Determination of 200 °C Isothermal Section of Al-Ag-Ga Phase Diagram by Microanalysis,X-ray Diffraction,Hardness and Electrical Conductivity Measurements

Ternary Al-Ag-Ga system at 200 °C was experimentally and thermodynamically assessed. Isothermal section was extrapolated using optimized thermodynamic parameters for constitutive binary systems. Microstructure and phase composition of the selected alloy samples were analyzed using light microscopy, scanning electron microscopy combined with energy-dispersive spectrometry and x-ray powder diffraction technique. The obtained experimental results were found to be in a close agreement with the predicted phase equilibria. Hardness and electrical conductivity of the alloy samples from four vertical sections Al-Ag₈₀Ga₂₀, Al-Ag₆₀Ga₄₀, Ag-Al₈₀Ga₂₀ and Ag-Al₆₀Ga₄₀ of the ternary Al-Ag-Ga system at 200 °C were experimentally determined using Brinell method and eddy current measurements. Additionally, hardness of the individual phases present in the microstructure of the studied alloy samples was determined using Vickers microhardness test. Based on experimentally obtained results, isolines of Brinell hardness and electrical conductivity were calculated for the alloys from isothermal section of the ternary Al-Ag-Ga system at 200 °C.     

Identification of local compactions in ceramics

Fractures of non-fired samples and samples heat-treated in the temperature range 900–1200°C made of a mixture of tinted granules molded at various pressure levels and non-tinted powder are investigated. It is demonstrated that a crack propagates along the boundaries of the granules simulating local compaction areas, and after firing at 1050 – 1100°C, the fracture becomes more level. At the same time, the system (the sample) passes to an unstable state which has the properties of a bifurcation. An increase in the heating rate from 2.5 to 6.5°C/min produces a shift in the transition from an uneven to a level fracture depending on the initial granule density (granule molding pressure). The identification and elimination of the principal bifurcations in a technological process opens up the possibility of developing ceramics with reproducible structure and properties.     

Selecting a retrofitting profile for the TGME-444 boiler at the Rostov TETs-2 cogeneration station

Hydraulic misalignments in the steam superheating surfaces and possible changes in the thermal circuit of a TGME-444 boiler are analyzed, and the retrofitting version of this boiler that was drawn up from the results of this analysis and implemented at the Rostov TETs-2 cogeneration station in 2007 is presented. The improvement in the operational reliability of the retrofitted boiler is demonstrated.     

Catalytic systems based on carbon fiber materials for the low-temperature oxidation of carbon monoxide

New heterogenized catalytic systems for the low-temperature oxidation of CO were synthesized by supporting solutions of Pd, Cu, and Fe salts on carbon fibrous materials (carbopon and busofit). The carbon supports were studied by elemental analysis, SEM, TGA, and TPD. The effects of the nature of the support, the concentration and composition of the active component, and the conditions of preparation on the efficiency of the catalytic system were studied. It was ascertained that attenuation of hydrophilic properties of the support led to the decrease in system activity. The investigation of the catalysts by XPS showed that sample treatment in the reaction medium results in redistribution of the components of the active phase in the near-surface layer of the catalyst. The catalytic system based on carbon fibrous material carbopon prepared by supporting active components (Pd, Cu, and Fe salts) in three stages with intermediate activation in the reaction medium ensures 95% conversion of CO under respiratory conditions, and is promising for the design of the main element of breathing masks on its basis.     

Spectral diagnostics of vapor composition over molten Na<Subscript>2</Subscript>WO<Subscript>4</Subscript> and Na<Subscript>2</Subscript>O-BaO-B<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The high-temperature Raman spectra recording technique was found applicable also to study luminescence of atoms and individual molecular groups in vapors over some overheated molten compounds. Sodium atomic luminescence excited with a yellow (578.2 nm) copper vapor laser line was detected in vapors over overheated molten Na₂WO₄ and Na₂O-BaO-B₂O₃ system. The possibility of recording the sodium doublet spectrum by excitation with the 578.2 nm copper vapor laser line in vapors of any melts containing sodium was shown. Overheated melts in the Na₂O-BaO-B₂O₃ system disproportionate and lose boron oxide as evidenced by the recording of luminescent spectra of BO₂ molecular radicals in vapors over relevant melts.     

Experience with drilled in-situ injected pile use in Krasnoyarsk

Experience with use of cast-in-place piles with stabilization of the soils beneath their bases by the method of grouting is described. Ranges of effective application of these piles are indicated.     

Effect of intraband carrier relaxation on the threshold characteristics of quantum well lasers

The effect of intraband carrier relaxation on the threshold characteristics of InGaAsP quantum well (QW) lasers is studied. The dependence of the intraband hole-hole relaxation time τ _int on temperature and carrier density is analyzed. It is shown that taking into account the finiteness of τ _int and its dependence on temperature and carrier density strongly affects the gain and the threshold current density of QW lasers.