Critical Heat Flux in Vertical Steam-Generating Channels in the Absence of Circulation of Heat-Transfer Agent: Critical Power of Channels of Different Shapes

An experimental investigation is performed of the critical heat flux in vertical channels in the absence of circulation of heat-transfer agent through the lower cross section. Experiments are performed in tubes 30, 40, and 80 mm in diameter, as well as in 19- and 40-rod assemblies. Equations are suggested for the calculation of critical power, which are valid in a wide range of the geometric and process parameters, including at a low pressure.     

Oxidation resistance before and after heat treatment for compacted Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiC–C mixtures with aluminum-chromium-phosphate binder

Oxidation resistance has been examined for compacted Al₂O₃–SiC–C mixtures, which contain an aluminum-chromium-phosphate binder without firing (DTA method) and ones that have been previously fired and given isothermal heat treatment at 800°C (as indicated by the mass loss). To obtain oxidation-resistant materials, the content of silicon carbide should not exceed 10 wt.% and the recommended graphite content is not more than 20 wt.%. Translated from Novye Ogneupory, No. 2, pp. 38 – 43, February, 2009.     

Service experience of refractory products and mixtures in metallurgical plant lining at the Magnitogorsk Metallurgical Works

The authors describe the experience of production of refractories and mixtures and their service in blast furnaces and steel melting, as well as the service of corundum-graphite products for protecting metal strands on machines for continuous slab casting. __________ Translated from Novye Ogneupory, No. 8, pp. 9–11, August, 2007.     

Ion-beam-induced modification of the electrical properties of vacancy-doped mercury cadmium telluride

The effect of ion-beam milling (IBM) on the electrical properties of vacancy-doped mercury cadmium telluride (MCT) p-Hg_1−x Cd _x Te (x ∼ 0.22) has been studied. The samples were prepared by thermal annealing of molecular beam epitaxy (MBE)-grown heterostructures and the films and single crystals grown by liquid-phase epitaxy (LPE). The etching of samples by IBM resulted in the formation of donor centers. In MBE-grown heterostructures (but not in LPE-grown samples), the concentration of these centers reached ∼10¹⁷ cm⁻³. It is established that the appearance of a high concentration of donor centers in the heterostructures is caused by the IBM-induced activation of neutral defects formed during epitaxial growth. The probable nature of defects is discussed.     

Nano-and microsecond laser pulse confinement in compensated gallium arsenide

Experimental data on the nano-and microsecond pulsed laser radiation (λ=1.315 μm) confinement in compensated GaAs are reported. There are three regions of confinement, which are controlled by radiation selfdefocusing due to single-photon absorption by deep impurity levels, self-defocusing due to two-photon absorption, and self-focusing caused by thermal dynamic lens formation.     

The hydrodynamics of countercurrent two-phase flow in vertical channels

Countercurrent flow of gas and liquid in vertical tubes is investigated. Processes that occur under various conditions of flow (including the “flooding” mode) are treated. Equations are suggested that describing the hydrodynamic characteristics of countercurrent two-phase flow.     

Formation of vortices during explosion welding (titanium-orthorhombic titanium aluminide)

The possibility of cladding commercially pure titanium by a plate of orthorhombic titanium aluminide has been investigated. The bimetallic joints of orthorhombic titanium aluminide (Ti-30Al-16Nb-1Zr-1Mo) with commercially pure titanium have been obtained by explosion welding. It has been found that the weld joint investigated had a multilayer structure consisting of a zone of continuous deformation observed in both materials, a zone of titanium recrystallization, and a transition zone near the interface. Wave formation and formation of isolated vortex zones have been observed. It has been found that upon explosion welding the bonding of the surfaces is effected via melting and subsequent mixing (in the zone of vortices) and the transfer of particles of one metal into another with the formation of particle tracks (outside the zone of vortices). A possible scenario of the formation of the vortex zone in the melt with a subsequent eutectic decomposition is proposed. The structure of the vortex zones was found to consist of an ultrafine mixture of α and β grains (both phases are disordered) with the grain size changing in the limits of 50–300 nm. The regions of transition from the vortex zone to the region of continuous deformation of the aluminide and to the recrystallized zone of titanium have been investigated.     

Monitoring the composition of the Cd<Subscript>1 − <Emphasis Type="Italic">z</Emphasis></Subscript>Zn<Subscript><Emphasis Type="Italic">z</Emphasis></Subscript>Te heteroepitaxial layers by spectroscopic ellipsometry

A hardware-software complex based on a spectroscopic ellipsometer integrated into a molecular beam epitaxy installation and destined to monitor the composition of the Cd_{1 − z} Zn _z Te alloy at small values of z is described. Methodical features of determination of the composition of growing layers by the spectra of ellipsometric parameters are considered. The procedure of determination of the composition by the absorption edge that allows measuring this parameter accurate to 1.2% is developed. Problems are considered the solutions of which will allow one to increase the resolution by the composition. In particular, maintaining a stable temperature during growth is required for this purpose.