The cryo-fracture electron microscope was used to study the micro-structure of pesticide mi-croemulsions. The hydromechanical radius (Rh) and the distribution (fRh) of pesticide microemulsions were determined by photo...The cryo-fracture electron microscope was used to study the micro-structure of pesticide mi-croemulsions. The hydromechanical radius (Rh) and the distribution (fRh) of pesticide microemulsions were determined by photo-correlation spectroscopy. This study showed that the Rh was significantly greater when the ratio of surfactants to water (w/w) decreased to 20/31 from 27/26, and a bicontinuous structure was formed when the ratio dropped to 15/36. These results explained the relationship between pesticide properties and the microscopic structure, and provided a good method for studying the microscopic structure of pesticide formulations.展开更多
The quasicrystal phase is beneficial to increasing the strength of magnesium alloys.However,its complicated structure and unclear phase relations impede the design of alloys with good mechanical properties.In this pap...The quasicrystal phase is beneficial to increasing the strength of magnesium alloys.However,its complicated structure and unclear phase relations impede the design of alloys with good mechanical properties.In this paper,the Mg_(40)Zn_(55)Nd_(5) icosahedral quasicrystal(I-phase)structure is discovered in an as-cast Mg-58Zn-4Nd alloy by atomic resolution high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).A cloud-like morphology is observed with Mg_(41.6)Zn_(55.0)Nd_(3.4) composition.The selected area electronic diffrac-tion(SAED)analysis shows that the icosahedral quasicrystal structure has 5-fold,4-fold,3-fold,and 2-fold symmetry zone axes.The thermo-dynamic stability of the icosahedral quasicrystal is investigated by differential scanning calorimetry(DSC)in the annealed alloys.When an-nealed above 300℃,the Mg_(40)Zn_(55)Nd_(5) quasicrystal is found to decompose into a stable ternary phase Mg_(35)Zn_(60)Nd_(5),a binary phase MgZn,andα-Mg,suggesting that the quasicrystal is a metastable phase in the Mg-Zn-Nd system.展开更多
The electronic and optical characteristics of the Sc2 CoSi Heusler with L21 structure and also the surface effect on electronic and optical properties, and the ?lms thermodynamic stability of the [001] direction in fo...The electronic and optical characteristics of the Sc2 CoSi Heusler with L21 structure and also the surface effect on electronic and optical properties, and the ?lms thermodynamic stability of the [001] direction in four cases including:Sc-Sc, Sc-Co, Sc-Si and Co-Si terminations are studied using the ?rst principles calculations(FPLAPW) within the framework of the density functional theory(DFT). The band structure calculations represent the ferromagnetic halfmetallic properties with 100% spin polarization and 0.54 e V indirect gap in spin down for Sc2 CoSi bulk with optimized lattice parameters of 6.25 A?. The total magnetic moment obtained for this compound is-1.0 μB, which is in accordance with Slater-Pauling rule. The half-metallic(HM) behavior by 100% spin polarization at Fermi level is occurred in the Sc-Si termination with a 0.32 eV gap in down spin. The optical responses have been calculated for the bulk and ScSi termination by a red shift in these parameters and the metallic treatments have been increased. According to the thermodynamic phase diagrams, it is shown the Sc-Si and Sc-Sc terminations are more stable than other terminations.展开更多
A matrix eigenvalue method is applied to analyse the thermodynamic stability of two-component interacting fermions. The non-relativistic and ultra-relativistic d = 1, 2, 3 dimensions have been discussed in detail, res...A matrix eigenvalue method is applied to analyse the thermodynamic stability of two-component interacting fermions. The non-relativistic and ultra-relativistic d = 1, 2, 3 dimensions have been discussed in detail, respectively. The corresponding stability region has been given according to the two-body interaction strength and the particle number density ratio.展开更多
A new Co（Ⅲ） complex with a tripodal amide ligand [CoL（N3）3] （L = N-acetyl- N＇,N＇-bis-[（2-pyridyl）methyl]-ethylenediamine） has been synthesized and characterized structurally by X-ray diffraction. It crystal...A new Co（Ⅲ） complex with a tripodal amide ligand [CoL（N3）3] （L = N-acetyl- N＇,N＇-bis-[（2-pyridyl）methyl]-ethylenediamine） has been synthesized and characterized structurally by X-ray diffraction. It crystallizes in orthorhombic, space group Pnma with a = 9.2515（19）, b = 12.729（3）, c = 17.273（4） A, V = 2034.0（7） A3, C16H20CoN13O, Mr = 469.38, Dc = 1.533 g/cm3, μ（MoKα） = 0.884 mm^-1, F（000） = 968, Z = 4, the final R = 0.0392 and wR = 0.0818 for 2430 observed reflections. In the complex, the amide ligand L acts as a tridentate fashion and coordinates to the Co（Ⅲ） ion through three nitrogen atoms, while the other three positions of the Co（Ⅲ） center are occupied by three terminal azide anions. The complex is connected as a 1D chain structure by intermolecular hydrogen bonds between the uncoordinated amide groups. In order to investigate the coordination ability, thermodynamic stability of the ligand L with the first-series transition metal ions （Co（Ⅱ）, Ni（Ⅱ）, Cu（Ⅱ） and Zn（Ⅱ）） has been studied by potentiometric titration, and the results show that the order of their stability constants conforms to the Irving-Williams sequence.展开更多
Thermal denaturation and stability of two commercially available preparations of Human Serum Albumin (HSA), differing in their advertised level of purity, were investigated by differential scanning calorimetry (DSC). ...Thermal denaturation and stability of two commercially available preparations of Human Serum Albumin (HSA), differing in their advertised level of purity, were investigated by differential scanning calorimetry (DSC). These protein samples were 99% pure HSA (termed HSA<sub>99</sub>) and 96% pure HSA (termed HSA<sub>96</sub>). According to the supplier, the 3% difference in purity between HSA<sub>96</sub> and HSA<sub>99</sub> is primarily attributed to the presence of globulins and fatty acids. Our primary aim was to investigate the utility of DSC in discerning changes in HSA that occur when the protein is specifically adducted, and determine how adduct formation manifests itself in HSA denaturation curves, or thermograms, measured by DSC. Effects of site specific covalent attachment of biotin (the adduct) on the thermodynamic stability of HSA were investigated. Each of the HSA preparations was modified by biotinylation targeting a single site, or multiple sites on the protein structure. Thermograms of both modified and unmodified HSA samples successfully demonstrated the ability of DSC to clearly discern the two HSA preparations and the presence or absence of covalent modifications. DSC thermogram analysis also provided thermodynamic characterization of the different HSA samples of the study, which provided insight into how the two forms of HSA respond to covalent modification with biotin. Consistent with published studies [1] HSA<sub>96</sub>, the preparation with contaminants that contain globulins and fatty acids seems to be comprised of two forms, HSA<sub>96-L</sub> and HSA<sub>96-H</sub>, with HSA<sub>96-L</sub> more stable than HSA<sub>99</sub>. The effect of multisite biotinylation is to stabilize HSA<sub>96-L</sub> and destabilize HSA<sub>96-H</sub>. Thermodynamic analysis suggests that the binding of ligands comprising the fatty acid and globulin-like contaminant contributes approximately 6.7 kcal/mol to the stability HSA<sub>96-L</sub>.展开更多
Alloying strategies provide a high degree of freedom for reducing lead toxicity,improving thermodynamic stability, tuning the optoelectronic properties of ABX3 halide perovskites by varying the alloying element specie...Alloying strategies provide a high degree of freedom for reducing lead toxicity,improving thermodynamic stability, tuning the optoelectronic properties of ABX3 halide perovskites by varying the alloying element species and their contents.Given the key role of B-site cations in contributing band edge states and modulating structure factors in halide perovskites,the partial replacement of Pb2+with different B-site metal ions has been proposed.Although several experimental attempts have been made to date,the effect of B-site alloying on the stability and electronic properties of halide perovskites has not been fully explored.Herein,we take cubic CsPbBr3 perovskite as the prototype material and systematically explore the effects of B-site alloying on Pb-containing perovskites.According to the presence or absence of the corresponding perovskite phase,the ten alloying elements investigated are classified into three types(i.e.,Type Ⅰ:Sn Ge,Ca,Sr;Type Ⅱ:Cd,Mg,Mn;Type Ⅲ:Ba,Zn,Cu).Based on the first-principles calculations,we obtain the following conclusions.First,these B-site alloys will exist as disordered solid solutions rather than ordered structures at room temperature throughout the composition space.Second,the alloying of Sn and Ge enhances the thermodynamic stability of the cubic perovskite host,whereas the alloying of the other elements has no remarkable effect on the thermodynamic stability of the cubic perovskite host.Third,the underlying physical mechanism for bandgap tuning can be attributed to the atomic orbital energy mismatch or quantum confinement effect.Fourth,the alloying of different elements demonstrates the diversity in the regulation of crystal structure and electronic properties,indicating potential applications in photovoltaic s and self-trapped exciton-based light-emitting applications.Our work provides theoretical guidance for using alloying strategies to reduce lead toxicity,enhance stability,and optimize the electronic properties of halide perovskites to meet the needs of optoelectronic applications.展开更多
We present here a thermodynamic assessment of the stability behavior in acid environment at 298 and 353 K(80◦C)of two iron(II)hexa-aza-macrocyclic complexes and of an hexa-aza-iron-based site(Fe^(II)N_((4+2))/C)that s...We present here a thermodynamic assessment of the stability behavior in acid environment at 298 and 353 K(80◦C)of two iron(II)hexa-aza-macrocyclic complexes and of an hexa-aza-iron-based site(Fe^(II)N_((4+2))/C)that should potentially be active for the oxygen reduction reaction in proton exchange membrane(PEM)fuel cells.The calculations of the equilibrium constant(K c)for the demetallation reaction indicate that the iron(II)-hexa-aza-macrocyclic complexes and Fe^(II)N_((4+2))/C are chemically stable in an acid medium at 298 and 353 K.Compared with two other potential model sites(Fe^(II)N_((4+2))/C and Fe II N(2+2)/C)that were thought to be present in the same Fe-based catalysts,K c of Fe^(II)N_((4+2))/C is two to three orders of magnitude smaller at 353 K,and three to four orders of magnitude smaller at 298 K,than K c for Fe^(II)N_((4+2))/C or Fe II N(2+2)/C,revealing the great chemical stability of Fe^(II)N_((4+2))/C.In this work,we discuss about a novel proposition that the two catalytic sites active in these Fe-based catalysts are Fe II N_(4)/C and Fe^(II)N_((4+2))/C.This proposition is in agreement with the durability behavior of these catalysts in PEM fuel cells and also with their known physico-chemical characterizations.The origin of the fast and slow decay behaviors of the different sites,which are active at the Fe–N–C-based cathode of PEM fuel cells,is also discussed.展开更多
A series of thermodynamic parameters in formation of ultrafine monodispersed colloidal particles of Y(OH)CO3 were measured, estimated and calculated. The thermodynamic stability of Y(OH)CO3 colloidal particles was stu...A series of thermodynamic parameters in formation of ultrafine monodispersed colloidal particles of Y(OH)CO3 were measured, estimated and calculated. The thermodynamic stability of Y(OH)CO3 colloidal particles was studied and discussed by phenomenological model. It is suggested that ultrafine monodispersed colloidal particles of Y(OH)CO3 are stable only in a very narrow temporary supersaturation range ( 1<x<1 .08).展开更多
Kagome materials host intertwined phenomena,including nontrivial band topology,superconductivity,and complex charge-density-wave order,making them an important platform in condensed-matter physics and materials scienc...Kagome materials host intertwined phenomena,including nontrivial band topology,superconductivity,and complex charge-density-wave order,making them an important platform in condensed-matter physics and materials science.Motivated by extensive studies on the AV_(3)Sb_(5) family of materials,we perform high-throughput first-principles calculations to screen bilayer kagome AM_(6)X_(6) compounds with an MgFe_(6)Ge_(6)-prototype structure as potential weak-coupling superconductors.Thereafter,we systematically evaluate the thermodynamic,dynamic,and magnetic stabilities,followed by electron–phonon coupling(EPC)calculations and superconducting transition temperature estimates based on the Allen–Dynes-modified McMillan equation.From 168 candidates,we identify 31 weak-coupling superconductors that satisfy both the thermodynamic and dynamical stability criteria in our screening workflow.Focusing on compounds without partially filled f shells,we obtain superconducting transition temperatures(T_(c))of 0.65–3.97 K with EPC constants λ=0.37–0.62,indicating conventional weak-coupling superconductivity.The EPC is typically driven by vibrations within the kagome layers,with Sn-containing materials exhibiting low-frequency soft modes that contribute significantly to λ.By providing a global mapping of stability and weak-coupling superconductivity in bilayer kagome AM_(6)X_(6) compounds,this study offers a practical theoretical database and design principles for future experimental exploration.展开更多
Lemon oil (LO), also known as <em>Citrus limonum</em> is a highly volatile essential oil (EO) with potential therapeutic properties like anti-oxidative, anti-proliferative, anti-fungal and anti-cancerous. ...Lemon oil (LO), also known as <em>Citrus limonum</em> is a highly volatile essential oil (EO) with potential therapeutic properties like anti-oxidative, anti-proliferative, anti-fungal and anti-cancerous. However, the efficacy of LO is limited due to its physiological factors such as high volatility, poor stability (particularly sensitive to sunlight) and quick degradability upon exposure. To overcome these challenges, we formulated lemon oil loaded nanoemulsion system (LO-NE) (oil-in-water), using aqueous titration method. The formulation comprised of lemon oil (LO), Tween 80 and ethanol as oil, surfactant and co-surfactant phases respectively. The existence zone of NE was established by constructing pseudo-ternary phase diagrams using different concentrations of LO, surfactant and co-surfactant (S<sub>mix</sub>). The quantitative estimation of LO was performed using a high throughput gas chromatography, revealing the presence of various compounds like Limonene, Alpha-Pinene and Linalyl acetate followed by the estimation of total phenolics and flavonoid content. The characterization of LO-NE indicated the particle size of 60 ± 2.5 nm along with the polydispersity index of 0.125 and zeta potential of <span style="white-space:nowrap;">−</span>14.9 mV. The size range of the NE particles dispersed in the colloidal system was further verified by TEM micrograph which shows size range between 46.2 - 104.7 nm. All the anti-oxidant assays outcomes exhibited the higher activity of LO-NE in comparison to LO alone with lower IC<sub>50</sub> values. The release kinetics statistical data showed that LO-NE had a sustained release and followed the Higuchi’s model in comparison to burst release of LO alone. Lastly, the stability analysis of the optimised formulation (LO-NE) and LO was estimated through antioxidant assay and subjecting them for thermodynamic stability after 6 months. The results attained, showed higher stability and anti-oxidant capability of LO-NE than LO alone. The study suggested that formulated nanoemulsion can be effectively used as a highly efficacious biologically active alternative nanoformulation against many transdermal disorders.展开更多
The thermodynamic phase stability area diagrams of BCl3-NH3-Si Cl4-H2-Ar system were plotted via Factsage software to predict the kinetic experimental results. The effects of parameters(i e, partial pressure of reacta...The thermodynamic phase stability area diagrams of BCl3-NH3-Si Cl4-H2-Ar system were plotted via Factsage software to predict the kinetic experimental results. The effects of parameters(i e, partial pressure of reactants, deposition temperature and total pressure) on the distribution regions of solid phase products were analyzed based on the diagrams. The results show that:(a) Solid phase products are mainly affected by deposition temperature. The area of BN+Si3N4 phase increases with the temperature rising from 650 to 900 ℃, and decreases with the temperature rising from 900 to 1 200 ℃;(b) When temperature and total pressure are constants, BN+Si3N4 phase exists at a high partial pressure of NH3;(c) The effect of total system pressure is correlated to deposition temperature. The temperature ranging from 700 to 900 ℃ under low total pressure is the optimum condition for the deposition.(d) Appropriate kinetic parameters can be determined based on the results of thermodynamic calculation. Si–B–N coating is obtained via low pressure chemical vapor deposition. The analysis by X-ray photoelectron spectroscopy indicates that B–N and Si–N are the main chemical bonds of the coating.展开更多
Achieving room-temperature superconductivity has been an enduring scientific quest,while hydrogen-rich compounds have emerged as highly promising candidates.Here,we systematically investigated the thermodynamic stabil...Achieving room-temperature superconductivity has been an enduring scientific quest,while hydrogen-rich compounds have emerged as highly promising candidates.Here,we systematically investigated the thermodynamic stability,crystal structure,electronic properties,and superconductivity within the ternary Y-Hf-H system under high pressure.Several distinct hydrides have been revealed,in which the hydrogen atoms are present in various hydrogenic motifs.A15-type hydride P_(m)3-YHfH_(6)with isolated H−is predicted to be dynamically stabilized down to 10GPa.The H atoms form pentagonal graphene-like layered-H10 anions in the Hf plane of P6-YHfH_(19),with aT_(c)of 95K at 100GPa.There are H cages in C_(mmm)-Y_(3)HfH_(24),and attributed to the robust electron–phonon coupling and high electronic density of states of hydrogen at the Fermi level,it demonstrates near-room temperature superconductivity with a T_(c)of 275K at 250GPa.Our work makes contributions to the understanding of the fundamental properties of ternary hydrides under high pressure and provides essential references for further research in this field.展开更多
Crystal structure prediction aims to predict stable and easily experimentally synthesized materials,which accelerates the discovery of new materials.It is worth noting that the stability of materials is the basis for ...Crystal structure prediction aims to predict stable and easily experimentally synthesized materials,which accelerates the discovery of new materials.It is worth noting that the stability of materials is the basis for ensuring high performance and reliable application of materials.Among which,the thermodynamic and molecular dynamics stability is especially important.Therefore,this paper proposes a method to predict stable crystal structures using formation energy and Lennard-Jones potential as evaluation indicators.Specifically,we use graph neural network models to predict the formation energy of crystals,and employ empirical formulas to calculate the Lennard-Jones potential.Then,we apply Bayesian optimization algorithms to search for crystal structures with low formation energy and Lennard-Jones potential approaching zero,in order to ensure the thermodynamic stability and dynamics stability of materials.In addition,considering the impact of the bonding situation between atoms in the crystal on the structural stability,this article uses contact map to analyze the atomic bonding situation of each crystal to screen out more stable materials.Finally,the experimental results show that the method we proposed can not only reduce the time for crystal structure prediction,but also ensure the stability of crystal materials.展开更多
In this study,the thermal behaviors of pure Ni and Pd as well as Ni@Pd,and Pd@Ni hollow nanoclusters were investigated by MD simulations.The Ni@Pd hollow nanoclusters exhibited more thermodynamic stability and a highe...In this study,the thermal behaviors of pure Ni and Pd as well as Ni@Pd,and Pd@Ni hollow nanoclusters were investigated by MD simulations.The Ni@Pd hollow nanoclusters exhibited more thermodynamic stability and a higher melting point than the Pd@Ni ones.This result is opposite to the trend demonstrated by the corresponding bulk materials,which could be related to the effect of the hollow core.Due to the small difference between the melting points of bulk Pd and Ni,a two-step melting behavior was not observed for the hollow Pd–Ni nanoclusters.The differences between the thermodynamic stabilities of the simulated nanoclusters were related to the concentration of Pd atoms in the shell and Ni atoms in the core regions due to the lower surface energy of Pd atoms and the higher cohesive and binding energy of Ni atoms.Also,a larger nanocluster size led to a faster diffusion of Pd atoms toward the shell of the nanocluster.Moreover,the diffusion of Pd atoms to the surface and Ni atoms to the core region for Pd@Ni nanoclusters near the melting point and the increase in the ordered atoms under these circumstances led to a higher melting point of this nanocluster in comparison with the Ni@Pd nanoclusters.These results indicate the potential for the future construction of nanocatalysts based on bimetallic nanoclusters with core–shell hollow structures.展开更多
Insufficient chemical stability of numerous metal-organic frameworks(MOFs)restricts their widespread use.Achieving high thermodynamic stability is not a universal method to obtain chemically stable MOFs because kineti...Insufficient chemical stability of numerous metal-organic frameworks(MOFs)restricts their widespread use.Achieving high thermodynamic stability is not a universal method to obtain chemically stable MOFs because kinetic stability also has a significant effect.Here,in contrast to a hydrogen bond between two adjacent ligands in MOFs needing rational framework structures,an intramolecular hydrogen bond in ligands was engineered to enhance the chemical stability of MOFs.As a proof-of-concept demonstration,3,3’-diamino-1,1’-biphenyl-4,4’-dicarboxylic acid(H_(2)BPDC-o-(NH_(2))2)with the intramolecular hydrogen bonds and 2,2’-diamino-1,1’-biphenyl-4,4’-dicarboxylic acid(H_(2)BPDC-m-(NH_(2))2)without the intramolecular hydrogen bonds were synthesized to construct UiO-67-o-(NH_(2))_(2) and UiO-67-m-(NH_(2))_(2),respectively.Intramolecular hydrogen bonds were found to increase the torsional rigidity of carboxyl groups relative to the adjacent aromatic rings in ligands and to favour the repair of broken coordination bonds of MOFs.Consequently,UiO-67-o-(NH_(2))_(2) is more chemically stable than UiO-67-m-(NH_(2))_(2) in H_(2)O,pH=2 HCl solution,and pH=12 NaOH solution.This work not only provides an insight into the contribution of intramolecular hydrogen bonds in ligands to the stability of MOFs but provides a strategy to design highly stable MOFs for widespread use.展开更多
Aromatic fractions of 140 oils and condensates that originated from different types of source rocks （marine shale,terrestrial shale and marine carbonate） were analyzed using gas chromatographymass spectrometry （GC...Aromatic fractions of 140 oils and condensates that originated from different types of source rocks （marine shale,terrestrial shale and marine carbonate） were analyzed using gas chromatographymass spectrometry （GC-MS） to investigate the relative distributions of methylated dibenzothiophenes with respect to thermal maturity.The positions of methyl groups of trimethyldibenzothiophene isomers （TMDBTs） including those used in the definition of maturity indicator TMDBT index in previous studies were firmly identified by co-elution of internal standards in GC-MS analysis and by comparing with reported retention indices.A new maturity ratio related to dimethyldibenzothiophenes （DMDBTs） is proposed on the basis of the differences in thermodynamic stability among different DMDBT isomers.Another maturity index （TMDBT-I2） based on TMDBTs is also suggested on the basis of our empirical observations and presumed thermodynamic stability of TMDBT isomers.These two newly proposed （2,6 ＋ 3,6）-/1,4-DMDBT ratio and TMDBT-I2 correlate well with MDR （4-/1-methyldibenzothiophene）and 2,4-/1,4-DMDBT ratios,suggesting their common chemical reaction mechanisms and similar behavior with increasing maturity.Therefore,they can be effectively applied for maturity assessments.Furthermore,the TMDBTs related maturity parameters are more reliable for over-mature oils and condensates due to the relatively higher concentrations of thermodynamically unstable TMDBT isomers,i.e.1,4,6-,1,4,8-and 3,4,6-TMDBT in this study than those of 1-methyldibenzothiophene （1-MDBT） or 1,4-DMDBT.In contrast with 4,6-/1,4-DMDBT,the newly proposed （2,6 ＋ 3,6）-/1,4-DMDBT ratios for oils that originated from different types of source rocks have approximately same relationship with the oil maturity （Rc %）.This suggests that the lithology and organic facies may have relatively less influence on （2,6 ＋ 3,6）-/1,4-DMDBT ratio compared to 4,6-/1,4-DMDBT.The maturity parameters based on methylated dibenzothiophenes are particularly useful in the maturity assessments of post-and over-mature oils and condensates and can complement maturity indicators based on steranes and terpanes.展开更多
Phase equilibria involving the long-period stacking ordered phases including 14 H,18 R and 10 H in the Mg-rich corner of the Mg-Y-Zn system at 400 and 500℃ have been experimentally investigated by using X-ray diffrac...Phase equilibria involving the long-period stacking ordered phases including 14 H,18 R and 10 H in the Mg-rich corner of the Mg-Y-Zn system at 400 and 500℃ have been experimentally investigated by using X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).The coexistence of 14 H and 18 R as well as 18 R and 10 H was confirmed from atomic scales.The phases 14 H,18 R and 10 H were all stable phases from 400 to 500℃.The experimentally proved three-phase equilibrium of14 H,18 R and α-Mg instead of 14 H,18 R and Mg_(24)Y_(5) were presented in the modified isothermal sections.The latter three-phase equilibrium was reported in the available literature.The modified isothe rmal sections are conducive to guide the composition design to obtain the alloys with favorable microstructure constituents and mechanical properties.展开更多
In the development process of crossover aluminum alloys,T-Mg_(32)(Al,Zn)_(49)phases play a significant role in the precipitation strengthening effect.However,comprehensive understandings of the structural characterist...In the development process of crossover aluminum alloys,T-Mg_(32)(Al,Zn)_(49)phases play a significant role in the precipitation strengthening effect.However,comprehensive understandings of the structural characteristics,interactions among alloying elements,mechanical property dependence on composition variation,effects of doping and defects etc.are still inadequate.A combination of density functional theory(DFT)calculations and special quasi-random structures(SQSs)was applied to investigate the formation energies,lattice parameters,electronic structures and mechanical properties of the disordered T-phases,as well as the effects of possible defects and alloying elements.The formation energy and lattice constant of the T-phase gradually vary from 0 to-0.12 eV/atom and from 1.460 to 1.405 nm,respectively,with increasing Zn contents.Zn-3d orbitals exhibit stronger hybridization with Al-3s than Mg-3s orbitals,and this is further enhanced by increasing Zn contents,leading to improved covalency and mechanical properties of the T-phase.The T-phases show good ductility according to the Poisson's ratio ν,Cauchy's pressure and G/B.The A site is more favorable to remain vacant in Al-rich and Zn-poor environments,which is consistent with the previous experimental observations.For alloying elements,Zn atoms tends to occupy Al atoms at the B,C and F sites and Mg atoms at the G sites.Both Cu and Ag elements can decrease the formation energy of T-phases and possibly produce a greater number of T-phases during the precipitation process.The effect of Ag is more significant relative to Cu due to the deeper orbital hybridization.The computational results show good agreement with previous experimental data and provide new insights into the compositional design of new Al-Mg-Zn alloys.展开更多
文摘The cryo-fracture electron microscope was used to study the micro-structure of pesticide mi-croemulsions. The hydromechanical radius (Rh) and the distribution (fRh) of pesticide microemulsions were determined by photo-correlation spectroscopy. This study showed that the Rh was significantly greater when the ratio of surfactants to water (w/w) decreased to 20/31 from 27/26, and a bicontinuous structure was formed when the ratio dropped to 15/36. These results explained the relationship between pesticide properties and the microscopic structure, and provided a good method for studying the microscopic structure of pesticide formulations.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51871143 and 11972219)the Science and Technology Committee of Shanghai(No.19010500400)+1 种基金Shanghai Rising-Star Program(No.21QA1403200)the Independent Research Project of State Key Laboratory of Mechanical Transmissions of China(No.SKLMT-ZZKT-2021M11).
文摘The quasicrystal phase is beneficial to increasing the strength of magnesium alloys.However,its complicated structure and unclear phase relations impede the design of alloys with good mechanical properties.In this paper,the Mg_(40)Zn_(55)Nd_(5) icosahedral quasicrystal(I-phase)structure is discovered in an as-cast Mg-58Zn-4Nd alloy by atomic resolution high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).A cloud-like morphology is observed with Mg_(41.6)Zn_(55.0)Nd_(3.4) composition.The selected area electronic diffrac-tion(SAED)analysis shows that the icosahedral quasicrystal structure has 5-fold,4-fold,3-fold,and 2-fold symmetry zone axes.The thermo-dynamic stability of the icosahedral quasicrystal is investigated by differential scanning calorimetry(DSC)in the annealed alloys.When an-nealed above 300℃,the Mg_(40)Zn_(55)Nd_(5) quasicrystal is found to decompose into a stable ternary phase Mg_(35)Zn_(60)Nd_(5),a binary phase MgZn,andα-Mg,suggesting that the quasicrystal is a metastable phase in the Mg-Zn-Nd system.
文摘The electronic and optical characteristics of the Sc2 CoSi Heusler with L21 structure and also the surface effect on electronic and optical properties, and the ?lms thermodynamic stability of the [001] direction in four cases including:Sc-Sc, Sc-Co, Sc-Si and Co-Si terminations are studied using the ?rst principles calculations(FPLAPW) within the framework of the density functional theory(DFT). The band structure calculations represent the ferromagnetic halfmetallic properties with 100% spin polarization and 0.54 e V indirect gap in spin down for Sc2 CoSi bulk with optimized lattice parameters of 6.25 A?. The total magnetic moment obtained for this compound is-1.0 μB, which is in accordance with Slater-Pauling rule. The half-metallic(HM) behavior by 100% spin polarization at Fermi level is occurred in the Sc-Si termination with a 0.32 eV gap in down spin. The optical responses have been calculated for the bulk and ScSi termination by a red shift in these parameters and the metallic treatments have been increased. According to the thermodynamic phase diagrams, it is shown the Sc-Si and Sc-Sc terminations are more stable than other terminations.
基金Project supported by the Scientific Starting Research Fund of Central China Normal University of Chinathe National Natural Science Foundation of China (Grant Nos 10675052 and 10875050)Ministry of Education of China (Grant No IRT0624)
文摘A matrix eigenvalue method is applied to analyse the thermodynamic stability of two-component interacting fermions. The non-relativistic and ultra-relativistic d = 1, 2, 3 dimensions have been discussed in detail, respectively. The corresponding stability region has been given according to the two-body interaction strength and the particle number density ratio.
基金supported by the National Natural Science Foundation of China (No.20771083)
文摘A new Co（Ⅲ） complex with a tripodal amide ligand [CoL（N3）3] （L = N-acetyl- N＇,N＇-bis-[（2-pyridyl）methyl]-ethylenediamine） has been synthesized and characterized structurally by X-ray diffraction. It crystallizes in orthorhombic, space group Pnma with a = 9.2515（19）, b = 12.729（3）, c = 17.273（4） A, V = 2034.0（7） A3, C16H20CoN13O, Mr = 469.38, Dc = 1.533 g/cm3, μ（MoKα） = 0.884 mm^-1, F（000） = 968, Z = 4, the final R = 0.0392 and wR = 0.0818 for 2430 observed reflections. In the complex, the amide ligand L acts as a tridentate fashion and coordinates to the Co（Ⅲ） ion through three nitrogen atoms, while the other three positions of the Co（Ⅲ） center are occupied by three terminal azide anions. The complex is connected as a 1D chain structure by intermolecular hydrogen bonds between the uncoordinated amide groups. In order to investigate the coordination ability, thermodynamic stability of the ligand L with the first-series transition metal ions （Co（Ⅱ）, Ni（Ⅱ）, Cu（Ⅱ） and Zn（Ⅱ）） has been studied by potentiometric titration, and the results show that the order of their stability constants conforms to the Irving-Williams sequence.
文摘Thermal denaturation and stability of two commercially available preparations of Human Serum Albumin (HSA), differing in their advertised level of purity, were investigated by differential scanning calorimetry (DSC). These protein samples were 99% pure HSA (termed HSA<sub>99</sub>) and 96% pure HSA (termed HSA<sub>96</sub>). According to the supplier, the 3% difference in purity between HSA<sub>96</sub> and HSA<sub>99</sub> is primarily attributed to the presence of globulins and fatty acids. Our primary aim was to investigate the utility of DSC in discerning changes in HSA that occur when the protein is specifically adducted, and determine how adduct formation manifests itself in HSA denaturation curves, or thermograms, measured by DSC. Effects of site specific covalent attachment of biotin (the adduct) on the thermodynamic stability of HSA were investigated. Each of the HSA preparations was modified by biotinylation targeting a single site, or multiple sites on the protein structure. Thermograms of both modified and unmodified HSA samples successfully demonstrated the ability of DSC to clearly discern the two HSA preparations and the presence or absence of covalent modifications. DSC thermogram analysis also provided thermodynamic characterization of the different HSA samples of the study, which provided insight into how the two forms of HSA respond to covalent modification with biotin. Consistent with published studies [1] HSA<sub>96</sub>, the preparation with contaminants that contain globulins and fatty acids seems to be comprised of two forms, HSA<sub>96-L</sub> and HSA<sub>96-H</sub>, with HSA<sub>96-L</sub> more stable than HSA<sub>99</sub>. The effect of multisite biotinylation is to stabilize HSA<sub>96-L</sub> and destabilize HSA<sub>96-H</sub>. Thermodynamic analysis suggests that the binding of ligands comprising the fatty acid and globulin-like contaminant contributes approximately 6.7 kcal/mol to the stability HSA<sub>96-L</sub>.
基金supported by the National Natural Science Foundation of China(Grant Nos.12004131,and 22090044)the Jilin Province Science and Technology Development Program(Grant No.20210508044RQ)。
文摘Alloying strategies provide a high degree of freedom for reducing lead toxicity,improving thermodynamic stability, tuning the optoelectronic properties of ABX3 halide perovskites by varying the alloying element species and their contents.Given the key role of B-site cations in contributing band edge states and modulating structure factors in halide perovskites,the partial replacement of Pb2+with different B-site metal ions has been proposed.Although several experimental attempts have been made to date,the effect of B-site alloying on the stability and electronic properties of halide perovskites has not been fully explored.Herein,we take cubic CsPbBr3 perovskite as the prototype material and systematically explore the effects of B-site alloying on Pb-containing perovskites.According to the presence or absence of the corresponding perovskite phase,the ten alloying elements investigated are classified into three types(i.e.,Type Ⅰ:Sn Ge,Ca,Sr;Type Ⅱ:Cd,Mg,Mn;Type Ⅲ:Ba,Zn,Cu).Based on the first-principles calculations,we obtain the following conclusions.First,these B-site alloys will exist as disordered solid solutions rather than ordered structures at room temperature throughout the composition space.Second,the alloying of Sn and Ge enhances the thermodynamic stability of the cubic perovskite host,whereas the alloying of the other elements has no remarkable effect on the thermodynamic stability of the cubic perovskite host.Third,the underlying physical mechanism for bandgap tuning can be attributed to the atomic orbital energy mismatch or quantum confinement effect.Fourth,the alloying of different elements demonstrates the diversity in the regulation of crystal structure and electronic properties,indicating potential applications in photovoltaic s and self-trapped exciton-based light-emitting applications.Our work provides theoretical guidance for using alloying strategies to reduce lead toxicity,enhance stability,and optimize the electronic properties of halide perovskites to meet the needs of optoelectronic applications.
基金This work was supported by the Natural Sciences and Engineering Research Council of Canada(NSERC).
文摘We present here a thermodynamic assessment of the stability behavior in acid environment at 298 and 353 K(80◦C)of two iron(II)hexa-aza-macrocyclic complexes and of an hexa-aza-iron-based site(Fe^(II)N_((4+2))/C)that should potentially be active for the oxygen reduction reaction in proton exchange membrane(PEM)fuel cells.The calculations of the equilibrium constant(K c)for the demetallation reaction indicate that the iron(II)-hexa-aza-macrocyclic complexes and Fe^(II)N_((4+2))/C are chemically stable in an acid medium at 298 and 353 K.Compared with two other potential model sites(Fe^(II)N_((4+2))/C and Fe II N(2+2)/C)that were thought to be present in the same Fe-based catalysts,K c of Fe^(II)N_((4+2))/C is two to three orders of magnitude smaller at 353 K,and three to four orders of magnitude smaller at 298 K,than K c for Fe^(II)N_((4+2))/C or Fe II N(2+2)/C,revealing the great chemical stability of Fe^(II)N_((4+2))/C.In this work,we discuss about a novel proposition that the two catalytic sites active in these Fe-based catalysts are Fe II N_(4)/C and Fe^(II)N_((4+2))/C.This proposition is in agreement with the durability behavior of these catalysts in PEM fuel cells and also with their known physico-chemical characterizations.The origin of the fast and slow decay behaviors of the different sites,which are active at the Fe–N–C-based cathode of PEM fuel cells,is also discussed.
文摘A series of thermodynamic parameters in formation of ultrafine monodispersed colloidal particles of Y(OH)CO3 were measured, estimated and calculated. The thermodynamic stability of Y(OH)CO3 colloidal particles was studied and discussed by phenomenological model. It is suggested that ultrafine monodispersed colloidal particles of Y(OH)CO3 are stable only in a very narrow temporary supersaturation range ( 1<x<1 .08).
基金financial support from the Guangdong Provincial Quantum Science Strategic Initiative (Grant No.GDZX2501011)the Guangdong Basic and Applied Basic Research Foundation (Grant No.2024A1515010484)+7 种基金the financial support from the Guangdong Basic and Applied Basic Research Foundation (Grant No.2022A1515110404)the Guangdong Basic and Applied Basic Research Foundation (Grant No.2023A1515140188)the Guangdong Basic and Applied Basic Research Foundation (Grant No.2022A1515110322)the National Natural Science Foundation of China (Grant Nos.U2330104 and 12574028)financial support from the National Natural Science Foundation of China (Grant No.12304095)support from the National Natural Science Foundation of China (Grant No.12404190)the financial support from the National Key R&D Program of China (Grant No.2022YFA1403103)the China Postdoctoral Science Foundation (Grant No.2024M762275)。
文摘Kagome materials host intertwined phenomena,including nontrivial band topology,superconductivity,and complex charge-density-wave order,making them an important platform in condensed-matter physics and materials science.Motivated by extensive studies on the AV_(3)Sb_(5) family of materials,we perform high-throughput first-principles calculations to screen bilayer kagome AM_(6)X_(6) compounds with an MgFe_(6)Ge_(6)-prototype structure as potential weak-coupling superconductors.Thereafter,we systematically evaluate the thermodynamic,dynamic,and magnetic stabilities,followed by electron–phonon coupling(EPC)calculations and superconducting transition temperature estimates based on the Allen–Dynes-modified McMillan equation.From 168 candidates,we identify 31 weak-coupling superconductors that satisfy both the thermodynamic and dynamical stability criteria in our screening workflow.Focusing on compounds without partially filled f shells,we obtain superconducting transition temperatures(T_(c))of 0.65–3.97 K with EPC constants λ=0.37–0.62,indicating conventional weak-coupling superconductivity.The EPC is typically driven by vibrations within the kagome layers,with Sn-containing materials exhibiting low-frequency soft modes that contribute significantly to λ.By providing a global mapping of stability and weak-coupling superconductivity in bilayer kagome AM_(6)X_(6) compounds,this study offers a practical theoretical database and design principles for future experimental exploration.
文摘Lemon oil (LO), also known as <em>Citrus limonum</em> is a highly volatile essential oil (EO) with potential therapeutic properties like anti-oxidative, anti-proliferative, anti-fungal and anti-cancerous. However, the efficacy of LO is limited due to its physiological factors such as high volatility, poor stability (particularly sensitive to sunlight) and quick degradability upon exposure. To overcome these challenges, we formulated lemon oil loaded nanoemulsion system (LO-NE) (oil-in-water), using aqueous titration method. The formulation comprised of lemon oil (LO), Tween 80 and ethanol as oil, surfactant and co-surfactant phases respectively. The existence zone of NE was established by constructing pseudo-ternary phase diagrams using different concentrations of LO, surfactant and co-surfactant (S<sub>mix</sub>). The quantitative estimation of LO was performed using a high throughput gas chromatography, revealing the presence of various compounds like Limonene, Alpha-Pinene and Linalyl acetate followed by the estimation of total phenolics and flavonoid content. The characterization of LO-NE indicated the particle size of 60 ± 2.5 nm along with the polydispersity index of 0.125 and zeta potential of <span style="white-space:nowrap;">−</span>14.9 mV. The size range of the NE particles dispersed in the colloidal system was further verified by TEM micrograph which shows size range between 46.2 - 104.7 nm. All the anti-oxidant assays outcomes exhibited the higher activity of LO-NE in comparison to LO alone with lower IC<sub>50</sub> values. The release kinetics statistical data showed that LO-NE had a sustained release and followed the Higuchi’s model in comparison to burst release of LO alone. Lastly, the stability analysis of the optimised formulation (LO-NE) and LO was estimated through antioxidant assay and subjecting them for thermodynamic stability after 6 months. The results attained, showed higher stability and anti-oxidant capability of LO-NE than LO alone. The study suggested that formulated nanoemulsion can be effectively used as a highly efficacious biologically active alternative nanoformulation against many transdermal disorders.
基金Funded by the National Natural Science Foundation of China(Nos.51002120,51472201)
文摘The thermodynamic phase stability area diagrams of BCl3-NH3-Si Cl4-H2-Ar system were plotted via Factsage software to predict the kinetic experimental results. The effects of parameters(i e, partial pressure of reactants, deposition temperature and total pressure) on the distribution regions of solid phase products were analyzed based on the diagrams. The results show that:(a) Solid phase products are mainly affected by deposition temperature. The area of BN+Si3N4 phase increases with the temperature rising from 650 to 900 ℃, and decreases with the temperature rising from 900 to 1 200 ℃;(b) When temperature and total pressure are constants, BN+Si3N4 phase exists at a high partial pressure of NH3;(c) The effect of total system pressure is correlated to deposition temperature. The temperature ranging from 700 to 900 ℃ under low total pressure is the optimum condition for the deposition.(d) Appropriate kinetic parameters can be determined based on the results of thermodynamic calculation. Si–B–N coating is obtained via low pressure chemical vapor deposition. The analysis by X-ray photoelectron spectroscopy indicates that B–N and Si–N are the main chemical bonds of the coating.
基金supported by the National Natural Science Foundation of China(Grant Nos.52072188,12122405,and 12274169)Program for Science and Technology Innovation Team in Zhejiang Province,China(Grant No.2021R01004)+2 种基金Natural Science Foundation of Zhejiang Province,China(Grant No.LQ24A040001)the Natural Science Foundation of Ningbo City,China(Grant No.2024J200)the Fundamental Research Funds for the Provincial Universities of Zhejiang(Grant No.SJLY2023003)。
文摘Achieving room-temperature superconductivity has been an enduring scientific quest,while hydrogen-rich compounds have emerged as highly promising candidates.Here,we systematically investigated the thermodynamic stability,crystal structure,electronic properties,and superconductivity within the ternary Y-Hf-H system under high pressure.Several distinct hydrides have been revealed,in which the hydrogen atoms are present in various hydrogenic motifs.A15-type hydride P_(m)3-YHfH_(6)with isolated H−is predicted to be dynamically stabilized down to 10GPa.The H atoms form pentagonal graphene-like layered-H10 anions in the Hf plane of P6-YHfH_(19),with aT_(c)of 95K at 100GPa.There are H cages in C_(mmm)-Y_(3)HfH_(24),and attributed to the robust electron–phonon coupling and high electronic density of states of hydrogen at the Fermi level,it demonstrates near-room temperature superconductivity with a T_(c)of 275K at 250GPa.Our work makes contributions to the understanding of the fundamental properties of ternary hydrides under high pressure and provides essential references for further research in this field.
基金supported by the Nature Science Foundation of China(Nos.61671362 and 62071366)。
文摘Crystal structure prediction aims to predict stable and easily experimentally synthesized materials,which accelerates the discovery of new materials.It is worth noting that the stability of materials is the basis for ensuring high performance and reliable application of materials.Among which,the thermodynamic and molecular dynamics stability is especially important.Therefore,this paper proposes a method to predict stable crystal structures using formation energy and Lennard-Jones potential as evaluation indicators.Specifically,we use graph neural network models to predict the formation energy of crystals,and employ empirical formulas to calculate the Lennard-Jones potential.Then,we apply Bayesian optimization algorithms to search for crystal structures with low formation energy and Lennard-Jones potential approaching zero,in order to ensure the thermodynamic stability and dynamics stability of materials.In addition,considering the impact of the bonding situation between atoms in the crystal on the structural stability,this article uses contact map to analyze the atomic bonding situation of each crystal to screen out more stable materials.Finally,the experimental results show that the method we proposed can not only reduce the time for crystal structure prediction,but also ensure the stability of crystal materials.
文摘In this study,the thermal behaviors of pure Ni and Pd as well as Ni@Pd,and Pd@Ni hollow nanoclusters were investigated by MD simulations.The Ni@Pd hollow nanoclusters exhibited more thermodynamic stability and a higher melting point than the Pd@Ni ones.This result is opposite to the trend demonstrated by the corresponding bulk materials,which could be related to the effect of the hollow core.Due to the small difference between the melting points of bulk Pd and Ni,a two-step melting behavior was not observed for the hollow Pd–Ni nanoclusters.The differences between the thermodynamic stabilities of the simulated nanoclusters were related to the concentration of Pd atoms in the shell and Ni atoms in the core regions due to the lower surface energy of Pd atoms and the higher cohesive and binding energy of Ni atoms.Also,a larger nanocluster size led to a faster diffusion of Pd atoms toward the shell of the nanocluster.Moreover,the diffusion of Pd atoms to the surface and Ni atoms to the core region for Pd@Ni nanoclusters near the melting point and the increase in the ordered atoms under these circumstances led to a higher melting point of this nanocluster in comparison with the Ni@Pd nanoclusters.These results indicate the potential for the future construction of nanocatalysts based on bimetallic nanoclusters with core–shell hollow structures.
基金supported by the National Natural Science Foundation of China(21808201,21776259,21706233,21978272,21808204,21878275,21905248).
文摘Insufficient chemical stability of numerous metal-organic frameworks(MOFs)restricts their widespread use.Achieving high thermodynamic stability is not a universal method to obtain chemically stable MOFs because kinetic stability also has a significant effect.Here,in contrast to a hydrogen bond between two adjacent ligands in MOFs needing rational framework structures,an intramolecular hydrogen bond in ligands was engineered to enhance the chemical stability of MOFs.As a proof-of-concept demonstration,3,3’-diamino-1,1’-biphenyl-4,4’-dicarboxylic acid(H_(2)BPDC-o-(NH_(2))2)with the intramolecular hydrogen bonds and 2,2’-diamino-1,1’-biphenyl-4,4’-dicarboxylic acid(H_(2)BPDC-m-(NH_(2))2)without the intramolecular hydrogen bonds were synthesized to construct UiO-67-o-(NH_(2))_(2) and UiO-67-m-(NH_(2))_(2),respectively.Intramolecular hydrogen bonds were found to increase the torsional rigidity of carboxyl groups relative to the adjacent aromatic rings in ligands and to favour the repair of broken coordination bonds of MOFs.Consequently,UiO-67-o-(NH_(2))_(2) is more chemically stable than UiO-67-m-(NH_(2))_(2) in H_(2)O,pH=2 HCl solution,and pH=12 NaOH solution.This work not only provides an insight into the contribution of intramolecular hydrogen bonds in ligands to the stability of MOFs but provides a strategy to design highly stable MOFs for widespread use.
基金funded by the National Natural Science Foundation of China (Grant No. 41272158)the State Key Laboratory of Petroleum Resources and Prospecting (PRP/indep-2-1302)
文摘Aromatic fractions of 140 oils and condensates that originated from different types of source rocks （marine shale,terrestrial shale and marine carbonate） were analyzed using gas chromatographymass spectrometry （GC-MS） to investigate the relative distributions of methylated dibenzothiophenes with respect to thermal maturity.The positions of methyl groups of trimethyldibenzothiophene isomers （TMDBTs） including those used in the definition of maturity indicator TMDBT index in previous studies were firmly identified by co-elution of internal standards in GC-MS analysis and by comparing with reported retention indices.A new maturity ratio related to dimethyldibenzothiophenes （DMDBTs） is proposed on the basis of the differences in thermodynamic stability among different DMDBT isomers.Another maturity index （TMDBT-I2） based on TMDBTs is also suggested on the basis of our empirical observations and presumed thermodynamic stability of TMDBT isomers.These two newly proposed （2,6 ＋ 3,6）-/1,4-DMDBT ratio and TMDBT-I2 correlate well with MDR （4-/1-methyldibenzothiophene）and 2,4-/1,4-DMDBT ratios,suggesting their common chemical reaction mechanisms and similar behavior with increasing maturity.Therefore,they can be effectively applied for maturity assessments.Furthermore,the TMDBTs related maturity parameters are more reliable for over-mature oils and condensates due to the relatively higher concentrations of thermodynamically unstable TMDBT isomers,i.e.1,4,6-,1,4,8-and 3,4,6-TMDBT in this study than those of 1-methyldibenzothiophene （1-MDBT） or 1,4-DMDBT.In contrast with 4,6-/1,4-DMDBT,the newly proposed （2,6 ＋ 3,6）-/1,4-DMDBT ratios for oils that originated from different types of source rocks have approximately same relationship with the oil maturity （Rc %）.This suggests that the lithology and organic facies may have relatively less influence on （2,6 ＋ 3,6）-/1,4-DMDBT ratio compared to 4,6-/1,4-DMDBT.The maturity parameters based on methylated dibenzothiophenes are particularly useful in the maturity assessments of post-and over-mature oils and condensates and can complement maturity indicators based on steranes and terpanes.
基金National Key Research and Development Program of China (No.2016YFB0701201)the National Natural Science Foundation of China (No.51571019) for the financial supports。
文摘Phase equilibria involving the long-period stacking ordered phases including 14 H,18 R and 10 H in the Mg-rich corner of the Mg-Y-Zn system at 400 and 500℃ have been experimentally investigated by using X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).The coexistence of 14 H and 18 R as well as 18 R and 10 H was confirmed from atomic scales.The phases 14 H,18 R and 10 H were all stable phases from 400 to 500℃.The experimentally proved three-phase equilibrium of14 H,18 R and α-Mg instead of 14 H,18 R and Mg_(24)Y_(5) were presented in the modified isothermal sections.The latter three-phase equilibrium was reported in the available literature.The modified isothe rmal sections are conducive to guide the composition design to obtain the alloys with favorable microstructure constituents and mechanical properties.
基金financially supported by the National Key R&D Program of China(No.2020YFF0218200)the Innovation Fund Project of GRINM,and other related projects.
文摘In the development process of crossover aluminum alloys,T-Mg_(32)(Al,Zn)_(49)phases play a significant role in the precipitation strengthening effect.However,comprehensive understandings of the structural characteristics,interactions among alloying elements,mechanical property dependence on composition variation,effects of doping and defects etc.are still inadequate.A combination of density functional theory(DFT)calculations and special quasi-random structures(SQSs)was applied to investigate the formation energies,lattice parameters,electronic structures and mechanical properties of the disordered T-phases,as well as the effects of possible defects and alloying elements.The formation energy and lattice constant of the T-phase gradually vary from 0 to-0.12 eV/atom and from 1.460 to 1.405 nm,respectively,with increasing Zn contents.Zn-3d orbitals exhibit stronger hybridization with Al-3s than Mg-3s orbitals,and this is further enhanced by increasing Zn contents,leading to improved covalency and mechanical properties of the T-phase.The T-phases show good ductility according to the Poisson's ratio ν,Cauchy's pressure and G/B.The A site is more favorable to remain vacant in Al-rich and Zn-poor environments,which is consistent with the previous experimental observations.For alloying elements,Zn atoms tends to occupy Al atoms at the B,C and F sites and Mg atoms at the G sites.Both Cu and Ag elements can decrease the formation energy of T-phases and possibly produce a greater number of T-phases during the precipitation process.The effect of Ag is more significant relative to Cu due to the deeper orbital hybridization.The computational results show good agreement with previous experimental data and provide new insights into the compositional design of new Al-Mg-Zn alloys.
