A. M. Kut’in

Self-propagating high-temperature synthesis of Y2O3 powders from Y(NO3)3x(CH3COO)3(1 − x) · nH2O

We have studied the self-propagating high-temperature synthesis (SHS) of yttrium oxide from Y(NO3)3x(CH3COO)3(1 − x) · nH2O (0.3 ≤ x ≤ 0.7) acetate nitrates, calculated their standard enthalpies of formation using the method of valence states of atoms in a chemical compound, and compared calculated and experimentally determined yttrium oxide SHS temperatures. Using thermogravimetry and differential scanning calorimetry data and thermodynamic analysis, we have determined the optimal range of yttrium acetate nitrate compositions for the SHS of Y2O3 powder.

Preparation of high-purity TeO2-ZnO glass batches

Tellurium oxide-zinc oxide glass batches have been prepared through chemical vapor deposition from tellurium and zinc alkyl compounds in an oxyhydrogen flame onto the lateral surface of rotating cylindrical substrates. The composition of the deposits has been shown to be determined by the relative amounts of the metalorganic precursors in the gas phase. Varying the deposition conditions, we obtained both amorphous and crystalline deposits, with concentrations of metallic impurities below 1 ppmw. Melting the deposits, we prepared high-purity (TeO2)1 − x(ZnO)x (0.15 ≤ x ≤ 0.35) glasses.

Obtaining Nanodisperse Powders of Neodymium-Activated Yttrium Aluminum Garnet by Self-Propagating High-Temperature Synthesis Method

Nanosized slightly agglomerated powders of neodymium-activated yttrium aluminum garnet (YAG:Nd) were obtained by a self-propagating high-temperature synthesis method. An increase in content of reducing substituents in metal-organic complexes as compared to oxidizing substituents leads to an increase in average size of the forming grains from 23 to 70 nm; thereupon, a decrease in powder agglomeration degree is observed. Firing of x-ray amorphous powders results in formation of polycrystalline YAG:Nd without forming intermediate phases.

Vapor pressure and thermodynamic functions of TeI4 and its decomposition products

Using a flow method, we have measured the vapor pressure of tellurium tetraiodide, an attractive reagent for chemical vapor deposition technology. The results, combined with earlier tensimetric data, have been used to evaluate the basic thermodynamic functions of TeI4 and its thermolysis products.

A mathematical model for analysis of sequentially coupled crystallization–melting differential scanning calorimetry peaks and the use of the model for assessing the crystallization resistance of tellurite glasses

Differential scanning calorimetry (DSC) characterization of tellurite glasses doped with lanthanum oxide, which improves their crystallization resistance, has revealed a phase transformation specific to such glasses, in which partial crystallization of a sample is followed by melting of the crystals formed. The experimentally observed dependence of the decrease of crystallization–melting peaks across a series of disperse samples of (TeO2)0.72(WO3)0.24(La2O3)0.04 glass with increasing particle size upon extrapolation to the size of a bulk sample has been used to assess the crystallization resistance of tellurite glasses for optical applications. The assessment technique comprises DSC characterization of particle-size-classified glass samples and the use of a mathematical model for obtaining the degree of crystallization as a function of temperature and time, α(T, t) through analysis of nonisothermal DSC peaks representing a partial glass crystallization process passing into melting. The crystallization resistance of glass is estimated by extrapolating the maximum α values as a function of particle size to a preform size. Tested for (TeO2)0.72(WO3)0.24(La2O3)0.04 glass, the technique offers the possibility of selecting preforms for producing fibers from compositionally new, chemically pure tellurite glasses at a given phase purity level.

Crystallization kinetics of (TeO2)1–x(MoO3)x glasses studied by differential scanning calorimetry

A technique has been proposed for assessing kinetic characteristics (parameters) of glass crystallization from mathematical data processing results for glass crystallization peaks, with allowance for nonisothermal conditions of differential scanning calorimetry. The technique has been used to analyze the crystallization behavior of (TeO2)1–x(MoO3)x (x = 0.25–0.55) glasses, which has made it possible to evaluate crystallization parameters and derive their regression dependences on glass composition. Basic to glassy materials research is that the proposed approach includes a parametrically defined, explicit functional dependence of the degree of crystallization on time and temperature, α(t, T), as a basis for optimizing glass heat treatment conditions in terms of this characteristic and predicting such conditions from regression relationships for previously unexplored compositions in the tellurite–molybdate glass system studied.

Chemical and physical transformations in Ge-S-I glass preparation

Vapor pressure measurement results for a mixture of germanium tetraiodide and sulfur in the temperature range 150–300°C have been analyzed in terms of conditionally equilibrium states, and the degree of GeI4 conversion and temperature-dependent compositions of the condensed and vapor phases have been determined. We have obtained a consistent thermodynamic data set necessary for optimizing the preparation of Ge-S-I glasses from germanium tetraiodide and sulfur.

Thermodynamic properties of (TeO2)0.95 − n − z (ZnO) z (Na2O) n (Bi2O3)0.05 glasses

AbstractThe heat capacity (Cp0) of the tellurite glasses

Thermophysical properties and crystal structure of high-purity monoisotopic 80Se

\begin{gathered} (TeO_2 )_{0.70} (ZnO)_{0.15} (Na_2 O)_{0.10} (Bi_2 O_3 )_{0.05} (I), \hfill \\ (TeO_2 )_{0.75} (ZnO)_{0.10} (Na_2 O)_{0.10} (Bi_2 O_3 )_{0.05} (II),and \hfill \\ (TeO_2 )_{0.75} (ZnO)_{0.15} (Na_2 O)_{0.05} (Bi_2 O_3 )_{0.05} (III) \hfill \\ \end{gathered}

Thermodynamic analysis of the self-propagating high-temperature synthesis of scandium and lutetium oxides nanopowders

has been measured in the temperature range 255–750 K using a differential scanning calorimeter (glasses I–III) and in the range 208–325 K using an adiabatic calorimeter (glass II). We have determined the temperature ranges of the glass transition, evaluated the thermodynamic characteristics of the glass transition and glassy state, and estimated the crystallization onset temperatures. Using the experimental data and a statistical model approach, we have calculated the standard thermodynamic functions for glassy and “supercooled liquid” states in the temperature range 0–740 K: heat capacity Cp0(T), enthalpy H0(T) − H0(0), entropy S0(T) − S0(0), and Gibbs function G0(T) − G0(0).