Ni-Al系金属间化合物价电子结构计算及界面反应预测

应用固体与分子经验电子理论,计算了Ni-Al系各相的价电子结构和理论结合能,并应用理论结合能值进一步计算了各相的反应生成焓,通过各相生成焓的比较对界面反应生成相进行了预测。Ni、Al、Ni3Al、Ni5Al3、NiAl、Ni2Al3和NiAl3的结合能计算值分别为427.44,324.58,441.11,440.10,435.51,432.66,395.05 kJ/mol,与实验值吻合良好。在Ni/Al界面,Ni2Al3相的生成焓最小,保温过程中,Ni2Al3相将最先析出。随后,NiAl相将在Ni2Al3/Ni的界面形成,而Ni3Al相将在NiAl/Ni的界面形成。在NiAl/Ni3Al界面,Ni5Al3生成焓绝对值较小,需要在较高温度下保温较长时间才可能形成。界面反应生成相预测结果与实验结果吻合。     

High Temperature Thermodynamic Properties of ZnTe(s)

We have gathered the partial pressure, Knudsen cell, and emf measurements on ZnTe(s) from which the Gibbs energy of formation can be calculated. Published partial pressures of diatomic tellurium have been adjusted to take account of a subsequently published third law analysis of tellurium. The equation used to calculate the total pressure from the rate of mass loss from an extensive set of Knudsen cell measurements has been corrected to give a 5% increase in total pressure and the Gibbs energy of formation has been recalculated. A high temperature heat capacity for ZnTe(s) has been selected from the published data. The Gibbs energies of formation as a function of temperature have then been fit using a third law analysis to give two essentially equally good but extreme fits. In the first, the standard enthalpy of formation agrees with the calorimetric value of −119 kJ/mol but the standard entropy of ZnTe(s) is low by 2-3 J/mol K. In the second, the standard enthalpy of formation is more positive than the calorimetric values by about 3 kJ/mol but the standard entropy of ZnTe(s) is 82 J/mol K and close to the value from low temperature heat capacity measurements. We select values of −119.49 kJ/mol for the standard enthalpy of formation and 78.23 J/mol K for the standard entropy.     

Computational and experimental study of phase stability,cohesive properties,magnetism and electronic structure of TiMn2

By an ab initio approach we calculated phase stability, cohesive and magnetic properties, and the electronic structure of TiMn₂ for the C14 and C15 Laves structure types. The nonmagnetic C14 phase is the ground state in accordance to experiment, whereas a metastable ferromagnetic C15 phase is predicted with a local magnetic moment of 0.78 μ_β for Mn. The energy of formation was measured by a calorimetric drop experiment resulting in a value of −86.76±6.79 kJ mol⁻¹ at 298 K being in good agreement to the ab initio result of −88.8 kJ mol⁻¹. Model calculations based on Miedema’s approach failed to yield reasonable results. The calculated densities of states reveal strong hybridisation between Ti-like and Mn d-like states.     

Thermodynamic reassessment of the Ni–Ru system and assessment of the Al–Ni–Ru system at 1273–1523 K using ab initio calculations

The Ni–Ru and Al–Ni–Ru systems are assessed with a combined CALPHAD and ab initio approach. Particular attention is paid to the possible existence of a miscibility gap in the B2 phase. Both face-centered cubic and body-centered cubic ordering are analyzed within the compound energy formalism. Ab initio calculations for the B2 phase show a similar trend as calorimetric measurements but the magnitude is much smaller. It is found that the calorimetric measurements cannot be reconciled with any reasonable phase diagram, whereas the ab initio results can. From the parameters obtained, isothermal sections in reasonable agreement with experimental phase diagrams are calculated. We have concluded that there is no miscibility gap in the B2 phase at 1273 K and higher temperatures.     

Thermodynamic assessments of the phase diagrams of the hafnium-vanadium and vanadium-zirconium systems

Thermodynamic assessments have been made for the hafnium-vanadium (Hf-V) and vanadium-zirconium (V-Zr) systems using the Calphad-Thermocalc approach. The Gibbs energies of the liquid, body-centered cubic, and close-packed hexagonal phases were described by a substitution solution model with a Redlich-Kister formalism to express the excess Gibbs energy. The C15-Laves phase was treated first as stoichiometric and then with a composition range. A consistent set of optimized thermodynamic parameters was obtained, and calculated phase equilibria were compared with the experimental data. The enthalpy of formation of the C15-Laves phase was calculated equal to approximately −3 and −5 kJ/mol, respectively, in the Hf-V and V-Zr systems, which is in good agreement with predicted values.     

Anelastic effects connected with isothermal martensitic transformations in 24Ni4Mo austenitic and 12Cr9Ni4Mo maraging steels

Anelasticity of the austenitic steel 24Ni5Mo and the stainless steel 12Cr9Ni4Mo has been investigated in the austenitic state after quenching with respect to isothermal martensitic transformation during cooling and subsequent heating. Maxima of anelasticity due to isothermal transformation at ≈200 K (24Ni5Mo, 0.002% C) and ≈250 K (12Cr9Ni4Mo; 0.01% C) coincided well with C-curve noses obtained by methods based on magnetic properties and electric resistivity. Corresponding internal friction maxima were found to be dependent on cooling or heating rate, quenching temperature and the frequency of oscillation and may therefore be described using the Delorme approximation. The activation energy of isothermal martensitic transformation calculated from the lower part of the C-curves estimated using the Borgenstam–Hillert and Arrhenius methods (3–8 kJ/mol for 24Ni5Mo and 15–20 kJ/mol for 12Cr9Ni4Mo) are comparable with the energy of impurity–dislocation interaction (≈10 kJ/mol) and interpreted as too low to be caused by diffusion processes: the activation energy for carbon diffusion in austenitic steel 24Ni5Mo is found to be ≈135 kJ/mol and ≈145 kJ/mol for austenite in two-phase 12Cr9Ni4Mo steel. An estimation showed that the activation energy for the isothermal martensitic transformation for the 24Ni5Mo alloy with so-called binary martensitic kinetics was higher in the vicinity of the nose of the C-curve, became lower with a decrease in temperature range and approached zero in the vicinity of the athermal martensitic point. A similar effect was not observed in the 12Cr9Ni4Mo steel.     

Contribution to the thermochemistry of rare earth pnictides: The Sm-Bi system

Formation enthalpies of Sm-Bi alloys (in the complete range of compositions) and Er-Bi alloys (for a few compositions) have been measured using a direct, small-furnace, isoperibolic aneroid differential calorimeter. Typical values for the reaction in the solid state at 300 K are: Sm₂Bi,−88 ± 3; Sm₅Bi₃, −94 ± 4; Sm₄Bi₃, −104 ± 2; SmBi, −108 ± 2; SmBi₂, −76 ± 4; and ErBi, −90 ± 5 kJ/g-atom. The experimental data are briefly discussed, compared with those of similar rare earth compounds, and found to be in good agreement with those computed according to the Miedema model and, for the rare earth-rich alloys, also with those calculated according to the Kubaschewski suggestion based on the so-called “effective coordination number” in alloys.     

First-principles investigation of the Cu–Ni,Cu–Pd,and Ni–Pd binary alloy systems

Phase diagrams of copper–nickel–palladium binary alloys were determined by density functional theory cluster expansion method. The system has both magnetic and non-magnetic binaries and subtle phase coexistence areas between similar and different kind of lattice types. Furthermore, the CuPd binary has several ordered structures. Cluster expansion models were constructed by heuristic cluster selection for all of the fcc structures and for the CuPd_bcc structure. Both configurational and magnetic phase diagrams were determined. Small amount of nickel magnetize fcc palladium to 0.26 μ_B from which the magnetic moment rises almost linearly to that of pure Ni. In CuNi, 0.46 x-Ni is needed for the magnetic transition. In CuPd alloy in 0 K, configurational free energy difference between bcc and fcc lattice resulting to phase separation is only about 1.1 kJ/mol-atoms. Low temperature energetics and magnetic phase diagrams have good quantitative agreement with available experimental and theoretical results. Finite temperature properties of the alloys are in good qualitative agreement with experimental results.     

Thermodynamic properties of Al,Ni, NiAl,and Ni3Al from first-principles calculations

The thermodynamic properties of Al, Ni, NiAl, and Ni₃Al were studied using the first-principles approach. The 0-K total energies are calculated using the ab initio plane wave pseudopotential method within the generalized gradient approximation. The contribution to the free energy from the lattice vibration was calculated using the phonon densities of states derived by means of the ab initio linear-response theory. The thermal electronic contribution to the free energy was obtained from the one-dimensional numerical integration over the electronic density of states. With the deduced Helmholtz free-energy, the thermal expansion and enthalpy as a function of temperature were calculated and compared with the experimental data. Our calculations show that the enthalpies of formation are slightly temperature dependent with a slope of −1.6 J/mol/K for NiAl and −1.2 J/mol/K for Ni₃Al. For Ni, the inclusion of thermal electronic excitation results in a 10% increase in thermal expansion and 15% increase in enthalpy at 1600 K.     

Stability and thermodynamic properties of supersaturated solid solution and amorphous phase formed by ball milling in the Zr- Al system

Zr ₁₀₀-_xA1_x (x ≤ 40) metastable alloys were synthesized by high- energy ball milling of elemental Zr and Al powders: supersaturated substitutional cph solid solution for x ≤ 15 and an amorphous phase for x ≥ 17.5. We performed a calorimetric study of the thermodynamics and kinetics of the metastable- to- equilibrium transformations of these phases. Their stability range (temperature/composition), as well as the apparent activation energies associated with the transformations, were determined. The transformation enthalpies were measured and used to determine the enthalpy of formation for these metastable phases. For both as- milled and relaxed amorphous phases, the measured enthalpy of crystallization is compared with those estimated for an undercooled liquid. Different amounts of retained entropy at the glass transition temperature were used to estimate the enthalpy loss upon undercooling due to the excess specific heat. This paper was presented at the Thermodynamics and Phase Equilibria of Metastable Phases Symposium at the Spring TMS Meeting, March 1-4,1992, in San Diego. The symposium was organized by Philip Nash, Illinois Institute of Technology, and Ricardo Schwarz, Los Alamos National Laboratory.     

乙二胺改性木屑黄原酸盐对水溶液中Cu（Ⅱ）和Ni（Ⅱ）离子吸附平衡及动力学

使用乙二胺改性的木屑黄原酸盐对水溶液中的Cu（II）、Ni（II）离子进行吸附。在单离子体系中,考虑影响因素（温度、投加量）对Cu（II）、Ni（II）单离子吸附等温线的影响;并计算Cu（II）、Ni（II）离子吸附的热力学参数：吸附吉布斯自由能（△GΘ）、吸附过程的焓变（△HΘ）以及熵变（△SΘ）,表明此吸附是一个放热自发的过程。在 Cu（II）和Ni（II）双离子体系中,采用修正后的拓展Langmuir模型对体系的吸附情况可以进行很好的预测。在单离子体系和双离子体系中,吸附过程的数据均可通过准二级动力学模型进行描述;计算得到其对Cu（II）和Ni（II）单离子的吸附活化能分别为59.12和55.92 kJ/mol。结果表明,金属离子在改性木屑表面的吸附效果会受到另一离子存在的影响。     

Calorimetric and Electromotive Force Measurements of Al-Li-Zn Liquid Solutions

The solution calorimetry and electromotive force methods were used for the study of the mixing enthalpy and partial excess Gibbs energy of the Al-Li-Zn liquid solutions. Calorimetric investigations were conducted for solutions with the ratio of X _Li/X _Al and X _Li/X _Zn = 0.8/0.2 and at the temperatures of 942 and 978 K, respectively. The electromotive force studies were performed at two temperatures: 873 and 923 K by the titration technique and for dilute solutions. Based on the data of the mixing enthalpy change and the partial excess Gibbs energy of Li available in the literature, together with that obtained in these studies, the ternary interaction parameters were elaborated. The comparative analysis of the experimental mixing enthalpy change generally showed a good agreement with the values calculated based on different models. The observed deviations between the experimental and the calculated values were, for most of the experimental data, lower than 1 kJ/mol. The experimental partial excess Gibbs energy of Li showed a satisfactory agreement with that modeled on the basis of the ternary parameters elaborated in this work.     

Thermodynamic analysis and assessment of the Ce–Ni system

An optimised set of thermodynamic parameters for the Ce–Ni system has been obtained using the CALPHAD approach. A thorough thermodynamic analysis of the system has been carried out using different calorimetric techniques and the data have been used in the assessment. The free energy of the liquid phase has been described as a function of temperature and composition using a Redlich–Kister polynomial. Solid compounds have been considered as stoichiometric with the exception of the Laves phases. The phase diagram and thermodynamic quantities calculated from assessed parameters agree well with experimental data.     

Thermodynamic properties of 1-nutyl-3-methylimidazolium chloride (C<Subscript>4</Subscript>mim[Cl]) ionic liquid

Thermodynamic properties of 1-butyl-3-methylimidazolium chloride (C₄mim[Cl]) ionic liquid were determined using thermogravimetric (TG) differential thermal analysis (DTA). A new method called DTA mass-difference baseline, was used to measure the heat capacity and enthalpy change of phase transformation of ionic liquid from DTA curves. Based on this, the changes in standard enthalpy, entropy, and Gibbs energy were determined. The results show that standard enthalpy and entropy changes of C₄mim[Cl] increase nonlinearly with increasing temperature, while the standard Gibbs energy change decreases nonlinearly with increasing temperature within the temperature range studied (298–453 K). The standard enthalpy of melting and enthalpy of vaporization were determined to be 0.93 and 11.07 kJ/mol, respectively.     

Thermodynamic Evaluation of Gadolinium

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Electronic theory of phase stability in substitutional alloys: application to the Au–Ni system

The total energies of formation of Au–Ni superstructures based on a fcc lattice have been calculated using the linear muffin-tin-orbital (LMTO) method in the full potential approach. Both unrelaxed and relaxed structures have been included in the calculations. The energy of formation is decomposed into three terms, a volume deformation contribution, a chemical contribution and a relaxation contribution. The enthalpy of mixing of the disordered solid solution has been calculated using an Ising-like cluster expansion for both the chemical and relaxation effects. In the Gibbs energy of mixing, a configurational entropy of mixing has been calculated with the cluster variation method (CVM) and the thermal excitations due to electronic and vibrational effects have been taken into account. The miscibility gap displayed in the Au–Ni system has been calculated. The results are discussed in comparison with the experimental data.     

Temperature dependence of magnetic properties of a disordered Fe<Subscript>0.65</Subscript>Ni<Subscript>0.35</Subscript>

The method of calculation of average and local magnetic characteristics of transition metals at finite temperatures developed by the author and Grebennikov in previous works and based on the employment of a real band structure and spin fluctuations has been applied to a disordered invar alloy Fe_0.65Ni_0.35. The magnetization, Curie temperature, local magnetic moment, and uniform and local susceptibilities have been calculated for both ferromagnetic and paramagnetic states. The results are in agreement with experimental data in a wide temperature range. It has been shown that the effect of disorder in the filling of sites with Fe and Ni atoms on the magnetic properties of the Fe-Ni invar is insignificant.     

Electronic structure and properties of LaNi<Subscript>5</Subscript> compound from first principles

The energy, electronic structure, and magnetic and mechanical properties of LaNi₅ compound have been studied by the first-principles method based on the density functional theory. The results show that the calculated lattice parameters of LaNi₅ compound are almost the same with the experimental ones, and the compound is easy to form and very stable. The bond between La and Ni1 atoms is an ionic bond, and electrostatic attraction effect exists between Ni atoms. The farther the distance between Ni atoms in the LaNi₅ crystal cell is, the stronger the electrostatic attraction effect is. LaNi₅ intermetallic compound is ductile and ferromagnetic. The calculated hardness value of LaNi₅ compound is 7.04 GPa, and the calculated elastic properties are close to the experimental results.     

Thermodynamic investigation of the Lu---Pb system

The Lu---Pb alloys were studied by different techniques. The molar heat capacities of the solid compounds Lu₅Pb₃ and Lu₆Pb₅ were determined in the range 525–823 K using differential scanning calorimetry. The enthalpy of formation of LuPb₂ was obtained by both emf and calorimetric methods. Potentiometric measurements were performed in the range 610–730 K and a value of −35 ± 2 kJ (mol at.)⁻¹ was obtained for the enthalpy of formation of LuPb₂ in the solid state at 298 K. By using a direct isoperibolic aneroid differential calorimeter the value Δ_formH = −34 ± 2 kJ (mol at.)⁻¹ was determined. The data obtained in this study are compared with those of other similar rare earth-lead compounds and discussed briefly.