Papers by Author: A.B. Shubin

Abstract: Thermal decomposition of copper digallide was studied using experimental (thermal analysis) and theoretical (thermodynamic modeling) methods. The temperatures of CuGa₂ incongruent melting are in satisfactory agreement between experimental and calculated values. Small differences with the phase diagram can be explained by minor non-stoichiometry of the alloy samples. The experimental studies of thermal diffusivity and thermal expansion of CuGa₂ were performed in the temperature range 298-500 K. The heat conductivity coefficient was further calculated using literary data concerning the density and heat capacity of the copper digallide.

Abstract: The solidification of binary Al-Sc melts containing small amounts of scandium (< 2 wt.%) have been investigated. We studied concentration profiles in long Al-Sc as cast ingots formed by slow cooling of the liquid alloys. It was found that minor addition of transition metals like Ti can lead to the formation of large (about 10-20 μm) spherical intermetallic particles (Al₃Sc containing some amount of isomorphic Ti). These sphere-like particles are forming during the crystallization of liquid solution of Sc in Al (before the precipitation on nanosize spherical particles from the solid solutions). The results of SEM and EDX investigations of these alloys are also presented in this paper.

Abstract: Gallium-based diffusive-hardening solders do not contain lead. These alloys have specific rheological properties. Their synthesis includes, as a rule, mechanical mixing of such initial components as gallium, copper and tin powders [1]. Then the metallic paste undergoes irreversible phase transformations forming a solid alloy with a specific structure. Here, we investigated microstructures of diffusive-hardened Cu-Ga-Sn alloys by SEM and EDX methods. Thermal diffusivity and heat conductivity of alloys mentioned above were studied by the laser flash method. Also differential scanning calorimetry (DSC) experiments were performed to obtain heat properties of the samples.

Abstract: Thin scandium-containing layers fabricated by different methods are good systems to investigate some properties of Al-Sc intermetallic compounds (IMC). The electrochemical deposition of a thin scandium layer onto a solid metallic surface leads to complex diffusion processes, especially if the second metal forms a number of IMC with Sc. Here, we used the electromotive force (EMF) method to study thin Al-Sc films in dynamics. Also, the Al-Sc alloy layers were prepared by direct aluminium-scandium interaction. The results of SEM and EDX investigations of these alloys are also presented in this paper. Analogue coatings (like Sc on Ni, Y on Cu, Al on Ni etc.) were also considered in order to discuss the phase sequence formation.

Abstract: Properties of diffusive-hardening pastes based on liquid gallium have been investigated. The optimal conditions were found for producing the paste (solder) with best technological characteristics. The liquid-solid ratio, powder alloy composition and dispersity, dust fractions percentage, exposition time and temperature are the main factors which determine the rheological properties of the gallium paste.

Abstract: The interaction between manganese(II) oxide and carbon in powder mixtures may give manganese carbides, condensed(c) and gaseous(g) manganese at different temperatures and pressures. The initial assumptions and results of thermodynamic modelling of this interaction in the temperature range 1600-2100 K at the pressures 0.1-1.0 MPa are presented in this paper.