Vol 58, No 1 (2017)

In the present work, the leaching kinetics of covellite ore in ammonia solution was studied and the following variables, the solution concentration, reaction temperature and particle size were considered. A kinetics model representing the effects of these variables on the leaching rate was developed and it was ascertained that the leaching rate increases with increasing solution concentration, reaction temperature and decreasing particle size. At optimal conditions, 75.1% of covellite ore was reacted within 120 min and the leaching reaction was diffusion controlled by surface chemical mechanism. The calculated activation energy of 56.98 kJ/mol supported the proposed dissolution process.

Synergistic effect of FeS and ZnS content on the separation of lead and antimony for PbS–Sb₂S₃–ZnS–FeS quaternary system under water vapor atmosphere has been studed in this paper. The results indicate that FeS can and ZnS can inhibit the volatilization of PbS. Inhibition effect of FeS is superior to that of ZnS to the volatilization of PbS. As to Sb₂S₃, FeS can inhibite the volatilization of Sb₂S₃, but ZnS can promote the volatilization of Sb₂S₃. Inhibition effect of FeS is superior to that of ZnS to the volatilization of Sb₂S₃.

The objective of the present work is to investigate the extraction of copper from spent low temperature Shift catalyst using EDTA, as chelating agent and optimization of the parameters that influence the extraction of copper. Response surface methodology was applied for designing the experiment and to determine the optimal experimental conditions. Most influencing parameters such as concentration of EDTA, solid to liquid ratio and particle size of catalyst were optimized based on 3 factors 3 levels box behnken design which requires 15 run of experiments for designing a response surface. The high value of regression coefficient R² (0.981) indicates a good correlation between predicted and experimental response, which confirms the acceptability of the proposed model.The optimum conditions were found as—concentration of EDTA: 0.5889 M, solid to liquid ratio: 0.02 and particle size: 90 μm. Under these optimum conditions, the experimental value of extraction of copper was estimated as 94.5% which seems very close to predicted response.

The results of investigations into the synthesis kinetics of magnesium hydrocarboaluminates are presented and the key role of the preliminary temperature activation of the magnesium component of the feedstock and temperature in the process rate is determined. The mechanism and conditions of the cocrystallization of calcium and magnesium hydrocarboaluminates from preliminarily activated natural Mg-containing feedstock are investigated. A high reaction ability of hexagonal structures of synthesized substances is established. An apparatus-and-process flowsheet of the synthesis process of hydrocarboaluminates of alkali earth metals in conditions of alumina production is proposed.

A fluoride cycle in tungsten technology is based on three processes: (i) electrochemical decomposition of HF in the KHF₂ + HF melt at 80–100°C with the separate evolution of gaseous fluorine and hydrogen; (ii) fluorination of the tungsten powder with evoluated fluorine at 300–350°C with the condensation of formed WF₆ in a liquid form at t = 2.5–3.0°C, and (iii) reduction of gaseous WF₆ with evoluated hydrogen at t = 580–600°C with the condensation of formed HF at +1°C and its use for the fluorine and hydrogen production, thereby ensuring their recycling in the cycle. The optimization of mentioned processes resulted in hardware-process implementations providing the formation of a large-scale plane and cylindrical billets in the industrial scale for deformation, as well as pipes, crucibles, and other products of various sizes made of tungsten with productivity of one process line of ~4.3 kg/h (>34 t/yr) with the fulfillment of environmental requirements. In contrast with the methods of powder metallurgy, the described technology ensures the formation of dense half-finished products and products made of pure tungsten with finer grain structures and almost unlimited sizes. Herewith, the specific power consumption for 1 kg of production lowers by a factor of 2.0–2.5. To increase the production efficiency, the simultaneous operation of four process lines in an automated mode is recommended.

The questions of applying the organoaluminum and yttrium aluminum binders when fabricating high-thermostable ceramic corundum molds are considered. This technology is a promising direction in the formation of ceramic shell molds for intricately shaped high-duty investment castings made of titanium alloys. The use of silica-free binders, which possess a series of advantages when compared with many currently widespread ones, in casting houses makes it possible to solve many questions associated with the thermochemical stability of ceramic forms, as well as to decrease the volume of finish operations and rejects during casting parts made of chemically active metals and alloys, thereby providing an increase in the quality of exact important castings.

Technical and process features of a flowsheet for fabricating the wire of casting aluminum alloys intended to solder waveguides with the use of the combined continuous casting–pressing of nonferrous metals are considered. The dependences necessary and sufficient to design the constructive elements of equipment and process modes providing the implementation of conditions for the stable run of processes of continuous supply of the metal melt into the stream of the carousel molding laboratory machine, its solidification, and extrusion into the die opening similarly to Conform technology are established. The magnitude of the cross section of the hole in the supply dispenser of the metal melt into the stream of the crystallizer wheel is calculated. The process modes of the continuous casting–pressing using a laboratory installation of a billet 3 mm in diameter and its subsequent treatment by high-quality rolling and drawing in combination with intermediate annealing procedures to the final sizes are presented. According to this flowsheet, a pilot batch of round and square wire of alloys AK12Ts10 and AK12Ts15 has been produced in the amount of 3 kg and delivered to the AO ISS enterprise for industrial test soldering of waveguides.

A relatively small number of revolutionary materials have been discovered in the field of physical metallurgy and metal physics in the last several decades, and bulk metallic glasses are among them. Their strength and hardness are considerably higher and their modulus of normal elasticity is considerably lower than that of crystalline alloys, which leads to large stored elastic strain energy. These materials also have very good corrosion resistance. In this article, we present the properties of bulk metallic glasses, in particular, thermal, mechanical, magnetic, and electrical properties, corrosion resistance, as well as the application fields of these alloys.