Conditions and stages of flotation of gold dispersed drops in silicate melts

N. A. Vatolin, A. M. Amdur, V. V. Pavlov, S. A. Fedorov.

ABSTRACT:

The flotation of droplets in liquids occurs frequently. For example, the flotation is the basis for the removal of liquid non-metallic inclusions from steel. Meanwhile, the mechanism of this process is has not been sufficiently studied. The paper describes in detail the mechanism of flotation of metal droplets in the melt for example of gold: the kinetics and formation stages of the gas bubble–gold droplet system, as well as the subsequent gold flotation in the melt, are considered. Once a gas bubble and a micro-droplet have concerned, a third surface gold–gas and a wetting perimeter appear, in addition to the previously existing melt-gas (around the bubble) and gold–melt (around the droplet) surfaces. The time for achieving equilibrium for gold micro-droplets with a radius of about 3 μm has an order of 10–4 s. Consequently, the formation of an equilibrium bubble-drop system is occurs rapidly and does not hinder the overall process of collecting and fusion of gold micro-droplets by gas bubbles. The flotation condition providing an excess of the interfacial tension forces over the gravity force is analyzed in relation to the system of dispersed droplets (gold, platinum and palladium)—oxide melt. This condition holds for metal droplets with a radius of up to 3500 μm.

KEYWORDS:

flotation, spreading, gas bubble, droplet, interphase tension, wetting perimeter, wetting angle, gold

DOI: 10.1134/S0235010618060075

Computer simulation of multicomponent melts of metallurgical slags

E. V. Dyul’dina, B. R. Gelchinski, V. N. Selivanov

ABSTRACT

Based on the experimental data on the density, the molecular dynamics simulation of multicomponent oxide-fluoride metallurgical slagFforming systems: SiO2–CaO–Al2O3–MgO–CaF2–Na2O–K2O–FeO was carried out for the first time in the approximation of the ionic bond model. The results were discussed and compared with literary experimental and calculated data. The obtained model indicates a weak temperature dependence of the structure of the melt. An increased diffusion mobility of fluorine ions as well as ions of alkali metals in comparison with other elements has been revealed.

KEYWORDS

melt, metallurgical slag, computer simulation, structure, properties

Model investigation of liquid interaction metal and dispersed steel inclusions in castingon gasificable models

B. S. Vorontsov, N. V. Nesterov

ABSTRACT

A mathematical model for the interaction of liquid metal with metallic inclusions embedded in the foam polystyrene, reflecting the filling of molds, the effect of thermal decomposition of expanded polystyrene and heat exchange of the base alloy and filler material, is developed. The resulted results of the experiment on obtaining prototypes by casting on gasified models, confirming the predictions of mathematical modeling.

KEYWORDS

mathematical model, interaction of metal particles with melt, local alloying, casting for gasified models, composite materials

Formation of the structure and properties of multi-component iron based alloys in dependence on the conditions of the solidification of hydrogenated melts.

R. M. Belyakova, V. A. Polukhin, N. I. Sidorov

ABSTRACT

The regularities of the behavior of the absorbed surfactant element (p.a.e.) of hydrogen on the peculiarities of the formation and phase structure in the multicomponent systems based on iron: steel, cast iron and alloys of the FINEMET group were studied. An analysis of the diffusion activity of elements with hydrogen adsorbed on them, hydrogen permeability, types of interatomic bonds as a result of interaction of elements and their influence on the functional properties of the products of structural design are carried out. The purpose of the work is to establish the nature of the interatomic bonds of adsorbed on the elements of the multi-component iron alloys of surface-active hydrogen and its influence on the functional and operational properties of the metal products under the changing conditions of their structuring.

KEYWORDS

interatomic interactions, types of bonds, polymorphic phase transitions, hydrogen, nanostructured phases, ferrite, graphite, carbides, structure and properties of matrices in products

Peculiarities of self-diffusion and shear viscosity in transition and transition metals

N. P. Malomuzh, V. N. Makhlaychuk

ABSTRACT

The paper discusses the behavior of the coefficients of shear viscosity and self-diffusion in liquid transition and post-transition metals, as well as their melts. It is shown that the application of activation concepts to the description of temperature dependences of the coefficients of shear viscosity and self-diffusion is incorrect. It is established that the shear viscosity of transition and post-transition metals is described with high accuracy by the same formulas as for alkali metals. This means that the key role in the formation of viscosity is played by the effects of the “roughness” of molecular layers shifting relative to each other. It is shown that self-diffusion coefficients should be considered as a superposition of two independent contributions – chaotic local mixing and collective drift, which is a characteristic feature of only the liquid state of matter. The values of the ion radii of the metals under consideration are discussed.

KEYWORDS

self-diffusion coefficient, shear viscosity, liquid transition and post-transition metals

Theory of self-diffusion in liquid metals

N. P. Malomuzh, V. N. Makhlaychuk

ABSTRACT

The paper discusses the physical nature of the coefficient of self-diffusion in liquid alkali metals. The self-diffusion coefficient D is represented as two contributions: single-particle and collective. It is shown that the contribution of the collective component in the vicinity of the melting point is 5–6% and with increasing temperature to where – the critical temperature reaches 25–30%. The sum of the single-particle and collective contributions reproduces the experimental values and the temperature dependence and self-diffusion coefficient of liquid alkali metals with a very satisfactory accuracy (above 95%). A new method for calculating the radii of ions of liquid metals based on an analysis of their shear viscosity is proposed. On the basis of similarity considerations, the question of the applicability of Einstein’s formula for determining single-particle contributions to the coefficient of self-diffusion of low-molecular liquids and liquid metals is discussed. A new formulation of the similarity principle for liquid metals is proposed.

KEYWORDS

self-diffusion coefficient, liquid alkali metals

Influence of niobium and tantalum on peculiarities of phase formation at metallothermic interaction between aluminium and titanium dioxide

T. V. Osinkina, S. A. Krasikov, E. M. Zhilina, S. N. Agafonov,

L. B. Vedmid, S. V. Zhidovinova

ABSTRACT

Thermodynamic modeling of joint aluminothermic reduction of titan, niobium and tantalum from oxides have been carried out. The results were coordinated with research of this process by a method of the combined scanning calorimetry and indicators of metal-thermic obtaining alloy Al–Ti–Nb in the laboratory electric furnace.

KEYWORDS

thermodynamic modeling, aluminothermic reduction, alloy, intermetallic compounds, oxides

Methods of determining critical parameters of d-metals

O. S. Nikolaev

ABSTRACT

New methods for determining the critical parameters of d-metals are briefly considered. Molybdenum and tungsten are taken as examples of the calculation. The values of critical parameters are known for molybdenum. This allows you to check the calculated values.

KEYWORDS

critical parameter, molybdenum, tungsten

Precrystallization Changes in Structural Dynamic Characteristics of Amorphous Metallic Melts under Deep Cooling, Glassforming and Hydrogenation

V. A. Polukhin, N. I. Sidorov, N. A. Vatolin

ABSTRACT

The processes of amorphization and crystallization of binary and multicomponent melts based on transition metals are considered. A comparative analysis of pre-crystallization structural changes and atomic dynamics in conditions of forced quenching and deep supercooling of metallic melts and other liquid substances, depending on their composition, the size of the atoms, the nature of the interatomic bonds, the presence of eutectics and saddles on the phase diagrams of states is carried out. Hydrogenation of the melts introduces additional specificity on the flow of pre-crystallization processes, affecting the atomic configuration, the modulation of the frequency spectrum and the fluctuations of the band (electronic) structure that determines the specificity of vitrification.

KEYWORDS

multicomponent melts, transition metals, atomic dynamics, configuration, interatomic bonds, molecular dynamics, hydrogenation, vitrification, phonons, band structure, precursors, viscosity, diffusion, levitation, crossovers, frequency

Experimental estimation of peculiarities of interaction of titanium oxides and gadolinium with aluminum

L. B. Vedmid, E. M. Zhilina, S. A. Krasikov, A. G. Merkushev

ABSTRACT

Theoretical and experimental evaluation of the aluminothermic reduction processes of titanium and gadolinium from oxides allowed us to establish the sequence of compounds formation in the Al–TiO2–Gd2O3 system. It was noted that the reduction is a two-stage process, proceeds through the stage of titanium monoxide formation, followed by formation of intermetallides Al3Ti and GdAl2.

KEYWORDS:

titanium alloy, aluminothermic reduction, phase formation, gadolinium, intermetallic compounds