In this paper,a comprehensive understanding of stable and metastable phase equilibria in binary Mg-Gd system was conducted with an aid of the CALculation of PHAse Diagram(CALPHAD)modeling.Firstly,thermodynamic descrip...In this paper,a comprehensive understanding of stable and metastable phase equilibria in binary Mg-Gd system was conducted with an aid of the CALculation of PHAse Diagram(CALPHAD)modeling.Firstly,thermodynamic descriptions of all the stable phases in the Mg-Gd system were re-assessed by considering all the experimental data in the literature.The discrepancy between the phase equilibria and thermochemical properties existing in the previous assessments was eliminated,and the better agreement with the experimental data was achieved in the present assessment.Secondly,the Gibbs energies for metastable β"-Mg3Gd and β"-Mg7Gd were constructed based on the first-principles and CALPHAD computed results as well as their correlation,and then incorporated into the CALPHAD descriptions.The model-predicted solvuses of(Mg)in equilibrium with the metastable β"-Mg7Gd and β'-Mg7Gd compounds showed very good agreement with the limited experimental data.Finally,the presently obtained thermodynamic descriptions of both stable and metastable phases in the binary Mg-Gd system were further validated by realizing the quantitative Scheil-Gulliver solidification simulations of 5 as-cast Mg-Gd alloys,and the successful prediction of the precipitation sequences in Mg-15Gd and Mg-12Gd alloys during the aging process.展开更多
The non-equilibrium microstructure and a new metastable phase of Al-9.6wt%Mg alloy solidified at 6 GPa were studied by optical microscope,differential scanning calorimetry,X-ray diffraction and transmission electron m...The non-equilibrium microstructure and a new metastable phase of Al-9.6wt%Mg alloy solidified at 6 GPa were studied by optical microscope,differential scanning calorimetry,X-ray diffraction and transmission electron microscope.The results showed that dendrite microstructure was refined,and the solid solubility of Mg in α-Al phase increased greatly.Correspondingly,the lattice parameter of α-Al phase increased.Al3Mg2 phases disappeared under high pressure solidification.In particular,a metastable phase with small size(20 nm or so) was produced in the alloy,its melting temperature range was 464~518.2 ℃,which was higher than that of Al3Mg2 phase(453~465 ℃) under normal pressure.These metastable phases located in the interdendritic position.It was the first time that the metastable phase was found in Al-Mg alloy at a high pressure of 6 GPa.The formation mechanism of the metastable phases was discussed.展开更多
The metastable liquid phase separation and rapid solidification behaviors of Co_(40) Fe_(40) Cu_(20) alloy were investigated by using differential thermal analysis(DTA) in combination with glass fluxing and el...The metastable liquid phase separation and rapid solidification behaviors of Co_(40) Fe_(40) Cu_(20) alloy were investigated by using differential thermal analysis(DTA) in combination with glass fluxing and electromagnetic levitation(EML) techniques. The critical liquid phase separation undercooling for this alloy was determined by DTA to be 174 K. Macrosegregation morphologies are formed in the bulk samples processed by both DTA and EML. It is revealed that undercooling level, cooling rate, convection, and surface tension difference between the two separated phases play a dominant role in the coalescence and segregation of the separated phases. The growth velocity of the(Fe,Co) dendrite has been measured as a function of undercooling up to 275 K. The temperature rise resulting from recalescence increases linearly with the increase of undercooling because of the enhancement of recalescence. The slope change of the recalescence temperature rise versus undercooling at the critical undercooling also implies the occurrence of liquid demixing.展开更多
The radiation of material surface by high intensity laser beams is used to produce the uhrafine powder of pure Fe and ZrO_2.The morphology,size and phases of the powder were examined by X-ray diffraetometer,scanning e...The radiation of material surface by high intensity laser beams is used to produce the uhrafine powder of pure Fe and ZrO_2.The morphology,size and phases of the powder were examined by X-ray diffraetometer,scanning electron microscopy as well as transmission electron microscopy.In pure Fe a considerable quantity of γ-phase was found in the powder.In ZrO_2 powder,instead of stable phase,two metastable phases appeared.展开更多
Variable-composition evolutionary structure searches are used to explore stable stoichiometries for the Zn-O system below 300 GPa. Our results confirm the previous structural phase transition sequence of pressurised Z...Variable-composition evolutionary structure searches are used to explore stable stoichiometries for the Zn-O system below 300 GPa. Our results confirm the previous structural phase transition sequence of pressurised ZnO. ZnO is thermodynamically stable up to 300GPa and zinc peroxide (Zn02, space group Pa3) is metastable under lower pressure. Insulating I4/mcm-Zn02 is thermodynamically stable between 128.3-300 GPa. Insulated metastable P3121-Zn02, controlling the pressure range of 51.5-128.3 GPa, has a wide band gap compared to the Pa3-Zn02 and I4/mem-Zn02. Phonon and elastic constant calculations conclude the dynamical and mechanical stability for the explored thermodynamically stable or metastable structures.展开更多
The powder mixture of Al, Ti and graphite has been mechanically alloyed in a planetary ball mill.The structural evolution of as-milled powder sample has been characterized by XRD, DTA. The results show that the amorph...The powder mixture of Al, Ti and graphite has been mechanically alloyed in a planetary ball mill.The structural evolution of as-milled powder sample has been characterized by XRD, DTA. The results show that the amorphous phase is formed first at an early milling stage, then crystallization occurs during further milling, leading to formation of a nanocrystalline fcc metastable phase. In contrast, during annealing the amorphous phase is crystallized to the equilibrium phase instead of the fcc phase. This indicates that crystallization during ball milling is different from that induced by annealing展开更多
The splat foils of Al-Sm alloys with 0.04-0.06mm in thickness were made by hammeranvil technique. The estimated cooling rute was 106K/ order of magnitude. The extended solid solubility of Sm in α-Al reached 0.5at. % ...The splat foils of Al-Sm alloys with 0.04-0.06mm in thickness were made by hammeranvil technique. The estimated cooling rute was 106K/ order of magnitude. The extended solid solubility of Sm in α-Al reached 0.5at. % Sm. The intermediate phase in the rapidlysolidified Al-Sm alloys is Al11Sm3 phase, which is stable only at temperatures above 1339K in equilibrium state and retained to ambient temperature as a metastable phase, whereas the equlibrium intermediate phase, Al3Sm, was restricted to occur.展开更多
1 Introduction The Pingluoba brine,which characterized as high concentration with sodium,potassium,boron,lithium,and rubidium,possess great development value.The main composition of the brine can be summarized to the
A time-resolved x-ray diffraction technique is employed to monitor the structural transformation of laser-shocked bismuth.Results reveal a retarded transformation from the shock-induced Bi-Ⅴphase to a metastable Bi-...A time-resolved x-ray diffraction technique is employed to monitor the structural transformation of laser-shocked bismuth.Results reveal a retarded transformation from the shock-induced Bi-Ⅴphase to a metastable Bi-Ⅳphase during the shock release,instead of the thermodynamically stable Bi-Ⅲphase.The emergence of the metastable Bi-Ⅳphase is understood by the competitive interplay between two transformation pathways towards the Bi-Ⅳand Bi-Ⅲ,respectively.The former is more rapid than the latter because the Bi-Ⅴto B-Ⅳtransformation is driven by interaction between the closest atoms while the Bi-Ⅴto B-Ⅲtransformation requires interaction between the second-closest atoms.The nucleation time for the Bi-Ⅴto Bi-Ⅳtransformation is determined to be 5.1±0.9 ns according to a classical nucleation model.This observation demonstrates the importance of the formation of the transient metastable phases,which can change the phase transformation pathway in a dynamic process.展开更多
Metastable nanostructured electrocatalyst with a completely different surface environment compared to conventional phase-based electrocatalyst often shows distinctive catalytic property.Although Ru-based electrocataly...Metastable nanostructured electrocatalyst with a completely different surface environment compared to conventional phase-based electrocatalyst often shows distinctive catalytic property.Although Ru-based electrocatalysts have been widely investigated toward hydrogen oxidation reaction(HOR)under alkaline electrolytes,these studies are mostly limited to conventional hexagonal-close-packed(hcp)phase,mainly arising from the lack of sufficient synthesis strategies.In this study,we report the precise synthesis of metastable binary RuW alloy with face-centered-cubic(fcc)phase.We find that the introduction of W can serve as fcc phase seeds and reduce the formation energy of metastable fcc-RuW alloy.Impressively,fcc-RuW exhibits remarkable alkaline HOR performance and stability with the activity of 0.67 mA cm_(Ru)^(-2)which is almost five and three times higher than that of hcp-Ru and commercial Pt/C,respectively,which is attributed to the optimized binding strength of adsorbed hydroxide intermediate derived from tailored electronic structure through W doping and phase engineering.Moreover,this strategy can also be applied to synthesize other metastable fcc-RuCr and fcc-RuMo alloys with enhanced HOR performances.展开更多
The metastable phase equilibria of the Li+, Mg2+//SO42-, borate-H2O system at 273.15 K were studied using isothermal evaporation method. The dry-salt phase diagram, water-phase diagram and the physicochemical proper...The metastable phase equilibria of the Li+, Mg2+//SO42-, borate-H2O system at 273.15 K were studied using isothermal evaporation method. The dry-salt phase diagram, water-phase diagram and the physicochemical property diagrams of the system were plotted with the metastable solubility values and physicochemical properties corresponding to density, refractive index, pH value and conductivity. The dry-salt diagram was composed of four crys- tallizing zones[lithium sulfate hydrate(Li2SO4·H2O), epsomite(MgSO4·7H2O), lithium metaborate octahy- drate(LiBO2.8H2O), and hungchaoite(MgB4O7·9H2O)], five univariant curves and two invariant points (Li2SO4·H2O+MgSO4·7H2O+MgB4O7·9H2O and Li2SO4·H2O+LiBO2-8H2O+MgB4O7·9H20). Li2B4O7 converted in- to LiBO2 in solution. Comparing the metastable phase diagram at 273.15 K and stable phase diagram at 298.15 K for the system, the crystallized area of Li2SO4·H2O and MgSO4·7H2O became large, whereas, the other phase regions became small. The J(H2O) changes regularly with increasing J(SO42-), and the physicochemical properties change regularly with the concentration of B4O72- increasing.展开更多
The component solubilities, densities and refractive indices of the quaternary system Na^+, Rb^+, Mg^+//Cl^--H2O at 298.2 K were measured using an isothermal evaporation method. Based on the gathered data, a metast...The component solubilities, densities and refractive indices of the quaternary system Na^+, Rb^+, Mg^+//Cl^--H2O at 298.2 K were measured using an isothermal evaporation method. Based on the gathered data, a metastable phase diagram, a water content diagram, and a density/refractive index vs. composition diagram were constructed. The results show that this system is of a complex type with a double salt rubidium carnallite (RbCl·MgCl2·6H2O) formed at 298.2 K. Double salt rubidium carnallite, whose component point locates in its own crystallization zone in the dry salt phase diagram, belongs to congruent double salt at 298.2 K. Accompanied by the double salt that was formed, there are two invariant points in the phase diagram that cosaturated with three salts and an equilibrated solution. The cosaturated salts for the two invariant points are MgCl26H2O+RbCl·MgCl2·6H2O+ NaCl and Na^+, Rb^+, Mg^+//Cl^--H2O, respectively. Both invariant points are commensurate invariant points in the evaporation process, and the two invariant points are evaporative dry points. The sizes of the crystalline regions of the salts are in the order of NaCl〉RbCl〉RbCl·MgCl2·6H2O〉MgCl2·6H2O.展开更多
Aberration-corrected scanning transmission electron microscopy has been used to study a novel metastable phase,designated asβ’’phase,induced to form by electron beam irradiation in a Mg-9.8 wt.%Sn alloy.This phase ...Aberration-corrected scanning transmission electron microscopy has been used to study a novel metastable phase,designated asβ’’phase,induced to form by electron beam irradiation in a Mg-9.8 wt.%Sn alloy.This phase is spherical in three dimensions,having a D019 structure with the lattice parameters of a=0.642 nm,c=0.521 nm and space group of P63/mmc.Its chemical formula is Mg_(3)Sn,like theβ’metastable precipitate phase.The orientation relationship between theβ’’phase and theα-Mg matrix is such that■_(β)’’//■_(α)and(0001)_(β)’’//(0001)_(α).Its formation involves solely the ordering of Sn atoms in the solid solution magnesium matrix.First-principles calculations indicate that the formation of theβ’’phase is energetically favored.展开更多
The solubilities and densities of the aqueous metastable ternary systems(NaCl-MgCl_(2)-H_(2)O)and(KCl-MgCl_(2)-H_(2)O)at 308.15 K were determined by the isothermal evaporation method.On the basis of the experimental r...The solubilities and densities of the aqueous metastable ternary systems(NaCl-MgCl_(2)-H_(2)O)and(KCl-MgCl_(2)-H_(2)O)at 308.15 K were determined by the isothermal evaporation method.On the basis of the experimental results,the phase diagrams for those systems were plotted.It was found that the former system belongs to the hydrate-I type with one invariant point of(NaCl+MgCl_(2)·6H_(2)O),two univariant curves,and two crystal-lization regions corresponding to halite(NaCl)and bischofite(MgCl_(2)·6H_(2)O);and the latter system belongs to the type of incongruent-double salts with two invariant points of(KCl+KCl·MgCl_(2)·6H_(2)O)and(MgCl_(2)·6H_(2)O+KCl·MgCl_(2)·6H_(2)O),three univariant curves,and three crystallization regions corresponding to potassium chlor-ide(KCl),carnallite(KCl·MgCl_(2)·6H_(2)O)and bischofite(MgCl_(2)·6H_(2).No solid solutions were found in both systems.展开更多
Pattern recognition and neural network methods have been used to investigate the formability of metastable alloy phases, It has been found that some chemi cal bond parameters Such as valence electron number, electrone...Pattern recognition and neural network methods have been used to investigate the formability of metastable alloy phases, It has been found that some chemi cal bond parameters Such as valence electron number, electronegativity and metallic radii of cor-nponent elements are the dominating fac tors affecting metastable alloy phase formation. Some semi-empirical rules found in this way may be useful for the construction of expert system for materials design.展开更多
A general approach is reported for ultra-fast phosphating synthesis of a series of ultra-small(<5 nm)noble metal phosphides(MPX/CNT,M=Pd,Pt,Ru)which are successfully produced in just 75 s for the first time.The cat...A general approach is reported for ultra-fast phosphating synthesis of a series of ultra-small(<5 nm)noble metal phosphides(MPX/CNT,M=Pd,Pt,Ru)which are successfully produced in just 75 s for the first time.The catalytic performance of the catalysts can be optimized by controlling the nanomaterials as the metastable crystalline phases.By altering the phosphorus source under the same conditions,the hexagonal structured Pd_(7)P_(3)(NaH_(2)PO_(2).H_(2)O as P source)and monoclinic structured Pd_(6)P(Na_(4)P_(2)O_(7) as P source)can be prepared successfully.Both of them exhibit excellent polyol oxidation performance in alkaline media.Monoclinic Pd_(6)P/CNT and hexagonal Pd_(7)P_(3)/CNT have large ECSA which are confirmed as 82.1 m2 g^(-1)and 86.2 m2 g^(-1),respectively.Hexagonal Pd_(7)P_(3)/CNT has the highest mass activity of 6.14 A mgPd^(-1)(3.21 A mgPd^(-1)for Pd_(6)P/CNT)for GOR,which far exceeded Pt/C(2.81 A mgPt^(-1)).Meanwhile,the mass activity of monoclinic Pt_(5)P_(2)/CNT for EGOR achieved 12.4 A mg_(Pt)^(-1),which far exceeded Pt/C(6.8 A mg_(Pt)^(-1)).The stability test proved that the activity decay of these catalysts was negligible after the 12-hour durability test.Meanwhile,they have excellent CO anti-poisoning abilities.展开更多
Nb/Nb5Si3 in-situ composites are very attractive structural materials because these materials perform a good balance in mechanical properties, including high strength at high temperature (> 1000 degrees C) and reas...Nb/Nb5Si3 in-situ composites are very attractive structural materials because these materials perform a good balance in mechanical properties, including high strength at high temperature (> 1000 degrees C) and reasonably high fracture toughness at room temperature. Metastable phase Nb3Si plays an important role in the properties of Nb/Nb5Si3 composites by affecting the volume fraction of ductile phase. The addition of Mo affects on the microstructure of ductile phase and the stability of metastable phase Nb3Si. In this paper, Nb-10Si-xMo and Nb-18Si-xMo (x = 0, 5, and 15) alloys were prepared by arc melting and annealed at 1473 K for 100 h. Single edge-notched bending (SENB) test was used to study the fracture toughness of Nb-Si-Mo alloys. The room temperature fracture toughness of Nb-10Si is 10.48 MPa center dot m(1/2) and higher than that of binary Nb-18Si alloys at near-eutectic composites. The addition of 5 at.% Mo improved the fracture toughness of as-cast Nb-Si alloys from 4.1 MPa center dot m(1/2) to 9.99 MPa center dot m(1/2) at near-eutectic compositions and reduced it from 10.48 MPa center dot m(1/2) to 8.86 MPa center dot m(1/2) at hypoeutectic compositions.展开更多
The nature of the oxygen contained in β-W was investigated with DSC,X-ray analysis on quenched samples and Auger spectroscope.It was shown that the oxygen contained in nonpyrophoric β-W consists of the reversibly ch...The nature of the oxygen contained in β-W was investigated with DSC,X-ray analysis on quenched samples and Auger spectroscope.It was shown that the oxygen contained in nonpyrophoric β-W consists of the reversibly chemisorbed oxygen and the interstitial oxygen which could form an interstitial solid solution with β-W.It seems better to consider β-W to be a metastable phase of tungsten with the interstitial oxygen as stabilizer.展开更多
The metastable phase equilibria of the quaternary system NaCl+Na2CO3+Na2SO4+H2O were studied at 273.15 K. The salts' solubilities, densities and pH values of the equilibrated solution in this system were determine...The metastable phase equilibria of the quaternary system NaCl+Na2CO3+Na2SO4+H2O were studied at 273.15 K. The salts' solubilities, densities and pH values of the equilibrated solution in this system were determined. According to the experimental data, the metastable equilibrium phase diagram, the diagram of density vs. composition and pH vs. composition diagram were plotted. The phase diagram consists of five univariant curves, four crystallization fields and two invariant points. The four crystallization fields correspond to sodium carbonate decahydrate (Na2CO3·10H2O), sodium sulfate decahydrate(Na2SOn-10H2O), sodium chloride(NaCl) and burkeite(2Na2SO4. Na2CO3), respectively. The crystallization field of sodium sulfate decahydrate(Na2SO4.10H2O) is the largest, which indicates that sodium sulfate is easy to saturate and crystallize from solution at 273.15 K.展开更多
1 Introduction Salt lakes are widely distributed in the world,and salt lakes in China are mainly located in the area of the Qinghai-Xizang(Tibet),and the Autonomous Regions of Xinjiang and Inner Mongolia.There are mor...1 Introduction Salt lakes are widely distributed in the world,and salt lakes in China are mainly located in the area of the Qinghai-Xizang(Tibet),and the Autonomous Regions of Xinjiang and Inner Mongolia.There are more than 700salt lakes,each with an area larger than 1 km2,in the展开更多
基金The financial support from the National Key Research and Development Program of China(Grant no.2016YFB0301101)the Hunan Provincial Science and Technology Program of China(Grant no.2017RS3002)-Huxiang Youth Talent Plan+2 种基金the Youth Talent Project of Innovation-driven Plan at Central South University(Grant no.2019XZ027)the Hebei Provincial Science and Technology Program of China(Grant no.BJ2018026)-Outstanding Young Talents Plan is acknowledgedYing Tang acknowledges the financial support from the Yuanguang fellowship released by Hebei University of Technology.
文摘In this paper,a comprehensive understanding of stable and metastable phase equilibria in binary Mg-Gd system was conducted with an aid of the CALculation of PHAse Diagram(CALPHAD)modeling.Firstly,thermodynamic descriptions of all the stable phases in the Mg-Gd system were re-assessed by considering all the experimental data in the literature.The discrepancy between the phase equilibria and thermochemical properties existing in the previous assessments was eliminated,and the better agreement with the experimental data was achieved in the present assessment.Secondly,the Gibbs energies for metastable β"-Mg3Gd and β"-Mg7Gd were constructed based on the first-principles and CALPHAD computed results as well as their correlation,and then incorporated into the CALPHAD descriptions.The model-predicted solvuses of(Mg)in equilibrium with the metastable β"-Mg7Gd and β'-Mg7Gd compounds showed very good agreement with the limited experimental data.Finally,the presently obtained thermodynamic descriptions of both stable and metastable phases in the binary Mg-Gd system were further validated by realizing the quantitative Scheil-Gulliver solidification simulations of 5 as-cast Mg-Gd alloys,and the successful prediction of the precipitation sequences in Mg-15Gd and Mg-12Gd alloys during the aging process.
基金This work is financially supported by the Science Foundation of Harbin Institute of Technology ( No HIT2002 29)
文摘The non-equilibrium microstructure and a new metastable phase of Al-9.6wt%Mg alloy solidified at 6 GPa were studied by optical microscope,differential scanning calorimetry,X-ray diffraction and transmission electron microscope.The results showed that dendrite microstructure was refined,and the solid solubility of Mg in α-Al phase increased greatly.Correspondingly,the lattice parameter of α-Al phase increased.Al3Mg2 phases disappeared under high pressure solidification.In particular,a metastable phase with small size(20 nm or so) was produced in the alloy,its melting temperature range was 464~518.2 ℃,which was higher than that of Al3Mg2 phase(453~465 ℃) under normal pressure.These metastable phases located in the interdendritic position.It was the first time that the metastable phase was found in Al-Mg alloy at a high pressure of 6 GPa.The formation mechanism of the metastable phases was discussed.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB1100101)the National Natural Science Foundation of China(Grant No.51471135)+2 种基金Shenzhen Science and Technology Program,China(Grant No.JCYJ20170815162201821)Shaanxi Provincial Key R&D Program,China(Grant No.2017KW-ZD-07)the Fundamental Research Funds for the Central Universities,China(Grant No.31020170QD102)
文摘The metastable liquid phase separation and rapid solidification behaviors of Co_(40) Fe_(40) Cu_(20) alloy were investigated by using differential thermal analysis(DTA) in combination with glass fluxing and electromagnetic levitation(EML) techniques. The critical liquid phase separation undercooling for this alloy was determined by DTA to be 174 K. Macrosegregation morphologies are formed in the bulk samples processed by both DTA and EML. It is revealed that undercooling level, cooling rate, convection, and surface tension difference between the two separated phases play a dominant role in the coalescence and segregation of the separated phases. The growth velocity of the(Fe,Co) dendrite has been measured as a function of undercooling up to 275 K. The temperature rise resulting from recalescence increases linearly with the increase of undercooling because of the enhancement of recalescence. The slope change of the recalescence temperature rise versus undercooling at the critical undercooling also implies the occurrence of liquid demixing.
文摘The radiation of material surface by high intensity laser beams is used to produce the uhrafine powder of pure Fe and ZrO_2.The morphology,size and phases of the powder were examined by X-ray diffraetometer,scanning electron microscopy as well as transmission electron microscopy.In pure Fe a considerable quantity of γ-phase was found in the powder.In ZrO_2 powder,instead of stable phase,two metastable phases appeared.
基金Supported by the National Natural Science Foundation of China under Grant No 11347007the Qing Lan Project+1 种基金the Colleges and Universities in Jiangsu Province Natural Science Research Project under Grant No 14KJB460013the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Variable-composition evolutionary structure searches are used to explore stable stoichiometries for the Zn-O system below 300 GPa. Our results confirm the previous structural phase transition sequence of pressurised ZnO. ZnO is thermodynamically stable up to 300GPa and zinc peroxide (Zn02, space group Pa3) is metastable under lower pressure. Insulating I4/mcm-Zn02 is thermodynamically stable between 128.3-300 GPa. Insulated metastable P3121-Zn02, controlling the pressure range of 51.5-128.3 GPa, has a wide band gap compared to the Pa3-Zn02 and I4/mem-Zn02. Phonon and elastic constant calculations conclude the dynamical and mechanical stability for the explored thermodynamically stable or metastable structures.
文摘The powder mixture of Al, Ti and graphite has been mechanically alloyed in a planetary ball mill.The structural evolution of as-milled powder sample has been characterized by XRD, DTA. The results show that the amorphous phase is formed first at an early milling stage, then crystallization occurs during further milling, leading to formation of a nanocrystalline fcc metastable phase. In contrast, during annealing the amorphous phase is crystallized to the equilibrium phase instead of the fcc phase. This indicates that crystallization during ball milling is different from that induced by annealing
文摘The splat foils of Al-Sm alloys with 0.04-0.06mm in thickness were made by hammeranvil technique. The estimated cooling rute was 106K/ order of magnitude. The extended solid solubility of Sm in α-Al reached 0.5at. % Sm. The intermediate phase in the rapidlysolidified Al-Sm alloys is Al11Sm3 phase, which is stable only at temperatures above 1339K in equilibrium state and retained to ambient temperature as a metastable phase, whereas the equlibrium intermediate phase, Al3Sm, was restricted to occur.
基金Project supported by National High Technology Research and Development Program of China (2012AA061704)China National Nature Science Foundation (No. 41173071)+2 种基金the Research Fund for the Doctoral Program of Higher Education from the Ministry of Education of China (20115122110001)the Sichuan Youth Science and Technology Innovation Research Team Funding Scheme (2013TD0005)Innovation Team of CDUT(KYTD201405)
文摘1 Introduction The Pingluoba brine,which characterized as high concentration with sodium,potassium,boron,lithium,and rubidium,possess great development value.The main composition of the brine can be summarized to the
基金supported by the National Natural Science Foundation of China (Grant No.12072331)the Science Challenge Project (Grant No.TZ2018001)+2 种基金the Japan Society for the Promotion of Science (Grant Nos.17H04820 and 21H01677)the Foundation of the United Laboratory of High-Pressure Physics and Earthquake Scienceperformed under the approval of the Photon Factory Program Advisory Committee (Proposal Nos.2016S2-006 and 2020G680)。
文摘A time-resolved x-ray diffraction technique is employed to monitor the structural transformation of laser-shocked bismuth.Results reveal a retarded transformation from the shock-induced Bi-Ⅴphase to a metastable Bi-Ⅳphase during the shock release,instead of the thermodynamically stable Bi-Ⅲphase.The emergence of the metastable Bi-Ⅳphase is understood by the competitive interplay between two transformation pathways towards the Bi-Ⅳand Bi-Ⅲ,respectively.The former is more rapid than the latter because the Bi-Ⅴto B-Ⅳtransformation is driven by interaction between the closest atoms while the Bi-Ⅴto B-Ⅲtransformation requires interaction between the second-closest atoms.The nucleation time for the Bi-Ⅴto Bi-Ⅳtransformation is determined to be 5.1±0.9 ns according to a classical nucleation model.This observation demonstrates the importance of the formation of the transient metastable phases,which can change the phase transformation pathway in a dynamic process.
基金the support from the National Natural Science Foundation of China(22272121,21972107)the National Key Research and Development program of China(2021YFB4001200)。
文摘Metastable nanostructured electrocatalyst with a completely different surface environment compared to conventional phase-based electrocatalyst often shows distinctive catalytic property.Although Ru-based electrocatalysts have been widely investigated toward hydrogen oxidation reaction(HOR)under alkaline electrolytes,these studies are mostly limited to conventional hexagonal-close-packed(hcp)phase,mainly arising from the lack of sufficient synthesis strategies.In this study,we report the precise synthesis of metastable binary RuW alloy with face-centered-cubic(fcc)phase.We find that the introduction of W can serve as fcc phase seeds and reduce the formation energy of metastable fcc-RuW alloy.Impressively,fcc-RuW exhibits remarkable alkaline HOR performance and stability with the activity of 0.67 mA cm_(Ru)^(-2)which is almost five and three times higher than that of hcp-Ru and commercial Pt/C,respectively,which is attributed to the optimized binding strength of adsorbed hydroxide intermediate derived from tailored electronic structure through W doping and phase engineering.Moreover,this strategy can also be applied to synthesize other metastable fcc-RuCr and fcc-RuMo alloys with enhanced HOR performances.
文摘The metastable phase equilibria of the Li+, Mg2+//SO42-, borate-H2O system at 273.15 K were studied using isothermal evaporation method. The dry-salt phase diagram, water-phase diagram and the physicochemical property diagrams of the system were plotted with the metastable solubility values and physicochemical properties corresponding to density, refractive index, pH value and conductivity. The dry-salt diagram was composed of four crys- tallizing zones[lithium sulfate hydrate(Li2SO4·H2O), epsomite(MgSO4·7H2O), lithium metaborate octahy- drate(LiBO2.8H2O), and hungchaoite(MgB4O7·9H2O)], five univariant curves and two invariant points (Li2SO4·H2O+MgSO4·7H2O+MgB4O7·9H2O and Li2SO4·H2O+LiBO2-8H2O+MgB4O7·9H20). Li2B4O7 converted in- to LiBO2 in solution. Comparing the metastable phase diagram at 273.15 K and stable phase diagram at 298.15 K for the system, the crystallized area of Li2SO4·H2O and MgSO4·7H2O became large, whereas, the other phase regions became small. The J(H2O) changes regularly with increasing J(SO42-), and the physicochemical properties change regularly with the concentration of B4O72- increasing.
文摘The component solubilities, densities and refractive indices of the quaternary system Na^+, Rb^+, Mg^+//Cl^--H2O at 298.2 K were measured using an isothermal evaporation method. Based on the gathered data, a metastable phase diagram, a water content diagram, and a density/refractive index vs. composition diagram were constructed. The results show that this system is of a complex type with a double salt rubidium carnallite (RbCl·MgCl2·6H2O) formed at 298.2 K. Double salt rubidium carnallite, whose component point locates in its own crystallization zone in the dry salt phase diagram, belongs to congruent double salt at 298.2 K. Accompanied by the double salt that was formed, there are two invariant points in the phase diagram that cosaturated with three salts and an equilibrated solution. The cosaturated salts for the two invariant points are MgCl26H2O+RbCl·MgCl2·6H2O+ NaCl and Na^+, Rb^+, Mg^+//Cl^--H2O, respectively. Both invariant points are commensurate invariant points in the evaporation process, and the two invariant points are evaporative dry points. The sizes of the crystalline regions of the salts are in the order of NaCl〉RbCl〉RbCl·MgCl2·6H2O〉MgCl2·6H2O.
基金financially supported by National Natural Science Foundation of China(51771036 and 51421001)。
文摘Aberration-corrected scanning transmission electron microscopy has been used to study a novel metastable phase,designated asβ’’phase,induced to form by electron beam irradiation in a Mg-9.8 wt.%Sn alloy.This phase is spherical in three dimensions,having a D019 structure with the lattice parameters of a=0.642 nm,c=0.521 nm and space group of P63/mmc.Its chemical formula is Mg_(3)Sn,like theβ’metastable precipitate phase.The orientation relationship between theβ’’phase and theα-Mg matrix is such that■_(β)’’//■_(α)and(0001)_(β)’’//(0001)_(α).Its formation involves solely the ordering of Sn atoms in the solid solution magnesium matrix.First-principles calculations indicate that the formation of theβ’’phase is energetically favored.
基金Financial support from the State Key Program of National Natural Science of China(No.20836009)the National Natural Science Foundation of China(Grant Nos.40573044,40773045)+1 种基金the“A Hundred Talents Program”of the Chinese Academy of Sciences(No.0560051057)the Specialized Research Fund for the Doctoral Program of Chinese Higher Education(No.20060616004)is greatly acknowledged.
文摘The solubilities and densities of the aqueous metastable ternary systems(NaCl-MgCl_(2)-H_(2)O)and(KCl-MgCl_(2)-H_(2)O)at 308.15 K were determined by the isothermal evaporation method.On the basis of the experimental results,the phase diagrams for those systems were plotted.It was found that the former system belongs to the hydrate-I type with one invariant point of(NaCl+MgCl_(2)·6H_(2)O),two univariant curves,and two crystal-lization regions corresponding to halite(NaCl)and bischofite(MgCl_(2)·6H_(2)O);and the latter system belongs to the type of incongruent-double salts with two invariant points of(KCl+KCl·MgCl_(2)·6H_(2)O)and(MgCl_(2)·6H_(2)O+KCl·MgCl_(2)·6H_(2)O),three univariant curves,and three crystallization regions corresponding to potassium chlor-ide(KCl),carnallite(KCl·MgCl_(2)·6H_(2)O)and bischofite(MgCl_(2)·6H_(2).No solid solutions were found in both systems.
文摘Pattern recognition and neural network methods have been used to investigate the formability of metastable alloy phases, It has been found that some chemi cal bond parameters Such as valence electron number, electronegativity and metallic radii of cor-nponent elements are the dominating fac tors affecting metastable alloy phase formation. Some semi-empirical rules found in this way may be useful for the construction of expert system for materials design.
基金supported by the National Natural Science Foundation of China(51772162,22001143,and 52072197)the Youth Innovation and Technology Foundation of Shandong Higher Education Institutions,China(2019KJC004)+4 种基金the Outstanding Youth Foundation of Shandong Province,China(ZR2019JQ14)the Taishan Scholar Young Talent Program(tsqn201909114,tsqn201909123)the Natural Science Foundation of Shandong Province(ZR2020YQ34)the Major Basic Research Program of Natural Science Foundation of Shandong Province under Grant(ZR2020ZD09)the Major Scientific and Technological Innovation Project(2019JZZY020405)。
文摘A general approach is reported for ultra-fast phosphating synthesis of a series of ultra-small(<5 nm)noble metal phosphides(MPX/CNT,M=Pd,Pt,Ru)which are successfully produced in just 75 s for the first time.The catalytic performance of the catalysts can be optimized by controlling the nanomaterials as the metastable crystalline phases.By altering the phosphorus source under the same conditions,the hexagonal structured Pd_(7)P_(3)(NaH_(2)PO_(2).H_(2)O as P source)and monoclinic structured Pd_(6)P(Na_(4)P_(2)O_(7) as P source)can be prepared successfully.Both of them exhibit excellent polyol oxidation performance in alkaline media.Monoclinic Pd_(6)P/CNT and hexagonal Pd_(7)P_(3)/CNT have large ECSA which are confirmed as 82.1 m2 g^(-1)and 86.2 m2 g^(-1),respectively.Hexagonal Pd_(7)P_(3)/CNT has the highest mass activity of 6.14 A mgPd^(-1)(3.21 A mgPd^(-1)for Pd_(6)P/CNT)for GOR,which far exceeded Pt/C(2.81 A mgPt^(-1)).Meanwhile,the mass activity of monoclinic Pt_(5)P_(2)/CNT for EGOR achieved 12.4 A mg_(Pt)^(-1),which far exceeded Pt/C(6.8 A mg_(Pt)^(-1)).The stability test proved that the activity decay of these catalysts was negligible after the 12-hour durability test.Meanwhile,they have excellent CO anti-poisoning abilities.
文摘Nb/Nb5Si3 in-situ composites are very attractive structural materials because these materials perform a good balance in mechanical properties, including high strength at high temperature (> 1000 degrees C) and reasonably high fracture toughness at room temperature. Metastable phase Nb3Si plays an important role in the properties of Nb/Nb5Si3 composites by affecting the volume fraction of ductile phase. The addition of Mo affects on the microstructure of ductile phase and the stability of metastable phase Nb3Si. In this paper, Nb-10Si-xMo and Nb-18Si-xMo (x = 0, 5, and 15) alloys were prepared by arc melting and annealed at 1473 K for 100 h. Single edge-notched bending (SENB) test was used to study the fracture toughness of Nb-Si-Mo alloys. The room temperature fracture toughness of Nb-10Si is 10.48 MPa center dot m(1/2) and higher than that of binary Nb-18Si alloys at near-eutectic composites. The addition of 5 at.% Mo improved the fracture toughness of as-cast Nb-Si alloys from 4.1 MPa center dot m(1/2) to 9.99 MPa center dot m(1/2) at near-eutectic compositions and reduced it from 10.48 MPa center dot m(1/2) to 8.86 MPa center dot m(1/2) at hypoeutectic compositions.
文摘The nature of the oxygen contained in β-W was investigated with DSC,X-ray analysis on quenched samples and Auger spectroscope.It was shown that the oxygen contained in nonpyrophoric β-W consists of the reversibly chemisorbed oxygen and the interstitial oxygen which could form an interstitial solid solution with β-W.It seems better to consider β-W to be a metastable phase of tungsten with the interstitial oxygen as stabilizer.
基金Supported by the National Natural Science Foundation of China(No.40673050)the Research Fund for the Doctoral Program of Higher Education from the Ministry of Education of China(No.20070616008)the Scholarship Leaders Training Fund from Sichuan Province,China(No.2008-140)
文摘The metastable phase equilibria of the quaternary system NaCl+Na2CO3+Na2SO4+H2O were studied at 273.15 K. The salts' solubilities, densities and pH values of the equilibrated solution in this system were determined. According to the experimental data, the metastable equilibrium phase diagram, the diagram of density vs. composition and pH vs. composition diagram were plotted. The phase diagram consists of five univariant curves, four crystallization fields and two invariant points. The four crystallization fields correspond to sodium carbonate decahydrate (Na2CO3·10H2O), sodium sulfate decahydrate(Na2SOn-10H2O), sodium chloride(NaCl) and burkeite(2Na2SO4. Na2CO3), respectively. The crystallization field of sodium sulfate decahydrate(Na2SO4.10H2O) is the largest, which indicates that sodium sulfate is easy to saturate and crystallize from solution at 273.15 K.
基金Financial support from the State Key Program of NNSFC (20836009)the NNSFCs (Grants 21106136, 21276194 and 21306136)
文摘1 Introduction Salt lakes are widely distributed in the world,and salt lakes in China are mainly located in the area of the Qinghai-Xizang(Tibet),and the Autonomous Regions of Xinjiang and Inner Mongolia.There are more than 700salt lakes,each with an area larger than 1 km2,in the