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Izvestiya. Non-Ferrous Metallurgy

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Extractive metallurgy of nonferrous metals

Nemchinova N.V. A study of structure of reducer and its reactive capability during carbothermic production of high-pure silicon
High-pure silicon (KrS) for photoelectric current converters can be produced by the carbothermic method in electric arc furnaces followed by clarification and multicrystal growing. The quality of KrS produced is largely dependent of correct selection of primary raw materials. In melting, the requirements to reducers as to the reaction capability are imposed along with minimal ash content. This work describes the investigation of the structural dependence of “Carbosil” low-ash carbon-material reaction capability after two processing methods (for the purpose of decrease in ash): chemical and high-temperature ones. Thermogravimetry, IR spectroscopy, EPR, and express gravimetric analyses were used in the investigations. The results showed the advantage of acid processing (ash decreasing was 85,38 %) on retention of sufficient reaction capability of carbon material.

Vostrikov V.A., Vostrikova N.M. Vapor-phase oxidation of arsenic containing concentrates
For the purpose of determination of a possibility to apply the vapor-phase oxidation for processing arsenic-containing concentrates and ores, investigations were carried out for steam roasting of arsenopyrite gold-containing concentrate. The effect of temperature and duration of vapor-phase oxidation was studied on the degree of its dearsenation and desulphurization. Based on the experimental data obtained, one can conclude that the effect of superheated water vapor at T = 800 ° C and air-vapor mixture at T = 700÷800 ° C is most effective. Concentrate roasting by the air at T = 700÷800 ° C gives no intended effect since the residual arsenic content in the roasted product is high enough.

Zubtsova E.A., Vorobiyov I.B., Kirov S.S., Nikolaev I.V., Seredkin M.V. Investigation of technological properties of Guinean bauxites
The technological properties of bauxites mined in one of the Guinean deposits were investigated and the optimal properties of their leaching: T = 190 ° C, CNa2O = 230 g/dm3, t = 60 min, without lime addition were determined. The mechanisms of change of the phase composition during leaching were found by chemical and X-ray structure analyses.

Extractive metallurgy of less-common and precious metals

Naumov A.V. A review of the world market of cadmium
Based on the publications of the recent years, a review of the current state of the world and Russian markets of cadmium was made as well as the prospect for their development was considered.

Davidenko P.S., Troshkin A.M., Melnikov Yu.T. Kinetics of interaction of antimony sulfide with nitric acid solution
The kinetic mechanism of antimony (III) sulfide oxidation was investigated depending on the concentration of nitric acid, temperature, and hydrodynamic conditions. The calculated reaction order by HNO3 in a range of its concentration from 80 to 140 g/dm3 is two. Of the temperature dependences of Sb2S3 oxidation rates, the apparent activation energy for [HNO3] = 100 and 140 g/dm3 were calculated, being equal to 30,9 and 31,8 kJ/mole respectively. The effect of the hydrodynamic conditions on Sb2S3 oxidation rate was found. The character of temperature and pulp mixing intensity effect on the Sb2S3 leaching kinetic makes it possible to conclude that the oxidation process at the initial stage runs in the miscellaneous conditions and it passes gradually to intradiffusion one. This is confirmed by run-out of the kinetic curves onto the plateaus upon 30 min leaching. The initial sections of the kinetic Sb2S3 oxidation curves are caused by that evolving NO interacts with oxygen of the air in the reactor gas space, and after O2 depletion only, the view of the curve is specified by the Sb2S3 oxidation kinetic. These features disappear when carrying the process in the argon atmosphere.

Balgaeva F.Sh., Medvedev A.S. Extraction of rhenium out of roasted products from oxidizing roasting of molybdenite concentrates
The effect of different parameters on rhenium extraction from the roasted product, being obtained because of poor molybdenum concentrate roasting in the tube furnace by means of water leaching and weak nitrate water solution, was considered. Maximum Re extraction during processing of roasted product by water is ~ 60 % and that by acidified water solution is 98 %. The most significant parameters affecting Re extraction are oxidizing agent concentration and the process duration. The optimal process conditions are S : L = 1 : 4, [NHO3] = 4 %, t = 2 h, T = 45÷50 ° C. In this case, the larger part of copper passes into the solution. Its concentration in the roasted product decreases from 1,5 to 0,1 %, thus permitting to use it for ferromolybdenum smelting.

Mineev G.G., Zhuchkov I.A. Low-temperature autoclave process of breakdown of difficult-to-process gold in sulfide concentrates
The experimental investigations of autoclave-peroxide oxidation of sulfide minerals and natural concentrate have been carried out. Sulfide concentrate of ore preparation from one of the deposits of Russia was taken as an object. The concentrate is of difficult-to-process and related to fine association of gold with pyrite and arsenopyrite and that of silver with galenite. Chemical activators (catalysts) of autoclave mineral oxidation in peroxide medium were proposed: molybdenum and nitric acids within a certain relation. They are able to increase 8–10 times the degree of sulfide decomposition at temperatures below the sulfur melting temperature. Using phase X-ray structure analysis and UV spectroscopy, the mechanism of catalytic action of introducible chemical additives was established. The degree of breakdown of noble metals in the catalyzed autoclave-peroxide process and their subsequent extraction by cyanation of solid residues of autoclave concentrate processing is ~93÷94 % for gold and ~75 % for silver.

Metal forming

Bogatov A.A., Levin I.V. On mathematic modeling of forming and evolution of grain metal structure in forming operation
The article gives a statement of a coupled boundary-value problem of the mechanics of continuum movement and thermal reactions in the deformation zone as well as the methods to solve it. The principal physics of the process of its variation during deformation and recrystallization as well as the ideas of phenomenological approach to the construction of structural condition diagrams and establishment of deformation mechanisms based on studying the plastic hardening of metals were used in development of the grain structure evolution models.

Materials science and heat treatment

Samoshina M.E., Aksyonov A.A., Istomin-Kastrovsky V.V., Gostev Yu.V. Structure and properties of dispersion-hardened materials of aluminum mixed secondary raw material
An opportunity is shown to produce composite material (AK12M2 + D16)–20 % vol. SiC of the specified composition of mixed aluminum raw material by the method of mechanical alloying. The indiscrete matrix corresponding to the composition of AK5M2 alloy with uniformly distributed SiC particles < 1 m m is formed in the treatment process of such composite material. (AK12M2 + D16)–O composite material was produced by joint processing of matrix alloy chips in the air under the controlled quantity of the air supplied in the system. An oxygen buildup in the composite material granules was found during increasing the time of mechanical alloying and the air volume, providing the synthesis of strengthening oxide particles in the aluminum matrix in this case. The consolidated samples of the composite materials strengthened by ceramic particles of two types (both introduced in the charge mixture and synthesized in the production process) are of high hardness at the room and elevated temperatures and low linear thermal coefficient of expansion.

Powder materials and coatings

Lakhin A.V., Bogachev E.A., Manukhin A.V., Timofeev A.N. Gas-phase deposition of silicon carbide from methylsilane at relatively low temperatures and pressures
The silicon carbide deposition process kinetics from methylsilane (CH3SiH3) on the graphite substrates at T = 590÷680 ° C and P = 50 Pa was studied. The crystalline SiC layers produced are of predominantly cubic modification with little content of hexagonal one. The X-ray photoelectronic spectroscopy established that the coating composition is close to the stoichiometric composition (Si/C ~ 0,9) for the studied deposition temperatures and it is characterized by low impurity content.

Boiko A.V. Erosion resistance of contact materials in the silver–graphite system with anisotropic structure
The erosion resistance of silver-graphite (3–5 % wt) contact materials made by extrusion in a wide range of extension ratios (400–2500 %) was investigated. It was established that the contacts with the structure of graphite particles aligned is perpendicular to the contact surface had the highest erosion resistance and those with particles in parallel had the lowest resistance. The erosion resistance rises with increase of the extension ratio. The behavior of the contact erosion resistance depending on the contact structure is explained by variation of the heat conductivity. Based on the results of model analysis of the coefficients of heat conductivity (for T = 400¸ 960 ° C) for the silver-graphite compositions, it was found that heat conductivity of the contact with perpendicular alignment of graphite particles in the structure relatively to the working surface is much higher that those with parallel.

Panov V.S., Padalko A.G. Barothermic impact on structure and properties of VA-8 alloy
The effect of treatment of VA-8 (WC–Ni3Al) sintered in hydrogen or vacuum was investigated in a gas-static device at the temperatures of 1300, 1320, and 1340 ° C and under pressure of 150 MPa. Independent of the medium of preliminary sintering, the ultimate bending strength, fracture toughness, and hardness of this alloy rise after barothermiс exposure, being related to decrease of the number of coarse micropores and improvement in uniformity of its structure.

Structural macrokinetics. Self-propagating high-temperature synthesis

Levashov E.A., Senatulin B.R., Leyland A., Matthews A. Production of composition targets by technology of self-propagating high-temperature synthesis in Ti–B–Si–Al system
The macrokinetic characteristics of SHS-reaction were investigated in the Ti–B–Si–Al system. The charge mixture was prepared according to the reaction equation in the following manner: X(Ti + 2B) + (70 % – X)(5Ti + 3Si) + 30 % (Ti + Al) where X, % mol is the running charging parameter. The adiabatic combustion temperature of the compositions studied and the equilibrium composition of the reaction products for it were calculated. The speed of combustion wave propagation was shown to rise when X value increases. The microstructure of synthesis products and the processes of their phase and structure formation were studied. The TiAl phase content in the synthesis products was found to be much lower than the calculated one, apparently being concerned with transfer of a part of charged aluminum and titanium into the Ti5Si3 sublattice. The hardness values of the samples studied are at a level of 87–88 HRA and the relative density is 97–99 %. TiB2–Ti5Si3–TiAl–Ti2AlN composition targets of different sizes intended for magnetron deposition of nanostructural multifunctional coatings were produced by the process of power SHS-compaction.

Surface engineering. Multifunctional films. Corrosion and metal protection

Pustov Yu.A., Filonov M.R., Pechyorkin K.A., Anosova M.O., Olesova V.N., Posdeev I.A. Electrochemical diagnosis of metal and alloy compatibility, which are used in stomatological prosthesis
The present-day practice of stomatologic orthopedics and prosthetics is rested on a wide application of different metals and alloys. However the application of dissimilar metallic and metal-ceramic materials in the mouth cavity can result in origination of their electrochemical inconsistency, so-called galvanism (galvanos) accompanying by sense of discomfort and sometimes by severe pain, metallic off-flavor, etc, which are conditioned by galvanic couples being originated. Corrosion damage of one of the structures of the contacting pair takes place in this case. The present work gives the results of investigation of electric properties of separate metals and alloys as well as contacting pairs on their basis, which work in the stationary conditions or under the conditions of mechanical effect on the surface of one of the elements of the pair. The investigations were carried out for the purpose of determination of the most promising dental materials and their combinations characterizing by the least effect of galvanism. NiTi alloy was used as a basic element of the contacting pair and one of nine materials studied was the second element. The electrochemical studies in the stomatology were shown to be the effective method of diagnosis of the state and estimate of corrosion rate of structure elements manufactured of metal materials of different nature. This permits to range them in terms of possibility of joint usage in prosthetics, being one of the most important stage of development and application of new materials in the stomatolgy.

Chronicle

Vladimir Sergeevich Panov is 70 years old

No 1 (2006)


ISSN 0021-3438 (Print)
ISSN 2412-8783 (Online)