The improvement of mechanical properties must be achieved by designing and constructing more suitable microstructure,such as hierarchical microstructure.In order to significantly enhance the creep resistance of titani...The improvement of mechanical properties must be achieved by designing and constructing more suitable microstructure,such as hierarchical microstructure.In order to significantly enhance the creep resistance of titanium matrix composites(TMCs),two-scale network microstructure was constructed including the first-scale network(<150μm)with micro-TiB whisker(TiBw)reinforcement and the second-scale network(<30μm)with nano-Ti5Si3 reinforcement by powder metallurgy and in-situ synthesis.The results showed that the creep rate of the composite was remarkably reduced by an order of magnitude compared with the Ti6Al4V alloy at 550℃,600℃,650℃ under the stresses between 100 MPa and 350 MPa.Moreover,the rupture time of the composite was increased by 20 times,compared with that of the Ti6Al4 Valloy at 550℃/300 MPa.The superior creep resistance could be attributed to the hierarchical microstructure.The micro-TiBw reinforcement in the first-scale network boundary contributed to creep resistance primarily by blocking grain boundary sliding,while the nano-Ti5Si3 particle in the second-scale network boundary mainly by hindering phase boundary sliding.In addition,the nano-Ti5Si3 particle was dissolved,and precipitated with smaller size than the primary Ti5Si3.This phenomenon was attributed to Si element diffusion under high temperature and external stress,which could further continuously enhance the creep resistance.Finally,the creep rate during steady-state stage was significantly decreased,which manifested superior creep resistance of the composite.展开更多
Using the SG-III prototype laser at China Academy of Engineering Physics,Mianyang,we irradiated polystyrene(CH)samples with a thermal radiation drive,reaching conditions on the principal Hugoniot up to P≈1 TPa(10 Mba...Using the SG-III prototype laser at China Academy of Engineering Physics,Mianyang,we irradiated polystyrene(CH)samples with a thermal radiation drive,reaching conditions on the principal Hugoniot up to P≈1 TPa(10 Mbar),and away from the Hugoniot up to P≈300 GPa(3 Mbar).The response of each sample was measured with a velocity interferometry diagnostic to determine the material and shock velocity,and hence the conditions reached,and the reflectivity of the sample,from which changes in the conductivity can be inferred.By applying the selfimpedance mismatch technique with the measured velocities,the pressure and density of thermodynamic points away from the principal Hugoniot were determined.Our results show an unexpectedly large reflectivity at the highest shock pressures,while the off-Hugoniot points agree with previous work suggesting that shock-compressed CH conductivity is primarily temperature-dependent.展开更多
The target backsheath field acceleration mechanism is one of the main mechanisms of laser-driven proton acceleration(LDPA)and strongly depends on the comprehensive performance of the ultrashort ultra-intense lasers us...The target backsheath field acceleration mechanism is one of the main mechanisms of laser-driven proton acceleration(LDPA)and strongly depends on the comprehensive performance of the ultrashort ultra-intense lasers used as the driving sources.The successful use of the SG-II Peta-watt(SG-II PW)laser facility for LDPA and its applications in radiographic diagnoses have been manifested by the good performance of the SG-II PW facility.Recently,the SG-II PW laser facility has undergone extensive maintenance and a comprehensive technical upgrade in terms of the seed source,laser contrast and terminal focus.LDPA experiments were performed using the maintained SG-II PW laser beam,and the highest cutoff energy of the proton beam was obviously increased.Accordingly,a double-film target structure was used,and the maximum cutoff energy of the proton beam was up to 70 MeV.These results demonstrate that the comprehensive performance of the SG-II PW laser facility was improved significantly.展开更多
Despite the immense interest in magnetic,topological,and magnetoelectronic phenomena in isolated layers of 2D materials and their vertically stacked heterostructures,there remains a dearth of 2D magnetic materials tha...Despite the immense interest in magnetic,topological,and magnetoelectronic phenomena in isolated layers of 2D materials and their vertically stacked heterostructures,there remains a dearth of 2D magnetic materials that can be readily exfoliated into single layers.Here,we synthesize EuSn_(2)As_(2),the first exfoliatable,layered magnetic Zintl-Klemm phase that features van der Waals bonding between neighboring layers.In these crystals,Eu^(2+)4f^(7) spins magnetically order at 24 K and are coupled ferromagnetically within each layer and antiferromagnetically,with some potential canting,across adjacent layers.Magnetic ground state DFT calculations and temperature-dependent transport measurements on single crystals together establish that EuSn_(2)As_(2) is semimetallic.Finally,we show that this material can be thinned down to a few layers having steps corresponding to SnAsEuAsSn layers via micromechanical exfoliation.This work opens up further explorations into the design,synthesis,and layer-dependent magnetic properties of exfoliatable,lanthanidebased magnetic van der Waals Zintl phases.展开更多
基金financially supported by the National Key R&D Program of China (No. 2017YFB0703100)the National Natural Science Foundation of China (NSFC) under Grant Nos. 51822103, 51671068 and 51731009the Fundamental Research Funds for the Central Universities (No. HIT.BRETIV.201902)
文摘The improvement of mechanical properties must be achieved by designing and constructing more suitable microstructure,such as hierarchical microstructure.In order to significantly enhance the creep resistance of titanium matrix composites(TMCs),two-scale network microstructure was constructed including the first-scale network(<150μm)with micro-TiB whisker(TiBw)reinforcement and the second-scale network(<30μm)with nano-Ti5Si3 reinforcement by powder metallurgy and in-situ synthesis.The results showed that the creep rate of the composite was remarkably reduced by an order of magnitude compared with the Ti6Al4V alloy at 550℃,600℃,650℃ under the stresses between 100 MPa and 350 MPa.Moreover,the rupture time of the composite was increased by 20 times,compared with that of the Ti6Al4 Valloy at 550℃/300 MPa.The superior creep resistance could be attributed to the hierarchical microstructure.The micro-TiBw reinforcement in the first-scale network boundary contributed to creep resistance primarily by blocking grain boundary sliding,while the nano-Ti5Si3 particle in the second-scale network boundary mainly by hindering phase boundary sliding.In addition,the nano-Ti5Si3 particle was dissolved,and precipitated with smaller size than the primary Ti5Si3.This phenomenon was attributed to Si element diffusion under high temperature and external stress,which could further continuously enhance the creep resistance.Finally,the creep rate during steady-state stage was significantly decreased,which manifested superior creep resistance of the composite.
基金The authors would like to thank the technical teams at LFRC for their invaluable work producing the targets and operating the facility.N.J.H.and D.K.were supported by the Helmholtz Association under Grant No.VH-NG-1141.Y.L.was supported by the National Natural Science Foundation of China(Grant No.11605189).
文摘Using the SG-III prototype laser at China Academy of Engineering Physics,Mianyang,we irradiated polystyrene(CH)samples with a thermal radiation drive,reaching conditions on the principal Hugoniot up to P≈1 TPa(10 Mbar),and away from the Hugoniot up to P≈300 GPa(3 Mbar).The response of each sample was measured with a velocity interferometry diagnostic to determine the material and shock velocity,and hence the conditions reached,and the reflectivity of the sample,from which changes in the conductivity can be inferred.By applying the selfimpedance mismatch technique with the measured velocities,the pressure and density of thermodynamic points away from the principal Hugoniot were determined.Our results show an unexpectedly large reflectivity at the highest shock pressures,while the off-Hugoniot points agree with previous work suggesting that shock-compressed CH conductivity is primarily temperature-dependent.
基金National Natural Science Foundation of China(Grant No.12075227)the National Natural Science Foundation of China-NSAF(Grant No.U2130121)+1 种基金the National Key Research and Development Program of China(Grant No.2016YFA0401102)the Science Challenge Project(Grant No.TZ2018005).
文摘The target backsheath field acceleration mechanism is one of the main mechanisms of laser-driven proton acceleration(LDPA)and strongly depends on the comprehensive performance of the ultrashort ultra-intense lasers used as the driving sources.The successful use of the SG-II Peta-watt(SG-II PW)laser facility for LDPA and its applications in radiographic diagnoses have been manifested by the good performance of the SG-II PW facility.Recently,the SG-II PW laser facility has undergone extensive maintenance and a comprehensive technical upgrade in terms of the seed source,laser contrast and terminal focus.LDPA experiments were performed using the maintained SG-II PW laser beam,and the highest cutoff energy of the proton beam was obviously increased.Accordingly,a double-film target structure was used,and the maximum cutoff energy of the proton beam was up to 70 MeV.These results demonstrate that the comprehensive performance of the SG-II PW laser facility was improved significantly.
基金Analytical Spectroscopy Laboratory and the Surface Analysis Laboratory(NSF DMR-0114098)of The Ohio State University Department of Chemistry and BiochemistryThe Ohio State University Nanosystems Laboratory(NSL)+1 种基金Funding for this research was provided by the Center for Emergent Materials:an NSF MRSEC under award number DMR-1420451J.E.G.acknowledges the Camille and Henry Dreyfus Foundation for partial support.
文摘Despite the immense interest in magnetic,topological,and magnetoelectronic phenomena in isolated layers of 2D materials and their vertically stacked heterostructures,there remains a dearth of 2D magnetic materials that can be readily exfoliated into single layers.Here,we synthesize EuSn_(2)As_(2),the first exfoliatable,layered magnetic Zintl-Klemm phase that features van der Waals bonding between neighboring layers.In these crystals,Eu^(2+)4f^(7) spins magnetically order at 24 K and are coupled ferromagnetically within each layer and antiferromagnetically,with some potential canting,across adjacent layers.Magnetic ground state DFT calculations and temperature-dependent transport measurements on single crystals together establish that EuSn_(2)As_(2) is semimetallic.Finally,we show that this material can be thinned down to a few layers having steps corresponding to SnAsEuAsSn layers via micromechanical exfoliation.This work opens up further explorations into the design,synthesis,and layer-dependent magnetic properties of exfoliatable,lanthanidebased magnetic van der Waals Zintl phases.
