Synthesis and structural features of Ni–Al nanoparticles by hydrogen plasma–metal reaction

Eight kinds of Ni–Al nanoparticles have been prepared by hydrogen plasma–metal reaction. The morphology, crystal structure and chemical composition of the nanoparticles obtained in this study were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD) and induction-coupled plasma (ICP) spectroscopy. The particle size was determined by TEM and BET gas adsorption. It was found that all the nanoparticles have spherical shapes, with average particle size in the range of 14∼62 nm. The crystal structures of Ni–Al nanoparticles vary with the composition of master alloys. Pure Al3Ni2 (D513), NiAl (B2) and Ni3Al (L12) structures were successfully produced with 55.0, 58.3 and 72.6 at.% Ni in bulk, respectively. The analysis result about the phase equilibrium based on the crystal structures of nanoparticles is not consistent with those based on the equilibrium phase diagram.