Phase diagram study of CaBr2–LiBr system using DTA

The phase diagram of binary LiBr–CaBr₂ system was investigated using differential thermal analysis (DTA) between room temperature and 800 °C. From the DTA results obtained over the entire range of composition from pure LiBr to pure CaBr₂ in steps of ~5 mol%, the phase diagram was constructed and is reported here. The results indicated the possible existence of a compound at 50 mol% LiBr, namely, LiCaBr₃. The compound undergoes peritectic decomposition at 552 °C. The system shows a eutectic reaction at 532 °C between this compound and LiBr phase, and the eutectic composition is close to 80 mol% LiBr. The compound LiCaBr₃ decomposes into CaBr₂ and LiBr phases below 272 °C. Co-existing phases in different phase fields are characterized by X-ray diffraction analysis.     

Phase diagram of the Sn–P system

Journal of Thermal Analysis and Calorimetry - The T–x diagram of the Sn–P system was studied by differential thermal analysis, X-ray phase analysis and local X-ray spectral...     

Phase diagram of ZnAs2–MnAs system

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Phase diagram and dissolution studies of the fenofibrate–acetylsalicylic acid system

Enhancement of the dissolution rate of poorly soluble compounds through the formation of drug–drug eutectics was investigated using fenofibrate and acetylsalicylic acid. Solid–liquid equilibria in the system under study were investigated by differential scanning calorimetry (DSC). The phase diagram for the whole range of compositions was constructed. In addition, existence of a metastable polymorph of fenofibrate has been confirmed. The investigation has revealed that acetylsalicylic acid and fenofibrate form a simple eutectic mixture containing 0.958 mol fraction of fenofibrate at the eutectic point. Dissolution rate improvement of fenofibrate correlated with the phase diagram. The amount of fenofibrate released from the solid dispersions that contained fenofibrate as the eutectic mixture with acetylsalicylic acid was at least threefold higher compared to untreated fenofibrate.     

Phase diagram and crystal chemistry of the La–Ca–Co–O system

The phase diagram of the La–Ca–Co–O system at 885 °C in air has been determined. The system consists of two materials that have interesting thermoelectric properties, namely, the misfit layered thermoelectric oxide solid solution, (Ca,La)₃Co₄O₉, and Ca₃Co₂O₆ which consists of 1D chains of alternating CoO₆ trigonal prism and CoO₆ octahedra. The reported La₂CaO₄ and the Ca-doped (La,Ca)₂CoO_4−z phases were not found at 885 °C. As a result of the absence of these phases, the phase diagram is significantly different from that reported at 1100 °C. Small solid solution regions of (La_1−xCa_x)₂O_3−z (0 ≤ x ≤ 0.08), (Ca_1−xLa_x)₃Co₄O₉ (0 ≤ x ≤ 0.07), and (La_1−xCa_x)CoO_3−z (0 ≤ x ≤ 0.2) were established.     

Phase state diagram of a poly(amic acid)–solvent–nonsolvent system

Phase behavior and structure formation was studied using optical interferometry, nephelometry, and refractometry in the polymer–solvent–nonsolvent system for DMF solutions of two poly(amic acids): based on 3,3′,4,4′-benzophenonetetracarboxylic acid dianhydride and meta-phenylenediamine (PAA-1) and pyromellitic acid dianhydride and 4,4′-oxydianiline (PAA-2). Distilled water and its mixtures with DMF were used as a nonsolvent. According to the results of the study, isothermal cross sections of the phase state diagram in the threecomponent system were plotted, the position of the critical point, the spinodal, and the conodes were determined, the movement of the figurative points in the system was traced depending on the nonsolvent composition.     

Phase diagram of the Pr–Mn–O system in composition–temperature–oxygen pressure coordinates

The phase relations in the Pr–Mn–O system were studied by the static method at lowered oxygen pressure in combination with thermal analysis and high-temperature X-ray diffraction. The equilibrium oxygen pressure in dissociation of PrMn₂O₅ and PrMnO₃ was measured, and the thermodynamic characteristics of formation of these compounds from elements were calculated. The Р–Т–х phase diagram of the Pr–Mn–O system was constructed in the “composition–oxygen pressure–temperature” coordinates.     

Detailed study of a two component smectic 4TPB–8OCB system with a nematic gap. Phase diagram and viscosity study

Abstract

The phase diagram of a two component system composed of two smectic compounds: 4-octyloxy-4′-cyanobiphenyl (8OCB) and 4-isothiocyanatophenyl 4-butylbenzoate (4TPB) was investigated. Three Miesowicz viscosity coefficients η₁, η₂, η₃ and the refractive indices at different temperatures as well as the enthalpies of the phase transitions were measured. It was stated, that the properties of the induced nematic phase, for example, the nematic phase existing between two smectic regions, are the same as the ones observed in the case of low viscosity nematic mesogens.     

Phase equilibrium diagram of the system MnCrO

A hypothetical oxygen pressure-composition phase diagram and a projection of the oxygen pressure-temperature-composition diagram on the composition triangle were constructed from phase equilibria in the system MnCrO on the basis of the data available in literature. The temperature-composition phase equilibrium diagram of this same system in air was specified. Isomorphism of solid solutions with spinel and hausmannite structure and their intertransformation was studied. Two chemical compounds, MnCr₂O₄ and Cr₄Mn₂₈O₄₈, are supposed to exist in the system.     

Phase diagram of an iodine-potassium iodide-water-ethanol system at 25°C

Phase equilibriums are studied in the isothermal-isobaric sections of the phase diagram of a fourcomponent iodine-potassium iodide-water-ethanol system at 25°C and atmospheric pressure. The compositions of the solvent at which it exhibits the greatest ability to dissolve iodine are established. It is shown that in all the investigated sections, there is three-phase eutonic equilibrium with potassium iodide and crystalline iodine as the solid phases. It is revealed that in the sections containing 30 and 50% of ethanol, potassium iodide serves as the salting in agent for crystalline iodine, due to the formation of polyiodide complexes of various composition in the studied system.     

Phase diagram of the eutectic benzoic acid-naphthalene system in the temperature range of 300–400 K

Liquid-solid phase equilibria are studied in the eutectic benzoic acid-naphthalene system by means of thermic analysis (DTA, CTA), on the basis of which the liquidus line and eutectic point (x _e ≈ 50 mol %, T _e ± 340 K) are determined and the phase diagram is constructed. Average precrystallization supercooling temperatures ΔT _L ^? of the liquid phase relative to liquidus temperature T _L are determined, allowing us to locate the region of solution metastability on the phase diagram. Excessive functions of the components in the liquid phase are found via thermodynamic modeling using the Margules equation and experimental data. The boundaries of the region of liquid solution metastability are estimated from the thermodynamic conditions of solution stability.     

Phase diagram studies of methanol–CHF3 and methanol–H2O–CHF3 mixtures

Comprehensive phase diagrams of methanol/CHF₃ and methanol/H₂O/CHF₃ mixtures over the temperature range of 25–100°C and pressure range of atmospheric to 340 atm are reported. Fluoroform is expected to be useful as an alternative to CO₂ for enhancing the fluidity of liquid mixtures due to its high polarity and low viscosity. Therefore, these mixtures will be studied as mobile phases for enhanced-fluidity liquid chromatography and extraction. The phase behavior of methanol/CHF₃ and methanol/H₂O/CHF₃ was compared to that of methanol/CO₂ and methanol/H₂O/CHF₃. Fluoroform is markedly more miscible with methanol or methanol/H₂O than is CO₂. Data for methanol/CHF₃ binary mixtures were also modeled by the Peng–Robinson equation of state. The correlation results showed that the PR equation of state with two temperature-independent binary parameters was capable of representing the experimental data over the entire temperature range with an average relative deviation within 6%.     

A study on the phase diagram of AlF3CsF system

Phase relations of the AlF₃CsF system have been investigated by the methods of DTA and XRD with quenching technique. Four compounds were identified: Cs₃AlF₆, CsAlF₄, CsF·2AlF₃ and CsF·3AlF₃. Cs₃AlF₆ melts congruently at 790°C. The first eutectic, E₁, between Cs₃AlF₆ and CsF is located in 10.0 mol% AlF₃ at 654°C. CsF·2AlF₃ and CsF·3AlF₃ melt incongruently at 508° and 653°C, respectively. The second eutectic, E₂, was observed in 42.0 mol% AlF₃ at 471°C. The compound CsAlF₄ formed in the solid eutectic when cooled below 443°C. CsAlF₄ has α and β forms, transformation of which takes place reversibly at 422°C. All phase structures in the system were confirmed by X-ray powder diffraction analysis.     

Phase diagrams of a condensed decane–eicosane–cyclododecane system

An n-eicosane–cyclododecane–n-decane system related to eutectic-type systems is investigated by means of differential thermal analysis. The eutectic alloy with melting point of–33.8°C contains 2.8 wt % of n-eicosane, 89.2 wt % of n-decane, and 8.0 wt % of cyclododecane.     

Comparative thermodynamic study of Ga–In–Sb system

The results of comparative thermodynamic analysis of Ga–In–Sb system are presented in this paper. Investigations, carried out in the section from Ga corner with molar ratio of In:Sb equal to 1:1, were done experimentally, using Oelsen calorimetry at the temperature 873 K and analytically, applying different calculation methods—Toop and Muggianu, in the temperature interval from 873 to 1673 K. Excess molar Gibbs energies and activity of all components in specified temperature interval were calculated.     

Phase diagram and electrical conductivity of the DyBr<Subscript>3</Subscript>–RbBr binary system

Phase equilibrium in the DyBr₃–RbBr binary system was established from differential scanning calorimetry measurements. This system exhibits three compounds, namely Rb₃DyBr₆, Rb₂DyBr₅, and RbDy₂Br₇, and two eutectics located at DyBr₃ molar fraction x = 0.116 (T = 886 K) and x = 0.458 (T = 702 K), respectively. Rb₃DyBr₆ undergoes a solid–solid phase transition at 726 K and melts congruently at 1,059 K. Rb₂DyBr₅ and RbDy₂Br₇ melt incongruently at 737 and 748 K, respectively. The electrical conductivity of DyBr₃–RbBr liquid mixtures was measured over the whole composition range. Results obtained are discussed in term of possible complex formation.