The impact of copper aluminium oxide for society
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3.1. The effect of different alumina precursors on the formation of CuAl2O4
The formation of CuAl2O4 was found to occur at different temperatures, depending on the form of alumina (or precursor) used. α-Alumina did not react appreciably with CuO at 900 °C, even after four repetitions of milling and calcination for 6 hours on the same sample, as confirmed by the absence of peaks belonging to CuAl2O4 in the XRD diffractograms shown in Fig. 1. However, when calcined in air at the higher temperature of 1000 °C for 6 hours, a significant amount of CuAl2O4 was formed and further milling and calcining led to the formation of CuAlO2 with almost all the free alumina consumed by the 4th calcination. When calcined at 950 °C, a small amount of CuAl2O4 but no CuAlO2 was detected in the material. This observation is in agreement with the finding of Jacob and Alcock that in an atmosphere with PO2 = 0.21 bar, reaction (4) has an equilibrium temperature of 1003 °C.14
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