The structural stability of methane hydrate under pressure at room temperature was examined by both in-situ single-crystal and powder X-ray diffraction techniques on samples with structure types I, II, and H in diamon...The structural stability of methane hydrate under pressure at room temperature was examined by both in-situ single-crystal and powder X-ray diffraction techniques on samples with structure types I, II, and H in diamond-anvil ceils. The diffraction data for types II （slI） and H （sH） were refined to the known structures with space groups Fd3m and P63/mmc, respectively. Upon compression, sl methane hydrate transforms to the sll phase at 120 MPa, and then to the sH phase at 600 MPa. The slI methane hydrate was found to coexist locally with sI phase up to 500 MPa and with sH phase up to 600 MPa. The pure sH structure was found to be stable between 600 and 900 MPa. Methane hydrate decomposes at pressures above 3 GPa to form methane with the orientationally disordered Fm3m structure and ice VII （Pn3m）. The results highlight the role of guest （CH4）-host （H2O） interactions in the stabilization of the hydrate structures under pressure.展开更多
The amount of literature on both melting and thermal conductivity of iron at Earth’s core conditions is overwhelming and the discrepancies are very large.There is a broad range of experimental techniques each of whic...The amount of literature on both melting and thermal conductivity of iron at Earth’s core conditions is overwhelming and the discrepancies are very large.There is a broad range of experimental techniques each of which is flawed to a certain degree,which may explain the discrepancy.In this report,we present new data using a different method for determining the phase behavior and resistivity of iron in the laser-heated diamond cell by measuring the electrical resistance of both solid and liquid iron wires.The experiment avoids some of the major flaws of previous experiments,the most important of which is the detection of the onset of melting.These measurements confirm a shallow melting curve found earlier and the resistivity data imply a trend towards low thermal conductivity in the liquid outer core.展开更多
The lower mantle makes up more than a half of our planet’s volume. Mineralogical and petrological experiments on realistic bulk compositions under high pressure–temperature (P–T) conditions are essential for unders...The lower mantle makes up more than a half of our planet’s volume. Mineralogical and petrological experiments on realistic bulk compositions under high pressure–temperature (P–T) conditions are essential for understanding deep mantle processes. Such high P–T experiments are commonly conducted in a laser-heated diamond anvil cell, producing a multiphase assemblage consisting of 100 nm to submicron crystallite grains. The structures of these lower mantle phases often cannot be preserved upon pressure quenching;thus, in situ characterization is needed. The X-ray diffraction (XRD) pattern of such a multiphase assemblage usually displays a mixture of diffraction spots and rings as a result of the coarse grain size relative to the small X-ray beam size (3–5 lm) available at the synchrotron facilities. Severe peak overlapping from multiple phases renders the powder XRD method inadequate for indexing new phases and minor phases. Consequently, structure determination of new phases in a high P–T multiphase assemblage has been extremely difficult using conventional XRD techniques. Our recent development of multigrain XRD in high-pressure research has enabled the indexation of hundreds of individual crystallite grains simultaneously through the determination of crystallographic orientations for these individual grains. Once indexation is achieved, each grain can be treated as a single crystal. The combined crystallographic information from individual grains can be used to determine the crystal structures of new phases and minor phases simultaneously in a multiphase system. With this new development, we have opened up a new area of crystallography under the high P–T conditions of the deep lower mantle. This paper explains key challenges in studying multiphase systems and demonstrates the unique capabilities of high-pressure multigrain XRD through successful examples of its applications.展开更多
Diamond anvil cell techniques have been improved to allow access to the multimegabar ultrahigh-pressure region for exploring novel phenomena in condensedmatter.However,the onlyway to determine crystal structures of ma...Diamond anvil cell techniques have been improved to allow access to the multimegabar ultrahigh-pressure region for exploring novel phenomena in condensedmatter.However,the onlyway to determine crystal structures of materials above 100 GPa,namely,X-ray diffraction(XRD),especially for lowZ materials,remains nontrivial in the ultrahigh-pressure region,even with the availability of brilliant synchrotron X-ray sources.In thiswork,we performa systematic study,choosing hydrogen(the lowest X-ray scatterer)as the subject,to understand how to better perform XRD measurements of low Z materials at multimegabar pressures.The techniques that we have developed have been proved to be effective in measuring the crystal structure of solid hydrogen up to 254GPa at room temperature[C.Ji et al.,Nature 573,558–562(2019)].Wepresent our discoveries and experienceswith regard to several aspects of thiswork,namely,diamond anvil selection,sample configuration for ultrahigh-pressure XRDstudies,XRDdiagnostics for low Z materials,and related issues in data interpretation and pressure calibration.Webelieve that these methods can be readily extended to other low Z materials and can pave the way for studying the crystal structure of hydrogen at higher pressures,eventually testing structural models of metallic hydrogen.展开更多
Polyimide（PI） is a type of important membrane material. A soluble polymer was synthesized from 4,4′-（hexafluoroisopropylidene） diphthalic anhydride（6FDA） and 2,2-bis[4-（4-aminophenoxy） phenyl] hexafluoroprop...Polyimide（PI） is a type of important membrane material. A soluble polymer was synthesized from 4,4′-（hexafluoroisopropylidene） diphthalic anhydride（6FDA） and 2,2-bis[4-（4-aminophenoxy） phenyl] hexafluoropropane（BDAF） by the two-step polymerization method. The polymer was proved to be polyimide 6FDA-BDAF by the Fourier transform infrared（FT-IR）, the 1H-NMR and ^（19）F-NMR spectra. An asymmetric membrane was prepared with the synthesized polyimide 6FDA-BDAF, it was porous in the 50 μm height bulk and dense in a 3–5 μm height surface. The membrane was used to separate n-heptane/thiophene mixtures by pervaporation with sulfur（S） contents from 50 to 900 μg g^（–1）. The total flux was enlarged from 7.96 to 37.61 kg m^（–2） h^（–1） with temperature increasing from 50 to 90°C. The membrane＇s enrichments factor for thiophene were about 3.13 and dependent on the experimental conditions. The experimental results demonstrated that polyimide 6FDA-BDAF would be a potential membrane material for desulfurization and controlled release of the S-containing fertilizer.展开更多
Two kinds of glassy sulfurs are synthesized by thrapid compression method from liquid sulfur at temperatures below and above the X-transition point. The glassy sulfur has different colors and transparencies, depending...Two kinds of glassy sulfurs are synthesized by thrapid compression method from liquid sulfur at temperatures below and above the X-transition point. The glassy sulfur has different colors and transparencies, depending on temperature, which may inherit some structural information from the transition. Raman spectrum studies of these samples show that a large fraction of polymeric chains exist in the glassy sulfur, even in the one solidified from T 〈 Tλ. We find that a higher compression rate instead of a higher temperature of the parent liquid captures more polymeric chains. Pressure-induced glassy sulfur presents high thermal stability compared with temperature quenched glassy sulfur and could transform into liquid sulfur directly without crystallization through an abnormal exothermic melting course. High energy x-ray diffraction is utilized to study the local order of the pressure-induced glassy sulfur.展开更多
Recent reports of the superconductivity in hydrides of two different families(covalent lattice,as in SH3 and clathrate-type H-cages containing La and Y atoms,as in LaH10 and YH6)have revealed new families of high-Tc m...Recent reports of the superconductivity in hydrides of two different families(covalent lattice,as in SH3 and clathrate-type H-cages containing La and Y atoms,as in LaH10 and YH6)have revealed new families of high-Tc materials with Tc’s near room temperature values.These findings confirm earlier expectations that hydrides may have very high Tc’s due to the fact that light H atoms have very high vibrational frequencies,leading to high Tc values within the conventional Bardeen–Cooper–Schrieffer phonon mechanism of superconductivity.However,as is pointed out by Ashcroft,it is important to have the metallic hydrogen“alloyed”with the elements added to it.This concept of a metallic alloy containing a high concentration of metal-like hydrogen atoms has been instrumental in finding new high-Tc superhydrides.These new superhydride“roomtemperature”superconductors are stabilized only at very high pressures above 100 GPa,making the experimental search for their superconducting properties very difficult.We will review the current experimental and theoretical results for LaH10−x and YH6−x superhydrides.展开更多
The pressure effect on the crystalline structure of the I-II- V semiconductor Li（Zn,Mn）As ferromagnet is studied using in situ high-pressure x-ray diffraction and diamond anvil cell techniques. A phase transition st...The pressure effect on the crystalline structure of the I-II- V semiconductor Li（Zn,Mn）As ferromagnet is studied using in situ high-pressure x-ray diffraction and diamond anvil cell techniques. A phase transition starting at -11.6GPa is found. The space group of the high-pressure new phase is proposed as Pmca. Fitting with the Birch-Murnaghan equation of state, the bulk modulus B0 and its pressure derivative B0 of the ambient pressure structure with space group of F43m are B0 = 75.4 GPa and B0 = 4.3, respectively.展开更多
We have performed measurements of minerals based on the synchrotron source for single crystal and powder X-ray diffraction, inelastic scattering, spectroscopy and radiography by using diamond anvil cells. We investiga...We have performed measurements of minerals based on the synchrotron source for single crystal and powder X-ray diffraction, inelastic scattering, spectroscopy and radiography by using diamond anvil cells. We investigated the properties of iron （Fe）, iron-magnesium oxides （Fe, Mg）O, silica（SiO2）, iron-magnesium silicates （Fe, Mg）SiO3 under simulated high pressure-high temperature extreme conditions of the Earth＇s crust, upper mantle, low mantle, core-mantle boundary, outer core, and inner core. The results provide a new window on the investigation of the mineral properties at Earth＇s conditions.展开更多
Research on the melting phenomenon is the most challenging work in the high pressure/temperature field. Until now,large discrepancies still exist in the melting curve of iron, the most interesting and extensively stud...Research on the melting phenomenon is the most challenging work in the high pressure/temperature field. Until now,large discrepancies still exist in the melting curve of iron, the most interesting and extensively studied element in geoscience research. Here we present a summary about techniques detecting melting in the laser heating diamond anvil cell.展开更多
Podiform chromitites are generally lenticular bodies of massive to disseminated chromite typically hosted in mantle peridotites in ophiolites. Most such chromitites are surrounded by envelopes of dunite, a few centime...Podiform chromitites are generally lenticular bodies of massive to disseminated chromite typically hosted in mantle peridotites in ophiolites. Most such chromitites are surrounded by envelopes of dunite, a few centimeters to a few meters wide. Based on their textures and compositions, podiform chromitites have been interpreted as magmatic rocks formed as partial melting of mantle peridotite under low-pressure conditions in the upper mantle or by magma mingling and melt-rock reaction.展开更多
Xieite,a new mineral,occurs in the shock vein of the Suizhou meteorite.The mineral has an ortho-rhombic structure and its space group is Bbmm.The cell parameters are a = 9.462(6),b = 9.562(9),c = 2.916(1).The crystal-...Xieite,a new mineral,occurs in the shock vein of the Suizhou meteorite.The mineral has an ortho-rhombic structure and its space group is Bbmm.The cell parameters are a = 9.462(6),b = 9.562(9),c = 2.916(1).The crystal-chemical formula is(Fe0.87Mg0.13Mn0.01)1.01(Cr1.62Al0.25Ti0.08V0.02)1.97O4,or simply formula FeCr2O4.Stronger X-ray diffraction lines are [d(),I/Io]:(2.675,100),(2.389,20),(2.089,10),(1.953,90),(1.566,60),(1.439,15),(1.425,15),(1.337,40).Xieite is a high pressure polymorph of FeCr2O4 and formed by solid-state transformation of chromite under shock-induced high pressure and tem-perature,in association with other high-pressure minerals including ringwoodite,majorite,lingunite and tuite.The P-T condition for the formation of xieite is estimated to be 18―23 GPa and 1800―1950℃,respectively.Xieite has recently been approved by the Commission on New Minerals,Nomenclature and Classification of the International Mineralogical Association(IMA 2007-056).The mineral name,xieite,is named after Xiande Xie.展开更多
In this study, controlled-release fertilizers （CRFs） with five different nitrogen release periods were pre- pared by coating large urea particles with polyethylene （PE） membranes under various experimental conditi...In this study, controlled-release fertilizers （CRFs） with five different nitrogen release periods were pre- pared by coating large urea particles with polyethylene （PE） membranes under various experimental conditions. The preliminary and differential solubility rates, release periods, and membrane pore sizes of the obtained CRFs were measured using water immersion, scanning electron microscopy, and mercury porosimetry. For all CRF samples, the median pore diameters of the membranes were equal to 4.5-5.3 nm and pores with sizes smaller than 10 nm accounted for 86-96% of the total pore surface area. The obtained pore diameter distributions differed for the five studied types of CRF, having release periods of 1,2, 4, 6, and 8 months. Thus, for the CRFs with a 1-month release period, the maximum pore diameter reached a magnitude of 4000 nm, while this value did not exceed 30 nm for the CRFs with a release period of 8 months. Hence, we have established a relationship between the release period of CRFs and their effective maximum pore sizes.展开更多
This paper reviews the recent progress in the understanding of the dynamics of Pb(B_(1/2)B0_(1/2))O_(3)-type relaxor ferroelectrics using of broadband micro-Brillouin scattering spectroscopy,which covers a large frequ...This paper reviews the recent progress in the understanding of the dynamics of Pb(B_(1/2)B0_(1/2))O_(3)-type relaxor ferroelectrics using of broadband micro-Brillouin scattering spectroscopy,which covers a large frequency range from 1 to 1000 GHz by a tandem multi-pass FabryPerot interferometer.In contrast to Pb(B_(1/3)B0_(2/3))O_(3)-type relaxors,there is no frustration on the B-site of perovskite structure and the degree of order of B-site cations depends on heat treatment.Remarkable softening of sound velocity and an intense central peak are observed above the Curie temperature TC owing to the polarization°uctuations in polar nanoregions(PNRs).Unlike the Pb(B_(1/3)B0_(2/3))O_(3)relaxors,Pb(B_(1/2)B'_(1/2))O_(3)does not undergoes a typical diffuse phase transition without lead vacancies on A-site which enhances randomfields.For the(1-x)Pb(B_(1/2)B'_(1/2))O_(3-x)PbTiO_(3)solid solutions,the long range polar order increases as the PbTiO_(3)content increases.Nevertheless,a central peak owing to dynamic PNRs still remains even for the composition near the MPB,and a critical slowing down is clearly observed in the vicinity of TC.展开更多
As a route to improving the energy conversion of organic-inorganic hybrid-solar cells, we have tested the performance of poly(phenylene vinylene)(PPV), poly(2,5-thienylene vinylene)(PWTV) polymers and CdTe nanocrystal...As a route to improving the energy conversion of organic-inorganic hybrid-solar cells, we have tested the performance of poly(phenylene vinylene)(PPV), poly(2,5-thienylene vinylene)(PWTV) polymers and CdTe nanocrystal devices produced via aqueous-processing. It is found that small differences in the conformation of the sensitizer lead to dramatic effects on the solar cell efficiency. Using a combination of UV-Vis absorption spectroscopy and first-principles non-adiabatic molecular dynamics(NAMD) based on time-dependent density-functional theory(TDDFT), PPV is found to have a longer electron injection and recombination time despite seeming to have a better energy alignment with the substrate, which leads to a higher devices performance than PWTV. The present results shed new light on the understanding of organic-inorganic hybrid-solar cells and will trigger further experimental and theoretical investigations.展开更多
基金HPSynC is supported as part of EFree,an EnergyFrontier Research Center funded by the U.S.Department of Energy(DOE),Office of Science, Office of Basic Energy Sciences(BES) under Award Number DE-SC0001057HPCAT is supported by CIW,CDAC,UNLV and LLNL through funding from DOE-NNSA,DOE-BES and NSFAPS is supported by DOE-BES,under Contract No.DE-AC02-06CH 11357
文摘The structural stability of methane hydrate under pressure at room temperature was examined by both in-situ single-crystal and powder X-ray diffraction techniques on samples with structure types I, II, and H in diamond-anvil ceils. The diffraction data for types II （slI） and H （sH） were refined to the known structures with space groups Fd3m and P63/mmc, respectively. Upon compression, sl methane hydrate transforms to the sll phase at 120 MPa, and then to the sH phase at 600 MPa. The slI methane hydrate was found to coexist locally with sI phase up to 500 MPa and with sH phase up to 600 MPa. The pure sH structure was found to be stable between 600 and 900 MPa. Methane hydrate decomposes at pressures above 3 GPa to form methane with the orientationally disordered Fm3m structure and ice VII （Pn3m）. The results highlight the role of guest （CH4）-host （H2O） interactions in the stabilization of the hydrate structures under pressure.
基金supported by the National Science Foundation (No. 1248553)
文摘The amount of literature on both melting and thermal conductivity of iron at Earth’s core conditions is overwhelming and the discrepancies are very large.There is a broad range of experimental techniques each of which is flawed to a certain degree,which may explain the discrepancy.In this report,we present new data using a different method for determining the phase behavior and resistivity of iron in the laser-heated diamond cell by measuring the electrical resistance of both solid and liquid iron wires.The experiment avoids some of the major flaws of previous experiments,the most important of which is the detection of the onset of melting.These measurements confirm a shallow melting curve found earlier and the resistivity data imply a trend towards low thermal conductivity in the liquid outer core.
基金the National Natural Science Foundation of China (41574080 and U1530402).
文摘The lower mantle makes up more than a half of our planet’s volume. Mineralogical and petrological experiments on realistic bulk compositions under high pressure–temperature (P–T) conditions are essential for understanding deep mantle processes. Such high P–T experiments are commonly conducted in a laser-heated diamond anvil cell, producing a multiphase assemblage consisting of 100 nm to submicron crystallite grains. The structures of these lower mantle phases often cannot be preserved upon pressure quenching;thus, in situ characterization is needed. The X-ray diffraction (XRD) pattern of such a multiphase assemblage usually displays a mixture of diffraction spots and rings as a result of the coarse grain size relative to the small X-ray beam size (3–5 lm) available at the synchrotron facilities. Severe peak overlapping from multiple phases renders the powder XRD method inadequate for indexing new phases and minor phases. Consequently, structure determination of new phases in a high P–T multiphase assemblage has been extremely difficult using conventional XRD techniques. Our recent development of multigrain XRD in high-pressure research has enabled the indexation of hundreds of individual crystallite grains simultaneously through the determination of crystallographic orientations for these individual grains. Once indexation is achieved, each grain can be treated as a single crystal. The combined crystallographic information from individual grains can be used to determine the crystal structures of new phases and minor phases simultaneously in a multiphase system. With this new development, we have opened up a new area of crystallography under the high P–T conditions of the deep lower mantle. This paper explains key challenges in studying multiphase systems and demonstrates the unique capabilities of high-pressure multigrain XRD through successful examples of its applications.
基金This research was supported by the National Natural Science Foundation of China under Award No.U1930401the Department of Energy(DOE),Office of Basic Energy Science,Division of Materials Sciences and Engineering under Award No.DE-FG02-99ER45775
文摘Diamond anvil cell techniques have been improved to allow access to the multimegabar ultrahigh-pressure region for exploring novel phenomena in condensedmatter.However,the onlyway to determine crystal structures of materials above 100 GPa,namely,X-ray diffraction(XRD),especially for lowZ materials,remains nontrivial in the ultrahigh-pressure region,even with the availability of brilliant synchrotron X-ray sources.In thiswork,we performa systematic study,choosing hydrogen(the lowest X-ray scatterer)as the subject,to understand how to better perform XRD measurements of low Z materials at multimegabar pressures.The techniques that we have developed have been proved to be effective in measuring the crystal structure of solid hydrogen up to 254GPa at room temperature[C.Ji et al.,Nature 573,558–562(2019)].Wepresent our discoveries and experienceswith regard to several aspects of thiswork,namely,diamond anvil selection,sample configuration for ultrahigh-pressure XRDstudies,XRDdiagnostics for low Z materials,and related issues in data interpretation and pressure calibration.Webelieve that these methods can be readily extended to other low Z materials and can pave the way for studying the crystal structure of hydrogen at higher pressures,eventually testing structural models of metallic hydrogen.
基金support from the Key Technology R&D Program of China(2011BAD11B05)the National Nonprofit Institute Research Grant of Chinese Academy of Agricultural Sciences(2011-28,2013-17)+3 种基金supported by the National Basic Research Program of China(973 Program,2003CB615701)the National Natural Science Foundation of China(20576059,20676067,31572204)the China Petroleum&Chemical Corporation(SINOPEC Foundation,X505002)the China National Petroleum Corporation(CNPC)InnovationFoundation(05051143)
文摘Polyimide（PI） is a type of important membrane material. A soluble polymer was synthesized from 4,4′-（hexafluoroisopropylidene） diphthalic anhydride（6FDA） and 2,2-bis[4-（4-aminophenoxy） phenyl] hexafluoropropane（BDAF） by the two-step polymerization method. The polymer was proved to be polyimide 6FDA-BDAF by the Fourier transform infrared（FT-IR）, the 1H-NMR and ^（19）F-NMR spectra. An asymmetric membrane was prepared with the synthesized polyimide 6FDA-BDAF, it was porous in the 50 μm height bulk and dense in a 3–5 μm height surface. The membrane was used to separate n-heptane/thiophene mixtures by pervaporation with sulfur（S） contents from 50 to 900 μg g^（–1）. The total flux was enlarged from 7.96 to 37.61 kg m^（–2） h^（–1） with temperature increasing from 50 to 90°C. The membrane＇s enrichments factor for thiophene were about 3.13 and dependent on the experimental conditions. The experimental results demonstrated that polyimide 6FDA-BDAF would be a potential membrane material for desulfurization and controlled release of the S-containing fertilizer.
基金supported by the Joint Funds of the National Natural Science Foundation of China(Grant No.U1530402)the National Natural Science Foundation of China(Grant No.11004163)+2 种基金the Fundamental Research Funds for the Central Universities,China(Grant No.2682014ZT31)the Department of Energy National Nuclear Security Administration(Grant No.DE-NA0001974)the Department of Energy Basic Energy Sciences(Grant Nos.DE-FG02-99ER45775and DE-AC02-06CH11357)
文摘Two kinds of glassy sulfurs are synthesized by thrapid compression method from liquid sulfur at temperatures below and above the X-transition point. The glassy sulfur has different colors and transparencies, depending on temperature, which may inherit some structural information from the transition. Raman spectrum studies of these samples show that a large fraction of polymeric chains exist in the glassy sulfur, even in the one solidified from T 〈 Tλ. We find that a higher compression rate instead of a higher temperature of the parent liquid captures more polymeric chains. Pressure-induced glassy sulfur presents high thermal stability compared with temperature quenched glassy sulfur and could transform into liquid sulfur directly without crystallization through an abnormal exothermic melting course. High energy x-ray diffraction is utilized to study the local order of the pressure-induced glassy sulfur.
基金V.S.acknowledges support fromthe Thousand Talent Program by the State Council of the People’s Republic of China.Portions of this work were performed at GeoSoilEnviroCARS(The University of Chicago,Sector 13)Advanced Photon Source(APS),Argonne National Laboratory.GeoSoilEnviroCARS is supported by the National Science Foundation-Earth Sciences(Grant No.EAR-1634415)Department of Energy-GeoSciences(Grant No.DE-FG02-94ER14466).This research used resources from the Advanced Photon Source,a U.S.Department of Energy(DOE)Office of the Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No.DEAC02-06CH11357.I.T.and A.G.acknowledge support from the Ministry of Science and Higher Education of the Russian Federation within the State assignment of the FSRC“Crystallography and Photonics”of RAS in part of the high-pressure structural experiments and from the Russian Science Foundation(Project No.19-12-00414)in part of the high-pressure studies of superconductivity.A.G.acknowledges the use of the facilities of the Center for Collective Use“AcceleratorCenter for NeutronResearch of the Structure of Substance and Nuclear Medicine”of the INR RAS.
文摘Recent reports of the superconductivity in hydrides of two different families(covalent lattice,as in SH3 and clathrate-type H-cages containing La and Y atoms,as in LaH10 and YH6)have revealed new families of high-Tc materials with Tc’s near room temperature values.These findings confirm earlier expectations that hydrides may have very high Tc’s due to the fact that light H atoms have very high vibrational frequencies,leading to high Tc values within the conventional Bardeen–Cooper–Schrieffer phonon mechanism of superconductivity.However,as is pointed out by Ashcroft,it is important to have the metallic hydrogen“alloyed”with the elements added to it.This concept of a metallic alloy containing a high concentration of metal-like hydrogen atoms has been instrumental in finding new high-Tc superhydrides.These new superhydride“roomtemperature”superconductors are stabilized only at very high pressures above 100 GPa,making the experimental search for their superconducting properties very difficult.We will review the current experimental and theoretical results for LaH10−x and YH6−x superhydrides.
基金Supported by the National Natural Science Foundation and the Ministry of Science and Technology of Chinathe National Natural Science Foundation of China under Grant No U1530402+3 种基金the U.S. Department of Energy of Office of Science under Grant No DE-AC02-06CH11357the DOE-NNSA under Grant No DE-NA0001974the DOE-BES under Grant No DE-FG02-99ER45775the Instrumentation Funding of National Science Foundation
文摘The pressure effect on the crystalline structure of the I-II- V semiconductor Li（Zn,Mn）As ferromagnet is studied using in situ high-pressure x-ray diffraction and diamond anvil cell techniques. A phase transition starting at -11.6GPa is found. The space group of the high-pressure new phase is proposed as Pmca. Fitting with the Birch-Murnaghan equation of state, the bulk modulus B0 and its pressure derivative B0 of the ambient pressure structure with space group of F43m are B0 = 75.4 GPa and B0 = 4.3, respectively.
文摘We have performed measurements of minerals based on the synchrotron source for single crystal and powder X-ray diffraction, inelastic scattering, spectroscopy and radiography by using diamond anvil cells. We investigated the properties of iron （Fe）, iron-magnesium oxides （Fe, Mg）O, silica（SiO2）, iron-magnesium silicates （Fe, Mg）SiO3 under simulated high pressure-high temperature extreme conditions of the Earth＇s crust, upper mantle, low mantle, core-mantle boundary, outer core, and inner core. The results provide a new window on the investigation of the mineral properties at Earth＇s conditions.
文摘Research on the melting phenomenon is the most challenging work in the high pressure/temperature field. Until now,large discrepancies still exist in the melting curve of iron, the most interesting and extensively studied element in geoscience research. Here we present a summary about techniques detecting melting in the laser heating diamond anvil cell.
文摘Podiform chromitites are generally lenticular bodies of massive to disseminated chromite typically hosted in mantle peridotites in ophiolites. Most such chromitites are surrounded by envelopes of dunite, a few centimeters to a few meters wide. Based on their textures and compositions, podiform chromitites have been interpreted as magmatic rocks formed as partial melting of mantle peridotite under low-pressure conditions in the upper mantle or by magma mingling and melt-rock reaction.
基金National Natural Science Foundation of China (Grant Nos. 40672035 and 40272028)the Chinese Academy of Sciences (Grant No. KJCX2-SW-N20)
文摘Xieite,a new mineral,occurs in the shock vein of the Suizhou meteorite.The mineral has an ortho-rhombic structure and its space group is Bbmm.The cell parameters are a = 9.462(6),b = 9.562(9),c = 2.916(1).The crystal-chemical formula is(Fe0.87Mg0.13Mn0.01)1.01(Cr1.62Al0.25Ti0.08V0.02)1.97O4,or simply formula FeCr2O4.Stronger X-ray diffraction lines are [d(),I/Io]:(2.675,100),(2.389,20),(2.089,10),(1.953,90),(1.566,60),(1.439,15),(1.425,15),(1.337,40).Xieite is a high pressure polymorph of FeCr2O4 and formed by solid-state transformation of chromite under shock-induced high pressure and tem-perature,in association with other high-pressure minerals including ringwoodite,majorite,lingunite and tuite.The P-T condition for the formation of xieite is estimated to be 18―23 GPa and 1800―1950℃,respectively.Xieite has recently been approved by the Commission on New Minerals,Nomenclature and Classification of the International Mineralogical Association(IMA 2007-056).The mineral name,xieite,is named after Xiande Xie.
基金This work described above was financially supported by National Key R＆D Program of China （No. 2017YFD0200703）, and the General Program of Natural Science Foundation of China （grant number 31572204）. The authors would like to thank Hongying Cai from the Department of Chemical Engineering of Tsinghua Univer- sity for his help with SEM observations and Dongwu Chang from the Department of Thermal Energy Engineering of Tsinghua University for assistance with MP measurements.
文摘In this study, controlled-release fertilizers （CRFs） with five different nitrogen release periods were pre- pared by coating large urea particles with polyethylene （PE） membranes under various experimental conditions. The preliminary and differential solubility rates, release periods, and membrane pore sizes of the obtained CRFs were measured using water immersion, scanning electron microscopy, and mercury porosimetry. For all CRF samples, the median pore diameters of the membranes were equal to 4.5-5.3 nm and pores with sizes smaller than 10 nm accounted for 86-96% of the total pore surface area. The obtained pore diameter distributions differed for the five studied types of CRF, having release periods of 1,2, 4, 6, and 8 months. Thus, for the CRFs with a 1-month release period, the maximum pore diameter reached a magnitude of 4000 nm, while this value did not exceed 30 nm for the CRFs with a release period of 8 months. Hence, we have established a relationship between the release period of CRFs and their effective maximum pore sizes.
文摘This paper reviews the recent progress in the understanding of the dynamics of Pb(B_(1/2)B0_(1/2))O_(3)-type relaxor ferroelectrics using of broadband micro-Brillouin scattering spectroscopy,which covers a large frequency range from 1 to 1000 GHz by a tandem multi-pass FabryPerot interferometer.In contrast to Pb(B_(1/3)B0_(2/3))O_(3)-type relaxors,there is no frustration on the B-site of perovskite structure and the degree of order of B-site cations depends on heat treatment.Remarkable softening of sound velocity and an intense central peak are observed above the Curie temperature TC owing to the polarization°uctuations in polar nanoregions(PNRs).Unlike the Pb(B_(1/3)B0_(2/3))O_(3)relaxors,Pb(B_(1/2)B'_(1/2))O_(3)does not undergoes a typical diffuse phase transition without lead vacancies on A-site which enhances randomfields.For the(1-x)Pb(B_(1/2)B'_(1/2))O_(3-x)PbTiO_(3)solid solutions,the long range polar order increases as the PbTiO_(3)content increases.Nevertheless,a central peak owing to dynamic PNRs still remains even for the composition near the MPB,and a critical slowing down is clearly observed in the vicinity of TC.
基金supported by the National Natural Science Foundation of China(51433003)the National Basic Research Program of China(2014CB643503)
文摘As a route to improving the energy conversion of organic-inorganic hybrid-solar cells, we have tested the performance of poly(phenylene vinylene)(PPV), poly(2,5-thienylene vinylene)(PWTV) polymers and CdTe nanocrystal devices produced via aqueous-processing. It is found that small differences in the conformation of the sensitizer lead to dramatic effects on the solar cell efficiency. Using a combination of UV-Vis absorption spectroscopy and first-principles non-adiabatic molecular dynamics(NAMD) based on time-dependent density-functional theory(TDDFT), PPV is found to have a longer electron injection and recombination time despite seeming to have a better energy alignment with the substrate, which leads to a higher devices performance than PWTV. The present results shed new light on the understanding of organic-inorganic hybrid-solar cells and will trigger further experimental and theoretical investigations.
