First observation of aS C * -S A-TGBA multicritical point in a pure compound

High pressure experiments have been performed by thermobarometric analysis on two homologous (n=10 and 11) of the [3-fluoro-4((R) or (S)-methylheptyloxy) 4′-(4″-alkoxy-3″-fluorobenzoyloxy) tolans series, which both exhibit the TΓB_A phase. The character (first or/and second order) of the transitions involving the TGB_A phase are determined from thermobarograms. The pressure-temperature phase diagrams show that the TGB_A phase is stabilized under high pressure for the two compounds. Forn=11 an inducedS _A phase is observed under high pressures leading to the first experimental observation, on pressure-temperature phase diagram of pure compounds, of aS _C ^* -S _A-TGB_A multicritical point, previously predicted by the Renn-Lubensky theory.     

Theory of phase diagrams described by thermodynamic potentials with T d symmetry

Phase diagrams of crystals induced by irreducible representations with symmetry group \(L = \bar 43m\) (T _d ) are constructed within the phenomenological theory of second-order phase transitions. A model of the Landau thermodynamic potential is studied, state equations of all symmetry-conditioned phases are obtained, and general conditions for their thermodynamic stability are formulated. Equations for the boundaries of phase areas and lines of phase transitions are obtained for the fourth order of expansion of the potential via components of the order parameter. Some types of the collapse of the multicritical point of the phase diagram for the eighth order of potential expansion are studied using computer calculations. The possible existence of phase diagrams that contain one or more triple points and areas of existence of three and four phases is shown for the first time for the potentials with the above symmetry. Examples are given of crystals that undergo phase transitions in the considered symmetry of the order parameter.     

Determining scaling in known phase diagrams of nonionic microemulsions to aid constructing unknown

Microemulsions based on nonionic surfactants of the ethylene oxide alkyl ether type C_mE_n, have been studied thoroughly for around 30 years. Thanks to the considerable amount of published data available on these systems, it is possible to observe trends to make predictions of phase diagrams not yet determined. Strey and Kahlweit, and subsequently Sottmann and Strey, with coworkers have studied and published phase diagrams for systems with a fixed ratio of oil to water, varying the surfactant, the so-called Kahlweit fish-cut diagrams. Some properties of the phase diagrams can be scaled to become general and not system dependent. Here are shown two examples of scaling data from phase diagrams and the use of trends to determine phase diagrams, both inside and outside a dataset. The trends of microemulsions with fixed ratio of surfactant to oil, the so-called Lund-cut diagrams, are also investigated. The trends are used to determine a new phase diagram and this is compared with previously unpublished experimental data on C₁₂E₅-Octadecane-Water system. The scalings and trends make it possible to get good estimations of many of the important properties of the phase diagrams, both temperatures and surfactant concentrations of interest, by investigating one sample in the 3-phase region of the balanced fish-cut diagram.     

Mutual solubility between hexane and tri-<Emphasis Type="Italic">n</Emphasis>-butyl phosphate solvates of lanthanide(III) and thorium(IV) nitrates at various temperatures

The phase diagrams of binary liquid systems consisting of hexane and a tri-n-butyl phosphate (TBP) solvate of an Ln(III) (Ln = Nd, Gd, Y, Yb, Lu) or Th(IV) nitrate at various temperatures are considered. The diagrams show a field of homogeneous solutions and a two-phase field in which phase I is hexane-rich and phase II is rich in [Ln(NO₃)₃(TBP)₃] or [Th(NO₃)₄(TBP)₂]. The miscibility gap in the binary systems narrows with increasing temperature.     

Phase diagrams of systems SrF2(Y,Ln)F3. II. Fusibility of systems and thermal behavior of phases

The phase diagrams of 14 SrF₂(Y,Ln)F₃ systems are given, where Ln are all the lanthanides except Pm and Eu. The diagrams have been constructed for temperature intervals from 850°C to the melting points according to the thermal and X-ray analysis. The fusibility diagrams for 12 systems have been obtained for the first time. The oxygen content in the specimens before and after thermal treatment was checked. The thermal behavior of the three types of solid solutions has been studied: (1) with the fluorite-type defective structure and its derivatives; (2) with the defective structure of the lanthanum fluoride, and (3) α-YF₃(α-UO₃) types. Maxima reflecting a noticeable effect of thermal stabilization on the fluorite-type structure by the heterovalent isomorphous substitution have been found for the majority of systems (with Ln = LaHo). The Sr_1?xLn_xF_2+x nonstoichiometric fluorite phases are formed in all the systems. Similar maxima corresponding generally to irrational compositions are present on the fusibility curves of the Ln_1?ySr_yF_3?y nonstoichiometric phases with the LaF₃-type structure (tysonite). Tysonite solid solutions are in all the systems, too. Nonstoichiometric phases with the α-YF₃-type structure are formed in the systems with Ln = ErLu. They are decomposed in the process of cooling and are the most unstable. The structure of the phase diagrams in the regions adjacent to lanthanide trifluorides are determined by polymorphism and morphotropy of the above-named compounds. Changes in the thermal stability of the nonstoichiometric phases and double chemical compounds in the series of lanthanides have been observed. The SrF₂(Y,Ln)F₃ systems studied give examples of the formation of phases with the highest concentrations of point defects among all the known binary fluoride systems (up to 50 at.%). The thermal stabilization effect of the nonstoichiometric phases with the fluorite structure results in the fact that the series of the two-component compositions is melted at considerably higher temperatures as compared with scandium fluoride, the most refractory single-component fluoride compound. This effect leads to formation of tysonite-type solid solutions with melting points exceeding 1500°C (mp of LaF₃—the most refractory fluoride material with tysonite-type structure).     

Phase diagrams with critical and tricritical liquid phase solution points in a ternary system

Critical phenomena of liquid phase stratification in ternary systems are considered. Models of the T-x ₁-x ₂ phase diagrams with critical and tricritical liquid solution points and isothermal diagrams over the corresponding interinvariant intervals are given.     

Twist-grain-boundary phase diagrams in chiral liquid crystals

The experimental phase diagrams of several chiral systems are compared with a theoretical diagram based on the chiral Chen-Lubensky model, which predicts at least two kinds of twist-grain-boundary phase, TGBA and TGBC. Also shown for comparison are typical nonchiral phase diagrams that exhibit a nematic-smectic A-smectic C multicritical point. Several aspects of experiment and theory agree, but there appear to be common experimental features that differ from those predicted by current theory.     

The investigation of sodium titanates by the hydrothermal reactions of TiO2 with NaOH

The hydrothermal reactions of TiO₂ with NaOH were performed in the molar range of Na₂O from 0 to 30% between 250 and 530°C. The compounds obtained were TiO₂ (rutile, brookite, and anatase), Na₂O·nTiO₂ (n = 3, 4, 6, and 9) and Na_xTiO₂, the formation ranges for which are shown in a reaction diagram. The roles of water in this hydrothermal system are investigated, to discuss the differences among the known and the present reaction diagrams and to raise a reliability of diagrams. From the present reaction diagram, phase relations in the system TiO₂Na₂O are estimated taking account of direct or indirect actions of hydrothermal water on solid phases.     

CO2 capture properties of M-C-O-H (M=Li, Na, K) systems: A combined density functional theory and lattice phonon dynamics study

We have computed the phase diagrams for multi-component M-C-O-H (M=Li, Na, K) systems using first-principles density functional theory complemented with lattice phonon calculations. We have identified all CO₂ capture reactions that lie on the Gibbs free energy convex hull as a function of temperature and the partial pressures of CO₂ and H₂O. Our predicted phase diagrams for CO₂ capture reactions are in qualitative and in some instances quantitative agreement with experimental data. The Na₂CO₃/NaHCO₃ and K₂CO₃/KHCO₃ systems were found to be the most promising candidates of all those we investigated for both pre- and post-combustion CO₂ capture. Overall, we show that our calculation approach can be used to screen promising materials for CO₂ capture under different conditions of temperature and pressure.     

Breakup promotion of deformed EPDM droplets by the migration of nanoparticles during extrusion

The effect of migration of calcium carbonate (CaCO₃) nanoparticles on the breakup dynamics of Ethylene-Propylene-Diene Monomer (EPDM) droplets in Polypropylene (PP) matrix during melt extrusion was investigated in situ. The breakup process of EPDM droplets was sped up dramatically when the migration of CaCO₃ nano-particles from dispersed phase to matrix was introduced to PP/EPDM melts. It was found that both the total breakup time and the shape stability of slender EPDM droplets decreased with the increase of CaCO₃ concentration. Both the maximum value in equivalent diameter d and aspect ratio AR of EPDM droplets were also reduced by increasing the composition of CaCO₃ nanoparticles. Results were discussed in consideration of interfacial tension and migration of CaCO₃ nanoparticles. Reduction in interfacial tension is mainly responsible for the improved breakup process in the two-step composites with CaCO₃ nanoparticles (<2 wt%). Higher composition of CaCO₃ (≥2 wt%) induced the CaCO₃ aggregates in the EPDM phase. These aggregates acted as stress concentration when the EPDM droplets break up.     

PTX phase equilibrium study of new solid solution systems,Cd1−xMxS (M = Mg,Ca, Sr)

Pressure, temperature, and composition phase equilibrium diagrams of new solid solution systems of the Cd_1?xM_xS (M = Mg, Ca, Sr) type were investigated using the quenching method. The stable region for the rock-salt-type phase is widely extended toward the high-temperature/low-pressure region by substituting 10–20 mole% of Cd with Ca or Sr. Temperature and composition phase diagrams for each solid solution system were obtained at 2 GPa. The rock-salt-type phase stability is discussed in view of these phase relations.     

Étude experimentale et théorique de la polarisation des PZT durs dopes au niobium

This paper deals with phase transitions of niobium-doped PZT ceramics. Phase diagrams of PbZr_1?xTi_xO₃ + yNb₂O₅ for x = 0,035 and 0,045 with 0 < y < 0,01 are given. An apparatus for remnent polarization measurement is described and experimental conditions are specified. Experimental results are interpreted with the help of a modified molecular field theory in which the molecular field coefficient is supposed to be a function of electric polarization. A discussion on phase transition order and on the theory validity is undertaken.     

The stability of the perovskite-type zirconium tungsten bronze ZrxWO3

It has been found that a perovskite-related zirconium tungsten bronze Zr_xWO₃ (with 0 < x ? 0.08) forms readily at temperatures between 973 and 1573° K. Prolonged heating causes the bronze to decompose to other oxide products at all the temperatures investigated. These results are summarized in phase diagrams. Possible reasons for the decomposition of the bronze are discussed.     

Phase Separation in the Systems Constituted by Tetradecane (Hexane,Decane), Tri-n-Butyl Phosphate,and Cerium(III) Nitrate Solvate with Tri-n-Butyl Phosphate

Phase diagrams of ternary liquid systems constituted by tetadecane (hexane, decane), tri-n-butyl phophate, and cerium(III) nitrate solvate with tri-n-butyl phosphate Ce(NO₃)₃(TBP)₃ with phase separation into liquid phases I and II were studied at 298.15 K. Phase I is enriched in the hydrocarbon diluent, and phase II, in Ce(NO₃)₃(TBP)₃. The distribution of components between phases I and II was considered.     

Thermal analysis for generating phase diagrams of systems alkali metal chloride/divalent metal chloride

After a historical survey of the application of differential thermal analysis (DTA) for the generation of phase diagrams, particularly those of pseudobinary halide systems, the authors' research work on the systems ACl/MCl₂ (A = NaCs) is reported. In addition to DTA measurements the thermodynamic properties of the ternary compounds A_nMCl_n+2 are investigated by solution calorimetry and EMF measurements dependent on temperature with a newly developed galvanic cell for solid electrolytes. This method is also a useful tool for elucidating phase diagrams, especially for reactions occurring in the solid state.     

Magnetic susceptibility and the spin-glass transition of Cd1−xMnxS and Zn1−xMnxS at low temperatures

Low-field magnetic susceptibility of the diluted magnetic semiconductors Cd_1?xMn_xS and Zn_1?xMn_xS was measured between 4.2 and 30 K for the Mn concentration range 0.25 < x < 0.40. When x > 0.25, both of these ternary systems show a spin-glass transition in the above temperature range, as evidenced by a somewhat rounded cusp in the susceptibility and by the presence of irreversible effects. Because these materials are insulators at low temperatures, and the interactions between the Mn ions are only antiferromagnetic, the observed spin-glass behavior is attributed to frustration inherent in the hcp lattices of these compounds. The phase diagrams for the boundary of the paramagnetic and the spin-glass phases are presented for the two alloy systems, and the difference between the two phase diagrams is discussed.     

Calorimetric determination of equilibrium phase diagrams of inorganic systems

Calorimetric isobaric determination of the heat involved during mixing processes gives the concentration dependence of the enthalpy of mixing ΔH_M = F(x) and also, under particular conditions, some liquids concentrations of the phase diagram.For some simple typical diagrams (with a eutectic point or miscibility gaps, or a definite compound etc.) direct calorimetric experiments at many temperatures give the liquidus (e.g. NaBrNaNO₃, KBrKNO₃, NaBKNO₃, KBrNaNO₃, GaHg, GaSb).For more complicated or multicomponent systems, the setting up of the equilibrium phase diagram needs both experimental measurement and thermodynamic calculations (e.g. GaInSb).     

Continuous phase viscosity influence on maximum diameters of poly(styrene‐divinylbenzene) beads prepared by suspension polymerization

The influence of the continuous phase viscosity (μ_c) on the diameter of styrene‐divinylbenzene polymer beads was studied over a large range of viscosities at constant dissipated power. This study was based on the inertial breakup and viscous shear breakup theories for a stirred dispersion. These two theoretical models were compared with an experiment for the two highly viscous agents sucrose and acacia gum [dispersed and continuous phase viscosities (μ_d, μ_c) = 10⁻³ < μ_d/μ_c < 1]. We found that the maximum diameters of the polymer beads could not be described by an inertial breakup. The maximum diameters were in good agreement with a viscous shear breakup model for the two viscous agents in turbulent and semilaminar flows. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 201–210, 2001     

Phase equilibria and crystal chemistry of the R-Cu-Ti-O systems (R=lanthanides and Y)

As part of the study of interaction of the Ba₂RCu₃O_6+z (R=lanthanides and Y) superconductor with SrTiO₃ buffer, phase equilibria of the subsystem, R₂O₃-TiO₂-CuO (R=Nd, Y, and Yb), have been investigated in air at 960 °C. While the phase relationships of the two phase diagrams with smaller R (Y and Yb) are similar, substantial differences were found in the Nd₂O₃-TiO₂-CuO system, partly due to different phase formation in the binary R₂O₃-TiO₂ and R₂O₃-CuO systems. R₂CuTiO₆ and R₂Cu₉Ti₁₂O₃₆ were the only ternary phases established in all the three diagrams. R₂Cu₉Ti₁₂O₃₆ belongs to the perovskite-related [AC₃](B₄)O₁₂ family which is cubic Im3. Depending on the size of R³⁺, R₂CuTiO₆ crystallizes in two crystal systems: Pnma (R=La-Gd), and P6₃cm (R=Dy-Lu). The structure and crystal chemistry of the Pnma series of R₂CuTiO₆ (R=La, Nd, Sm, Eu, and Gd) are discussed in detail in this paper. Patterns for selected members of R₂CuTiO₆ have also been prepared and submitted for inclusion in the Powder Diffraction File (PDF).     

Phase behaviors of Gemini cationic surfactants/n-butanol/water systems

Phase diagrams for ternary system of the Gemini cationic surfactants, N,N-long chain alkyl-2-hydroxyl-N,N,N,N-tetramethyl diammonium dichloride (G_nCl₂) with butanol and water have been drawn based on experimental data at 25 °C. The phase diagrams show that L phase and different liquid crystalline phases are existent in the ternary system at different components. Electric conductivity of the L phase has been studied. Small-angle X-ray scattering (SAXS), ²H (deuterium) quadrupolar splitting (²H NMR) and the polarizing-light microscope were employed to confirm the characteristic texture structures and the microstructure of three different liquid crystalline phases.