Premelting and the formation of solid solutions

Possibilities for the occurrence of marked premelting are reviewed for various types of crystal lattice. Examination of criteria for the detection of homophase premelting involves careful consideration of the effects of forming solid solutions, when impurities are present. Some of the consequences of forming solid solutions are discussed in relation to premelting phenomena.     

The formation of solid solutions in the tetrahydrofuran-tetra(n-propyl)ammonium fluoride-water system

The phase diagram of the tetrahydrofuran (THF)-tetra(n-propyl)ammonium fluoride (Prp₄ NF)-water system has been studied by differential thermal analysis (DTA). Solid solutions have been detected of the general formula THF·x Prp₄NF·(17–2x) H₂O, wherex changes from 0.06 to 0.5. The formation of solid solutions is due to the variable degree of the filling of the fragment consisting of four D-cavities in CS-II clathrate hydrates by the tetra(n-propyl)ammonium cation. The solid solution obtained is peculiar in that its vacancies are occupied by the blocks of four D-cavities each. Besides, this kind of displacement of two water molecules by an ionic pair Prp₄N⁺+F^–, where only the charges of the substituting and substituted groups are equal, takes place here. It appears that this type of solid solution has been discovered for the first time.     

Phase formation of BICUVOX solid solutions

Phase formation of Bi₄(V_{1 ? x} Cu _x )₂O_{11 ? z} solid solutions (BICUVOX) with x = 0.00–0.20 and Δx = 0.02 was studied. The concentration stability ranges were determined for the α, β, and γ polymorphs of BICUVOX solid solutions at room temperature, and their unit cell parameters were revised. The following was found to occur as x rises: the α ai β phase transition temperature between the monoclinic and orthorhombic phases shifts down, the β ai γ phase transition temperature to the high-temperature tetragonal phase shifts down, and the order-disorder phase transition temperature between γ′ ai γ tetragonal phases shifts up.     

Solid solutions in the Zn-Co-O system: Physicochemical properties

Physicochemical analysis is used to study phase equilibria and to design a concentration diagram for the Zn-Co-O system. ZnO-, CoO-, and Co₃O₄-based mixed crystals with a fixed Zn/Co ratio have different oxygen nonstoichiometry depending on the synthesis and annealing parameters. Metastable clustering is discovered in Zn_{1 ? x} Co_xO_{1 + δ} wurtzite solid solutions, which exist stably in the range 0 ≤ x ≤ 0.2. Magnetization investigation shows that an antiferromagnetic order exists in homogeneous Zn_{1 ? x} Co_xO_{1 + δ} grains; this order is conserved up to 625 ± 25 K. The substitution of praseodymium, neodymium, samarium, or europium for zinc(II) cations in Zn_0.9Co_0.1O_{1 + δ} does not spoil the compensated antiferromagnetism of the wurtzite unit cell.     

Properties of solid solutions in the KCl-NaCl system

Conditions for the decomposition of solid solutions in the KCl-NaCl system and their electrophoretic properties were studied. Compositions based on the KCl-NaCl system can be used for producing temperature sensors.     

Physicochemical modeling and experimental study of the interaction in the Si-Al-Ca-Mg-Fe-Na-K-V-Cl-H-O system

Physicochemical modeling is used to study the interaction in the SiO₂-Al₂O₃-CaO-MgO-Fe₃O₄-Na₂O-V₂O₃(V₂O₅)-HCl-H₂O system. The regions of formation of calcium (magnesium, iron) vanadates and various vanadium oxides are determined. The conditions for the most complete extraction of vanadium into hydrochloric acid solutions are estimated. The data obtained can be used to develop the procedure a the extraction of vanadium during the leaching of basalt with hydrochloric acid. Original Russian Text ? N.V. Kochetkova, N.P. Dergacheva, S.V. Fomichev, V.A. Krenev, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 7, pp. 1205–1211.     

Physicochemical interaction in the TlSe-Tl2SnSe3-Se quasi-ternary system

The physicochemical interaction in the TlSe-Tl₂SnSe₃-Se quasi-ternary system was studied by differential thermal analysis, X-ray powder diffraction, and mathematical modeling. A projection of the liquidus surface and the three-dimensional phase diagram of the TlSe-Tl₂SnSe₃-Se quasi-ternary system were constructed. It was determined that this system is of the eutectic type and limited solid solutions based on the initial components form in it. New intermediate compounds were not observed in the quasi-ternary system.     

Physicochemical processes at the boundary between some semiconducting solid solutions and contact alloys

Some adhesion and electric properties of boundaries between Bi₂Te₃-Sb₂Te₃-Gd₂Te₃ solid solution crystals and Bi-Pb-Sn and Bi-Sn alloys and the formation of various intermediate phases in these systems were studied. When the alloys are applied to crystal end faces, crystals are dissolved in contact material melt and contact material components diffuse into crystals. This is accompanied by the formation of intermediate phases such as PbTe and SbTe at the boundary. The 57 wt % Bi + 43 wt % Sn alloy was found to form contacts with the systems studied with fairly low contact resistances and wetting angles and high work of adhesion and adhesion strength.     

Physicochemical properties of Cr/TiO2 solid solutions

Solid solutions of Cr³⁺ ions in TiO₂ have been prepared by impregnating commercial TiO₂ with CrO₃(aq) and annealing in O₂ at 770 K. X-Ray diffraction data show the absence of a segregated Cr₂O₃ phase. The magnetic and spectroscopic properties have also been investigated.

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Cr³⁺ TiO₂ TiO₂ CrO₃(.) O₂ 770 . Cr₂O₃. .

     

Thermal interaction in two-layered solid fuel system

Journal of Mathematical Chemistry - The stability and dynamics of combustion waves in a system consisting of two exothermic solid fuel layers in thermal contact is numerically investigated within...     

Peculiarities of formation of ZnO and CuO-based solid solutions

Low-temperature (623 K) treatment of hydroxocarbonate compounds of copper-zinc and copper-zinc-aluminium leads to the formation of phases with CuO and ZnO structures, which are solid solutions of the promoter ions. The formation of solid solutions is attributed to structural distortions (uniform or local) in the oxide lattice due to the incomplete removal of OH^– and CO ₃ ^2– groups at low temperatures.

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, (623 ) - -- CuO ZnO, . , ( ) - OH ₃ ^–– - .

     

Paracetamol-propyphenazone interaction and formulation difficulties associated with eutectic formation in combination solid dosage forms

Polymorphic behaviours of paracetamol and propyphenazone and interaction between these two compounds were investigated using differential scanning calorimetry (DSC), X-ray powder diffraction and Fourier transform-infrared (FT-IR)-spectroscopy. Binary mixtures containing various ratios of the compounds were prepared as physical and fused mixtures and analysed by DSC to study their thermal behaviours. Phase diagrams obtained from the melting endotherms of the binary mixtures demonstrated formation of an eutectic mixture at a paracetamol-propyphenazone combination of about 35:65 (w/w) with an eutectic temperature of 56 degrees C. The FT-IR spectroscopy revealed no chemical interaction due to eutectic formation, and a lower degree of crystallinity of the eutectic mixture than individual substances was observed by X-ray powder diffraction analysis. The DSC and X-ray powder diffraction data demonstrated a polymorphic change in propyphenazone as a result of melting of the compound. Tablets, containing both paracetamol and propyphenazone in a combination formulation and prepared using standard wet granulation technology, were found to have physical instability when packed in either polyvinylchloride// aluminium or polyvinylchloride/polyvinyldienechloride// aluminium blisters and stored for one month at 40 degrees C with either 75% relative humidity or without any humidity control. The instability of the tablets was more apparent under the high humidity condition.     

Structural transformations in mechanochemical synthesis of solid solutions in the Cu-Ga system

Formation of solid solutions in the copper-gallium system under mechanical activation is considered as an example of a mechanochemical interaction between a solid metal and a liquid metal.     

Adrenaline system: another rare case of conglomerate with partial solid solutions

Journal of Thermal Analysis and Calorimetry - Adrenaline, in its enantiomeric form l-, is the drug of choice for the treatment of cardiac arrest or certain serious shock conditions. However,...     

Preparation and identification of substitutional solid solutions of the InSb-CdTe system

Substitutional solid solutions with a sphalerite cubic structure have been synthesized on the basis of binary semiconductor compounds InSb and CdTe in their miscibility regions. The solid solutions have been identified using X-ray diffraction, thermal analysis, IR spectra, and electrophysical measurements.     

ESR study of the interaction of oxygen and propene with solid CoO?MgO solutions under pulse conditions

An ESR study has shown that under the action of oxygen pulses, radical ions O ₂ ^– with g_I=2.0085 and g_II=2.087 are generated at room temperature on the surface of 1% CoO–MgO. Heating of the sample to 150 °C in the spectrometer results in complete disappearance of the O ₂ ^– signal from the ESR spectra. The variation of the O ₂ ^– signal intensity with time due to the interaction between propene and oxygen adsorbed on the sample surface, has been measured.

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, 1% CoO–MgO - O ₂ ^– g_I=2.0085 g_II=2.087. 150 °C - O ₂ ^– . O ₂ ^– .

     

Physicochemical aspects of the liposome-wool interaction in wool dyeing

Despite the promising application of liposomes in wool dyeing, little is known about the mechanism of liposome interactions with the wool fiber and dyestuffs. The kinetics of wool dyeing by two dyes, Acid Green 27 (hydrophobic) and Acid Green 25 (hydrophilic), were compared in three experimental protocols: (1) without liposomes, (2) in the presence of phosphatidylcholine (PC) liposomes, and (3) with wool previously treated with PC liposomes. Physicochemical interactions of liposomes with wool fibers were studied under experimental dyeing conditions with particular interest in the liposome affinity to the fiber surface and changes in the lipid composition of the wool fibers. The results obtained indicate that the presence of liposomes favors the retention of these two dyes in the dyeing bath, this effect being more pronounced in case of the hydrophobic dye. Furthermore, the liposome treatment is accompanied by substantial absorption of PC by wool fibers with simultaneous partial solubilization of their polar lipids (more evident at higher temperatures). This may result in structural modification of the cell membrane complex of wool fibers, which could account for a high level of the dye exhaustion observed at the end of the liposome dyeing process.     

Thermodynamic stability of calcium vanadium garnet ferrites upon formation of substitutional solid solutions

The thermodynamic stability of calcium vanadium garnet ferrites Ca₃Fe_{3.5 ? x} Ti_2x V_{1.5 ? x} O₁₂ upon isomorphic substitution of titanium ions for iron and vanadium ions was studied by the EMF method using ZrO₂(Y₂O₃) ceramic solid electrolyte. Temperature-dependent ΔG ⁰ was determined. Isomorphic substitutions of titanium ions for iron and vanadium ions in the inequivalent sublattices of the garnet structure in a temperature range of 1100–1483 K cause changes in ΔG ⁰ due to the entropy and enthalpy components and has a minimal value when x = 0.15.