The electrochemical reduction of carbon dioxide offers a sound and economically viable technology for the electrification and decarbonization of the chemical and fuel industries.In this technology,an electrocatalytic ...The electrochemical reduction of carbon dioxide offers a sound and economically viable technology for the electrification and decarbonization of the chemical and fuel industries.In this technology,an electrocatalytic material and renewable energy-generated electricity drive the conversion of carbon dioxide into high-value chemicals and carbon-neutral fuels.Over the past few years,single-atom catalysts have been intensively studied as they could provide near-unity atom utilization and unique catalytic performance.Single-atom catalysts have become one of the state-of-the-art catalyst materials for the electrochemical reduction of carbon dioxide into carbon monoxide.However,it remains a challenge for single-atom catalysts to facilitate the efficient conversion of carbon dioxide into products beyond carbon monoxide.In this review,we summarize and present important findings and critical insights from studies on the electrochemical carbon dioxide reduction reaction into hydrocarbons and oxygenates using single-atom catalysts.It is hoped that this review gives a thorough recapitulation and analysis of the science behind the catalysis of carbon dioxide into more reduced products through singleatom catalysts so that it can be a guide for future research and development on catalysts with industry-ready performance for the electrochemical reduction of carbon dioxide into high-value chemicals and carbon-neutral fuels.展开更多
Al-doped LiVPO4F cathode materials LiAlxV1-xPO4F were prepared by two-step reactions based on a car-bothermal reduction （CTR） process. The properties of the Al-doped LiVPO4F were investigated by X-ray diffraction （...Al-doped LiVPO4F cathode materials LiAlxV1-xPO4F were prepared by two-step reactions based on a car-bothermal reduction （CTR） process. The properties of the Al-doped LiVPO4F were investigated by X-ray diffraction （XRD）,scanning electron microscopy （SEM）,and electrochemical measurements. XRD studies show that the Al-doped LiVPO4F has the same triclinic structure （space group p-↑1 ） as the undoped LiVPO4F. The SEM images exhibit that the particle size of Al-doped LiVPO4F is smaller than that of the undoped LiVPO4F and that the smallest particle size is only about 1 μm. The Al-doped LiVPO4F was evaluated as a cathode material for secondary lithium batteries,and exhibited an improved reversibility and cycleability,which may be attributed to the addition of Al^3＋ ion by stabilizing the triclinic structure.展开更多
A potential 4.2 V cathode material LiVPO4F for lithium batteries was prepared by two-step reaction method based on a carbon-thermal reduction （CTR） process. Firstly, V2O5, NH4H2PO4 and acetylene black are reacted un...A potential 4.2 V cathode material LiVPO4F for lithium batteries was prepared by two-step reaction method based on a carbon-thermal reduction （CTR） process. Firstly, V2O5, NH4H2PO4 and acetylene black are reacted under an Ar atmosphere to yield VPO4. The transition-metal reduction is facilitated by the CTR based on C→CO transition. These CTR conditions favor stabilization of the vanadium as V^3＋ as well as leaving residual carbon, which is useful in the subsequent electrode processing. Secondly, VPO4 reacts with ElF to yield LiVPO4F product. The property of the LiVPO4F was investigated by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and electrochemical measurement. XRD studies show that LiVPO4F synthesized has triclinic structure（space group p I ）, isostructural with the naturally occurring mineral tavorite, EiFePO4-OH. SEM image exhibits that the particle size is about 2μm together with homogenous distribution. Electrochemical test shows that the initial discharge capacity of LiVPO4F powder is 119 mA·h/g at the rate of 0.2C with an average discharge voltage of 4.2V （vs Ei/Li^＋）, and the capacity retains 89 mA·h/g after 30 cycles.展开更多
As an essential renewable mineral resource,mollusk shells can be used as handicrafts,building materials,adsor-bents,etc.However,there are few reports on the wear resistance of their structures.The Vicker’s hardness a...As an essential renewable mineral resource,mollusk shells can be used as handicrafts,building materials,adsor-bents,etc.However,there are few reports on the wear resistance of their structures.The Vicker’s hardness and friction,and wear resistance of different microstructures in mollusk shells were comparatively studied in the pre-sent work.The hardness of prismatic structures is lower than that of cross-lamellar and nacreous structures.How-ever,the experimental results of sliding tests indicate that the prismatic structure exhibits the best anti-wear ability compared with foliated,crossed-lamellar,and nacreous structures.The anti-wear and hardness do not present a positive correlation,as the wear resistance properties of different microstructures in mollusk shells are governed jointly by organic matrix,structural arrangement,and basic building block actions.The present researchfindings are expected to provide fundamental insight into the design of renewable bionic materials with high wear resistance.展开更多
Cholesteric liquid crystals（CLCs） have recently sparked an enormous amount of interest in the development of soft matter materials due to their unique ability to self-organize into a helical supra-molecular architec...Cholesteric liquid crystals（CLCs） have recently sparked an enormous amount of interest in the development of soft matter materials due to their unique ability to self-organize into a helical supra-molecular architecture and their excellent selective reflection of light based on the Bragg relationship.Nowadays,by the virtue of building the self-organized nanostructures with pitch gradient or non-uniform pitch distribution,extensive work has already been performed to obtain CLC films with a broad reflection band.Based on authors＇ many years＇ research experience,this critical review systematically summarizes the physical and optical background of the CLCs with broadband reflection characteristics,methods to obtain broadband reflection of CLCs,as well as the application in the field of intelligent optical modulation materials.Combined with the research status and the advantages in the field,the important basic and applied scientific problems in the research direction are also introduced.展开更多
Magnesium(Mg) alloys, as the lightest metal engineering materials, have broad application prospects.However, the strength and ductility of traditional Mg alloys are still relativity low and difficult to improve simult...Magnesium(Mg) alloys, as the lightest metal engineering materials, have broad application prospects.However, the strength and ductility of traditional Mg alloys are still relativity low and difficult to improve simultaneously.Refining grain size via the deformation process based on the grain boundary strengthening and the transition of deformation mechanisms is one of the feasible strategies to prepare Mg alloys with high strength and high ductility.In this review, the effects of grain size on the strength and ductility of Mg alloys are summarized, and fine-grained Mg alloys with high strength and high ductility developed by various severe plastic deformation technologies and improved traditional deformation technologies are introduced.Although some achievements have been made, the effects of grain size on various Mg alloys are rarely discussed systematically and some key mechanisms are unclear or lack direct microscopic evidence.This review can be used as a reference for further development of high-performance fine-grained Mg alloys.展开更多
The uniform layered LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries was prepared by using （Ni1/3Co1/3Mn1/3）C2O4 as precursor synthesized via oxalate co-precipitation method in air. The effects of calc...The uniform layered LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries was prepared by using （Ni1/3Co1/3Mn1/3）C2O4 as precursor synthesized via oxalate co-precipitation method in air. The effects of calcination temperature and time on the structure and electrochemical properties of the LiNi1/3Co1/3Mn1/3O2 were systemically studied. XRD results revealed that the optimal calcination conditions to prepare the layered LiNi1/3Co1/3Mn1/302 were 950℃ for 15 h. Electrochemical measurement showed that the sample prepared under the such conditions has the highest initial discharge capacity of 160.8 mAh/g and the smallest irreversible capacity loss of 13.5% as well as stable cycling performance at a constant current density of 30 mA/g between 2.5 and 4.3 V versus Li at room temperature.展开更多
Spherical carbonyl iron(Fe)powders were coated with magnesioferrite(MgFe2O4)insulating coating layer and then mixed with epoxy-modified silicone resin(ESR).Soft magnetic composites(SMCs)were fabricated by compaction o...Spherical carbonyl iron(Fe)powders were coated with magnesioferrite(MgFe2O4)insulating coating layer and then mixed with epoxy-modified silicone resin(ESR).Soft magnetic composites(SMCs)were fabricated by compaction of the coated powders and annealing treatment.Transmission electron microscopy(TEM),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),X-ray diffractometry(XRD)and X-ray photoelectron spectroscopy(XPS)revealed that the MgFe2O4 layer was coated on the surface of the iron powders.The magnetic properties of SMCs were determined using a vibrating sample magnetometer and an auto testing system for magnetic materials.The results showed that the SMCs prepared at 800 MPa and 550℃ exhibited a significant core loss of 167.5 W/kg at 100 kHz and 50 mT.展开更多
The as-formed and post-deformed microstructures in both electroformed and spin-formed copper liners of shaped charge were studied by optical microscopy(OM), electron backscattering Kikuchi patterns(EBSP) technique and...The as-formed and post-deformed microstructures in both electroformed and spin-formed copper liners of shaped charge were studied by optical microscopy(OM), electron backscattering Kikuchi patterns(EBSP) technique and transmission electron microscopy(TEM). The deformation was carried out at an ultra-high strain rate. OM analysis shows that the initial grains of the electroformed copper liner are finer than those of the spin-formed copper liners. Meanwhile, EBSP analysis reveals that the fiber texture exists in the electroformed copper liners, whereas there is no texture observed in the spin-formed copper liners before deformation. Having undergone high-strain-rate deformation the grains in the recovered slugs, which are transformed from both the electroformed and spin-formed copper liners, all become small. TEM observations of the above two kinds of post-deformed specimens show the existence of cellular structures characterized by tangled dislocations and subgrain boundaries consisting of dislocation arrays. These experimental results indicate that dynamic recovery and recrystallization play an important role in the high-strain-rate deformation process.展开更多
In this paper, a series of chiral non-symmetrical liquid crystals （nBA-chol） consisting of a cholesteryl ester moiety as chiral entity and a biphenyl aromatic core with different terminal alkyl chain has been synthe...In this paper, a series of chiral non-symmetrical liquid crystals （nBA-chol） consisting of a cholesteryl ester moiety as chiral entity and a biphenyl aromatic core with different terminal alkyl chain has been synthesized and investigated for their liquid crystalline properties. Effects of numbers of methylene units in the terminal alkyl chain on the phase transition temperatures and on the temperature-dependent pitch lengths of the chiral liquid crystals have been studied. The long terminal alkyl chain tends to exhibit smectic A mesophases. The pitch lengths of the cholesteric mesophases of the chiral liquid crystals decrease with increasing temperature and with increasing numbers of methylene units in the terminal alkyl chain, respectively.展开更多
Two series of novel cholesteryl-containing H-bonded liquid crystals were prepared through facile self-assembly between cholesteryl isonicotinate （proton acceptor） exhibiting a monotropic cholesteric phase, and the 4...Two series of novel cholesteryl-containing H-bonded liquid crystals were prepared through facile self-assembly between cholesteryl isonicotinate （proton acceptor） exhibiting a monotropic cholesteric phase, and the 4-alkoxy-benzoic acid or 4-alkoxy cinnamic acid （proton donor）. It was found that the increase of the conjugate length as well as the terminal length can contribute to enhance the interaction of molecules and thus significantly influenced the thermal behaviors of H-bonded LCs. The cholesteric reflection spectra of the induced mesogenic complexes were located in the visible region with the color tuneable thermo-sensitivity, which could be used for display application.展开更多
The microstructure in the electroformed copper liners of shaped charges prepared with different electrolytes was studied by Scanning Electron Microscopy （SEM） and Electron Backscattering Kikuchi Pattern （EBSP） met...The microstructure in the electroformed copper liners of shaped charges prepared with different electrolytes was studied by Scanning Electron Microscopy （SEM） and Electron Backscattering Kikuchi Pattern （EBSP） methods. SEM observations revealed the existence of columnar grains in electroformed copper liners of shaped charges formed by electrolyte without any additive and the average grain size is about 3 μm. When an additive is introduced to the electrolyte, the grains formed in the copper liners become equiaxed and finer. EBSP results show that the columnar grain grown during electroformation has the most preferential growth direction, whereas a micro-texture does not exit in the specimen prepared by electrolyte with the additive. Further, explosive detonation deformation experiments show that penetration depth is dramatically improved when the electroformed copper liners of shaped charges exhibit equiaxed grains.展开更多
To explore the specimen size effect of mechanical behavior of ultrafine-grained(UFG)materials with different structures,UFG Al sheets processed by equal channel angular pressing(ECAP)were selected as target materials ...To explore the specimen size effect of mechanical behavior of ultrafine-grained(UFG)materials with different structures,UFG Al sheets processed by equal channel angular pressing(ECAP)were selected as target materials and the dependency of tensile behavior on sheet thickness(t)was systematically investigated.The strength and ductility of ECAPed UFG Al sheets were improved synchronously as t increased from 0.2 to 0.7 mm,and then no apparent change occurred when t reached to 0.7 and 1.0 mm.The corresponding microstructure evolved from dislocation networks in equiaxed grains into the walls and subgrains and finally into the dominated cells in elongated grains or subgrains.Meanwhile,dense shear lines(SLs)and shear bands(SBs)were clearly observed and microvoids and cracks were initiated along SBs with the increase of t.These observations indicated that the plastic deformation of UFG Al sheets was jointly controlled by shear banding,dislocation sliding,and grain-boundary sliding.Furthermore,the propagation of SBs became difficult as t increased.Finally,the obtained results were discussed and compared with those of annealed UFG Al and UFG Cu.展开更多
Visible photoluminescence （PL） has been observed from rare earth （Tm, Sm and Dy）-doped AlN films grown by radio-frequency magnetron reactive sputtering. X-ray diffraction indicates that the films are c-axis-orient...Visible photoluminescence （PL） has been observed from rare earth （Tm, Sm and Dy）-doped AlN films grown by radio-frequency magnetron reactive sputtering. X-ray diffraction indicates that the films are c-axis-oriented hexagonal wurtzite type structure with an average crystal size of about 80-110 nm. Room-temperature PL spectra indicate that the blue emission is due to the transition of ^1D2 to ^3F4 and ^1G4 to ^3H6 intra 4f electron of Tm^3＋, the yellow emissions of AlN：Sm are due to ^4G5/2 to the ^6HJ （J=5/2, 7/2, 9/2, 11/2） and the reddish emissions of AlN：Dy correspond to the ^4F9/2 to ^6HJ （J=5/2, 13/2, 11/2 and 9/2） and ^6Fll/2 transitions.展开更多
For 18 months, a newly developed low alloy weathering steel has been exposed in two coastal sites （Qingdao in the north China, Wanning in the south China）. The different corrosion behaviors of the exposed side and t...For 18 months, a newly developed low alloy weathering steel has been exposed in two coastal sites （Qingdao in the north China, Wanning in the south China）. The different corrosion behaviors of the exposed side and the underside of the samples were characterized by X-ray diffraetion （XRD）, polarization curve, electrochemical impedance spectroscopy （EIS）, scanning electron microscopy （SEM）, and N2 adsorption approach. It was found that the samples exhibited higher corrosion rate in Wanning than that in Qingdao. The underside of the samples corrodes more seriously than the exposed side in Qingdao, whereas the result in Wanning is just the reverse. The protection performance of rust layers mainly depends on its compactness and the enrichment of Cu and Cr is a secondary causation. The different compactness of rust layers in the exposed side and the underside originates from different corrosion conditions of the two sides.展开更多
Microstructure of as-cast and extruded Mg-8Li-1Al-1Y alloy specimens was analyzed with OM,SEM and XRD.Results show that as-cast specimens are composed of α phase(Mg),β phase(Li) and rod-like Al2Y compound.In the ext...Microstructure of as-cast and extruded Mg-8Li-1Al-1Y alloy specimens was analyzed with OM,SEM and XRD.Results show that as-cast specimens are composed of α phase(Mg),β phase(Li) and rod-like Al2Y compound.In the extruded specimens,the microstructure is refined and the β phase has the effect of coordination during deformation.After extruding process,the Al2Y compound distributes evenly in the extruding direction.The results of mechanical properties tests show that the strength and elongation are both improved after extruding deformation.展开更多
The title compound [2-（2,6-dioxacyclohexyl）-5-methoxylphenols]2 was synthesized by the reaction of 2-hydroxyl-3-methoxylbenzaldehyde and 1,3-propanediol in the presence of DMF-DMS adduct and characterized by IR spec...The title compound [2-（2,6-dioxacyclohexyl）-5-methoxylphenols]2 was synthesized by the reaction of 2-hydroxyl-3-methoxylbenzaldehyde and 1,3-propanediol in the presence of DMF-DMS adduct and characterized by IR spectrum, UV-Vis spectrum and X-ray crystallography. The title compound belongs to monoclinic, space group P21 with a = 9.8967（10）, b = 8.2240（9）, c = 13.3654（14） A^°, β= 90.016（2）°, C11H14O4, Mr = 210.22, V = 1087.8（2）A^°3, Z = 4, Dc = 1.284 Mg/m^3, F（000） = 448,μ = 0.098 mm^-1, the final R = 0.0300 and wR = 0.0761 for 2070 observed reflections with I 〉 2σ（I）. The molecules are connected via intermolecular O-H…O hydrogen bonds into a 2D network structure. Moreover, theoretical investigations of the title compound with HF/6-31G（d） method were performed, and its stability, frontier molecular orbital composition and Mulliken charge distribution were also discussed. The compound is a bis-molecule. The two molecules stay together and could not be separated. Two crystallographically independent molecules exist in an asymmetric unit. The bond lengths and bond angles of the two molecules are slightly different with each other.展开更多
Two series of novel tolane-type liquid crystals （LCs） comprising of hydrogen-bonded organic acids were synthesized. The formation of dimerized H-bond LCs was confirmed by IR spectroscopy, and mesomorphic properties ...Two series of novel tolane-type liquid crystals （LCs） comprising of hydrogen-bonded organic acids were synthesized. The formation of dimerized H-bond LCs was confirmed by IR spectroscopy, and mesomorphic properties of the LCs were investigated by differential scanning calorimetry （DSC） and polarizing optical microscopy （POM）. It was found that the end groups of the liquid crystals as well as the unsaturated rigid core had effect on the mesomorphic properties.展开更多
The trimeric phenylenevinylene with the symmetrical chiral end-groups （ChTPV） was synthesized. The liquid crystalline and luminescent properties of the ChTPV have been studied by differential scanning calorimetry （...The trimeric phenylenevinylene with the symmetrical chiral end-groups （ChTPV） was synthesized. The liquid crystalline and luminescent properties of the ChTPV have been studied by differential scanning calorimetry （DSC）, polarized optical microscopy （POM）, absorption and photoluminescence spectra. The results indicated that the ChTPV exhibits mesophase over a wide temperature range and a typical optical texture of smectic phase. In contrast with the spectra of the solution, that of the film showed blue-shift in maximal absorption and red-shift in maximal emission due to H-type aggregation with parallel alignment of the TPV transition dipole moment.展开更多
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIP)(NRF,2021R1C1C1013953,2022K1A4A7A04094394,2022K1A4A7A04095890)。
文摘The electrochemical reduction of carbon dioxide offers a sound and economically viable technology for the electrification and decarbonization of the chemical and fuel industries.In this technology,an electrocatalytic material and renewable energy-generated electricity drive the conversion of carbon dioxide into high-value chemicals and carbon-neutral fuels.Over the past few years,single-atom catalysts have been intensively studied as they could provide near-unity atom utilization and unique catalytic performance.Single-atom catalysts have become one of the state-of-the-art catalyst materials for the electrochemical reduction of carbon dioxide into carbon monoxide.However,it remains a challenge for single-atom catalysts to facilitate the efficient conversion of carbon dioxide into products beyond carbon monoxide.In this review,we summarize and present important findings and critical insights from studies on the electrochemical carbon dioxide reduction reaction into hydrocarbons and oxygenates using single-atom catalysts.It is hoped that this review gives a thorough recapitulation and analysis of the science behind the catalysis of carbon dioxide into more reduced products through singleatom catalysts so that it can be a guide for future research and development on catalysts with industry-ready performance for the electrochemical reduction of carbon dioxide into high-value chemicals and carbon-neutral fuels.
文摘Al-doped LiVPO4F cathode materials LiAlxV1-xPO4F were prepared by two-step reactions based on a car-bothermal reduction （CTR） process. The properties of the Al-doped LiVPO4F were investigated by X-ray diffraction （XRD）,scanning electron microscopy （SEM）,and electrochemical measurements. XRD studies show that the Al-doped LiVPO4F has the same triclinic structure （space group p-↑1 ） as the undoped LiVPO4F. The SEM images exhibit that the particle size of Al-doped LiVPO4F is smaller than that of the undoped LiVPO4F and that the smallest particle size is only about 1 μm. The Al-doped LiVPO4F was evaluated as a cathode material for secondary lithium batteries,and exhibited an improved reversibility and cycleability,which may be attributed to the addition of Al^3＋ ion by stabilizing the triclinic structure.
基金Project(50302016) supported by the National Natural Science Foundation of China
文摘A potential 4.2 V cathode material LiVPO4F for lithium batteries was prepared by two-step reaction method based on a carbon-thermal reduction （CTR） process. Firstly, V2O5, NH4H2PO4 and acetylene black are reacted under an Ar atmosphere to yield VPO4. The transition-metal reduction is facilitated by the CTR based on C→CO transition. These CTR conditions favor stabilization of the vanadium as V^3＋ as well as leaving residual carbon, which is useful in the subsequent electrode processing. Secondly, VPO4 reacts with ElF to yield LiVPO4F product. The property of the LiVPO4F was investigated by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and electrochemical measurement. XRD studies show that LiVPO4F synthesized has triclinic structure（space group p I ）, isostructural with the naturally occurring mineral tavorite, EiFePO4-OH. SEM image exhibits that the particle size is about 2μm together with homogenous distribution. Electrochemical test shows that the initial discharge capacity of LiVPO4F powder is 119 mA·h/g at the rate of 0.2C with an average discharge voltage of 4.2V （vs Ei/Li^＋）, and the capacity retains 89 mA·h/g after 30 cycles.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51902043)the Fundamental Research Funds for the Central Universities(Grant Nos.N2102007,N2102002,and N2202011)This work was also partially supported by the National Natural Science Foundation of China(Grant Nos.51871048 and 52171108).
文摘As an essential renewable mineral resource,mollusk shells can be used as handicrafts,building materials,adsor-bents,etc.However,there are few reports on the wear resistance of their structures.The Vicker’s hardness and friction,and wear resistance of different microstructures in mollusk shells were comparatively studied in the pre-sent work.The hardness of prismatic structures is lower than that of cross-lamellar and nacreous structures.How-ever,the experimental results of sliding tests indicate that the prismatic structure exhibits the best anti-wear ability compared with foliated,crossed-lamellar,and nacreous structures.The anti-wear and hardness do not present a positive correlation,as the wear resistance properties of different microstructures in mollusk shells are governed jointly by organic matrix,structural arrangement,and basic building block actions.The present researchfindings are expected to provide fundamental insight into the design of renewable bionic materials with high wear resistance.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51573006,51573003,51203003,51303008,51302006,51402006,51272026,and 51273022)the Major Project of Beijing Science and Technology Program,China(Grant Nos.Z151100003315023 and Z141100003814011)the Fok Ying Tung Education Foundation,China(Grant No.142009)
文摘Cholesteric liquid crystals（CLCs） have recently sparked an enormous amount of interest in the development of soft matter materials due to their unique ability to self-organize into a helical supra-molecular architecture and their excellent selective reflection of light based on the Bragg relationship.Nowadays,by the virtue of building the self-organized nanostructures with pitch gradient or non-uniform pitch distribution,extensive work has already been performed to obtain CLC films with a broad reflection band.Based on authors＇ many years＇ research experience,this critical review systematically summarizes the physical and optical background of the CLCs with broadband reflection characteristics,methods to obtain broadband reflection of CLCs,as well as the application in the field of intelligent optical modulation materials.Combined with the research status and the advantages in the field,the important basic and applied scientific problems in the research direction are also introduced.
基金supported by the National Natural Science Foundation of China (Nos.51871069 and 52071093)the Fundamental Research Funds for the Central Universities (No.3072020CF1009)+2 种基金the Science and Technology Innovation Major Project of Ningbo City, China (No.2019B10103)the Domain Foundation of Equipment Advance Research of 13th Five-year Plan (No.61409220118)the Open Funds of the State Key Laboratory of Rare Earth Resource Utilization (No.RERU2020008)。
文摘Magnesium(Mg) alloys, as the lightest metal engineering materials, have broad application prospects.However, the strength and ductility of traditional Mg alloys are still relativity low and difficult to improve simultaneously.Refining grain size via the deformation process based on the grain boundary strengthening and the transition of deformation mechanisms is one of the feasible strategies to prepare Mg alloys with high strength and high ductility.In this review, the effects of grain size on the strength and ductility of Mg alloys are summarized, and fine-grained Mg alloys with high strength and high ductility developed by various severe plastic deformation technologies and improved traditional deformation technologies are introduced.Although some achievements have been made, the effects of grain size on various Mg alloys are rarely discussed systematically and some key mechanisms are unclear or lack direct microscopic evidence.This review can be used as a reference for further development of high-performance fine-grained Mg alloys.
基金financially supported by the Natural Science Foundation of Guangxi Province, China (No. GKZ0832256)
文摘The uniform layered LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion batteries was prepared by using （Ni1/3Co1/3Mn1/3）C2O4 as precursor synthesized via oxalate co-precipitation method in air. The effects of calcination temperature and time on the structure and electrochemical properties of the LiNi1/3Co1/3Mn1/3O2 were systemically studied. XRD results revealed that the optimal calcination conditions to prepare the layered LiNi1/3Co1/3Mn1/302 were 950℃ for 15 h. Electrochemical measurement showed that the sample prepared under the such conditions has the highest initial discharge capacity of 160.8 mAh/g and the smallest irreversible capacity loss of 13.5% as well as stable cycling performance at a constant current density of 30 mA/g between 2.5 and 4.3 V versus Li at room temperature.
基金Project(2016YFB0700302)supported by the National Key Research and Development Program of ChinaProjects(51862030,51563020)supported by the National Natural Science Foundation of China。
文摘Spherical carbonyl iron(Fe)powders were coated with magnesioferrite(MgFe2O4)insulating coating layer and then mixed with epoxy-modified silicone resin(ESR).Soft magnetic composites(SMCs)were fabricated by compaction of the coated powders and annealing treatment.Transmission electron microscopy(TEM),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),X-ray diffractometry(XRD)and X-ray photoelectron spectroscopy(XPS)revealed that the MgFe2O4 layer was coated on the surface of the iron powders.The magnetic properties of SMCs were determined using a vibrating sample magnetometer and an auto testing system for magnetic materials.The results showed that the SMCs prepared at 800 MPa and 550℃ exhibited a significant core loss of 167.5 W/kg at 100 kHz and 50 mT.
基金Project(571014569) supported by the National Natural Science Foundation of China
文摘The as-formed and post-deformed microstructures in both electroformed and spin-formed copper liners of shaped charge were studied by optical microscopy(OM), electron backscattering Kikuchi patterns(EBSP) technique and transmission electron microscopy(TEM). The deformation was carried out at an ultra-high strain rate. OM analysis shows that the initial grains of the electroformed copper liner are finer than those of the spin-formed copper liners. Meanwhile, EBSP analysis reveals that the fiber texture exists in the electroformed copper liners, whereas there is no texture observed in the spin-formed copper liners before deformation. Having undergone high-strain-rate deformation the grains in the recovered slugs, which are transformed from both the electroformed and spin-formed copper liners, all become small. TEM observations of the above two kinds of post-deformed specimens show the existence of cellular structures characterized by tangled dislocations and subgrain boundaries consisting of dislocation arrays. These experimental results indicate that dynamic recovery and recrystallization play an important role in the high-strain-rate deformation process.
基金Financial support from National Natural Science foundation(No.20674005)National High Technology"863"Program of China(No.2006AA03Z108)National Science and Technology Supporting Item(No.2006BAI03A09)
文摘In this paper, a series of chiral non-symmetrical liquid crystals （nBA-chol） consisting of a cholesteryl ester moiety as chiral entity and a biphenyl aromatic core with different terminal alkyl chain has been synthesized and investigated for their liquid crystalline properties. Effects of numbers of methylene units in the terminal alkyl chain on the phase transition temperatures and on the temperature-dependent pitch lengths of the chiral liquid crystals have been studied. The long terminal alkyl chain tends to exhibit smectic A mesophases. The pitch lengths of the cholesteric mesophases of the chiral liquid crystals decrease with increasing temperature and with increasing numbers of methylene units in the terminal alkyl chain, respectively.
基金supported by National Natural Science foundation(No.20674005)Program of National High Technology 863 program of China(No.2006AA03Z108)Science and Technology Program of Beijing,China (No.Y0405004040121)
文摘Two series of novel cholesteryl-containing H-bonded liquid crystals were prepared through facile self-assembly between cholesteryl isonicotinate （proton acceptor） exhibiting a monotropic cholesteric phase, and the 4-alkoxy-benzoic acid or 4-alkoxy cinnamic acid （proton donor）. It was found that the increase of the conjugate length as well as the terminal length can contribute to enhance the interaction of molecules and thus significantly influenced the thermal behaviors of H-bonded LCs. The cholesteric reflection spectra of the induced mesogenic complexes were located in the visible region with the color tuneable thermo-sensitivity, which could be used for display application.
基金financially supported by the National Natural Science Foundation of China (No.59971008)
文摘The microstructure in the electroformed copper liners of shaped charges prepared with different electrolytes was studied by Scanning Electron Microscopy （SEM） and Electron Backscattering Kikuchi Pattern （EBSP） methods. SEM observations revealed the existence of columnar grains in electroformed copper liners of shaped charges formed by electrolyte without any additive and the average grain size is about 3 μm. When an additive is introduced to the electrolyte, the grains formed in the copper liners become equiaxed and finer. EBSP results show that the columnar grain grown during electroformation has the most preferential growth direction, whereas a micro-texture does not exit in the specimen prepared by electrolyte with the additive. Further, explosive detonation deformation experiments show that penetration depth is dramatically improved when the electroformed copper liners of shaped charges exhibit equiaxed grains.
基金financially supported by the National Natural Science Foundation of China (Nos. 51571058 and 51871048)the Open Foundation of Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, China (No. ATM20170001)
文摘To explore the specimen size effect of mechanical behavior of ultrafine-grained(UFG)materials with different structures,UFG Al sheets processed by equal channel angular pressing(ECAP)were selected as target materials and the dependency of tensile behavior on sheet thickness(t)was systematically investigated.The strength and ductility of ECAPed UFG Al sheets were improved synchronously as t increased from 0.2 to 0.7 mm,and then no apparent change occurred when t reached to 0.7 and 1.0 mm.The corresponding microstructure evolved from dislocation networks in equiaxed grains into the walls and subgrains and finally into the dominated cells in elongated grains or subgrains.Meanwhile,dense shear lines(SLs)and shear bands(SBs)were clearly observed and microvoids and cracks were initiated along SBs with the increase of t.These observations indicated that the plastic deformation of UFG Al sheets was jointly controlled by shear banding,dislocation sliding,and grain-boundary sliding.Furthermore,the propagation of SBs became difficult as t increased.Finally,the obtained results were discussed and compared with those of annealed UFG Al and UFG Cu.
基金Project supported by the National Natural Science Foundation of China （Grant No 50372082）.
文摘Visible photoluminescence （PL） has been observed from rare earth （Tm, Sm and Dy）-doped AlN films grown by radio-frequency magnetron reactive sputtering. X-ray diffraction indicates that the films are c-axis-oriented hexagonal wurtzite type structure with an average crystal size of about 80-110 nm. Room-temperature PL spectra indicate that the blue emission is due to the transition of ^1D2 to ^3F4 and ^1G4 to ^3H6 intra 4f electron of Tm^3＋, the yellow emissions of AlN：Sm are due to ^4G5/2 to the ^6HJ （J=5/2, 7/2, 9/2, 11/2） and the reddish emissions of AlN：Dy correspond to the ^4F9/2 to ^6HJ （J=5/2, 13/2, 11/2 and 9/2） and ^6Fll/2 transitions.
基金supported by National Key Basic Research and Development Programof China (No.2004CB619102).
文摘For 18 months, a newly developed low alloy weathering steel has been exposed in two coastal sites （Qingdao in the north China, Wanning in the south China）. The different corrosion behaviors of the exposed side and the underside of the samples were characterized by X-ray diffraetion （XRD）, polarization curve, electrochemical impedance spectroscopy （EIS）, scanning electron microscopy （SEM）, and N2 adsorption approach. It was found that the samples exhibited higher corrosion rate in Wanning than that in Qingdao. The underside of the samples corrodes more seriously than the exposed side in Qingdao, whereas the result in Wanning is just the reverse. The protection performance of rust layers mainly depends on its compactness and the enrichment of Cu and Cr is a secondary causation. The different compactness of rust layers in the exposed side and the underside originates from different corrosion conditions of the two sides.
文摘Microstructure of as-cast and extruded Mg-8Li-1Al-1Y alloy specimens was analyzed with OM,SEM and XRD.Results show that as-cast specimens are composed of α phase(Mg),β phase(Li) and rod-like Al2Y compound.In the extruded specimens,the microstructure is refined and the β phase has the effect of coordination during deformation.After extruding process,the Al2Y compound distributes evenly in the extruding direction.The results of mechanical properties tests show that the strength and elongation are both improved after extruding deformation.
基金Supported by the Postgraduate Foundation of Taishan University (No. Y07-2-16)
文摘The title compound [2-（2,6-dioxacyclohexyl）-5-methoxylphenols]2 was synthesized by the reaction of 2-hydroxyl-3-methoxylbenzaldehyde and 1,3-propanediol in the presence of DMF-DMS adduct and characterized by IR spectrum, UV-Vis spectrum and X-ray crystallography. The title compound belongs to monoclinic, space group P21 with a = 9.8967（10）, b = 8.2240（9）, c = 13.3654（14） A^°, β= 90.016（2）°, C11H14O4, Mr = 210.22, V = 1087.8（2）A^°3, Z = 4, Dc = 1.284 Mg/m^3, F（000） = 448,μ = 0.098 mm^-1, the final R = 0.0300 and wR = 0.0761 for 2070 observed reflections with I 〉 2σ（I）. The molecules are connected via intermolecular O-H…O hydrogen bonds into a 2D network structure. Moreover, theoretical investigations of the title compound with HF/6-31G（d） method were performed, and its stability, frontier molecular orbital composition and Mulliken charge distribution were also discussed. The compound is a bis-molecule. The two molecules stay together and could not be separated. Two crystallographically independent molecules exist in an asymmetric unit. The bond lengths and bond angles of the two molecules are slightly different with each other.
基金supported by National Natural Science foundation(No.20674005)Program of National High Technology 863 program of China(No.2006AA03Z108)+1 种基金National Key Technology Program(No.2007BAE31B00)Key Program for Panel Display of 863 program of China(No.2008AA03A318)
文摘Two series of novel tolane-type liquid crystals （LCs） comprising of hydrogen-bonded organic acids were synthesized. The formation of dimerized H-bond LCs was confirmed by IR spectroscopy, and mesomorphic properties of the LCs were investigated by differential scanning calorimetry （DSC） and polarizing optical microscopy （POM）. It was found that the end groups of the liquid crystals as well as the unsaturated rigid core had effect on the mesomorphic properties.
基金supported by the National Science Foundation(No.20674005)the major project of Ministry Education of the People's Republic of China(No.104187).
文摘The trimeric phenylenevinylene with the symmetrical chiral end-groups （ChTPV） was synthesized. The liquid crystalline and luminescent properties of the ChTPV have been studied by differential scanning calorimetry （DSC）, polarized optical microscopy （POM）, absorption and photoluminescence spectra. The results indicated that the ChTPV exhibits mesophase over a wide temperature range and a typical optical texture of smectic phase. In contrast with the spectra of the solution, that of the film showed blue-shift in maximal absorption and red-shift in maximal emission due to H-type aggregation with parallel alignment of the TPV transition dipole moment.
