Synthesis and thermal analysis of nanocomposites based on intermetallic compounds in the Ni-Al system and Al2O3

Abstract

This study investigated the synthesis of intermetallic compounds in the Ni-Al system based nanocomposite powders with Al2O3 by mechanical alloying (MA) of NiO and Al powder mixture with various compositions. The structural changes of powder particles during mechanical alloying were studied by X-ray diffractometry (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The thermal analysis of as-milled powders was examined by differential scanning calorimetry (DSC). XRD results revealed that the intermetallic phase was first noticed for all compositions investigated in the current study after 1 h milling. The formation of intermetallic phase, however, was completed after 3 h milling for NiAl and Ni3Al4 phases and after 2 h for Ni3Al phase. The unreacted NiO present in as milled powder is reduced by Al at 590°C on heating. The TEM micrographs of 3 h milled NiAl-Al2O3, Ni3Al4-Al2O3 and Ni3Al-Al2O3 powder particles reveal the nanocrystallinity of the powders.