Investigation of the forms of occurrence of nonferrous metals in oxyhydroxides from the process of nitration of chloride solutions

Using the methods of X-ray photoelectron spectroscopy (XPES), X-ray phase analysis, gamma-resonance (Mössbauer) spectroscopy, thermogravimetry of solid samples and atomic absorption, and atomic emission spectroscopy for solutions, the forms of occurrence of nonferrous metals in oxyhydroxide sediments (nitration hydroxides, NH) from nitration of refining of rhodium, iridium, and ruthenium are investigated. According to the XPES data, nitration hydroxides involve oxidized and unoxidized (selenium) transition metals, namely, Fe(III), Sn(II), Te(IV), Cu(I), Cu(II), Ni(II), Pb(II), As(III), Se(0), and Se(IV), as well as nonmetals O, Cl, and C. All nitration hydroxides are formed mainly by an X-ray amorphous phase (>90%). During heating of nitration hydroxides up to t = 900°C in an inert atmosphere, dehydration of hydroxides and crystallization of certain phases take place, but the X-ray amorphous phase amounts to more than 50%. Purely oxide phases or mixed oxide phases Fe₃O₄, SnO₂, Cu^IFe^IIIO₂, and Pb₂O₃ (NH-1); Ni_0.4Fe_2.6O₄, Cu^IFe^IIIO₂, and CuNiSnO₄ (NH-2); and Fe₃O₄, Fe₂O₃, and SnO₂ (NH-3) are formed in this case.     

A comparison of toughness of

The low-temperature toughness of C-Mn weld steel with different grain sizes was investigated with notched and precracked specimens. The results indicated that the fine grain steel, evaluated by notched specimens (Charpy V-notch and 4 point bending specimens), is tougher than that of the coarse grain steel over a temperature range from -196 °C to -30 °C. On the other hand, the coarse grain steel, evaluated with precracked specimens, has a remarkably greater plane strain fracture toughness compared to the fine grain steel. The microstructural analysis revealed that the fracture toughness of both the fine grain and the coarse grain steel is not directly related to the distance of the fracture initiation site from the precrack tip or the size of the ferrite grain. The behavioral discrepancy can be explained in terms of the ratio of local fracture stress to yield stress,i.e., σ _f f/σ _y . The fine grain steel had a higherσ _f /σ _y in the notched specimens but a lower value in the precracked specimens compared to the coarse grain steel. The scatter of toughness data can be mainly attributed to the probabilistic distribution of the weakest particle. We suggested thatσ _f /σ _y may be a useful parameter for the engineering evaluation of toughness.     

Production of high-strength tubes made of steels of type 15GFB

A unit for making L-class high-strength pump-compressor tubing composed of low-carbon, low-alloy steels of type 15GFB is now being used on the 140 mill in the tube-rolling shop at the Rustavi Metallurgical Plant. The steel 15GFB pump-compressor tubing made by the technology that was developed has the following service properties: σ_y = 630–670 N/mm², σ_u = 730–780 N/mm², δ = 18–22%, ψ = 55–60%, KCU = 1.6–2.2 MJ/m². The percentage of ductile fracture at room temperature is 85–95%. __________ Translated from Metallurg, No. 1, pp. 79–80, January, 2006.     

Mathematical model of the movement of layers of metal during the rotary rolling of semifinished products made of hypereutectic silumins

A mathematical model has been constructed to describe the kinematics of the movement of metal on the surface of semifinished products made of hypereutectic silumin alloys as they undergo rotary rolling. The model is based on the dependence of the pitch of the helical lines of metal flow on the deformation ε of the product and the feed angle α. The pitch is minimal when ε = 50–55%, regardless of the feed angle α. The degree of deformation ε = 50–55% is optimum for ensuring that the unit number of cycles in which the semifinished product is loaded by the work rolls is such as to produce a fine-grained structure and maximize the ductility characteristics of hypereutectic silumins. __________ Translated from Metallurg, No. 6, pp. 57–59, June, 2006.     

Screening of bacterial cells for biosorption of oxyanions: Application of micro-PIXE for measurement of biosorption

An attempt was made to isolate bacterial strains capable of biologically removing tungstate (WO₄²⁻) and perrhenate (ReO₄⁻). Thirty-eight water samples were collected from various areas of Anzali lagoon, Iran. Initial screening of a total of 100 bacterial isolates, resulted in the selection of one isolate with maximum biosorption capacity of WO₄²⁻ and ReO₄⁻. It was tentatively identified as Bacillus sp. according to morphological and biochemical properties and named strain GT-83. WO₄²⁻ and ReO₄⁻ uptake by Bacillus sp. GT-83 involved both inactive and active phenomena. The amount of WO₄²⁻ (initial concentration 184 mg/l) removed from aqueous solution after 16 h by inactive and active phenomena was 26 and 194.5 μg/mg protein, respectively. The strain also removed ReO₄⁻ inactively (23 μg/mg protein). Bacillus sp. GT-83 tolerated high MIC of the oxyanions. The order of toxicity of the oxyanions to the bacterium was WO₄²⁻ > ReO₄⁻ in solid media. The effects of increasing metal concentrations on the growth rate were determined in order to obtain precise patterns of resistance in liquid cultures. From the results of the oxyanions toxicity, inhibitory concentrations in solid media were higher than those in liquid media. Oxyanions biosorption was determined during the course of growth. Bacillus sp. GT-83 was capable of removing WO₄²⁻ and ReO₄⁻ during the active growth cycle with a sorption capacity of 194.5 μg WO₄²⁻/mg protein and 137.1 μg ReO₄⁻/mg protein. In view of the results of oxyanions accumulation experiments, it was concluded that Bacillus sp. GT-83 was not only tolerant to oxyanions, but it also bound considerable amounts of WO₄²⁻ and ReO₄⁻ from the growth medium. The binding of tungsten and rhenium on the cell wall of Bacillus sp. GT-83 was confirmed with micro-PIXE.     

Investigation of the formation of precipitates of copper cations with sulfhydryl collectors

The formation processes of precipitates of copper cations with diethyldithiocarbamate, xanthates (ethyl and buthyl), and isobutyl dithiophosphate are investigated using potentiometric and optical methods. The minimal value of the potential of the copper electrode (E _Cu) with the formation of precipitates agrees well with the solubility product (SP) and forms the following series: copper diethyldithiocarbamate (E _Cu = −335 mV, SP = 2.8 × 10⁻³⁰) > butyl xanthate (E _Cu = −225 mV, SP ≈ 10⁻²⁶) > ethyl xanthate (E _Cu = −163 mV, SP = 4 × 10⁻²⁴) > isobutyl dithiophosphate (E _Cu = −60 mV, SP ≈ 10⁻¹⁸). The visible agglomerates of precipitate particles are observed for all the studied sulfhydryl collectors (xanthates, dithiocarbamates, dithiophosphates) with the ethyl group of hydrocarbon radical. The butyl xanthate and isobutyl dithiophosphate form colloid precipitates with copper cations.     

Thermodynamics of reduction of sintered dolomite

The thermodynamic data are determined, and the variations in the standard values of the Gibbs energy (ΔG ⁰) are evaluated for three groups of reactions (selected among 32) of the silicothermic reduction of roasted dolomite, which differ in oxygen content in the reduction products and in the characteristics of the processes with a limited oxygen access (retort method), and of the vacuum silicothermic reduction both with the addition of dolomite and without it. It is established that the reduction reactions of roasted dolomite to Fe₂SiO₄, Ca₂SiO₄, and CaMg(SiO₃)₂ in the retort method, which are presented in classic works, have a positive or close-to-zero negative value of ΔG ⁰ and, consequently, are low-probable in practice. The reactions with the formation of a complex calcium-magnesium silicate Ca₃Mg(SiO₄) are more preferable thermodynamically. For the vacuum silicothermic reduction with the introduction of carbon and without it with the formation of Ca₂SiO₄ at 1200–1350 K, the negative value of ΔG ⁰ is larger by a factor of 4–8 by the absolute magnitude. The optimal temperature and kinetic parameters of these processes are found experimentally. It is shown that the use of carbon as an additional reducing agent stably increases the yield of Mg by 20–30%. In this case, the FeSi consumption decreases by a factor of 3 compared with the retort method and by a factor of 2 compared with the vacuum process without carbon. Our data served as the basis for the project task of designing an installation for the vacuum-silicothermic reduction of magnesium from roasted dolomites.     

Effect of the kinematics of rotary rolling on the fineness of the structure of hypereutectoid silumins

It has been established experimentally that the internal layers of cylindrical semifinished products that are made of hypereutectoid silumins and contain embedded lengthwise pins do not intermix during rotary rolling. The experiment also determined that the angles through which different concentric internal layers of the semifinished product (ω₁ > ω₂ > ω₃) are twisted are different and depend on the radii of those layers (R′₁ > R′₂ > R′₃). This finding contradicts the hypothesis of rigid sections in the classical theory of the strength of materials. An analytic relation (empirical formula) is found to describe the pitch of the internal layers of metal flow in relation to the main parameters of the rotary-rolling operation (the feed angle α and deformation ε) and the radius of the given internal layer (R′_x). Another empirical formula is proposed to determine the angle of inclination of the helical lines along which the metal inside the rolled specimen is displaced. A mathematical model is constructed to describe the dependence of the ductility properties of hypereutectoid silumin alloys on changes in the dimensions of the silicon crystals in the alloys when semifinished products made of these alloys are deformed by rotary rolling. __________ Translated from Metallurg, No. 8, pp. 68–72, August, 2006.     

Modulus of elasticity of some refractory compounds

Conclusions Measurements were made of the moduli of elasticity of nonporous refractory compounds prepared by the method of diffusion impregnation. The following values were obtained: 49,300±2000 kg/mm² for NbN, 58,700±2000 kg/mm² for TaN, 58,000±2000 kg/mm² for NbC, 65,000±2000 kg/mm² for NbB₂, 70,000±2000 kg/mm² for TaB₂, 68,500±2000 kg/mm² for Mo₂B₅, and 79,000±2000 kg/mm² for W₂B₅.Translated from Poroshkovaya Metallurgiya, No. 3 (63), pp. 32–33, March, 1968.     

Thermodynamics of formation of Th-Ni alloys

Electromotive force cells have been used to determine the Gibbs free energies, entropies, and enthalpies of phase formation for Th₂Ni₁₇, ThNi₅, ThNi₂, ThNi, and Th₇Ni₃. Solid CaF₂ was em ployed as the electrolyte, and it has previously been shown that CaF₂ is an ionic conductor over the temperature range of measurements, 841° to 1141°K. The experimental results can be correlated with the atomic coordinations in the crystal structures of these five Th-Ni intermediate phases. Formerly Graduate Student, Department of Metallurgy, Iowa State University     

Mechanism of fracture of dispersion-strenghthened tungsten

Conclusions In a dispersion-strengthened tungsten alloy fracture mechanisms change with rise in temperature in the same sequence as in unalloyed tungsten: quasibrittle cleavage at low temperatures is succeeded by partly tough fracture at 400°C (T _Br ^u1 ), tough fracture through the body of the grain is observed in the range from 1000 (T _Br ^u2 ) to 1600°C, and at 1800°C tough intergranular fracture commences. The cold-brittleness points of the dispersion-strengthened tungsten alloy are lower (T _Br ^u1 by 100 and T _Br ^u1 by 200°C) then those of unalloyed tungsten, while the temperature of transition to tough intergranular fracture is higher. As a result, the dispersion-strengthened alloy has a wider temperature range of tough transgranular fracture, with a larger value of. The wider range of tough transgranular fracture in the dispersion-strengthened tungsten alloy may be linked with a tendency for microvoids to form in the material on the second-phase particles, as a consequence of which subsequent fracture occurs by a microvoid coalescence mechanism.Translated from Poroshkovaya Metallurgiya, No. 7(283), pp. 31–35, July, 1986.     

Hot pressing of oxides of refractory metals

Conclusions A study was made of the sintering process in the hot pressing of several powdered oxides of transition metals, namely, TiO₂, ZrO₂, V₂O₅, Nb₂O₅, and Cr₂O₃. It was established that, at any given treatment duration, raising the temperature steadily increases the rate of densification and density of specimens. At each temperature, the densification process is characterized by a specific final density.Translated from Poroshkovaya Metallurgiya, No. 11 (107), pp. 22–25, November, 1971.     

Kinetics of oxychlorination of magnesium oxide

The kinetics of oxychlorination of MgO by Cl₂ + O₂ were studied in the temperature range from 850 °C to 1025 °C, using thermogravimetric analysis (TGA). The effects of Cl₂/O₂ ratio, gas velocity, temperature, and partial pressure of reactive gases on the reaction rate were investigated. The oxychlorination process was characterized by an apparent activation energy of about 214 kJ/mol. The reaction orders with respect to O₂, Cl₂, and Cl₂ + O₂ at 950 °C were about −0.37, 0.98, and 0.65, respectively. Data concerning oxychlorination of MgO, Cr₂O₃, and MgCr₂O₄ contained in chromite were compared. The effectiveness of using oxychlorination to extract iron oxides contained in magnesia was demonstrated.     

Investigation of the effect of temperature on the electrical and thermoelectrical properties of silicides of some transition metals

Conclusions The authors investigated the temperature dependence of the specific electric resistance of the silicides V₃Si, V₅Si₃, VSi₂, Fe₃Si, FeSi, MnSi, MnSi₂, Mn₅Si₂, Co₃Si, CoSi₂, Ni₃Si, Ni₂Si, Re₃Si, and ReSi and the absolute differential thermal-emf of the silicides V₃Si, VgSis, VSi₂, MnSi, Mn₅Si₃, MnSi₂.Fe₃Si, FeSi, FeSi₂, Co₃Si, CoSi, Ni₃Si, Ni₂Si, ZnSi₂, and TaSi₂ in the range from room temperature to 1000° (electric resistance) and 500° (thermal-emf). The silicides were obtained by direct synthesis from components; the samples for measurement, by sintering by means of the hot pressing method.The temperature dependence of the electric resistance of the suicides MnSi₂ and ReSi is typical of semiconductors. The silicides Fe₃Si and Co₃Si may be relegated to the class of ferromagnetic semimetals. A metallic character of dependence of the resistance on the temperature was found for the other investigated suicides. The shape of the temperature vs electric resistance curves indicates the complex multiband nature of the energetic spectrum of electrons in silicides.With the increase in the relative silicon content in silicides within the given metal-silicon system, there is an increase in the absolute value of the thermal-emf, and the nature of the temperature dependence becomes more complex.The thermal-emf of Re₃Si gave a zero value throughout the investigated temperature range. This substance is of practical interest as a material for contacts in high-temperature metal powder thermocouples.     

Construction of a mathematical model of sulfide sublimation of germanium from middlings

Based on empirical dependences of the value of a variable Y—the degree of sublimation of germanium (%) in the mode of sulfide melting (T = 1350°C, τ = 1 h)—on the values of the parameters that are characteristic of the content in charge, %, X ₁ × 10^?2, of the basicity {[CaO] + [MgO])/[SiO₂]}; X ₂ × 10^?3, of germanium; X ₃, of the slag-forming components (Σ[CaO], [MgO], [SiO₂]); X ₄, of carbon; and X ₅, of sulfur, by the method of computer mathematics with the use of the standard program packets Excel, Mathcad, and Maple, an adequate mathematical model of the influence of the charge composition on the degree of pyrometallurgical sublimation of germanium has been constructed.     

Kinetics of phase evolution of Zn-Fe intermetallics

The intermetallic phases, Γ (Fe₃3Zn₁₀), Γ₁, (Fe₅Zn₂₁), δ (FeZn₇, and ζ (FeZn₁₃), are mechanically alloyed through ball milling of pure elemental Fe and Zn powders under a controlled atmosphere of argon gas. The state of the as-ball-milled materials was crystalline, except for the Γ phase, which was amorphous. Phase-evolution kinetics through differential scanning calorimeter (DSC) measurements of the as-ball-milled powders show three characteristic transition temperatures for the Γ₁, and ζ phases, two for the Γ phase, and only one for the δ phase. The activation energies for the evolution of the milled powders to their equilibrium crystalline phases are 170 ± 1, 251 ±2, 176± 1, and 737 ±4 kJ/mol for the Γ, Γ₁, δ, and ζ phases, respectively. These values show that the mechanisms for the metastable-to-stable phase transition in these intermetallics are different, whereas diffusion over short distances may be part of the entire process in all cases.     

Sorption technology of recovery of indium from solutions of zinc production

Sorption of indium ions from polycomponent solutions with preliminarily reduced iron(III), which contain, g/dm³, 0.084 In³⁺, 6.2 Fe²⁺, 67.0 Zn²⁺, and 19.6 H₂SO₄, on the Metosol reagent, is investigated in the dynamic mode. The Metosol reagent represents montmorillonite of composition (Na,Ca)_0.3(Al,Mg)₂Si₄O₁₀(OH)₂(H₂O) _n , modified with di(2-ethylhexyl)phosphoric acid. The absorption dynamics of ions by it is investigated by frontal chromatography. The values of working (DEC) and total (CDEC) dynamic exchange capacities of the mineral sorbent are determined depending on the eluent specific passing rate and temperature. The main parameters of the sorption technology of the selective recovery of indium from process solutions of the zinc production on the Metosol reagent in columns followed by the desorption of metal with the hydrochloric acid solution (1: 1) are substantiated and calculated.     

An investigation of the thermodynamics of solvent extraction of metals III. Prediction of the composition of the equilibrated organic phase

Based on the known composition of the aqueous phase, a thermodynamic extraction equilibrium model can be used to solve for the equilibrated organic component concentrations simultaneously. In this model, the non-ideality of both the organic and aqueous phase is considered. Several metal neutral solvent extraction systems, such as TBP—UO₂(NO₃)₂, (C₇H₁₅)₂SOUO₂(NO₃)₂ and TBP—UO₂Cl₂, have been used to verify the applicability of this model. The predicted compositions are in good agreement with the experimentally measured results.     

A Review of the Mechanisms of Fatigue

Abstract

Relationships between structure and fatigue properties are briefly reviewed for metals and alloys of the facecentred cubic structure. The effects are considered of stressor strain amplitude, temperature, stacking fault energy, strain ageing, degree of order, precipitation and dispersion hardening, and fibre strengthening, upon crack initiation and propagation.

Résumé

L'auteur traite brièvement des rapports entre la structure et la résistance à la fatigue des métaux et alliages cubiques à faces centrées. II passe en revue L'influence de l'intensité de la contrainte, de l'amplitude de la ,déformation, de la temperature, de l' énergie de faute d'empilement, du vieillissement après déformation, de la nature de l'ordre, du durcissement par précipitation et dispersion, et du renforcement à l'aide de fibres, sur la formation et.la propagation des fissures.