Multifunctional lead-free double perovskites demonstrate remarkable potential towards applications in various fields.Herein,an environmentally-friendly,low-cost,high-throughput Cs_(2)NaFeCl_(6) single crystal with exc...Multifunctional lead-free double perovskites demonstrate remarkable potential towards applications in various fields.Herein,an environmentally-friendly,low-cost,high-throughput Cs_(2)NaFeCl_(6) single crystal with exceedingly high thermal stability is designed and grown.It obtains a cubic lattice system in the temperature range of 80-500 K,accompanied by a completely reversible chromatic variation ranging from yellow to black.Importantly,the intriguing thermochromism is proved to own extremely high reproducibility(over 1000 cycles)without a hysteretic effect,originating from its structural flexibility that including(i)the noteworthy distortion/deformation of[NaCl_(6)]5−and[FeCl_(6)]3−octahedra;(ii)order-disorder arrangement transition of[NaCl_(6)]5−and[FeCl6]3−octahedra as the function of temperature.This study paves the way towards a new class of smart windows and camouflage coatings with an unprecedented colour range based on a Cs_(2)NaFeCl_(6) perovskite.展开更多
The embedded atom method (EAM) was used to study the order-disorder transformation in gamma -TiAl alloy with L1(0). structure at stoichiometrical composition, and the effect of lattice constants was also investigated....The embedded atom method (EAM) was used to study the order-disorder transformation in gamma -TiAl alloy with L1(0). structure at stoichiometrical composition, and the effect of lattice constants was also investigated. It was found that the gamma -TiAl alloy at stoichiometrical composition exhibits a second-order transition, and the relations between lattice constants a, c and the long-range order sigma are not linear. The lattice constant a decreases whereas c increases with the increase of the long-range order parameter. In this case the ordering induces the transformation from cubic to tetragonal. The change of the lattice constant during the ordering processes can be interpreted in terms of bond length.展开更多
To understand and control the interfacial properties of polydiacetylenes(PDAs)vesicles withπ-conjugated backbone is very important for their colorimetric sensing of chemical and biological targets.In this work,we ado...To understand and control the interfacial properties of polydiacetylenes(PDAs)vesicles withπ-conjugated backbone is very important for their colorimetric sensing of chemical and biological targets.In this work,we adopted 10,12-pentacosadiynoic acid(PCDA)as the model molecule to prepare PDAs vesicles in aqueous solution with different forms(from monomer to blue-to-purple-to-red phase)by controlling the UV irradiation dose.The variations of the interfacial conformation of PDAs vesicles during chromatic transitions were inspected by the adsorption behaviors of probe molecules(4-(4-diethylaminostyry)-1-methylpyridinium iodide,D289)on vesicle surface with surface-specific second harmonic generation(SHG)and zeta potential measurements.Resonant SHG signal from D289 adsorbed on vesicle surface attenuated sharply,and the adsorption free energy as well as the corresponding two-photon fluorescence signal decreased slightly in chromatic transitions.While,the change in the surface density of the adsorbed D289 molecules for PDAs vesicles with different forms was relatively small as estimated from zeta potential measurements.The attenuation of the SHG intensity was thus attributed to the overall order-disorder transition and the changed orientation of D289 molecules caused by the gradual distortion of carboxyl head group driven by backbone perturbation.展开更多
The Fe-Pt based intermetallic compounds exhibit good chemical stability and unique magnetic proper-ties,where Ni is an important additional element to optimize the magnetic properties or obtain the outstanding catalyt...The Fe-Pt based intermetallic compounds exhibit good chemical stability and unique magnetic proper-ties,where Ni is an important additional element to optimize the magnetic properties or obtain the outstanding catalytic performances of the Fe-Pt based alloys.Knowledge of how Ni addition affects the order-disorder transitions of the Fe-Pt intermetallics is thus necessary;however,the related information is limited.Therefore,in this work,the phase diagrams of the Fe-Ni-Pt system were experimentally in-vestigated,and as a result,the isothermal sections of the Fe-Ni-Pt system at 600 and 900℃,as well as the vertical sections of Fe_(80)Ni_(20)-Pt_(80)Ni_(20)and Fe_(50)Pt_(50)-Ni_(50)Pt_(50)were constructed.Based on these re-sults,the influences of Ni addition on the crystal stabilities and phase transformations of the ordered Fe-Pt intermetallics have been well described.The results show that the L1_(0)-FePt and L1_(0)-NiPt phases form a ternary continuous solid solution of L1_(0)-(Fe,Ni)Pt,whereas Ni can dissolve in the L1_(2)-Fe_(3)Pt and L1_(2)-FePt_(3)phases as high as 57.0 at.%and 26.0 at.%at 600℃,respectively.The selective occupancy of Ni atoms has been predicted,which should depend on the alloy composition.For both the L1_(0)-(Fe,Ni)Pt and L1_(2)-FePt_(3)phases,when Pt contents are less than their stoichiometric values,Ni atoms will preferentially occupy the Pt sublattice,forming as many nearest-neighbor Fe-Pt bonds as possible.All these results can correlate the alloy compositions,annealing temperatures and crystal structures to both magnetic and catalytic properties,thus providing a basis for optimizing the Fe-Ni-Pt alloys towards enhanced magnetic or catalytic performances.展开更多
Based on cluster variation method (CVM) and natural iteration method (MM),order-disorder phase transition in the intercalation compounds M_(1/2)TiS_2 is simulated bycomputer. The favorable conditions, under which 3^(1...Based on cluster variation method (CVM) and natural iteration method (MM),order-disorder phase transition in the intercalation compounds M_(1/2)TiS_2 is simulated bycomputer. The favorable conditions, under which 3^(1/2)a_0 x a_0 superstructure is formed, aregiven, and the results are in good agreement with the experiments and theoretical calculations. Therelationship between critical temperature and M-ion-vacancy interaction parameter is linear.展开更多
After describing research status of super-structure for Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2,diffraction patterns of Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2 in different order parameters have been researched by Powder-cell pro...After describing research status of super-structure for Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2,diffraction patterns of Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2 in different order parameters have been researched by Powder-cell program,including crystal structure,X-ray and neutron diffraction pattern,anomalous diffraction pattern and comparison of NiCoMn in different positions. The influence of order parameters on intensity of matrix and super-lattice diffraction lines has also been analyzed and the summarization and prospect have been made lastly.展开更多
Based on pair potential, the Bragg Williams (B-W) model is modified to takeinto account the effect of the lattice parameter on theoretical order-disorder transformationanalysis. The main purpose of this work is to und...Based on pair potential, the Bragg Williams (B-W) model is modified to takeinto account the effect of the lattice parameter on theoretical order-disorder transformationanalysis. The main purpose of this work is to understand the basic aspects of this effect andrelated reasonable model on order-disorder transformation. In the present approach, theconfiguration free energy is chosen as function of the lattice parameter and the long-range order.This energy is calculated through Taylor's expansion, starting from the disordered state. It wasfound that the configuration free energy has been strongly modified when the lattice parameter istaken into account. It was also found only one type of order-disorder transformation exists in ABalloy and three kinds of order-disorder transformations for non-equiatomic alloy system such as A_3Balloy. This result is in agreement with experiments.展开更多
The embedded atom method (EAM) was used to theoretically analyze the effect of the lattice parameter variation on the order-disorder transformation in binary alloys. Based on EAM, it is found that only one kind of ord...The embedded atom method (EAM) was used to theoretically analyze the effect of the lattice parameter variation on the order-disorder transformation in binary alloys. Based on EAM, it is found that only one kind of order-disorder transition (second-order transition) exists for AB alloy. Three groups of order-disorder transformation can be observed for the A(3)B or AB(3) compounds. For group I, the order-disorder is a completely first-order transition. For group II, the order-disorder transformation is a classical first-order transition. For group III, the order-disorder transformation is found to be a second-order transition. The lattice parameter variations have a significant effect on E-2 coefficient, which is related to the ordering energy. These results are in good agreement with experiments.展开更多
The order–disorder transition(ODT)of A_(2)B_(2)O_(7)compounds obtained enormous attention owing to the potential application for thermal barrier coating(TBC)design.In this work,the influence of ODT on the mechanical ...The order–disorder transition(ODT)of A_(2)B_(2)O_(7)compounds obtained enormous attention owing to the potential application for thermal barrier coating(TBC)design.In this work,the influence of ODT on the mechanical and thermophysical properties of dual-phase A_(2)B_(2)O_(7)high-entropy ceramics was investigated by substituting Ce^(4+)and Hf^(4+)with different ionic radii on B-sites(Zr^(4+)).The X-ray diffraction(XRD),Raman,and transmission electron microscopy(TEM)results show that rA3+/rB^(4+)=1.47 is the critical value of ODT phase boundary with different doping B-site ion contents,and the energy dispersive spectroscopy(EDS)results further indicate the uniform distribution of elements.Interestingly,owing to the high intrinsic disorder derived from high-entropy effect,the A_(2)B_(2)O_(7)high-entropy ceramics exhibit unreduced modulus(E0≈230 GPa)and enhanced mechanical properties(HV≈10 GPa,KIC≈2.3 MPa·m^(0.5)).A_(2)B_(2)O_(7)high-entropy ceramics exhibit excellent thermal stability with relatively high thermal expansion coefficients(TECs)(Hf_(0.25),11.20×10-6 K-1,1000℃).Moreover,the matching calculation implied that the ODT further enhances the phonon scattering coefficient,leading to a relatively lower thermal conductivity of(La_(0.25)Eu_(0.25)Gd_(0.25)Yb_(0.25))2(Zr_(0.85)Ce_(0.15))_(2)O_(7)(1.48–1.51 W/(m·K),100–500℃)compared with other components.This present work provides a novel composition design principle for high-entropy ceramics,as well as a material selection rule for high-temperature insulation applications.展开更多
Kinetics of order-disorder transition at antiphase domain boundary （APDB） formed between L12 （Ni3A1） phases is investigated using microscopic phase-field model. The results demonstrate that whether order-disorder ...Kinetics of order-disorder transition at antiphase domain boundary （APDB） formed between L12 （Ni3A1） phases is investigated using microscopic phase-field model. The results demonstrate that whether order-disorder transition happens or not depends on the atomic structure of the APDB. Accompanied with the enrichment of V and depletion of Ni and A1, the ordered APDB with phase-shift vector of a/2[100] transforms into a thin disordered phase layer. Whereas at the APDB with phase shift vector of a/2[110], which remains ordered with temporal evolution, Ni and A1 enrich and V depletes. Composition evolution of APDB with order-disorder transition favors the nucleation of DO22 phase, and the formation of disordered phase layer accelerates the growth of DO22 phase. The disordered phase caused by order-disordered transition of the APDB can be considered as the transient phase along the precipitation path of DO22 phase.展开更多
The structural phase transition compound {[（CH3）2CHCH2]2NH2}·[CF3COO] （1） has been synthesized based on the diisobutylamine and trifluoroacetic acid. The DSC data reveal that 1 undergoes a phase transition at...The structural phase transition compound {[（CH3）2CHCH2]2NH2}·[CF3COO] （1） has been synthesized based on the diisobutylamine and trifluoroacetic acid. The DSC data reveal that 1 undergoes a phase transition at 277 K （Tc）. When one chlorine atom replaces one fluorine atom on trifluoroacetate anion, three order-disorder phase transitions at 251 K （Ti）, 282 K （T2） and 290 K could be achieved owing to a stepwise release of rotation motions of the anion and cation in {[（CH3）2CHCH2]2NH2}·[CF2C[COO] （2）. Based on the variable temperature crystal structures, the phase transition in compound 1 is triggered by the rotation of three fluorine atoms on the trifluoroacetate anion synchronized with the motions of the methyl groups on the diisobutylammonium cation. However, in compound 2, the phase transitions can be realized by a sequence of motions of both the anion and cation. Besides, the dielectric- temperature dependences were investigated in order to prove this regulation process. All of this investigation will be beneficial to design and synthesis of the novel phase transition materials and molecular dielectric materials on pur- pose.展开更多
An overview is presented on the order-disorder structural transitions and the dielectric mechanism in the complex-perovskite type relaxor ferroelectrics, i.e., the relaxors. Emphasis is put on the theoretical understa...An overview is presented on the order-disorder structural transitions and the dielectric mechanism in the complex-perovskite type relaxor ferroelectrics, i.e., the relaxors. Emphasis is put on the theoretical understanding of the structural transitions, the macroscopic dielectric properties, and the relationship between them. The influences of the composition, the temperature, and the atomic interactions on the order-disorder microstructures can be well understood in the cluster-variation-method calculations. The criterion drawn from theoretical analysis is successful in predicting the order-disorder structure of relaxors. Among various physical models about relaxors, the dipole glassy model that described the dielectric response as the thermally activated flips of the local spontaneous polarization under random interactions is discussed in details. The Monte Carlo simulation results of this model are consistent with the linear and nonlinear experiments of relaxors.展开更多
Organic ferroelastics with metal free features and intrinsically light weight are highly desirable for future applications in flexible,smart and biocompatible devices.However,organoferroelastics with plastic phase tra...Organic ferroelastics with metal free features and intrinsically light weight are highly desirable for future applications in flexible,smart and biocompatible devices.However,organoferroelastics with plastic phase transition have rarely been reported yet.Herein,we discovered ferroelasticity in a pair of organic enantiomers,(1S and/or 1R)-2,10-camphorsultam(S-and R-CPS),which undergoes a high-T_(c)plastic phase transition.Both large entropies change of∼45 J mol^(-1)K^(-1)and evidently ductile deformation process confirm the plastic phase feature.Strip-like ferroelastic domain patterns and bidirectional domain movements have been observed via polarized light microscopy and nanoindentation technique,respectively.This work highlights the discovery of organic ferroelastic combining the features of enantiomers and plastic phase transition,which contributes insights into exploration of organic multifunctional materials.展开更多
The intrinsic properties of theγ′phase are well known to be of critical importance for the targeted control of the mechanical performance ofγ/γ′high entropy alloys(HEAs).In the present work,a composition tuning s...The intrinsic properties of theγ′phase are well known to be of critical importance for the targeted control of the mechanical performance ofγ/γ′high entropy alloys(HEAs).In the present work,a composition tuning strategy is employed to modulate the thermal stability,elastic properties,and deformation mechanisms of theγ′phase in(FeCoNi)86Ti7Al7 HEAs using ab initio methods.Prior to tailoring the alloying elements,the temperature-dependent stability of theγ′phase is meticulously investigated by considering both enthalpic and entropic contributions.The findings reveal that the primary vibrational entropy can be effectively substituted by an empirical parameter(δ)to expedite the design of stable HEAs.Subsequently,based on the individual effects of elements on the order-disorder transformation temperatures(Tod)and practical considerations for high-temperature applications,eight substituting elements(Nb,Mo,Ta,W,V,Cr,Mn and Cu)are judiciously selected from the 3d,4d and 5d transition metal series.The results indicate that Nb and Ta are the most ideal substituting elements for theγ′phase,as they concurrently enhance the Tod,shear modulus,hardness,ductility,and antiphase boundary energy.These insights open a promising avenue for the innovative design of strong-yet-ductileγ/γ′HEAs.展开更多
The Fe-Ti binary system was re-assessed using the CALPHAD method in order to improve the capability of being extrapolated to a ternary or higher-order system. Compared with previous assessments, the main focus was put...The Fe-Ti binary system was re-assessed using the CALPHAD method in order to improve the capability of being extrapolated to a ternary or higher-order system. Compared with previous assessments, the main focus was put on the thermodynamic description of the two intermetallic compounds Fe2Ti and FeTi. The C14_Laves phase Fe2Ti was described by the two-sublattice model, which is widely used at present. By checking the homogeneity range on the boundary of the ternary systems involving the binary, the phase boundary of this compound was further confirmed. The FeTi phase with a BCC_B2 crystal structure was treated as the ordered phase of the BCC_A2 phase and a unified Gibbs energy function was used to describe both the ordered and disordered phases. Reproduction of the specific heat capacities of these compounds was another aspect paid particular attention to. Comprehensive comparisons of the calculated and experimental results regarding the phase diagram and thermodynamic properties show a good agreement between them and prove the validity of the present thermodynamic description.展开更多
The relationship between the structural stability and the long-range-order parameter of stoichiometry NiAl has been studied using effective atom model based on the embedded-atom-method(EAM) potential. The results obta...The relationship between the structural stability and the long-range-order parameter of stoichiometry NiAl has been studied using effective atom model based on the embedded-atom-method(EAM) potential. The results obtained from the computation show that NiAl lacks a metastable disordered structure intrinsically, and has the stable ordered B2 phase,which are consistent with experimental results.展开更多
The kinetics of internal boundaries relaxation: antiphase domain boundaries and interphase boundaries-in the conditions of high-temperature annealing and the structure transformations are investigated in homophase an...The kinetics of internal boundaries relaxation: antiphase domain boundaries and interphase boundaries-in the conditions of high-temperature annealing and the structure transformations are investigated in homophase and heterophase systems. Homophase systems look like ordered binary alloy and include antiphase domain boundaries of various orientation. Clear components border on ordered alloy in heterophase systems and two processes take place simultaneously here-disordering of binary alloy and solution in ordered phase of clear component. Computer experiment is realized in the sphere of temperatures close to the temperature of order-disorder phase transition in the limits of two-dimensional model of atom diffusion at the vacant knots of crystal lattics.展开更多
In this study,a new Dy-Eu-Tm co-doped cubic phase stabilized bismuth oxide solid electrolyte system was synthesized by using solid-state reaction method in atmospheric conditions.Before conductivity measurements,X-ray...In this study,a new Dy-Eu-Tm co-doped cubic phase stabilized bismuth oxide solid electrolyte system was synthesized by using solid-state reaction method in atmospheric conditions.Before conductivity measurements,X-ray diffraction(XRD)pro files of the annealed samples show that created mixtures have heterogeneous phase,but after conductivity measurements,the face-centered cubic(FCC)crystal structure is stabilized for all samples.Also,the increase in total dopant rate causes an increase in full width half maxima(FWHM)of main peak(111)on the XRD pattern while average crystal size decreases with it.On the other hand,the highest conductivity value was obtained for the sample having 15%total dopant rate with 0.62 S/cm at 750℃,whose dopants are evenly distributed in mole percent.Differential thermal analysis(DTA)results of the samples having 1:1:1 and 1:2:1 dopant content ratios show that endothermic peak occurs on their DTA curve,indicating crystal structure transformation such as phase transition or order-disorder transition.Also,thermo-gravimetric analysis(TGA)depending on temperature was evaluated in terms of mass loss.According to TGA curves,mass loss for both heating and cooling process can be negligible due to the small fluctuations(2%)on their TGA curves.展开更多
Theoretical investigation of the phase equilibria of the Fe-Ni alloy has been performed by combining the FLAPW total energy calculations and the Cluster Variation Method through the Cluster Expansion Method. The calcu...Theoretical investigation of the phase equilibria of the Fe-Ni alloy has been performed by combining the FLAPW total energy calculations and the Cluster Variation Method through the Cluster Expansion Method. The calculations have proved the stabilization of the LIE phase at 1：3 stoichiometry, which is in agreement with the experimental result, and predicted the existence of L1 0 as a stable phase below 550 K; this L1 0 phase has been missing in the conventional phase diagram. The calculations are extended to the Fe-rich region that is characterized by a wide range phase separation and has drawn considerable attention because of the intriguing Invar property associated with a Fe concentration of 65%. To reveal the origin of the phase separation, a P-V curve in an entire concentration range is derived by the second derivative of free energy functional of the disordered phase with respect to the volume. The calculation confirmed that the phase separation is caused by the breakdown of the mechanical-stability criterion. The newly calculated phase separation line combined with the L1 0 and L12Eorder-disordered phase boundaries provides phase equilibria in the wider concentration range of the system. Furthermore, a coefficient of thermal expansion （CTE） is attempted by incorporating the thermal vibration effect through harmonic approximation of the Debye-Gruneisen model. The Invar behavior has been reproduced, and the origin of this anomalous volume change has been discussed.展开更多
As an example of the La-Mg-Y system, the method how to set up the themaodynamic model of individual phases was introduced in the process of thermodynamic optimization. The solution phases （liquid, body-centered cubic...As an example of the La-Mg-Y system, the method how to set up the themaodynamic model of individual phases was introduced in the process of thermodynamic optimization. The solution phases （liquid, body-centered cubic, face-centered cubic, hexagonal close-packed and double hexagonal close-packed） were modeled with the Redlich-Kister equation. The compound energy model has been used to describe the thermodynamic functions of the intermetallic compounds in the La-Mg-Y systems. The compounds Mg2Y, Mg24Y5, Mg12La, Mg17La2, Mg41Las, Mg3La and Mg2La in the La-Mg-Y system were treated as the formulae （Mg,Y）2（La,Mg,Y）, Mg24（La,Mg,Y）4Y, Mg12（La, Y）, Mg17（La,Y）2, Mg41（La,Y）5, Mg3（La,Mg,Y） and Mg2（La, Y）, respectively. A model （La, Mg,Y）0.5（La,Mg,Y）0.5 was applied to describe the compound MgM formed by MgLa and MgY in order to cope with the order-disorder transition between body-centered cubic solution （A2） and MgM with CsCl-type structure （B2） in the La-Mg-Y system. The Gibbs energies of individual phases were optimized in the La-Mg, La-Y and La-Mg-Y systems by CALPHAD technique. The projection of the liquidus surfaces for the La-Mg-Y system was predicted. The Mg-based alloys database including 36 binary and 15 ternary systems formed by Mg, Al, Cu, Ni, Mn, Zn and rare earth elements was set up in SGTE standard.展开更多
基金The research was funded by the National Natural Science Foundation of China(No.51802120,51872126,22075103,51672111)Guangdong Basic and Applied Basic Research Foundation for Distinguished Young Scholar(No.2019B151502030)+7 种基金Natural Science Foundation of Guangdong Province(No.2018030310181)the Science and Technology Plan Project of Guangzhou(No.202002030159)Guangdong Basic and Applied Basic Research Foundation for Young Scholar(No.2020A1515111057)‘100 Talents Program of Hebei Province’(No.E2014100008)the Fundamental Research Funds for the Central Universities(No.21619406)X.Y.thanks for the Special Funds for the Cultivation of Guangdong College Students'Scientific and Technological Innovation("Climbing Program"Special Funds)(No.pdjh2019a0055)J.Fan also thanks for the project support for"Young Top talents"in the Pearl River Talent Project of Guangdong Province(2017GC010424)the Guangdong Provincial Innovation and Entrepreneurship Project(grant 2016ZT06D081).
文摘Multifunctional lead-free double perovskites demonstrate remarkable potential towards applications in various fields.Herein,an environmentally-friendly,low-cost,high-throughput Cs_(2)NaFeCl_(6) single crystal with exceedingly high thermal stability is designed and grown.It obtains a cubic lattice system in the temperature range of 80-500 K,accompanied by a completely reversible chromatic variation ranging from yellow to black.Importantly,the intriguing thermochromism is proved to own extremely high reproducibility(over 1000 cycles)without a hysteretic effect,originating from its structural flexibility that including(i)the noteworthy distortion/deformation of[NaCl_(6)]5−and[FeCl_(6)]3−octahedra;(ii)order-disorder arrangement transition of[NaCl_(6)]5−and[FeCl6]3−octahedra as the function of temperature.This study paves the way towards a new class of smart windows and camouflage coatings with an unprecedented colour range based on a Cs_(2)NaFeCl_(6) perovskite.
基金This work was financially supported by the National Natural Science Foundation of China under Contract No.59895151-01
文摘The embedded atom method (EAM) was used to study the order-disorder transformation in gamma -TiAl alloy with L1(0). structure at stoichiometrical composition, and the effect of lattice constants was also investigated. It was found that the gamma -TiAl alloy at stoichiometrical composition exhibits a second-order transition, and the relations between lattice constants a, c and the long-range order sigma are not linear. The lattice constant a decreases whereas c increases with the increase of the long-range order parameter. In this case the ordering induces the transformation from cubic to tetragonal. The change of the lattice constant during the ordering processes can be interpreted in terms of bond length.
基金This work was supported by the National Natural Science Foundation of China(No.21403292,No.21403293,No.21473249,and No.21673285),and the funding from the Shenzhen city(No.JCYJ20170307150520453).
文摘To understand and control the interfacial properties of polydiacetylenes(PDAs)vesicles withπ-conjugated backbone is very important for their colorimetric sensing of chemical and biological targets.In this work,we adopted 10,12-pentacosadiynoic acid(PCDA)as the model molecule to prepare PDAs vesicles in aqueous solution with different forms(from monomer to blue-to-purple-to-red phase)by controlling the UV irradiation dose.The variations of the interfacial conformation of PDAs vesicles during chromatic transitions were inspected by the adsorption behaviors of probe molecules(4-(4-diethylaminostyry)-1-methylpyridinium iodide,D289)on vesicle surface with surface-specific second harmonic generation(SHG)and zeta potential measurements.Resonant SHG signal from D289 adsorbed on vesicle surface attenuated sharply,and the adsorption free energy as well as the corresponding two-photon fluorescence signal decreased slightly in chromatic transitions.While,the change in the surface density of the adsorbed D289 molecules for PDAs vesicles with different forms was relatively small as estimated from zeta potential measurements.The attenuation of the SHG intensity was thus attributed to the overall order-disorder transition and the changed orientation of D289 molecules caused by the gradual distortion of carboxyl head group driven by backbone perturbation.
基金supported by the Major Scientific and Technological Projects in Yunnan Province(No.202002AB080001-1)the National Natural Science Foundation of China(Nos.U1602275 and 51971059).Special thanks are due to the instrumen-tal data analysis from the Analytical and Testing Center,Northeast-ern University。
文摘The Fe-Pt based intermetallic compounds exhibit good chemical stability and unique magnetic proper-ties,where Ni is an important additional element to optimize the magnetic properties or obtain the outstanding catalytic performances of the Fe-Pt based alloys.Knowledge of how Ni addition affects the order-disorder transitions of the Fe-Pt intermetallics is thus necessary;however,the related information is limited.Therefore,in this work,the phase diagrams of the Fe-Ni-Pt system were experimentally in-vestigated,and as a result,the isothermal sections of the Fe-Ni-Pt system at 600 and 900℃,as well as the vertical sections of Fe_(80)Ni_(20)-Pt_(80)Ni_(20)and Fe_(50)Pt_(50)-Ni_(50)Pt_(50)were constructed.Based on these re-sults,the influences of Ni addition on the crystal stabilities and phase transformations of the ordered Fe-Pt intermetallics have been well described.The results show that the L1_(0)-FePt and L1_(0)-NiPt phases form a ternary continuous solid solution of L1_(0)-(Fe,Ni)Pt,whereas Ni can dissolve in the L1_(2)-Fe_(3)Pt and L1_(2)-FePt_(3)phases as high as 57.0 at.%and 26.0 at.%at 600℃,respectively.The selective occupancy of Ni atoms has been predicted,which should depend on the alloy composition.For both the L1_(0)-(Fe,Ni)Pt and L1_(2)-FePt_(3)phases,when Pt contents are less than their stoichiometric values,Ni atoms will preferentially occupy the Pt sublattice,forming as many nearest-neighbor Fe-Pt bonds as possible.All these results can correlate the alloy compositions,annealing temperatures and crystal structures to both magnetic and catalytic properties,thus providing a basis for optimizing the Fe-Ni-Pt alloys towards enhanced magnetic or catalytic performances.
基金This work was supported by the Foundation of Civil Aviation University of China (No. 2001-3-18).
文摘Based on cluster variation method (CVM) and natural iteration method (MM),order-disorder phase transition in the intercalation compounds M_(1/2)TiS_2 is simulated bycomputer. The favorable conditions, under which 3^(1/2)a_0 x a_0 superstructure is formed, aregiven, and the results are in good agreement with the experiments and theoretical calculations. Therelationship between critical temperature and M-ion-vacancy interaction parameter is linear.
基金Sponsored by the National Key Research and Development Program(Grant No.2016YFB0100500)
文摘After describing research status of super-structure for Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2,diffraction patterns of Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2 in different order parameters have been researched by Powder-cell program,including crystal structure,X-ray and neutron diffraction pattern,anomalous diffraction pattern and comparison of NiCoMn in different positions. The influence of order parameters on intensity of matrix and super-lattice diffraction lines has also been analyzed and the summarization and prospect have been made lastly.
基金This work was financially supported by the National Natural Science Foundation of China under contract No. 59895151-01.
文摘Based on pair potential, the Bragg Williams (B-W) model is modified to takeinto account the effect of the lattice parameter on theoretical order-disorder transformationanalysis. The main purpose of this work is to understand the basic aspects of this effect andrelated reasonable model on order-disorder transformation. In the present approach, theconfiguration free energy is chosen as function of the lattice parameter and the long-range order.This energy is calculated through Taylor's expansion, starting from the disordered state. It wasfound that the configuration free energy has been strongly modified when the lattice parameter istaken into account. It was also found only one type of order-disorder transformation exists in ABalloy and three kinds of order-disorder transformations for non-equiatomic alloy system such as A_3Balloy. This result is in agreement with experiments.
基金the National Natural Science Foundation of China under contract No. 59895151-01.]
文摘The embedded atom method (EAM) was used to theoretically analyze the effect of the lattice parameter variation on the order-disorder transformation in binary alloys. Based on EAM, it is found that only one kind of order-disorder transition (second-order transition) exists for AB alloy. Three groups of order-disorder transformation can be observed for the A(3)B or AB(3) compounds. For group I, the order-disorder is a completely first-order transition. For group II, the order-disorder transformation is a classical first-order transition. For group III, the order-disorder transformation is found to be a second-order transition. The lattice parameter variations have a significant effect on E-2 coefficient, which is related to the ordering energy. These results are in good agreement with experiments.
基金This work was supported by the National Natural Science Foundation of China(No.52072301)State Key Laboratory of New Ceramics and Fine Processing Tsinghua University(No.KFZD202102)+3 种基金State Key Laboratory of Solidification Processing(NPU)(No.2021-TS-08)the China–Poland International Collaboration Fund of the National Natural Science Foundation of China(No.51961135301)the Fundamental Research Funds for the Central Universities(No.D5000210722)State Key Laboratory of Materials Processing and Die&Mould Technology,Huazhong University of Science and Technology(No.P2020-009)。
文摘The order–disorder transition(ODT)of A_(2)B_(2)O_(7)compounds obtained enormous attention owing to the potential application for thermal barrier coating(TBC)design.In this work,the influence of ODT on the mechanical and thermophysical properties of dual-phase A_(2)B_(2)O_(7)high-entropy ceramics was investigated by substituting Ce^(4+)and Hf^(4+)with different ionic radii on B-sites(Zr^(4+)).The X-ray diffraction(XRD),Raman,and transmission electron microscopy(TEM)results show that rA3+/rB^(4+)=1.47 is the critical value of ODT phase boundary with different doping B-site ion contents,and the energy dispersive spectroscopy(EDS)results further indicate the uniform distribution of elements.Interestingly,owing to the high intrinsic disorder derived from high-entropy effect,the A_(2)B_(2)O_(7)high-entropy ceramics exhibit unreduced modulus(E0≈230 GPa)and enhanced mechanical properties(HV≈10 GPa,KIC≈2.3 MPa·m^(0.5)).A_(2)B_(2)O_(7)high-entropy ceramics exhibit excellent thermal stability with relatively high thermal expansion coefficients(TECs)(Hf_(0.25),11.20×10-6 K-1,1000℃).Moreover,the matching calculation implied that the ODT further enhances the phonon scattering coefficient,leading to a relatively lower thermal conductivity of(La_(0.25)Eu_(0.25)Gd_(0.25)Yb_(0.25))2(Zr_(0.85)Ce_(0.15))_(2)O_(7)(1.48–1.51 W/(m·K),100–500℃)compared with other components.This present work provides a novel composition design principle for high-entropy ceramics,as well as a material selection rule for high-temperature insulation applications.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50941020, 10902086, 50875217,and 20903075)the Natural Science Foundation of Shaanxi Province (Grant Nos.SJ08-ZT05 and SJ08-B14)the Doctorate Foundation of Northwest Polytechnical University (Grant No.CX200905)
文摘Kinetics of order-disorder transition at antiphase domain boundary （APDB） formed between L12 （Ni3A1） phases is investigated using microscopic phase-field model. The results demonstrate that whether order-disorder transition happens or not depends on the atomic structure of the APDB. Accompanied with the enrichment of V and depletion of Ni and A1, the ordered APDB with phase-shift vector of a/2[100] transforms into a thin disordered phase layer. Whereas at the APDB with phase shift vector of a/2[110], which remains ordered with temporal evolution, Ni and A1 enrich and V depletes. Composition evolution of APDB with order-disorder transition favors the nucleation of DO22 phase, and the formation of disordered phase layer accelerates the growth of DO22 phase. The disordered phase caused by order-disordered transition of the APDB can be considered as the transient phase along the precipitation path of DO22 phase.
基金This work was financially supported by the 973 Pro- ject from the Ministry of Science and Technology of China （No. 2014CB84561）, and the National Natural Science Foundation of China （Nos. 21571150, 21431005 and 21390391）.
文摘The structural phase transition compound {[（CH3）2CHCH2]2NH2}·[CF3COO] （1） has been synthesized based on the diisobutylamine and trifluoroacetic acid. The DSC data reveal that 1 undergoes a phase transition at 277 K （Tc）. When one chlorine atom replaces one fluorine atom on trifluoroacetate anion, three order-disorder phase transitions at 251 K （Ti）, 282 K （T2） and 290 K could be achieved owing to a stepwise release of rotation motions of the anion and cation in {[（CH3）2CHCH2]2NH2}·[CF2C[COO] （2）. Based on the variable temperature crystal structures, the phase transition in compound 1 is triggered by the rotation of three fluorine atoms on the trifluoroacetate anion synchronized with the motions of the methyl groups on the diisobutylammonium cation. However, in compound 2, the phase transitions can be realized by a sequence of motions of both the anion and cation. Besides, the dielectric- temperature dependences were investigated in order to prove this regulation process. All of this investigation will be beneficial to design and synthesis of the novel phase transition materials and molecular dielectric materials on pur- pose.
基金State Key Program of Basic ResearchDevelopm ent! (No.G2 0 0 0 0 6 710 8) the NationalNatural Science Foundation of Chin
文摘An overview is presented on the order-disorder structural transitions and the dielectric mechanism in the complex-perovskite type relaxor ferroelectrics, i.e., the relaxors. Emphasis is put on the theoretical understanding of the structural transitions, the macroscopic dielectric properties, and the relationship between them. The influences of the composition, the temperature, and the atomic interactions on the order-disorder microstructures can be well understood in the cluster-variation-method calculations. The criterion drawn from theoretical analysis is successful in predicting the order-disorder structure of relaxors. Among various physical models about relaxors, the dipole glassy model that described the dielectric response as the thermally activated flips of the local spontaneous polarization under random interactions is discussed in details. The Monte Carlo simulation results of this model are consistent with the linear and nonlinear experiments of relaxors.
基金supported by the National Natural Science Foundation of China(No.22271131)the Department of Science and Technology in Jiangxi Province(No.20225BCJ23029).
文摘Organic ferroelastics with metal free features and intrinsically light weight are highly desirable for future applications in flexible,smart and biocompatible devices.However,organoferroelastics with plastic phase transition have rarely been reported yet.Herein,we discovered ferroelasticity in a pair of organic enantiomers,(1S and/or 1R)-2,10-camphorsultam(S-and R-CPS),which undergoes a high-T_(c)plastic phase transition.Both large entropies change of∼45 J mol^(-1)K^(-1)and evidently ductile deformation process confirm the plastic phase feature.Strip-like ferroelastic domain patterns and bidirectional domain movements have been observed via polarized light microscopy and nanoindentation technique,respectively.This work highlights the discovery of organic ferroelastic combining the features of enantiomers and plastic phase transition,which contributes insights into exploration of organic multifunctional materials.
基金supported by the National Natural Science Foundation of China(Nos.52371014 and U22B20132)Shenzhen Science and Technology Program(No.JCYJ20230807091401004)+1 种基金Fundamental Research Funds for the Central Universities(No.20720230036)Guided Subject of Dean’s Fund(No.YZJJ-YDL-0004).
文摘The intrinsic properties of theγ′phase are well known to be of critical importance for the targeted control of the mechanical performance ofγ/γ′high entropy alloys(HEAs).In the present work,a composition tuning strategy is employed to modulate the thermal stability,elastic properties,and deformation mechanisms of theγ′phase in(FeCoNi)86Ti7Al7 HEAs using ab initio methods.Prior to tailoring the alloying elements,the temperature-dependent stability of theγ′phase is meticulously investigated by considering both enthalpic and entropic contributions.The findings reveal that the primary vibrational entropy can be effectively substituted by an empirical parameter(δ)to expedite the design of stable HEAs.Subsequently,based on the individual effects of elements on the order-disorder transformation temperatures(Tod)and practical considerations for high-temperature applications,eight substituting elements(Nb,Mo,Ta,W,V,Cr,Mn and Cu)are judiciously selected from the 3d,4d and 5d transition metal series.The results indicate that Nb and Ta are the most ideal substituting elements for theγ′phase,as they concurrently enhance the Tod,shear modulus,hardness,ductility,and antiphase boundary energy.These insights open a promising avenue for the innovative design of strong-yet-ductileγ/γ′HEAs.
基金Project (IP08-092009) supported by Sino Swiss Science and Technology Cooperation (SSSTC)Project (50971136) supported by the National Natural Science Foundation of ChinaProject (1343-71134001013) supported by the Scholarship Award for Excellent Doctoral Student granted by Ministry of Education of China
文摘The Fe-Ti binary system was re-assessed using the CALPHAD method in order to improve the capability of being extrapolated to a ternary or higher-order system. Compared with previous assessments, the main focus was put on the thermodynamic description of the two intermetallic compounds Fe2Ti and FeTi. The C14_Laves phase Fe2Ti was described by the two-sublattice model, which is widely used at present. By checking the homogeneity range on the boundary of the ternary systems involving the binary, the phase boundary of this compound was further confirmed. The FeTi phase with a BCC_B2 crystal structure was treated as the ordered phase of the BCC_A2 phase and a unified Gibbs energy function was used to describe both the ordered and disordered phases. Reproduction of the specific heat capacities of these compounds was another aspect paid particular attention to. Comprehensive comparisons of the calculated and experimental results regarding the phase diagram and thermodynamic properties show a good agreement between them and prove the validity of the present thermodynamic description.
文摘The relationship between the structural stability and the long-range-order parameter of stoichiometry NiAl has been studied using effective atom model based on the embedded-atom-method(EAM) potential. The results obtained from the computation show that NiAl lacks a metastable disordered structure intrinsically, and has the stable ordered B2 phase,which are consistent with experimental results.
文摘The kinetics of internal boundaries relaxation: antiphase domain boundaries and interphase boundaries-in the conditions of high-temperature annealing and the structure transformations are investigated in homophase and heterophase systems. Homophase systems look like ordered binary alloy and include antiphase domain boundaries of various orientation. Clear components border on ordered alloy in heterophase systems and two processes take place simultaneously here-disordering of binary alloy and solution in ordered phase of clear component. Computer experiment is realized in the sphere of temperatures close to the temperature of order-disorder phase transition in the limits of two-dimensional model of atom diffusion at the vacant knots of crystal lattics.
文摘In this study,a new Dy-Eu-Tm co-doped cubic phase stabilized bismuth oxide solid electrolyte system was synthesized by using solid-state reaction method in atmospheric conditions.Before conductivity measurements,X-ray diffraction(XRD)pro files of the annealed samples show that created mixtures have heterogeneous phase,but after conductivity measurements,the face-centered cubic(FCC)crystal structure is stabilized for all samples.Also,the increase in total dopant rate causes an increase in full width half maxima(FWHM)of main peak(111)on the XRD pattern while average crystal size decreases with it.On the other hand,the highest conductivity value was obtained for the sample having 15%total dopant rate with 0.62 S/cm at 750℃,whose dopants are evenly distributed in mole percent.Differential thermal analysis(DTA)results of the samples having 1:1:1 and 1:2:1 dopant content ratios show that endothermic peak occurs on their DTA curve,indicating crystal structure transformation such as phase transition or order-disorder transition.Also,thermo-gravimetric analysis(TGA)depending on temperature was evaluated in terms of mass loss.According to TGA curves,mass loss for both heating and cooling process can be negligible due to the small fluctuations(2%)on their TGA curves.
文摘Theoretical investigation of the phase equilibria of the Fe-Ni alloy has been performed by combining the FLAPW total energy calculations and the Cluster Variation Method through the Cluster Expansion Method. The calculations have proved the stabilization of the LIE phase at 1：3 stoichiometry, which is in agreement with the experimental result, and predicted the existence of L1 0 as a stable phase below 550 K; this L1 0 phase has been missing in the conventional phase diagram. The calculations are extended to the Fe-rich region that is characterized by a wide range phase separation and has drawn considerable attention because of the intriguing Invar property associated with a Fe concentration of 65%. To reveal the origin of the phase separation, a P-V curve in an entire concentration range is derived by the second derivative of free energy functional of the disordered phase with respect to the volume. The calculation confirmed that the phase separation is caused by the breakdown of the mechanical-stability criterion. The newly calculated phase separation line combined with the L1 0 and L12Eorder-disordered phase boundaries provides phase equilibria in the wider concentration range of the system. Furthermore, a coefficient of thermal expansion （CTE） is attempted by incorporating the thermal vibration effect through harmonic approximation of the Debye-Gruneisen model. The Invar behavior has been reproduced, and the origin of this anomalous volume change has been discussed.
基金This work was financially supported by the National Natural Science Foundation of China (Nos. 50471095 and 50271008).
文摘As an example of the La-Mg-Y system, the method how to set up the themaodynamic model of individual phases was introduced in the process of thermodynamic optimization. The solution phases （liquid, body-centered cubic, face-centered cubic, hexagonal close-packed and double hexagonal close-packed） were modeled with the Redlich-Kister equation. The compound energy model has been used to describe the thermodynamic functions of the intermetallic compounds in the La-Mg-Y systems. The compounds Mg2Y, Mg24Y5, Mg12La, Mg17La2, Mg41Las, Mg3La and Mg2La in the La-Mg-Y system were treated as the formulae （Mg,Y）2（La,Mg,Y）, Mg24（La,Mg,Y）4Y, Mg12（La, Y）, Mg17（La,Y）2, Mg41（La,Y）5, Mg3（La,Mg,Y） and Mg2（La, Y）, respectively. A model （La, Mg,Y）0.5（La,Mg,Y）0.5 was applied to describe the compound MgM formed by MgLa and MgY in order to cope with the order-disorder transition between body-centered cubic solution （A2） and MgM with CsCl-type structure （B2） in the La-Mg-Y system. The Gibbs energies of individual phases were optimized in the La-Mg, La-Y and La-Mg-Y systems by CALPHAD technique. The projection of the liquidus surfaces for the La-Mg-Y system was predicted. The Mg-based alloys database including 36 binary and 15 ternary systems formed by Mg, Al, Cu, Ni, Mn, Zn and rare earth elements was set up in SGTE standard.
