Structure and Electronic Spectrum of Fullerene-like Nanoclusters Based on Mo, Nb, Zr, and Sn Disulfides

Modeling results are presented on the atomic structure, electronic spectra, and interatomic interaction parameters of quasi-zero-dimensional fullerene-like nanoparticles of Mo, Nb, Zr, and Sn disulfides. These characteristics are analyzed in relation to the chemical composition, size, and atomic configuration of the nanoparticles and are compared to those of nanotubes and crystals of the corresponding disulfides.     

Microstructure and electric conductivity of composite (BeO + TiO<Subscript>2</Subscript>) ceramics

Specimens of composite (BeO + TiO₂) ceramics with TiO₂ added in an amount of 5, 10, 20, 30, and 40 mass% are obtained. The temperature dependence of the conductivity of the (BeO + 30 mass % TiO₂) ceramics is studied. Conduction is ensured by the titania additive present in the ceramics in a strongly reduced state. The maximum temperature (950 K) at which the (BeO + 30 mass % TiO₂) ceramics preserves its conductive properties in air for a long time and, possibly, the capacity to efficiently absorb microwave radiation is determined. Heating in air at a temperature exceeding 960 K is accompanied by the processes of oxidation of reduced TiO₂, which causes disordering of the structure and lowering of the conductivity. An electron microscope study is used to show that the distribution of TiO₂ in the BeO of the [BeO + (5, 10, and 30 mass %) TiO₂] system is nonuniform; inclusions of large regions of grouped TiO₂ microcrystals are encountered. This affects the physicochemical properties of the ceramics, the thermal and electrical conductivities in particular. In order to ensure a uniform distribution of TiO₂ in the volume of the ceramics it is recommended to introduce the dioxide into the composition of the BeO powder from solutions (hydrochemical method). __________ Translated from Novye Ogneupory, No. 11, pp. 68–74, November, 2007.     

Calculating the thermally stressed state of the high and medium pressure rotors of a T-250/300-240 turbine in the labyrinth seal zone

The temperature and thermally stressed state of the high and medium pressure rotors of the T-250/300-240 district heating steam turbine are calculated, taking into account the concentration of stresses in the neighborhood of the thermal grooves in labyrinth seals. “Critical” zones in the turbine rotors, within which thermal stresses limit the rate of startup, are determined. Some practices for reducing the temperature stresses are suggested. __________ Translated from élektricheskie Stantsii, No. 1, pp. 32–37 (2008).     

Single crystals and light-transmitting BeO-ceramic for electronic technology

Problems are discussed for the preparation and physicochemical properties of beryllium oxide and light-transmitting BeO-ceramic as promising materials for electronic technology.     

Quantum chemical study of the electronic structure of new nanotubular systems: α-graphyne-like carbon, boron-nitrogen and boron-carbon-nitrogen nanotubes

Single-wall BN and BCN nanotubes in assumed α-graphyne-like wall structures are studied by means of the tight-binding band theory. The electron density of states, total energies and interatomic bond indices (crystal orbital overlap populations) are analyzed as a function of the composition, atomic structure and diameters of zigzag and armchair BN and BCN tubes. The results obtained are compared with the electronic properties of α-graphyne carbon- and graphite-like BN nanotubes.     

Calcium Production by the Electrolysis of Molten CaCl2—Part I. Interaction of Calcium and Copper-Calcium Alloy with Electrolyte

This paper describes the interaction between calcium and molten CaCl₂ and the solubility of calcium in this melt, depending on the calcium content in the copper-calcium alloy that comes in contact with the molten CaCl₂. The negative influence of the dissolved calcium on the current efficiency was verified. The negative effects of moisture and CaO impurities on the calcium current efficiency were demonstrated. The dependence of the current efficiency and the purity of the metal obtained by the electrolysis conditions were studied in a laboratory electrolyzer (20 to 80 A).     

Diffusion-chemical and phase resistance during condensation and evaporation of alkali metals

It is shown that, for s.v.p, in the range 1–100 mm Hg, evaporation (condensation) of alkali metals goes via liberation (absorption) of both monatomic and diatomic molecules by the liquid surface. In this pressure range, dimerization (dissociation) occurs as the result of a chemical reaction at the liquid surface, and the coefficients of condensation of monatomic and diatomic molecules are close to unity.Translated from Atomnaya Énergiya, Vol. 21, No. 1, pp. 17–22, July, 1966.