Thermodynamic and Structural Study of the Copper-Aluminum System by the Electrochemical Method Using a Copper-Selective Beta″ Alumina Membrane

Abstract

The liquid phase thermodynamic of mixing of the copper-aluminium binary system is investigated as a function of temperature and composition using the electrochemical potential difference method. A copper-selective beta" alumina (Cuβ"Al 2 O 3 ) is used as a solid electrolyte, synthesized through ion exchange, sintering from base oxide powders, and the floating zone method of crystal growth. Measured thermodynamic of mixing data were used to inform short range ordering in copper-aluminium melts through Darken's factor for excess stability and Bhatia-Thornton structure factors, revealing a strong departure from ideality and pronounced ordering. Mixing properties were used to predict viscosity and self-diffusion coefficients. Features observed in calculated electronic entropy of mixing for copper-aluminium were compared to trends in viscosity, demonstrating the utility of electronic property of mixing in the description of structure-properties in this liquid binary system.

Electrochemical Methods for the Study of Liquid Metals: Highlights from Metallurgical Transactions

“…§ The thermodynamic formalism presented above is applicable to any liquid solution behavior, including as it evolves with temperature. However, we herein propose to sort solutions into 4 categories; dilute (e.g., O in Fe at 1600 °C, [17] ) fully miscible (e.g., Al in Cu [18] ), phase separating (e.g., S in Cu [19] ) or reacting (e.g., yttrium (Y) in Al saturated with alumina (Al 2 O 3 ) [20] ). Independently, we sort experimental methods according to the standard state of the solute B; gaseous (G), liquid (L) or solid (s).…”

“…[47] Solid electrolytes can also handle B in a liquid standard state in solution in a liquid metal A, though the papers surveyed herein indicate that it is rare to investigate the entire composition range. One recent report using Cu-b alumina (Al 2 O 3 ) [18] provided the first data across the entire liquid system Al-Cu, using a copper reference electrode. Borate electrolytes to study boron seem to be an exception, because molten borates are both not too reactive and compatible with several metals.…”