Effect of Milling Speed on Fabrication Al2O3-ZrB2 in Situ Nano-Composite Powder Via Mechanochemical Synthesis

In this study the effect of milling speed on Al/ZrO2/H3BO3 combustion system is evaluated. The powders were milled at different speed (350، 450 and 500 rpm) for 15 hours. Also، differential thermal analysis (DSC) was performed on the samples. In order to investigate the formed phases، XRD phase analysis was done on the samples. The results showed that the formation of composite has not been achieved at low speeds، and only some intermetallic phases (such as Al-B) were appeared. Also، by increasing the speed of milling، the probability of composite synthesis (in the chamber) will increase. However، increasing the milling speed up to 500 rpm leads to the formation of the composite inside the mill by mechanochemical method with releasing substantial amount of heat. Scanning electron microscopy results show that the morphology of the synthesized composite is highly porous one. The average grain size of alumina and zirconium borides were measured 58 and 42 nm، respectively.