Effect of zirconium and molybdenum oxides on the viscosity and the electrical conductivity of oxide-fluoride slags

The effect of additions of zirconium and molybdenum oxides on the viscosity and the electrical conductivity of oxide-fluoride slags is studied using a vibration viscometry and an ac bridge.     

Effect of titanium and molybdenum oxides on viscosity and electrical conductivity of oxide-fluoride slags

The effect of additives of titanium and molybdenum oxides on the viscosity and electrical conductivity of the Al₂O₃-CaO-CaF₂ oxide-fluoride slag melts at 1750–1950 K is investigated by vibration viscosimetry and the ac bridge method. Crystallization intervals are established depending on the variation in the TiO₂ and MoO₃ concentrations in the melts from 0 to 25%, and it is revealed that the majority charge carriers are calcium and fluorine ions. These data indicate the complex-forming character of the behavior of Ti and Mo in aluminum-calcium oxide-fluoride melts.     

Effect of nickel and cobalt on interphase interaction in pseudoalloys tungsten (molybdenum)-silver

Conclusions Interaction of tungsten and molybdenum with additions of nickel or cobalt under temperature-time conditions corresponding to the formation of molybdenum-silver and tungsten-silver pseudoalloys leads to the formation of solid solutions and (or) intermetallic compounds on the interface between the high-melting matrix and the silver. By varying the conditions of formation of the pseudoalloy on this interface we can obtain different phases and deliberately change mechanical properties of this part and of the pseudoalloy as a whole.Translated from Poroshkovaya Metallurgiya, No. 2(278), pp. 59–62, February, 1986.     

Liquid extraction of rhenium(VII) and molybdenum(VI) with trialkylphosphine oxide from acidic solutions

The liquid extraction of rhenium(VII) and molybdenum(VI) ions from sulfuric, hydrochloric, and nitric acid media is studied in the temperature range from 20 to 40°C using trialkylphosphine oxide in kerosene as an extracting agent. The maximum separation of these metals is attained when they are extracted from solutions of 1.0–2.0 M H₂SO₄ (the duration of intense phase mixing was 3–5 min). The enthalpy of the studied process is estimated to be ΔH = ?32.32 kJ/mol for molybdenum and ?51.52 kJ/mol for rhenium. The chemical aspects of the extraction process studied are discussed.     

Extraction of tungsten(VI) from hydrochloric and nitric acid solutions by tri-isooctylamine in various organic diluents

The dependence of the distribution ratio of tungsten(VI) upon aqueous acid concentration in hydrochloric and nitric acid media using hydrochloride and nitrate salts of triisooctylamine (TIOA or R,N) in various organic diluents including benzene, chloroform and 1,2-dichloroethane has been studied. The influence of the aqueous tungsten concentration upon the extraction was also determined. The degree of extraction varies with hydrogen ion concentration. No definite formula can be ascribed to the organic species formed. An overall equation for the mechanism of extraction is tentatively proposed.A new colorimetric technique for the determination of small amounts of tungsten(VI) is reported.     

An increase in purity of ammonium perrhenate solutions with respect to molybdenum(IV) with the sorption recovery of rhenium(VII) from Mo-containing solutions

The possibility of the additional purification of ammonia rhenium desorbates with respect to molybdenum in the course of the sorption recovery of rhenium from Mo-containing solutions with the help of Purolite A170 and Purolite A172 weak base anion-exchange resins is considered. The pH-dependence of sorption of Re(VII) and Mo(VI) on these anion-exchange resins is investigated in static conditions with the 1 M (NH₄)₂SO₄ background in the solution. It is shown that the range of pH, in which anion-exchange resins retain the ability to sorb Re(VII), is also spread to a weakly basic region. A substantial decrease in the adsorption of Re(VII) starts already with an increase in pH above 7.5. The capacity of anion-exchange resins with respect to Mo(VI) starts to decrease noticeably with an increase in pH of solutions above 5.0, and molybdenum almost ceases to sorb by both anion-exchange resins upon reaching pH ~ 7.0. In order to decrease the Mo(VI) content in rhenium desorbates with the sorption recovery of Re(VII) from Mo-containing solutions on weak base anion-exchange resins, the following flowsheet is suggested. Initially, the main amount of sorbed Mo(VI) is desorbed by contacting the saturated anion-exchange resin with the ammonium sulfate solution upon mixture stirring and holding constant pH of the solution in limits of 7.0–7.5 due to the addition of dosed amounts of ammonia solution. Then anion-exchange resin is separated from the ammonium sulfate solution containing Mo(VI), washed with water, and Re(VII) is desorbed by ammonium solution in dynamic conditions. The verification of the proposed method for the resins saturated by sorption from the model solution of the composition, g/L, 98 H₂SO₄, 4 Mo(VI), and 0.5 Re(VII) showed the occurrence of desorption of no less than 90% sorbed molybdenum during the treatment of anion-exchange resins with ammonium sulfate solution. Herewith, concentration ratio Re(VII) : Mo(VI) in ammoniacal rhenium desorbates when using A170 anion-exchange resin increases 11-fold and when using A172 anion-exchange resin, it increases 20-fold compared with that attained without the additional washing of Mo(VI). Losses of Re(VII) with the Mo-containing desorbate (reversible) do not exceed 5.2% of the amount of sorbed Re(VII).     

应用于仲钨酸铵结晶过程中钨钼分离的高效方法

通过对大量仲钨酸铵(Ammonium Paratungstate,APT)结晶生产数据的总结,发现结晶料液(钨酸铵溶液)中氯离子浓度与APT晶体的钼含量之间存在明显的负相关关系,即氯离子具有在APT结晶过程中抑制Mo析出的作用。进一步研究还发现,对于特定组成的结晶料液,存在一对应的氯离子浓度阈值,在此阈值氯离子对料液中Mo析出的抑制作用达到最强。在此基础上,提出一种通过控制结晶料液氯离子浓度来实现APT结晶过程钨钼分离的高效、新型方法。通过这种方法,不但能够将APT的一次结晶率从原来的80%提高到96%,而且制得的APT产品具有晶体结构好,粒度均匀,纯度高(Mo含量不大于2×10-5)的优点。同时,对氯离子抑制钼析出的机理进行了探讨。     

Reactions at phase boundaries in pseudoalloys based on tungsten (molybdenum) and copper

Conclusions The reaction between tungsten and copper in the presence of nickel under conditions close to those of pseudoalloy formation is characterized by the formation of a two-layer zone in the copper. Next to the tungsten there is a layer of a phase containing W, Ni, and Cu. The reaction between molybdenum and copper under the same conditions is not accompanied by the formation of a new phase. It is possible to activate the reactions at the phase boundaries of such a pseudoalloy without increasing its electrical resistivity by decreasing the amount of nickel added to it and ensuring that the addition is evenly distributed over the surface of the particle of the pseudoalloy's refractory component. The addition of cobalt to a molybdenum-copper pseudoalloy leads to the appearance of layers of a Mo₆Co₇-base phase at its phase boundaries.Translated from Poroshkovaya Metallurgiya, No. 12(216), pp. 39–44, December, 1980.     

Electrochemical synthesis of intermetallic compounds and complex carbides based on molybdenum (tungsten) and cobalt (nickel)

Systems for the joint electrodeposition of molybdenum (tungsten) and nickel(cobalt) from ionic melts have been identified. Conditions for depositing the intermetallics molybdenum(tungsten)-nickel(cobalt) and double carbides based on these were ascertained. It is shown that the process of electrochemical synthesis is determined, on the whole, by the ratio of partial currents of reacting components, energies of interaction between them, and the occurrence of parallel reactions between components.Institute of General and Inorganic Chemistry, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 3/4(384), pp. 1–6, March–April. 1996. Original article submitted June 20, 1994.     

Ways of increasing the plasticity of molybdenum,tungsten, and alloys based on them (review)

A combined treatment method is devised for raising the plasticity of refractory metals on the basis of a study of relevant papers.Ternopol Pedagogic Institute. Translated from Poroshkovaya Metallurgiya, Nos. 5–6, pp. 107–111, May-June, 1996. Original article submitted March 28, 1994.     

Effect of niobium,molybdenum, and tungsten on some properties of iron-boride materials

Conclusions A study was made of some key physicomechanical properties of iron-boride materials alloyed with Nb, Mo, and W. The greatest strengthening effect (_t = 62–75 kgf/mm² at 30–33 HRC) is achieved with iron-tungsten matrices infiltrated, using alloyed powders produced by coreduction from oxides, with eutectic Fe-Mo-B or Fe-Nb-Mo-B alloys. The presence of Fe(Nb, Mo)_xB_y type borides in the eutectic alloys substantially increases the heat resistance of the infiltrated materials.Translated from Poroshkovaya Metallurgiya, No. 2(206), pp. 79–82, February, 1980.     

Effect of niobium-containing additions on the viscosity and electrical conductivity of oxide-fluoride melts

An oscillatory viscometer and ac 5-kHz bridge are used to measure the viscosity and electrical conductivity (at 1450–1600°C) of two types of slag melts based on CaF₂(ANF-1P flux) and on the CaF₂-30% Al₂O₃ system (ANF-6 flux) with additions (to 35%) of one of the following three types of niobium-containing compounds: Nb₂O₅ (extrapure grade), Nb₂O₅ (commercial purity), and a niobium concentrate (about 70% Nb₂O₅). An addition of the niobium-containing compounds to the fluxes is found to increase the viscosity, to increase the solidification range, and to decrease the electrical conductivities of the melts. In this case, the activation energies of viscous flow (34–148 kJ/mol) and conduction (22–100 kJ/mol) increase monotonically, which indicates polymerization of the melts.