Phase Thermodynamic Properties Research Articles

Key phase diagram experiments and thermodynamic modeling of the ZnO‒B2O3, ZnO‒SiO2, and ZnO‒B2O3‒SiO2 systems

AbstractThermodynamic modeling of binary ZnO‒B2O3 and ZnO‒SiO2 systems and ternary ZnO‒B2O3‒SiO2 system were carried out based on the critical evaluation and optimization of all available phase diagram and thermodynamic property data using the CALculation of PHAse Diagram (CALPHAD) method. To resolve the inconsistency among the available phase diagram data in ternary ZnO‒B2O3‒SiO2 system, key phase diagram experiment was carried out using classical quenching method followed by electron probe micro‐analysis and X‐ray diffraction phase determination. The liquid oxide solution was described using the modified quasichemical model accounting for a short‐range ordering behavior in molten oxide solution. Thermodynamic models with optimized model parameters were used to predict the phase diagram and thermodynamic properties of the ternary systems.

First Principles Calculation of the Influence of Alloying on the Phase Stability, Elasticity, and Thermodynamic Properties of the MoNbTiVX (X = Al/Cr) Refractory High-Entropy Alloy

In response to the poor wear resistance and high-temperature oxidation resistance of titanium alloys during service, a series of lightweight refractory high-entropy alloys (RHEAs) can be designed for the laser cladding coating of titanium alloy surfaces, with due consideration of the compositional and structural characteristics of titanium alloys. Firstly, the structural stability, mechanical and thermal properties of four lightweight RHEAs (MoNbTiV, AlMoNbTiW, CrMoNbTiV, and AlCrMoNbTiV) with equal atomic ratios were designed and calculated using first principles combined with quasi-harmonic approximation (QHA). The results indicate that all four RHEAs are stable BCC, exhibiting elastic anisotropy and ductility. The lightest density is 6.409 g/cm3. Adding Al/Cr can cause structural distortion and affect its mechanical properties. Their Young’s moduli are in the following order: AlCrMoNbTiV > MoNbTiV > CrMoNbTiV > AlMoNbTiV. The thermal expansion coefficients of the four RHEAs and titanium alloys are very close, with a difference in linear expansion coefficient of less than 1.16 × 10−5/K. Meanwhile, the metallurgical bonding of four types of RHEA coatings was successfully achieved on a Ti-6Al-4V(TC4) substrate through laser cladding technology, and all coatings exhibited a unique BCC solid solution phase.

First-principles calculations of phase transition, phonon spectra, thermodynamic properties and elasticity for PuO2 polymorphs

The first principles are utilized to calculate the phase transition, phonon spectra, thermodynamic properties, and elasticity of PuO2 under varying pressures. Under the compression condition, the anticipated pressure of phase transition from Fmm to Pnma is 26.7 GPa, from Pnma to Cmcm is 112.9 GPa, and from Cmcm to I4/mmm phase is 588.0 GPa. As the pressure decreases, the phase transition pressure of anticipating from Fmm phase to P42/mnm phase occur at -8.6 GPa. The phonon spectra of these six structures show that all phases are dynamically stable under the selected pressure. Meanwhile, the verification results of the mechanical stability criterion show that Fmm, Pnma, Cmcm and I4/mmm of PuO2 are mechanically stable, nevertheless P42/mnm is unstable in high pressure. The thermodynamic properties were then calculated to further research the patterns of variation in the coefficient of thermal expansion, bulk modulus, Gibbs free energy, and heat capacity with temperature, and these were compared with experimental data.

Preparation and properties of ultra-high hardness Co-Cr-Mo-Nb-B high-temperature amorphous alloy coating

In this paper, a high temperature and amorphous alloy coating of Co26Cr26Mo26Nb7B15 was prepared by high-velocity oxy-fuel spraying. The phase structure, thermodynamic properties, hardness, friction and wear behaviors, and corrosion behavior and its mechanism were studied. The results showed that the glass transition temperature of the coating reached to 1058 K, and the hardness was as high as 1589.4 HV. The amorphous alloy coating of Co26Cr26Mo26Nb7B15 exhibited excellent wear resistance. Its friction coefficient was only 0.1152, which was about 25 % of 316 stainless steel, and the wear volume was only 0.1338 mm3. Additionally, the coating presented excellent corrosion resistance in 1 M hydrochloric acid solution, with the corrosion current density of 1.04 × 10−5 A·cm−2, and corrosion voltage of −0.32 V vs SCE.

Critical Evaluation and Thermodynamic Optimization of the Cr–P and Cr–Fe–P Systems

Existing thermodynamic descriptions of the whole Cr–Fe–P system are insufficiently accurate for understanding the thermodynamic behavior of the Cr–Fe–P materials during the manufacturing process. To construct a more precise and consistent thermodynamic database of the Cr–Fe–P system, thermodynamic modeling of the Cr–P and Cr–Fe–P systems was conducted using the CALculation of PHAse Diagrams (CALPHAD) approach based on critical evaluation of the experimental data. The modified quasichemical model and compound energy formalism were employed to describe the liquid and solid solutions, respectively. The Gibbs energies of stoichiometric compounds Cr3P(s), Cr2P(s), CrP(s), and CrP2(s) were carefully determined based on reliable experimental data. The ternary (Cr,Fe)3P, (Cr,Fe)2P, and (Cr,Fe)P phosphides were modeled as solid solutions considering mutual substitution between Cr and Fe atoms. In addition, the phase equilibria of BCC_A2 and FCC_A1 solutions and the liquid phase of the ternary Cr–Fe–P system were also optimized for more accurate descriptions of existing phase equilibria and thermodynamic properties data. As an application of the present database, the experimentally unexplored thermodynamic properties and phase diagrams of the Cr–Fe–P system are predicted.

Thermodynamic re-assessment of the Al-Li-Zn system

Aluminum-lithium alloys are a kind of highly promising material due to low density, high strength and excellent modulus properties. The proper addition of Zn can effectively promote the precipitation of the main metastable strengthening phase δ′(Al3Li). As a crucial sub-system of Al-Li alloys, literature data on phase diagram and thermodynamic properties of the Al-Li-Zn system as well as the Al-Li and Li-Zn binary systems were comprehensively evaluated by the CALPHAD approach. The Li-Zn system was reassessed mainly by considering the newly reported data on formation enthalpy and activity and a 2-sublattice (SL) model was applied to describe the βLiZn4 phase. The Al-Li system was modified by considering AlLi2 and describing the metastable phase δ′(Al3Li) with interconvertible 4SL and 2SL ordered-disordered models. The predicted metastable fcc solvus was in perfect agreement with the measurements. Considering the available experimental data, the ternary Al-Li-Zn system was then re-optimized and a self-consistent thermodynamic description of the ternary Al-Li-Zn system was presented. The predicted metastable two-phase region of (Al)+δ’(Al3Li) in Al-Li-Zn system can be coupled with the accessible experimental data, which can be expected to well assist in designing high-strength Al-Li alloys.

First-principles calculations to investigate phase stability, elastic and thermodynamic properties of TiMoNbX (X=Cr, Ta, Cr and Ta) refractory high entropy alloys

This work uses first-principles calculations to investigate the phase stability, thermophysical and mechanical properties of refractory high entropy alloys (RHEAs) at finite temperatures. On the basis of plane wave quasi-potential and density functional theory, construct the structure model of a solid solution. The TiMoNbX (X = Cr, Ta, Cr and Ta) RHEAs have been determined to preserve a single body-centered cubic solid solution structure by calculations and the equilibrium lattice parameters and elastic modulus are consistent with experimental data obtained by laser cladding, which is combined with TC4 (Ti-6Al-4V) substrate. Using the quasi-harmonic Debye-Grüneisen model, the thermophysical characteristics of three RHEAs are investigated. The Voigt-Reuss-Hill scheme is used for calculating the Young's modulus (E), bulk modulus (B), shear modulus (G), and Poisson's ratio (ν), which indicates that all three RHEAs are ductile materials. Additionally, the modulus and hardness of materials decrease as temperature rises, whereas the properties of TiMoNbX RHEAs are predicted, as the nanoindentation hardness values at room temperature are comparable to, and slightly higher than the calculated values.

Application of DieselB10 formulations with short-chain alcohols in diesel cycle engines: phase equilibrium, physicochemical and thermodynamic properties and power curves

Application of DieselB10 formulations with short-chain alcohols in diesel cycle engines: phase equilibrium, physicochemical and thermodynamic properties and power curves

Formation mechanism of Hf-based ceramic particles in tungsten alloys

Abstract To meet the requirements of high strength of tungsten (W) based alloys at high temperature applied in the aerospace field, the preparation and formation of Hf-related ceramic particles in W were studied. It is found that the HfO2 phase with a size of about 500 nm was observed at the grain boundary in both W-0.26 wt.% HfC and W-0.25 wt.% HfH2-0.125 wt.% C systems. Further study of phase stability and thermodynamic properties of Hf(W)-O(C) compounds reveals that the HfO2 phase possesses the most stability of all the Hf-related compounds, and the oxidation of Hf is preferred to the carbonization. It is predicted that more stability of W base metal, higher temperature, and higher carbon concentration can reduce the formation of HfO2 while promoting the formation of the HfC particle phase.

DFT insight into the phase stability, optoelectronic, elastic, vibrational, and thermodynamic properties of metal chalcogenides RbKM (M = S, Se, Te) for energy harvesting technology

In this manuscript, the structural, optoelectronic, elastic, vibrational, and thermodynamic properties of RbKM (M = S, Se, Te) chalcogenides are explored via first principles approach. The estimated equilibrium lattice parameters a(c) through the TB-mBJ functional are 5.3876 Å (8.2810 Å), 5.2700 Å (8.6550 Å) and 5.2656 Å (8.7707 Å) for RbKS, RbKSe and RbKTe, respectively. The large value of the cohesive (Ecoh) and formation energy (Eform) reveals that all these compounds are stable at 0 K that may be difficult to decompose at ambient conditions. The direct band gap for RbKS, RbKSe and RbKTe is noted as 4.05 eV, 3.71 eV and 3.63 eV, respectively that is sufficient to declare them as semiconducting materials. So far as, the projected density of states (PDOS), pseudo electrons residing in d orbitals of the rubidium atoms contribute in the conduction region and p orbitals of chalcogen elements partake in the valence band. The optical parameters are determined by Kramers-Kronig relations. The elastic constants unveil that all compounds are mechanically stable and hold anisotropic nature. Here the vibrational properties of RbKM (M = S, Se, Te) are examined through Density functional perturbation theory (DFPT) technique. The Harmonic Approximation Method (HAM) is utilized to seek thermodynamic stability that is ensured due to the observance of negative free energy for all cases. Our theoretical outcomes for RbKM (M = S, Se, Te) can contribute significantly to amelioration for future research in devising optoelectronic and energy harvesting like appliances.

Enhanced mechanical and thermophysical properties of Mg2Ca, Al2Ca, and Al4Ca bulk metallic glasses in comparison to crystalline alloys for bone grafting applications: A molecular dynamics investigation

We investigate the glassy-state properties of Mg2Ca, Al2Ca, and Al4Ca from the grafting application viewpoint. We employed classical molecular dynamics to examine the phase transition, structural, thermodynamic, transport, and mechanical properties in the amorphous state. All properties suggest successful simulations of the glass phase at and below the glass transition temperature, ranging between 550 and 689 K for Mg2Ca, Al2Ca, and Al4Ca. Computed results are compared and discussed with the reported findings and known mechanical and thermal properties of the various parts of the human bones and biocomposites. The comparison establishes that the mechanical, thermal, and transport properties significantly improve in the glass phase compared to its crystalline alloy form. At 300 K, studied glasses have densities in close agreement with human bone density. Structural analysis and heat capacity show the second-order phase transition, verifying the formation of the glass structure. The targeted glasses exhibit excellent thermal conductivity and thermal diffusivity compared to other commonly used biocomposites for bone grafting. Furthermore, the simulated elastic properties, viz., the Poisson ratio, G/B ratio, Cauchy's pressure, and yield strength, are in close agreement with the mechanical properties of various parts of human bone. The predicted ductility nature, contrary to the brittle character of Mg2Ca, Al2Ca, and Al4Ca crystalline alloys, proves the superiority of the glassy form for the implant's functioning. The minimum enthalpy of formation and thermodynamic stability of studied compounds benefit the synthesis process; hence, we propose that the studied glasses are persuasive materials for experimental synthesis aimed at bone grating applications.

Critical evaluation and thermodynamic assessment of the Al2O3–TiO2–CaO ternary system

Knowledge about the thermodynamic equilibria of the Al2O3–TiO2–CaO system is important for the design of refractory and ceramic materials. The Al2O3–TiO2, Al2O3–CaO and CaO–TiO2 binary systems were reoptimized and the Al2O3–TiO2–CaO ternary system was assessed by CALPHAD (CAlculation of PHAse Diagram) approach due to the reliability of phase diagram and thermodynamic property data. The liquid phase was described by the ionic two-sublattice model with the formula (Al+3,Ti+2,Ti+3,Ca+2)P(O−2,AlO1.5,Va,O,TiO2)Q. A set of self-consistent thermodynamic parameters for the Al2O3–TiO2–CaO ternary system was finally obtained, reproducing well the phase diagram and thermodynamic properties, predicting the Ca4Ti3O10 primary crystallization field. The present thermodynamic description is of interest for the design of refractory and ceramic materials as well as the development of thermodynamic databases for multicomponent aluminosilicate system.

A cluster-based computational thermodynamics framework with intrinsic chemical short-range order: Part I. Configurational contribution

Exploiting Chemical Short-Range Order (CSRO) is a promising avenue for manipulating the properties of alloys. However, existing modeling frameworks are not sufficient to predict CSRO in multicomponent alloys (>3 components) in an efficient and reliable manner. In this work, we developed a hybrid computational thermodynamics framework by combining unique advantages from Cluster Variation Method (CVM) and CALculation of PHAse Diagram (CALPHAD) method. The key is to decompose the cumbersome cluster variables in CVM into fewer site variables of the basic cluster using the Fowler-Yang-Li (FYL) transform, which considerably reduces the number of variables that must be minimized for multicomponent systems. CSRO is incorporated into CALPHAD with a novel cluster-based solution model called FYL-CVM. This new framework brings more physics into CALPHAD while maintaining its practicality and achieves a good balance between accuracy and computational cost. It leverages statistical mechanics to yield a more physical description of configurational entropy and opens the door to cluster-based CALPHAD database development. The application of the FYL-CVM model in a prototype fcc AB alloy demonstrates its capability to calculate the phase diagram and thermodynamic properties with remarkable accuracy comparable to CVM. The hybrid CVM-CALPHAD framework represents a new methodology for thermodynamic modeling that enables atomic-scale order to be exploited for materials design.

First-principles thermodynamic investigation on the α phases in TiO and TiNb binary system.

O and Nb are two representative alloying elements of Ti to form high-temperature and corrosion resistance α Ti alloys. The investigation on the thermodynamic characteristics of α Ti-O and Ti-Nb has attracted much attention in recent years. However, in this regard, a satisfied experimental technique or modeling scheme is still yet to be developed due to the appearance of a variety of oxides in Ti-O and the mechanical instability present in Ti-Nb. Herein, we combined first-principles calculations with the cluster expansion method to investigate the ground-state characteristics for α Ti-O and α Ti-Nb systems. The atomic bonding interactions in these two systems were first revealed based on the calculated electronic structures. Afterward, the Debye-Grüneisen model and Monte Carlo simulations were employed together to investigate the thermodynamic properties of α phases in these two systems, and the effect of vibrational entropy on the order-disorder transition temperatures of the phases in α Ti-O system was first examined. A good agreement with experimentally reported phase boundaries is obtained in the Ti-Nb system by handling the mechanical instabilities introduced by the highly distorted structures. In addition, the cluster expansion coefficients for the Ti-O and Ti-Nb system offer a good starting point to investigate the phase equilibrium in Ti-Nb-O ternary alloy. We also believe the insights provided here would be helpful for those who would like to seek an efficient scheme they are confident with to investigate the phase thermodynamic properties of other hcp Ti-based alloys.

Comprehensive analysis of the phase stability, optoelectronic, mechanical, thermodynamic, and vibrational properties for prospective optoelectronic applications of novel combinations of chalcogenides XScTe2 (X = Li, Rb) by employing density functional theory

Comprehensive analysis of the phase stability, optoelectronic, mechanical, thermodynamic, and vibrational properties for prospective optoelectronic applications of novel combinations of chalcogenides XScTe2 (X = Li, Rb) by employing density functional theory

Thermodynamic Assessment of the P2O5-Na2O and P2O5-MgO Systems.

Knowledge about the thermodynamic equilibria of the P2O5-Na2O and P2O5-MgO systems is very important for controlling the phosphorus content of steel materials in the process of steelmaking dephosphorization. The phase equilibrium and thermodynamic data of the P2O5-Na2O and P2O5-MgO systems were critically evaluated and re-assessed by the CALPHAD (CAlculation of PHAse Diagram) approach. The liquid phase was described by the ionic two-sublattice model for the first time with the formulas (Na+1)P(O-2, PO3-1, PO4-3, PO5/2)Q and (Mg+2)P(O-2, PO3-1, PO4-3, PO5/2)Q, respectively, and the selection of the species constituting the liquid phase was based on the structure of the phosphate melts. A new and improved self-consistent set of thermodynamic parameters for the P2O5-Na2O and P2O5-MgO systems was finally obtained, and the calculated phase diagram and thermodynamic properties exhibited excellent agreement with the experimental data. The difference in the phase composition of invariant reactions from the experimentally determined values reported in the literature is less than 0.9 mol.%. The present thermodynamic modeling contributes to constructing a multicomponent oxide thermodynamic database in the process of steelmaking dephosphorization.

A Comprehensive Ab Initio Study of the Recently Synthesized Zintl Phase CsGaSb2 Structural, Dynamical Stability, Elastic and Thermodynamic Properties

A Comprehensive Ab Initio Study of the Recently Synthesized Zintl Phase CsGaSb2 Structural, Dynamical Stability, Elastic and Thermodynamic Properties

Thermodynamic assessment of the Cr–Si binary system

A thermodynamic evaluation of the Cr–Si system was performed concerning the latest experimental phase diagram and with the aid of first-principles calculations. The thermodynamic parameters for the Gibbs energy of pure Cr were modified based on the new experimental value of 1861 °C for the melting point of pure Cr, which was previously reported as 1907 °C in the SGTE database. The Gibbs energy descriptions of the Cr3Si and Cr5Si3 phases were revised using Cr3(Cr,Si)- and (Cr,Si)5Si3-type two-sublattice models to reproduce the latest experimental results of their solubility composition ranges, that is, Cr3Si extending toward the Cr-rich side and Cr5Si3 extending toward the Si-rich side from the stoichiometry. The CrSi and CrSi2 phases were considered line compounds with no solubility range, and the solubility of Cr in the Si phase was ignored. A set of self-consistent thermodynamic parameters for the Cr–Si system was obtained using the CALPHAD technique. The phase diagrams calculated using the optimized parameters showed reasonable agreement with the latest phase equilibrium data and thermodynamic property data in the literature, including the enthalpy of mixing, formation enthalpy, and chemical potential diagrams of Cr and Si in the equilibrium phases.

Solid-liquid phase equilibrium and thermodynamic properties analysis of 1,3,5-tribromobenzene in sixteen kinds of organic mono-solvents

Solid-liquid equilibrium solubility of 1,3,5-Tribromobenzene (m-TBB) in 16 pure solvents, including ethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, amyl acetate, acetone, 2-butanone, cyclohexanone, 1,2-dichloroethane, chloroform, cyclohexane, toluene, tetrahydrofuran (THF), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMA) were determined by gravimetric method at different temperatures. The solubility of m-TBB increases gradually with the increase of temperature. The order of solubility of m-TBB in alkanes solvents is: chloroform > 1,2-dichloroethane > cyclohexane. The order of solubility of m-TBB in esters solvents is: amyl acetate > butyl acetate > propyl acetate > ethyl acetate > methyl acetate > ethyl formate. The order of solubility of m-TBB in ketones solvents is: cyclohexanone > 2-butanone > acetone. The order of solubility of m-TBB in other solvents is: THF > toluene > DMA > DMF. The KAT-LSER model was selected to explore the solvent effect of m-TBB in the tested solvents. Four thermodynamic models, i.e., the modified Apelblat model, the λh model, the NRTL model and the Wilson model, were selected for correlate the solubility data of m-TBB in 16 mono-solvents. The RAD and the RMSD values of NRTL model were all less than 1.67 × 10-2 and 3.82 × 10-4, respectively. All the four theoretical models can correlate the solubility data of m-TBB well in the selected solvents. The dissolution process of m-TBB were calculated based on the Wilson model. The dissolution process of m-TBB is endothermic, entropy increase and spontaneous. The entropy contributes more to Gibbs free energy.

Solid – phase equilibria and thermodynamic properties of the Sb-Te-S system

The powder X-ray diffraction (PXRD) analysis and the electromotive force (emf) measurements have been used to investigate the Sb–Te–S system in the Sb2S3-Sb2Te3-Te-S composition region at 300–450 K temperatures interval. Relative partial molar functions of antimony in alloys have been calculated and obtained data have been used to get self-consistent sets of the standard Gibbs free energy, standard enthalpy, and standard entropy of the Sb2S3 and Sb2Te2S compounds, as well as the Sb2Te2,4S0,6 and Sb2Te2,7S0,3 solid solutions. The data obtained for Sb2S3 have been compared to the ones available in the literature. Thermodynamic functions of the Sb2Te2S compound, as well as, the Sb2Te2,4S0,6 and Sb2Te2,7S0,3 solid solutions have been determined for the first time.