Monotectic Type Research Articles

PHASE RELATIONS IN THE Cu3SbS4-Sb2S3-S SYSTEM

Phase relations in the Cu3SbS4-Sb2S3-S system were determined experimentally over the entire concentration range by means of differential thermal analysis (DTA) and powder X-ray diffraction (PXRD) techniques. One boundary, two internal polythermal sections, and the liquidus surface projection of the system were constructed. Primary crystallization fields of existing phases, as well as, types and coordinates of non- and monovariant equilibria were determined. It was defined that, the concentration triangle under study is an independent subsystem of the Cu-Sb-S ternary system and belongs to the monotectic type with a wide stratification field of two liquids.

Phase diagram of the iodine-sodium iodide-water-propyl alcohol system at 298.15 K

Phase equilibria in the cross sections of isothermal-isobaric sections of the phase diagram of four-component iodine-potassium iodide-water-propyl alcohol are investigated at 298.15 K and pressure of 101325 Pa. It is shown that a three-phase equilibrium of the eutonic type occurs in the cross sections containing (I) 10 and (II) 30 wt % of propyl alcohol, and two three-phase equilibria of the monotectic type are found in cross section II. It is shown that the solid phases of saturated solutions in the investigated cross sections are potassium iodide and crystalline iodine. The compositions of the mixed solvents with the strongest iodine dissolving ability relative to individual solvents are established.

Liquid phase separation of ternary Al–In–Sn/Ge monotectic type alloys investigated with calorimetric method

The phase equilibrium, thermodynamic properties and liquid demixing patterns for binary Al100−xInx, ternary (Al100−xInx)90Sn10 and (Al100−xInx)90Ge10 (x=wt.%) alloys are investigated by differential scanning calorimetry (DSC) method. The corresponding phase diagrams are experimentally established, and it is found that both monotectic temperature and critical temperature for immiscibility gap decrease when either Sn or Ge is added to binary Al100−xInx alloys. The enthalpy of fusion for binary Al–In alloys, ternary Al–In–Sn and Al–In–Ge alloys shows linear functions with In content, and the introduction of Sn and Ge elements decreases the enthalpy of fusion. The liquid phase separation mechanism is discussed in relation to the DSC curves and solidified microstructures. It is demonstrated that the core and shell phases can be altered by the addition of Ge element in (Al100−xInx)90Ge10 alloys as compared with those in binary Al100−xInx and ternary (Al100−xInx)90Sn10 alloys. This provides an effective way to switch the inner and outer phases for core–shell structure.

Solution based synthesis of mixed-phase materials in the Li2TiO3–Li4SiO4 system

As candidate tritium breeder materials for use in the ITER helium cooled pebble bed, ceramic multiphasic compounds lying in the region of the quasi-binary lithium metatitanate–lithium orthosilicate system may exhibit mechanical and physical advantages relative to single phase materials. Here we present an organometallic solution-based synthesis procedure for the low-temperature fabrication of compounds in the Li2TiO3–Li4SiO4 region and investigate phase stability and transformations through temperature varied X-ray diffraction and scanning calorimetry. Results demonstrate that the metatitanate and metasilicate phases Li2TiO3 and Li2SiO3 readily crystallise in nanocrystalline form at temperatures below 180°C. Lithium deficiency in the region of 5% results from Li sublimation from Li4SiO4 and/or from excess Li incorporation in the metatitanate phase and brings about a stoichiometry shift, with product compounds exhibiting mixed lithium orthosilicate/metasilicate content towards the Si rich region and predominantly Li2TiO3 content towards the Ti rich region. Above 1150°C the transformation of monoclinic to cubic γ-Li2TiO3 disordered solid-solution occurs while the melting of silicate phases indicates a likely monotectic type system with a solidus line in the region 1050–1100°C. Synthesis procedures involving a lithium chloride precursor are not likely to be a viable option for breeder pebble synthesis as this route was found to yield materials with a more significant Li-deficiency exhibiting the crystallisation of the Li2TiSiO5 phase at intermediate compositions.

Experimental and thermodynamic assessment of the Gd–Ti system

The phase equilibria of the binary Gd–Ti system were studied by combining electrostatic levitation of the melt with high energy synchrotron in situ X-ray diffraction at elevated temperatures. The coexistence of the phases including the liquid was directly proven in the temperature range between T=1000 and 1920K. The Gd–Ti system is of monotectic type characterized by a miscibility gap in the liquid state above the monotectic temperature T=1841±5K. Together with experimental data from thermo-analysis and microstructure investigation of as-cast samples an improved Gd–Ti phase diagram is presented and a thermodynamic description is derived.

Dy-Ti (Dysprosium-Titanium)

The Dy-Ti phase diagram shown in [Massalski2] was a monotectic type with the monotectic temperature at 1400 C. The miscibility gap in the liquid phase was speculated to be limited to a narrow range because a miscibility gap was observed in the Gd-Ti system and not in the Er-Ti system (atomic numbers of Gd, Dy, and Er are 64, 66, and 68, respectively). A eutectic reaction was shown at 1280 C. [2004Bul] doubted the monotectic type of this system because the Tb-Ti system is not a monotectic type (atomic number of Tb is 65). Figure 1 shows the Dy-Ti phase diagram proposed by [2004Bul], which was determined based on DTA data measured at 18 and 95 at.% Ti. The eutectic type was concluded because of the characteristic microstructure of the 18 at.% Ti alloy. According to the criteria given by [1991Oka], however, the opening angle of the L + (bTi) two-phase field at 100 at.% Ti in Fig. 1 is too broad. The initial slope of the liquidus is probably much steeper (the opening angle may be about a half). Then, it could be assumed that the phase diagram includes a monotectic reaction, as shown in [Massalski2]. This assumption does not contradict the result of [2004Bul] because a eutectic reaction also exists in the phase diagram. If the monotectic reaction does not exist, as concluded by [2004Bul], there would be a nearly horizontal section in the liquidus curve in the center region of the phase diagram. Further experimental data are needed to reach the conclusion.

T-x-y Computer Models with SiC and SiO2

Method to design the computer models of T-x-y diagrams with SiC and SiO2 by means of kinematical surfaces has been considered. Templates for computer models of three Т-х-у diagrams are analyzed: 1) with the liquidus field of low-temperature polymorphous modification; 2) with the invariant 4-phase transformation of monotectic type; 3) with the liquidus surfaces of two modifications of component B and an invariant monotectic reaction of two immiscible liquids with solid phases C and A.

Phase behavior and optical- and mechanical properties of the binary system isotactic polypropylene and the nucleating/clarifying agent 1,2,3-trideoxy-4,6:5,7-bis- O-[(4-propylphenyl) methylene]-nonitol

The phase behavior and optical- and selected mechanical properties of the binary system consisting of isotactic polypropylene (i-PP) and a new sorbitol-based nucleating and clarifying agent, 1,2,3-trideoxy-4,6:5,7-bis- O-[(4-propylphenyl) methylene]-nonitol (TBPMN), were investigated. Temperature/composition diagrams of the binary were found to be of the simple monotectic type, similar to those of, among others, the previously investigated i-PP/1,3:2,4-bis(3,4-dimethyldibenzylidene)sorbitol (DMDBS). Liquid–liquid phase separation was observed in binaries comprising more than ∼5% w/w TBPMN, indicative of enhanced miscibility of the new additive with i-PP when compared with that of DMDBS. At TBPMN contents ≥0.1% w/w the optical properties haze and clarity progressively improved to remarkable levels with increasing concentration of the nucleating agent up to the onset of liquid–liquid phase separation, above which they deteriorated. The enhanced solubility in i-PP of the new clarifying agent on the one hand required uneconomically higher concentrations than previous members of the sorbitol family to be effective, but on the other, the superior optical properties of the system may permit manufacturing of clarified products of increased thickness.

The Hg—P (Mercury—Phosphorus) System

AbstractFor Abstract see ChemInform Abstract in Full Text.

The Hg-P (Mercury-Phosphorus) System

The Hg-P system was not studied systematically, and its whole phase diagram is unknown. Hg and P (white) melt at –38.8290 and 44.14 °C, respectively, and boil at 356.623 and 277 °C, respectively, when the pressure is 0.101325 MPa. P exists in many allotropic modifications [1989Gre]. At least five crystalline and several amorphous or vitreous forms of P are known, but when they melt, they all give the same liquid, consisting of P4 molecules of tetrahedral structure. This form is also present in the gas phase at temperatures lower than 800 °C. The allotropic forms of P have different colors and other physical properties as well as different chemical reactivities. The most stable allotropes are cubic P (white) and orthorhombic phosphorus (black). It is of interest that P heated at 380 °C in the presence of Hg gives vitreous gray P [1989Gre]. [1911Vou] claimed the formation of a Hg-P compound by heating both components under a layer of paraffin, but no analysis was made to determine the resultant product. Hg 3 P 4 ,H g 3 P 2 , and Hg 3 P compounds were obtained by indirect chemical reactions [1947Mel], but formation by direct alloying was not observed by [1951Rot]. Therefore, these compounds should be treated as metastable phases. The melting temperatures of P and Hg would suggest considerable miscibility of the elements near ambient temperature. According to [1910Ger], molten P dissolves some amount of Hg, and the resulting colorless solution is blackened after solidification due to the rejection of Hg excess. [1951Rot] measured Hg solubility in metastable liquid P at 25 °C by using a chemical analysis of the equilibrated phases. The solubility value found amounts to 0.0176 at.% Hg, which amounts to one-fifteenth of the value predicted from the regular solution model. These authors observed that the solubility of Hg in liquid P increased slightly with temperatures up to 100 °C, but no numerical results were reported therein. Because P is soluble in such metals as Pb and Bi [1947Mel], one may predict that detectable amounts of P should also dissolve in Hg. These facts suggest that the Hg-P diagram should be of a monotectic type, with a critical temperature higher than the boiling point of Hg (at normal pressure). Crystal structures of the elements and their lattice parameter data are listed in Table 1. By analogy with an ammonium amalgam [1997Gum], a “phosphonium amalgam” was formed [1889Bes] during the electroreduction of PH4 + on a Hg electrode at –25 to –40 °C, The PH 4 · radical possesses metallike properties that qualitatively approximate those of the alkali metals. The phosphonium amalgam, like the ammonium amalgam, should be stable in the solid state at temperatures lower than the Hg melting point.

Solid–liquid phase behavior of binary fatty acid mixtures: 1. Oleic acid/stearic acid and oleic acid/behenic acid mixtures

Solid–liquid phase behavior of binary fatty acid mixtures was investigated by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) for the mixture composed of oleic acid (OA) and stearic acid (SA) and that composed of OA and behenic acid (BA). The DSC results provided a monotectic type T– X phase diagram for these mixtures, from which it was suggested that the two fatty acid species are completely immiscible in a solid phase regardless of the two polymorphs of OA, i.e., α-form or γ-form. The solid phase immiscibility was confirmed by the FT-IR observation that the spectra obtained for the mixtures correspond to the superposition of the two spectra for respective components. Thermodynamic analysis of liquidus line demonstrated that OA and SA form an ideal mixture in a liquid phase, whereas the mixing of OA and BA in a liquid phase is slightly non-ideal.

Structure of stratum corneum lipids characterized by FT-Raman spectroscopy and DSC. IV. Mixtures of ceramides and oleic acid

The thermotropic and lyotropic phase behaviour of mixtures of ceramides type IV (CER) and oleic acid (OA) was investigated using Fourier transform (FT) Raman spectroscopy and differential scanning calorimetry (DSC). The Raman spectra of the mixtures in the solid state exhibit sharp bands associated with trans sequences of the alkyl chain residues of both lipids, indicating highly ordered chains. The DSC heating curves for the dry and the fully hydrated mixtures show three endothermal transitions. The events at T=−5.5 and 12.3°C do not depend on the composition of the mixtures. As in the case of pure OA, they are associated with the solid–solid transition of OA from γ to α modification and the melting of the α phase, respectively. The temperature of the third event at higher temperatures decreases continuously with increasing OA content. This transition involves the melting of CER. Both DSC and Raman spectroscopic studies reveal that CER and OA are immiscible in the solid state. The phase diagram is a monotectic type one. Calculations of the melting curve of CER support this interpretation. Full hydration of the system causes a decrease of the temperature of the upper transition, but, the general feature of the phase diagram remains.

INTERACTION OF TEMAZEPAM WITH CERTAIN MACROMOLECULES: IV- PHASE DIAGRAM OF TEMAZEPAM-POLYETHYLENE GLYCOL BINARY SYSTEMS

Differential scanning calorimetery and hot stage microscopy were used to build up temperature-composition phase diagrams for temazepam-polyethylene glycol 2000, 4000 and 6000 physical mixtures and comprecipitates. The phase diagram showed the systems to be of the monotectic type, with the monotectic species being the pure drug. Phase diagram of the drug and the investigated polyethylene glycols helped in ruling out the possibility of forming solid solution or molecular compound within the concentration range of the components investigated. Differential scanning calorimetery was also utilized for predicting the melting behaviour of temazepam and polyethylene glycols separately and as coprecipitates and physical mixture binary systems. A good correlation was found between the position of the system on the phase diagram and its dissolution rate. The highest the carrier content, the nearest the system would be to the monotectic composition, the highest the release rate of the drug.

Some thermodynamic aspects of organic eutectic in a monotectic type system

Phase diagram and heat of fusion of succinonitrile–phenanthrene system have been studied. Heat of mixing, entropy of fusion, and excess thermodynamic functions such as hE, sE, and gE have also been calculated. The results have been explained on the basis of cluster formation and the interactions among the components forming the eutectic melt. Solid–liquid and liquid–liquid interfacial energies calculated from the heats of fusion of the pure components suggest the validity of Cahn wetting condition and predict the monotectic solidification morphology in the present system.

The main types of phase diagrams for the rare-earth-X systems and their correlation with the periodic table

As the result of reviewing the phase diagrams for binary rare earth (RE)-X (element) systems, complete or partial, published to date, the author has successfully classified 530 binary systems, with reference to their phase diagrams, into four different types. The types of phase diagrams for binary RE-X systems are closely related to the position that the component X occupies in the periodic system. Four different types of RE-X systems are defined as follows. 1. 1. The compound-forming system. The main part of the compound-forming system is based on the combination of p-f- and d 5–10-f-elements. In this case, the components X are those elements lying on the right of group VIIB of the periodic table with the exception of hydrogen and beryllium, magnesium which belong to groups IA and IIA. 2. 2. The solubility type. At least one range of complete solid solubility exists in this type of phase diagram. In this case, the RE-X systems consist of a combination of either the f-f-element or (europium or ytterbium)-(calcium or barium). The valence electron number of the two components constituting the system are equal. 3. 3. The monotectic type, and 4. the eutectic type. These two types of phase diagram are based on the combinations of d 1–4-f- and s 1–2-f-elements. However, in the case of the monotectic type, there are generally very large differences between the melting temperatures of the two components.

Observations of a monotectic solidification interface morphology

For detailed studies of the region around a solidification interface on a microscopic scale, a very thin (essentially two-dimensional) test cell may be translated across two temperature-controlled heating/cooling blocks and viewed with a microscope. Such a device is sometimes referred to as a temperature gradient microscope stage (TGS). Of particular interest in this study is the behavior of a monotectic type solution during solidification. Succinonitrile based model systems for metallic monotectic alloys, when solidified on a TGS, form an unusual “worm-like” micromorphology. These interfaces are observable in situ under high optical magnification during growth.

Comparison of polyethylene glycol and polyoxyethylene stearate as excipients for solid dispersion systems of griseofulvin and tolbutamide I: Phase equilibria

Phase equilibrium diagrams were constructed based on hot-stage microscopy and differential scanning calorimetry of solid dispersions of griseofulvin or tolbutamide in polyethylene glycol 2000 or polyoxyethylene 40 stearate. The solid dispersions were prepared by physical mixing, fusion, and coprecipitation from ethanol. The phase diagrams were largely independent of the method of preparation of the dispersion systems. The diagrams were of the monotectic type for polyethylene glycol 2000 with each drug and for griseofulvin with each excipient, with the monotectic species being the pure drug. Polyoxyethylene 40 stearate with tolbutamide gave eutectic systems in which liquid polyoxyethylene 40 stearate dissolved up to 20% of the tolbutamide. The phase diagrams showed greater solubility of tolbutamide in liquid polyoxyethylene 40 stearate than in polyethylene glycol 2000 but showed a similar solubility of griseofulvin in each excipient. Solid solution formation was not detected.

Application of phase diagrams to predict phases formed during deoxidation of steel

Phase diagrams for simple ternary systems such as Fe-Al-O, Fe-Si-O and more complex systems Fe-Mn-Al-O, Fe-Mn-Si-O have been used to rationalize some of the observations made during deoxidation. The formation of less stable oxides such as liquid aluminates and spinel is shown to be a consequence of the reaction path followed by the metal-inclusion system. The significance of univariant conditions in which three phases are in equilibrium is brought out. During cooling and solidification inclusions may change from a solid oxide to a liquid oxide phase and vice versa. This causes a change in solidification from eutectic type to a monotectic type. The existence of a saddle point at which either a eutectic or monotectic solidification begins is established and its significance in semi-killed steel is brought out.

Evidence for Liquid Immiscibility in the System FeS-S

The results of heating experiments performed in evacuated, sealed, silica-glass tubes indicate that in the FeS--S system two immiscible liquids can co-exist in invariant equilibrium with crystalline pyrrhotite and vapor at 1,092 + or - 3 degrees C. The compositions of the condensed phases at 1,092 + or - 3 degrees C are (weight % Fe): crystalline pyrrhotite --59.2 + or - 0.3; liquid A -- 49.0 + or - 1.1; liquid B [asymp] 0.5. The phase relations at the invariant temperature are of the monotectic type. An equilibrium diagram for the FeS--S system above 700 degrees C is presented.Charges in silica tubes were heated in a pressure vessel at approximately 200 atm pressure of argon or water to prevent the high sulfur pressures of the charges from blowing up the tubes. Narrow brackets on the invariant temperature were obtained with charges covering a range of compositions and specific volumes.