Use of various growth catalysts for laser sputtering of ZnO micro- and nanorods

Pulsed laser deposition and various catalysts are used to fabricate ZnO micro- and nanorods at temperatures close to the optimum temperature for each catalyst. A comparative analysis of the optical and structural properties of the rods shows that, as the temperature of growth on Al₂O₃(11–20) substrates decreases, the internal stresses in the rods decrease, which improves their structure and optical properties. This effect is not observed for GaN/Si substrates because of the high stresses induced by the difference in the lattice parameters. An increase in the synthesis temperature leads to an increase in the lattice strains and the concentration of point defects, the relaxation of selection rules, and the appearance of numerous phonon A ₁(LO) overtones. The lattice strains calculated from unit cell parameter a and the shift in the phonon A ₁(LO) frequency agree qualitatively. The study of the photoluminescence of the rods shows that a decrease in the synthesis temperature decreases the imperfection of the ZnO rods and improves their optical properties for UV applications.     

Fe2O3-Li2O Catalysts for Ammonia Oxidation

The catalytic properties of the Fe₂O₃-Li₂O system in ammonia oxidation were studied in the high-temperature region. The influence of the phase composition of the system on the physicochemical, catalyticproperties of the catalysts were revealed. The catalytic properties of lithium ferrite, which is the most activeand selective component of the Fe₂O₃-Li₂O system, were studied. The mechanism of lithium ferrite deactivation at 1273 K is considered.     

The Singular Limit Problem to the Extended Cahn–Hillard Equation

A mathematical model with a small parameter, which describes the hardening process of the binary tin–lead alloy, is investigated on the basis of nonlinear asymptotic analysis. A singular limit problem, namely an extended Stefan problem in the case of short relaxation time in the phase transformation zone, is derived. We prove the existence of an asymptotic solution with any accuracy on the time interval where the solution to the singular limit problem exists. The phase-separation interface is determined uniquely by three leading approximations. We also show that the stability of the separation interface depends on the so-called dissipation condition obtained for the solutions of the interface problem. Nonsymmetry of the surface tension tensor leads to a situation where the limit values of concentration distributions are in dependence on the geometry of the interface. This provokes the dispersion of the interface problem solutions on the part of the interface that not is tangent to the main crystallographic axis.     

Trapping of Transformation Products of a Palladium Catalyst for Ammonia Oxidation by a Calcium Oxide Absorbent

The chemical regularities of trapping palladium and its compounds lost in the process of high-temperature ammonia oxidation by a calcium oxide absorbent are studied. In the interaction with the absorbent, the products of palladium catalyst transformation form CaPd₃O₄, which is a derivative of the nonstoichiometric intercalation compound Ca _x Pd₃O₄, where 0 x 1. Physicochemical properties of this compound and the conditions of its formation are considered.     

Effect of a bias field on the dielectric properties of NaNbO3 solid solutions in the range of the giant temperature hysteresis of a phase transition

The effect of a bias field E on the value and temperature dependence of permittivity ɛ of ceramic samples of solid solutions 0.6NaNbO₃-0.4 NaTaO₃ (I), and 0.97[0.9NaNbO₃-0.1Na_0.5Bi_0.5TiO₃]-0.03LiNbO₃ (II) possessing an anomalously large temperature hysteresis of ɛ(T) dependence is studied. The character of the dependences of both the height and the temperature of the ɛ(T) maximum on the field show that composition (I) has antiferroelectric properties, while composition (II) has ferroelectric properties. It is found that up to 8 kV/cm, the strength of the bias field has actually no effect on the width of the ɛ(T) temperature hysteresis of the compositions under study.     

Kinetics of alkaline hydrolysis of ethylp-nitrophenyl ethylphosphonate in the reverse micellar system: sodium dodecyl sulfate-hexanol-water

The kinetics of alkaline hydrolysis of ethylp-nitrophenyl ethylphosphonate in the reverse micellar system sodium dodecyl sulfate—hexanol—water was studied. At high pH and low water content, the process occurs at the surface layer and can satisfactorily be described by the pseudo-phase model equation. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp 262–266, February, 2000.     

Recovery with Calcium Oxide Sorbent of Conversion Products of Rhodium Catalyst for Ammonia Oxidation

The chemical aspects of recovery with a calcium oxide sorbent of rhodium lost in high-temperature oxidation of ammonia were studied. The physicochemical properties of this compound, conditions of its formation were considered.     

Flowfield geometry for interaction of a side jet with a supersonic flow

The interaction of a two-dimensional lateral gas jet — a liquid wing — with a supersonic flow is analyzed, and a system of dimensionless determining parameters derived. An experimental investigation was made of the influence of these parameters on the penetration depth of the jet in the considered case of blowing through a longitudinal slot on a cylindrical surface. Simple correlation dependences of the coordinates of the characteristics points of the jet geometry on the determining parameters are proposed, and these make it possible to generalize the obtained experimental data.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 157–162, March–April, 1980.