Thermodynamic Studies of the Fe-Cr-C-N System by EMF Measurements

In this work, the Fe-Cr-C-N alloys were synthesized by nitriding the Fe, Cr, and C powder mixtures at 1573 K in the N₂ gas (101 325 Pa). The nitrogen content and phase relationships at 1173 K in the alloys were investigated by the use of an equilibration technique. The thermodynamic activities of chromium in the alloys were studied using the solid-state galvanic cell method with CaF₂ as the solid electrolyte in the temperature range 973 to 1173 K in an atmosphere of N₂ gas (101 325 Pa). The activities of chromium in the Fe-Cr-C-N alloys were calculated and compared with those of the corresponding Fe-Cr-C ternary alloys with pure bcc-Cr as standard state. X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods were used to identify the equilibrium phases and microstructures of the investigated alloys. The experimental results show that a Cr₂N-based nitride was formed during the nitriding procedure in the alloys. The nitrogen content in the alloys decreases with the decreasing chromium content, as well as the increasing temperature. The addition of nitrogen to the ternary Fe-Cr-C alloy was found to have a strong negative impact on the Cr activity in the Fe-Cr-C-N system.     

Kinetics of diffusion in the Nb-Al system

Diffusion kinetics were studied by varying the time and temperature (800° to 1300°C) of dipping solid niobium into molten aluminum. It was found by X-ray diffraction analysis that only the Al₃Nb phase forms at the surface of the niobium specimen and that the thickness of this layer for a given dip temperature varies parabolically with time. The activation energy and the preexponential factor of the diffusion parameter, (δD) were found to be 36.5 ∓ 0.45 kcal per mole and 2.0 ∓ 0.34 sq cm per sec, respectively.     

磷酸钙体系热力学分析

运用热力学数据，绘制出稳态磷酸钙体系在298K、不同pH值下的热力学平衡图，讨论了溶液中可能出现的磷酸钙盐的溶解度与pH之间的关系。计算得到了不同pH条件下含钙、磷溶液极限饱和溶解行为与pH的关系，并进行了实验验证，给出了过饱和溶液的浓度和pH范围。     

Investigation of leaching of oxidized Nb-Al sublimates

Using the method of rational planning the experiment, the sulfuric acid leaching of products that result from oxidized roasting-sintering of the sublimates of electron-beam remelting of niobium with sodium carbonate is investigated. The possibility of concentrating Nb in the solid phase due to the transfer of the accompanying elements (Al, Fe, Cr, Si) into the solution is considered. Multifactor mathematical models of sulfuric acid leaching are constructed, and kinetic parameters of the process are determined. Based on them, the conditions for obtaining a niobium chemical concentrate suitable for smelting the crude metal are optimized.     

Thermodynamic Modeling of the Al-Ti-V Ternary System

The sub-binary systems Al-Ti, Ti-V, and Al-V are reviewed and adopted from the previous assessments, the thermodynamic analysis of the Al-Ti-V ternary system is performed by the CALPHAD approach, and a set of self-consistent thermodynamic parameters of the ternary system are obtained. Furthermore, the isothermal sections of this system at 1073 K, 1173 K, 1273 K, 1373 K, and 1473 K (800 °C, 900 °C, 1000 °C, 1100 °C, and 1200 °C) and the ternary invariant equilibria are calculated and compared with the corresponding experimental data, and all are in good agreement with most of the experimental results. Thus, the optimized thermodynamic parameters in this study may provide more accurate guidance to develop the new alloys involving it.     

Structure and properties of Nb-Al alloys prepared by powder metallurgy

The structure and short-time strength of Nb-Al alloys of two compositions prepared by powder metallurgy are studied. The mechanical alloying of niobium with aluminum in a planetary ball mill in air is shown to result in simultaneous alloying of niobium with oxygen. During subsequent vacuum high-temperature sintering, disperse particles of a complex oxide, whose tentative composition is (AlNb)₂O₃, form in the alloy structure. The short-time strength at 1250°C of the prepared alloys exceeds that of nickel-aluminum superalloys.     

Cu-In体系的热力学优化

评估了Cu-In体系的相平衡和热力学实验结果,并对体系进行了热力学优化。采用替代模型描述体系的液相和富铜固溶体相,双亚晶格模型描述线性化合物相,三亚晶格模型描述非线性化合物相,结合选取合理的实验数据,优化得到Cu-In体系各相的热力学参数,用优化结果计算的相图以及热力学性质与实验结果吻合。     

Solution and Thermodynamic Studies on Binary and Ternary Complexes of Lanthanides

The interactions of La(Ⅲ), Pr(Ⅲ), Nd(Ⅲ), Sm(Ⅲ), Eu(Ⅲ), Gd(Ⅲ), Dy(Ⅲ), and Yb(Ⅲ) with cytosine, 5-bromocytosine, 5-azacytosine and 5-flurocytosine as primary ligands (L) and guanine (A) as secondary ligand for both binary (1:1) as well as ternary (1:1:1) systems were investigated by potentiometric equilibrium measurements at 25, 35 and 45 ℃ in aqueous solution (ionic strength, μ=0.1 mol·dm-3 NaNO3). The stability constants of the binary (1:1) and ternary (1:1:1) metal-ligand complexes follow the following order La＜Pr＜Nd＜Sm＜Eu＞Gd＜Dy＞Yb. Results also indicate that the ternary lanthanide complexes of La(Ⅲ), Pr(Ⅲ), Nd(Ⅲ), Sm(Ⅲ), Eu(Ⅲ), Gd(Ⅲ), Dy(Ⅲ), and Yb(Ⅲ) are more stable than corresponding binary lanthanide complexes. The enthalpy (Δhof) and entropy (Δsof) changes for the formation of binary and ternary complexes were calculated from temperature coefficient data. The ΔΔSof values are positive for all the metal ligand systems. The negative ΔΔHof values indicate the extra stability of the ternary complexes by the exothermic enthalpy changes (ΔΔSof=ΔTSof-ΔBSof and ΔΔHof=ΔTHof-ΔBHof where ΔTSof, ΔTHof and ΔBSof, ΔBHof are the entropy and enthalpy values associated with the ternary and binary complexes, respectively). It was also proposed that the guanine is bonded to metal ions through N1/C6=O and N7 whereas cytosine and its derivatives are bonded through N3 atoms in ternary complexes.     

铌-铝化合物的机械合金化制备及机理

研究高能球磨制备Nb/Al化合物的工艺,探索在高能球磨过程中Nb、Al形成化合物的机理.结果表明,通过高能球磨可获得Al在Nb中的固溶体,固溶度与球磨转速和球磨时间成正比,并发现选用硬脂酸作为添加剂有利于Nb/Al的机械合金化.对高能球磨中机械合金化的机理进行了讨论,指出高能球磨产生的高比表面能和高密度晶体缺陷大大降低...     

Thermodynamic Study on MgO Solubility in High-Alumina-Content Slag System

Metallurgical and Materials Transactions B - In the current study, the MgO solubility in molten slag was measured to clarify the effect of basicity and Al2O3 content on the MgO solubility...     

Zr-Nb-O三元系的热力学优化

综合评估了文献报道的Zr-Nb-O三元系及其子二元系的相图及热力学信息。液相的Gibbs自由能采用离子亚晶格模型描述,固溶体相(α,β)和所有化合物(αZrO2,βZrO2,γZrO2,NbO,NbO2和Nb2O5)的Gibbs自由能都采用双亚晶格模型描述。用CALPHAD(CALculation ofPHAse Diagrams)技术,使用Pandat软件中的PanOptimizer优化模块,对Zr-O二元系进行了热力学优化,计算得到的相图和热力学性质与实验结果相吻合。应用优化的Zr-O二元系模型参数,结合Zr-Nb、Nb-O已有的热力学评估结果,对Zr-Nb-O三元系进行了热力学优化,得到了该体系的一套热力学模型参数。计算了Zr-Nb-O三元系在1273,1473和1773 K温度下的等温截面,与实验数据符合得较好。计算了若干该体系在富Zr区α+ββ的相转变温度,结果和实验测量也能较好地吻合。研究结果对建立多元锆合金热力学数据库,以及指导新型锆基合金材料的成分设计具有重要意义。     

Phase Equilibria and Thermodynamic Studies in the System CaO−FeO−Fe2O3−SiO2

Phase equilibria and thermodynamic properties of the system CaO?FeO?Fe₂O₃?SiO₂ were studied at 1450° and 1550°C, over a range ofpO₂ from 1 to about 10^?11 atm. Isothermal phase diagrams and activity-composition diagrams were constructed for 0, 5, 10, 20, and 30 wt pct SiO₂ sections. The data are applicable to further understanding the behavior of simple BOF steelmaking slags.     

Experimental Investigation and Thermodynamic Calculation of the Co-Si-Zn System

Phase relations of the Co-Si-Zn ternary system were experimentally investigated and thermodynamically calculated. First, the isothermal sections of the Co-Si-Zn system at 1123 K and 1323 K (850 °C and 1050 °C) were investigated experimentally using scanning electron microscopy coupled with wave-dispersive X-ray spectroscopy and X-ray diffraction. Then the thermodynamic calculation for this system was carried out using the CALPHAD technique. The calculated results and the experimental data are reasonably self-consistent.     

Experimental Investigation and Thermodynamic Modeling for the Mg-Nd-Sr System

Microstructure examination, phase analysis, and DSC measurement on the equilibrated ternary alloys not only enabled exploration of the phase equilibria relations of the Mg-Nd-Sr ternary but also thermodynamic assessment of the ternary system in the context of the CALPHAD approach. Thermodynamic modeling, further coupled with first principle calculations, was thereafter used to predict a panoramic phase diagram for the Mg-Nd-Sr ternary system at the Mg-rich corner.     

Experimental Investigation and Thermodynamic Modeling of the Ag-Cu-Ge System

Metallurgical and Materials Transactions A - The liquidus surface projection was re-investigated using scanning electron microscopy with energy dispersive spectrometer and differential thermal...