Carbide nucleation, growth and trapping behavior in directionally solIdified MAR-M247 LC alloyand the corresponding mechanism have been investigated. Carbide forming element enrichmentcontrols the carbide nucleation a...Carbide nucleation, growth and trapping behavior in directionally solIdified MAR-M247 LC alloyand the corresponding mechanism have been investigated. Carbide forming element enrichmentcontrols the carbide nucleation and the carbide growth behavior. If the carbide forming elementenrichment and the nucleation sites are suitable, carbide nucleation can occur both above andbelow the liquidus temperature. Heterogeneous carbide nucleation is the preferred nucleationmechanism at low carbide forming element enrichment. Carbide growth occurs mainIy at inter-secondary ry dendrite arm area and lower part of the mushy zone. The carbides are subsequentlytrapped at these positions after growing to a certain size. Some carbides are only partially trappedby the solid-liquid interface and the carbide growth accelerates after being partially trapped. Acritical growth rate exists between 2×10-6 m/s and 5 ×10-6 m/s. The carbide volume fractiondecreases in the directionally solidified part at slow growth rate that is caused by the lack ofsuitable growth site and the low trapping ability of the solid-liquid展开更多
The diffusion of nitrogen atom in Cr thin film is studied. The temperature of the film under ion beam bombarding was measured by a new method and discussed theoretically. The temperature measured by means of thin film...The diffusion of nitrogen atom in Cr thin film is studied. The temperature of the film under ion beam bombarding was measured by a new method and discussed theoretically. The temperature measured by means of thin film resistor gave a same level of volume. On the basis of the conservation of energy in equilibrium state, a semi-theoretical formula has been derived. The factors ion beam assisted diffusion were discussed. The result of AES analysis indicates that the arrangement of N atoms is long and smooth. HREM analysis and dynamic resistance measurement show that the Cr-nitride formed by N^+ implantation is in the near surface layers and can not grow very deep. The assemble of N was observed by means of TEM.展开更多
Gas hydrates have endowed with great potential in gas storage,and rapid formation of gas hydrates is critical to use this novel technology.This work evaluated the natural gas hydrate formation process,which was compar...Gas hydrates have endowed with great potential in gas storage,and rapid formation of gas hydrates is critical to use this novel technology.This work evaluated the natural gas hydrate formation process,which was compared from six parameters,including conversion of water to hydrate,storage capacity,the rate of hydrate formation,space velocity(SV)of hydrate reaction,energy consumption and hydrate removal.The literature was selected by analyzing and comparing these six parameters mentioned above,meanwhile placing emphasis on the three parameters of storage capacity,the rate of hydrate formation and space velocity of hydrate reaction.Through analysis and comparison,four conclusions could be obtained as follows.Firstly,the overall performance of the stirring process and the spraying process were better than other processes after analyzing the six parameters.Secondly,the additive types,the reactor structure and the reactor size had influence on the natural gas hydrate formation process.Thirdly,the energy consumption via reciprocating impact in the hydrate formation process was higher than that via stirring,spraying and static higee.Finally,it was one key for hydrate removal to realize the hydrate industrial production.展开更多
Despite the recent progress on controllable synthesis of alkynyl-protected Au nanoclusters,the effective synthetic means are very limited and the cluster formation process still remains puzzling.Here,we develop a nove...Despite the recent progress on controllable synthesis of alkynyl-protected Au nanoclusters,the effective synthetic means are very limited and the cluster formation process still remains puzzling.Here,we develop a novel synchronous nucleation and passivation strategy to fabricate Au36(PA)24(PA=phenylacetylenyl) nanoclusters with high yield.In Au36(PA)24formation process,Au22(PA)18as key intermediate was identified.Meanwhile,Au22(PA)18can be synthesized under a low amount of reductant,and by employing more reductants,Au22(PA)18can turn into Au36(PA)24eventually.Moreover,the structure evolution from Au22(PA)18to Au36(PA)24is proposed,where four Au13cuboctahedra can yield one Au28kernel.Finally,the ratiocination is verified by the good accordance between the predicted intermediate/product ratio and the experimental value.This study not only offers a novel synthetic strategy,but also sheds light on understanding the structural evolution process of alkynyl-protected Au nanoclusters at atomic level.展开更多
This study examines the diversity of low-level jet(LLJ)formation and related physical processes over southern China.A total of 171 LLJ formation events with enhanced daily southwesterlies and early-morning maximum win...This study examines the diversity of low-level jet(LLJ)formation and related physical processes over southern China.A total of 171 LLJ formation events with enhanced daily southwesterlies and early-morning maximum wind speeds were observed during the mei-yu seasons of 1989–2018.The LLJs can be further categorized into four types based on the increases in the daily mean and diurnal amplitude of the low-level winds.Analysis of the synoptic-scale disturbances shows that the two types of LLJ formation(Q1 and Q4),which feature large increases of daily southerly wind components,are mainly induced by west-east dipole patterns of pressure change,in association with the enhanced southwest vortex and/or the western Pacific subtropical high(WPSH).In contrast,the other two types(Q2 and Q3),which feature relatively large increases in their daily westerly components,are related to a northwest-southeast dipole pattern of pressure change due to the mid-latitude trough and the WPSH.We further analyze the considerable variations in the diurnal thermal forcing among the LLJ formation events.The strong(weak)daytime heating of solar radiation leads to relatively large(small)increases in the diurnal amplitude of low-level winds in Q1 and Q2(Q3 and Q4)types.Therefore,different combinations of synopticscale disturbances and diurnal thermal forcings are found to account for the diversity in LLJ formation and associated differences in downstream rainfall patterns.These results help to improve our understanding and prediction of the formation of LLJs.展开更多
In order to design a kind of heat exchanger suitable to the indirect-touched gas hydrate cool storage vessel, a visual observation of HCFC141b gas hydrate formation/decomposition process was presented through a self-d...In order to design a kind of heat exchanger suitable to the indirect-touched gas hydrate cool storage vessel, a visual observation of HCFC141b gas hydrate formation/decomposition process was presented through a self-designed small-scale visualization apparatus of gas hydrate cool storage. Based on the shooted photos and recorded temperatures, the formation/decomposition process of HCFC141b are described, some characteristics are concluded, and some suggestions of designing heat exchanger are indicated according to the specific characteristics of HCFC141b gas hydrate formation/decomposition process.展开更多
The northeastern Tibetan Plateau exhibits steep topography and strong internal or external dynamic geological effect and is frequently subjected to strong earthquakes and heavy rainfall. The geological evolution has r...The northeastern Tibetan Plateau exhibits steep topography and strong internal or external dynamic geological effect and is frequently subjected to strong earthquakes and heavy rainfall. The geological evolution has resulted in a wide distribution of ancient landslides, which has become a hotspot for studying ancient landslide formation and reactivation. In recent decades, several ancient landslides on both banks of the Longwu River, Qinghai Province, China were reactivated, causing serious economic losses and casualties. This study conducted remote sensing interpretation and ground surveys on these ancient landslides. Totally 59 ancient landslides were identified, and the formation mechanism, evolution process, and resurrection mechanism of the Longwu Xishan No.2 ancient landslide were analyzed by means of a detailed field geological survey, drilling, and series of experimental tests such as the particle size distribution test, the Xray diffraction test and the mechanical properties test. The results show that the formation of these ancient landslides is closely associated with the uplift of the Tibetan Plateau and the erosion of the Longwu River. Firstly, the intermittent uplift of the Tibetan Plateau lead to the diversion and downcutting of the Longwu River basin, which forms the alternate slope topography with steep and slow slopes, thereby providing favourable topography and slope structure conditions for the formation of landslides. Secondly, 34.5% clay-mineral content in the Neoproterozoic mudstone with 32.7% particle size less than 0.005 mm, and the corrosion and softening effects of the Neogene mudstone with high clay mineral content under the erosion of water provides favourable material conditions for the formation of landslides. Thirdly, rainfall and human activities are the primary triggering factors for the revival of this ancient landslide group. It is revealed that the evolution process of the ancient landslides on both banks of the Longwu River can be divided into five stages namely tectonic rapid uplift slope formation, river erosion creep-sliding deformation, slope instability critical status, landslide failure-movement-accumulation, and slope reactivation under rainfall erosion and engineering excavation.展开更多
In this paper, stable isotope(δ^(18)O, δD) investigations were completed in ground ice from a deep borehole in the Beiluhe Basin on northern Qinghai-Tibet Plateau to unravel the isotopic variations of ground ice and...In this paper, stable isotope(δ^(18)O, δD) investigations were completed in ground ice from a deep borehole in the Beiluhe Basin on northern Qinghai-Tibet Plateau to unravel the isotopic variations of ground ice and their possible source water. The δ^(18)O and δD of ground ice show distinctive characteristics compared with precipitation and surface water. The near-surface ground ice is highly enriched in heavier isotopes(δ^(18)O and δD), which were gradually depleted from top to bottom along the profile. It is suggestive of different origin and ice formation process. According to isotopic variations, the ice profile was divided into three sections: the near-surface ground ice at 2.5 m is frozen by the active-layer water which suffered evaporation. It is possible that ground ice between 3 and 4.2 m is recharged by the infiltration of snowmelt. From 5 to 6 m, the ground ice show complex origin and formation processes. Isotopic variations from 6 to 11.1 m and 20.55 m indicate different replenishment water. The calculated slope of freezing line(S=6.4) is larger than the experimental value(5.76), and is suggestive of complex origin and formation process of ground ice.展开更多
Fe_(3)Si and FeSi intermetallic compounds were prepared by CaCl_(2)-NaCl melt electrolysis at 800℃from the non-magnetic copper slag compound.The phase transition of the cathode particles with different electrolysis v...Fe_(3)Si and FeSi intermetallic compounds were prepared by CaCl_(2)-NaCl melt electrolysis at 800℃from the non-magnetic copper slag compound.The phase transition of the cathode particles with different electrolysis voltages and durations was investigated by X-ray fluorescence spectroscopy,inductively coupled plasma spectroscopy,X-ray diffraction,and scanning electron microscopy.The results showed that Fe_(3)Si and FeSi intermetallic compounds can be obtained by one-step electrolysis for 10 h at 3.2 V and two-step electrolysis of 2.5 V for 4 h and 3.2 V for 6 h.However,the current efficiency increased from 31.70%of one-step electrolysis to 39.87%of two-step electrolysis.The formation of Fe_(3)Si and FeSi intermetallic compounds is a gradual evolution process with the increase in Si content,following the formation law of Fe→FeSi→Fe_(3)Si+FeSi→FeSi.The metallic impurities of the final product were 1.29 wt.%Mg and 3.85 wt.%Al,respectively.展开更多
Lithium-ion batteries(LIBs)provide power for a variety of applications from the portable electronics to electric vehicles,and now they are supporting the smart grid.Safety of LIBs is of paramount importance in these s...Lithium-ion batteries(LIBs)provide power for a variety of applications from the portable electronics to electric vehicles,and now they are supporting the smart grid.Safety of LIBs is of paramount importance in these scenarios.Specifically,thermal safety arouses increasing attention with the piling-up of LIBs.Heat generation can be significant.Hazardous incidents happen when thermal runaway occurs in a single cell level and drives the battery pack failure.Moreover,thermal runaway of LIBs is believed to originate from the exothermic reactions starting from the breakdown of the solid/cathode electrolyte interphase(SEI/CEI).To mitigate this challenge for a safe operation of LIBs,one straightforward and low-cost method is to build thermally stable SEI/CEI.This review gives an overview on the thermal behaviors of SEI/CEI as the first step in thermal runaway.We analyzed the electrolyte composition and the formation process of SEI/CEI that enable SEI/CEI of high thermal stability.It is identified that the stable lithium salts coupled with solvents of high boiling point is one way to enhance thermal stability of the battery system.In addition,the unsaturated bonds,halogen,phosphorus,sulfur,phenol,organic borate,borane,and silane are functional components to facilitate the formation of a thermally stable SEI/CEI,which is the immediate solution to boost thermal stability of high capacity electrodes.Moreover,in-situ polymerization/solidification is effective in enhancing simultaneously the electrochemical,chemical,and thermal stability.Finally,we revealed that only by constructing a stable SEI/CEI simultaneously could we harvest a battery system of high thermal stability.展开更多
文摘Carbide nucleation, growth and trapping behavior in directionally solIdified MAR-M247 LC alloyand the corresponding mechanism have been investigated. Carbide forming element enrichmentcontrols the carbide nucleation and the carbide growth behavior. If the carbide forming elementenrichment and the nucleation sites are suitable, carbide nucleation can occur both above andbelow the liquidus temperature. Heterogeneous carbide nucleation is the preferred nucleationmechanism at low carbide forming element enrichment. Carbide growth occurs mainIy at inter-secondary ry dendrite arm area and lower part of the mushy zone. The carbides are subsequentlytrapped at these positions after growing to a certain size. Some carbides are only partially trappedby the solid-liquid interface and the carbide growth accelerates after being partially trapped. Acritical growth rate exists between 2×10-6 m/s and 5 ×10-6 m/s. The carbide volume fractiondecreases in the directionally solidified part at slow growth rate that is caused by the lack ofsuitable growth site and the low trapping ability of the solid-liquid
文摘The diffusion of nitrogen atom in Cr thin film is studied. The temperature of the film under ion beam bombarding was measured by a new method and discussed theoretically. The temperature measured by means of thin film resistor gave a same level of volume. On the basis of the conservation of energy in equilibrium state, a semi-theoretical formula has been derived. The factors ion beam assisted diffusion were discussed. The result of AES analysis indicates that the arrangement of N atoms is long and smooth. HREM analysis and dynamic resistance measurement show that the Cr-nitride formed by N^+ implantation is in the near surface layers and can not grow very deep. The assemble of N was observed by means of TEM.
基金supported by the Scientific and Technological Research Project of the Science and Technology Department of Henan Province,China(152102210041)the National Natural Science Foundation of China(NSFC-U1404519)+1 种基金the China Postdoctoral Science Foundation(2016 M602260)the Program of Biomass Resources Processing and Efficient Utilization of Outstanding Foreign Scientists’Workroom(GZS2018004)。
文摘Gas hydrates have endowed with great potential in gas storage,and rapid formation of gas hydrates is critical to use this novel technology.This work evaluated the natural gas hydrate formation process,which was compared from six parameters,including conversion of water to hydrate,storage capacity,the rate of hydrate formation,space velocity(SV)of hydrate reaction,energy consumption and hydrate removal.The literature was selected by analyzing and comparing these six parameters mentioned above,meanwhile placing emphasis on the three parameters of storage capacity,the rate of hydrate formation and space velocity of hydrate reaction.Through analysis and comparison,four conclusions could be obtained as follows.Firstly,the overall performance of the stirring process and the spraying process were better than other processes after analyzing the six parameters.Secondly,the additive types,the reactor structure and the reactor size had influence on the natural gas hydrate formation process.Thirdly,the energy consumption via reciprocating impact in the hydrate formation process was higher than that via stirring,spraying and static higee.Finally,it was one key for hydrate removal to realize the hydrate industrial production.
基金This work was supported by Guangdong Natural Science Funds for Distinguished Young Scholars(2015A030306006)Guangzhou Science and Technology Plan Projects(201804010323)+1 种基金the fundamental funds for central universities(SCUT,2018ZD022)the National Natural Science Foundation of China(21971070).
文摘Despite the recent progress on controllable synthesis of alkynyl-protected Au nanoclusters,the effective synthetic means are very limited and the cluster formation process still remains puzzling.Here,we develop a novel synchronous nucleation and passivation strategy to fabricate Au36(PA)24(PA=phenylacetylenyl) nanoclusters with high yield.In Au36(PA)24formation process,Au22(PA)18as key intermediate was identified.Meanwhile,Au22(PA)18can be synthesized under a low amount of reductant,and by employing more reductants,Au22(PA)18can turn into Au36(PA)24eventually.Moreover,the structure evolution from Au22(PA)18to Au36(PA)24is proposed,where four Au13cuboctahedra can yield one Au28kernel.Finally,the ratiocination is verified by the good accordance between the predicted intermediate/product ratio and the experimental value.This study not only offers a novel synthetic strategy,but also sheds light on understanding the structural evolution process of alkynyl-protected Au nanoclusters at atomic level.
基金supported by the Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)the National Natural Science Foundation of China(Grant Nos.42275002,41875055,and 42122033).
文摘This study examines the diversity of low-level jet(LLJ)formation and related physical processes over southern China.A total of 171 LLJ formation events with enhanced daily southwesterlies and early-morning maximum wind speeds were observed during the mei-yu seasons of 1989–2018.The LLJs can be further categorized into four types based on the increases in the daily mean and diurnal amplitude of the low-level winds.Analysis of the synoptic-scale disturbances shows that the two types of LLJ formation(Q1 and Q4),which feature large increases of daily southerly wind components,are mainly induced by west-east dipole patterns of pressure change,in association with the enhanced southwest vortex and/or the western Pacific subtropical high(WPSH).In contrast,the other two types(Q2 and Q3),which feature relatively large increases in their daily westerly components,are related to a northwest-southeast dipole pattern of pressure change due to the mid-latitude trough and the WPSH.We further analyze the considerable variations in the diurnal thermal forcing among the LLJ formation events.The strong(weak)daytime heating of solar radiation leads to relatively large(small)increases in the diurnal amplitude of low-level winds in Q1 and Q2(Q3 and Q4)types.Therefore,different combinations of synopticscale disturbances and diurnal thermal forcings are found to account for the diversity in LLJ formation and associated differences in downstream rainfall patterns.These results help to improve our understanding and prediction of the formation of LLJs.
基金supported by the National Natural Science Foundation of China (No. 50176051, No. 59836230)the Satate Key Development Program for Basic Research of China (No. 2000026306).
文摘In order to design a kind of heat exchanger suitable to the indirect-touched gas hydrate cool storage vessel, a visual observation of HCFC141b gas hydrate formation/decomposition process was presented through a self-designed small-scale visualization apparatus of gas hydrate cool storage. Based on the shooted photos and recorded temperatures, the formation/decomposition process of HCFC141b are described, some characteristics are concluded, and some suggestions of designing heat exchanger are indicated according to the specific characteristics of HCFC141b gas hydrate formation/decomposition process.
基金financially supported by the National Natural Science Foundation of China(grant numbers 41907238 and 41931296)National Key R&D Program of China(grant numbers 2018YFC1508804)+1 种基金Sichuan Science and Technology Program(grant numbers 2019YJ0534 and 2021YFSY0036)State Key Laboratory of Geohazard Prevention and Geo-environment Protection Independent Research Project(SKLGP2021Z008)。
文摘The northeastern Tibetan Plateau exhibits steep topography and strong internal or external dynamic geological effect and is frequently subjected to strong earthquakes and heavy rainfall. The geological evolution has resulted in a wide distribution of ancient landslides, which has become a hotspot for studying ancient landslide formation and reactivation. In recent decades, several ancient landslides on both banks of the Longwu River, Qinghai Province, China were reactivated, causing serious economic losses and casualties. This study conducted remote sensing interpretation and ground surveys on these ancient landslides. Totally 59 ancient landslides were identified, and the formation mechanism, evolution process, and resurrection mechanism of the Longwu Xishan No.2 ancient landslide were analyzed by means of a detailed field geological survey, drilling, and series of experimental tests such as the particle size distribution test, the Xray diffraction test and the mechanical properties test. The results show that the formation of these ancient landslides is closely associated with the uplift of the Tibetan Plateau and the erosion of the Longwu River. Firstly, the intermittent uplift of the Tibetan Plateau lead to the diversion and downcutting of the Longwu River basin, which forms the alternate slope topography with steep and slow slopes, thereby providing favourable topography and slope structure conditions for the formation of landslides. Secondly, 34.5% clay-mineral content in the Neoproterozoic mudstone with 32.7% particle size less than 0.005 mm, and the corrosion and softening effects of the Neogene mudstone with high clay mineral content under the erosion of water provides favourable material conditions for the formation of landslides. Thirdly, rainfall and human activities are the primary triggering factors for the revival of this ancient landslide group. It is revealed that the evolution process of the ancient landslides on both banks of the Longwu River can be divided into five stages namely tectonic rapid uplift slope formation, river erosion creep-sliding deformation, slope instability critical status, landslide failure-movement-accumulation, and slope reactivation under rainfall erosion and engineering excavation.
基金supported by the National Natural Science Foundation of China(Grant No.41501071)by the State Key Laboratory of Frozen Soils Engineering(Grant No.SKLFSE201511)+1 种基金by the China Postdoctoral Science Foundation(Grant No.2016M590984)by the Chinese Academy of Sciences Key Research Program(Grant No.KZZD-EW-13)
文摘In this paper, stable isotope(δ^(18)O, δD) investigations were completed in ground ice from a deep borehole in the Beiluhe Basin on northern Qinghai-Tibet Plateau to unravel the isotopic variations of ground ice and their possible source water. The δ^(18)O and δD of ground ice show distinctive characteristics compared with precipitation and surface water. The near-surface ground ice is highly enriched in heavier isotopes(δ^(18)O and δD), which were gradually depleted from top to bottom along the profile. It is suggestive of different origin and ice formation process. According to isotopic variations, the ice profile was divided into three sections: the near-surface ground ice at 2.5 m is frozen by the active-layer water which suffered evaporation. It is possible that ground ice between 3 and 4.2 m is recharged by the infiltration of snowmelt. From 5 to 6 m, the ground ice show complex origin and formation processes. Isotopic variations from 6 to 11.1 m and 20.55 m indicate different replenishment water. The calculated slope of freezing line(S=6.4) is larger than the experimental value(5.76), and is suggestive of complex origin and formation process of ground ice.
基金This work was supported by the National Natural Science Foundation of China(No.52174315).
文摘Fe_(3)Si and FeSi intermetallic compounds were prepared by CaCl_(2)-NaCl melt electrolysis at 800℃from the non-magnetic copper slag compound.The phase transition of the cathode particles with different electrolysis voltages and durations was investigated by X-ray fluorescence spectroscopy,inductively coupled plasma spectroscopy,X-ray diffraction,and scanning electron microscopy.The results showed that Fe_(3)Si and FeSi intermetallic compounds can be obtained by one-step electrolysis for 10 h at 3.2 V and two-step electrolysis of 2.5 V for 4 h and 3.2 V for 6 h.However,the current efficiency increased from 31.70%of one-step electrolysis to 39.87%of two-step electrolysis.The formation of Fe_(3)Si and FeSi intermetallic compounds is a gradual evolution process with the increase in Si content,following the formation law of Fe→FeSi→Fe_(3)Si+FeSi→FeSi.The metallic impurities of the final product were 1.29 wt.%Mg and 3.85 wt.%Al,respectively.
基金Beijing Municipal Science&Technology Commission,Grant/Award Number:D181100004518003Key ProgramAutomobile Joint Fund of National Natural Science Foundation of China,Grant/Award Number:U1964205+2 种基金Key R&D Project of the Department of Science and Technology of Jiangsu Province,China,Grant/Award Number:BE2020003National Key R&D Program of China,Grant/Award Number:2016YFB0100100National Natural Science Foundation of China,Grant/Award Numbers:51822211,Y5JC011E21。
文摘Lithium-ion batteries(LIBs)provide power for a variety of applications from the portable electronics to electric vehicles,and now they are supporting the smart grid.Safety of LIBs is of paramount importance in these scenarios.Specifically,thermal safety arouses increasing attention with the piling-up of LIBs.Heat generation can be significant.Hazardous incidents happen when thermal runaway occurs in a single cell level and drives the battery pack failure.Moreover,thermal runaway of LIBs is believed to originate from the exothermic reactions starting from the breakdown of the solid/cathode electrolyte interphase(SEI/CEI).To mitigate this challenge for a safe operation of LIBs,one straightforward and low-cost method is to build thermally stable SEI/CEI.This review gives an overview on the thermal behaviors of SEI/CEI as the first step in thermal runaway.We analyzed the electrolyte composition and the formation process of SEI/CEI that enable SEI/CEI of high thermal stability.It is identified that the stable lithium salts coupled with solvents of high boiling point is one way to enhance thermal stability of the battery system.In addition,the unsaturated bonds,halogen,phosphorus,sulfur,phenol,organic borate,borane,and silane are functional components to facilitate the formation of a thermally stable SEI/CEI,which is the immediate solution to boost thermal stability of high capacity electrodes.Moreover,in-situ polymerization/solidification is effective in enhancing simultaneously the electrochemical,chemical,and thermal stability.Finally,we revealed that only by constructing a stable SEI/CEI simultaneously could we harvest a battery system of high thermal stability.
