Synthesis of Fe Al nanoparticles by hydrogen plasma metal reaction

Fe–Al nanoparticles of eight kinds have been prepared by hydrogen plasma–metal reaction. The morphology, crystal structure, and chemical composition of the nanoparticles obtained were investigated by transmission electron microscopy (TEM), x-ray diffractometry (XRD), and induction-coupled plasma spectroscopy. The particle size was determined by TEM and Brunaumer–Emmet–Teller gas adsorption. It was found that all the nanoparticles have spherical shapes, with average particle size in the range of 29–46 nm. The oxide layer in nanoparticles containing Al after passivation is not observable by XRD and TEM. The Al contents in Fe–Al ultrafine particles are about 1.2–1.5 times those in the master alloys. The evaporation speeds of Al and Fe in Fe–Al alloys are mutually accelerated at a certain composition. The crystal structures of the Fe–Al nanoparticles vary with the composition of the master alloys. Pure Fe 3 Al (D0 3 ) and FeAl (B2) structures are successfully produced with 15 and 25 at.% Al in bulks, respectively. For samples of Fe–Al nanoparticles with Al content over 56.5 at.%, the crystal structures of the nanoparticles do not comply with the equilibrium phase diagram and there is no intermetallic formation except that of Fe 3 Al and FeAl.