A. V. Khoroshilov

Low-temperature heat capacity and thermal behavior of Zn0.98Co0.02O in the high-temperature region

The low-temperature heat capacity of Zn 0.98Co0.02O oxide was measured by adiabatic calorimetry. The formation of a solid solution was shown to be accompanied by a change in the entropy by 0.4 J/(K mol). No anomalies in the heat capacity or the thermal behavior confirming the phase transformations found earlier by other methods were observed. A heat capacity anomaly was revealed below 15 K and tentatively attributed to a change in the magnetic properties of the substance.

Synthesis and crystal structure of new complex sodium lanthanide phosphate molybdates Na2MIII(MoO4)(PO4)(MIII = Tb, Dy, Ho, Er, Tm, Lu)

New complex sodium lanthanide phosphate molybdates Na2MIII(MoO4)(PO4)(MIII=Tb, Dy, Ho, Er, Tm, Lu) have been synthesized by the ceramic method (T = 600°C, τ = 48 h), and their unit cell parameters have been determined. The structures of Na2MIII(MoO4)(PO4)(MIII = Dy, Ho, Er, Lu) were refined by the Rietveld method. The compounds are isostructural: they are orthorhombic (space group Ibca, Z = 8) and have layered structures. In the structures of phosphate molybdates, chains of MIIIO8 polyhedra and MoO4 tetrahedra are linked by PO4 tetrahedra to form layers. The MoO42− anions are involved in dipole-dipole interaction. The sodium ions are arranged in the interlayer space. The compounds melt incongruently at 850–870°C.

Crystallization and glass transition of the diols and aminoalcohols, according to DSC data

Overcooling, crystallization, and glass transition of the diol series and aminoalcohols which are the liquids with spatial hydrogen-bond networks, which are the along with the overcooling of dioxane, dimethylsulfoxide, and acetonitrile, which do not have such networks were studied by DSC. The observed phenomena are explained by the stability of H-bond networks. It was concluded that changes in the stability of the networks in and between series of diols and aminoalcohols are due to differences between their molecular structures, the energies of their hydrogen bonds, and their network topologies.

Effect of iron content on the sintering of ground basalt into ceramics

Ground basalt from the Myandukha occurrence, Arkhangelsk oblast, was divided into magnetically enriched and magnetically deficient components by magnetic separation, and their chemical compositions were determined. We investigated the difference in thermal behavior between the two components using differential scanning calorimetry and thermogravimetry data and the mineralogical composition obtained by thermodynamic modeling of the basalt. The sintering behavior of the magnetic and nonmagnetic components of the ground basalt was examined, and some properties of the resultant ceramic materials were studied.

Phase composition of metamorphosed basalt and its sintering products

The phase composition of metamorphosed basalt from the Myandukha occurrence, Arkhangelsk oblast, has been determined by X-ray diffraction. Using differential scanning calorimetry and thermogravimetry data, we examined the effect of phase composition and particle size on the thermal behavior of ground basalt. The phase composition of the sintering products of the magnetic and nonmagnetic components of the basalt has been investigated.

Heat capacity and thermodynamic functions of Mg(Fe0.8Ga0.2)2O4 at high temperatures

The heat capacity of Mg(Fe0.8Ga0.2)2O4 solid solution was measured by differential scanning calorimetry (DSC) at 353–1153 K. The thermodynamic functions (entropy and enthalpy changes) were calculated based on smoothed heat capacity values. No heat capacity anomalies were found in the temperature range under study.

A calorimetric study of the thermodynamic properties of potassium molybdate

The low-temperature heat capacity of K2MoO4 was measured by adiabatic calorimetry. The smoothed heat capacity values, entropies, reduced Gibbs energies, and enthalpies were calculated over the temperature range 0–330 K. The standard thermodynamic functions determined at 298.15 K were Cp° (298.15 K) = 143.1 ± 0.2 J/(mol K), S°(298.15 K) = 199.3 ± 0.4 J/(mol K), H°(298.15 K)-H°(0) = 28.41 ± 0.03 kJ/mol, and Φ°(298.15 K) = 104.0 ± 0.4 J/(mol K). The thermal behavior of potassium molybdate at elevated temperatures was studied by differential scanning calorimetry. The parameters of polymorphic transitions and fusion of potassium molybdate were determined.

DSC study of YaBabCucO72212;δ homogeneity in the region 1050–1300 K

Phase transitions of the compositions Y1±xBa2±yCu3±zO72212;δ (x,y=0–0.2;z=0–0.5; step 0.1) were studied by DSC in argon atmosphere in the temperature range 1050–1300 K. The formation of three polymorphous modifications of the 123 phase was observed. The solubilities of yttrium, barium and copper oxides in every modification were determined. TheT-x-y phase microdiagram for the 123 phase was mapped out.

Phase Diagram of the Ethylene Glycol–Dimethylsulfoxide System

The phase diagram of ethylene glycol (EG)–dimethylsulfoxide (DMSO) system is studied in the temperature range of +25 to −140°C via differential scanning calorimetry. It is established that the EG–DMSO system is characterized by strong overcooling of the liquid phase, a glass transition at −125°C, and the formation of a compound with the composition of DMSO · 2EG. This composition has a melting temperature of −60°C, which is close to those of neighboring eutectics (−75 and −70°C). A drop in the baseline was observed in the temperature range of 8 to −5°C at DMSO concentrations of 5–50 mol %, indicating the existence of a phase separation area in the investigated system. The obtained data is compared to the literature data on the H2O–DMSO phase diagram.

Heat capacity and thermodynamic properties of Mg(Fe0.6Ga0.4)2O4 in the 0–800 K temperature range

The heat capacity of Mg(Fe0.6Ga0.4)2O4 in the temperature range of 4.56–804.9 K is measured by adiabatic and differential scanning calorimetry. The temperature dependence of the heat capacity of Mg(Fe0.6Ga0.4)2O4 in the 0–800 K range is determined by generalizing the experimental data. The temperature dependences of thermodynamic functions (entropy, enthalpy change, and the reduced Gibbs free energy) are calculated. The abnormal contribution to the heat capacity Cpan(T) in the temperature range of 5–52 K is estimated.