Nanocrystalline powder of LaF3 was synthesized by a method of direct precipitation from water solution. Particle size and shape of LaF3 nanocrystalline powder was analysed with TEM. Particles were mainly spherical wit...Nanocrystalline powder of LaF3 was synthesized by a method of direct precipitation from water solution. Particle size and shape of LaF3 nanocrystalline powder was analysed with TEM. Particles were mainly spherical with narrow particle size distribution （10 20 nm）. The average particle size analysed with XRD is 16.7 nm. Nano-LaF3 bulk material was prepared by compacting the powder to 1 GPa at room temperature and a vacuum of 10^-4 Pa. The ionic conductivity of nano-LaF3 bulk material was studied with complex impedance spectra at room temperature. The ionic conductivity of nano-LaF3 bulk material （1 × 10^-5 S·cm^-1 ） at room temperature is significantly increased compared to that of single crystal LaF3 （1 × 10^-6 S·cm^-1）. A special phenomenon was observed firstly time that the ionic conductivity increased gradually with multiple testing in result of relaxation.展开更多
Experiment about ultrafine comminution in theory of vertiginous current of bulk material has successfully performed by a lately developed vertical shaft centrifugal autogenous grinder. The results of tested several ma...Experiment about ultrafine comminution in theory of vertiginous current of bulk material has successfully performed by a lately developed vertical shaft centrifugal autogenous grinder. The results of tested several materials are analyzed, moreover. the comminution mechanism and the affecting factors of ultrafine comminution are analyzed.展开更多
The fluidity and classification of bulk material (loose body) were introduced, the self-grinding mechanism and the affecting factors of bulk materials in various forms of phase, state and motion were investigated. A r...The fluidity and classification of bulk material (loose body) were introduced, the self-grinding mechanism and the affecting factors of bulk materials in various forms of phase, state and motion were investigated. A rotational-flow-state centrifugal autogenous grinder was developed on the basis of applying self-grinding mechanism of bulk material,the result tested by the autogenous grinder was compared with that tested by 4R Raymond mills, and fine particles with extremely high specific area were obtained. The feasibility of the developed new-type autogenous grinder in the view of fluid motion of bulk material was proved.展开更多
Wet and sticky bulk materials exhibit poor flowability during the mixing process,which prevents adequate contact between dry and wet particles.This results in uneven moisture distribution and deterioration in the mixi...Wet and sticky bulk materials exhibit poor flowability during the mixing process,which prevents adequate contact between dry and wet particles.This results in uneven moisture distribution and deterioration in the mixing system.To address these issues,the mixing process of viscous concrete was focused on a vertical blender.A comprehensive investigation into mixing mechanisms and particles flow patterns were conducted using the discrete element method(DEM).The accuracy of the contact parameters in DEM was calibrated through repose angle and validated by torques tested in a custom-built mixing platform.And then,the effects of moisture content,filling level,rotational speed,and inclined angle were systematically investigated with respect to key mixing metrics:the relative standard deviation(RSD),coordination number(CN),segregation index(SI)of wet particles,as well as liquid mass.The results indicated that when the moisture content is 8%,filling level is 50%,and rotational speed is more than 60 rpm,the CN and mixing efficiency are acceptable,and the RSD and SI are low,thereby improving the mixing quality.The convective motion was revealed as the dominant flow regime through statistical quantification of diffusion coefficients and Peclet numbers.Finally,Box-Behnken Design was employed to develop quadratic polynomial models for RSD,CN,and SI,which demonstrated strong accuracy in predicting mixing performance and enabled systematic optimization of critical process parameters.展开更多
Currently,friction characteristics obtained from empirical parameters or soil direct shear tests are widely applied in the resistance calculation and operational parameter optimization of soil tillage components.Howev...Currently,friction characteristics obtained from empirical parameters or soil direct shear tests are widely applied in the resistance calculation and operational parameter optimization of soil tillage components.However,the operation of soiltouching components is a dynamic process,and there are few reports on the dynamic friction characteristics of soil-contacting components in agricultural tillage based on factors such as different moisture content,pressure,and relative velocity.Herein,a test device to measure the friction characteristics of compressible bulk materials was developed:the interface friction between the soil and 65Mn plate and the internal friction characteristics of soil were tested using this device,and the dynamic changes of interface friction coefficient and internal friction coefficient with moisture content,pressure,and relative velocity were obtained.Based on the dynamic friction parameters of soil,the ditching resistance model of a typical ploughshare opener was established,the ditching resistance value was predicted,and field experiments were performed under different operating speeds(0.5 m/s,0.7 m/s,and 0.9 m/s)and ditching depths(60 mm,100 mm,and 140 mm).The results indicated that the calculated values of the ditching resistance model based on the dynamic friction parameters of soil reduced the error by 15%compared with the calculated values based on the friction characteristics of the soil direct shear test,which verified the accuracy of the ditching resistance model and the validity of the parameters obtained from the test device for the friction characteristics of compressible bulk materials.In addition,the minimum ditching resistance can be obtained when the ditching speed is 0.7 m/s at the same ditching depths,which is consistent with the dynamic friction characteristics of soil.It can be found that the dynamic friction characteristics of bulk materials have basic theoretical support for the optimization of operational component structures and operational parameters.展开更多
Authors produced rapidly solidified T15 high speed steel powders by high pressure(5~ 6MPa) N_a atomization and liquid N_2 cooling,observed and analyzed the morphology and structure of the powders;at the same time,prep...Authors produced rapidly solidified T15 high speed steel powders by high pressure(5~ 6MPa) N_a atomization and liquid N_2 cooling,observed and analyzed the morphology and structure of the powders;at the same time,prepared bulk microcrystalline T15 high speed steel materials by hot extruding or HIPing and hot rolling of the powders,observed and measured the microstructure and performance of the bulk materials.It was shown that rapid solidification may change the solidification characteristics and structure of T15 high speed steel powder and improve the qualities and properties of T15 high speed steel materials.展开更多
1.Introduction The synthesis of bulk nanostructured multiphase(NM)mate-rials with extreme properties such as high hardness and strength is one of the most interesting research topics in materials science and engineeri...1.Introduction The synthesis of bulk nanostructured multiphase(NM)mate-rials with extreme properties such as high hardness and strength is one of the most interesting research topics in materials science and engineering[1].At present,NM alloys can be produced by several synthesis methods,including sintering of nanocomposites[2,3],physical or chemical vapour deposition(PVD or CVD)[4],crystallization of metallic glasses[5],and severe plastic deforma-tion(SPD)[6-8].However,industry applications of bulk NM alloys produced by these methods are significantly restricted by their ge-ometrical and size limitations.Thus,the fabrication of large-scale NM alloys remains challenging.展开更多
Bulk materials were synthesized by the Bridgman technique using the elements Cu, Ga, Se. These samples were characterized by Energy Dispersive Spectrometry (EDS) to determine the elemental composition, as well as by X...Bulk materials were synthesized by the Bridgman technique using the elements Cu, Ga, Se. These samples were characterized by Energy Dispersive Spectrometry (EDS) to determine the elemental composition, as well as by X-ray diffraction for structure, hot point probe method for type of conductivity. Optical response (Photoconductivity) and Photoluminescence (PL) and PL-excitation (PLE) at temperatures from 4.2 to 77 K were also used to estimate the band-gap energy of Cu-Ga<sub>3</sub>Se<sub>5</sub>. They show a nearly perfect stoechiometry and present p-type conductivity. CuGa<sub>3</sub>Se<sub>5</sub> either have an Ordered Defect Chalcopyrite structure (ODC), or an Ordered Vacancy Chalcopyrite structure (OVC). The gap energy obtained by Photoconductivity and Photoluminescence (PL) for the different samples is 1.85 eV. Studying the variation of the gap as a function of the temperature shows that the transition is a D-A type. The defects that appear are probably Ga<sub>Cu</sub>.展开更多
A bulk nanostructured Al-10.0Zn-2.8Mg-1.8Cu alloy was synthesized by cryomilling first and then by spark plasma sintering （SPS）, and the effect of heat treatment on the microstructures and mechanical properties of t...A bulk nanostructured Al-10.0Zn-2.8Mg-1.8Cu alloy was synthesized by cryomilling first and then by spark plasma sintering （SPS）, and the effect of heat treatment on the microstructures and mechanical properties of this alloy were studied. Most MgZn2 particles with a coarse size lie on the grain boundaries of the SPS-processed sample. After solid solution and artificial aging, fine spherical-like MgZn2 particles precipitate uniformly in the grain interiors. No obvious grain growth is found after the heat treatment. A nanoindentation study indicates that no clear change is found in the Yong＇s modulus of the nanostructured alloy after the heat treatment. However, the hardness of the nanostructured alloy increases by about 33% after the heat treatment, which is attributed to the effect of precipitation-hardening.展开更多
The unreacted equation of state（EOS） of energetic materials is an important thermodynamic relationship to characterize their high pressure behaviors and has practical importance. The previous experimental and theore...The unreacted equation of state（EOS） of energetic materials is an important thermodynamic relationship to characterize their high pressure behaviors and has practical importance. The previous experimental and theoretical works on the equation of state of several energetic materials including nitromethane, 1,3,5-trinitrohexahydro-1,3,5-triazine（RDX）,1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane（HMX）, hexanitrostilbene（HNS）, hexanitrohexaazaisowurtzitane（HNIW or CL-20）, pentaerythritol tetranitrate（PETN）, 2,6-diamino-3,5-dinitropyrazine-1-oxide（LLM-105）, triamino-trinitrobenzene（TATB）, 1,1-diamino-2,2-dinitroethene（DADNE or FOX-7）, and trinitrotoluene（TNT） are reviewed in this paper. The EOS determined from hydrostatic and non-hydrostatic compressions are discussed and compared. The theoretical results based on ab initio calculations are summarized and compared with the experimental data.展开更多
Under the synergistic effect of molecular design and devices engineering, small molecular organic solar cells have presented an unstoppable tendency for rapid development with putting forward donor- acceptor （D-A） s...Under the synergistic effect of molecular design and devices engineering, small molecular organic solar cells have presented an unstoppable tendency for rapid development with putting forward donor- acceptor （D-A） structures. Up to now, the highest power conversion efficiency of small molecules has exceeded 11%, comparable to that of polymers. In this review, we summarize the high performance small molecule donors in various classes of typical donor-acceptor （D-A） structures and discuss their relationships briefly.展开更多
Thermal rectification refers to the asymmetry in heat transfer capability when subjected to forward and reverse temperature gradients.A thermal cloak can render objects invisible in thermal fields by redirecting heat ...Thermal rectification refers to the asymmetry in heat transfer capability when subjected to forward and reverse temperature gradients.A thermal cloak can render objects invisible in thermal fields by redirecting heat flux pathways.In this paper,we present a thermal diode model based on a bi-layer thermal cloak system that incorporates a composite heat-fluxattracting layer with asymmetric,temperature-dependent thermal conductivity.In the forward case,the heat flux bypasses the cloaking region while maintaining undistorted background isotherm contours,whereas in the reverse case,the thermal cloak fails to function and the device effectively insulates heat.Consequently,thermal rectification occurs in the bi-layer thermal cloak system.A significant increase in the thermal rectification ratio is observed as the temperature gradient increases.By optimizing the system dimensions,a peak rectification ratio of 11.06 is achieved.This study provides physical insight and a design framework for developing novel thermal diodes with dual-functional thermal management capabilities.展开更多
This test will be to simulate actual drilling operations to prove that the rig functions as a unit as laid out in the design specifications. The testing is to further demonstrate that equipment and systems maintain th...This test will be to simulate actual drilling operations to prove that the rig functions as a unit as laid out in the design specifications. The testing is to further demonstrate that equipment and systems maintain their operability for an extended period and will highlight any problematic areas within the system designs or equipment suitability. All systems shall be operated in the fully automatic mode as designed.展开更多
Introducing transformation-induced plasticity(TRIP)effect into bulk metallic glass composites(BMGCs)is an effective route to improve their ductility and strain-hardening ability.Since the morphology and structure of t...Introducing transformation-induced plasticity(TRIP)effect into bulk metallic glass composites(BMGCs)is an effective route to improve their ductility and strain-hardening ability.Since the morphology and structure of the crystalline austenite phases responsible for the TRIP phenomenon are strongly dependent on the alloy composition and cooling rate during freezing,distinguishing the optimal cases from a vast variety of candidates is the primary task of exploring TRIP BMGCs.However,without a suitable theoretical guidance,the exploration of BMGCs is usually performed via the traditional trial-and-error route,making the BMGC development extremely time consuming and labor intensive.Here,we present a novel high-throughput strategy to accelerate the exploration process of TRIP BMGCs.The efficiency of this strategy was demonstrated on a well-studied Cu-Zr-Al alloy system.A screening library,comprised by121 cylindrical samples with different conditions,was rapidly prepared by laser additive manufacturing(LAM).The phases of the library were efficiently identified by micro-area X-ray diffraction(M-XRD)to screen the optimal compositions and cooling rates that precipitate only B2-Cu Zr phase.The distribution uniformity of the B2-Cu Zr phase was further evaluated based on digital image processing technology to screen the candidates of better ductility.The high-throughput results are in good agreement with the previous casting investigations of discrete samples,confirming the validity of the present high-throughput strategy.展开更多
The possible practical limits for the specific surface area and capacitance performance of bulk sp^2 carbon materials were investigated experimentally and theoretically using a variety of carbon materials. We find the...The possible practical limits for the specific surface area and capacitance performance of bulk sp^2 carbon materials were investigated experimentally and theoretically using a variety of carbon materials. We find the limit for the specific surface area to be 3500–3700 m^2 g^(-1), and based on this, the corresponding best capacitance was predicted for various electrolyte systems. A model using an effective ionic diameter for the electrolyte ions was proposed and used to calculate the theoretical capacitance. A linear dependence of experimental capacitance versus effective specific surface area of various sp^2 carbon materials was obtained for all studied ionic liquid, organic and aqueous electrolyte systems. Furthermore, excellent agreement between the theoretical and experimental capacitance was observed for all the tested sp^2 carbon materials in these electrolyte systems, indicating that this model can be applied widely in the evaluation of various carbon materials for supercapacitors.展开更多
This paper reports a novel method of repetitive uniaxial compression combined with accumulative fold for preparing bulk submicron- to nanocrystalline copper starting with a coarse grained counterpart. Grain size reduc...This paper reports a novel method of repetitive uniaxial compression combined with accumulative fold for preparing bulk submicron- to nanocrystalline copper starting with a coarse grained counterpart. Grain size reduction and microstrain variations of the high purity copper samples after different passes of compression and fold are investigated by scanning electron microscope and x-ray diffraction （XRD）, respectively. Our results show that the average grain size of samples decreases from about 830 nm to 127 nm as the number of compression passes increases to 30. Microstrain in the compressed sample is found to increase for the first 20 passes, but to decrease at the last 10 passes. The variations of compressive yield strength and the shift of XRD peaks to larger diffraction angles are observed in the squeezed sample. Our experimental results demonstrate that the repetitive uniaxial compression combined with accumulative fold is an effective method to prepare bulk nanocrystalline metallic materials, in particular for soft metals such as Cu, Al and Pb.展开更多
The development of novel materials with dimensions on the nanoscale has become a rising star in the field of materials science.^(1)These nanocrystalline materials often have novel physical and chemical properties diff...The development of novel materials with dimensions on the nanoscale has become a rising star in the field of materials science.^(1)These nanocrystalline materials often have novel physical and chemical properties differing from those of the corresponding bulk materials and therefore open up new avenues for their wide applications.^(2)Inorganic peroxy compounds because of their exceptional reactivity and oxidative capacity are widely being used in industry as oxidizing agents,as catalysts and oxygen source in organic synthesis and as precursors for the synthesis of metal oxides.^(3)Most of these peroxy salts reversibly add oxygen and upon heating release oxygen and thus can be considered as"oxygen batteries".^(4)Sodium peroxide,sodium perborate,and sodium persulfate are commonly known inorganic peroxy compounds,which are considered to be inorganic salts of the hydrogen peroxide and react with water to produce H_(2)O_(2).^(5)The oxidation of organic compounds with these peroxy salts in acetic acid using KBr and transition metal based catalysts is well reported in the literature.^(6)The metal peroxides such as CaO_(2),MgO_(2)and BaO_(2)are highly stable and have the potential to promote the oxidation of organic substrates only at higher reaction temperatures.^(7,8)展开更多
Single-ion magnets(SIMs)are the most promising candidates for magnetic storage and processing of information at the molecular level.Apart from the properties of each isolated SIM,their performance crucially depends on...Single-ion magnets(SIMs)are the most promising candidates for magnetic storage and processing of information at the molecular level.Apart from the properties of each isolated SIM,their performance crucially depends on intermolecular exchange interactions in bulk materials or those occurring when individual SIMs are assembled into arrays for practical applications.However,compared with their magnetic anisotropy,the correlation of in-bulk intermolecular exchange interactions and magnetic relaxation parameters has been established to a much lesser extent.In this work,using an extended protocol involving XRD,multifrequency and frequency-domain EPR,SQUID magnetometry,DFT and ab initio calculations,we investigated intermolecular interactions in a new series of four bis-(phenoxy Schiff base)Co(Ⅱ)complexes representing field-induced SIMs.Combined multifrequency EPR ranging from 9 GHz to>1 THz allowed unique measurement of weak intermolecular exchange couplings of the order of 0.01 cm^(-1).Consolidation of EPR data with ac/dc SQUID magnetometry and detailed structural and quantum-chemical analyses allowed us to reliably analyze the key performance characteristics of these SIMs,the degree of polyhedral distortion,and the values of intermolecular exchange couplings in an attempt to achieve a firm interplay among them.Such analysis can become prototypical for future design and evaluation of crystals,assemblies and arrays of SIMs.展开更多
THERMACOND is an open-source software for ab initio calculations of phonon thermal transport in crystalline bulk materials.It optimizes computational efficiency by leveraging the crystal symmetry to solve the lineariz...THERMACOND is an open-source software for ab initio calculations of phonon thermal transport in crystalline bulk materials.It optimizes computational efficiency by leveraging the crystal symmetry to solve the linearized phonon Boltzmann transport equation(LPBTE)over the irreducible wedge of the Brillouin zone(IBZ).Brillouin zone integrations of δ functions are handled using the thetrahedron method.The code is written in Fortran 90,parallelized using MPI to manage the computational costs associated with large k-point meshes,and is distributed under the GNU public license GPLv3.Here we provide an overview of the program structure and present results for three examples:Germanium(Ge),Germanium Selenide(GeSe),and diamond.展开更多
文摘Nanocrystalline powder of LaF3 was synthesized by a method of direct precipitation from water solution. Particle size and shape of LaF3 nanocrystalline powder was analysed with TEM. Particles were mainly spherical with narrow particle size distribution （10 20 nm）. The average particle size analysed with XRD is 16.7 nm. Nano-LaF3 bulk material was prepared by compacting the powder to 1 GPa at room temperature and a vacuum of 10^-4 Pa. The ionic conductivity of nano-LaF3 bulk material was studied with complex impedance spectra at room temperature. The ionic conductivity of nano-LaF3 bulk material （1 × 10^-5 S·cm^-1 ） at room temperature is significantly increased compared to that of single crystal LaF3 （1 × 10^-6 S·cm^-1）. A special phenomenon was observed firstly time that the ionic conductivity increased gradually with multiple testing in result of relaxation.
文摘Experiment about ultrafine comminution in theory of vertiginous current of bulk material has successfully performed by a lately developed vertical shaft centrifugal autogenous grinder. The results of tested several materials are analyzed, moreover. the comminution mechanism and the affecting factors of ultrafine comminution are analyzed.
文摘The fluidity and classification of bulk material (loose body) were introduced, the self-grinding mechanism and the affecting factors of bulk materials in various forms of phase, state and motion were investigated. A rotational-flow-state centrifugal autogenous grinder was developed on the basis of applying self-grinding mechanism of bulk material,the result tested by the autogenous grinder was compared with that tested by 4R Raymond mills, and fine particles with extremely high specific area were obtained. The feasibility of the developed new-type autogenous grinder in the view of fluid motion of bulk material was proved.
基金supported by the Science and Technology Plan Project in Quanzhou,China(grant No.2023GZ5)the High-Level Talent Recruitment Project in Quanzhou,China(grant No.2023CT011)the National Natural Science Foundation of China(grant No.11772135)。
文摘Wet and sticky bulk materials exhibit poor flowability during the mixing process,which prevents adequate contact between dry and wet particles.This results in uneven moisture distribution and deterioration in the mixing system.To address these issues,the mixing process of viscous concrete was focused on a vertical blender.A comprehensive investigation into mixing mechanisms and particles flow patterns were conducted using the discrete element method(DEM).The accuracy of the contact parameters in DEM was calibrated through repose angle and validated by torques tested in a custom-built mixing platform.And then,the effects of moisture content,filling level,rotational speed,and inclined angle were systematically investigated with respect to key mixing metrics:the relative standard deviation(RSD),coordination number(CN),segregation index(SI)of wet particles,as well as liquid mass.The results indicated that when the moisture content is 8%,filling level is 50%,and rotational speed is more than 60 rpm,the CN and mixing efficiency are acceptable,and the RSD and SI are low,thereby improving the mixing quality.The convective motion was revealed as the dominant flow regime through statistical quantification of diffusion coefficients and Peclet numbers.Finally,Box-Behnken Design was employed to develop quadratic polynomial models for RSD,CN,and SI,which demonstrated strong accuracy in predicting mixing performance and enabled systematic optimization of critical process parameters.
基金financially supported by China Agriculture Research System(Grant No.CARS-02)Chongqing Science and Technology Bureau Agricultural High Tech Special Project(Grant No.CSTC2019ngzx0017).
文摘Currently,friction characteristics obtained from empirical parameters or soil direct shear tests are widely applied in the resistance calculation and operational parameter optimization of soil tillage components.However,the operation of soiltouching components is a dynamic process,and there are few reports on the dynamic friction characteristics of soil-contacting components in agricultural tillage based on factors such as different moisture content,pressure,and relative velocity.Herein,a test device to measure the friction characteristics of compressible bulk materials was developed:the interface friction between the soil and 65Mn plate and the internal friction characteristics of soil were tested using this device,and the dynamic changes of interface friction coefficient and internal friction coefficient with moisture content,pressure,and relative velocity were obtained.Based on the dynamic friction parameters of soil,the ditching resistance model of a typical ploughshare opener was established,the ditching resistance value was predicted,and field experiments were performed under different operating speeds(0.5 m/s,0.7 m/s,and 0.9 m/s)and ditching depths(60 mm,100 mm,and 140 mm).The results indicated that the calculated values of the ditching resistance model based on the dynamic friction parameters of soil reduced the error by 15%compared with the calculated values based on the friction characteristics of the soil direct shear test,which verified the accuracy of the ditching resistance model and the validity of the parameters obtained from the test device for the friction characteristics of compressible bulk materials.In addition,the minimum ditching resistance can be obtained when the ditching speed is 0.7 m/s at the same ditching depths,which is consistent with the dynamic friction characteristics of soil.It can be found that the dynamic friction characteristics of bulk materials have basic theoretical support for the optimization of operational component structures and operational parameters.
文摘Authors produced rapidly solidified T15 high speed steel powders by high pressure(5~ 6MPa) N_a atomization and liquid N_2 cooling,observed and analyzed the morphology and structure of the powders;at the same time,prepared bulk microcrystalline T15 high speed steel materials by hot extruding or HIPing and hot rolling of the powders,observed and measured the microstructure and performance of the bulk materials.It was shown that rapid solidification may change the solidification characteristics and structure of T15 high speed steel powder and improve the qualities and properties of T15 high speed steel materials.
基金funding from the Australian Research Council(ARC Discovery Project,Nos.DP200101408 and DP230100183).
文摘1.Introduction The synthesis of bulk nanostructured multiphase(NM)mate-rials with extreme properties such as high hardness and strength is one of the most interesting research topics in materials science and engineering[1].At present,NM alloys can be produced by several synthesis methods,including sintering of nanocomposites[2,3],physical or chemical vapour deposition(PVD or CVD)[4],crystallization of metallic glasses[5],and severe plastic deforma-tion(SPD)[6-8].However,industry applications of bulk NM alloys produced by these methods are significantly restricted by their ge-ometrical and size limitations.Thus,the fabrication of large-scale NM alloys remains challenging.
文摘Bulk materials were synthesized by the Bridgman technique using the elements Cu, Ga, Se. These samples were characterized by Energy Dispersive Spectrometry (EDS) to determine the elemental composition, as well as by X-ray diffraction for structure, hot point probe method for type of conductivity. Optical response (Photoconductivity) and Photoluminescence (PL) and PL-excitation (PLE) at temperatures from 4.2 to 77 K were also used to estimate the band-gap energy of Cu-Ga<sub>3</sub>Se<sub>5</sub>. They show a nearly perfect stoechiometry and present p-type conductivity. CuGa<sub>3</sub>Se<sub>5</sub> either have an Ordered Defect Chalcopyrite structure (ODC), or an Ordered Vacancy Chalcopyrite structure (OVC). The gap energy obtained by Photoconductivity and Photoluminescence (PL) for the different samples is 1.85 eV. Studying the variation of the gap as a function of the temperature shows that the transition is a D-A type. The defects that appear are probably Ga<sub>Cu</sub>.
基金supported by the National High-Tech Research and Development Program of China (No.2002AA302502)
文摘A bulk nanostructured Al-10.0Zn-2.8Mg-1.8Cu alloy was synthesized by cryomilling first and then by spark plasma sintering （SPS）, and the effect of heat treatment on the microstructures and mechanical properties of this alloy were studied. Most MgZn2 particles with a coarse size lie on the grain boundaries of the SPS-processed sample. After solid solution and artificial aging, fine spherical-like MgZn2 particles precipitate uniformly in the grain interiors. No obvious grain growth is found after the heat treatment. A nanoindentation study indicates that no clear change is found in the Yong＇s modulus of the nanostructured alloy after the heat treatment. However, the hardness of the nanostructured alloy increases by about 33% after the heat treatment, which is attributed to the effect of precipitation-hardening.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11174045 and 11404050)
文摘The unreacted equation of state（EOS） of energetic materials is an important thermodynamic relationship to characterize their high pressure behaviors and has practical importance. The previous experimental and theoretical works on the equation of state of several energetic materials including nitromethane, 1,3,5-trinitrohexahydro-1,3,5-triazine（RDX）,1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane（HMX）, hexanitrostilbene（HNS）, hexanitrohexaazaisowurtzitane（HNIW or CL-20）, pentaerythritol tetranitrate（PETN）, 2,6-diamino-3,5-dinitropyrazine-1-oxide（LLM-105）, triamino-trinitrobenzene（TATB）, 1,1-diamino-2,2-dinitroethene（DADNE or FOX-7）, and trinitrotoluene（TNT） are reviewed in this paper. The EOS determined from hydrostatic and non-hydrostatic compressions are discussed and compared. The theoretical results based on ab initio calculations are summarized and compared with the experimental data.
基金supported by the National Natural Science Foundation of China (Nos. 21474022, 51603051)Youth Innovation Promotion Association CAS and Beijing Nova Program (No. Z171100001117062)the Chinese Academy of Sciences
文摘Under the synergistic effect of molecular design and devices engineering, small molecular organic solar cells have presented an unstoppable tendency for rapid development with putting forward donor- acceptor （D-A） structures. Up to now, the highest power conversion efficiency of small molecules has exceeded 11%, comparable to that of polymers. In this review, we summarize the high performance small molecule donors in various classes of typical donor-acceptor （D-A） structures and discuss their relationships briefly.
文摘Thermal rectification refers to the asymmetry in heat transfer capability when subjected to forward and reverse temperature gradients.A thermal cloak can render objects invisible in thermal fields by redirecting heat flux pathways.In this paper,we present a thermal diode model based on a bi-layer thermal cloak system that incorporates a composite heat-fluxattracting layer with asymmetric,temperature-dependent thermal conductivity.In the forward case,the heat flux bypasses the cloaking region while maintaining undistorted background isotherm contours,whereas in the reverse case,the thermal cloak fails to function and the device effectively insulates heat.Consequently,thermal rectification occurs in the bi-layer thermal cloak system.A significant increase in the thermal rectification ratio is observed as the temperature gradient increases.By optimizing the system dimensions,a peak rectification ratio of 11.06 is achieved.This study provides physical insight and a design framework for developing novel thermal diodes with dual-functional thermal management capabilities.
文摘This test will be to simulate actual drilling operations to prove that the rig functions as a unit as laid out in the design specifications. The testing is to further demonstrate that equipment and systems maintain their operability for an extended period and will highlight any problematic areas within the system designs or equipment suitability. All systems shall be operated in the fully automatic mode as designed.
基金the National Natural Science Foundation of China under Grant Nos.51671042,51671043,51675074 and 51971047the project of Liaoning Province’s“rejuvenating Liaoning talents plan”under Grant No.XLYC1907046+4 种基金the Program for Innovative Talents of Liaoning Higher Education Institution under Grant No.LR2018014the Natural Science Foundation of Liaoning Province under Grant No.2019-MS-034the Joint Research Fund Liaoning-Shenyang National Laboratory for Materials Science under Grant No.2019JH3/30100032Dalian Science and Technology Innovation Fund Project under Grant No.2018J11CY027the Dalian Support Plan for Innovation of High-level Talents under Grant No.2018RQ07。
文摘Introducing transformation-induced plasticity(TRIP)effect into bulk metallic glass composites(BMGCs)is an effective route to improve their ductility and strain-hardening ability.Since the morphology and structure of the crystalline austenite phases responsible for the TRIP phenomenon are strongly dependent on the alloy composition and cooling rate during freezing,distinguishing the optimal cases from a vast variety of candidates is the primary task of exploring TRIP BMGCs.However,without a suitable theoretical guidance,the exploration of BMGCs is usually performed via the traditional trial-and-error route,making the BMGC development extremely time consuming and labor intensive.Here,we present a novel high-throughput strategy to accelerate the exploration process of TRIP BMGCs.The efficiency of this strategy was demonstrated on a well-studied Cu-Zr-Al alloy system.A screening library,comprised by121 cylindrical samples with different conditions,was rapidly prepared by laser additive manufacturing(LAM).The phases of the library were efficiently identified by micro-area X-ray diffraction(M-XRD)to screen the optimal compositions and cooling rates that precipitate only B2-Cu Zr phase.The distribution uniformity of the B2-Cu Zr phase was further evaluated based on digital image processing technology to screen the candidates of better ductility.The high-throughput results are in good agreement with the previous casting investigations of discrete samples,confirming the validity of the present high-throughput strategy.
基金supported by the National Basic Research Program of China(2012CB933401)the National Natural Science Foundation of China(51472124+3 种基金5127309321374050)the Natural Science Foundation of Tianjin(13RCGFGX01121)Science Research Project of Langfang Teachers University(LSLB201401)
文摘The possible practical limits for the specific surface area and capacitance performance of bulk sp^2 carbon materials were investigated experimentally and theoretically using a variety of carbon materials. We find the limit for the specific surface area to be 3500–3700 m^2 g^(-1), and based on this, the corresponding best capacitance was predicted for various electrolyte systems. A model using an effective ionic diameter for the electrolyte ions was proposed and used to calculate the theoretical capacitance. A linear dependence of experimental capacitance versus effective specific surface area of various sp^2 carbon materials was obtained for all studied ionic liquid, organic and aqueous electrolyte systems. Furthermore, excellent agreement between the theoretical and experimental capacitance was observed for all the tested sp^2 carbon materials in these electrolyte systems, indicating that this model can be applied widely in the evaluation of various carbon materials for supercapacitors.
基金supported by the National Natural Science Foundation of China (Grant No 50572067)
文摘This paper reports a novel method of repetitive uniaxial compression combined with accumulative fold for preparing bulk submicron- to nanocrystalline copper starting with a coarse grained counterpart. Grain size reduction and microstrain variations of the high purity copper samples after different passes of compression and fold are investigated by scanning electron microscope and x-ray diffraction （XRD）, respectively. Our results show that the average grain size of samples decreases from about 830 nm to 127 nm as the number of compression passes increases to 30. Microstrain in the compressed sample is found to increase for the first 20 passes, but to decrease at the last 10 passes. The variations of compressive yield strength and the shift of XRD peaks to larger diffraction angles are observed in the squeezed sample. Our experimental results demonstrate that the repetitive uniaxial compression combined with accumulative fold is an effective method to prepare bulk nanocrystalline metallic materials, in particular for soft metals such as Cu, Al and Pb.
文摘The development of novel materials with dimensions on the nanoscale has become a rising star in the field of materials science.^(1)These nanocrystalline materials often have novel physical and chemical properties differing from those of the corresponding bulk materials and therefore open up new avenues for their wide applications.^(2)Inorganic peroxy compounds because of their exceptional reactivity and oxidative capacity are widely being used in industry as oxidizing agents,as catalysts and oxygen source in organic synthesis and as precursors for the synthesis of metal oxides.^(3)Most of these peroxy salts reversibly add oxygen and upon heating release oxygen and thus can be considered as"oxygen batteries".^(4)Sodium peroxide,sodium perborate,and sodium persulfate are commonly known inorganic peroxy compounds,which are considered to be inorganic salts of the hydrogen peroxide and react with water to produce H_(2)O_(2).^(5)The oxidation of organic compounds with these peroxy salts in acetic acid using KBr and transition metal based catalysts is well reported in the literature.^(6)The metal peroxides such as CaO_(2),MgO_(2)and BaO_(2)are highly stable and have the potential to promote the oxidation of organic substrates only at higher reaction temperatures.^(7,8)
基金the Summer Student Program at HZB for the opportunity to conduct THz-EPR measurementsFinancial support by the Russian Science Foundation through grant no.22-13-00376(X-and Q-band EPR measurements)is acknowledged+1 种基金the financial support from the institutional sources of the Department of Inorganic Chemistry,Palacký University Olomouc,Czech Republicindebted to Deutsche Forschungsgemeinschaft(DFG,German Research Foundation,Project No.LO 2898/1-1).
文摘Single-ion magnets(SIMs)are the most promising candidates for magnetic storage and processing of information at the molecular level.Apart from the properties of each isolated SIM,their performance crucially depends on intermolecular exchange interactions in bulk materials or those occurring when individual SIMs are assembled into arrays for practical applications.However,compared with their magnetic anisotropy,the correlation of in-bulk intermolecular exchange interactions and magnetic relaxation parameters has been established to a much lesser extent.In this work,using an extended protocol involving XRD,multifrequency and frequency-domain EPR,SQUID magnetometry,DFT and ab initio calculations,we investigated intermolecular interactions in a new series of four bis-(phenoxy Schiff base)Co(Ⅱ)complexes representing field-induced SIMs.Combined multifrequency EPR ranging from 9 GHz to>1 THz allowed unique measurement of weak intermolecular exchange couplings of the order of 0.01 cm^(-1).Consolidation of EPR data with ac/dc SQUID magnetometry and detailed structural and quantum-chemical analyses allowed us to reliably analyze the key performance characteristics of these SIMs,the degree of polyhedral distortion,and the values of intermolecular exchange couplings in an attempt to achieve a firm interplay among them.Such analysis can become prototypical for future design and evaluation of crystals,assemblies and arrays of SIMs.
基金funding from the NSF-CSSI program,award#2103989.
文摘THERMACOND is an open-source software for ab initio calculations of phonon thermal transport in crystalline bulk materials.It optimizes computational efficiency by leveraging the crystal symmetry to solve the linearized phonon Boltzmann transport equation(LPBTE)over the irreducible wedge of the Brillouin zone(IBZ).Brillouin zone integrations of δ functions are handled using the thetrahedron method.The code is written in Fortran 90,parallelized using MPI to manage the computational costs associated with large k-point meshes,and is distributed under the GNU public license GPLv3.Here we provide an overview of the program structure and present results for three examples:Germanium(Ge),Germanium Selenide(GeSe),and diamond.
