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
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
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.
