By adding 1 wt% damage homogenizer（DH）, i.e. carbon black microparticles, into the electrodes of lithiumion batteries, thermal runaway can be mitigated as the battery cells are subjected to impact loadings. In a dro...By adding 1 wt% damage homogenizer（DH）, i.e. carbon black microparticles, into the electrodes of lithiumion batteries, thermal runaway can be mitigated as the battery cells are subjected to impact loadings. In a drop tower test, the generated heat of the modified cells is reduced by nearly 40%, compared with the reference cells. This phenomenon may be attributed to the weakening effect of the carbon black fillers.The shape of the filler grains does not have a pronounced influence on the temperature profile.展开更多
1.Introduction Cemented carbides are composites of WC ceramic phases and metallic Co binders that endow them with superior hardness and excellent toughness.Hard metals are widely used as metal cutting and rock drillin...1.Introduction Cemented carbides are composites of WC ceramic phases and metallic Co binders that endow them with superior hardness and excellent toughness.Hard metals are widely used as metal cutting and rock drilling tools[1,2].Their hardness is believed to be inversely proportional to the sizes of WC grains^([3]).Grain growth inhibitors are widely employed to achieve smaller grain sizes.展开更多
Neutron diffraction and total scattering are combined to investigate a series of single-phase 10-component compositionally complexfluorite-based oxides,[(Pr_(0.375)Nd_(0.375)Yb_(0.25))2(Ti_(0.5)Hf_(0.25)Zr_(0.25))_(2)O...Neutron diffraction and total scattering are combined to investigate a series of single-phase 10-component compositionally complexfluorite-based oxides,[(Pr_(0.375)Nd_(0.375)Yb_(0.25))2(Ti_(0.5)Hf_(0.25)Zr_(0.25))_(2)O_(7)]_(1-x)[(DyHoErNb)O_(7)]_(x),denoted as 10CCFBOxNb.A long-range order-disorder transition(ODT)occurs at x=0.81±0.01 from the ordered pyrochlore to disordered defectfluorite.In contrast to ternary oxides,this ODT occurs abruptly without an observable two-phase region;moreover,the phase stability in 10CCFBOs deviates from the well-established criteria for simpler oxides.Rietveld refinements of neutron diffraction patterns suggest that this ODT occurs via the migration of oxygen anions from the position 48f to 8a,with a smallfinal jump at the ODT;however,the 8a oxygen occupancy changes gradually(without an observable discontinuous jump).We further discover diffuse scattering in Nb-rich compositions,which suggests the presence of short-range order.Using small-box modelling,four compositions near ODT(x=0.75,0.8,0.85,and 1)can be betterfitted by C2221 weberite ordering for the local polyhedral structure at nanoscale.Interestingly,10CCFBO_(0.75)Nb and 10CCFBO_(0.8)Nb possess both long-range pyrochlore order and short-range weberite-type order,which can be understood from severe local distortion of the pyrochlore polyhedral structure.Thus,weberite-type short-range order emerges before the ODT,coexisting and interacting with long-range pyrochlore order.After the ODT,the long-range pyrochlore order vanishes but the short-range weberite-type order persists in the long-range disordered defectfluorite structure.Notably,a drop in the thermal conductivity coincides with emergence of the short-range order,instead of the long-range ODT.展开更多
Two new high-entropy ceramics(HECs)in the weberite and fergusonite structures,along with the unexpected formation of ordered pyrochlore phases with ultrahigh-entropy compositions and an abrupt pyrochlore–weberite tra...Two new high-entropy ceramics(HECs)in the weberite and fergusonite structures,along with the unexpected formation of ordered pyrochlore phases with ultrahigh-entropy compositions and an abrupt pyrochlore–weberite transition,are discovered in a 21-component oxide system.While the Gibbs phase rule allows 21 equilibrium phases,9 out of the 13 compositions examined possess single HEC phases(with ultrahigh ideal configurational entropies:~2.7kB per cation or higher on one sublattice in most cases).Notably,(15RE_(1/15))(Nb_(1/2)Ta_(1/2))O_(4) possess a single monoclinic fergusonite(C2/c)phase,and(15RE_(1/15))_(3)(Nb_(1/2)Ta_(1/2))_(1)O_(7) form a single orthorhombic(C222_(1))weberite phase,where 15RE_(1/15) represents Sc_(1/15)Y_(1/15)La_(1/15)Pr_(1/15)Nd_(1/15)Sm_(1/15)Eu_(1/15)Gd_(1/15)Tb_(1/15)Dy_(1/15)Ho_(1/15)Er_(1/15)Tm_(1/15) Yb_(1/15)Lu_(1/15).Moreover,a series of eight(15RE_(1/15))_(2+x)(Ti_(1/4)Zr_(1/4)Ce_(1/4)Hf_(1/4))_(2−2x)(Nb_(1/2)Ta_(1/2))_(x)O_(7) specimens all exhibit single phases,where a pyrochlore–weberite transition occurs within 0.75<x<0.8125.This cubic-to-orthorhombic transition does not change the temperature-dependent thermal conductivity appreciably,as the amorphous limit may have already been achieved in the ultrahigh-entropy 21-component oxides.These discoveries expand the diversity and complexity of HECs,towards many-component compositionally complex ceramics(CCCs)and ultrahigh-entropy ceramics.展开更多
Computing the grain boundary(GB)counterparts to bulk phase diagrams represents an emerging research direction.Using a classical embrittlement model system Ga-doped Al alloy,this study demonstrates the feasibility of c...Computing the grain boundary(GB)counterparts to bulk phase diagrams represents an emerging research direction.Using a classical embrittlement model system Ga-doped Al alloy,this study demonstrates the feasibility of computing temperature-and composition-dependent GB diagrams to represent not only equilibrium thermodynamic and structural characters,but also mechanical properties.Specifically,hybrid Monte Carlo and molecular dynamics(MC/MD)simulations are used to obtain the equilibrium GB structure as a function of temperature and composition.Simulated GB structures are validated by aberrationcorrected scanning transmission electron microscopy.Subsequently,MD tensile tests are performed on the simulated equilibrium GB structures.GB diagrams are computed for not only GB adsorption and structural disorder,but also interfacial structural and chemical widths,MD ultimate tensile strength,and MD tensile toughness.This study suggests a research direction to investigate GB composition–structure–property relationships via computing GB diagrams of thermodynamic,structural,and mechanical(or potentially other)properties.展开更多
Heusler alloys combined with MgO interfaces exhibit interfacial perpendicular magnetic anisotropy, making them attractive forenergy-efficient spintronic technologies. However, finding suitable Heusler/MgO heterostruct...Heusler alloys combined with MgO interfaces exhibit interfacial perpendicular magnetic anisotropy, making them attractive forenergy-efficient spintronic technologies. However, finding suitable Heusler/MgO heterostructures with desired properties ischallenging due to the vast range of compositions available and the complexity of interfacial structures, particularly for theemerging quaternary Heusler compounds. In this study, we report a high-throughput screening of quaternary-Heusler/MgOheterostructures for spintronic applications. By analyzing various materials descriptors, including formation energy, convex hulldistance, magnetic ordering, lattice misfit, magnetic anisotropy constant, tunnel magnetoresistance, Curie temperature, and atomicsite disordering, we identified 5 promising compounds out of 27,000 quaternary Heusler compounds. These compounds, namelyIrCrAlTi, IrCrGaTi, IrMnZnTi, OsCrAlTa, and TaGaOsCr, show potential for designing energy-efficient perpendicular magnetic tunneljunctions. This work demonstrates an efficient approach using open quantum materials repositories, effective materials descriptors,and high-throughput computational techniques to accelerate the discovery of quaternary-Heusler-based functional materials.展开更多
The growing demand for electric vehicles highlights the need for energy storage solutions with higher densities,spotlighting Li metal anodes as potential successors to traditional Li-ion batteries(LIBs).Achieving long...The growing demand for electric vehicles highlights the need for energy storage solutions with higher densities,spotlighting Li metal anodes as potential successors to traditional Li-ion batteries(LIBs).Achieving longer calendar aging life for Li metal anodes is crucial for their practical use,given their propensity for corrosion due to a low redox potential,which leads to compromised cycling stability and significant capacity loss during storage.Recent research investigated that this susceptibility is mainly dependent on the surface area of Li metal anode and the properties of the solid electrolyte interphase(SEI),particularly its stability and growth rate.Our research adds to this understanding by demonstrating that the amount of Li plating is a key factor in its corrosion during open-circuit storage,as assessed across various electrolytes.We discovered that increasing the Li plating amount effectively reduces Coulombic efficiency(C.E.)loss during aging,due to a lower surface area-to-Li ratio.This implies that the choice of electrolyte for optimal storage life should consider the amount of Li plating,with higher capacities promoting better storage characteristics.展开更多
High-entropy intermetallic compounds(HEICs)were fabricated by mechanical alloying and spark plasma sintering to fill a knowledge gap between the traditional high-entropy alloys(HEAs)and emerging highentropy ceramics(H...High-entropy intermetallic compounds(HEICs)were fabricated by mechanical alloying and spark plasma sintering to fill a knowledge gap between the traditional high-entropy alloys(HEAs)and emerging highentropy ceramics(HECs).Notably,several four-or five-component equimolar aluminides,such as the B2-phase(Fe1/5 Co1/5 Ni1/5 Mn1/5 Cu1/5)Al,have been made into single-phase HEICs for the first time.Thermodynamic modeling and a reversible,temperature-dependent,phase-stability experiment suggest that such B2-phase HEICs are entropy-stabilized phases.The structure of these HEICs resembles that of HECs with high-entropy mixing of fo ur or five elements of nearly equal fractions in one and only one sublattice,but with significant(10%)anti-site defects(differing from typical HECs).A new phase stability rule for forming single B2-phase HEICs is proposed.Five additional HEICs of predominantly D022 phases have also been made.This study broadens the families of equimola r,single-phase,high-entropy materials that have been successfully fabricated.展开更多
A new class of high-entropy M3B4 borides of the Ta_(3)B_(4)-prototyped orthorhombic structure has been synthesized in the bulk form for the first time.Specimens with compositions of(V0.2Cr0.2Nb0.2Mo0.2Ta0.2)3B4 and(V0...A new class of high-entropy M3B4 borides of the Ta_(3)B_(4)-prototyped orthorhombic structure has been synthesized in the bulk form for the first time.Specimens with compositions of(V0.2Cr0.2Nb0.2Mo0.2Ta0.2)3B4 and(V0.2Cr0.2Nb0.2Ta0.2W0.2)_(3)B_(4) were fabricated via reactive spark plasma sintering of high-energy-ball-milled elemental boron and metal precursors.The sintered specimens were〜98.7%in relative densities with virtually no oxide contamination,albeit the presence of minor(4-5 vol%)secondary high-entropy M5B6 phases.Despite that Mo_(3)B_(4) or W_(3)B_(4) are not stable phase,20%of M03B4 and W3B4 can be stabilized into the high-entropy M3B4 borides.Vickers hardness was measured to be 18.6 and 19.8 GPa at a standard load of 9.8 N.This work has further expanded the family of different structures of high-entropy ceramics reported to date.展开更多
The cold sintering process(CSP)and Bi_(2)O_(3)-activated liquid-phase sintering(LPS)are combined to densify Mg-doped NASICON(Na_(3.256)Mg_(0.128)Zr_(1.872)Si_(2)PO_(12))to achieve high densities and conductivities at ...The cold sintering process(CSP)and Bi_(2)O_(3)-activated liquid-phase sintering(LPS)are combined to densify Mg-doped NASICON(Na_(3.256)Mg_(0.128)Zr_(1.872)Si_(2)PO_(12))to achieve high densities and conductivities at reduced temperatures.As an example,a cold-sintered specimen with the addition of 1.1wt%Bi_(2)O_(3)sintering additive achieved a high conductivity of 0.91 mS/cm(with~96%relative density)after annealing at 1000℃;this conductivity is>70%higher than that of a cold-sintered specimen without adding the Bi_(2)O_(3)sintering additive,and it is>700%of the conductivity of a dry-pressed counterpart with the same amount of Bi_(2)O_(3)added,all of which are subjected to the same heating profile.The highest conductivity achieved in this study via combining CSP and Bi_(2)O_(3)-activated LSP is>1.5 mS/cm.This study suggests an opportunity to combine the new CSP with the traditional LPS to sinter solid electrolytes to achieve high densities and conductivities at reduced temperatures.This combined CSP-LPS approach can be extended to a broad range of other materials to fabricate the“thermally fragile”solid electrolytes or solid-state battery systems,where reducing the processing temperature is often desirable.展开更多
Composites of Na_(0.44)Mn O_2, Na_(0.7)Mn O_(2.05), and Na_(0.91) Mn O_2 were synthesized by facile solid-state reaction, ball milling, and annealing methods. Two different composites of identical overall composition ...Composites of Na_(0.44)Mn O_2, Na_(0.7)Mn O_(2.05), and Na_(0.91) Mn O_2 were synthesized by facile solid-state reaction, ball milling, and annealing methods. Two different composites of identical overall composition but drastically different morphologies and microstructures were synthesized. A composite of a hierarchical porous microstructure with primary and secondary particles(i.e., a "meatball-like" microstructure) achieved an excellent stable capacity of 126 m A h g^(-1) after 100 cycles. The rate capability of the composite could be dramatically enhanced by another round of high-energy ball milling and reannealing; subsequently, a composite that was made up of irregular rods was obtained, for which the capacity was improved by more than 230% to achieve ~53 m A h g^(-1) at a particularly high discharge rate of 50 C. This study demonstrated the feasibility of tailoring the electrochemical performance of electrode materials by simply changing their microstructures via facile ball milling and heat treatments, which can be particularly useful for optimizing composite electrodes for sodium-ion batteries.展开更多
Entropic stabilized ABO_(3) perovskite oxides promise many applications,including the two-step solar thermochemical hydrogen(STCH)production.Using binary and quaternary A-site mixed{A}FeO_(3) as a model system,we reve...Entropic stabilized ABO_(3) perovskite oxides promise many applications,including the two-step solar thermochemical hydrogen(STCH)production.Using binary and quaternary A-site mixed{A}FeO_(3) as a model system,we reveal that as more cation types,especially above four,are mixed on the A-site,the cell lattice becomes more cubic-like but the local Fe–O octahedrons are more distorted.By comparing four different Density Functional Theory-informed statistical models with experiments,we show that the oxygen vacancy formation energies(E^(f)_(V))distribution and the vacancy interactions must be considered to predict the oxygen non-stoichiometry(δ)accurately.For STCH applications,the E^(f)_(V) distribution,including both the average and the spread,can be optimized jointly to improveΔδ(difference ofδbetween the two-step conditions)in some hydrogen production levels.This model can be used to predict the range of water splitting that can be thermodynamically improved by mixing cations in{A}FeO_(3) perovskites.展开更多
A high-entropy metal disilicide,(Mo_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)W_(0.2))Si_(2),has been successfully synthesized.X-ray diffraction(XRD),energy dispersive X-ray spectroscopy(EDX),and electron backscatter diffraction(E...A high-entropy metal disilicide,(Mo_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)W_(0.2))Si_(2),has been successfully synthesized.X-ray diffraction(XRD),energy dispersive X-ray spectroscopy(EDX),and electron backscatter diffraction(EBSD)collectively show the formation of a single high-entropy silicide phase.This high-entropy(Mo_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)W_(0.2))Si_(2) possesses a hexagonal C40 crystal structure with ABC stacking sequence and a space group of P6222.This discovery expands the known families of high-entropy materials from metals,oxides,borides,carbides,and nitrides to a silicide,for the first time to our knowledge,as well as demonstrating that a new,non-cubic,crystal structure(with lower symmetry)can be made into highentropy phase.This(Mo_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)W_(0.2))Si_(2) exhibits high nanohardness of 16.7±1.9 GPa and Vickers hardness of 11.6±0.5 GPa.Moreover,it has a low thermal conductivity of 6.9±1.1Wm^(-1) K^(-1),which is approximately one order of magnitude lower than that of the widely-used tetragonal MoSi_(2) and ~1/3 of those reported values for the hexagonal NbSi_(2) and TaSi_(2) with the same crystal structure.展开更多
A low-carbon future demands more affordable batteries utilizing abundant elements with sustainable end-of-life battery management.Despite the economic and environmental advantages of Li-MnO_(2)batteries,their applica-...A low-carbon future demands more affordable batteries utilizing abundant elements with sustainable end-of-life battery management.Despite the economic and environmental advantages of Li-MnO_(2)batteries,their applica-tion so far has been largely constrained to primary batteries.Here,we demonstrate that one of the major limiting factors preventing the stable cycling of Li-MnO_(2)batteries,Mn dissolution,can be effectively mitigated by employing a common ether electrolyte,1 mol/L lithium bis(trifluorometha-nesulfonyl)imide(LiTFSI)in 1,3-dioxane(DOL)/1,2-dimethoxyethane(DME).We discover that the suppression of this dissolution enables highly reversible cycling of the MnO_(2)cathode regardless of the synthesized phase and morphology.Moreover,we find that both the LiPF_(6)salt and carbonate solvents present in conventional electrolytes are responsible for previous cycling challenges.The ether electrolyte,paired with MnO_(2)cathodes is able to demonstrate stable cycling performance at various rates,even at elevated temperature such as 60℃.Our discovery not only represents a defining step in Li-MnO_(2)batteries with extended life but provides design criteria of electrolytes for vast manganese-based cathodes in rechargeable batteries.展开更多
Grain boundaries(GBs)can be treated as two-dimensional(2-D)interfacial phases(also called“complexions”)that can undergo interfacial phase-like transitions.As bulk phase diagrams and calculation of phase diagram(CALP...Grain boundaries(GBs)can be treated as two-dimensional(2-D)interfacial phases(also called“complexions”)that can undergo interfacial phase-like transitions.As bulk phase diagrams and calculation of phase diagram(CALPHAD)methods serve as a foundation for modern materials science,we propose to extend them to GBs to have equally significant impacts.This perspective article reviews a series of studies to compute the GB counterparts to bulk phase diagrams.First,a phenomenological interfacial thermodynamic model was developed to construct GB lambda diagrams to forecast high-temperature GB disordering and related trends in sintering and other properties for both metallic and ceramic materials.In parallel,an Ising-type lattice statistical thermodynamic model was utilized to construct GB adsorption(segregation)diagrams,which predicted first-order GB adsorption transitions and critical phenomena.These two simplified thermodynamic models emphasize the GB structural(disordering)and chemical(adsorption)aspects,respectively.Subsequently,hybrid Monte Carlo and molecular dynamics atomistic simulations were used to compute more rigorous and accurate GB“phase”diagrams.Computed GB diagrams of thermodynamic and structural properties were further extended to include mechanical properties.Moreover,machine learning algorithms were combined with atomistic simulations to predict GB properties as functions of four independent compositional variables and temperature in a 5-D space for a given GB in high-entropy alloys or as functions of five GB macroscopic(crystallographic)degrees of freedom plus temperature and composition for a binary alloy in a 7-D space.Other relevant studies are also examined.Future perspective and outlook,including two emerging fields of high-entropy grain boundaries(HEGBs)and electrically(or electrochemically)induced GB transitions,are discussed.展开更多
基金supported by the Advanced Research Projects Agency-Energy(ARPA-E)(No.DE-AR0000396)
文摘By adding 1 wt% damage homogenizer（DH）, i.e. carbon black microparticles, into the electrodes of lithiumion batteries, thermal runaway can be mitigated as the battery cells are subjected to impact loadings. In a drop tower test, the generated heat of the modified cells is reduced by nearly 40%, compared with the reference cells. This phenomenon may be attributed to the weakening effect of the carbon black fillers.The shape of the filler grains does not have a pronounced influence on the temperature profile.
基金the support from the National Natural Science Foundation of China(Nos.51871058 and 51701170)Financial support from the Project of Science and Technology Plan of Fujian Province(No.2018J01520)the Talented Youth Scientist Support Program of the Eyas Program of Fujian Province。
文摘1.Introduction Cemented carbides are composites of WC ceramic phases and metallic Co binders that endow them with superior hardness and excellent toughness.Hard metals are widely used as metal cutting and rock drilling tools[1,2].Their hardness is believed to be inversely proportional to the sizes of WC grains^([3]).Grain growth inhibitors are widely employed to achieve smaller grain sizes.
基金supported by the National Science Foundation(NSF)via Grant No.DMR-2026193.A portion of this research used resources at the Spallation Neutron Source,a DOE Office of Science User Facility operated by the ORNL.The STEM work was performed at the Irvine Materials Research Institute(IMRI).
文摘Neutron diffraction and total scattering are combined to investigate a series of single-phase 10-component compositionally complexfluorite-based oxides,[(Pr_(0.375)Nd_(0.375)Yb_(0.25))2(Ti_(0.5)Hf_(0.25)Zr_(0.25))_(2)O_(7)]_(1-x)[(DyHoErNb)O_(7)]_(x),denoted as 10CCFBOxNb.A long-range order-disorder transition(ODT)occurs at x=0.81±0.01 from the ordered pyrochlore to disordered defectfluorite.In contrast to ternary oxides,this ODT occurs abruptly without an observable two-phase region;moreover,the phase stability in 10CCFBOs deviates from the well-established criteria for simpler oxides.Rietveld refinements of neutron diffraction patterns suggest that this ODT occurs via the migration of oxygen anions from the position 48f to 8a,with a smallfinal jump at the ODT;however,the 8a oxygen occupancy changes gradually(without an observable discontinuous jump).We further discover diffuse scattering in Nb-rich compositions,which suggests the presence of short-range order.Using small-box modelling,four compositions near ODT(x=0.75,0.8,0.85,and 1)can be betterfitted by C2221 weberite ordering for the local polyhedral structure at nanoscale.Interestingly,10CCFBO_(0.75)Nb and 10CCFBO_(0.8)Nb possess both long-range pyrochlore order and short-range weberite-type order,which can be understood from severe local distortion of the pyrochlore polyhedral structure.Thus,weberite-type short-range order emerges before the ODT,coexisting and interacting with long-range pyrochlore order.After the ODT,the long-range pyrochlore order vanishes but the short-range weberite-type order persists in the long-range disordered defectfluorite structure.Notably,a drop in the thermal conductivity coincides with emergence of the short-range order,instead of the long-range ODT.
基金The work is supported by the National Science Foundation(NSF)in the Ceramics program via Grant No.DMR2026193This work utilized the shared facilities at the San Diego Nanotechnology Infrastructure of UCSD,a member of the National Nanotechnology Coordinated Infrastructure(supported by the NSF ECCS-1542148)the Irvine Materials Research Institute(partially supported by NSF DMR-2011967 through UCI CCAM).
文摘Two new high-entropy ceramics(HECs)in the weberite and fergusonite structures,along with the unexpected formation of ordered pyrochlore phases with ultrahigh-entropy compositions and an abrupt pyrochlore–weberite transition,are discovered in a 21-component oxide system.While the Gibbs phase rule allows 21 equilibrium phases,9 out of the 13 compositions examined possess single HEC phases(with ultrahigh ideal configurational entropies:~2.7kB per cation or higher on one sublattice in most cases).Notably,(15RE_(1/15))(Nb_(1/2)Ta_(1/2))O_(4) possess a single monoclinic fergusonite(C2/c)phase,and(15RE_(1/15))_(3)(Nb_(1/2)Ta_(1/2))_(1)O_(7) form a single orthorhombic(C222_(1))weberite phase,where 15RE_(1/15) represents Sc_(1/15)Y_(1/15)La_(1/15)Pr_(1/15)Nd_(1/15)Sm_(1/15)Eu_(1/15)Gd_(1/15)Tb_(1/15)Dy_(1/15)Ho_(1/15)Er_(1/15)Tm_(1/15) Yb_(1/15)Lu_(1/15).Moreover,a series of eight(15RE_(1/15))_(2+x)(Ti_(1/4)Zr_(1/4)Ce_(1/4)Hf_(1/4))_(2−2x)(Nb_(1/2)Ta_(1/2))_(x)O_(7) specimens all exhibit single phases,where a pyrochlore–weberite transition occurs within 0.75<x<0.8125.This cubic-to-orthorhombic transition does not change the temperature-dependent thermal conductivity appreciably,as the amorphous limit may have already been achieved in the ultrahigh-entropy 21-component oxides.These discoveries expand the diversity and complexity of HECs,towards many-component compositionally complex ceramics(CCCs)and ultrahigh-entropy ceramics.
文摘Computing the grain boundary(GB)counterparts to bulk phase diagrams represents an emerging research direction.Using a classical embrittlement model system Ga-doped Al alloy,this study demonstrates the feasibility of computing temperature-and composition-dependent GB diagrams to represent not only equilibrium thermodynamic and structural characters,but also mechanical properties.Specifically,hybrid Monte Carlo and molecular dynamics(MC/MD)simulations are used to obtain the equilibrium GB structure as a function of temperature and composition.Simulated GB structures are validated by aberrationcorrected scanning transmission electron microscopy.Subsequently,MD tensile tests are performed on the simulated equilibrium GB structures.GB diagrams are computed for not only GB adsorption and structural disorder,but also interfacial structural and chemical widths,MD ultimate tensile strength,and MD tensile toughness.This study suggests a research direction to investigate GB composition–structure–property relationships via computing GB diagrams of thermodynamic,structural,and mechanical(or potentially other)properties.
基金This work was supported by the Academic Senate General Campus Research Grant Committee at the University of California San DiegoThis work used the Expanse cluster at San Diego Supercomputer Center through allocation DMR160045 from the Extreme Science and Engineering Discovery Environment(XSEDE),which was supported by National Science Foundation grant number#1548562,Acknowl-edgement is made to the donors of the American Chemical Society Petroleum Research Fund for partial support of this research.
文摘Heusler alloys combined with MgO interfaces exhibit interfacial perpendicular magnetic anisotropy, making them attractive forenergy-efficient spintronic technologies. However, finding suitable Heusler/MgO heterostructures with desired properties ischallenging due to the vast range of compositions available and the complexity of interfacial structures, particularly for theemerging quaternary Heusler compounds. In this study, we report a high-throughput screening of quaternary-Heusler/MgOheterostructures for spintronic applications. By analyzing various materials descriptors, including formation energy, convex hulldistance, magnetic ordering, lattice misfit, magnetic anisotropy constant, tunnel magnetoresistance, Curie temperature, and atomicsite disordering, we identified 5 promising compounds out of 27,000 quaternary Heusler compounds. These compounds, namelyIrCrAlTi, IrCrGaTi, IrMnZnTi, OsCrAlTa, and TaGaOsCr, show potential for designing energy-efficient perpendicular magnetic tunneljunctions. This work demonstrates an efficient approach using open quantum materials repositories, effective materials descriptors,and high-throughput computational techniques to accelerate the discovery of quaternary-Heusler-based functional materials.
基金supported by Intelligence Advanced Research Projects Activity under Robust Energy Sources for Intelligence Logistics In Extreme,Novel and Challenging Environments(RESILIENCE)program.
文摘The growing demand for electric vehicles highlights the need for energy storage solutions with higher densities,spotlighting Li metal anodes as potential successors to traditional Li-ion batteries(LIBs).Achieving longer calendar aging life for Li metal anodes is crucial for their practical use,given their propensity for corrosion due to a low redox potential,which leads to compromised cycling stability and significant capacity loss during storage.Recent research investigated that this susceptibility is mainly dependent on the surface area of Li metal anode and the properties of the solid electrolyte interphase(SEI),particularly its stability and growth rate.Our research adds to this understanding by demonstrating that the amount of Li plating is a key factor in its corrosion during open-circuit storage,as assessed across various electrolytes.We discovered that increasing the Li plating amount effectively reduces Coulombic efficiency(C.E.)loss during aging,due to a lower surface area-to-Li ratio.This implies that the choice of electrolyte for optimal storage life should consider the amount of Li plating,with higher capacities promoting better storage characteristics.
基金supported by a Vannevar Bush Faculty Fellowship sponsored by the Basic Research Office of the Assistant Secretary of Defense for Research and Engineeringfunded by the Office of Naval Research(N00014-16-1-2569)funding support from State Key Laboratory of High Performance and Complex Manufacturing at Central South University(ZZYJKT2018-04)
文摘High-entropy intermetallic compounds(HEICs)were fabricated by mechanical alloying and spark plasma sintering to fill a knowledge gap between the traditional high-entropy alloys(HEAs)and emerging highentropy ceramics(HECs).Notably,several four-or five-component equimolar aluminides,such as the B2-phase(Fe1/5 Co1/5 Ni1/5 Mn1/5 Cu1/5)Al,have been made into single-phase HEICs for the first time.Thermodynamic modeling and a reversible,temperature-dependent,phase-stability experiment suggest that such B2-phase HEICs are entropy-stabilized phases.The structure of these HEICs resembles that of HECs with high-entropy mixing of fo ur or five elements of nearly equal fractions in one and only one sublattice,but with significant(10%)anti-site defects(differing from typical HECs).A new phase stability rule for forming single B2-phase HEICs is proposed.Five additional HEICs of predominantly D022 phases have also been made.This study broadens the families of equimola r,single-phase,high-entropy materials that have been successfully fabricated.
基金an office of Naval Research MURI Program(Grant No.N00014-15-1-2863)Qizhang YAN and Jian LUO also acknowledge partial support from the Air Force Office of Scientific Research(Grant No.FA9550-19-1-01327)for the microscopy work.
文摘A new class of high-entropy M3B4 borides of the Ta_(3)B_(4)-prototyped orthorhombic structure has been synthesized in the bulk form for the first time.Specimens with compositions of(V0.2Cr0.2Nb0.2Mo0.2Ta0.2)3B4 and(V0.2Cr0.2Nb0.2Ta0.2W0.2)_(3)B_(4) were fabricated via reactive spark plasma sintering of high-energy-ball-milled elemental boron and metal precursors.The sintered specimens were〜98.7%in relative densities with virtually no oxide contamination,albeit the presence of minor(4-5 vol%)secondary high-entropy M5B6 phases.Despite that Mo_(3)B_(4) or W_(3)B_(4) are not stable phase,20%of M03B4 and W3B4 can be stabilized into the high-entropy M3B4 borides.Vickers hardness was measured to be 18.6 and 19.8 GPa at a standard load of 9.8 N.This work has further expanded the family of different structures of high-entropy ceramics reported to date.
基金acknowledge partial support by a Vannevar Bush Faculty Fellowship sponsored by the Basic Research Office of the Assistant Secretary of Defense for Research and Engineering and funded by the Office of Naval Research through grant N00014-16-1-2569.
文摘The cold sintering process(CSP)and Bi_(2)O_(3)-activated liquid-phase sintering(LPS)are combined to densify Mg-doped NASICON(Na_(3.256)Mg_(0.128)Zr_(1.872)Si_(2)PO_(12))to achieve high densities and conductivities at reduced temperatures.As an example,a cold-sintered specimen with the addition of 1.1wt%Bi_(2)O_(3)sintering additive achieved a high conductivity of 0.91 mS/cm(with~96%relative density)after annealing at 1000℃;this conductivity is>70%higher than that of a cold-sintered specimen without adding the Bi_(2)O_(3)sintering additive,and it is>700%of the conductivity of a dry-pressed counterpart with the same amount of Bi_(2)O_(3)added,all of which are subjected to the same heating profile.The highest conductivity achieved in this study via combining CSP and Bi_(2)O_(3)-activated LSP is>1.5 mS/cm.This study suggests an opportunity to combine the new CSP with the traditional LPS to sinter solid electrolytes to achieve high densities and conductivities at reduced temperatures.This combined CSP-LPS approach can be extended to a broad range of other materials to fabricate the“thermally fragile”solid electrolytes or solid-state battery systems,where reducing the processing temperature is often desirable.
基金supported by the U.S.NSF(Grant No.DMR-1320615)subsequently an NSSEFF fellowship(Grant No.N00014-15-1-0030)
文摘Composites of Na_(0.44)Mn O_2, Na_(0.7)Mn O_(2.05), and Na_(0.91) Mn O_2 were synthesized by facile solid-state reaction, ball milling, and annealing methods. Two different composites of identical overall composition but drastically different morphologies and microstructures were synthesized. A composite of a hierarchical porous microstructure with primary and secondary particles(i.e., a "meatball-like" microstructure) achieved an excellent stable capacity of 126 m A h g^(-1) after 100 cycles. The rate capability of the composite could be dramatically enhanced by another round of high-energy ball milling and reannealing; subsequently, a composite that was made up of irregular rods was obtained, for which the capacity was improved by more than 230% to achieve ~53 m A h g^(-1) at a particularly high discharge rate of 50 C. This study demonstrated the feasibility of tailoring the electrochemical performance of electrode materials by simply changing their microstructures via facile ball milling and heat treatments, which can be particularly useful for optimizing composite electrodes for sodium-ion batteries.
基金This work is supported by the U.S.Department of Energy’s Office of Energy Efficiency and Renewable Energy(EERE)under Agreement Number DE-EE0008839managed by the Hydrogen and Fuel Cell Technologies Office in the Fiscal Year 2019 H2@SCALE program+1 种基金The Alliance for Sustainable Energy,LLC,operates and manages the National Renewable Energy Laboratory for the US.Department of Energy(DOE)under Contract No.DE-AC36-08GO28308The research was performed using computational resources sponsored by the Department of Energy’s Office of Energy Efficiency and Renewable Energy and located at the National Renewable Energy Laboratory and was conducted using computational resources and services at the Center for Computation and Visualization,Brown University.
文摘Entropic stabilized ABO_(3) perovskite oxides promise many applications,including the two-step solar thermochemical hydrogen(STCH)production.Using binary and quaternary A-site mixed{A}FeO_(3) as a model system,we reveal that as more cation types,especially above four,are mixed on the A-site,the cell lattice becomes more cubic-like but the local Fe–O octahedrons are more distorted.By comparing four different Density Functional Theory-informed statistical models with experiments,we show that the oxygen vacancy formation energies(E^(f)_(V))distribution and the vacancy interactions must be considered to predict the oxygen non-stoichiometry(δ)accurately.For STCH applications,the E^(f)_(V) distribution,including both the average and the spread,can be optimized jointly to improveΔδ(difference ofδbetween the two-step conditions)in some hydrogen production levels.This model can be used to predict the range of water splitting that can be thermodynamically improved by mixing cations in{A}FeO_(3) perovskites.
基金the partial financial support from an Office of Naval Research MURI program(grant no.N00014-15-1-2863,Program Mangers:Dr.Kenny Lipkowitz and Dr.Eric Wuchina)funding from the National Science Foundation,Grant No.CBET-1706388supported by the Deparment of Defense(DoD)through the National Defense Science and Engineering Graduate Fellowship(NDSEG)program as well as the ARCS foundation.
文摘A high-entropy metal disilicide,(Mo_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)W_(0.2))Si_(2),has been successfully synthesized.X-ray diffraction(XRD),energy dispersive X-ray spectroscopy(EDX),and electron backscatter diffraction(EBSD)collectively show the formation of a single high-entropy silicide phase.This high-entropy(Mo_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)W_(0.2))Si_(2) possesses a hexagonal C40 crystal structure with ABC stacking sequence and a space group of P6222.This discovery expands the known families of high-entropy materials from metals,oxides,borides,carbides,and nitrides to a silicide,for the first time to our knowledge,as well as demonstrating that a new,non-cubic,crystal structure(with lower symmetry)can be made into highentropy phase.This(Mo_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)W_(0.2))Si_(2) exhibits high nanohardness of 16.7±1.9 GPa and Vickers hardness of 11.6±0.5 GPa.Moreover,it has a low thermal conductivity of 6.9±1.1Wm^(-1) K^(-1),which is approximately one order of magnitude lower than that of the widely-used tetragonal MoSi_(2) and ~1/3 of those reported values for the hexagonal NbSi_(2) and TaSi_(2) with the same crystal structure.
基金supported by NSF through the UC San Diego Materials Research Science and Engineering Center(UCSD MRSEC)DMR-2011924Part of the work used the UCSD-MTI Battery Fabrication Facility and the UCSDArbin Battery Testing Facility.Electron microscopic characterization was performed at the San Diego Nanotechnology Infrastructure(SDNI)of UCSD,a member of the National Nanotechnology Coordinated Infrastructure,which is supported by the National Science Foundation(Grant No.ECCS-1542148)Use of the Stanford Synchrotron Radiation Light source,SLAC National Accelerator Laboratory,is supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,under Contract No.DE-AC02-76SF00515.
文摘A low-carbon future demands more affordable batteries utilizing abundant elements with sustainable end-of-life battery management.Despite the economic and environmental advantages of Li-MnO_(2)batteries,their applica-tion so far has been largely constrained to primary batteries.Here,we demonstrate that one of the major limiting factors preventing the stable cycling of Li-MnO_(2)batteries,Mn dissolution,can be effectively mitigated by employing a common ether electrolyte,1 mol/L lithium bis(trifluorometha-nesulfonyl)imide(LiTFSI)in 1,3-dioxane(DOL)/1,2-dimethoxyethane(DME).We discover that the suppression of this dissolution enables highly reversible cycling of the MnO_(2)cathode regardless of the synthesized phase and morphology.Moreover,we find that both the LiPF_(6)salt and carbonate solvents present in conventional electrolytes are responsible for previous cycling challenges.The ether electrolyte,paired with MnO_(2)cathodes is able to demonstrate stable cycling performance at various rates,even at elevated temperature such as 60℃.Our discovery not only represents a defining step in Li-MnO_(2)batteries with extended life but provides design criteria of electrolytes for vast manganese-based cathodes in rechargeable batteries.
基金National Science Foundation,Grant/Award Number:DMR-2011967Air Force Office of Scientific Research,Grant/Award Numbers:FA9550-19-1-0327,FA9550-22-1-0413+1 种基金Army Research Office,Grant/Award Number:W911NF2210071Vannevar Bush Faculty Fellowship,Grant/Award Number:N00014-16-2569。
文摘Grain boundaries(GBs)can be treated as two-dimensional(2-D)interfacial phases(also called“complexions”)that can undergo interfacial phase-like transitions.As bulk phase diagrams and calculation of phase diagram(CALPHAD)methods serve as a foundation for modern materials science,we propose to extend them to GBs to have equally significant impacts.This perspective article reviews a series of studies to compute the GB counterparts to bulk phase diagrams.First,a phenomenological interfacial thermodynamic model was developed to construct GB lambda diagrams to forecast high-temperature GB disordering and related trends in sintering and other properties for both metallic and ceramic materials.In parallel,an Ising-type lattice statistical thermodynamic model was utilized to construct GB adsorption(segregation)diagrams,which predicted first-order GB adsorption transitions and critical phenomena.These two simplified thermodynamic models emphasize the GB structural(disordering)and chemical(adsorption)aspects,respectively.Subsequently,hybrid Monte Carlo and molecular dynamics atomistic simulations were used to compute more rigorous and accurate GB“phase”diagrams.Computed GB diagrams of thermodynamic and structural properties were further extended to include mechanical properties.Moreover,machine learning algorithms were combined with atomistic simulations to predict GB properties as functions of four independent compositional variables and temperature in a 5-D space for a given GB in high-entropy alloys or as functions of five GB macroscopic(crystallographic)degrees of freedom plus temperature and composition for a binary alloy in a 7-D space.Other relevant studies are also examined.Future perspective and outlook,including two emerging fields of high-entropy grain boundaries(HEGBs)and electrically(or electrochemically)induced GB transitions,are discussed.
