Binary System 4MnO·Nb_2O_5-SiO_2—One of the Binary Sections in the Ternary System MnO-Nb_2O_5-SiO_2

1.IntroductionAs mentioned in our previous paper[1],it is important to study the phase diagram ofthe system Nb_2O_5-MnO-SiO_2.The newcompound 4MnO·Nb_2O_5 has been ascer-tained in the binary system MnO-Nb_2O_5[1].Then,there are three stable compounds     

Binary System MnO-Nb_2O_5

The phase diagram of the binary systemMnO-Nb_2O_5 was studied by means of the differentialthermal analysis(DTA),X-ray diffraction analysis andscanning electron microscopy(SEM).Thermodynamic da-ta of the new compounds 4MnO·Nb_2O_5 andMnO·Nb_2O_5were found as follows:4MnO·Nb_2O_5:t_m=1398±2℃△H_m=129000(J/mol)△S_m=77(J/mol,K)△G_m~o=129000-77T(J/mol)MnO·Nb_2O_5:t_m=1499±2℃△H_m=86940(J/mol)△S_m=49.6(J/mol,K)△G_m~o=86940-49.6T(J/mol)The eutectic parameters for the system are given below:t_(E1)=1383±3℃ N_(E1(MnO))=0.896t_(E2)=1312±2℃ N_(E2(MoO))=0.713t_(E3)=1400±4℃ N_(E3(MnO))=0.231     

Phase Stability, Kinetic Diagrams and Diffusion Path in High Temperature Oxidation of Binary Solid-Solution Alloys

The phase diagrams of ternary systems involving two metal components and one oxidant are considered first, the limitations to their use is discussed in relation to the high temperature oxidation of binary alloys. Kinetic diagrams,which are useful to predict the conditions for the stability of the two mutually insoluble oxides as the external scale, are then calculated on the basis of thermodynamic and kinetic data concerning both the alloys and the oxides, assuming the validity of the parabolic rate law. A combination of the two types of diagrams provides a more detail information about the oxidation behavior of binary alloys. The calculation of the diffusion paths, which relate the oxidant pressure to the composition of the system in terms of the alloy components both in the alloy and in the scale during an initial stage of the reaction in the presence of the parabolic rate law, is finally developed.     

Thermodynamic Assessment of the ZrO2—CeO2 and ZrO2—CeO1.5 Binary System

An optimal set of thermodynamic parameters of the ZrO2-CeO1.5 system has been obtained using phase diagram data by modern CALPHAD (CAL culation of PHAse Diagrams) technique.The liquid and other solid solution phases were regarded as substitutional solution.The ordered ZrCe2O7 phase was treated as a stoichiometric compound.The ZrO2-CeO2 system has been re-optimized with new reference state.A comparison between the ZrO2-CeO2 system and ZrO2-CeO1.5 system has been made through calculation.With the calculation, the experimental information is well reproduced and a good agreement is obtained.     

Phase Transformations in the Y2Cu2O5–BaCuO2 System

The sequence of phase transformations in the Y₂Cu₂O₅–BaCuO₂ pseudobinary system was studied during heating and cooling in the range 1170–1310 K. The results demonstrate that the reaction zone in BaCuO₂/Y₂Cu₂O₅ diffusion couples consists of BaCuO₂/YBa₂Cu₃O_{7 –} /Y₂BaCuO₅/Y₂O₃/Y₂Cu₂O₅ layers, corresponding to the sequence of chemical changes during YBa₂Cu₃O_{7 –} crystallization between 1170 and 1220 K. In the range 1260–1310 K, BaCu₂O₂ is formed. During cooling of a Y₂Cu₂O₅ + 4.3BaCuO₂ mixture, YBa₂Cu₃O_{7 –} crystallizes in a wide temperature range, between 1240 and 1190 K. The process depends on the presence of BaCu₂O₂ on the surface of Y₂BaCuO₅ grains in the high-temperature solution and the oxygen supply from the gas phase.     

Stable and Metastable Phase Equilibria in the Bi2O3–BiPO4 System

The stable and metastable phase equilibria in the Bi₂O₃–P₂O₅ system were studied in the range 0–50 mol % P₂O₅ by differential thermal analysis and x-ray diffraction. The results were used to construct the corresponding phase diagrams. In the equilibrium state, the system contains one sillenite phase with Bi₂O₃ : P₂O₅ = 12 : 1 and four other bismuth phosphates (2 : 1, 3 : 1, 5 : 1, and 1 : 1). In a metastable state, resulting from solidification of metastable melts, there exist * solid solutions (0–25 mol % P₂O₅) based on the high-temperature form of Bi₂O₃. At lower temperatures, the * phase transforms eutectoidally into the metastable phase, which has the same structural basis as the high-temperature solid solutions. At room temperature, the phase exists in a narrow composition range around 15 mol % P₂O₅. At lower P₂O₅ contents, the * phase decomposes at 868 K by a monotectoid reaction to form a mixture of the metastable and phases. The phases 3Bi₂O₃ · P₂O₅ () and 2Bi₂O₃ · P₂O₅ (), melting incongruently at 1193 and 1223 K, respectively, appear in both the equilibrium and metastable phase diagrams.     

Calculation of the Quasiternary Systems:Si_3N_4-Y_2O_3-SiO_2,Y_2O_3-SiO_2-BeO and Y_2O_3-Al_2O_3-BeO

Based on the thermodynamic model of Kaufman for the calculation of quasibinary and quasiternary system, numerical method for the calculation of stable equilibrium is developed and thermodynamic data of undefined phases are discussed in this work for several ceramic systems.The calculated isothermal sections in Si3N4-Y2O3-SiO2 system meet well with other previous calculated phase diagrams and experimental results. The diagrams in Y2O3-SiO2-BeO and Y2O3-Al2O3-BeO systems are calculated for the approach of prediction.     

Precise Determination of the MgAlON/(AlN+MgAlON) Phase Boundties in the MgO-AlN-Al2O3 Ternary System at 1600℃ and 1700℃

The accurate phase boundary of MgAlON/(AlN MgAION) in MgO-AlN-Al2O3 ternary system, has not been determined precisely so far. In the present study, the lattice parameters of MgAION solid solution with various compositions were determined precisely with X-ray powder diffraction. According to the relationship between the lattice parameters of MgAION solid solution and the contents of AIN and MgO, the phase boundaries of MgAION/(AIN MgAION) in MgO-AIN-Al2O3 ternary system at 1600℃ and 1700℃ were precisely determined.     

Precise Determination of the MgAlON/(AlN+MgAlON) Phase Boundries in the MgO-AlN-Al2O3 Ternary System at 1600℃ and 1700℃

The accurate phase boundary of MgAION/(AIN+MgAION) in MgO-AIN-Al2O3 ternary system, has not been determined precisely so far. In the present study, the lattice parameters of MgAION solid solution with various compositions were determined precisely with X-ray powder diffraction. According to the relationship between the lattice parameters of MgAION solid solution and the contents of AIN and MgO, the phase boundaries of MgAION/(AIN+MgAION) in MgO-AIN-AI2O3 ternary system at 1600℃ and 1700℃ were precisely determined.     

Thermodynamic Properties of Melts and Phase Equilibria in the Copper–Zirconium System

The vapor composition over and thermodynamic properties of Cu–Zr melts (5.1–85.0 at. % Zr) are studied by Knudsen cell mass spectrometry between 1191 and 1823 K. The data set obtained comprises more than 1100 activity values for various compositions and temperatures. The thermodynamic behavior of Cu–Zr melts is described in terms of the associated-solution approach with an accuracy no worse than the experimental accuracy. The melts are shown to contain two molecular species: CuZr and Cu₂Zr. The contributions of different types of chemical bonding to the Gibbs energy and enthalpy of formation of Cu–Zr melts are asymmetrical and shifted from the equiatomic composition in opposite directions: the extremum of covalent bonding is shifted to the Cu-rich side, while metallic bonding is more significant in Zr-rich alloys. The rapid temperature variation of covalent bonding leads to a large excess heat capacity C _p ^E of the melts and a negative excess entropy _f S ^E, which rapidly drops with decreasing temperature. It is shown that not only C _p ^E and _f S ^E but also their temperature variations are governed by the parameters of association reactions and depend more strongly on the entropy than on the enthalpy of complex formation. This indicates that, in the general case, the glass-forming capabilities of melts are independent of the interparticle interaction and accounts for the pronounced tendency of Cu–Zr melts toward amorphization.     

Phase Relations in the NiFe2O4–NiCr2O4–CuCr2O4System

The phase relations in the NiFe₂O₄–NiCr₂O₄–CuCr₂O₄system were investigated experimentally and theoretically. X-ray diffraction data were used to construct the phase diagram of the system and elucidate the structural mechanisms of the transitions from the cubic spinel structure to the tetragonal (I42d, c/a< 1 and I4₁/amd, c/a> 1) and orthorhombic (Fdd2) structures.     

Stable and Metastable Phases within the GeO2-Rich Part of the Binary PbO–GeO2 System

Glasses of composition (1-x)PbO · xGeO₂ with 0.50 x 1.00 were produced by melt quenching. Aliquots of each sample were thermally treated in air for various times at 660°C and then characterized by X-ray powder diffraction (XRPD) and differential thermal analysis (DTA). The XRPD patterns of devitrified samples show the presence of one or more crystalline phases, depending on x. For 0.50 x 0.75, short treatments (2 h) resulted in the presence of monoclinic PbGeO₃, accompanied by phases of PbGe₄O₉ stoichiometry. On the contrary, prolonged thermal treatments (360 h) produced a slight decrease in the intensity of the XRPD peaks of the PbGeO₃ phase and the transformation of the remaining material into orthorhombic PbGe₃O₇. For 0.80 x 0.95, short treatments (2 h) resulted in the formation of hexagonal GeO₂, accompanied by orthorhombic PbGe₃O₇ and by PbGe₄O₉ phases. In this case, prolonged thermal treatments (360 h) do not affect strongly the XRPD patterns.     

Non-Fermi Liquid Regimes and Superconductivity in the Low Temperature Phase Diagrams of Strongly Correlated d- and f-Electron Materials

Standard models for simple metals and insulators often fail for systems based on elements with unstable d- or f-electron shells, where strong electronic correlations can generate new and unexpected states of matter. Such a scenario can often be induced when a magnetic phase transition is tuned to absolute zero temperature by an external control parameter such as chemical composition, pressure or magnetic field. At the resulting quantum critical point (QCP), emergent phenomena, such as unconventional superconductivity and novel magnetic phases are frequently observed. The temperature and energy dependences of the physical properties are also found to deviate from expectations for a simple Fermi liquid. This “non-Fermi-liquid” (NFL) behavior is commonly manifested as weak power laws and logarithmic divergences in the physical properties at low temperatures and is often found in a V-shaped region near a QCP, which has become the “classic” QCP phase diagram. However, there is also a growing number of materials where the NFL behavior either occurs far away from the QCP, within an ordered phase, or may not be associated with any putative QCP. Thus, after nearly 20 years of research, it remains unknown whether NFL physics is universal, or if a multitude of unique subclasses exist. In this article, we review research that has primarily been carried out in our laboratory on systems that exhibit NFL behavior that does not conform to the “classic” QCP scenario.     

Thermo dynamic Assessment and Microstructure of the ZrO_2-CeO_2-Al_2O_3 System

The ZrO2-CeO2-AI2O3 system has been assessed with the CALPHAD (Calculation of Phase Diagrams) technique using the PARROT procedure. The experimental information on the ZrO2-AI2O3, AI2O3-CeO2 systems as well as the isothermal sections of the ternary system at 1673 K and 1873 K is well reproduced. According to the assessed isothermal section at 1723 K, no alumina dissolves into the tetragonal zirconia phase. Specimens with different alumina content are fabricated from commercial 12 mol pct CeO2-stabilized ZrO2 powder (12Ce-ZrO2). The thermodynamic properties are consistent with the observed microstructure, which present a combination of tetragonal phase and alumina grains.     

Phase Relations in the Li–V2O5–Cu System at 600°C and Cathodic Properties of Cu x V2O5

The phase relations in the Li–V₂O₅–Cu system at 600°C are studied by x-ray diffraction. The existence of the known vanadium bronzes M _x V₂O₅ (M = Li, Cu) is confirmed, and the composition ranges of the related solid solutions are determined. -Li _x V₂O₅ (0.22 x 0.49) and -Li _x V₂O₅ (0.88 x 1.0) are shown to dissolve Cu, forming Li _x Cu _y V₂O₅ solid solutions with y = 0.72 – 1.48x and y = 0.58 – 0.18x, respectively. Cu _x Li _y V₂O₅ solid solutions (y= 0.51 – 0.76 x) are only obtained from -Cu _x V₂O₅ (0.24 x 0.67). -Li _x V₂O₅ and -Cu _x V₂O₅ form a continuous series of solid solutions. The cathodic properties of Li–V₂O₅–Cu materials in high-temperature pulsed lithium batteries are investigated.     

Effect of Phosphates on the Metal Ion Activated Surface Complexes at the SiO_2-H_2O Interface and in Quartz Deactivation in Flotation System

The complexation of phosphates in thequartz-metal ion-H_2O-oleate system was studied.Computer assisted calculations with the aid of theadvanced program SOLGASWATER and knownequilibrium constants were used to evaluate themechanism,The calculation results revealed that inthe presence of a certain amount of phosphates,metal ions adsorbed at the quartz-H_2O interfacewill be transferred into solution.Thus the competi-tion for metal ions between phosphates and thequartz surface leads to surface deactivation and re-duced floatability.Various distribution diagramsclearly demonstrate the change of surfacecomplexation as a function of added phosphateconcentration.The deactivation products were alsoevaluated.     

Phase Relations in the BaO · 2B2O3–La2O3 · 3B2O3 System

The BaO · 2B₂O₃–La₂O₃ · 3B₂O₃ join of the ternary system BaO–La₂O₃–B₂O₃ is studied using differential thermal analysis, x-ray diffraction, and density measurements. The join is shown to be pseudobinary, with eutectic phase relations. In the composition range 5–99.8 mol % La₂O₃ · 3B₂O₃, glassy materials are obtained, which seems to be associated with the existence of the congruently melting compound BaO · La₂O₃ · 5B₂O₃.     

Effect of Cd Substitution for Bi on Superconductivity of the Bi-2201 Phase in the Bi—La—Ca—Cu—O System

A series of the Bi-2201 samples with the nominal composition of (Bi_2–x Cd _x )La_0.7Ca_1.3CuO _z has been synthesized and effect of Cd substitution for Bi on the superconductivity has been investigated. As a result, it is found that almost single phase samples are obtained for a considerable wide composition of 0.0 x 0.8, their crystal structures have a tetragonal or a pseudotetragonal symmetry in the whole composition range, and the sample unexpectedly changes from superconductor to semiconductor by little Cd-substitution of about 0.1. The semiconducting samples show a temperature dependence of the resistivity suggesting that the transport process is followed by a three-dimensional variable range hopping conduction.     

Measurement of Vapor–Liquid Equilibrium for the DME + Diisopropyl Ether Binary System and Correlation for the DME + CO<Subscript>2</Subscript> + Diisopropyl Ether Ternary System

Vapor–liquid equilibrium (VLE) data have been measured with a static-type VLE apparatus for the dimethyl ether (DME)–diisopropyl ether (DIPE) binary system at five temperatures within the range from 293.04 K to 352.70 K. An isothermal correlation for the experimental data has been carried out based on the Peng-Robinson equation of state. The regressed binary interaction parameters were used to estimate VLE for the DME–CO₂–DIPE ternary system at 298.15 K. From the study, it is demonstrated that DIPE is an excellent absorbent for separation in the DME synthesis process from syngas.