南海西北陆缘构造演化极其复杂,受到红河断裂、海南地幔柱和南海形成演化等多种因素的控制。莺歌海盆地位于南海西北部,发育了巨厚的新生代沉积物,详细记录了南海西北陆缘新生代的演化历史。但是莺歌海盆地新生代以来主要受到何种构造...南海西北陆缘构造演化极其复杂,受到红河断裂、海南地幔柱和南海形成演化等多种因素的控制。莺歌海盆地位于南海西北部,发育了巨厚的新生代沉积物,详细记录了南海西北陆缘新生代的演化历史。但是莺歌海盆地新生代以来主要受到何种构造因素的控制目前还不太清楚。本文在莺歌海盆地较为均匀地选择了7口钻井和23口模拟井,通过空盆构造沉降方法重建了莺歌海盆地的构造沉降量、构造沉降速率和沉积速率,同时运用重力反演方法模拟了莺歌海盆地深部地壳结构,并结合前人研究成果进行了综合分析。结果发现莺歌海盆地在裂陷期(45-23 Ma BP),盆地北部和中部沉降速率较大,南部沉降速率较小;在裂后期(23-0 Ma BP),盆地北部和中部沉降速率存在两期“台阶式”上升,分别为23-11.7 Ma BP和11.7 Ma BP至今,北部裂后期构造沉降速率最大可达80 m/Ma,中部最大可达110 m/Ma;南部地堑和隆起裂后期分别在11.7-5.7 Ma BP和15.9-11.7 Ma BP构造沉降速率最大可达70 m/Ma。莺歌海盆地新生代整体上表现为沉降速率与沉积速率变化基本一致,说明构造沉降对沉积速率具有显著的控制作用。重力反演发现莺歌海盆地可能存在下地壳高密度异常体,结合盆地沉积物内部钻遇玄武岩,我们推测下地壳高密度异常体为基性侵入体。通过与南海周边其他沉积盆地沉降速率对比发现,几乎所有盆地都在中中新世-晚中新世(15.9-11.7 Ma BP)发生了加速沉降事件,我们认为这可能跟南海海盆停止扩张导致大陆边缘次生地幔对流消失有关。莺歌海盆地5.7 Ma BP至今的加速沉降则可能与红河断裂右旋走滑活动有关。展开更多
Two unit cells to 200Åthick ultrathin YBa_(2)Cu_(3)O_(7)-δfilms have been synthesized and their growth mechanism and physical properties have been studied.Atomic force microscopy showed that the films grow with ...Two unit cells to 200Åthick ultrathin YBa_(2)Cu_(3)O_(7)-δfilms have been synthesized and their growth mechanism and physical properties have been studied.Atomic force microscopy showed that the films grow with both spiral and layer by layer modes and the screw dislocations appeared even in the 6 unit cells thick films.In the initial growth stages of the films,the strong dependence of T_(c)on the film thickness is discussed.展开更多
A nearly single-phased Bi-2223 sample with T_(c) 108K was studied by low-temperature powder x-ray diffraction.Several discontinuous changes of lattice parameters are observed around 245,160,125,100 and 20K.The most pr...A nearly single-phased Bi-2223 sample with T_(c) 108K was studied by low-temperature powder x-ray diffraction.Several discontinuous changes of lattice parameters are observed around 245,160,125,100 and 20K.The most pronounced anomalies occur dose to the superconducting transition temperature.Our observation indicates that electron-lattice interaction is quite strong near T_(c).展开更多
Chemical doping or substitutions were carried out in both the Ba site and Bi site in Ba-K-Bi-O superconductor.The large single crystals of Ba-K-M-Bi-O(M=Ca,Eu,In and T1)were prepared by using the electrocrystallizatio...Chemical doping or substitutions were carried out in both the Ba site and Bi site in Ba-K-Bi-O superconductor.The large single crystals of Ba-K-M-Bi-O(M=Ca,Eu,In and T1)were prepared by using the electrocrystallization method.The resulting crystalline materials were characterized by x-ray photoelectron spectroscopy and magnetic method.The results show that partial substitutions of Ca or Eu in the Ba site suppress T_(c) more drastically than that of TI in the Bi site.All the present chemical substitutions result in a decrease in T_(c).展开更多
High critical temperature superconductors of mercury-based system were synthesized under high pressure and high temperature.The resistance and ac magnetic susceptibility measurements for sample prepared at 25 kbar and...High critical temperature superconductors of mercury-based system were synthesized under high pressure and high temperature.The resistance and ac magnetic susceptibility measurements for sample prepared at 25 kbar and 850℃for 1.5 h show that the sample without any added treatment was a mixture of Hg-1201 and Hg-1223.The Tc values of Hg-1223 phase and Hg-1201 phase are 132 and 98 K,respectively.展开更多
M&gnetic relaxation and magnetization of the powder melting Y_(1-x)Ho_(x)Ba_(2)Cu_(3)O_(7)(x=0.2,0.4 and 0.6)samples have been measured at the temperature of 70K.The pinning potential U and magnetization critical ...M&gnetic relaxation and magnetization of the powder melting Y_(1-x)Ho_(x)Ba_(2)Cu_(3)O_(7)(x=0.2,0.4 and 0.6)samples have been measured at the temperature of 70K.The pinning potential U and magnetization critical current density J_(c) have been obtained according to the Anderson-Kim model and Bean model.It is found that both U and J_(c) were in^uenced by doping Bb.In the sample with x=0.4 the pinning potential U has a value of 3.2 eV when the Held is equal to 1 kG and parallel to c-axis,which is the highest one we have known in the high Tc superconductors.展开更多
Superconducting compound (Sr_(0.86)Nd_(0.14))CuO_(2 )with the infinite layer structure was synthesized under high pressure.This tetragonal structure a×a transforms into a superstructure 2√2a ×2√2a when the...Superconducting compound (Sr_(0.86)Nd_(0.14))CuO_(2 )with the infinite layer structure was synthesized under high pressure.This tetragonal structure a×a transforms into a superstructure 2√2a ×2√2a when the sample was in situ heated in transmission electron microscope to about 600K.An anormalous resistance change of the sample during heating in vacuum to 400℃ confinned the phase transformation.Aftrer the superlattice formationf the sample lost its superconductivity and became semiconducting.展开更多
The effect of annealing process in flowing nitrogen on the formation of super-conducting phases in Nd_(1.85)Ce_(0.15)CuO_(4-y) has been investigated.Two super-conductingphases with onset temperature Tcons of about 15 ...The effect of annealing process in flowing nitrogen on the formation of super-conducting phases in Nd_(1.85)Ce_(0.15)CuO_(4-y) has been investigated.Two super-conductingphases with onset temperature Tcons of about 15 and 25K might be formed when the samples were annealed at various temperatures ranging from 850℃ to 870℃ and from 880℃ to 920℃,respectively.The dependence of Tcons on the annealing temperature was reported.展开更多
文摘南海西北陆缘构造演化极其复杂,受到红河断裂、海南地幔柱和南海形成演化等多种因素的控制。莺歌海盆地位于南海西北部,发育了巨厚的新生代沉积物,详细记录了南海西北陆缘新生代的演化历史。但是莺歌海盆地新生代以来主要受到何种构造因素的控制目前还不太清楚。本文在莺歌海盆地较为均匀地选择了7口钻井和23口模拟井,通过空盆构造沉降方法重建了莺歌海盆地的构造沉降量、构造沉降速率和沉积速率,同时运用重力反演方法模拟了莺歌海盆地深部地壳结构,并结合前人研究成果进行了综合分析。结果发现莺歌海盆地在裂陷期(45-23 Ma BP),盆地北部和中部沉降速率较大,南部沉降速率较小;在裂后期(23-0 Ma BP),盆地北部和中部沉降速率存在两期“台阶式”上升,分别为23-11.7 Ma BP和11.7 Ma BP至今,北部裂后期构造沉降速率最大可达80 m/Ma,中部最大可达110 m/Ma;南部地堑和隆起裂后期分别在11.7-5.7 Ma BP和15.9-11.7 Ma BP构造沉降速率最大可达70 m/Ma。莺歌海盆地新生代整体上表现为沉降速率与沉积速率变化基本一致,说明构造沉降对沉积速率具有显著的控制作用。重力反演发现莺歌海盆地可能存在下地壳高密度异常体,结合盆地沉积物内部钻遇玄武岩,我们推测下地壳高密度异常体为基性侵入体。通过与南海周边其他沉积盆地沉降速率对比发现,几乎所有盆地都在中中新世-晚中新世(15.9-11.7 Ma BP)发生了加速沉降事件,我们认为这可能跟南海海盆停止扩张导致大陆边缘次生地幔对流消失有关。莺歌海盆地5.7 Ma BP至今的加速沉降则可能与红河断裂右旋走滑活动有关。
基金Supported by the Chinese National Center for Research and Development on Superconductivity.
文摘Two unit cells to 200Åthick ultrathin YBa_(2)Cu_(3)O_(7)-δfilms have been synthesized and their growth mechanism and physical properties have been studied.Atomic force microscopy showed that the films grow with both spiral and layer by layer modes and the screw dislocations appeared even in the 6 unit cells thick films.In the initial growth stages of the films,the strong dependence of T_(c)on the film thickness is discussed.
文摘A nearly single-phased Bi-2223 sample with T_(c) 108K was studied by low-temperature powder x-ray diffraction.Several discontinuous changes of lattice parameters are observed around 245,160,125,100 and 20K.The most pronounced anomalies occur dose to the superconducting transition temperature.Our observation indicates that electron-lattice interaction is quite strong near T_(c).
文摘Chemical doping or substitutions were carried out in both the Ba site and Bi site in Ba-K-Bi-O superconductor.The large single crystals of Ba-K-M-Bi-O(M=Ca,Eu,In and T1)were prepared by using the electrocrystallization method.The resulting crystalline materials were characterized by x-ray photoelectron spectroscopy and magnetic method.The results show that partial substitutions of Ca or Eu in the Ba site suppress T_(c) more drastically than that of TI in the Bi site.All the present chemical substitutions result in a decrease in T_(c).
文摘High critical temperature superconductors of mercury-based system were synthesized under high pressure and high temperature.The resistance and ac magnetic susceptibility measurements for sample prepared at 25 kbar and 850℃for 1.5 h show that the sample without any added treatment was a mixture of Hg-1201 and Hg-1223.The Tc values of Hg-1223 phase and Hg-1201 phase are 132 and 98 K,respectively.
基金Supported by the National Center for Research and Development on Superconductivity of China.
文摘M&gnetic relaxation and magnetization of the powder melting Y_(1-x)Ho_(x)Ba_(2)Cu_(3)O_(7)(x=0.2,0.4 and 0.6)samples have been measured at the temperature of 70K.The pinning potential U and magnetization critical current density J_(c) have been obtained according to the Anderson-Kim model and Bean model.It is found that both U and J_(c) were in^uenced by doping Bb.In the sample with x=0.4 the pinning potential U has a value of 3.2 eV when the Held is equal to 1 kG and parallel to c-axis,which is the highest one we have known in the high Tc superconductors.
文摘Superconducting compound (Sr_(0.86)Nd_(0.14))CuO_(2 )with the infinite layer structure was synthesized under high pressure.This tetragonal structure a×a transforms into a superstructure 2√2a ×2√2a when the sample was in situ heated in transmission electron microscope to about 600K.An anormalous resistance change of the sample during heating in vacuum to 400℃ confinned the phase transformation.Aftrer the superlattice formationf the sample lost its superconductivity and became semiconducting.
文摘The effect of annealing process in flowing nitrogen on the formation of super-conducting phases in Nd_(1.85)Ce_(0.15)CuO_(4-y) has been investigated.Two super-conductingphases with onset temperature Tcons of about 15 and 25K might be formed when the samples were annealed at various temperatures ranging from 850℃ to 870℃ and from 880℃ to 920℃,respectively.The dependence of Tcons on the annealing temperature was reported.
