Experimental Determination of the Liquidus Surface of the Cu-O-ZnO-CaO System in Equilibrium with Air
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THE Cu-O-ZnO-CaO system is widely used in ceramics and advanced materials.[1–4] Phase diagrams provide road maps for processing and facilitating the understanding of material properties, and accurate thermodynamic information of the system is important in enhancing the performance of these applications. Due to the increasing association of impurities in ore minerals and concentrates, and the increasing amount of secondary raw materials in metallurgical industry, smelters are in great need to re-design the operating flow sheets and optimize the processing parameters. The Cu-O-ZnO-CaO system is widely used in pyrometallurgical processing of copper and zinc.[5,6] Phase relationships in the Cu-O-ZnO-CaO system have significant importance in reducing operating costs, and developing new flow sheets. However, experimental phase equilibria and thermodynamic information about this system is still uncompleted in the literature. Equilibrium information of simple systems such as binaries and ternaries provides knowledge for
LONGGONG XIA, Ph.D. Candidate, is with the Metallurgical Thermodynamics and Modeling Research Group, School of Chemical Technology, Aalto University, 02150 Espoo, Finland, and also with the School of Metallurgy and Environment, Central South University, Changsha 410083, Hunan, China. Contact e-mail: longgong.xia@ aalto.fi ZHIHONG LIU, Professor, is with the School of Metallurgy and Environment, Central South University. PEKKA TASKINEN, Professor, is with the Metallurgical Thermodynamics and Modeling Research Group, School of Chemical Technology, Aalto University, and also Visiting Professor with the School of Metallurgy and Environment, Central South University. Manuscript submitted March 7, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
developing accurate thermodynamic descriptions of high-order systems. Phase equilibria of the ZnO-CaO, Cu-O-CaO, and Cu-O-ZnO subsystems have been systematically studied by several researchers.[7–14] In the binary ZnO-CaO system, the effect of temperature on the solubility of ZnO and CaO in the other phase, and the composition of liquidus has been experimentally studied in air using the equilibration/quenching/EPMA (Electron Probe X-ray Micro-Analyzer) technique.[7] The ZnO-CaO phase diagram has one binary eutectic point occurring at 1808 K ± 2 K (1535 °C ± 2 °C) and 0.6546 mole fraction of wurtzite (ZnO). The phase equilibration of the Cu-O-ZnO system in equilibrium with air (pO2 ¼ 0:21 atm) and metallic copper (in pure argon) has been studied in a previous study.[8] The phases in equilibrium with air within the temperature range from 1368 K to 1773 K (1095 °C to 1500 °C) have been analyzed by EPMA. The pseudo-binary phase diagram (‘Cu2O’-ZnO) has two primary phase fields of cuprite (‘Cu2O’) and zincite (ZnO), and one binary eutectic point, occurring at 1371 K ± 2 K (1098 °C ± 2 °C) and 0.10 ± 0.01 mole fraction of ZnO. Phase relationships of the Cu-O-CaO system have been investigated by different researchers.[9–14] Three ternary compounds (Ca2CuO3, CaCu2O3, and Ca1xCuO2) were
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