Thermal barrier coating(TBC)materials perform an increasingly important role in the thermal or chemical protection of hot components in a gas turbine.In this study,a novel high entropy hafnate(Y_(0.2)Gd_(0.2)Dy_(0.2)E...Thermal barrier coating(TBC)materials perform an increasingly important role in the thermal or chemical protection of hot components in a gas turbine.In this study,a novel high entropy hafnate(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7) was synthesized by solution combustion method and investigated as a potential TBC layer.The as-synthesized(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7) possesses a pure single disordered fluorite phase with a highly homogeneous distribution of rare earth(RE)cations,exhibiting prominent phase stability and excellent chemical compatibility with Al_(2)O_(3) even at 1300°C.Moreover,(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7) demonstrates a more sluggish grain growth rate than Y_(2)Hf_(2)O_(7).The thermal conductivity of(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7)(0.73-0.93 W m^(-1)K^(-1))is smaller than those of components RE_(2)Hf_(2)O_(7) and many high entropy TBC materials.Beside,the calculated thermal expansion coefficient(TEC)of(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7)(10.68×10^(-6)/K,1100°C)is smaller than that of yttriastabilized zirconia(YSZ).Based on the results of this work,(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7) is suitable for the next generation TBC materials with outstanding properties.展开更多
A new bismuth-based halide double perovskite Cs_(2)KBiCl_(6) was isolated successfully through solid-state reactions and investigated using X-ray and neutron diffraction.Rather than an ordered structure,the crystal st...A new bismuth-based halide double perovskite Cs_(2)KBiCl_(6) was isolated successfully through solid-state reactions and investigated using X-ray and neutron diffraction.Rather than an ordered structure,the crystal structure consists of shifted Cs,K,Bi,and Cl sites from the ideal positions with fractional occupancy in compensation,leading to variable local coordination of Cs^(+)ions,as revealed by^(133)Cs solid-state nuclear magnetic resonance spectroscopy.Cs_(2)KBiCl_(6) displays volume hysteresis at 5-298 K range upon heating and cooling.The Cs_(2)KBiCl_(6) has a direct bandgap of 3.35(2)eV and red-shift luminescence of around 600 nm upon Mn doping compared with the Na analogue.The stabilization of disordered structure in Cs_(2)KBiCl_(6) is related to two factors including the large-sized K^(+)cation which prefers to coordinate with more than six Cl^(-),and the Bi^(3+)with 6s^(2) lone pair which has a preference for a local asymmetric environment.These findings could have general application and help to understand the structure and property of halide perovskites.展开更多
Charge density wave(CDW) in kagome materials with the geometric frustration is able to carry unconventional characteristics.Recently, a CDW has been observed below the antiferromagnetic order in kagome FeGe, in which ...Charge density wave(CDW) in kagome materials with the geometric frustration is able to carry unconventional characteristics.Recently, a CDW has been observed below the antiferromagnetic order in kagome FeGe, in which magnetism and CDW are intertwined to form an emergent quantum ground state. However, the CDW is only short-ranged and the structural modulation originating from it has yet to be determined experimentally. Here we realize a long-range CDW order by post-annealing process,and resolve the structure model through single crystal X-ray diffraction. Occupational disorder of Ge resulting from short-range CDW correlations above T_(CDW) is identified from structure refinements. The partial dimerization of Ge along the c axis is unveiled to be the dominant distortion for the CDW. Occupational disorder of Ge is also proved to exist in the CDW phase due to the random selection of partially dimerized Ge sites. Our work provides useful insights for understanding the unconventional nature of the CDW in FeGe.展开更多
The layeredδ-MnO_(2)(dMO)is an excellent cathode material for rechargeable aqueous zinc-ion batteries owing to its large interlayer distance(~0.7 nm),high capacity,and low cost;however,such cathodes suffer from struc...The layeredδ-MnO_(2)(dMO)is an excellent cathode material for rechargeable aqueous zinc-ion batteries owing to its large interlayer distance(~0.7 nm),high capacity,and low cost;however,such cathodes suffer from structural degradation during the long-term cycling process,leading to capacity fading.In this study,a Co-doped dMO composite with reduced graphene oxide(GC-dMO)is developed using a simple cost-effective hydrothermal method.The degree of disorderness increases owing to the hetero-atom doping and graphene oxide composites.It is demonstrated that layered dMO and GC-dMO undergo a structural transition from K-birnessite to the Zn-buserite phase upon the first discharge,which enhances the intercalation of Zn^(2+)ions,H_(2)O molecules in the layered structure.The GC-dMO cathode exhibits an excellent capacity of 302 mAh g^(-1)at a current density of 100 mAg^(-1)after 100 cycles as compared with the dMO cathode(159 mAhg^(-1)).The excellent electrochemical performance of the GC-dMO cathode owing to Co-doping and graphene oxide sheets enhances the interlayer gap and disorderness,and maintains structural stability,which facilitates the easy reverse intercalation and de-intercalation of Zn^(2+)ions and H_(2)O molecules.Therefore,GC-dMO is a promising cathode material for large-scale aqueous ZIBs.展开更多
Ultrasonic vibration can be used for the micro-molding of metallic glasses(MGs)due to stress-softening and fast surface-diffusion effects.However,the structural rearrangement under ultrasonic vibration and its impact ...Ultrasonic vibration can be used for the micro-molding of metallic glasses(MGs)due to stress-softening and fast surface-diffusion effects.However,the structural rearrangement under ultrasonic vibration and its impact on the mechanical response of metallic glasses remain a puzzle.In this work,the plastic flow of the Zr35Ti30Cu8.25Be26.75 metallic glass with the applied ultrasonic-vibration energy of 140 J was investigated by nanoindentation.Both Kelvin and Maxwell-Voigt models have been adopted to analyze the structural evolution during the creep deformation.The increase of the characteristic relaxation time and the peak intensity of relaxation spectra can be found in the sample after ultrasonic vibration.It effectively improves the activation energy of atomic diffusion during the glass transition(Eg)and the growth of the crystal nucleus(Ep).A more homogenous plastic deformation with a weak loading-rate sensitivity of stress exponent is observed in the ultrasonic-vibrated sample,which coincides with the low pile-up and penetration depth as shown in the cross profile of indents.The structural rearrangement under resonance actuation demonstrated in this work might help us better understand the defect-activation mechanism for the plastic flow of amorphous systems.展开更多
超薄锂金属(≤50μm)是下一代高比能锂金属电池负极选择。然而纯锂质软、易脆,机械加工性较差,导致超薄锂箔的制备工艺复杂、成本高昂;此外相比于较厚的锂金属负极,超薄锂金属负极常呈现更差的电化学循环性能。本文提出一种“自下而上...超薄锂金属(≤50μm)是下一代高比能锂金属电池负极选择。然而纯锂质软、易脆,机械加工性较差,导致超薄锂箔的制备工艺复杂、成本高昂;此外相比于较厚的锂金属负极,超薄锂金属负极常呈现更差的电化学循环性能。本文提出一种“自下而上”的策略制备10~50μm厚度可控的超薄还原氧化石墨烯/锂金属(rGO/Li)复合箔材,其结构由大量无序随机的rGO片层非平行排列并均匀分散在锂金属内。首先将还原氧化石墨烯(rGO)粉片与熔融锂金属在200℃下搅拌复合,获得微米级的还原氧化石墨烯/锂复合粉片,之后将复合粉片作为原材料进一步通过反复辊压制备出结构均匀、超薄的复合箔材,该方法具有一定的规模化潜力。不同于其他所报道的rGO层状薄膜结构,在复合箔材中rGO片层随机无序分散形成三维网络,有利于实现锂的均匀沉积/剥离。所制50μm超薄无序结构rGO/Li复合箔材负极在对称电池中以1 mA cm^(-2)、1 mAh cm^(-2)条件在醚基电解液中可稳定循环1600 h以上,在与硫化聚丙烯腈(SPAN)正极组配全电池以0.2 C倍率循环220次后比容量高达~675 mAh g^(-1),优于使用同厚度纯锂负极的电池。展开更多
Structural parameters, elastic constants, and thermodynamic properties of ordered and disordered solid solutions of ZrHf alloys are investigated through first-principles calculations based on density-functional theory...Structural parameters, elastic constants, and thermodynamic properties of ordered and disordered solid solutions of ZrHf alloys are investigated through first-principles calculations based on density-functional theory （DFF）. The special quasi-random structure （SQS） method is used to model the disordered phase as a single unit cell, and two lamella structures are generated to model the ordered alloys. Small strains are applied to the unit cells to measure the elastic behavior and mechanical stability of ZrHf alloys and to obtain the independent elastic constants by the stress-strain relationship. Phonon dispersions and phonon density of states are presented to verify the thermodynamic stability of the considered phases. Our results show that both the ordered and disordered phases of ZrHf alloys are structurally stable. Based on the obtained phonon frequencies, thermodynamic properties, including Gibbs free energy, entropy, and heat capacity, are predicted within the quasi-harmonic approximation. It is verified that there are no obvious differences in energy between ordered and disordered phases over a wide temperature range.展开更多
Maxwell-Voigt model with two Kelvin units and one Maxwell unit was utilized to analyze the microalloying effect of Cu on the creep behavior of CoFe-based metallic glasses at different loading rates.The defect activati...Maxwell-Voigt model with two Kelvin units and one Maxwell unit was utilized to analyze the microalloying effect of Cu on the creep behavior of CoFe-based metallic glasses at different loading rates.The defect activation during creep deformation was detected by the relaxation time spectrum based on this model.The defect,with respect to a short relaxation time in relaxation spectra,intends to be activated at a quasi-static loading mode in the alloy with 0.5 at.%Cu addition.With further increasing loading rates,more defects with a large size were provoked activated at both hard and soft regions in the Cu-containing sample.A softening with the reduction of elastic modulus and hardness about 10%and 15%,respectively,was also observed in the Cu-doped sample.It is consistent with the pronounced viscoplastic deformation of this alloy along with the decrease of viscosity.Our work provides a microscopic insight into structural evolution during creep deformation in a Cu-doped metallic glass,which might help for understanding the plastic deformation of metallic glasses upon a minor addition.展开更多
There is an ever-growing demand for lightweighting of steel for structural applications,particularly for automobile and transportation applications.It is mainly to improve the fuel efficiency,reduce the CO_(2) emissio...There is an ever-growing demand for lightweighting of steel for structural applications,particularly for automobile and transportation applications.It is mainly to improve the fuel efficiency,reduce the CO_(2) emissions and cater the increased passenger safety.Hence,the main focus is to reduce the density of the steel structure without affecting other properties.This can be achieved by down-gauging of the conventional steel by replacing the steel with higher strength,however,it is limited by dent resistance and stiffness.So,the novel idea is to reduce the density of the steel itself.It is well-known that addition of Al to steel reduces the density of the steel.About 1wt% of Al addition to steel can reduce the density by 1.3%,decreases the elastic modulus by 2% and it improves the strength by about 40 MPa.There is a new class of low-density/lightweight steel with addition of about 6-9 wt% Al to steel.Addition of higher than 9 wt%of Al in steel leads to embrittlement issues due to ordering and environmental effect.These disordered Fe-Al lightweight steels have raised considerable interest due to their low-density,high ductility,costeffectiveness and feasibility for bulk production.The low-density steels are envisaged in the development of an advanced lightweight ground transportation system,huge structures and also for certain defence applications and in thermal power plants.展开更多
Electronic and magnetic properties of Fe1-xCoxSi alloys were investigated by using a full-potential linear augmented-plane-wave method based on density functional theory. Electronic structure calculation demonstrates ...Electronic and magnetic properties of Fe1-xCoxSi alloys were investigated by using a full-potential linear augmented-plane-wave method based on density functional theory. Electronic structure calculation demonstrates that half-metallic property appears in the Fe-rich region of 0 〈 x ≤ 0.25, while the alloys turn out to be a magnetic metal for x 〉 0.25. The concentration dependence of the magnetic moment of the alloys can be understood by the fixed Fermi level at minority band in Fe-rich region, as well as at the majority band in Co-rich region. In Fe-rich alloys, the electronic structure and the magnetic properties at Fe site depend mainly on the spin-polarization of nearest neighbouring Co atoms, while in Co-rich alloys, these features at Co site arise mainly from the neighbours of Fe atoms.展开更多
A drawn high density polyethylene（HDPE）has been measured by Raman spectroscopy and differential scanning calorimetry （DSC）. The crystalline structure of drawn HDPE is analysed by the Raman internal modes in terms ...A drawn high density polyethylene（HDPE）has been measured by Raman spectroscopy and differential scanning calorimetry （DSC）. The crystalline structure of drawn HDPE is analysed by the Raman internal modes in terms of mass fractions of the crystalline orthorhombic phase, the liquid- like amorphous phase and the disordered anisotropic phase. The mass fractions depend on draw temperature T;and draw ratio R;. The fraction of disordered anisotropic amorphous phase changes very little with, the T;and increases with increasing R;. Sum of the mass fractions of crystalline orthorhombic phase and the disordered anisotropic phase increases linearly as the same slope as the crystallinity W;determined from DSC measurements with increasing T;or R;and it is higher than the W;for all the samples. The results show that the mass fraction of disordered anisotropic phase is partially devoted by the taut tie molecules （TTM s） in the amorphous state. The dependence of the disordered anisotropic phase on T;and R;supports the mechanism of plastic deformation of fibre structure.展开更多
It is suggested that there is a kind of probability wave of the atomic configuration p(R)in crystals that can be deduced from the eigenequation of the ionic interaction Hamiltonian,and it has definite physical meaning...It is suggested that there is a kind of probability wave of the atomic configuration p(R)in crystals that can be deduced from the eigenequation of the ionic interaction Hamiltonian,and it has definite physical meaning. By use of the probability wave of the atomic con-figuration, the occupation probabilities of different kinds of atoms at lattice sites in multi-component solutions can be studied, and the crystal structures of multi-component solutionscan be predicted.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 51872234, 51502242, 51432008, 51802244, and 51821091)the Key R&D Program of Shaanxi Provence (No. 2019ZDLGY04-02)。
文摘Thermal barrier coating(TBC)materials perform an increasingly important role in the thermal or chemical protection of hot components in a gas turbine.In this study,a novel high entropy hafnate(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7) was synthesized by solution combustion method and investigated as a potential TBC layer.The as-synthesized(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7) possesses a pure single disordered fluorite phase with a highly homogeneous distribution of rare earth(RE)cations,exhibiting prominent phase stability and excellent chemical compatibility with Al_(2)O_(3) even at 1300°C.Moreover,(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7) demonstrates a more sluggish grain growth rate than Y_(2)Hf_(2)O_(7).The thermal conductivity of(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7)(0.73-0.93 W m^(-1)K^(-1))is smaller than those of components RE_(2)Hf_(2)O_(7) and many high entropy TBC materials.Beside,the calculated thermal expansion coefficient(TEC)of(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7)(10.68×10^(-6)/K,1100°C)is smaller than that of yttriastabilized zirconia(YSZ).Based on the results of this work,(Y_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Hf_(2)O_(7) is suitable for the next generation TBC materials with outstanding properties.
基金the National Science Foundation of China(Nos.22090043 and 22161014)Guangxi Natural Science Foundation(Nos.2019GXNSFGA245006 and 2020GXNSFAA297220)the Foundation of Guilin University of Technology(No.GUTQDJJ2018115)for the financial support。
文摘A new bismuth-based halide double perovskite Cs_(2)KBiCl_(6) was isolated successfully through solid-state reactions and investigated using X-ray and neutron diffraction.Rather than an ordered structure,the crystal structure consists of shifted Cs,K,Bi,and Cl sites from the ideal positions with fractional occupancy in compensation,leading to variable local coordination of Cs^(+)ions,as revealed by^(133)Cs solid-state nuclear magnetic resonance spectroscopy.Cs_(2)KBiCl_(6) displays volume hysteresis at 5-298 K range upon heating and cooling.The Cs_(2)KBiCl_(6) has a direct bandgap of 3.35(2)eV and red-shift luminescence of around 600 nm upon Mn doping compared with the Na analogue.The stabilization of disordered structure in Cs_(2)KBiCl_(6) is related to two factors including the large-sized K^(+)cation which prefers to coordinate with more than six Cl^(-),and the Bi^(3+)with 6s^(2) lone pair which has a preference for a local asymmetric environment.These findings could have general application and help to understand the structure and property of halide perovskites.
基金the National Natural Science Foundation of China (Grant No.12204298)the National Natural Science Foundation of China (Grant No.12074242)+4 种基金the National Natural Science Foundation of China (Grant No.12174334)the National Natural Science Foundation of China (Grant Nos.52272265,U1932217,11974246,and 12004252)the Science and Technology Commission of Shanghai Municipality (Grant No.21JC1402600)the Zhejiang Provincial Natural Science Foundation of China (Grant No.LQ23A040009)supported by the Deutsche Forschungsgemeinschaft (DFG,German Research Foundation) (Grant No.406658237)。
文摘Charge density wave(CDW) in kagome materials with the geometric frustration is able to carry unconventional characteristics.Recently, a CDW has been observed below the antiferromagnetic order in kagome FeGe, in which magnetism and CDW are intertwined to form an emergent quantum ground state. However, the CDW is only short-ranged and the structural modulation originating from it has yet to be determined experimentally. Here we realize a long-range CDW order by post-annealing process,and resolve the structure model through single crystal X-ray diffraction. Occupational disorder of Ge resulting from short-range CDW correlations above T_(CDW) is identified from structure refinements. The partial dimerization of Ge along the c axis is unveiled to be the dominant distortion for the CDW. Occupational disorder of Ge is also proved to exist in the CDW phase due to the random selection of partially dimerized Ge sites. Our work provides useful insights for understanding the unconventional nature of the CDW in FeGe.
基金supported by the National Research Foundation of Korea(NRF)grants funded by the Korean Government(NRF-2021R1A4A1030318,NRF-2022R1C1C1011386,NRF-2020M3H4A1A03084258)supported by the"Regional Innovation Strategy(RIS)"through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(MOE)(2021RIS-003)
文摘The layeredδ-MnO_(2)(dMO)is an excellent cathode material for rechargeable aqueous zinc-ion batteries owing to its large interlayer distance(~0.7 nm),high capacity,and low cost;however,such cathodes suffer from structural degradation during the long-term cycling process,leading to capacity fading.In this study,a Co-doped dMO composite with reduced graphene oxide(GC-dMO)is developed using a simple cost-effective hydrothermal method.The degree of disorderness increases owing to the hetero-atom doping and graphene oxide composites.It is demonstrated that layered dMO and GC-dMO undergo a structural transition from K-birnessite to the Zn-buserite phase upon the first discharge,which enhances the intercalation of Zn^(2+)ions,H_(2)O molecules in the layered structure.The GC-dMO cathode exhibits an excellent capacity of 302 mAh g^(-1)at a current density of 100 mAg^(-1)after 100 cycles as compared with the dMO cathode(159 mAhg^(-1)).The excellent electrochemical performance of the GC-dMO cathode owing to Co-doping and graphene oxide sheets enhances the interlayer gap and disorderness,and maintains structural stability,which facilitates the easy reverse intercalation and de-intercalation of Zn^(2+)ions and H_(2)O molecules.Therefore,GC-dMO is a promising cathode material for large-scale aqueous ZIBs.
基金the National Natural Science Foundation of China(51631003,51871157 and 51601038)the Key Basic and Applied Research Program of Guangdong Province,China(2019B030302010)+3 种基金the Natural Science Foundation of Jiangsu Province,China(BK20171354)the Fundamental Research Funds for the Central Universities(2242020K40002)the Research and Practice Innovation Program for Postgraduates in Jiangsu Province(SJCX20_0038)Jiangsu Key Laboratory for Advanced Metallic Materials(BM2007204)。
文摘Ultrasonic vibration can be used for the micro-molding of metallic glasses(MGs)due to stress-softening and fast surface-diffusion effects.However,the structural rearrangement under ultrasonic vibration and its impact on the mechanical response of metallic glasses remain a puzzle.In this work,the plastic flow of the Zr35Ti30Cu8.25Be26.75 metallic glass with the applied ultrasonic-vibration energy of 140 J was investigated by nanoindentation.Both Kelvin and Maxwell-Voigt models have been adopted to analyze the structural evolution during the creep deformation.The increase of the characteristic relaxation time and the peak intensity of relaxation spectra can be found in the sample after ultrasonic vibration.It effectively improves the activation energy of atomic diffusion during the glass transition(Eg)and the growth of the crystal nucleus(Ep).A more homogenous plastic deformation with a weak loading-rate sensitivity of stress exponent is observed in the ultrasonic-vibrated sample,which coincides with the low pile-up and penetration depth as shown in the cross profile of indents.The structural rearrangement under resonance actuation demonstrated in this work might help us better understand the defect-activation mechanism for the plastic flow of amorphous systems.
文摘超薄锂金属(≤50μm)是下一代高比能锂金属电池负极选择。然而纯锂质软、易脆,机械加工性较差,导致超薄锂箔的制备工艺复杂、成本高昂;此外相比于较厚的锂金属负极,超薄锂金属负极常呈现更差的电化学循环性能。本文提出一种“自下而上”的策略制备10~50μm厚度可控的超薄还原氧化石墨烯/锂金属(rGO/Li)复合箔材,其结构由大量无序随机的rGO片层非平行排列并均匀分散在锂金属内。首先将还原氧化石墨烯(rGO)粉片与熔融锂金属在200℃下搅拌复合,获得微米级的还原氧化石墨烯/锂复合粉片,之后将复合粉片作为原材料进一步通过反复辊压制备出结构均匀、超薄的复合箔材,该方法具有一定的规模化潜力。不同于其他所报道的rGO层状薄膜结构,在复合箔材中rGO片层随机无序分散形成三维网络,有利于实现锂的均匀沉积/剥离。所制50μm超薄无序结构rGO/Li复合箔材负极在对称电池中以1 mA cm^(-2)、1 mAh cm^(-2)条件在醚基电解液中可稳定循环1600 h以上,在与硫化聚丙烯腈(SPAN)正极组配全电池以0.2 C倍率循环220次后比容量高达~675 mAh g^(-1),优于使用同厚度纯锂负极的电池。
基金Project supported by the National Natural Science Foundation of China(Grant No.51102009)the Long-Term Subsidy Mechanism from the Ministry of Finance and the Ministry of Education of China
文摘Structural parameters, elastic constants, and thermodynamic properties of ordered and disordered solid solutions of ZrHf alloys are investigated through first-principles calculations based on density-functional theory （DFF）. The special quasi-random structure （SQS） method is used to model the disordered phase as a single unit cell, and two lamella structures are generated to model the ordered alloys. Small strains are applied to the unit cells to measure the elastic behavior and mechanical stability of ZrHf alloys and to obtain the independent elastic constants by the stress-strain relationship. Phonon dispersions and phonon density of states are presented to verify the thermodynamic stability of the considered phases. Our results show that both the ordered and disordered phases of ZrHf alloys are structurally stable. Based on the obtained phonon frequencies, thermodynamic properties, including Gibbs free energy, entropy, and heat capacity, are predicted within the quasi-harmonic approximation. It is verified that there are no obvious differences in energy between ordered and disordered phases over a wide temperature range.
基金the Natural Science Foundation of Jiangsu Province,China(No.BK20171354)the National Natural Science Foundation of China(Nos.51631003 and 51601038)+2 种基金the Key Basic and Applied Research Program of Guangdong Province,China(No.2019B030302010)the Fundamental Research Funds for the Central Universities(No.2242020K40002)the Jiangsu Key Laboratory for Advanced Metallic Materials(No.BM2007204)。
文摘Maxwell-Voigt model with two Kelvin units and one Maxwell unit was utilized to analyze the microalloying effect of Cu on the creep behavior of CoFe-based metallic glasses at different loading rates.The defect activation during creep deformation was detected by the relaxation time spectrum based on this model.The defect,with respect to a short relaxation time in relaxation spectra,intends to be activated at a quasi-static loading mode in the alloy with 0.5 at.%Cu addition.With further increasing loading rates,more defects with a large size were provoked activated at both hard and soft regions in the Cu-containing sample.A softening with the reduction of elastic modulus and hardness about 10%and 15%,respectively,was also observed in the Cu-doped sample.It is consistent with the pronounced viscoplastic deformation of this alloy along with the decrease of viscosity.Our work provides a microscopic insight into structural evolution during creep deformation in a Cu-doped metallic glass,which might help for understanding the plastic deformation of metallic glasses upon a minor addition.
文摘There is an ever-growing demand for lightweighting of steel for structural applications,particularly for automobile and transportation applications.It is mainly to improve the fuel efficiency,reduce the CO_(2) emissions and cater the increased passenger safety.Hence,the main focus is to reduce the density of the steel structure without affecting other properties.This can be achieved by down-gauging of the conventional steel by replacing the steel with higher strength,however,it is limited by dent resistance and stiffness.So,the novel idea is to reduce the density of the steel itself.It is well-known that addition of Al to steel reduces the density of the steel.About 1wt% of Al addition to steel can reduce the density by 1.3%,decreases the elastic modulus by 2% and it improves the strength by about 40 MPa.There is a new class of low-density/lightweight steel with addition of about 6-9 wt% Al to steel.Addition of higher than 9 wt%of Al in steel leads to embrittlement issues due to ordering and environmental effect.These disordered Fe-Al lightweight steels have raised considerable interest due to their low-density,high ductility,costeffectiveness and feasibility for bulk production.The low-density steels are envisaged in the development of an advanced lightweight ground transportation system,huge structures and also for certain defence applications and in thermal power plants.
基金Project supported by the State Key Development Program for Basic Research of China （Grant No 2001CB610605）, and the National Natural Science Foundation of China （Grant No 10474132）.
文摘Electronic and magnetic properties of Fe1-xCoxSi alloys were investigated by using a full-potential linear augmented-plane-wave method based on density functional theory. Electronic structure calculation demonstrates that half-metallic property appears in the Fe-rich region of 0 〈 x ≤ 0.25, while the alloys turn out to be a magnetic metal for x 〉 0.25. The concentration dependence of the magnetic moment of the alloys can be understood by the fixed Fermi level at minority band in Fe-rich region, as well as at the majority band in Co-rich region. In Fe-rich alloys, the electronic structure and the magnetic properties at Fe site depend mainly on the spin-polarization of nearest neighbouring Co atoms, while in Co-rich alloys, these features at Co site arise mainly from the neighbours of Fe atoms.
文摘A drawn high density polyethylene（HDPE）has been measured by Raman spectroscopy and differential scanning calorimetry （DSC）. The crystalline structure of drawn HDPE is analysed by the Raman internal modes in terms of mass fractions of the crystalline orthorhombic phase, the liquid- like amorphous phase and the disordered anisotropic phase. The mass fractions depend on draw temperature T;and draw ratio R;. The fraction of disordered anisotropic amorphous phase changes very little with, the T;and increases with increasing R;. Sum of the mass fractions of crystalline orthorhombic phase and the disordered anisotropic phase increases linearly as the same slope as the crystallinity W;determined from DSC measurements with increasing T;or R;and it is higher than the W;for all the samples. The results show that the mass fraction of disordered anisotropic phase is partially devoted by the taut tie molecules （TTM s） in the amorphous state. The dependence of the disordered anisotropic phase on T;and R;supports the mechanism of plastic deformation of fibre structure.
文摘It is suggested that there is a kind of probability wave of the atomic configuration p(R)in crystals that can be deduced from the eigenequation of the ionic interaction Hamiltonian,and it has definite physical meaning. By use of the probability wave of the atomic con-figuration, the occupation probabilities of different kinds of atoms at lattice sites in multi-component solutions can be studied, and the crystal structures of multi-component solutionscan be predicted.
