Implementation of Combined Mechanical Activation and Thermal Analysis for Identification of Combustion Synthesis Mechanism in TiO۲-Al -C System

Abstract:A combination of mechanical activation and Differential Thermal Analysis (DTA) together with X-Ray Diffraction (XRD), and various microstractural characterization techniques were used to evaluate the starting reaction in the combustion synthesis of TiC-Al۲O۳ composite in TiO۲-Al-C system. The mechanical activation was performed on the mixtures of two components of TiO۲/Al, Al/C and TiO۲/C and then the third component was added according to the stoichiometric reaction for ۳TiC+۲Al۲O۳ composite formation. The powder mixtures were heated up to ۱۴۵۰ °C under Argon atmosphere at a heating rate of ۱۰ °C/min. The combustion synthesis temperature was observed to decrease from ۹۶۲ °C to ۶۴۹ °C after milling of TiO۲/Al mixture for ۱۶ hr. On the contrary, the mechanical activation of Al/C and TiO۲/C mixtures for ۱۶ hr made the reaction temperature increase to ۹۹۵ °C and ۱۰۲۴ °C, respectively. The decrease in reaction temperature as a result of milling the TiO۲/Al mixture could be due to an increase of TiO۲ and Al interface area as confirmed by TEM micrographs and XRD patterns of milled powder mixture. In addition, DTA experiments showed that for the sample in which TiO۲ and Al were mechanically activated the reaction occurred at the temperature even lower than that of Al melting point.