Tantalum(Ta)alloys have been widely utilized in rocket,air-breathing engines,and airframe applications.However,traditional Ta alloys suffer from insufficient strength at ultra-high temperature,making it challenging to...Tantalum(Ta)alloys have been widely utilized in rocket,air-breathing engines,and airframe applications.However,traditional Ta alloys suffer from insufficient strength at ultra-high temperature,making it challenging to satisfy the design requirements for next-generation aerospace equipment.We report a novel strategy to design Ta alloys with superior mechanical properties by integrating the multi-principal element concept with compositionally complex carbides.By introducing multiple refractory elements and C,the resultant alloys displayed a thermally stable microstructure consisting of two phases.With the increasing C contents,the microstructure evolved from hypoeutectic to eutectic and then to hypereutectic.These varying microstructural characteristics influenced crack blunting and dislocation accumulation behaviors,leading to different softening resistance at 1600℃and plasticity at room temperature.Benefiting from the strengthening effects of solid solution and compositionally complex carbides,these alloys exhibited a high strength of~600 MPa at 1600℃,significantly superior than that of traditional Ta alloys.展开更多
This study focuses on compositionally complex alloys(CCAs),aiming to achieve a balance between high strength and low density for new energy and aerospace applications.The composition of AlCrFeNiTi_(x) CCAs is strategi...This study focuses on compositionally complex alloys(CCAs),aiming to achieve a balance between high strength and low density for new energy and aerospace applications.The composition of AlCrFeNiTi_(x) CCAs is strategically guided by employing density functional theory and the theoretical design of thermodynamic calculations.Bulk CCAs,particularly AlCrFeNiTi_(0.25) alloy,demonstrate remarkable specific yield strength(1640.8 MPa) and 22.7% maximum strain.The incorporation of Ti facilitates the formation of lightweight and high-strength L2_(1)phase,contributing to the overall high specific strength.Synergistic effects of grain boundary strengthening,solid solution strengthening,Orowan strengthening and Peierls flow stress further enhance strength.Detailed exploration of micros tructural changes during fracture reveals the role of ordered phases in suppressing crack propagation and absorbing energy within disordered phases,thereby improving the toughness and fracture resistance of CCAs.These methods and discoveries establish a robust foundation for advancing the development of novel lightweight CCAs.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
Here,we study the hydride formation in a metastable Ti-33Zr-22Hf-11Ta(at.%)refractory high entropy alloy(RHEA).Deviating to non-equiatomic compositions of RHEAs promotes the formation of transformation-induced plastic...Here,we study the hydride formation in a metastable Ti-33Zr-22Hf-11Ta(at.%)refractory high entropy alloy(RHEA).Deviating to non-equiatomic compositions of RHEAs promotes the formation of transformation-induced plasticity where the body-centered cubic phase transforms to hexagonal close-packed(HCP)phase.It is found that the phase transformation capability assists the hydride formation due to the low solubility of hydrogen within the HCP phase.In this study,hydrogen is charged via electrochemical polishing and the corresponding phase transformation is activated in the metastable RHEAs.The newly formed HCP phase interacts with hydrogen to form a face-centered cubic hydride verified by electron energy loss spectroscopy.This work provides a primary exploration of the formation of compositionally complex metal hydrides in the metastable RHEAs,which are potential candidates for future hydrogen storage material design.展开更多
1.Introduction Multi-principal element alloys(MPEAs),with compositions in the central region of the multicomponent phase diagram,have been dubbed"high-entropy alloys"(HEAs)in recent years[1-11].A more genera...1.Introduction Multi-principal element alloys(MPEAs),with compositions in the central region of the multicomponent phase diagram,have been dubbed"high-entropy alloys"(HEAs)in recent years[1-11].A more general term currently accepted by the community for these MPEAs is complex concentrated alloys or compositionally complex alloys(CCAs)[12].These alloys are usually based on single-phase multi-principal element solid solutions,with no need or possibility to distinguish which species constitutes the solvent and which ones are solutes.This Viewpoint and Perspective article focuses on a salient feature in the internal structure of MPEAs,different from traditional metals and solvent-(dilute)solute solutions.Specifically,the unusual trait to be highlighted for these heavily concentrated solutions is their inherent chemical inhomogeneity on the nanoscale,in terms of the high propensity for compositional fluctuation and local chemical order.展开更多
Advanced structural materials with superb mechanical properties at ultrahigh temperatures are essential for aerospace and power-generation sectors.Refractory multi-principal element alloys(RMPEAs)are promising candida...Advanced structural materials with superb mechanical properties at ultrahigh temperatures are essential for aerospace and power-generation sectors.Refractory multi-principal element alloys(RMPEAs)are promising candidates,but they face challenges such as limited plasticity at room temperatures and insufficient strength at ultrahigh temperatures.In this work,we investigated the mechanical properties and microstructures of RMPEA reinforced with compositional complex carbides and demonstrated that tailoring the carbon content can significantly alter their microstructures and enhance mechanical properties.Specifically,the W_(30)Ta_(30)Mo_(15)Nb_(15)C_(10)alloy achieved an ultrahigh strength of 896 MPa at 1600℃ and a plasticity of∼8%at room temperatures.The strengthening effect arises from multi-principal element mixing and robust dislocation hindering at the phase interfaces between the carbides and the matrix,while the room temperature plasticity is attributed to crack buffering facilitated by the highly saturated solid solution matrix.Our study highlights the potential of compositional complex carbide to enhance the mechanical properties of RMPEAs,offering a promising approach for the development of advanced structural materials for ultrahigh temperature applications.展开更多
Accurate boundary conditions of composite material plates with different holes are founded to settle boundary condition problems of complex holes by conformal mapping method upon the nonhomogeneous anisotropic elastic...Accurate boundary conditions of composite material plates with different holes are founded to settle boundary condition problems of complex holes by conformal mapping method upon the nonhomogeneous anisotropic elastic and complex function theory. And then the two stress functions required were founded on Cauchy integral by boundary conditions. The final stress distributions of opening structure and the analytical solution on composite material plate with rectangle hole and wing manholes were achieved. The influences on hole-edge stress concentration factors are discussed under different loads and fiber direction cases, and then contrast calculates are carried through FEM.展开更多
During the whole service lifetime of aircraft structures with composite materials,impacts are inevitable and can usually cause severe but barely visible damages.Since the occurrences of impact are random and unpredict...During the whole service lifetime of aircraft structures with composite materials,impacts are inevitable and can usually cause severe but barely visible damages.Since the occurrences of impact are random and unpredictable,it is a hotspot direction to develop an online impact monitoring system that can meet strict limitations of aerospace applications including small size,light weight,and low power consumption.Piezoelectric(PZT)sensor,being able to generate impact response signals with no external power and cover a large-scale structure with only a small amount of them,is a promising choice.Meanwhile,for real systems,networks with multiple nodes are normally required to monitor large-scale structures in a global way to identify any impact localization confliction,yet the existing studies are mostly evaluated with single nodes instead of networks.Therefore,in this paper,based on a new low-power node designed,a Bluetooth-based digital impact monitoring PZT sensor network is proposed for the first time with its global confliction-solving impact localization method.Evaluations of the system as a network are researched and analyzed on a complex real aircraft wing box for a global confliction-solving impact localization,showing a satisfying high accuracy.展开更多
The accurate and efficient analysis of anisotropic heat conduction problems in complex composites is crucial for structural design and performance evaluation. Traditional numerical methods, such as the finite element ...The accurate and efficient analysis of anisotropic heat conduction problems in complex composites is crucial for structural design and performance evaluation. Traditional numerical methods, such as the finite element method(FEM), often face a trade-off between calculation accuracy and efficiency. In this paper, we propose a quasi-smooth manifold element(QSME) method to address this challenge, and provide the accurate and efficient analysis of two-dimensional(2D) anisotropic heat conduction problems in composites with complex geometry. The QSME approach achieves high calculation precision by a high-order local approximation that ensures the first-order derivative continuity.The results demonstrate that the QSME method is robust and stable, offering both high accuracy and efficiency in the heat conduction analysis. With the same degrees of freedom(DOFs), the QSME method can achieve at least an order of magnitude higher calculation accuracy than the traditional FEM. Additionally, under the same level of calculation error, the QSME method requires 10 times fewer DOFs than the traditional FEM. The versatility of the proposed QSME method extends beyond anisotropic heat conduction problems in complex composites. The proposed QSME method can also be applied to other problems, including fluid flows, mechanical analyses, and other multi-field coupled problems, providing accurate and efficient numerical simulations.展开更多
Compositionally complex solid electrolyte(Li_(0.375)Sr_(0.4375))(Ta_(0.375)Nb_(0.375)Zr_(0.125)Hf_(0.125))O_(3)(LSTNZH)samples are synthesized using different sintering temperatures,durations,and cooling conditions(fu...Compositionally complex solid electrolyte(Li_(0.375)Sr_(0.4375))(Ta_(0.375)Nb_(0.375)Zr_(0.125)Hf_(0.125))O_(3)(LSTNZH)samples are synthesized using different sintering temperatures,durations,and cooling conditions(furnace cooling(FC)vs.air quenching(AQ)).The temperature-dependent grain growth has been examined to investigate the microstructural evolution and the origin of exaggerated(abnormal)grain growth.At moderate temperatures,the grain growth of LSTNZH follows a cubic root growth model with an Arrhenius temperature dependence.With increasing temperature,bimodal microstructures develop,and the Arrhenius temperature dependence breaks down.Notably,increasing the temperature induces increased Nb segregation at general grain boundaries(GBs),in contrast to classical GB segregation models but suggesting premelting-like GB disordering,which can explain the observed abnormal grain growth(AGG).In addition,the large grains become faceted with increasing temperature,which occurs concurrently with the temperature-induced transitions in GB segregation and grain growth,thereby further supporting the occurrence of a GB phase-like(complexion)transition.The impacts on the densification,ionic conductivity,and hardness are also examined.This work provides a new insight into the fundamental understanding of the grain growth mechanisms of the emergent class of medium-and high-entropy compositionally complex ceramics(CCCs),which is essential for tailoring microstructures and material properties.展开更多
A broad tunability of the thermoelectric and mechanical properties of CoSb_(3) has been demonstrated by adjusting the composition with the addition of an increasing number of elements.However,such a strategy may negat...A broad tunability of the thermoelectric and mechanical properties of CoSb_(3) has been demonstrated by adjusting the composition with the addition of an increasing number of elements.However,such a strategy may negatively impact processing repeatability and composition control.In this work,singleelement-filled skutterudite is engineered to have high thermoelectric and mechanical performances.Increased Yb filling fraction is found to increase phonon scattering,whereas cryogenic grinding contributes additional microstructural scattering.A peak zT of 1.55 and an average zT of about 1.09,which is comparable to the reported results of multiple-filled SKDs,are realized by the combination of simple composition and microstructure engineering.Furthermore,the mechanical properties of Yb single-filled CoSb_(3) skutterudite are improved by manipulation of the microstructure through cryogenic grinding.These findings highlight the realistic prospect of producing high-performance thermoelectric materials with reduced compositional complexity.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
In the aforementioned article,on page 8,the sentence:‘The trend towards compositional complexity…reached its pinnacle with the introduction of HEMGs in 2004[43,44,46].’contains an inaccuracy regarding the timeline....In the aforementioned article,on page 8,the sentence:‘The trend towards compositional complexity…reached its pinnacle with the introduction of HEMGs in 2004[43,44,46].’contains an inaccuracy regarding the timeline.Correction:The sentence should be revised to acknowledge the foundational work published in 2002–2003.展开更多
Transition metal carbides are promising candidates for thermal protection materials due to their high melting points and excellent mechanical properties.However,the relatively high thermal conductivity is still a majo...Transition metal carbides are promising candidates for thermal protection materials due to their high melting points and excellent mechanical properties.However,the relatively high thermal conductivity is still a major obstacle to its application in an ultra-high-temperature insulation system.In this work,the low thermal conductivity of dense(TiZrHfVNbTa)Cx(x=0.6-1)high-entropy carbides has been realized by adjusting the carbon stoichiometry.The thermal conductivity gradually decreases from 10.6 W·m^(−1)·K^(−1) at room temperature to 6.4 W·m^(−1)·K^(−1) with carbon vacancies increasing.Due to enhanced scattering of phonons and electrons by the carbon vacancies,nearly full-dense(97.9%)(TiZrHfVNbTa)C_(0.6) possesses low thermal conductivity of 6.4 W·m^(−1)·K^(−1),thermal diffusivity of 2.3 mm^(2)·s^(−1),as well as electrical resistivity of 165.5μΩ·cm.The thermal conductivity of(TiZrHfVNbTa)C_(0.6) is lower than that of other quaternary and quinary high-entropy carbide ceramics,even if taking the difference of porosity into account in some cases,which is mainly attributed to compositional complexity and carbon vacancies.This provides a promising route to reduce the thermal conductivity of high-entropy carbides by increasing the number of metallic elements and carbon vacancies.展开更多
In this work, new plain and composite high-energy solitons of the cubic–quintic Swift–Hohenberg equation were numerically found. Starting from a composite pulse found by Soto-Crespo and Akhmediev and changing some p...In this work, new plain and composite high-energy solitons of the cubic–quintic Swift–Hohenberg equation were numerically found. Starting from a composite pulse found by Soto-Crespo and Akhmediev and changing some parameter values allowed us to find these high energy pulses. We also found the region in the parameter space in which these solutions exist. Some pulse characteristics, namely, temporal and spectral profiles and chirp, are presented. The study of the pulse energy shows its independence of the dispersion parameter but its dependence on the nonlinear gain. An extreme amplitude pulse has also been found.展开更多
基金funded by the National Natural Science Foundation of China(Grant Nos.52201171 and 52225103)the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-IDRY-23-001)the National Key Research and Development Program of China(Grant No.2022YFB4602101).
文摘Tantalum(Ta)alloys have been widely utilized in rocket,air-breathing engines,and airframe applications.However,traditional Ta alloys suffer from insufficient strength at ultra-high temperature,making it challenging to satisfy the design requirements for next-generation aerospace equipment.We report a novel strategy to design Ta alloys with superior mechanical properties by integrating the multi-principal element concept with compositionally complex carbides.By introducing multiple refractory elements and C,the resultant alloys displayed a thermally stable microstructure consisting of two phases.With the increasing C contents,the microstructure evolved from hypoeutectic to eutectic and then to hypereutectic.These varying microstructural characteristics influenced crack blunting and dislocation accumulation behaviors,leading to different softening resistance at 1600℃and plasticity at room temperature.Benefiting from the strengthening effects of solid solution and compositionally complex carbides,these alloys exhibited a high strength of~600 MPa at 1600℃,significantly superior than that of traditional Ta alloys.
基金financially supported by Guangdong Basic and Applied Basic Research Foundation (No. 2021A1515012626)Shenzhen Knowledge Innovation Plan-Fundamental Research (Discipline Distribution) (No. JCYJ20180507184623297)+1 种基金the National Natural Science Foundation of China (No.52301043)the Postdoctoral Research Startup Expenses of Shenzhen (No.NA25501001)。
文摘This study focuses on compositionally complex alloys(CCAs),aiming to achieve a balance between high strength and low density for new energy and aerospace applications.The composition of AlCrFeNiTi_(x) CCAs is strategically guided by employing density functional theory and the theoretical design of thermodynamic calculations.Bulk CCAs,particularly AlCrFeNiTi_(0.25) alloy,demonstrate remarkable specific yield strength(1640.8 MPa) and 22.7% maximum strain.The incorporation of Ti facilitates the formation of lightweight and high-strength L2_(1)phase,contributing to the overall high specific strength.Synergistic effects of grain boundary strengthening,solid solution strengthening,Orowan strengthening and Peierls flow stress further enhance strength.Detailed exploration of micros tructural changes during fracture reveals the role of ordered phases in suppressing crack propagation and absorbing energy within disordered phases,thereby improving the toughness and fracture resistance of CCAs.These methods and discoveries establish a robust foundation for advancing the development of novel lightweight CCAs.
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W.J.Lu is grateful for financial support from the open research fund of Songshan Lake Materials Laboratory(No.2021SLABFK05)the Shenzhen Science and Technology Program(No.JCYJ20210324104404012).
文摘Here,we study the hydride formation in a metastable Ti-33Zr-22Hf-11Ta(at.%)refractory high entropy alloy(RHEA).Deviating to non-equiatomic compositions of RHEAs promotes the formation of transformation-induced plasticity where the body-centered cubic phase transforms to hexagonal close-packed(HCP)phase.It is found that the phase transformation capability assists the hydride formation due to the low solubility of hydrogen within the HCP phase.In this study,hydrogen is charged via electrochemical polishing and the corresponding phase transformation is activated in the metastable RHEAs.The newly formed HCP phase interacts with hydrogen to form a face-centered cubic hydride verified by electron energy loss spectroscopy.This work provides a primary exploration of the formation of compositionally complex metal hydrides in the metastable RHEAs,which are potential candidates for future hydrogen storage material design.
基金supported by the National Natural Science Foundation of China(Grant No.52231001)Evan Ma and Jun Ding also acknowledge XJTU for hosting their research at the Center for Alloy Innovation and Design(CAID).
文摘1.Introduction Multi-principal element alloys(MPEAs),with compositions in the central region of the multicomponent phase diagram,have been dubbed"high-entropy alloys"(HEAs)in recent years[1-11].A more general term currently accepted by the community for these MPEAs is complex concentrated alloys or compositionally complex alloys(CCAs)[12].These alloys are usually based on single-phase multi-principal element solid solutions,with no need or possibility to distinguish which species constitutes the solvent and which ones are solutes.This Viewpoint and Perspective article focuses on a salient feature in the internal structure of MPEAs,different from traditional metals and solvent-(dilute)solute solutions.Specifically,the unusual trait to be highlighted for these heavily concentrated solutions is their inherent chemical inhomogeneity on the nanoscale,in terms of the high propensity for compositional fluctuation and local chemical order.
基金financially supported by the National Natural Science Foundation of China(Nos.52201171,52225103,U2441262,51921001,and 12335017)the Fundamental Research Funds for the Central Universities,China(No.FRF-IDRY-23-001)+1 种基金National Key Re-search and Development Program of China(No.2022YFB4602101)the China heavy-duty gas turbine technology Co.Ltd under the project of J721.
文摘Advanced structural materials with superb mechanical properties at ultrahigh temperatures are essential for aerospace and power-generation sectors.Refractory multi-principal element alloys(RMPEAs)are promising candidates,but they face challenges such as limited plasticity at room temperatures and insufficient strength at ultrahigh temperatures.In this work,we investigated the mechanical properties and microstructures of RMPEA reinforced with compositional complex carbides and demonstrated that tailoring the carbon content can significantly alter their microstructures and enhance mechanical properties.Specifically,the W_(30)Ta_(30)Mo_(15)Nb_(15)C_(10)alloy achieved an ultrahigh strength of 896 MPa at 1600℃ and a plasticity of∼8%at room temperatures.The strengthening effect arises from multi-principal element mixing and robust dislocation hindering at the phase interfaces between the carbides and the matrix,while the room temperature plasticity is attributed to crack buffering facilitated by the highly saturated solid solution matrix.Our study highlights the potential of compositional complex carbide to enhance the mechanical properties of RMPEAs,offering a promising approach for the development of advanced structural materials for ultrahigh temperature applications.
基金This project is supported by National Natural Science Foundation of China(No.50175031).
文摘Accurate boundary conditions of composite material plates with different holes are founded to settle boundary condition problems of complex holes by conformal mapping method upon the nonhomogeneous anisotropic elastic and complex function theory. And then the two stress functions required were founded on Cauchy integral by boundary conditions. The final stress distributions of opening structure and the analytical solution on composite material plate with rectangle hole and wing manholes were achieved. The influences on hole-edge stress concentration factors are discussed under different loads and fiber direction cases, and then contrast calculates are carried through FEM.
基金supported by the National Natural Science Foundation of China(Nos.51921003,51975292 and 52275153)the Outstanding Youth Foundation of Jiangsu Province of China(No.BK20211519)+2 种基金the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures,China(Nanjing University of Aeronautics and Astronautics,No.MCMS-I-0521K01)the Fund of Prospective Layout of Scientific Research for Nanjing University of Aeronautics and Astronautics,Chinathe Priority Academic Program Development of Jiangsu Higher Education Institutions,China。
文摘During the whole service lifetime of aircraft structures with composite materials,impacts are inevitable and can usually cause severe but barely visible damages.Since the occurrences of impact are random and unpredictable,it is a hotspot direction to develop an online impact monitoring system that can meet strict limitations of aerospace applications including small size,light weight,and low power consumption.Piezoelectric(PZT)sensor,being able to generate impact response signals with no external power and cover a large-scale structure with only a small amount of them,is a promising choice.Meanwhile,for real systems,networks with multiple nodes are normally required to monitor large-scale structures in a global way to identify any impact localization confliction,yet the existing studies are mostly evaluated with single nodes instead of networks.Therefore,in this paper,based on a new low-power node designed,a Bluetooth-based digital impact monitoring PZT sensor network is proposed for the first time with its global confliction-solving impact localization method.Evaluations of the system as a network are researched and analyzed on a complex real aircraft wing box for a global confliction-solving impact localization,showing a satisfying high accuracy.
基金Project supported by the National Natural Science Foundation of China (Nos. 12102043, 12072375U2241240)the Natural Science Foundation of Hunan Province of China (Nos. 2023JJ40698 and 2021JJ40710)。
文摘The accurate and efficient analysis of anisotropic heat conduction problems in complex composites is crucial for structural design and performance evaluation. Traditional numerical methods, such as the finite element method(FEM), often face a trade-off between calculation accuracy and efficiency. In this paper, we propose a quasi-smooth manifold element(QSME) method to address this challenge, and provide the accurate and efficient analysis of two-dimensional(2D) anisotropic heat conduction problems in composites with complex geometry. The QSME approach achieves high calculation precision by a high-order local approximation that ensures the first-order derivative continuity.The results demonstrate that the QSME method is robust and stable, offering both high accuracy and efficiency in the heat conduction analysis. With the same degrees of freedom(DOFs), the QSME method can achieve at least an order of magnitude higher calculation accuracy than the traditional FEM. Additionally, under the same level of calculation error, the QSME method requires 10 times fewer DOFs than the traditional FEM. The versatility of the proposed QSME method extends beyond anisotropic heat conduction problems in complex composites. The proposed QSME method can also be applied to other problems, including fluid flows, mechanical analyses, and other multi-field coupled problems, providing accurate and efficient numerical simulations.
基金supported by the National Science Foundation(NSF)Materials Research Science and Engineering Center(MRSEC)program through the UC Irvine Center for Complex and Active Materials(CCAM)under No.DMR2011967This work used shared facilities at the Irvine Materials Research Institute(also supported in part by the NSF DMR2011967)+3 种基金the San Diego Nanotechnology Infrastructure(SDNI)of UCSD,a member of the National Nanotechnology Coordinated Infrastructure(NSF ECCS-2025752)the NSF Center for Chemistry at the Space–Time Limit(CHE-0802913)the UC San Diego MRSEC shared instrumentation(NSF Grant DMR2011924)the UC San Diego Nanoengineering Materials Research Center(NE-MRC).
文摘Compositionally complex solid electrolyte(Li_(0.375)Sr_(0.4375))(Ta_(0.375)Nb_(0.375)Zr_(0.125)Hf_(0.125))O_(3)(LSTNZH)samples are synthesized using different sintering temperatures,durations,and cooling conditions(furnace cooling(FC)vs.air quenching(AQ)).The temperature-dependent grain growth has been examined to investigate the microstructural evolution and the origin of exaggerated(abnormal)grain growth.At moderate temperatures,the grain growth of LSTNZH follows a cubic root growth model with an Arrhenius temperature dependence.With increasing temperature,bimodal microstructures develop,and the Arrhenius temperature dependence breaks down.Notably,increasing the temperature induces increased Nb segregation at general grain boundaries(GBs),in contrast to classical GB segregation models but suggesting premelting-like GB disordering,which can explain the observed abnormal grain growth(AGG).In addition,the large grains become faceted with increasing temperature,which occurs concurrently with the temperature-induced transitions in GB segregation and grain growth,thereby further supporting the occurrence of a GB phase-like(complexion)transition.The impacts on the densification,ionic conductivity,and hardness are also examined.This work provides a new insight into the fundamental understanding of the grain growth mechanisms of the emergent class of medium-and high-entropy compositionally complex ceramics(CCCs),which is essential for tailoring microstructures and material properties.
基金funded by Natural Science Foundation of China(Nos.51774096,51871053)Shanghai Committee of Science and Technology(Nos.16JC1401800,18JC1411200)+1 种基金supported by the NASA Science Missions Directorate under the Radioisotope Power Systems Programsupport from the National Science Foundation(DMREF-1333335 and DMREF-1729487).
文摘A broad tunability of the thermoelectric and mechanical properties of CoSb_(3) has been demonstrated by adjusting the composition with the addition of an increasing number of elements.However,such a strategy may negatively impact processing repeatability and composition control.In this work,singleelement-filled skutterudite is engineered to have high thermoelectric and mechanical performances.Increased Yb filling fraction is found to increase phonon scattering,whereas cryogenic grinding contributes additional microstructural scattering.A peak zT of 1.55 and an average zT of about 1.09,which is comparable to the reported results of multiple-filled SKDs,are realized by the combination of simple composition and microstructure engineering.Furthermore,the mechanical properties of Yb single-filled CoSb_(3) skutterudite are improved by manipulation of the microstructure through cryogenic grinding.These findings highlight the realistic prospect of producing high-performance thermoelectric materials with reduced compositional complexity.
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In the aforementioned article,on page 8,the sentence:‘The trend towards compositional complexity…reached its pinnacle with the introduction of HEMGs in 2004[43,44,46].’contains an inaccuracy regarding the timeline.Correction:The sentence should be revised to acknowledge the foundational work published in 2002–2003.
基金supported by the National Natural Science Foundation of China (Nos.52032002 and 51972081)National Safety Academic Foundation (No.U2130103)Science and Technology on Particle Transport and Separation Laboratory,and Heilongjiang Touyan Team Program.
文摘Transition metal carbides are promising candidates for thermal protection materials due to their high melting points and excellent mechanical properties.However,the relatively high thermal conductivity is still a major obstacle to its application in an ultra-high-temperature insulation system.In this work,the low thermal conductivity of dense(TiZrHfVNbTa)Cx(x=0.6-1)high-entropy carbides has been realized by adjusting the carbon stoichiometry.The thermal conductivity gradually decreases from 10.6 W·m^(−1)·K^(−1) at room temperature to 6.4 W·m^(−1)·K^(−1) with carbon vacancies increasing.Due to enhanced scattering of phonons and electrons by the carbon vacancies,nearly full-dense(97.9%)(TiZrHfVNbTa)C_(0.6) possesses low thermal conductivity of 6.4 W·m^(−1)·K^(−1),thermal diffusivity of 2.3 mm^(2)·s^(−1),as well as electrical resistivity of 165.5μΩ·cm.The thermal conductivity of(TiZrHfVNbTa)C_(0.6) is lower than that of other quaternary and quinary high-entropy carbide ceramics,even if taking the difference of porosity into account in some cases,which is mainly attributed to compositional complexity and carbon vacancies.This provides a promising route to reduce the thermal conductivity of high-entropy carbides by increasing the number of metallic elements and carbon vacancies.
基金FCT(Fundacao para a Ciência e Tecnologia)for supporting this work through the Project UID/CTM/50025/2013
文摘In this work, new plain and composite high-energy solitons of the cubic–quintic Swift–Hohenberg equation were numerically found. Starting from a composite pulse found by Soto-Crespo and Akhmediev and changing some parameter values allowed us to find these high energy pulses. We also found the region in the parameter space in which these solutions exist. Some pulse characteristics, namely, temporal and spectral profiles and chirp, are presented. The study of the pulse energy shows its independence of the dispersion parameter but its dependence on the nonlinear gain. An extreme amplitude pulse has also been found.
