Synthesis and characterization of MOSI2-MO5SI3 nanocomposite by mechanical alloying and heat treatment

Abstract

The nanocomposite of MoSi2-Mo5Si3 powder was synthesized by mechanical alloying from Mo and Si powder mixture at room temperature. The phase evaluation of powder after various milling durations and heat treatments were assessed via X-ray diffraction (XRD) and a differential thermal analysis (DTA). Morphology and microstructure of powder particles were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results revealed that nanocomposite of MoSi2-Mo5Si3 powder was synthesized by combustion reaction of Mo and Si powder using ball milling. In the early stages of ball milling beta-MoSi2 was produced. However with continued milling for 48 h alpha-MoSi2 and Mo5Si3 phases were formed. DTA results of 24 h and 48 h as milled mechanical alloyed specimens showed a well-defined peak at 852 degrees C and 920 degrees C relating to the formation of alpha-MoSi2. The activation energy for 24 h and 48 h milled specimens were -128.6 KJ/mol and -121.4 KJ/mol respectively. Annealing the milled specimens at 1000 degrees C for 2 h revealed the phase transformation of beta-Mosi(2) to alpha-MoSi2 and the formation of Mo5Si3. The crystallite size of alpha-MoSi2 and Mo5Si3 were about 9 nm and 12 nm after 48 h mechanical alloying. These values increased slightly to 18 nm and 14 nm after annealing at 1000 degrees C.