Al-1.0%Sc-1.0%Zr （mass fraction） master alloy was prepared at different cooling rates. The morphology and thermodynamics data of the primary particles of the master alloy were investigated by X-ray diffraction （XRD...Al-1.0%Sc-1.0%Zr （mass fraction） master alloy was prepared at different cooling rates. The morphology and thermodynamics data of the primary particles of the master alloy were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and differential scanning calorimetry （DSC）. It shows that the primary particles are dendrite-shaped particles comprised of several attached small cubic, cusped-cubic or crucifer shape particles at slow cooling rate. However, the primary particles are separated with crucifer shape at intermediate cooling rate, and they are cubic with cusped-cubic shape at high cooling rate. Meanwhile, the separated and attached particles present AlaSc/AlaZr1-xScx core-shell structure. The formation mechanism of the structure was systematically investigated by a mathematical model.展开更多
The electronic packaging shell with high silicon carbide aluminum-base composites was prepared by semi-solid thixoforming technique. The flow characteristic of the Si C particulate was analyzed. The microstructures of...The electronic packaging shell with high silicon carbide aluminum-base composites was prepared by semi-solid thixoforming technique. The flow characteristic of the Si C particulate was analyzed. The microstructures of different parts of the shell were observed by scanning electron microscopy and optical microscopy, and the thermophysical and mechanical properties of the shell were tested. The results show that there exists the segregation phenomenon between the Si C particulate and the liquid phase during thixoforming, the liquid phase flows from the shell, and the Si C particles accumulate at the bottom of the shell. The volume fraction of Si C decreases gradually from the bottom to the walls. Accordingly, the thermal conductivities of bottom center and walls are 178 and 164 W·m-1·K-1, the coefficients of thermal expansion(CTE) are 8.2×10-6 and 12.6×10-6 K-1, respectively. The flexural strength decreases slightly from 437 to 347 MPa. The microstructures and properties of the shell show gradient distribution.展开更多
In this paper,the possibility of the monatomic chain (MC) formation for ZnO material was studied by molecular dynamics (MD) simulation.The process of MC formation and the effects of temperature,strain rate and size we...In this paper,the possibility of the monatomic chain (MC) formation for ZnO material was studied by molecular dynamics (MD) simulation.The process of MC formation and the effects of temperature,strain rate and size were studied extensively.The tensile process can be divided to be five stages and the ZnO diatomic chain (DC) can be found.The MD results show that most atoms in MC came from the original surface of ZnO nanowires (NWs).Temperature and strain rate are two important factors affecting the process,and both high temperature and low strain rate in a certain range would be beneficial to the formation of DC.Moreover,the effects of strain rate and temperature could attribute to the Arrhenius model and the energy release mechanism.Furthermore,multi-shell structure was found for the samples under tensile strain and the layer-layer distance was about 3.Our studies based on density functional theory showed that the most stable structure of ZnO DC was confirmed to be linear,and the I-V curve was also got using ATK.展开更多
The Upper Carboniferous in northern Xinjiang, China was formed in a post-collisional depression and collapsed structural setting. Within the Upper Carboniferous, volcanic rocks and source rocks alternate over a wide r...The Upper Carboniferous in northern Xinjiang, China was formed in a post-collisional depression and collapsed structural setting. Within the Upper Carboniferous, volcanic rocks and source rocks alternate over a wide region. At the end of the Carboniferous, these layers were uplifted by plate collisions and subsequently weathered and leached. Volcanic weathering and leaching led to the establishment of weathered crusts that can be divided into five layers. Corrosion and crumble zones in these layers form favorable reservoirs. Volcanic weathering crust formed in sub-aerially exposed paleogeomorphic areas; the five relatively continuous layers are generally preserved in paleogeomorphic lowland and slope regions, but the upper soil layer is usually absent in structurally higher parts of the rock record. The thickness of the weathered layer has a positive nonlinear ex- ponential relationship to the duration of weathering and leaching, and the dynamic equilibrium time of weathered crust is about 36.3 Ma. The thickest weathered layer （~450 m） is located in fracture zones. Weathered crusts are possible from a range of volcanic rocks with different lithologies, given sufficient time for weathering and leaching. The combination of volcanic weathered crust and source rocks results in three types of hydrocarbon accumulation models： （1） sequences of volcanic weathered crust interbedded with source rocks, （2） a quasi-layered weathered volcanic core located above source rocks, and （3） volcanic rocks associated with pectinate unconformities adjacent to source rocks. Each of these three types has the potential to form a giant stratigraphic reservoir of volcanic weathered crust. This knowledge has changed the traditional exploration model of searching for favorable lithologic and lithofacies zones in volcanic rocks, and has changed the viewpoint that the Carboniferous does not have the genetic potential to be the basement of the basin in northern Xinjiang. The concepts developed here are of great scientific significance and application for focusing oil and gas exploration on volcanic weathered crust. As such, the Paleozoic volcanic weathered crust in the midwestern part of China may possibly contain large-scale stratigraphic reservoirs and thus could be a new oil and gas exploration target in the future.展开更多
ZnO:Cu/ZnO core/shell nanocrystals are synthesized by a two-step solution-phase process. The morphology, structure and optical properties of the samples are detected by scanning electron microscopy, Raman, absorption ...ZnO:Cu/ZnO core/shell nanocrystals are synthesized by a two-step solution-phase process. The morphology, structure and optical properties of the samples are detected by scanning electron microscopy, Raman, absorption and luminescence spectroscopy. The increase of particle size confirms the growth of ZnO shell. The segregation of CuO phase observed in ZnO: Cu core is not detected in ZnO:Cu/ZnO core/shell nanocrystals from Raman spectra. It is suggested that some Cu ions can be segregated from ZnO nanocrystals, and the separated Cu ions can be incorporated inside ZnO shell after the growth of ZnO shell. The visible emission mechanism is discussed in detail, and the photoluminescence analysis indicates that the core/shell structure helps to eliminate the surface-related emission.展开更多
We report a unique shell margin that differed from the usual shell structure of Pinctada fucata.We observed empty organic envelopes in the prismatic layer and the formation of the nacreous layer in the shell margin.Al...We report a unique shell margin that differed from the usual shell structure of Pinctada fucata.We observed empty organic envelopes in the prismatic layer and the formation of the nacreous layer in the shell margin.All the characteristics of the growing margin indicated that the shell was growing rapidly.To explain this anomaly,we propose the concept of "jumping development".During jumping development,the center of growth in the bivalve shell jumps forward over a short time interval when the position of the mantle changes.Jumping development explains the unusual structure of the anomalous shell and the development of annual growth lines in typical shells.Annual growth lines are the result of a discontinuity in the shell microstructure induced by jumping development.展开更多
Trivalent lanthanide(Ln^(3+))-doped luminescent nanoparticles(NPs)have been extensively investigated as deep-tissue-penetration visual bioimaging agents owing to their exceptional upconversion and near-infrared(NIR)lu...Trivalent lanthanide(Ln^(3+))-doped luminescent nanoparticles(NPs)have been extensively investigated as deep-tissue-penetration visual bioimaging agents owing to their exceptional upconversion and near-infrared(NIR)luminescence upon irradiation of NIR light.However,in most cases,the power density of irradiation used for in vivo biological imaging is much higher than that of the reported maximum permissible exposure(MPE)value of NIR light,which inevitably does great damage to the living organisms under study and thus impedes the plausible clinical applications.Herein,by using a facile syringe pump-aided shell epitaxial growth method,we construct for the first time a new class of Ln^(3+)-doped KMgF_(3):Yb/Er@KMgF_(3)core-shell NPs that can be activated by utilizing a 980-nm xenon lamp or diode laser with an ultralow excitation power density down to 0.08 mW cm^(−2),a value that is approximately 4 orders of magnitude lower than the MPE value set by the American National Standards Institute(ANSI)for safe bioimaging in vivo.By combining the comparative spectroscopic investigations with atomic-resolved spherical aberration corrected transmission electron microscopy(AC-TEM)characterization,we find that the reduced crystallographic defects are the primary cause underlying such an ultralow-power-excitable feature of the KMgF_(3):Yb/Er@KMgF_(3)core-shell NPs.And,by the same token,the resultant KMgF_(3):Yb/Er@KMgF_(3)core-shell NPs also exhibit an anomalous thermo-enhanced photoluminescence(PL)behavior coupled with an excellent photothermal stability that cannot occur in other Ln^(3+)-doped core-shell NPs.These findings described here unambiguously pave a new way to prepare high-quality Ln^(3+)-doped luminescent NPs with desirable ultralow-power-excitable capability and photothermal stability for future biomedical applications.展开更多
基金Project(2012CB619503)supported by the National Basic Research Program of ChinaProject(2013AA031001)supported by the National High-tech Research and Development Program of ChinaProject(2012DFA50630)supported by the International Science and Technology Cooperation Program of China
文摘Al-1.0%Sc-1.0%Zr （mass fraction） master alloy was prepared at different cooling rates. The morphology and thermodynamics data of the primary particles of the master alloy were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and differential scanning calorimetry （DSC）. It shows that the primary particles are dendrite-shaped particles comprised of several attached small cubic, cusped-cubic or crucifer shape particles at slow cooling rate. However, the primary particles are separated with crucifer shape at intermediate cooling rate, and they are cubic with cusped-cubic shape at high cooling rate. Meanwhile, the separated and attached particles present AlaSc/AlaZr1-xScx core-shell structure. The formation mechanism of the structure was systematically investigated by a mathematical model.
文摘The electronic packaging shell with high silicon carbide aluminum-base composites was prepared by semi-solid thixoforming technique. The flow characteristic of the Si C particulate was analyzed. The microstructures of different parts of the shell were observed by scanning electron microscopy and optical microscopy, and the thermophysical and mechanical properties of the shell were tested. The results show that there exists the segregation phenomenon between the Si C particulate and the liquid phase during thixoforming, the liquid phase flows from the shell, and the Si C particles accumulate at the bottom of the shell. The volume fraction of Si C decreases gradually from the bottom to the walls. Accordingly, the thermal conductivities of bottom center and walls are 178 and 164 W·m-1·K-1, the coefficients of thermal expansion(CTE) are 8.2×10-6 and 12.6×10-6 K-1, respectively. The flexural strength decreases slightly from 437 to 347 MPa. The microstructures and properties of the shell show gradient distribution.
基金supported by the National Natural Science Foundation of China (Grant No.60936001)
文摘In this paper,the possibility of the monatomic chain (MC) formation for ZnO material was studied by molecular dynamics (MD) simulation.The process of MC formation and the effects of temperature,strain rate and size were studied extensively.The tensile process can be divided to be five stages and the ZnO diatomic chain (DC) can be found.The MD results show that most atoms in MC came from the original surface of ZnO nanowires (NWs).Temperature and strain rate are two important factors affecting the process,and both high temperature and low strain rate in a certain range would be beneficial to the formation of DC.Moreover,the effects of strain rate and temperature could attribute to the Arrhenius model and the energy release mechanism.Furthermore,multi-shell structure was found for the samples under tensile strain and the layer-layer distance was about 3.Our studies based on density functional theory showed that the most stable structure of ZnO DC was confirmed to be linear,and the I-V curve was also got using ATK.
基金supported by National S&T Major Project (Grant No. 2008ZX05001)Major Brainstorm Project of CNPC-provided Financial Aid (Grant No. 06-01A-01-01)
文摘The Upper Carboniferous in northern Xinjiang, China was formed in a post-collisional depression and collapsed structural setting. Within the Upper Carboniferous, volcanic rocks and source rocks alternate over a wide region. At the end of the Carboniferous, these layers were uplifted by plate collisions and subsequently weathered and leached. Volcanic weathering and leaching led to the establishment of weathered crusts that can be divided into five layers. Corrosion and crumble zones in these layers form favorable reservoirs. Volcanic weathering crust formed in sub-aerially exposed paleogeomorphic areas; the five relatively continuous layers are generally preserved in paleogeomorphic lowland and slope regions, but the upper soil layer is usually absent in structurally higher parts of the rock record. The thickness of the weathered layer has a positive nonlinear ex- ponential relationship to the duration of weathering and leaching, and the dynamic equilibrium time of weathered crust is about 36.3 Ma. The thickest weathered layer （~450 m） is located in fracture zones. Weathered crusts are possible from a range of volcanic rocks with different lithologies, given sufficient time for weathering and leaching. The combination of volcanic weathered crust and source rocks results in three types of hydrocarbon accumulation models： （1） sequences of volcanic weathered crust interbedded with source rocks, （2） a quasi-layered weathered volcanic core located above source rocks, and （3） volcanic rocks associated with pectinate unconformities adjacent to source rocks. Each of these three types has the potential to form a giant stratigraphic reservoir of volcanic weathered crust. This knowledge has changed the traditional exploration model of searching for favorable lithologic and lithofacies zones in volcanic rocks, and has changed the viewpoint that the Carboniferous does not have the genetic potential to be the basement of the basin in northern Xinjiang. The concepts developed here are of great scientific significance and application for focusing oil and gas exploration on volcanic weathered crust. As such, the Paleozoic volcanic weathered crust in the midwestern part of China may possibly contain large-scale stratigraphic reservoirs and thus could be a new oil and gas exploration target in the future.
基金supported by the National Natural Science Foundation of China (Nos.60877029,10904109,60977035 and 60907021)the Natural Science Foundation of Tianjin (No.09JCYBJC01400)the Tianjin Key Subject for Materials Physics and Chemistry
文摘ZnO:Cu/ZnO core/shell nanocrystals are synthesized by a two-step solution-phase process. The morphology, structure and optical properties of the samples are detected by scanning electron microscopy, Raman, absorption and luminescence spectroscopy. The increase of particle size confirms the growth of ZnO shell. The segregation of CuO phase observed in ZnO: Cu core is not detected in ZnO:Cu/ZnO core/shell nanocrystals from Raman spectra. It is suggested that some Cu ions can be segregated from ZnO nanocrystals, and the separated Cu ions can be incorporated inside ZnO shell after the growth of ZnO shell. The visible emission mechanism is discussed in detail, and the photoluminescence analysis indicates that the core/shell structure helps to eliminate the surface-related emission.
基金supported by the National Natural Science Foundation of China (Grant Nos. U0831001 and 40876068)the National High Technology Research and Development Program of China (Grant Nos. 2010CB126405 and 2010AA09Z405)
文摘We report a unique shell margin that differed from the usual shell structure of Pinctada fucata.We observed empty organic envelopes in the prismatic layer and the formation of the nacreous layer in the shell margin.All the characteristics of the growing margin indicated that the shell was growing rapidly.To explain this anomaly,we propose the concept of "jumping development".During jumping development,the center of growth in the bivalve shell jumps forward over a short time interval when the position of the mantle changes.Jumping development explains the unusual structure of the anomalous shell and the development of annual growth lines in typical shells.Annual growth lines are the result of a discontinuity in the shell microstructure induced by jumping development.
基金supported by the Fund of Fujian Science&Technology Innovation Laboratory for Optoelectronic Information(2020ZZ114)the Key Research Program of Frontier Science CAS(QYZDY-SSW-SLH025)+1 种基金the National Natural Science Foundation of China(21731006 and 21871256)the Fund of Advanced Energy Science and Technology Guangdong Laboratory(DJLTN0200/DJLTN0240)。
文摘Trivalent lanthanide(Ln^(3+))-doped luminescent nanoparticles(NPs)have been extensively investigated as deep-tissue-penetration visual bioimaging agents owing to their exceptional upconversion and near-infrared(NIR)luminescence upon irradiation of NIR light.However,in most cases,the power density of irradiation used for in vivo biological imaging is much higher than that of the reported maximum permissible exposure(MPE)value of NIR light,which inevitably does great damage to the living organisms under study and thus impedes the plausible clinical applications.Herein,by using a facile syringe pump-aided shell epitaxial growth method,we construct for the first time a new class of Ln^(3+)-doped KMgF_(3):Yb/Er@KMgF_(3)core-shell NPs that can be activated by utilizing a 980-nm xenon lamp or diode laser with an ultralow excitation power density down to 0.08 mW cm^(−2),a value that is approximately 4 orders of magnitude lower than the MPE value set by the American National Standards Institute(ANSI)for safe bioimaging in vivo.By combining the comparative spectroscopic investigations with atomic-resolved spherical aberration corrected transmission electron microscopy(AC-TEM)characterization,we find that the reduced crystallographic defects are the primary cause underlying such an ultralow-power-excitable feature of the KMgF_(3):Yb/Er@KMgF_(3)core-shell NPs.And,by the same token,the resultant KMgF_(3):Yb/Er@KMgF_(3)core-shell NPs also exhibit an anomalous thermo-enhanced photoluminescence(PL)behavior coupled with an excellent photothermal stability that cannot occur in other Ln^(3+)-doped core-shell NPs.These findings described here unambiguously pave a new way to prepare high-quality Ln^(3+)-doped luminescent NPs with desirable ultralow-power-excitable capability and photothermal stability for future biomedical applications.
