Structure evolution of corundum concretes

Conclusions Structure evolution of the corundum concretes based on the binders of different compositions was studied.We demonstrated the effect of Cr₂O₃, CCLS, and technological (technical-grade) lignosulfonate on the strength gain of the cement stone and the concrete based on it, the phase composition of the cement stone and the concrete, their variation during the process of heat treatment, and on the microstructure.The ability of these additives to increase the degree of hydration of the high-alumina cement was established. The formation of a large quantity of aluminum hydroxide and calcium hydromonocarboaluminate confirm this fact.The evolution of a dense and strong structure of the corundum concrete based on the high-alumina cement and the occurrence of additional growth during the high-temperature firing process due to the formation of CA₆ and the solid solutions of corundum and CA₆ with Cr₂O₃ were shown.Translated from Ogneupory, No. 4, pp. 7–14, April, 1989.     

Effect of temperature on the interaction of ÉP823 steel with lead melts saturated with oxygen

We study the corrosion behavior of ferritic-martensitic éP823 steel in a static lead melt, saturated with oxygen, at 550 and 650°C. At these temperatures, a complex magnetite-base scale is formed on the surface of steel, but the mechanisms of its growth are different. At 550°C, corrosion has a cyclic character. On the surface of steel, a Fe_1+x Pb_2−x O₄−Fe_1+x Cr_2−x O₄ two-layer scale is formed periodically. Reaching the critical thickness (18 μm), it exfoliates along the interface with the matrix, to which oxygen-containing lead penetrates, whereupon this process is repeated. The corrosion rate is ∼0.08 mm/year. At 650°C, the intensification of reactions of formation of chromium spinel and plumboferrite induces the growth of a porous scale, where lead is accumulated. This scale has good adherence to the matrix and is formed as a compact conglomerate owing to the efficient mass transfer at all interfaces, which leads to a catastrophic rate of thinning of the specimen (3.82 mm/yr) in a lead melt. On the basis of experimental data, we propose schemes of the oxidation of chromium steels in a lead melt with a high oxygen activity at different temperatures. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 2, pp. 77–84, March–April, 2007.     

The influence of current density on the electrochemical properties of anion-exchange membranes in electrodialysis of phenylalanine solution

Electrochemical properties of heterogeneous anion-exchange membranes can be indicators of their fouling during electrodialysis of phenylalanine solutions. The current–voltage curves of the membrane MA-40 make it possible to reveal the difference in the limiting current values for fresh and fouled membranes. Increase of membrane voltage with time characterizes the development of fouling in the electromembrane system. Membrane conductivity decreases significantly in solutions containing phenylalanine. Overlimiting current conditions lead to “washing out” of amino acid from membrane phase and therefore help to avoid fouling.     

Transmission and reflection spectra of defective magnetophotonic crystals

Features of the behavior of electromagnetic eigenmodes in a transversely magnetized magneticdielectric periodic structure with a finite number of periods are analyzed. Possible defects of this structure are classified. It is shown that the presence of a defect in a layered periodic structure causes the appearance of a narrow passband corresponding to the mode associated with the defect (defect mode) in the stopband of the nondefective structure. The capability of control of the position and shape of the spectral line of the defect mode by changing the type and position of the defect and the number of the structure periods is discovered. An increased magnetooptical activity of the defective structure as compared to the magnetooptical activity of the nondefective structure is revealed.