Synthesis of (Ti_x,W_1-x)_3 SiC_2 MAX phase by mechanical milling

This study has investigated the synthesis of (Ti_1-xWx)_3SiC_2 MAX phase via high energy ball milling, and the effect of heat treatment and excess Si on the purity of synthesized powder were explored. In this regards, different mixtures of Ti, Si, and C were ball milled by a planetary ball mill for various milling times up to 15h. The phase evolution of products was studied by X-ray diffraction (XRD), and the morphological changes monitored by a field emission scanning electron microscopy (FESEM) equipped with energy-dispersive spectroscopy (EDS). The results showed that after 15 hours of ball milling the reaction started, and resulted in Ti_3SiC_2 and TiC formation. The as- synthesized powders were then compacted and heat treated at 600, 1000, 1250 and 1400˚C. Heat treatment caused to proceed in the reaction between the intermetallic compounds in Si-Ti system and TiC, and led to increasing the purity of Ti_3SiC_2. In a separate run, a non-stoichiometric composition of Ti: Si:C= 3:1.2:2 was ball milled for 15 h, and heat treated at 1250˚C. The XRD results showed that the purity of the product is higher than the stoichiometric composition. The addition of W to Ti_3SiC_2 was also explored. In this regard, the synthesis of (Ti_1-xW_x)_3SiC_2 component (x= 0.8, 0.5) was investigated, and the results showed that some W incorporated in Ti_3SiC_2 structure, and the WC and Ti_xW_1-x formed during the process.