A kinetic study of the strontium extraction by metallothermic reduction using submerged SrO powders injection

Preparation of Al–Cu alloys by aluminothermic reduction of CuO using submerged powder injection assisted with mechanical agitation: thermodynamic approach and kinetic measurements

“…According to Guedes et al, 14 a layer of Al 2 O 3 forms at the beginning of the reduction reaction of CuO, when no magnesium is present in the molten alloy. The growth of this layer hinders contact between the molten aluminium and the reaction front by working as a diffusion barrier to both Al and Cu transport, which prevents the reaction given by equation (2) to complete. Nevertheless, the layer of Al 2 O 3 is not completely impervious, thus having some porosity through which aluminium 2 Variation of Cu concentration in molten aluminium as function of CuO addition time for indicated temperatures: particle size was ,50 mm, and absence of Mg can diffuse to the boundary layer, where it reaches the CuO particle surface.…”

“…No fluxing or degassing of the melt was performed after melting, and the alloy was only treated to increase its copper concentration. The quantity of CuO powder to be injected corresponded to the amount stoichiometrically required, according to the reaction given by equation (2), in order to reach a final concentration of Cu in the melt of 8?76 wt-%. The total treatment time was of 180 min.…”

“…The equilibrium analysis described above is important for stating that the main chemical reaction that must occur is that given by equation (2), no matter that the value of its Gibbs free energy is not as negative as that of the reactions given by equation (7) or (11). In this sense, it can be considered that the main role of magnesium is lowering the surface tension of the molten phase, although some increase in the reactivity of the molten bath can be gained by adding it.…”

“…1 Currently, aluminothermic reduction is used to obtain aluminium master alloys such as Al-SrMg, Al-Ce-Mg, Al-Zn, Al-Mn, Al-Zr, Al-Mg-Fe-Cr, Al-Li, Al-Ni, etc. [2][3][4][5][6][7][8][9][10] On the other hand, copper is broadly known to represent one of the main alloying elements in aluminium alloys, and its consumption in the automotive and aerospace industries has consequently increased in recent years. The main effect of copper in aluminium alloys is the considerable improvement in mechanical properties obtained after the aging and thermal heat treatment of alloys such as the 2xx.x and 3xx.x types.…”

“…From a thermodynamic point of view, the aluminothermic reduction of CuO is possible through the following chemical reaction, which may occur at the temperature of molten aluminium, i.e. 1273 K CuOz2=3Al~Cu ½ Al z1=3Al 2 O 3 (2) As copper is dissolved in the molten metal, the following equation must be used for determining the value of the Gibbs free energy of reaction…”