[en] The temperature-dependent heat capacity of three high-purity (1–x)(0.75TeO₂–0.25WO₃) + xLa₂O₃ tellurite glass samples (x = 0.02, 0.04, and 0.06) has been determined by dynamic calorimetry in the range 320–1000 K. The experimental devitrification and heat capacity data have been used to evaluate standard thermodynamic functions: C_p^o(T), enthalpy, entropy, and Gibbs energy in glassy and supercooled liquid states. We have demonstrated model-parameter similarity of properties in a statistical approach and found correlation relationships for parameters as functions of composition, which make it possible to predict the thermodynamic functions of unexplored glasses of this series. We have identified crystallization-resistant compositions of (1–x)(0.75TeO₂–0.25WO₃) + xLa₂O₃ glasses as a basis for the development of optically active elements.

[en] Using MCVD, we have produced optically active fibers with a glass-ceramic core containing mullite, 3Al₂O₃ · 2SiO₂, as a major crystalline phase. Thermodynamic prediction of mullite formation conditions has been supplemented by thermal analysis and X-ray diffraction characterization of preform core samples, and fiber heat treatment (annealing) conditions have been established. Luminescence measurements for the fibers annealed under optimal conditions demonstrate that optically active chromium has a crystalline local environment.

[en] 

Abstract—

Using thermal analysis, we have studied the decomposition of self-propagating high-temperature synthesis precursors consisting of scandium nitrate (oxidant) and three types of fuel: scandium acetate, scandium acetylacetonate, and glycine. Comparison of thermogravimetry and differential scanning calorimetry data for starting reagents and reaction mixtures indicates that the initiation of chemical reactions underlying SHS is associated with the thermal destruction of the oxidant. Analysis of the obtained data in terms of a modified Sestak–Berggren method has been used to assess kinetic characteristics of interaction between reactants in the reaction systems studied.

[en] A procedure for simulating gas-dynamic and thermal conditions during the conversion in a radiofrequency induction (RFI) plasma reactor has been developed. The model includes a turbulent flow of a mixture of ideal viscous compressible gases, taking into account inductive heating of the gas through heat conduction, convection, and radiation, considering the effect of the electromagnetic field force on the plasma motion. The formation of powder particles agrees with the results of thermodynamic calculations; the distribution of particles in the flow is described by the diffusion mechanism. The results of the simulation of the conversion of volatile boron chloride and boron fluoride in an RFI plasma torch with vortex-stabilized flow are presented.

No abstract available