Optical transmission characteristics of water between quartz glass under shock compression are in situ observed by using the technique of missile-borne light source. Through these transmission properties, the phase tr...Optical transmission characteristics of water between quartz glass under shock compression are in situ observed by using the technique of missile-borne light source. Through these transmission properties, the phase transition of liquid water is studied. The experimental results show that liquid water exhibits transparency decline phenomenon when the pressure is lower than 2 GPa under shock compression process, and the transparency variation is related to the existence of quartz glass. So, the transparency decline is attributed to a quartz-induced freezing phenomenon of water.展开更多
Nanotwinned diamond（nt-diamond）,which demonstrates unprecedented hardness and stability,is synthesized through the martensitic transformation of onion carbons at high pressure and high temperature（HPHT）.Its hardne...Nanotwinned diamond（nt-diamond）,which demonstrates unprecedented hardness and stability,is synthesized through the martensitic transformation of onion carbons at high pressure and high temperature（HPHT）.Its hardness and stability increase with decreasing twin thickness at the nanoscale.However,the formation mechanism of nanotwinning substructures within diamond nanograins is not well established.Here,we characterize the nanotwins in nt-diamonds synthesized under different HPHT conditions.Our observation shows that the nanotwin thickness reaches a minimum at ~20 GPa,below which phase-transformation twins and deformation twins coexist.Then,we use the density-functional-based tight-binding method and kinetic dislocation theory to investigate the subsequent plastic deformation mechanism in these pre-existing phase-transformation diamond twins.Our results suggest that pressure-dependent conversion of the plastic deformation mechanism occurs at a critical synthetic pressure for nt-diamond,which explains the existence of the minimum twin thickness.Our findings provide guidance on optimizing the synthetic conditions for fabricating nt-diamond with higher hardness and stability.展开更多
文摘Optical transmission characteristics of water between quartz glass under shock compression are in situ observed by using the technique of missile-borne light source. Through these transmission properties, the phase transition of liquid water is studied. The experimental results show that liquid water exhibits transparency decline phenomenon when the pressure is lower than 2 GPa under shock compression process, and the transparency variation is related to the existence of quartz glass. So, the transparency decline is attributed to a quartz-induced freezing phenomenon of water.
基金supported by the National Natural Science Foundation of China(51421091,51332005,51572225,51272227, 51172197,51525205 and 51672239)the US National Science Foundation(EAR-1361276)
文摘Nanotwinned diamond（nt-diamond）,which demonstrates unprecedented hardness and stability,is synthesized through the martensitic transformation of onion carbons at high pressure and high temperature（HPHT）.Its hardness and stability increase with decreasing twin thickness at the nanoscale.However,the formation mechanism of nanotwinning substructures within diamond nanograins is not well established.Here,we characterize the nanotwins in nt-diamonds synthesized under different HPHT conditions.Our observation shows that the nanotwin thickness reaches a minimum at ~20 GPa,below which phase-transformation twins and deformation twins coexist.Then,we use the density-functional-based tight-binding method and kinetic dislocation theory to investigate the subsequent plastic deformation mechanism in these pre-existing phase-transformation diamond twins.Our results suggest that pressure-dependent conversion of the plastic deformation mechanism occurs at a critical synthetic pressure for nt-diamond,which explains the existence of the minimum twin thickness.Our findings provide guidance on optimizing the synthetic conditions for fabricating nt-diamond with higher hardness and stability.
