For the first time, carbon dioxide hydrate was synthesized from a 1

For the first time, a standard formation enthalpy for the K5Gd(MoO4)(4) compound was measured by solution calorimetry. Stabilization energy and lattice enthalpy were calculated. It was shown that the compound is thermodynamically stable with respect to decomposition into simple oxides, which makes it promising for practical applications.

Предложено комбинированное уравнение состояния метана в реальных переменных давление p — температура T — плотность r, позволяющее произвести расчет теплоемкостей Cv, Cp, и скорости звука W в явном виде в однофазных состояниях, включая критическую область. Уравнение содержит регулярную часть в форме уравнения Бендера для p(r,T) с 19 коэффициентами, масштабную часть с шестью коэффициентами и кроссоверную функцию явного вида (два коэффициента). Коэффициенты определены по массиву p,r,T-данных СH4 до 30 МПа, данные по Cv, Cp и W не привлекались, кроме зависимости Cv(T) в идеально-газовом состоянии и значения Cv при 100 К на ветви жидкости пограничной кривой. В регулярной области расчетные величины Cv, Cp и W близки к экспериментальным и табличным значениям, в критической области расхождения с табличными величинами не более 5%. Cреднеквадратичная погрешность давления sр = 0.8%, погрешность в Cv не более 5%. Результаты расчетов сравнены с кроссоверными уравнениями состояния для СН4. Сделан вывод о преимуществе предлагаемой модели уравнения состояния для расчетов теплофизических свойств метана.

Erbium-substituted bismuth oxide with a composition of Bi1.6Er0.4O3 was synthesized by the solid-phase reaction method. The compound is shown to have a cubic structure, space group Fm3m. The standard enthalpy of formation of Bi1.6Er0.4O3 was determined from the measured enthalpies of dissolution of Bi2O3, ErCl3, and Bi1.6Er0.4O3 in a 2 M HCl solution: ΔfH0(Bi1.6Er0.4O3(s)) = −819.0 ± 6.4 kJ/mol. The lattice enthalpy for the compound was calculated using the Born–Haber cycle: ΔlatH0(Bi1.6Er0.4O3(s)) = −13 227 kJ/mol.

The Cs2MoO4 single crystal grown by the Czochralski method was characterized using X-ray diffraction analysis and its heat capacity was measured by differential scanning calorimetry in the temperature range of 319-900 K. It was found that the single crystal undergoes a phase transition at a temperature of 842 K, therefore it is promising for applications in the temperature range of 319-842 K.

Стандартная энтальпия образования димолибдата натрия определена методом калориметрии растворения на основании измеренных энтальпий растворения Na2CO3, MoO3, Na2Mo2O7 в 0.2 M растворе NaOH и литературных данных: ∆fH0(Na2Mo2O7, 298.15 K) = −2245.3 ± 6.3 кДж/моль. С использованием цикла Борна–Габера рассчитана энтальпия решетки: –54730 кДж/моль. Показано, что длина волны люминесцентного излучения уменьшается от 650 нм до 540 нм при переходе от молибдата натрия к вольфрамату натрия, при этом энтальпия решетки уменьшается от –54730 кДж/моль (Na2Mo2O7) до –49030 кДж/моль (Na2W2O7). Температурная зависимость теплоемкости димолибдата натрия определена в области температур 320–785 K. Показано, что в этом интервале отсутствуют фазовые переходы.

The standard enthalpy of formation of sodium dimolybdate was determined by dissolution calorimetry based on the measured enthalpies of dissolution of Na2CO3, MoO3, and Na2Mo2O7 in a 0.2 M NaOH solution and the literature data: ΔfH0(Na2Mo2O7, 298.15 K) = −2245.3 ± 6.3 kJ/mol. The lattice enthalpy was calculated using the Born–Haber cycle: –54 730 kJ/mol. The wavelength of luminescence radiation decreased from 650 to 540 nm on passing from sodium molybdate to sodium tungstate, and the lattice enthalpy decreased from –54 730 kJ/mol (Na2Mo2O7) to –49 030 kJ/mol (Na2W2O7). The temperature dependence of the heat capacity of sodium dimolybdate was determined in the temperature range 320–785 K. There are no phase transitions in this range.

Physicochemical methods were used to study the oxidized carbon materials obtained by oxidation of the Tekhnosorb mesoporous carbon by 2–30

A combined equation of state of methane in real variables (pressure p, temperature T, density ρ) is proposed that allows calculations of heat capacities C_v , Cp, and speed of sound W in explicit form in single-phase states, including the critical region. The equation contains a regular part in the form of Bender’s equation for p(ρ,T) with 19 coefficients, a scaling part with 6 coefficients, and a crossover function in explicit form (2 coefficients). The coefficients are determined from a CH4 p, ρ,T data array up to 30 MPa. Data on C_v , Cp, and W are not involved, except for the C_v (T) dependence in the ideal gas state and value C_v at 100 K on the liquid branch of the boundary curve. In the regular region, the calculated values of C_v , Cp, and W are close to the experimental and tabulated values. Discrepancies with the tabular values are no more than 5 C_v is no more than 5

Cs 2 MoO 4 and Li 1.9 Cs 0.1 MoO 4 crystals were grown from melt by the low-thermal-gradient Czochralski technique. The standard formation enthalpy of cesium molybdate Cs 2 MoO 4 was measured by solution calorimetry. The heat capacity of Li 1.9 Cs 0.1 MoO 4 was measured by differential scanning calorimetry (DSC) in the temperature range 320–710 K. The lattice enthalpy of Cs 2 MoO 4 was calculated using the Born-Haber cycle. Cesium molybdate was shown to be thermodynamically stable to decomposition into constituent simple oxides (Cs 2 O and MoO 3 ), which made it promising for application. Li 1.9 Cs 0.1 MoO 4 experienced no phase transitions in the temperature range 320–710 K.

Ceramic Bi 1.4 Dy 0.6 O 3 and Bi 3 Nb 0.2 Sm 0.8 O 6.2 samples were prepared by solid-phase synthesis. The compounds have cubic structures (space group Fm 3 m ). Their standard enthalpies of formation were determined by solution calorimetry, and their lattice enthalpies were calculated. The lattice enthalpies of Bi 3 Nb 0.2 R 0.8 O 6.2 compounds decrease in magnitude when erbium is replaced by samarium, due to the lanthanide radius increasing from erbium to samarium. The lattice enthalpy of Bi 1.4 Dy 0.6 O 3 has a greater magnitude than the lattice enthalpy of Bi 1.2 Gd 0.8 O 3 .

Bismuth cobalt dysprosium oxide of composition Bi12.5Dy1.5CoO22.325 has been prepared by solid-state reactions. The compound has a cubic structure (space group Fm 3̅ m) with the unit cell parameter a = 0.55279(5) nm. The solution enthalpy and standard enthalpy of formation of Bi12.5Dy1.5CoO22.325 have been measured by solution calorimetry: ΔsolH0 = −1017.0 ± 7.5 kJ/mol, and ΔfH0 = −5338.8 ± 19.9 kJ/mol. The lattice enthalpy has been calculated using the Born–Haber cycle: ΔlatH0 = −99020 kJ/mol. The lattice enthalpy increases in magnitude as the lanthanide radius decreases in the neodymium–dysprosium–holmium series.

The single crystal of Na2W2O7 has been grown by the low-temperature-gradient Czochralski technique. The thermo- dynamic properties (standard enthalpy of formation, lattice enthalpy and stabilization energy), the knowledge of which is necessary to improve the growth technology, have been measured using reaction calorimetry. It has been shown that in the Na2W2O7– Na2Mo2O7 series, the luminescence wavelength increases from 540 to 650 nm, respectively, along with a change in the lattice enthalpy from −49030 to −54730 kJ mol−1.

Cesium dimolybdate (Cs2Mo2O7) has been grown by a low-temperature-gradient Czochralski technique. Cs2Mo2O7 is one of the perspective materials to search rare events. Also cesium (Cs) is one of the most important fission products in assessing the consequence of severe accidents. The standard formation enthalpy for single crystal of Cs2Mo2O7 was determined by reaction calorimetry. For the first time, the lattice enthalpy and stabilization energy were calculated. It was found that Cs2Mo2O7 was thermodynamically stable at room temperature in respect to decomposition into simple oxides (Cs2O, MoO3).

For the first time, single crystal of CsLiMoO4 was grown by low-temperature-gradient Czochralski technique with weight control. The low-temperature-gradient Czochralski technique is technique that allows one to grow the most perfect crystals. It was shown that structure of CsLiMoO4 single crystal was cubic. Thermodynamic properties of CsLiMoO4 single crystal, which were necessary for optimizing the conditions of crystal growth, developing recommendations for its application in optoelectronics, microelectronics, electro-optics, in investigations of rare events and other areas, were studied by calorimetry methods. For the first time, the standard formation enthalpy was obtained by reaction calorimetry; lattice enthalpy and stabilization energy of CsLiMoO4 single crystal was calculated. It was shown that single crystal was thermodynamically stable with respect to decomposition into simple oxides at room temperature. Based on obtained and published data, it was shown that with decreasing of lattice enthalpies, the luminescence length decreasing in series Li2MoO4-CsLiMoO4-Cs2MoO4, which is very important to study rare events, applications in optoelectronics and etc. The heat capacity of CsLiMoO4 single crystal was measured for the first time by differential scanning calorimetry in the temperature range of 320-1000 K. It was shown that there were no phase transitions for CsLiMoO4 single crystal in this temperature region, which made it promising for application in this temperature range.

Synthesis methods, thermodynamic and functional properties of compounds based on bismuth niobates doped with rare-earth elements (REEs) are presented. These compounds are promising materials for fuel cells, ceramic oxygen generators, electrocatalysis, etc. As show the data generalized, most compounds have a cubic structure of the δ-form of bismuth oxide, which has the highest ionic conductivity among solid-state ionic conductors. The compounds have high lattice enthalpy and are therefore promising high-energy compounds. The review summarizes studies on the basic thermodynamic characteristics of bismuth niobates doped with rare earth elements. The change in standard enthalpies of formation, lattice enthalpies, and heat capacity when replacing one rare earth element with another is analyzed. It is shown that as the radius of rare earth elements decreases, the standard enthalpies of formation increases and lattice enthalpies increases. The change in ionic conductivity with changes in temperature and rare earth element content has been studied. It has been shown that with increasing temperature and REE content, conductivity increases.