V. V. Ryabov

Construction of viscosity diagrams for CaO–SiO 2 –Al 2 O 3 –8% MgO–4% B 2 O 3 slags by the simplex lattice method

The simplex lattice method of planning experiments is used to study the viscosities of CaO–SiO2–Al2O3–8% MgO–4% B2O3 slags in a wide chemical composition range. For each viscosity, we developed an adequate mathematical model in the form of a reduced third-order polynomial. The results of mathematical simulation are presented in composition–viscosity diagrams. Composition regions with a high fluidity of slags, the viscosities of which are 0.8–1.2 Pa s in the temperature range 1500–1600°C, are indicated in the diagrams.

High-temperature heat capacity of samarium and erbium titanates with pyrochlore structure

Titanates Sm2Ti2O7 and Er2Ti2O7 with pyrochlore structure have been prepared by solid-phase synthesis in air from stoichiometric Sm2O3 (Er2O3)–TiO2 mixtures sequentially at 1673 and 1773 K. Hightemperature heat capacity of the oxide compounds has been determined by differential scanning calorimetry. Their thermodynamic properties have been calculated from experimental temperature dependence Cp = f(T).

Influence of the mechanical activation of REE oxides on the electrical conductivity of borate melts

The influence of the mechanical activation of oxides M2O3 (La2O3, Ce2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Yb2O3, and Lu2O3) on electrical conductivity (æ) of the B2O3-M2O3 molten systems is investigated. It is assumed that the majority carriers in these melts can be protons which enter the melts due to the hydration of B2O3. The variation in the magnitude of for various M2O3 contents is explained by the corresponding variation in the structure of structural units as a result of the dissociation of the boron-oxygen groups, which include the OH groups. The activation energy of electrical conductivity in the B2O3-M2O3 melts increases due to the decay of superstructural units [B3O4.5] and B3O3O3/2OH as the temperature increases. The dependence of is found. In the B2O3-La2O3 → B2O3-Lu2O3 melts series, this energy follows the intraseries periodicity, which depends on the stabilization energy of fundamental terms of the ions of rare-earth elements (REE).

Effect of zirconium and molybdenum oxides on the viscosity and the electrical conductivity of oxide-fluoride slags

The effect of additions of zirconium and molybdenum oxides on the viscosity and the electrical conductivity of oxide-fluoride slags is studied using a vibration viscometry and an ac bridge.

Effect of mechanical activation of rare-earth metal oxides on the viscosity of borate melts

Effect of mechanical activation of yttrium-group rare-earth metal (REM) oxides on the viscosity of borate melts is studied. The concentration of Gd, Dy, Ho, and Lu oxides is found to affect the viscosity and solidification temperature of these melts.

Effect of titanium and molybdenum oxides on viscosity and electrical conductivity of oxide-fluoride slags

The effect of additives of titanium and molybdenum oxides on the viscosity and electrical conductivity of the Al2O3-CaO-CaF2 oxide-fluoride slag melts at 1750–1950 K is investigated by vibration viscosimetry and the ac bridge method. Crystallization intervals are established depending on the variation in the TiO2 and MoO3 concentrations in the melts from 0 to 25%, and it is revealed that the majority charge carriers are calcium and fluorine ions. These data indicate the complex-forming character of the behavior of Ti and Mo in aluminum-calcium oxide-fluoride melts.

Viscosity and conductivity of melts of the GeO2-PbO system

The temperature dependence of the viscosity and conductivity of melts of the GeO2-PbO system containing 25, 40, 50, 62.5, 66.8, and 75 mol % PbO is measured. The results are attributed to the structure of the studied melts. It is shown that current-carrying ions also determine the viscous flow.

Viscosity of niobium-containing oxide-fluoride melts

Influence of Nb2O5 on viscosity of the CaF2-based and CaF2-30% Al2O3-based melts was investigated using a vibration viscosimetry method in the range 1523–1873 K. It is found that viscosity of the melts rise and the crystallization range shifts to lower temperatures as the Nb2O5 concentration increases from 0 to 25 wt %. The activation energy of viscous flow increases from 34 to 110 kJ mol−1 and from 56 to 148 kJ mol−1 for the CaF2-based and CaF2-30% Al2O3-based melts, respectively. The obtained data indicate the complexing behavior of niobium in the oxide-fluoride melts.

Synthesis and High-Temperature Heat Capacity of Neodymium Titanate

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.

High-temperature heat capacity of erbium titanate with a pyrochlore structure

Erbium titanate with a pyrochlore structure has been synthesized by a ceramic method from stoichiometric Er2O3–TiO2 mixtures at 1673–1773 K. The high-temperature heat capacity of Er2Ti2O7 (320–1000 K) has been studied by differential scanning calorimetry. The thermodynamic functions of this oxide compound—enthalpy and entropy changes and reduced Gibbs—have been calculated from the experimental dependence CP = f(T).