Diffusion in copper sulphides. An experimental study of chalcocite, chalcopyrite and bornite

摘要

Diffusion measurements on three copper-containing sulphides have been performed by an electrochemical potentiometric method. Chalcocite (Cu(sub 2)S), Chalcopyrite (CuFeS(sub 2)) and Bornite (Cu(sub 5)FeS(sub 4)) were synthesized and fully characterized by X-ray diffraction. The diffusivities were measured on compacted powders yielding both the chemical and the component diffusion coefficients in the temperature range 5-50 C. The chemical diffusion coefficients found were: for Chalcocite 38.7*exp (-5600/T), for Chalcopyrite 15.4*exp(-6000/T) and for Bornite 14.4*exp(-4900/T). The diffusion coefficient for Chalcocite is in good agreement with values found previously, and a reasonable agreement is also found for Chalcopyrite and Bornite when our data are compared with values acquired at much higher temperatures with a different technique. The activation energies (here on a Kelvin scale) are remarkably similar for the three sulfides, considering that their relative errors are of a 10% magnitude, which indicates that the bonding strengths and the diffusion mechanisms are similar. The chemical diffusion coefficients which enter the empirical Fick's diffusion laws that describe concentration changes, are of the order of exp(-8) to exp (-7) cm(sup 2)/s at room temperature. Such values bring the ion mobilities near values found for solid state 'fast ion conductors', used as electrolytes at elevated temperatures. 17 refs, 8 figs, 5 tabs. (Atomindex citation 27:028224)