation with very low power,resulting in a decrease in the selectivity to DME.
基金supported by the National Natural Science Foundation of China (No.50734007)Technology Project of Yunnan Province (No.2007GA002)
文摘The incremental improved Back-Propagation （BP） neural network prediction model using the Levenberg-Marquardt algorithm based on optimizing theory is put forward, which can solve the problems existing in the process of calcinations for ammonium diuranate （ADU） by microwave heating, such as long testing cycle, high testing quan- tity, difficulty of optimization for process parameters. Many training data probably were offered by the way of increment batch and the limitation of the system mem- ory could make the training data infeasible when the sample scale was large. The prediction model of the nonlinear system is built, which can effectively predict the experiment of microwave calcining of ADU, and the incremental improved BP neural network is very useful in overeoining the local minimum problem, finding the global optimal solution and accelerating the convergence speed.
