Section Of Phase Diagram Research Articles

873 K Isothermal section of phase diagram for YFeTi ternary system

For Y-Fe-Ti ternary system, a ternary compound, Fe{sub 10.8}Ti{sub 1.2}Y, was observed by Mooij et al. in the alloys with composition Fe{sub 12{minus}x}Ti{sub x}y homogenized and equilibrated at 1123 K for 2--3 weeks. Additionally, a new ternary compound R{sub 3}(Fe,Ti){sub 29} (for R = Sm or Nd) has excited interest of research recently. The present work was also intended to determine whether or not this phase can exist for R = Y at the considered temperature range.

The cadmium-zinc phase diagram under high pressure

Phase relation of the Cd-Zn system at various pressures up to 7.0 GPa was determined by means of isobaric measurement of electrical resistance and in-situ X-ray diffraction analysis. The eutectic temperature and melting temperatures of cadmium and zinc increase under pressure with mean values of the slopes (ΔT/ΔP)(P=0-7 GPa) of 26°C/CPa, 48°C/GPa and 38°C/GPa, respectively. The eutectic composition moves toward Zn-rich phase from 26.6 at% Zn at atmospheric pressure to 58 at% Zn at 6.0 GPa. The maximum solubility of zinc in the α phase (hcp solid solution on the Cd-rich side) and that of cadmium in the β phase (hcp solid solution on the Zn-rich side) expand slightly under high pressure. Isobaric temperature-composition sections of the three-dimensional equilibrium phase diagram of the Cd-Zn system up to 7.0 GPa are constructed on the bagis or the results.

Analysis of the β′Ni2TiAl/βNiTi equilibrium in Ni-Ti-Al alloys by the cluster variation method

Abstract The cluster variation method with the Lennard-Jones potential, previously used to analyze the γ′(L1 2 Ni 3 Al)/γ(fcc Ni) equilibrium in Ni-Al base multicomponent alloys, was used to calculate the β′(L2 1 Ni 2 TiAl)/β (B2 NiTi) equilibrium phase boundaries in the Ni-Ti-Al system. Results are compared with the isothermal and vertical sections of the ternary phase diagram in the literature. The lattice misfit between β′ and β compound lattices, which is considered to play an important role for the formation of a rafted structure, passed through a minimum at 50%Ni, but was considerably larger compared to γ′/γ alloys. It is thus necessary to consider alloying addition for the optimization of high temperature properties of β′/β alloys by controlling the size and distribution of the β′ phase and the lattice misfit. © 1997 Elsevier Science Limited. All rights reserved

Identification of a novel gene, , as a primary response gene upregulated during seizure and LTP

The aim of this paper is to investigate the role of thermal path on the accuracy of gas hydrate phase equilibrium data using isochoric method. In this regard, methane hydrate equilibrium conditions have been typically determined using different heating paths – continuous and stepwise. The step-heating path, with proper size and duration of temperature increment, provided the most accurate data of methane hydrate phase equilibrium conditions compared with other experimental data available in literature. We have concluded that equilibrium step-heating path had the potential for determining reliable hydrate phase diagrams, irrespective of the present components in the system. Generally, the sufficient time given to each isothermal step is based on approaching a constant number of moles of gas phase through partial hydrate dissociation whereas the size of temperature increment is limited by the amount of gas encaged in hydrate cages.Moreover, the advantage of isochoric method for pure gas systems in utilizing a section of hydrate phase diagram instead of the distinctive condition, at which the last piece of hydrate disappears, is confirmed. Finally, the possibility of obtaining hydrate phase diagram of pure gas systems at arbitrary pressures was examined by purging the system before hydrate dissociation process.

Kinetic considerations about the successive nucleations of various aluminates in the BaCO 3-γ-Al 2O 3 reaction

Diffusion experiments using barium carbonate-alumina couples have been carried out. This work follows up a kinetic study previously published on the synthesis of BaAl 2O 4 from stoichiometric BaCO 3 + γ-Al 2O 3 powder mixtures, with formation of an intermediate compound [1]. In the current study, the formation of other barium aluminates is shown when the distances of diffusion greatly increase. After different annealing times, a complete isothermal cross section of the equilibrium phase diagram can be proposed.

Experimental study of ternary M-Zn-Se (M=W, Au, In, Ti) phase equilibria

Ternary phase equilibria in the systems M-Zn -Se(M = W, Au, In, Ti) are studied by X-ray diffraction on samples annealed in silica capsules and quenched. Four isothermal phase diagram sections are presented and discussed. Only in the In-Zn-Se system a ternary compound is present (ZnIn2Se4). The metals W, Au and In are in equilibrium with the II–VI semiconductor ZnSe, whereas Ti and ZnSe are not equilibrium. The particular feature of the large Zn-solubility in solid (Au) does not modify the (Au)-ZnSe equilibrium, in contrast to the related Au-Cd-Te system. Possible reactions at the metal/ZnSe interface in an open or closed environment are discussed based on the phase diagrams, and potential contact materials are indicated.

First-principles study of multiple order-disorder transitions in Cd2AgAu Heusler alloys.

The bcc-based Heusler alloys exhibit a series of order-disorder phase transitions as a function of temperature. The high-temperature phase is a disordered bcc solid solution, and the low-temperature phase is the Heusler structure. An intermediate ordered phase is also typically observed in real systems. A prototype cluster variation method (CVM) analysis is presented that shows that the relative stabilities of the Heusler and intermediate phases can vary continuously, depending on a fine balance between ordering tendencies in the constituent binary systems. Given these basic conclusions, a first-principles analysis of order-disorder transitions in ${\mathrm{Cd}}_{2}$AgAu was performed. A cluster expansion Hamiltonian was constructed based on a series of linearized muffin-tin orbital calculations in the atomic sphere approximation. CVM calculations were then performed in the ternary bcc tetrahedron approximation. In addition to the transition temperatures, long-range order parameters, and sublattice occupations for ${\mathrm{Cd}}_{2}$AgAu, an isoplethal section of the ternary phase diagram was also calculated. In general, agreement with experiment is excellent, given the first-principles nature of the calculation. This study clearly demonstrates the ability of first-principles statistical-mechanical calculations to treat complex ordering phenomena in ternary systems. \textcopyright{} 1996 The American Physical Society.

The phase equilibria in the quasi-ternary HgSeGa2Se3GeSe2 system

The seven polythermal sections of the quasi-ternary HgSeGa2Se3GeSe2 system were investigated using differential thermal, X-ray phase and microstructural analyses and microhardness measurement. New quaternary compounds were not found. Extended solid solutions on the basis of Ga2Se3 and HgSe have been established. The projection of the liquidus surface and the isothermal section of the HgSeGa2Se3GeSe2 phase diagram at 770 K over the whole concentration region have been constructed.

The SmAgAl system

The isothermal section of the SmAgAl phase diagram at 870 K over the whole concentration region has been determined using X-ray diffraction. Solubility of the third component in the binary compounds SmAg, SmAl 2 and Sm 3Al 11 and homogeneity ranges of the ternary phases Sm 2(Ag,Al) 17, Sm 1.6(Ag,Al) 17, Sm(Ag,Al) 5 and Sm(Ag,Al) 2 have been established. The existence of earlier reported ternary compounds SmAg 2.42Al 2.53 (DyAg 2.4Al 2.6 type) and Sm 1.6Ag 7.5Al 9.5 (Th 2Ni 17 type) has been confirmed and four new ternary compounds SmAg 1.46Al 0.54 (CeCu 2 type, a = 0.46560(8), b = 0.7237(1), c = 0.7951(1) nm, R = 0.063), SmAg 1.15Al 1.85 (PuNi 3 type, a = 0.55903(4), c = 2.6560(3) nm, R = 0.102), Sm 2Ag 10.9Al 6.1 (Th 2Zn 17 type, a = 0.9370(1), c = 1.3641(2), R = 0.120) and ∼ SmAg 3.7Al 1.1 (hexagonal structure of new type, a = 0.5407(2), c = 0.9253(2) nm) have been found.

Proof of schreine makers’ rule for general phase diagram sections

Following a proposal by Hillert, Schreinemakers$#x2019; rule is proven to apply in the general case to sections of phase diagrams of systems of any number of components.

Determination and calculation of the CdPbSn ternary phase diagram

Six vertical sections of the CdPbSn ternary phase diagram (Cd60wt.%Pb40wt.%Sn, Pb20wt.%Cd80wt.%Sn, Sn70wt.%Cd30wt.%Pb, Cd30wt.%Pb, Cd30wt.%Pb70wt.%Sn, Cd80wt.%Pb20wt.%Sn and Cd90wt.%Pb10wt.%Sn) were determined and calculated. The calculations agreed well with the experimental results. A complete liquidus projection of the CdPbSn system was also derived from the calculations.

The aluminum-zinc phase diagram under high pressure

Phase relations of the AlZn system at various pressures up to 7.3 GPa are investigated by means of isobaric measurement of electrical resistance and X-ray diffraction analysis. The liquidus, solidus, eutectic and eutectoid horizontals and the f.c.c. miscibility gap in the equilibrium phase diagram move toward higher temperature with increasing pressure. The solubility of zinc in the α 1 phase (f.c.c. solid solution on the Al-rich side) and aluminum in the β phase (primary solid solution of Zn) tends to decrease under high pressures. However, the compositions of the eutectic and eutectoid points are invariable. The existence of the α 2 phase (f.c.c. solid solution on the Zn-rich side) is confirmed at a pressure of 7.3 GPa by means of in situ high-pressure X-ray diffraction. An isobaric temperature-composition section of the three-dimensional phase diagram of the AlZn system at a pressure of 5.4 GPa is constructed on the basis of the results.

Calculation of Phase Equilibria and Ihermodynamic Properties of the Li - Na - H System

Available data for the phase diagram and equilibrium hydrogen pressures in the Na-NaH system were optimized to obtain equations for the Gibbs energies of the phases as functions of composition and temperature. Phase diagram data for the Li-Na system were similarly optimized. For the Li-LiH system, optimized Gibbs energy expressions were taken from the literature. The Gibbs energy of ternary liquid Li-Na-H solutions were calculated from these optimized binary Gibbs energies by means of a sublattice model in which the system is treated as a reciprocal ternary system Li-Na-LiH-NaH. Calculated equilibrium hydrogen pressures in the ternary system agree well with available data. Several calculated isothermal sections of the ternary phase diagram are presented

Phase stabilities in the AlCuRu system

Isothermal sections of the AlCuRu phase diagram at 500 and 800dgC have been determined for Al concentrations greater than 60 at.%. At 500°C, the icosahedral phase is not thermodynamically stable, whereas at 800°C it is stable over a fairly broad compositional region. The formation of the fci phase from the low temperature tetragonal phase is by a nucleation and growth process. The first-order transformation to the fci phase is endothermic, indicating that the fci phase is at a higher energy than the tetragonal phase.

The ytterbium-copper-aluminium system

The isothermal section of the YbCuAl phase diagram at 870 K over the whole concentration region has been constructed using X-ray structure and phase analysis. We have confirmed the existence of earlier reported ternary compounds: YbCuAl (ZrNiAl type) and YbCu 4Al 8 (CeMn 4Al 8 type); the previously reported compound YbCu 4Al proved to be a solid solution of aluminium in the binary compound YbCu 5 (CaCu 5). New ternary aluminides such as Yb 4(Cu 0.26Al 0.74) 33 (new structure type), Yb 2(Cu 0.57Al 0.43) 17 (Th 2Zn 17), Yb(Cu 0.85Al 0.15) 6 (YbMo 2Al 4) 7 Yb 6(Cu 0.74Al 0.26) 23 (Th 6Mh 23) and Yb(Cu 0.30Al 0.70) 3 (PuNi 3) have been prepared for the first time and their crystal structures have been determined. The limits of solid solutions of the binary compound YbCu 5 and the homogeneity ranges of the ternary phases Yb(CuAl) 12, Yb(CuAl) 17 and Yb(CuAl) 2 have been established.

Mobilities in cubic liquid crystals (“ringing gels”) determined by NMR self-diffusion measurements

Diffusion coefficients in the ternary surfactant system consisting of surfactant (tetradecyldimethylaminoxide, C 14DMAO), hydrocarbon (C 6H 12), and water have been determined by the pulsed field gradient spin-echo NMR method. Concentrations were varied along two sections of the ternary phase diagram. The transition from a micellar phase (L 1) that consists of spherical micelles into a cubic liquid crystalline phase (“ringing gel”) is studied as the volume fraction of the micelles is increased at constant hydrocarbon surfactant ratio. The mobility of the solvent, water, is only moderately decreased for this series of samples. In contrast, the diffusion coefficient of the hydrocarbon is decreased by two orders of magnitude, and the one of the surfactant by three orders of magnitude, when passing from the micellar phase into the cubic phase. In the micellar phase, the observed diffusive motion ( D ∼ 1–3 × 10 −11m 2 s −1) is due to transport of the micelles. This conclusion is reached from the fact that the diffusion coefficients of surfactant and hydrocarbon are equal, and approximately two orders of magnitude lower than that of the neat hydrocarbon liquid. In agreement with expectations, a linear decrease of the diffusion coefficient with the volume fraction of the micelles is observed. In contrast, the mobility of the micelles is strongly reduced in the cubic liquid crystal. The dynamics observed in the latter phase is due to two processes. Hopping of hydrocarbon molecules between neighboring micelles is characterized by a residence time of ∼100 μs, and diffusion coefficients of 3–5 × 10 −13 m 2 s −1. The exchange of surfactant molecules between the micelles occurs on a slower time scale (∼1 ms), with diffusion coefficients on the order of 3 × 10 −14 m 2 s −1.

The system YPO 4-Na 3PO 4-Na 4P 2O 7

The ternary system YPO 4-Na 3PO 4-Na 4P 2O 7 was investigated by differential thermal analysis, powder X-ray diffraction and microscopy in reflected light. Its phase diagram and isothermal section at room temperature were determined. The system contains two double phosphates which are formed at the 1:1 and 2:1 molar ratios of YPO 4 and Na 3PO 4, i.e. Na 3Y(PO 4) 2 and Na 3Y 2(PO 4) 3.

Constitution of the mantle. I. Phase relations in the FeOMgOSiO2 system at 10–30 GPa

P - T - x phase diagrams of the FeOMgOSiO 2 (FMS) system are calculated using the ideal solution model at 10–30 GPa and 1000–2000 K. A thermodynamic data base for minerals in the MgOSiO 2 and FeOSiO 2 systems is established by supplementing the calorimetric data for low-pressure phases and equations of state for all phases with data calculated from high-pressure synthesis experiments. The thermodynamic functions of virtual phases in the FeOSiO 2 system are evaluated. The topologies of calculated P - x sections of phase diagrams at 1273 K and 2000 K are in agreement with earlier experimental data. Univariant curves γ + St = Ilm + Mw, γ + Ilm = Pv + Mw + St intersect giving the nondegenerated invariant point (St + Mw + γ + Pv + Ilm) at T ≈ 1650 K, P ≈ 23 GPa and Fe/(Fe + Mg) ratios in the range 0.19–0.30. Univariant curves α + γ = β and Px + γ = β + St do not intersect in the calculated interval of P - T conditions. At temperatures higher than 1650 K, Ilm = Pv + γ + St and γ + St = Pv + Mw equilibria are stable. It is supposed that the disagreement between the earlier experimental phase diagrams is due to the experiments being carried out at temperatures above and below the invariant point.

Petrogenetic grids for metacarbonate rocks: pressure-temperature phase-diagram projection for mixed-volatile systems

Isothermal or isobaric phase diagram sections as a function of fluid composition (X F) are widely used for interpreting the genetic history of metacarbonate rocks. This approach has the disadvantages that: (1) the influence of a key metamorphic variable, either pressure (P) or temperature (T), is obscured; (2) the diagrams are inappropriate for systems that are not fluid-saturated. These problems are avoided by constructing phase-diagram projections in which the volatile composition of the system is projected onto a P-T coordinate frame, i.e., a petrogenetic grid. The univariant curves of such P-T projections trace the conditions of the invariant points of isothermal or isobaric phase-diagram sections, thereby defining the absolute stability of high-variance mineral assemblages, with and without a coexistent fluid phase. Petrogenetic grids for metacarbonate rocks are most useful for the study of regional metamorphism and for systems in which fluid composition has not been externally controlled. A calculated example of a P-T projection for the system CaO−MgO−SiO2−H2O−CO2 suggests that many assemblages (e.g., calcite +tale, enstatite+fluid, magnesite+tremolite, antigorite+diopside+dolomite, and calcite+forsterite+tremolite) in mixed-volatile systems have stability fields that make them useful as P-T indicators. Consideration of the principles governing projection topology demonstrates that the univariant curves around a fluid present invariant point cannot be oriented independently with respect to the direction of compositional variation in the fluid phase. This has the interesting predictive implication that if the direction of compositional variation along one univariant curve around an invariant point is known, then the direction of compositional variation along the remaining curves can be determined solely from topologic constraints. The same constraints can be applied to systems containing simple mineral solutions or melts in order to predict compositional variations.

The calculation of horizontal sections of high-pressure phase diagrams of the CdSnZn ternary system

A method for calculating ternary horizontal sections of the high-pressure phase diagram is described and applied to the CdSnZn system. Several horizontal sections of the high-pressure phase diagram of the system were calculated at different temperatures up to 700 K and different pressures up to 2.0 GPa. The liquidus projections of the system at a pressure of 2.0 GPa and at a temperature of 500 K are shown as examples.