Eutectic reaction between copper oxide and titanium dioxide

Eutectic reaction between copper oxide (CuO) and titanium dioxide (TiO2) was investigated by using directly Cu and TiO2 samples and by employing optical microscopy, X-ray diffraction (XRD), scanning electron microscopy, and electron probe for microanalysis (EPMA). Different types of samples including Cu plate/TiO2 pellet samples and TiO2/Cu/TiO2 sandwiched samples were prepared. The samples would react with each other at as considerably low as about 900°C in air, which is due to a eutectic reaction. The reaction diagram was generated, in which different reaction categories were denoted at various temperatures (300–1070°C) and times. After annealing, the weight changes normalized to the original Cu samples were also analyzed to verify the eutectic reaction. The eutectic was identified to be the CuO–TiO2 system characterized from XRD and EPMA analyses. Annealing in N2/O2=9 at the same temperature as in air resulted in similar but not so drastic eutectic melting phenomena. The eutectic reaction would enhance significantly the grain growth of TiO2 and the oxidation of Cu. The changes in the microstructures and the morphologies of the samples were also investigated. The eutectic temperatures of CuO and other oxide systems were compared and discussed. The eutectic points as well as the phase diagram of the CuO–TiO2 system were calculated and analyzed. Several potential applications of the reactions were also proposed.