The interpretation of heterometallic bonding nature is a basic work of inorganic chemistry.By means of intermetallic substitution of germylene anions with iron halide complexes CpFe(CO)_(2)I andβ-diketiminato Fe^Ⅱch...The interpretation of heterometallic bonding nature is a basic work of inorganic chemistry.By means of intermetallic substitution of germylene anions with iron halide complexes CpFe(CO)_(2)I andβ-diketiminato Fe^Ⅱchloride,the ferrogermylene complexes 3a,3b and 4a were synthesized and structurally characterized.The structural and IR characterizations show the presence of the Ge←Feπbackbonding in molecules 3a,3b and 4a.The computational works on frontier molecular orbitals and their comparison of energy states confirmed thatσdonation andπbackbonding are both weak in these molecules,despite three complexes have longer Ge-Fe bonds,whose strength decreases slightly with the degressive electron density around Fe environment in a sequence from 3a,3b to 4a.展开更多
The recent report of pressure-induced structural transition and signature of superconductivity with T_(c)≈80 K above 14 GPa in La_(3)Ni_(2)O_(7)crystals has garnered considerable attention.To further elaborate this d...The recent report of pressure-induced structural transition and signature of superconductivity with T_(c)≈80 K above 14 GPa in La_(3)Ni_(2)O_(7)crystals has garnered considerable attention.To further elaborate this discovery,we carried out comprehensive resistance measurements on La_(3)Ni_(2)O_(7)crystals grown in an optical-image floating zone furnace under oxygen pressure(15 bar)using a diamond anvil cell(DAC)and cubic anvil cell(CAC),which employ a solid(KBr)and liquid(glycerol)pressure-transmitting medium,respectively.Sample 1 measured in the DAC exhibits a semiconducting-like behavior with large resistance at low pressures and gradually becomes metallic upon compression.At pressures P 13.7 GPa we observed the appearance of a resistance drop of as much as~50%around 70 K,which evolves into a kink-like anomaly at pressures above 40 GPa and shifts to lower temperatures gradually with increasing magnetic field.These observations are consistent with the recent report mentioned above.On the other hand,sample 2 measured in the CAC retains metallic behavior in the investigated pressure range up to 15 GPa.The hump-like anomaly in resistance around~130 K at ambient pressure disappears at P≥2 GPa.In the pressure range of 11–15 GPa we observed the gradual development of a shoulder-like anomaly in resistance at low temperatures,which evolves into a pronounced drop of resistance of 98%below 62 K at 15 GPa,reaching a temperature-independent resistance of 20μΩbelow 20 K.Similarly,this resistance anomaly can be progressively shifted to lower temperatures by applying external magnetic fields,resembling a typical superconducting transition.Measurements on sample 3 in the CAC reproduce the resistance drop at pressures above 10 GPa and realize zero resistance below 10 K at 15 GPa even though an unusual semiconducting-like behavior is retained in the normal state.Based on these results,we constructed a dome-shaped superconducting phase diagram and discuss some issues regarding the sample-dependent behaviors on pressure-ind展开更多
Primary solidification phase and lamellar orientation are investigated in Ti-45Al-7Nb alloy at very high ratio of temperature gradient to growth rate （G/v） by a liquid-metal-cooled directionally solidified method. I...Primary solidification phase and lamellar orientation are investigated in Ti-45Al-7Nb alloy at very high ratio of temperature gradient to growth rate （G/v） by a liquid-metal-cooled directionally solidified method. It shows that Ti-45Al-7Nb alloy solidifies with primary ct phase. Longitudinal （parallel to growth direction） microstructure shows that a dendrites in solid-liquid mushy zone are discontinuous and transverse mierostructure of a dendrites is worm-like feature. Growth direction of a phase is about 80° away from （0001）,a direction, and close to （1120） a direction. The corresponding lamellar orientation is aligned at the angle of about 10° to growth direction, which is consistent with a-dendrite growth direction according to Blackburn orientation relationship. Therefore, due to the altered growth direction of a phase, the lamellar orientation in Ti-45Al-7Nb alloy is controlled at the G/v ratio of 5 × 10^9 K.sm^-2.展开更多
The γ-U phase alloys can be retained down to low temperatures with less required alloying concentration by using the splat-cooling technique with a cooling rate better than 10^6 K/s. Doping with 15 at.% Mo, Pt, Pd, N...The γ-U phase alloys can be retained down to low temperatures with less required alloying concentration by using the splat-cooling technique with a cooling rate better than 10^6 K/s. Doping with 15 at.% Mo, Pt, Pd, Nb leads to a stabilization of the cubic γ-U phase, while it requires much higher Zr concentrations （≥30 at.% Zr）. All U-T splats become superconducting with Tc in the range of 0.61-2.11 K. A good agreement of the experimentally observed specific-heat jump at Tc with that from BCS theory prediction was obtained for U-15 at.% Mo consisting of the γ-U phase with an ideal bcc A2 structure.展开更多
The localized plastic flow auto-waves observed for the stages of easy glide and linear work hardening in a number of metals are considered. The propagation rates were determined expe- rimentally for the auto-waves in ...The localized plastic flow auto-waves observed for the stages of easy glide and linear work hardening in a number of metals are considered. The propagation rates were determined expe- rimentally for the auto-waves in question with the aid of focused-image holography. The dispersion relation of quadratic form derived for localized plastic flow auto-waves and the dependencies of phase and group rates on wave number are discussed. A detailed comparison of the quantitative characteristics of phase and group waves has revealed that the two types of wave are closely related. An invariant is introduced for localized plastic flow phenomena occurring on the micro-and macro-scale levels in the deforming solid.展开更多
An analytical phase transformation model has been used to study the kinetics of crystallization of amorphous alloys sub- jected to either isothermal or isochronal anneals. The model has been applied to Mg82.3Cu17.7 an...An analytical phase transformation model has been used to study the kinetics of crystallization of amorphous alloys sub- jected to either isothermal or isochronal anneals. The model has been applied to Mg82.3Cu17.7 and Pd40Cu30P20Ni10, employing iso- thermal and isochronal differential scanning calorimetry. Applying different combinations of nucleation and growth mechanisms to the same experiments, the nucleation and growth modes dominating the crystallization and the values for the corresponding kinetic parameters, including the constant activation energies for nucleation and growth, have been determined. Further, the influence of isothermal pre-annealing on subsequent isochronal crystallization kinetics, involving a gradual change of nucleation mode up to site saturation with increase of pre-annealing, can be analyzed.展开更多
基金supported by National Science Foundation of China(No.22273072)the Shaanxi Provincial Enterprise Joint Fund(No.2021JLM-31)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2021JM-311)。
文摘The interpretation of heterometallic bonding nature is a basic work of inorganic chemistry.By means of intermetallic substitution of germylene anions with iron halide complexes CpFe(CO)_(2)I andβ-diketiminato Fe^Ⅱchloride,the ferrogermylene complexes 3a,3b and 4a were synthesized and structurally characterized.The structural and IR characterizations show the presence of the Ge←Feπbackbonding in molecules 3a,3b and 4a.The computational works on frontier molecular orbitals and their comparison of energy states confirmed thatσdonation andπbackbonding are both weak in these molecules,despite three complexes have longer Ge-Fe bonds,whose strength decreases slightly with the degressive electron density around Fe environment in a sequence from 3a,3b to 4a.
基金supported by the Beijing Natural Science Foundation(Grant No.Z190008)the National Key Research and Development Program of China(Grant Nos.2018YFA0305700 and 2021YFA1400200)+6 种基金the National Natural Science Foundation of China(Grant Nos.12025408,11921004,11834016,and 11888101)supported by the National Natural Science Foundation of China(Grant No.12174454)the Strategic Priority Research Program of CAS(Grant No.XDB33000000)CAS Project for Young Scientists in Basic Research(Grant Nos.2022YSBR-047 and 2022YSBR-048)the Users with Excellence Program of Hefei Science Center CAS(Grant No.2021HSCUE008)Guangdong Basic and Applied Basic Research Funds(Grant No.2021B1515120015)Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant No.2022B1212010008)。
文摘The recent report of pressure-induced structural transition and signature of superconductivity with T_(c)≈80 K above 14 GPa in La_(3)Ni_(2)O_(7)crystals has garnered considerable attention.To further elaborate this discovery,we carried out comprehensive resistance measurements on La_(3)Ni_(2)O_(7)crystals grown in an optical-image floating zone furnace under oxygen pressure(15 bar)using a diamond anvil cell(DAC)and cubic anvil cell(CAC),which employ a solid(KBr)and liquid(glycerol)pressure-transmitting medium,respectively.Sample 1 measured in the DAC exhibits a semiconducting-like behavior with large resistance at low pressures and gradually becomes metallic upon compression.At pressures P 13.7 GPa we observed the appearance of a resistance drop of as much as~50%around 70 K,which evolves into a kink-like anomaly at pressures above 40 GPa and shifts to lower temperatures gradually with increasing magnetic field.These observations are consistent with the recent report mentioned above.On the other hand,sample 2 measured in the CAC retains metallic behavior in the investigated pressure range up to 15 GPa.The hump-like anomaly in resistance around~130 K at ambient pressure disappears at P≥2 GPa.In the pressure range of 11–15 GPa we observed the gradual development of a shoulder-like anomaly in resistance at low temperatures,which evolves into a pronounced drop of resistance of 98%below 62 K at 15 GPa,reaching a temperature-independent resistance of 20μΩbelow 20 K.Similarly,this resistance anomaly can be progressively shifted to lower temperatures by applying external magnetic fields,resembling a typical superconducting transition.Measurements on sample 3 in the CAC reproduce the resistance drop at pressures above 10 GPa and realize zero resistance below 10 K at 15 GPa even though an unusual semiconducting-like behavior is retained in the normal state.Based on these results,we constructed a dome-shaped superconducting phase diagram and discuss some issues regarding the sample-dependent behaviors on pressure-ind
文摘Primary solidification phase and lamellar orientation are investigated in Ti-45Al-7Nb alloy at very high ratio of temperature gradient to growth rate （G/v） by a liquid-metal-cooled directionally solidified method. It shows that Ti-45Al-7Nb alloy solidifies with primary ct phase. Longitudinal （parallel to growth direction） microstructure shows that a dendrites in solid-liquid mushy zone are discontinuous and transverse mierostructure of a dendrites is worm-like feature. Growth direction of a phase is about 80° away from （0001）,a direction, and close to （1120） a direction. The corresponding lamellar orientation is aligned at the angle of about 10° to growth direction, which is consistent with a-dendrite growth direction according to Blackburn orientation relationship. Therefore, due to the altered growth direction of a phase, the lamellar orientation in Ti-45Al-7Nb alloy is controlled at the G/v ratio of 5 × 10^9 K.sm^-2.
基金supported by the Czech Science Foundation under the Grant No.15-01100Ssupported within the program of Czech Research Infrastructures(No.LM2011025)+2 种基金supported by the Grant Agency of the Charles University under the Project No.1332314supported by the Czech-Polish cooperation in the scope of Czech-Polish project7AMB14PL036(9004/R14/R15)European Regional Development Fund under the Infrastructure and Environment Programme
文摘The γ-U phase alloys can be retained down to low temperatures with less required alloying concentration by using the splat-cooling technique with a cooling rate better than 10^6 K/s. Doping with 15 at.% Mo, Pt, Pd, Nb leads to a stabilization of the cubic γ-U phase, while it requires much higher Zr concentrations （≥30 at.% Zr）. All U-T splats become superconducting with Tc in the range of 0.61-2.11 K. A good agreement of the experimentally observed specific-heat jump at Tc with that from BCS theory prediction was obtained for U-15 at.% Mo consisting of the γ-U phase with an ideal bcc A2 structure.
文摘The localized plastic flow auto-waves observed for the stages of easy glide and linear work hardening in a number of metals are considered. The propagation rates were determined expe- rimentally for the auto-waves in question with the aid of focused-image holography. The dispersion relation of quadratic form derived for localized plastic flow auto-waves and the dependencies of phase and group rates on wave number are discussed. A detailed comparison of the quantitative characteristics of phase and group waves has revealed that the two types of wave are closely related. An invariant is introduced for localized plastic flow phenomena occurring on the micro-and macro-scale levels in the deforming solid.
基金The work was financially supported by the National Natural Science Foundation of China (No.50501020 and 50395103)the Fun-damental Research Project of National Defense of China (No.A2720060295)+1 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars, the Ministry of Education of China (No.N6CJ0002)the New Century Excellent Person Supporting Project (No.NCET-05-870).]
文摘An analytical phase transformation model has been used to study the kinetics of crystallization of amorphous alloys sub- jected to either isothermal or isochronal anneals. The model has been applied to Mg82.3Cu17.7 and Pd40Cu30P20Ni10, employing iso- thermal and isochronal differential scanning calorimetry. Applying different combinations of nucleation and growth mechanisms to the same experiments, the nucleation and growth modes dominating the crystallization and the values for the corresponding kinetic parameters, including the constant activation energies for nucleation and growth, have been determined. Further, the influence of isothermal pre-annealing on subsequent isochronal crystallization kinetics, involving a gradual change of nucleation mode up to site saturation with increase of pre-annealing, can be analyzed.
