An Investigation on the Mechanism of TiC+Al₂O₃ Combustion Synthesis via Mechanical Activation of Double Phases in TiO₂-Al-C System

The starting reaction in the combustion synthesis process in TiO2-Al-C system leading to TiC+Al2O3 composite was evaluated using a combination of Differential Thermal Analysis (DTA), X-Ray Diffraction (XRD) and Transmission Electron Microscope (TEM). Double phases in 3TiO2- 4Al-3C system were milled separately and then the third phase was added according to the stoichiometric reaction for 3TiC+2Al2O3 composite formation. The combustion synthesis temperature was observed to decrease from 962 °C to 649 °C after mechanical activation of TiO2/Al mixture for 16 hr. On the contrary, the mechanical activation of Al/C and TiO2/C mixtures for 16 hr made the reaction temperature increase to 995 °C and 1024 °C, respectively. TEM and XRD patterns of as-milled powders showed that the reaction temperature changes could be due to increased TiO2 and Al interface area. In addition, DTA experiments showed that for the sample in which TiO2 and Al were mechanically activated the reaction occurred at the temperature even lower than the aluminum melting point.