Solid state phase transformations during the oxidation of copper sulfides: Roaster diagrams for the Cu-S-O system

Abstract

Roaster diagrams that represent the stabilities of condensed phases as a function of temperature and percent oxygen appear to be more useful than the predominance area diagrams (PADs), which show the stability of different phases in the metal-sulfur-oxygen system at constant temperature. Roaster diagrams can be obtained from PADs and represent the intersection of total pressure lines with lines on a PAD extended in temperature. In this paper, PADs at four different temperatures and roaster diagrams for the system Cu-S-O are derived from PADs at total pressures of 0.25 atm and 1 atm. These diagrams show that at total pressures of 0.25 atm and 1 atm the CuO/CuO·CuSO4 phase transformation occurs at 1063 K and 1133 K at 50% oxygen. The more complex four-component system Cu-As-S-O will follow in a subsequent publications.