Development of high-performance and cost-effective catalysts for electrocatalytic hydrogen evolution reaction(HER)play crucial role in the growing hydrogen economy.Recently,the atomically dispersed metal catalysts hav...Development of high-performance and cost-effective catalysts for electrocatalytic hydrogen evolution reaction(HER)play crucial role in the growing hydrogen economy.Recently,the atomically dispersed metal catalysts have attracted increasing attention due to their ultimate atom utilization and great potential for highly cost-effective and high-efficiency HER electrocatalyst.Herein,we propose a hightemperature treatment strategy to furtherly improve the HER performance of atomically dispersed Ptbased catalyst.Interestingly,after appropriate high-temperature treatment on the atomically dispersed Pt0.8@CN,the Pt species on the designed N-doped porous carbon substrate with rich defect sites can be re-dispersed to single atom state with new coordination environment.The obtained Pt0.8@CN-1000 shows superior HER performance with overpotential of 13 m V at 10 m A cm^(-2)and mass activity of 11,284 m A/mgPtat-0.1 V,much higher than that of the pristine Pt0.8@CN and commercial Pt/C catalyst.The experimental and theoretical investigations indicate that the high-temperature treatment induces the restructuring of coordination environment and then the optimized Pt electronic state leads to the enhanced HER performances.This work affords new strategy and insights to develop the atomically dispersed high-efficiency catalysts.展开更多
The atomic-scale surface roughness of Si(110) reconstructed via high-temperature Ar annealing is immediately increased by non uniform accidental oxidation during the unloading process (called reflow oxidation) during ...The atomic-scale surface roughness of Si(110) reconstructed via high-temperature Ar annealing is immediately increased by non uniform accidental oxidation during the unloading process (called reflow oxidation) during high-temperature Ar annealing. In particular, for a reconstructed Si(110) surface, characteristic line-shaped oxidation occurs at preferential oxidation sites appearing in pentagonal pairs in the directions of Si[-112] and/or [-11-2]. We previously reported that the roughness increase of reconstructed Si(110) due to reflow oxidation can be restrained by replacing Ar gas with H2 gas at 1000°C during the cooling to 100°C after high-temperature Ar annealing. It was speculated that preferential oxidation sites on reconstructed Si(110) were eliminated by H2 gas etching and hydrogen termination of dangling bonds. Thus, it is necessary to investigate the effect of H2 gas etching and hydrogen termination behavior on the reconstructed Si(110) surface structure. In this study, we evaluated in detail the relationship between the temperature at which the H2 gas replaces the Ar in high-temperature Ar annealing and the reconstructed Si(110) surface structure. The maximum height of the roughness on the reconstructed surface was the same as if Ar gas was used when the H2 gas introduction temperature was 200°C, although the amount of reflow oxidation was decreased to 70% by hydrogen termination. Furthermore, line-shaped oxidation still occurs when H2 gas replaces Ar at this low temperature. Therefore, we conclude that oxidation is caused by slight Si etching at low temperatures, and thus the preferential oxidation sites on the reconstructed structure must be eliminated by hydrogen etching in order to form an atomically smooth Si(110) surface.展开更多
The electrochemical performance of double phase Mg Ni alloy was characterized at 25°C and 70°C, in order to evaluate briefly its utility as negative electrode materials in nickel metal hydride batteries. ...The electrochemical performance of double phase Mg Ni alloy was characterized at 25°C and 70°C, in order to evaluate briefly its utility as negative electrode materials in nickel metal hydride batteries. The results show that the electrochemical capacity of double phase Mg Ni alloy is rarely low at 25°C, but increased rapidly when the temperature is enhanced, and the double phase Mg Ni alloy has its maximum capacity at the first discharge cycle, but the capacity degrades rapidly with cycling number.展开更多
The tensile deformation hot simulation test of as-cast 1420 Al-Li alloy was performed on Gleeble-1500 Thermal Simulator in the deformation temperature range from 350 to 450 ℃ and the strain rate range from 0.01 to l0...The tensile deformation hot simulation test of as-cast 1420 Al-Li alloy was performed on Gleeble-1500 Thermal Simulator in the deformation temperature range from 350 to 450 ℃ and the strain rate range from 0.01 to l0.0s-1.The tensile fracture behavior of the 1420 Al-Li alloy at high temperature was studied experimently. The results show that the tensile fracture mode of the 1420 Al-Li alloy at high temperature is changed from typical transgranular ductile fracture to intergranular brittle fracture with the increase of the deformation temperature and the strain rate. It is made out that the precipitation of LiH is the fundamental reason for the intergranular brittle fracture of the 1420 Al-Li alloy at high temperature. The mechanism of hydrogen embrittlement of the 1420 Al-Li alloy at high temperature was discussed, and it was proposed that the hydrogen embrittlement at high temperature is an integrated function of the dynamic and the static force, which enrichs the theories of hydrogen embrittlemen t.展开更多
A PHE (Process Heat Exchanger) is a key component in transferring high-temperature heat generated from a VHTR (Very High Temperature Reactor) to a chemical reaction for the massive production of hydrogen. Last year, a...A PHE (Process Heat Exchanger) is a key component in transferring high-temperature heat generated from a VHTR (Very High Temperature Reactor) to a chemical reaction for the massive production of hydrogen. Last year, a 10 kW class lab-scale PHE prototype made of Hastelloy-X was manufactured at the Korea Atomic Energy Research Institute (KAERI), and a performance test of the PHE prototype is currently underway in a small-scale nitrogen gas loop at KAERI. The PHE prototype is composed of two kinds of flow plates: grooves 1.0 mm in diameter machined into the flow plate for the primary coolant, and waved channels bent into the flow plate for the secondary coolant. Inside the 10 kW class lab-scale PHE prototype, twenty flow plates for the primary and secondary coolants are stacked in turn. In this study, to understand the macroscopic structural behavior of the PHE prototype under the steady-state operating condition of the gas loop, high-temperature structural analyses on the 10 kW class lab-scale PHE prototype were performed for two extreme cases: in the event of contacting the flow plates together, and when not contacting them. The analysis results for the extreme cases were also compared.展开更多
The structure and high-temperature electrochemical properties of the as-cast and annealed （940 °C, 8 h） La0.60Nd0.15Mg0.25Ni3.3Si0.10 hydrogen storage alloys were investigated. The X-ray diffraction revealed th...The structure and high-temperature electrochemical properties of the as-cast and annealed （940 °C, 8 h） La0.60Nd0.15Mg0.25Ni3.3Si0.10 hydrogen storage alloys were investigated. The X-ray diffraction revealed that the multiphase structure of the as-cast alloy with LaNi5 phase as the main phase was converted into a double-phase structure with La2Ni7 phase as the main phase after annealing. The surface morphology studied by scanning electronic microscope （SEM） showed that the annealed alloy had a much higher anti-corrosion ability than the as-cast alloy. Both alloys presented excellent activation characteristics at all test temperatures. The maximum discharge capacity of the as-cast alloy decreased when the test temperature increased, while the temperature almost had no effect on the annealed alloy. As the test temperature increased, the cyclic stability and charge retention of both alloys decreased, and these properties were improved significantly by annealing.展开更多
Variation and degradation of P-110 casing steel mechanical properties, due to sulfide stress cracking （SSC） in sour environments, was investigated using tensile and impact tests. These tests were carried out on spec...Variation and degradation of P-110 casing steel mechanical properties, due to sulfide stress cracking （SSC） in sour environments, was investigated using tensile and impact tests. These tests were carried out on specimens, which were pretreated under the following conditions for 168 hours： temperature, 60 ℃; pressure, 10 MPa; H2S partial pressure, 1 MPa and CO2 partial pressure, 1 MPa; preload stress, 80% of the yield strength （os）; medium, simulated formation water. The reduction in tensile and impact strengths for P-110 casing specimens in corrosive environments were 28% and 54%, respectively. The surface morphology analysis indicated that surface damage and uniform plastic deformation occurred as a result of strain aging. Impact toughness of the casing decreased significantly and intergranular cracking occurred when specimens were maintained at a high stress level of 85% %.展开更多
Chou model was used to investigate the dehydriding reaction kinetic mechanism of MgH_2-Nb_2O_5 hydrogen storage materials at 573 K.A new conception,'characteristic absorption/desorption time(t_c)'was introduce...Chou model was used to investigate the dehydriding reaction kinetic mechanism of MgH_2-Nb_2O_5 hydrogen storage materials at 573 K.A new conception,'characteristic absorption/desorption time(t_c)'was introduced to characterize the reaction rate The fitting results show that for the hydrogen desorbing mechanism,the surface penetration is the rate-controlling step.The mechanism remains the same even when the original panicle size of Nb_2O_5 is before ball milling(BM) or when the BM time changes And t_c indicates that the desorption rate of MgH_2-Nb_2O_5 will be faster than that of MgH_2-Nb_2O_5 by BM.The dehydriding reaction rate of MgH_2-Nb_2O_5(micro particle) BMed for 50 h is 4.76 times faster than that of the MgH_2-Nb_2O_5(micro panicle) BMed for 0.25 h,while the dehydriding reaction rate of MgH_2-Nb_2O_5(nano particle) BMed for 50 h is only 1.18 times as that of the MgH2-Nb_2O_5 (nano particle) BMed for 0.25 h.The dehydriding reaction rate of the BMed MgH_2-Nb_2O_5(nano particle) is 1-9 times faster than that of the BMed MgH_2-Nb_2O_5(micro particle).展开更多
基金financially supported by the National Science Foundation of China(21773112,21173119,and 21273109)the National Key Technology R&D Program of China(2017YFB0310704)the Fundamental Research Funds for the Central Universities and the Hubei Key Laboratory for Processing and Application of Catalytic Materials(CH201401)。
文摘Development of high-performance and cost-effective catalysts for electrocatalytic hydrogen evolution reaction(HER)play crucial role in the growing hydrogen economy.Recently,the atomically dispersed metal catalysts have attracted increasing attention due to their ultimate atom utilization and great potential for highly cost-effective and high-efficiency HER electrocatalyst.Herein,we propose a hightemperature treatment strategy to furtherly improve the HER performance of atomically dispersed Ptbased catalyst.Interestingly,after appropriate high-temperature treatment on the atomically dispersed Pt0.8@CN,the Pt species on the designed N-doped porous carbon substrate with rich defect sites can be re-dispersed to single atom state with new coordination environment.The obtained Pt0.8@CN-1000 shows superior HER performance with overpotential of 13 m V at 10 m A cm^(-2)and mass activity of 11,284 m A/mgPtat-0.1 V,much higher than that of the pristine Pt0.8@CN and commercial Pt/C catalyst.The experimental and theoretical investigations indicate that the high-temperature treatment induces the restructuring of coordination environment and then the optimized Pt electronic state leads to the enhanced HER performances.This work affords new strategy and insights to develop the atomically dispersed high-efficiency catalysts.
文摘The atomic-scale surface roughness of Si(110) reconstructed via high-temperature Ar annealing is immediately increased by non uniform accidental oxidation during the unloading process (called reflow oxidation) during high-temperature Ar annealing. In particular, for a reconstructed Si(110) surface, characteristic line-shaped oxidation occurs at preferential oxidation sites appearing in pentagonal pairs in the directions of Si[-112] and/or [-11-2]. We previously reported that the roughness increase of reconstructed Si(110) due to reflow oxidation can be restrained by replacing Ar gas with H2 gas at 1000°C during the cooling to 100°C after high-temperature Ar annealing. It was speculated that preferential oxidation sites on reconstructed Si(110) were eliminated by H2 gas etching and hydrogen termination of dangling bonds. Thus, it is necessary to investigate the effect of H2 gas etching and hydrogen termination behavior on the reconstructed Si(110) surface structure. In this study, we evaluated in detail the relationship between the temperature at which the H2 gas replaces the Ar in high-temperature Ar annealing and the reconstructed Si(110) surface structure. The maximum height of the roughness on the reconstructed surface was the same as if Ar gas was used when the H2 gas introduction temperature was 200°C, although the amount of reflow oxidation was decreased to 70% by hydrogen termination. Furthermore, line-shaped oxidation still occurs when H2 gas replaces Ar at this low temperature. Therefore, we conclude that oxidation is caused by slight Si etching at low temperatures, and thus the preferential oxidation sites on the reconstructed structure must be eliminated by hydrogen etching in order to form an atomically smooth Si(110) surface.
文摘The electrochemical performance of double phase Mg Ni alloy was characterized at 25°C and 70°C, in order to evaluate briefly its utility as negative electrode materials in nickel metal hydride batteries. The results show that the electrochemical capacity of double phase Mg Ni alloy is rarely low at 25°C, but increased rapidly when the temperature is enhanced, and the double phase Mg Ni alloy has its maximum capacity at the first discharge cycle, but the capacity degrades rapidly with cycling number.
文摘The tensile deformation hot simulation test of as-cast 1420 Al-Li alloy was performed on Gleeble-1500 Thermal Simulator in the deformation temperature range from 350 to 450 ℃ and the strain rate range from 0.01 to l0.0s-1.The tensile fracture behavior of the 1420 Al-Li alloy at high temperature was studied experimently. The results show that the tensile fracture mode of the 1420 Al-Li alloy at high temperature is changed from typical transgranular ductile fracture to intergranular brittle fracture with the increase of the deformation temperature and the strain rate. It is made out that the precipitation of LiH is the fundamental reason for the intergranular brittle fracture of the 1420 Al-Li alloy at high temperature. The mechanism of hydrogen embrittlement of the 1420 Al-Li alloy at high temperature was discussed, and it was proposed that the hydrogen embrittlement at high temperature is an integrated function of the dynamic and the static force, which enrichs the theories of hydrogen embrittlemen t.
文摘A PHE (Process Heat Exchanger) is a key component in transferring high-temperature heat generated from a VHTR (Very High Temperature Reactor) to a chemical reaction for the massive production of hydrogen. Last year, a 10 kW class lab-scale PHE prototype made of Hastelloy-X was manufactured at the Korea Atomic Energy Research Institute (KAERI), and a performance test of the PHE prototype is currently underway in a small-scale nitrogen gas loop at KAERI. The PHE prototype is composed of two kinds of flow plates: grooves 1.0 mm in diameter machined into the flow plate for the primary coolant, and waved channels bent into the flow plate for the secondary coolant. Inside the 10 kW class lab-scale PHE prototype, twenty flow plates for the primary and secondary coolants are stacked in turn. In this study, to understand the macroscopic structural behavior of the PHE prototype under the steady-state operating condition of the gas loop, high-temperature structural analyses on the 10 kW class lab-scale PHE prototype were performed for two extreme cases: in the event of contacting the flow plates together, and when not contacting them. The analysis results for the extreme cases were also compared.
基金Project supported by the National Natural Science Foundation of China (50701011)the National High Technology Research and Develop-ment Program of China (2007AA03Z230, 2009AA03Z230)
文摘The structure and high-temperature electrochemical properties of the as-cast and annealed （940 °C, 8 h） La0.60Nd0.15Mg0.25Ni3.3Si0.10 hydrogen storage alloys were investigated. The X-ray diffraction revealed that the multiphase structure of the as-cast alloy with LaNi5 phase as the main phase was converted into a double-phase structure with La2Ni7 phase as the main phase after annealing. The surface morphology studied by scanning electronic microscope （SEM） showed that the annealed alloy had a much higher anti-corrosion ability than the as-cast alloy. Both alloys presented excellent activation characteristics at all test temperatures. The maximum discharge capacity of the as-cast alloy decreased when the test temperature increased, while the temperature almost had no effect on the annealed alloy. As the test temperature increased, the cyclic stability and charge retention of both alloys decreased, and these properties were improved significantly by annealing.
基金support of the State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University in Chinathe National Natural Science Foundation of China (Grant No.51004084)
文摘Variation and degradation of P-110 casing steel mechanical properties, due to sulfide stress cracking （SSC） in sour environments, was investigated using tensile and impact tests. These tests were carried out on specimens, which were pretreated under the following conditions for 168 hours： temperature, 60 ℃; pressure, 10 MPa; H2S partial pressure, 1 MPa and CO2 partial pressure, 1 MPa; preload stress, 80% of the yield strength （os）; medium, simulated formation water. The reduction in tensile and impact strengths for P-110 casing specimens in corrosive environments were 28% and 54%, respectively. The surface morphology analysis indicated that surface damage and uniform plastic deformation occurred as a result of strain aging. Impact toughness of the casing decreased significantly and intergranular cracking occurred when specimens were maintained at a high stress level of 85% %.
基金Project(2006AZ001)supported by the Shanghai Municipal Education Commission,ChinaProject(06JC14031)supported by the Scienceand Technology Commission of Shanghai Municipality,China+2 种基金Project(06QA14021)supported by the Shanghai Rising-Star Program(Atype),ChinaProject(200746)supported by the Foundation for the Author of National Excellent Doctoral Dissertation of ChinaProjectsupported by the Innovation Fund for Graduate Student of Shanghai University,China
文摘Chou model was used to investigate the dehydriding reaction kinetic mechanism of MgH_2-Nb_2O_5 hydrogen storage materials at 573 K.A new conception,'characteristic absorption/desorption time(t_c)'was introduced to characterize the reaction rate The fitting results show that for the hydrogen desorbing mechanism,the surface penetration is the rate-controlling step.The mechanism remains the same even when the original panicle size of Nb_2O_5 is before ball milling(BM) or when the BM time changes And t_c indicates that the desorption rate of MgH_2-Nb_2O_5 will be faster than that of MgH_2-Nb_2O_5 by BM.The dehydriding reaction rate of MgH_2-Nb_2O_5(micro particle) BMed for 50 h is 4.76 times faster than that of the MgH_2-Nb_2O_5(micro panicle) BMed for 0.25 h,while the dehydriding reaction rate of MgH_2-Nb_2O_5(nano particle) BMed for 50 h is only 1.18 times as that of the MgH2-Nb_2O_5 (nano particle) BMed for 0.25 h.The dehydriding reaction rate of the BMed MgH_2-Nb_2O_5(nano particle) is 1-9 times faster than that of the BMed MgH_2-Nb_2O_5(micro particle).
