Wear of high-fired periclase-spinel refractories in the roof of a double-bath steel-melting furnace

Conclusions Periclase-spinel products prepared from magnesite powders which are pure in chemical composition and beneficiated Kempirsaisk chromite possess an increased resistance (30% higher than in ordinary periclase-spinel brick) during service in the roof of a double-bath steel-melting furnace, operating with oxygen blow in the bath. Their wear in general occurs as a result of the fusion of the working surface. The mechanism of this wear is explained by the metasomatic processes which lead almost to complete replacement of the periclase and chrome-spinel by ferritic spinels.The increase in the resistance of the experimental periclase—spinel refractories is helped by the structure with the direct bond between the grains which retards the access of silicates and slags inside the textural elements. This exerts a favorable influence on the change in structure of the refractory during service, especially in the transition zone in which additional sintering and crack formation leading to scaling of the experimental refractory hardly develops.On the basis of the results of the research we recommend that refractory enterprises set up various technological production lines for making periclase-spinel products from pure Satkinsk magnesite powders (94–96% magnesium oxide) and beneficiated Kempirsaisk chromite (59–60% chromium oxide) using high-temperature firing in a tunnel klin. The use of high fired periclase-spinel products with a direct bond between the grains would increase the resistance of the roofs of metallurgical furnaces operating with the use of oxygen and increasing their outputs.Translated from Ogneupory, No. 5, pp. 28–33, May, 1973.     

Processor curve of a magnetostrictive displacement transducer

A technique is discussed for improving the accuracy of a displacement-sensing primary detector by taking into account the influence of perturbing factors on the coefficients of the so-called processor curve. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 29–30, May, 1999.     

Singular and Hypersingular Integral Equations Techniques for Gyrotron Coaxial Resonators with a Corrugated Insert

For the first time rigorous theory is developed for eigen traveling TM modes in the resonator of the coaxial cavity gyrotron with a corrugated insert. This mathematical model can be applied for any corrugation parameters and wavelengths. Gyrotron simulation software is developed and allows to calculate mode eigenvalues, electromagnetic field components and Ohmic losses for eigen TE and TM modes. Results of the numerical investigations are presented for the ITER relevant 170 GHz coaxial cavity gyrotron developed in Forschungszentrum Karlsruhe, Germany.     

On the kinetics of oriented growth of two-phase colonies of platelet grains in the presence of second-phase particles phase

Specific features of the formation of lamellar (columnar) two-phase structures have been considered in the process of the decomposition of the matrix in the presence of (1) immobile disperse second-phase particles and (2) mobile disperse second-phase inclusions. It has been shown that the approaches to the derivation of initial differential equations of growth should be based on the change in the behavior of particles of the second phase upon the potential propagation of the growth front. To retain the invariance of the driving force along the entire composite growth front of the colony-wise structure, equations of balance of interphase surface tensions in ternary junctions of the normal sections of matrix grains with lamellar grains of the two-phase colony-wise mixture have been taken into account.     

New approach to the characterization of ion-exchange membranes using a set of model parameters

An extended three-wire model of the conductivity of ion-exchange membranes is proposed. The model includes a set of three-wire model equations supplemented with coupling equations between three-wire model parameters and the parameters of a microheterogeneous model. To calculate the complete set of parameters for evaluating the structural inhomogeneity of a membrane and calculating its effective electrotransport properties, it is necessary and sufficient to get only the concentration dependence of the specific conductivity of the membrane, which simplifies the characterization procedure. The model was verified based on independent experimental data and the calculations of transport-structural parameters with the use of the microheterogeneous model. It was found that the proposed model approach makes it possible to obtain a reliable combination of structural parameters to characterize the volume fractions of conductive phases and their mutual arrangement in the ion exchange material peculiar to the membrane test sample.     

Synthesis and properties of antimony-doped ZnO nanorods

This paper describes a process for the synthesis of ZnO〈Sb〉nanorods containing controlled antimony concentrations. We have optimized the synthesis of ZnO〈Sb〉nanorods to maximize their length-to-diameter ratio. The synthesis conditions and subsequent processing are shown to have a significant effect on the luminescence and transport properties of the nanorods. Planar structures based on individual nanorods were produced by electron beam lithography and their current-voltage characteristics were measured and were shown to depend on the chemical history of the nanorods.     

Estimation of state of paper electric insulation based on results of measuring recovered voltage

Based on the multicomponent analysis of the recovery voltage curve, a new approach to assessing the condition of electrical insulation has been justified that allows one to monitor changes in the volume charge state and electric conductivity of insulation using the results of one measurement. For cables with impregnated paper insulation, this approach enables one to monitor typical defects in operation, such as drying out the impregnation compound and humidifying the insulation along the entire trajectory of its aging from unfailing up to marginal state.     

Oxidation of Powdered Alloys of Aluminum and Cerium during Heating in Air

The effect of cerium on the oxidation of powdered alloys of aluminum and cerium during heating in air at temperatures up to 1773 K was studied using derivatography, xray phase analysis, and thermal desorption of argon. It is established that the rate and completeness of the oxidation of aluminum increase if it is alloyed with cerium. The effect of cerium is due to its polyvalence, high reactivity, and surface activity toward aluminum. Structural and phase nonuniformities that arise during the growth of oxide phases on the surface of oxidized particles of the alloys enhance the interaction of these particles with air oxygen. It is shown that the assumptions that the surfaces of the alloys have a micrononuniform structure and are enriched with CeAl₂ and CeAl₄ groups are valid.     

High-Temperature Compatibility of Al–Rare Earth Alloys with Titanium Carbide

The wetting of titanium carbide by molten Al–rare earth alloys was studied. The physicochemical properties of the alloys were correlated with the contact angle and the carbon and oxygen affinities of the substrate and alloy. The properties of the alloys were investigated as a function of composition. The phase relations in the Al-rich corners of the Al–Y and Al–Nd phase diagrams were refined using viscosity data. The x-ray microanalysis and Auger electron spectroscopy data were used to assess the melt structure, adsorption behavior of the melt components at the liquid–gas and liquid–solid interfaces, interfacial area, and composition of the transition layer. The introduction of rare-earth additions into Al was found to reduce the temperature at which good adhesion to TiC can be achieved by 100–200 K.