Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the CrO-Cr2O3-SiO2 and CrO-Cr2O3-SiO2-Al2O3 systems

Available thermodynamic and phase diagram data have been critically assessed for all phases in the CrO-Cr₂O₃-SiO₂ and CrO-Cr₂O₃-SiO₂-Al₂O₃ systems from 298 K to above the liquidus temperatures and for oxygen partial pressures ranging from equilibrium with metallic Cr to equilibrium with air. All reliable data have been simultaneously optimized to obtain one set of model equations for the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature. The modified quasi-chemical model was used for the slag. The models permit phase equilibria to be calculated for regions of composition, temperature, and oxygen potential where data are not available.     

Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the Al-Mg, Al-Sr, Mg-Sr, and Al-Mg-Sr Systems

All available thermodynamic and phase diagram data were critically assessed for all phases in the Al-Mg, Al-Sr, and Mg-Sr systems at 1 bar pressure from room temperature to above the liquidus temperatures. For these systems, all reliable data were simultaneously optimized to obtain a set of model equations for the Gibbs energy of the liquid alloy and all solid phases as functions of composition and temperature. The modified quasi-chemical model was used for the liquid. The Al-Mg-Sr ternary phase diagram was calculated from the optimized thermodynamic properties of the binary systems. Since no reliable ternary data were available, three assumptions were made: no ternary terms were added to the model parameters for the thermodynamic properties of the liquid, no ternary solid solutions are present in the system, and no ternary compound is present in the system. The calculated ternary phase diagram is thus a first approximation, which can be improved by the addition of new experimental data and can be used as a base for the calculation of phase diagrams of multicomponent systems.     

Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the CrO-Cr2O3, CrO-Cr2O3-Al2O3, and CrO-Cr2O3-CaO systems

Available thermodynamic and phase diagram data have been critically assessed for all phases in the CrO-Cr₂O₃, CrO-Cr₂O₂-Al₂O₃, and CrO-Cr₂O₂-CaO systems from 298 K to above the liquidus temperatures and for oxygen partial pressures ranging from equilibrium with metallic Cr to equilibrium with air in the case of the first two systems and toP _{O 2} = 10⁻³ atm for the CrO-Cr₂O₃-CaO system. All reliable data have been simultaneously optimized to obtain one set of model equations for the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature. The modified quasichemical model was used for the slag. The models permit phase equilibria to be calculated for regions of composition, temperature, and oxygen potential where data are not available.     

Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the CrO-Cr2O3-SiO2 and CrO-Cr2O3-SiO2-Al2O3 systems

Available thermodynamic and phase diagram data have been critically assessed for all phases in the CrO-Cr₂O₃-SiO₂ and CrO-Cr₂O₃-SiO₂-Al₂O₃ systems from 298 K to above the liquidus temperatures and for oxygen partial pressures ranging from equilibrium with metallic Cr to equilibrium with air. All reliable data have been simultaneously optimized to obtain one set of model equations for the Gibbs energy of the liquid slag and all solid phases as functions of composition and temperature. The modified quasi-chemical model was used for the slag. The models permit phase equilibria to be calculated for regions of composition, temperature, and oxygen potential where data are not available.     

Phase diagrams and thermodynamics of the systems ZrO2-CaO and ZrO2-MgO

The partial phase diagrams of the systems ZrO₂-CaO and ZrO₂-MgO were determined using precision lattice parameter measurements in order to check uncertainties reported in the literature. The results are in general agreement with the previous investigations by Hellmann and Stubican [83HeI], Grain [67Gra], and Sim and Stubican [87Sim]. Enthalpies of formation of the fluorite cubic solid solution and the Ca₂6Zr₁₉O₄₄ ordered phase, with reference to the monoclinic zirconia and the periclase forms of CaO and MgO, were measured calorimetrically. Assessment of the thermodynamic properties of these two systems shows that it is appropriate to model the systems with a simple single cation sublattice model. The eutectoid of the cubic phase in ZrO₂-CaO, according to both the optimization and the experimental results, is located at 1412 ± 50 K and 16.2 ±1.0 mol% CaO and in the ZrO₂-MgO binary at 1678 ± 5 K and 13.1 ± 0.5 mol% MgO. The calculated phase diagrams are presented for comparison with the experimental results.     

Phase diagrams and thermodynamic properties of rare earth-bismuth systems

A survey is given of rare earth-bismuth phase diagrams and of crystallographic and thermodynamic properties of the intermetallic compounds occuring in the various rare earth-bismuth systems. Observed trends and regularities are briefly discussed. A more detailed investigation is presented for the Tm---Bi phase diagram.     

Thermodynamics and phase diagrams in the binary systems Na2O-SiO2, Na2O-GeO2, Na2O-B2O3, Li2O-B2O3, CaO-B2O3, SrO-B2O3, and BaO-B2O3

We applied our model to the enthalpy of mixing data of the binary systems Na₂O-SiO₂, Na₂O-GeO₂, Na₂O-B₂O₃, Li₂O-B₂O₃, CaO-B₂O₃, SrO-B₂O₃, and BaO-B₂O₃. The most stable composition in the liquid, that is where the enthalpy of mixing is most negative, is with a metal-oxygen ratio of 4 to 3, for monovalent metals (Na and Li) and 3 to 4 for divalent metals (Ba and Ca) in liquid silicates or borates. The same applies to the CaO-SiO₂, CaO-Al₂O₃, PbO-B₂O₃, PbO-SiO₂, ZnO-B₂O₃, and ZnO-SiO₂ systems. The oxygen to metal ratio, its constant value in various types of systems, reflects and describes the structure of the liquid. Using the analyzed enthalpies of mixing data and the available phase diagrams, we calculated the enthalpies of formation of the various binary compounds. The results are in excellent agreement with data in the literature that were obtained from direct solid-solid calorimetry.     

Correlations between phase diagrams and thermodynamic data for metal hydride systems

A series of correlations between the phase diagrams and enthalpic data are developed for metal hydride systems. The value of these correlations lies in their providing criteria for checking the consistency of the thermodynamic behavior for these systems. The correlations are illustrated using some experimental thermodynamic data and the accompanying phase diagrams for metal hydrides from the literature.     

Correlations between phase diagrams and thermodynamic data for metal hydride systems

A series of correlations between the phase diagrams and enthalpic data are developed for metal hydride systems. The value of these correlations lies in their providing criteria for checking the consistency of the thermodynamic behavior for these systems. The correlations are illustrated using some experimental thermodynamic data and the accompanying phase diagrams for metal hydrides from the literature.     

影响γ-Al2O3→α-Al2O3物相转变过程的因素研究

本文以拟薄水铝石为起始原料,采用XRD、SEM、TG/DTA等研究手段,研究了在γ-Al2O3→α-Al2O3相变过程中的影响因素,研磨、晶种、矿化剂等手段都可以促进相变过程的发生,这些因素对相转变过程的影响主要是降低相变过程的活化能,从而使γ-Al2O3在相对较低的温度下完成相变.     

B2O3-CaO、CaF2-CaO对LATS钢包渣的调质处理实验

为减少LATS合金化精炼浸渍罩粘渣,分别采用B2O3-CaO和CaF2-CaO作调质剂对钢包渣进行调质处理实验.调质后熔渣物性研究结果表明:两种调质剂都有效地降低了钢包渣的熔点和粘度.硫在渣-金属间分配平衡实验表明,调质后的钢包渣不会引起钢液回硫,而且可使钢中的硫含量进一步降低.     

Compilation of calculated phase diagrams in multicomponent metallic systems using a thermodynamic approach

The following is an updated version of the table that appeared as Appendix 1 of “Comparison of Methods for Thermodynamic Calculation of Phase Diagrams” inInternational Metals Reviews, Vol. 24, No. 1, p 20–53 (1979). Many of the articles cited in the table also contain data relevant to the component binary systems.     

Phase relationships in the systems RE2O3-Al2O3-SiO2 (RE = rare earth element, Y, and Sc)

A literature survey and recent results on phase relationships in the quasi-ternary systems RE₂O₃-Al₂O₃-SiO₂ are given. The investigated systems exhibit extended ternary solid solutions, RE_9.33+2x(Si_{1_x}Al_xO₄)₆O₂ (withx up to ~0.33) and/or RE₄Al_{2(1_X)}Si_2xO_9+x (withx up to ~0.3), which are based on the quasi-binary phases RE_9.33(SiO₄)₆O₂ and RE₄A1₂O₉, respectively. The former is encountered only in systems with laige RE³⁺ ions (e.g., La³⁺), whereas the latter is found in systems with small RE³⁺ ions (e.g., Yb³⁺); in systems with medium-sized KE³⁺ ions (e.g., Gd³⁺) both types exist Quasi-ternary compounds are known only in the La, Ce, and Sc systems. Severe discrepancies in reported ternary eutectic temperatures led to a need for their accurate redeteimination.     

Al_2O_3含量对Al_2O_3-Al复合涂层组织和摩擦磨损性能的影响

通过改变喷涂粉末中Al2O3和Al的比例,在AZ91D镁合金表面制备不同Al2O3含量的等离子喷涂Al2O3-Al复合涂层。对复合涂层的显微组织、硬度和摩擦磨损性能进行表征,研究Al2O3含量对涂层组织和磨损性能的影响。结果表明,涂层组织为带状Al2O3分布在致密的Al基体上,Al2O3内可见细微的片层结构,且层与层间存在一定的孔隙。复合涂层中Al平均硬度62HV,Al2O3平均硬度达1380 HV。摩擦磨损实验证实,复合涂层具有较小的摩擦系数和较低磨损量,大大改善了镁合金表面的抗磨损性能。涂层中Al2O3体积少于Al时,Al2O3增加使涂层的抗磨效果增强。涂层中Al2O3体积超过Al后,涂层的孔隙增多、涂层变脆,其耐磨损性能下降。     

阐述α-氧化铝相变机理和α相含量影响因素

介绍了高温煅烧氧化铝α相变的转换机理,并从流程和α相X光分析检测等方面对影响α相含量进行了阐述,表明合理的工艺对其α相含量有重要影响。     

煅烧时间对TiO2-Al2O3复合光催化材料性能的影响

研究500℃下煅烧不同时间对溶胶-凝胶法制备的TiO2-Al2O3复合材料的吸附性能和光催化性能的影响.经表征分析可知,所制备材料由锐钛矿型TiO2和非晶态Al2O3组成.随着煅烧时间的增加,样品的晶粒逐渐长大,但煅烧时间对样品颗粒的表面形貌影响不大,其表面形貌较为平坦.煅烧2.5h或3h所制得样品的比表面积较大.复合材料对甲基橙的吸附率在5％～8％之间,随煅烧时间的变化不大.经500℃煅烧3h制得的TiO2-Al2O3复合材料的光催化活性最佳,经紫外光照射90 min后可使甲基橙溶液总脱色率达95.2％.     

The phase diagrams and thermodynamics of the ZrO2-CaO-MgO and MgO-CaO systems

The phase diagram of the ZrO₂-CaO-MgO system was studied both experimentally and computationally. Using the newly developed isoplethal map method, the partial isotherms of the system at 1523,1573,1683, and 1773 K were determined with better accuracy than reported in the literature. The enthalpies of formation of the fluorite cubic structure, with reference to the monoclinic zirconia and the periclase CaO and MgO, were measured calorimetrically. With optimized binary data for the systems ZrO₂-MgO and ZrO₂-CaO, which were reported elsewhere, and the data for MgO-CaO briefly discussed in this paper, the thermodynamics and phase diagram data of the ternary system were assessed by means of computational optimization. Good agreement between the experimental and computational results were obtained. The liquidus surface was also predicted and compared with the available experimental results.     

The phase diagrams of the Sc---Sn and Sc---Pb systems

The phase diagrams of the Sc---Sn and Sc---Pb systems have been investigated using differential thermal analysis (DTA), metallographic analysis, X-ray diffraction (XRD) and electron microscopy.

The Sc-rich side of both systems (0–30 at.% Sn or Pb) has not been studied owing to the high melting temperatures of the corresponding alloys and contamination of the samples by the container material (Mo).

The two systems are very similar to one another; with tin, however, two more intermediate phases are formed. Sc₅X₃ and Sc₆X₅ compounds are isomorphous, Mn₅Si₃ and Ti₆Ge₅ types respectively. ScSn₂ is a new intermetallic compound with a new structure type. The impossibility of finding single crystals for XRD prevented the determination of the structure and then of the exact stoichiometry for ScSn which was assigned taking into account the results of DTA, XRD, optical and electronic microanalysis. Sc₅X₃, different from the other intermediate phases, shows appreciable solid solution range towards compositions richer in X.