The nV‐MCM‐41 catalysts were prepared by one‐step hydrothermal synthesis and applied to the oxidative dehydrogenation of propane（ODHP） in the presence of CO2. Several state‐of‐the‐art char‐acterization method...The nV‐MCM‐41 catalysts were prepared by one‐step hydrothermal synthesis and applied to the oxidative dehydrogenation of propane（ODHP） in the presence of CO2. Several state‐of‐the‐art char‐acterization methods were performed to explore the correlation between catalytic performance and the physicochemical characterizations of the catalysts. Because moderate amounts of V species were introduced into the framework of MCM‐41, the catalyst maintained a large specific surface area, a highly ordered mesoporous structure, and highly dispersed V active sites（monomeric and dimeric V oxide species）, while the high‐vanadium‐doping catalysts caused an enhancement in the number of acidic sites and V2O5 crystallites. The ODHP reaction showed that the 6.8 V‐MCM‐41（V content 6.8 wt%） catalyst exhibits high activity and stability, and the C3H8/CO2 molar ratio（1：4） was suitable. The promoting effect of CO2 on the oxidative dehydrogenation of ODHP was demonstrated as the reaction coupling mechanism and ＂lattice oxygen＂ mechanism.展开更多
Vanadium dioxide(VO 2)thin films are used for protection from high-energy laser hits due to their semiconductor-to-metal phase transition experienced during heating at temperature of approximately 68 ℃,which followed...Vanadium dioxide(VO 2)thin films are used for protection from high-energy laser hits due to their semiconductor-to-metal phase transition experienced during heating at temperature of approximately 68 ℃,which followed by a abrupt change of optical behavior, namely from transparent semiconductor state below 68 ℃ to highly reflective metallic state beyond 68 ℃.The preparation and properties of the films are described as well as the primary principle of the device for protection from high energy laser hits. An ion-beam-sputtering system is used to deposit VO 2 thin films.The technique is reactive ion beam sputtering of vanadium at temperature of 200 ℃ on Si, Ge and Si 3N 4 substrates in a well controlled atmosphere of argon with a partial pressure of O 2, followed by a post annealing at 400-550 ℃ with argon gas.The optical transmittance changes from 60% to 4% are obtained within the temperature range from 50 ℃ to 70 ℃. X-ray diffraction (XRD) shows that the films are of single-phase VO 2.展开更多
文摘The nV‐MCM‐41 catalysts were prepared by one‐step hydrothermal synthesis and applied to the oxidative dehydrogenation of propane（ODHP） in the presence of CO2. Several state‐of‐the‐art char‐acterization methods were performed to explore the correlation between catalytic performance and the physicochemical characterizations of the catalysts. Because moderate amounts of V species were introduced into the framework of MCM‐41, the catalyst maintained a large specific surface area, a highly ordered mesoporous structure, and highly dispersed V active sites（monomeric and dimeric V oxide species）, while the high‐vanadium‐doping catalysts caused an enhancement in the number of acidic sites and V2O5 crystallites. The ODHP reaction showed that the 6.8 V‐MCM‐41（V content 6.8 wt%） catalyst exhibits high activity and stability, and the C3H8/CO2 molar ratio（1：4） was suitable. The promoting effect of CO2 on the oxidative dehydrogenation of ODHP was demonstrated as the reaction coupling mechanism and ＂lattice oxygen＂ mechanism.
文摘Vanadium dioxide(VO 2)thin films are used for protection from high-energy laser hits due to their semiconductor-to-metal phase transition experienced during heating at temperature of approximately 68 ℃,which followed by a abrupt change of optical behavior, namely from transparent semiconductor state below 68 ℃ to highly reflective metallic state beyond 68 ℃.The preparation and properties of the films are described as well as the primary principle of the device for protection from high energy laser hits. An ion-beam-sputtering system is used to deposit VO 2 thin films.The technique is reactive ion beam sputtering of vanadium at temperature of 200 ℃ on Si, Ge and Si 3N 4 substrates in a well controlled atmosphere of argon with a partial pressure of O 2, followed by a post annealing at 400-550 ℃ with argon gas.The optical transmittance changes from 60% to 4% are obtained within the temperature range from 50 ℃ to 70 ℃. X-ray diffraction (XRD) shows that the films are of single-phase VO 2.
