Engineering in Action

Improvements in operational performance of the refractory lining of a direct-current electric furnace for cobalt smelting achieved at the Ufaleinikel Joint-Stock Co. in collaboration with the Kombinat Magnezit Joint-Stock Co. are reported.     

Fluorine sorption by aluminosilicate-modified diatomite from highly concentrated fluorine solutions: 1. Adsorption equilibrium

The adsorption capacity of natural (D1) and chemically structure-modified diatomite (DMA) in the removal of fluorine ions from highly concentrated fluorine solutions (up to 0.3 mol/L) under static conditions at room temperature is studied. The effect of different parameters—solution pH, initial fluorine concentration, sorbent weight, and particle surface charge density—is examined to determine the adsorption properties of DMA under different process conditions. It is shown that the solution pH plays a crucial role in the removal of fluorine from solutions. An efficient removal of fluorine occurs at a pH of 4.5–5.5. Under equilibrium conditions, upon the saturation of the DMA surface with fluorine ions, the adsorption capacity of DMA achieves 58 mmol/g of sorbent; this value is 5.5 times higher than that of unmodified D1. Fluorine adsorption isotherms for DMA samples are derived; equilibrium adsorption data are modeled using a twostage Langmuir model; it is shown that the experimental and calculated data on fluorine adsorption are in good agreement: correlation coefficient R² for the D1 and DMA samples is 0.9952 and 0.9687, respectively. The fluorine adsorption mechanism is studied. X-ray diffraction and chemical analyses, FTIR spectroscopy, potentiometric titration, and adsorption–desorption experiments reveal that the diatomite–NaF–H₂O system is characterized by the occurrence not only of physical adsorption and ion exchange but also of the chemical bonding of the fluorine ions with the active sites of the sorbent surface, i.e., the formation of weakly soluble fluorine compounds with Al on DMA and with Ca on D1 (AlF₃, Na₃AlF₆, СаF₂).     

Surface electromagnetic waves in a metal

Microwave surface electromagnetic waves are observed on a plane metal/dielectric interface in a frequency range of 0.5–20 GHz. The problem of separation of surface and spatial waves simultaneously excited by a source located on the medium interface is solved.     

Dependence of viscoelastic properties on segregation degree of components in interpenetrating polymer networks

The temperature dependences of elastic moduli, loss moduli, and mechanical loss angle tangent were investigated for the interpenetrating polymer networks: polyurethane–polyurethane acrylate by the method of dynamic mechanical spectroscopy (DMS). The segregation degree of components due to phase separation have been calculated from the parameters of relaxation maxima. An essential change was found in the segregation degree of components with the curing sequence of individual networks being changed. It was shown that, with the conditions and sequence of IPN formation changed, the phase separation degree can be fixed at a particular stage, i.e., the structures with a different segregation degree of components are obtainable. For the IPNs under investigation the variation of elastic moduli of the composites proved possible by fixing the separation degree of components.     

Chaotic dynamics in Bonhoffer-van der Pol fractional reaction-diffusion system

In this article we analyze the linear stability of nonlinear fractional reaction-diffusion systems. As an example, the reaction-diffusion model with cubic nonlinearity is considered. By computer simulation, it was shown that in such simplest system, a complex nonlinear dynamics, which includes spatially non-homogeneous oscillations and spatio-temporal chaos, takes place. Possible applications of the fractional reaction-diffusion system for signal processing and pattern recognition systems are presented.     

Physicochemical and adsorption-structural properties of diatomite modified with aluminum compounds

A selective sorbent based on the diatomite of local origin modified with aluminum compounds has been studied by the methods of powder X-ray diffraction; FTIR; and differential thermal, adsorption-structural (BET), and chemical analyses. The surface modification of diatomite is carried out by heating it in an NaOH solution and its subsequent treatment with a solution of aluminum salt and ammonia. The amorphous surface silica partially dissolves during the treatment with NaOH and forms an aluminosilicate compound at the addition of an aluminum salt. The obtained material is deposited both on the surface of the diatomite and on the inner surface of the macro- and larger mesopores, which leads to the development of the specific surface area of 81.8 m²/g, which is 2.5 times larger than the corresponding value in the initial diatomite (37.5 m²/g). The precipitated aluminosilicate compound with the concentration equal to 0.34 g of Al/g of aluminosilicate contributes to the development of a porous structure in the treated diatomite, so the volume of the mesopores increases from 0.029 to 0.079 cm³/g and that of the micropores from 0.012 to 0.027 cm³/g. The qualitative changes in the composition of the obtained sorbent are confirmed by the emergence of new lines in the X-ray diffraction patterns, which are characteristic for aluminosilicates, and additional peaks in the infrared spectra corresponding to the stretching vibrations of Si-O-Al. The selectivity of the obtained adsorbent with respect to fluoride ions increases significantly, specifically, its adsorption capacity increases from 8.9 to 57.6 mg of F/g at the initial fluorine concentration equal to 0.15 mol/L.     

Periclase-Carbon Refractories from the Kombinat Magnezit JSC for Use in Converter Steelmaking Technology at the Magnitogorskii Metal-and-Steel Works JSC

Cooperation between the Kombinat Magnezit Joint-Stock Co. and Magnitogorskii Metal-and-Steel Works Joint-Stock Co. in the area of exploitation of converter refractories is briefly outlined. Prospects for further improvement of the performance characteristics of refractories and converter design are discussed.     

Effect of pulsed magnetic field on the thermal decomposition of zirconium hydroxide

An applied magnetic field was found to raise the rate and reduce the temperature of the dehydration, dehydroxylation, and crystallization of zirconium hydroxide. The role of water in the crystallization and aggregation of zirconium hydroxide was examined.     

The influence of treatment with weak magnetic field pulses on the brittle-plastic transition temperature in zinc

It is shown that the brittle-plastic transition temperature in zinc is reduced appreciably (in terms of internal friction and microhardness) as a result of magnetic treatment. Pis’ma Zh. Tekh. Fiz. 23, 28–31 (February 12, 1997)     

Use of hybrid vibrations for measuring the amount of liquid in tanks with mobile displacers

The possibility is considered of using the resonance properties of metal chambers for measuring their volume and the amount of liquid contained in them. Basic calculation relationships are obtained for a system of coupled chamber resonators. An algorithm and functional scheme are proposed for processing resonance frequencies with measurement of the amount of liquid in long tanks. Results are presented for experimental studies. __________ Translated from Izmeritel’naya Tekhnika, No. 1, pp. 33–37, January, 2008.