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Pb10 –xSmx(GeO4)2 +x(VO4)4 –x (x = 0.2, 0.5, 0.7, 1.0) compounds with the apatite structure have been synthesized by firing appropriate mixtures of the PbO, Sm2O3, GeO2, and V2O5 oxides in air at temperatures from 773 to 1073 K. Their crystal structure has been studied using X-ray diffraction, and their high-temperature heat capacity (350–1000 K) has been determined by differential scanning calorimetry. The data have been used to evaluate their thermodynamic properties. [ABSTRACT FROM AUTHOR]

Sequential annealing of stoichiometric mixtures of CaCO3, Pr6O11(Nd2O3), and GeO2 in air at 1423–1473 K yields germanates CaPr2Ge3O10 and CaNd2Ge3O10. Their crystal structure is refined via X-ray diffraction. The high-temperature heat capacity (320–1000 K) is measured by means of differential scanning calorimetry. The thermodynamic properties of germanates are calculated using experimental dependences Cp = f(T). [ABSTRACT FROM AUTHOR]

Copper samarium germanate CuSm2Ge2O8 have been synthesized by the ceramic method from CuO, Sm2O3, and GeO2 in air at the final calcination temperature 1273 K (200 h), and its crystal structure has been determined (space group Cm; a = 9.7592(2) Å, b = 15.2608(4) Å, c = 8.2502(2) Å, β = 148.2566(8)°, V = 646.46(3) Å3). The temperature dependence of the molar heat capacity Cp= f(T) measured in the temperature range 350–1000 K shows a maximum at Tmax = 498.5 K caused by the phase transition. Thermodynamic properties have been calculated from experimental data. [ABSTRACT FROM AUTHOR]

The results of a study of the features of the dissolution processes of metallic platinum, rhodium, and iridium in hydrochloric acid solutions under hydrothermal autoclave conditions are presented. Hydrogen peroxide is used as an oxidizing agent. Solid and liquid phases are brought into contact after reaching a predetermined temperature, which is critically important in the study of the kinetics of dissolution of rhodium black and platinum plate due to the high rates of these processes. The concentrations of the metals in solutions are determined by atomic absorption spectroscopy and inductively coupled plasma mass spectrometry. The forms of chlorocomplexes of rhodium, iridium, and platinum in solutions are determined with a spectrophotometric method. As a result of the experiments, the modes of quantitative dissolution of a platinum plate and rhodium (in the form of affined powder and a plate) are determined and it is shown that, at 210°C in a medium of 6M hydrochloric acid with the addition of 5 vol % hydrogen peroxide, iridium taken in the form of affined powder dissolved by 50% in over 50 h, while the platinum plate dissolved completely at 130°C in about 120 min. An analysis of kinetic data using the shrinking core model showed that the rate determining the steps of the dissolution of rhodium black and affined rhodium and iridium powders under autoclave conditions were the chemical reactions. These results can be used both in analytical chemistry for quantitatively determining inert platinum metals and in refining production to improve the technology for processing raw materials containing platinum group metals (PGMs) and to optimize approaches to the synthesis of pure chlorocomplex compounds of PGMs. [ABSTRACT FROM AUTHOR]

The reduction of divalent nickel with hydrazine hydrate from alkaline ammonia solutions at elevated temperatures was studied. A procedure to synthesize finely divided nickel powders was proposed. The morphology of the objects obtained under various synthesis conditions was investigated by scanning electron microscopy; it was shown that both needle-like and spherical particles can form. The specific surface area of the synthesized metallic nickel powders was determined by low-temperature nitrogen adsorption to be within the range 5–20 m2/g, depending on the synthesis conditions (the concentration of the initial salt in the solution, the pH, and the temperature). X-ray powder diffraction analysis showed that all the powders are mixtures of two phases: nickel (to 99%) and nickel hydroxide. X-ray photoelectron spectroscopy demonstrated that a particle of the powders consists of a nickel(0) core coated with several atomic layers of nickel hydroxide. [ABSTRACT FROM AUTHOR]

The hydrothermal formation of Pd and Pt nanoparticles on carbon nanotubes (CNT) and the subsequent reduction of gold from solutions in these systems were investigated. It was found that upon contact of composites Pd/CNT and Pt/CNT (6.0 wt.%) with hydrogen tetrachloroaurate(iii) solutions in an autoclave, bimetallic particles Pd-Au and Pt-Au, respectively, are formed. The sample composition, structure, and size was investigated by powder X-ray diffraction, scanning and transmission electron microscopy with local energy-dispersive X-ray fluorescence analysis, X-ray photoelectron spectroscopy, and nitrogen gas adsorption. [ABSTRACT FROM AUTHOR]

The DyGaTi2O7 and EuGaTi2O7 titanates have been prepared by solid-state reactions in a starting mixture of Dy2O3 (Eu2O3), Ga2O3, and TiO2 via firing in air at temperatures of 1273 and 1573 K, and their crystal structure has been studied by X-ray diffraction. Their high-temperature heat capacity (350–1000 K) has been determined by differential scanning calorimetry. The Cp(T) experimental data have been used to calculate the thermodynamic functions of the titanates. [ABSTRACT FROM AUTHOR]

Bi4–xNdxTi3O12 (x = 0.4, 0.8, 1.2, 1.6) bismuth neodymium titanate solid solutions have been prepared by solid-state reactions, via firing of mixtures of their constituent oxides in air at temperatures from 1003 to 1323 K. The crystal structure of the synthesized phases has been determined by X-ray diffraction. The results demonstrate that increasing the neodymium concentration leads to a morphotropic phase transition from the orthorhombic structure (sp. gr. B2cb) of the parent phase Bi4Ti3O12 (which persists at x = 0.4 and 0.8) to a tetragonal structure (sp. gr. P42/ncm) at x = 1.2 and 1.6. The heat capacity of the synthesized bismuth neodymium titanate samples has been determined by differential scanning calorimetry in the temperature range 320–1000 K. The Cp(T) curves of the Bi4– xNdxTi3O12 samples with x = 0.4 and 0.8 have been shown to have extrema due to their ferroelectric phase transition. [ABSTRACT FROM AUTHOR]

The apatite-like Pb9Pr(GeO4)3(VO4)3 and Pb9Sm(GeO4)3(VO4)3 compounds were prepared by solid-phase synthesis using oxides as starting chemicals: PbO, Pr2O3 (Sm2O3), GeO2, and V2O5. The successive annealing was carried out at 773–1073 K in the air. The effect of rare-earth elements on the structure of the Pb9R(GeO4)3(VO4)3 (R = La, Pr, Nd, Sm) apatites and basic thermodynamic functions was investigated. The temperature dependence (350–1050 K) of the heat capacity of the Pr(Sm)-containing apatites has been determined by differential scanning calorimetry. It has been established that the Cp = f(T) curve for the Pb9Pr(GeO4)3(VO4)3 compound has an extremum associated with a polymorphic transformation in the region of 978 K. [ABSTRACT FROM AUTHOR]

The RxBi2– xGeO5 (R = Sm–Yb, Y) and BiGeO5 (R1 = Y, R2 = Pr, Nd) germanates have been prepared by solid-state reactions, by sequential firing of oxide mixtures in air in the temperature range 1003–1223 K. Their heat capacity has been determined by differential scanning calorimetry. The Cp(T) data have been shown to be well represented by the classic Maier–Kelley equation in the range 350–1000 K. [ABSTRACT FROM AUTHOR]

At elevated temperatures (130 and 180°C) in hydrothermal autoclave conditions, the possibility of deep extraction of noble metals from poor intermediate products of refining (or affinage) production was investigated. The conditions (temperature, processing conditions) of leaching of impurity elements into the solution are determined, under which the uncontrolled distribution of precious metals according to the technological scheme is prevented and their concentration in the solid phase is ensured. It was found that the processing of the poor intermediate product in two stages (alkaline and acidic) under autoclave conditions makes it possible to increase the total content of noble metals in the solid phase from 0.5 to 17.5 wt %, which allows returning this product to the refining cycle. In this case, more than 99 wt % tellurium passes into a solution that does not contain impurities of noble metals and is suitable for further processing. [ABSTRACT FROM AUTHOR]

The PrFeGe2O7 and NdFeGe2O7 germanates have been prepared by solid-state reactions using stoichiometric mixtures of Pr2O3 (Nd2O3), Fe2O3, and GeO2 as starting oxides, which were sequentially fired between 1273 and 1473 K in air, and their high-temperature heat capacity has been determined by differential scanning calorimetry. The experimental Cp(T) data obtained have been used to evaluate their thermodynamic properties. [ABSTRACT FROM AUTHOR]

Germanates InFeGe2O7 and GdFeGe2O7 have been produced in the form of polycrystalline powders from stoichiometric mixtures of In2O3 (Gd2O3), Fe2O3, and GeO2 by solid-phase synthesis. Calcination was carried out in air in the temperature range 1273–1473 K. The high-temperature heat capacities of these oxide compounds have been measured using differential scanning calorimetry. The resulting experimental Cp = f(T) data were used to calculate the thermodynamic functions (the enthalpy and entropy changes) of the investigated Fe–In and Fe–Gd germanates. [ABSTRACT FROM AUTHOR]

The Bi12TiO20, Bi4Ti3O12, and Bi2Ti4O11 bismuth titanates have been prepared by solid-state reactions, via multistep firing of stoichiometric mixtures of their constituent oxides in air at temperatures from 1003 to 1273 K (Bi12TiO20, to 1123 K). The heat capacity of polycrystalline samples of the synthesized compounds has been determined by differential scanning calorimetry in the temperature range 330–1050 K. The Cp(T) curves of Bi4Ti3O12 and Bi2Ti4O11 show peaks at temperatures of 943 and 509 K, respectively, due to ferroelectric phase transitions. The experimental data have been used to evaluate the enthalpy increment, entropy change, and reduced Gibbs energy change of the bismuth titanates. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of gallium neodymium germanate NdGaGe2O7 were synthesized by solid-phase reactions from a stoichiometric mixture of oxides Nd2O3, Ga2O3, and GeO2 under sequential stepwise calcination in the air at temperatures in the range 1273–1473 K. The heat capacity–temperature dependence for the synthesized samples was studied by differential scanning calorimetry in the range 350–1000 K. The experimental Cp = f(T) data were used to calculate the thermodynamic functions (enthalpy, entropy, and reduced Gibbs energy changes) of NdGaGe2O7. [ABSTRACT FROM AUTHOR]

The YbInGe2O7 and LuInGe2O7 germanates have been prepared by solid-state reactions using stoichiometric oxide mixtures, which were sequentially fired at temperatures from 1273 to 1473 K in air, and their molar heat capacity has been determined by differential scanning calorimetry in the range 350‒1000 K. The experimental Cp(T) data obtained have been used to evaluate the enthalpy increment, entropy change, and reduced Gibbs energy of the rare-earth oxide compounds. [ABSTRACT FROM AUTHOR]

Gadolinium germanate, Gd2Ge2O7, has been prepared by solid-state reaction, via multistep firing in the temperature range 1273–1473 K, and its high-temperature heat capacity has been determined by differential scanning calorimetry. The Cp(T) data have been used to evaluate the thermodynamic functions (enthalpy increment, entropy change, and reduced Gibbs energy) of the oxide compound. [ABSTRACT FROM AUTHOR]

The EuBiGeO5 compound has been prepared from stoichiometric mixtures of Eu2O3, Bi2O3, and GeO2 by solid-phase synthesis with subsequent multistage annealing in the temperature range of 1003–1223 K. The molar heat capacity of polycrystalline bismuth europium germanate has been determined by differential scanning calorimetry in the temperature range 350–1000 K. The experimental temperature dependence of heat capacity Cp = f(T) contains no anomalies and can be fitted using the Maier–Kelley equation. The key thermodynamic functions of bismuth europium germanate (changes in enthalpy, entropy, and Gibbs free energy) have been calculated. [ABSTRACT FROM AUTHOR]

The R2Ge2O7 (R = Pr–Lu, Y) rare-earth germanates have been prepared by solid-state reactions by firing stoichiometric R2O3 + GeO2 mixtures in air at temperatures in the range 1273–1473 K. The unit-cell parameters (a, c, and V) of the R2Ge2O7 (R = Tb–Lu) compounds have been shown to be linear functions of the ionic radius of the rare-earth elements. The high-temperature heat capacity of polycrystalline samples of the germanates has been determined by differential scanning calorimetry in the temperature range 350–1000 K. The variation in the specific heat of R2Ge2O7 has been shown to be correlated with the dependence of the heat capacity of rare-earth oxides on the ionic radius of the rare-earth element within each tetrad. [ABSTRACT FROM AUTHOR]

The compounds DyInGe2O7 and HoInGe2O7 were synthesized by multistage calcination of stoichiometric mixtures of the constituent oxides (solid-phase synthesis) in air in the temperature range 1273–1473 K. The high-temperature heat capacities of polycrystalline samples of dysprosium–indium and holmium–indium mixed-cation germanates were measured by differential scanning calorimetry. The thermodynamic properties of the investigated oxides were calculated using the Cp = f(T) experimental data. [ABSTRACT FROM AUTHOR]

Dissolution of metallic rhodium in solutions of hydrochloric acid was studied under hydrothermal autoclave conditions. The influence exerted by various factors on the depth of rhodium(0) transfer to solution was examined. It was found that the quantitative dissolution of rhodium(0) is reached in a mixture of hydrochloric and hydrobromic acids in the presence of manganese dioxide at 20°C in autoclaves. The results obtained can be used both for an analytical determination of rhodium and for processing of rhodium-containing raw materials and synthesis of complex rhodium compounds. [ABSTRACT FROM AUTHOR]

SmFeGe2O7 germanate has been synthesized by solid-state reactions from stoichiometric mixtures of starting oxides using multistage sintering in the temperature range 1273‒1473 K. The effect of temperature on the heat capacity of the compound has been studied by differential scanning calorimetry. On the basis of the dependence Cp = f(T), the thermodynamic properties of this compound have been calculated. [ABSTRACT FROM AUTHOR]

Germanate Tb2Ge2O7 has been prepared by solid-phase synthesis from a stoichiometric mixture of Tb2O3 and GeO2 by sequential firing in air at temperatures of 1273–1473 K. The effect of temperature on its molar heat capacity has been studied by differential scanning calorimetry. According to the obtained dependence Cp = f(T), the thermodynamic properties (enthalpy and entropy changes and the reduced Gibbs energy) have been calculated, and the specific heat value at 298 K has been estimated. [ABSTRACT FROM AUTHOR]

Cu5V2O10 is prepared by solid-phase synthesis via sequential air calcination of a stoichiometric CuO-V2O5 mixture. Its high-temperature heat capacity is measured by differential scanning calorimetry. The thermodynamic properties (enthalpy and entropy changes and scaled Gibbs free energy) are calculated using the experimental dependence Cp =f(T). It is shown that specific heat capacity correlates with the composition of oxides in the CuO−V2O5 system. [ABSTRACT FROM AUTHOR]

The Gd2Ti2O7 and Lu2Ti2O7 titanates (pyrochlore structure, sp. gr. Fd3m) have been prepared by solid-state reactions in air at temperatures from 1673 to 1773 K using the Gd2O3, Lu2O3, and TiO2 oxides as starting materials. Their high-temperature heat capacity has been determined by differential scanning calorimetry in the range 350–1000 K. The experimental heat capacity data have been used to evaluate the thermodynamic functions of gadolinium and lutetium dititanates. [ABSTRACT FROM AUTHOR]

Tm2Ge2O7 and TmInGe2O7 germanates are obtained via solid-phase synthesis from stoichiometric mixtures of initial oxides through multi-stage annealing in the temperature range 1273–1473 K. The heat capacity of oxide compounds is measured using differential scanning calorimetry. The temperature dependences of enthalpy, enthropy, and normalized Gibbs energy are calculated from the resulting experimental data. [ABSTRACT FROM AUTHOR]

Behavior of the concentrate of platinum-accompanying metals in autoclave conditions was studied with the use of various solvents: water and aqueous solutions of formic acid, sulfuric acid, and sodium hydroxide. The quantitative values of the recovery of noble metals and impurity nonferrous elements from the concentrate were found. It was shown that the best results are obtained with a preliminary calcination of the concentrate, followed by an autoclave treatment of the cinder in sulfuric acid. In this case, the content of noble metals in the concentrate increases from 29 to 51% due to the selective removal of considerable amounts of impurity elements: tellurium, nickel, iron, copper, and arsenic. [ABSTRACT FROM AUTHOR]

Pb10 –xLax(GeO4)2 +x(VO4)4 –x (x = 0, 1, 3) compounds with the apatite structure have been prepared by solid-state reactions via multistep firing of appropriate oxide mixtures in air in the temperature range 773–1073 K. The heat capacity of the synthesized polycrystalline samples has been determined by differential scanning calorimetry. The experimental Cp(T) data have been used to evaluate the thermodynamic properties of the lead lanthanum germanatovanadates: enthalpy increment, entropy change, and reduced Gibbs energy. [ABSTRACT FROM AUTHOR]

Oxides Y0.65Pr0.35BiGeO5 and Y0.65Nd0.35BiGeO5 have been synthesized by a ceramic method. The heat capacity of fine crystalline samples has been studied in the range 350-1000 K by differential scanning calorimetry. The Cp = f(T) dependences can be described by the Maier-Kelley equation. The thermodynamic functions of these oxides—changes in enthalpy, entropy, and reduced Gibbs energy—have been calculated from the experimental data on high-temperature heat capacity. [ABSTRACT FROM AUTHOR]

Abstract—: Polycrystalline In2Ge2O7 and YInGe2O7 samples have been prepared by solid-state reactions, by sequentially firing stoichiometric mixtures of In2O3, Y2O3, and GeO2 at temperatures from 1273 to 1473 K. The molar heat capacity of the indium and yttrium indium pyrogermanates has been determined by differential scanning calorimetry in the range 320-1000 K. The experimental Cp(T) data have been used to evaluate the enthalpy increment, entropy change, and reduced Gibbs energy of In2Ge2O7 and YInGe2O7. [ABSTRACT FROM AUTHOR]

Polycrystalline HoBiGeO5 and ErBiGeO5 samples have been prepared by solid-state reactions, by firing stoichiometric mixtures of Ho2O3 (Er2O3), Bi2O3, and GeO2. The effect of temperature on the heat capacity of the synthesized compounds has been investigated by differential scanning calorimetry in the range 350-1000 K. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of bismuth holmium and bismuth erbium germanates: enthalpy increment, entropy change, and reduced Gibbs energy. [ABSTRACT FROM AUTHOR]

Neodymium dititanate, Nd2Ti2O7 (monoclinic structure, sp. gr. P21), has been prepared by solid-state reaction in air at temperatures from 1673 to 1773 K using the Nd2O3 and TiO2 oxides as starting materials. The high-temperature heat capacity of the resultant polycrystalline Nd2Ti2O7 samples has been determined by differential scanning calorimetry. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of neodymium dititanate (enthalpy increment H°(T)-H°(320 K), entropy change S°(T)-S°(320 K), and reduced Gibbs energy Ф°(T)) in the temperature range 320-1053 K. [ABSTRACT FROM AUTHOR]

Stable modification of palladium oxide and a material modeling the palladium-containing platinum-palladium concentrate poorly soluble in acids were synthesized. It was found that silica is dissolved in alkaline solutions of sodium formate, and palladium oxide is quantitatively reduced under autoclave conditions, which improves the parameters of the subsequent hydrochlorination of the concentrate. Raising the temperature results in that the separation of the palladium phase from alkaline solution is improved and enables separation via decantation. [ABSTRACT FROM AUTHOR]

The Dy2Ge2O7 and Ho2Ge2O7 pyrogermanates have been prepared by solid-state reactions in several sequential firing steps in the temperature range 1237-1473 K using stoichiometric mixtures of Dy2O3 (or Ho2O3) and GeO2. The heat capacity of the synthesized germanates has been determined as a function of temperature by differential scanning calorimetry in the range 350-1000 K. The experimentally determined Cp(T) curves of the dysprosium and holmium germanates have no anomalies and are well represented by the Maier-Kelley equation. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of the Dy2Ge2O7 and Ho2Ge2O7 pyrogermanates: enthalpy increment H°(T)-H°(350 K), entropy change S°(T)-S°(350 K), and reduced Gibbs energy Ф°(T). [ABSTRACT FROM AUTHOR]

Various palladium-carbon composites have been manufactured by autoclaving at 170°С to be used as precursors for manufacturing bimetallic particles. The morphology of the manufactured items was comprehensively studied by scanning electron microscopy; the ultrafine metal palladium was found to have particles sizes lying in the range 30-120 nm. The specifics of hydrothermal reduction of gold(III) chloro complexes by palladium-carbon composites at 110°С have been studied. An appreciable increase in gold(III) reduction rate was observed with the use of a palladium-carbon composite relative to the rate observed for ultrafine metallic palladium. Gold is reduced on a palladium-carbon composite to an individual metallic phase. [ABSTRACT FROM AUTHOR]

The Sm2Ge2O7 and Eu2Ge2O7 germanates have been prepared by solid-state reactions via multistep firing of stoichiometric mixtures of Sm2O3 (Eu2O3) and GeO2 in air at temperatures from 1273 to 1473 K. The molar heat capacity of the samarium and europium germanates has been determined by differential scanning calorimetry in the range 350-1000 K and the Cp(T) data have been used to evaluate their thermodynamic properties. [ABSTRACT FROM AUTHOR]

The Pb8La2(GeO4)4(VO4)2 and Pb8Nd2(GeO4)4(VO4)2 germanatovanadates with the apatite structure have been prepared by solid-state reactions, by sequentially firing stoichiometric mixtures of PbO, La2O3 (Nd2O3), GeO2, and V2O5 in air at temperatures of 773, 873, 973, and 1073 K. The effect of temperature on the heat capacity of the resultant polycrystalline samples has been studied by differential scanning calorimetry at temperatures from 350 to 950 K using polycrystalline samples. The experimental Cp(T) data have been used to evaluate the thermodynamic functions of the lead lanthanum and lead neodymium germanatovanadates. [ABSTRACT FROM AUTHOR]

ErInGe2O7 and TbInGe2O7 have been synthesized from the parent oxides by a ceramic method through the multistep annealing in air in the temperature range 1273–1473 K. The high-temperature heat capacity of these oxides has been measured by the differential scanning calorimetry method (350–1000 K). Their thermodynamic properties have been calculated from the experimental dependences Cp = f(T). [ABSTRACT FROM AUTHOR]

Examines the thermodynamic properties of the gold (Au)-bismuth (Bi) system. Melting points of pure Au and Bi; Simplicity of the Au-Bi system; Measurement of the enthalpy of liquid bismuth; Observations on the heat of mixing of the Au-Bi alloys over the entire concentration.