Synthesis of Fe–Al nanoparticles by hydrogen plasma–metal reaction

Abstract

Fe–Al nanoparticles of eight kinds have been prepared by hydrogen plasma–metalreaction. The morphology, crystal structure, and chemical composition of thenanoparticles 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 gasadsorption. It was found that all the nanoparticles have spherical shapes, withaverage particle size in the range of 29–46 nm. The oxide layer in nanoparticlescontaining Al after passivation is not observable by XRD and TEM. The Alcontents in Fe–Al ultrafine particles are about 1.2–1.5 times those in the masteralloys. The evaporation speeds of Al and Fe in Fe–Al alloys are mutuallyaccelerated at a certain composition. The crystal structures of the Fe–Alnanoparticles vary with the composition of the master alloys. Pure Fe3Al (D03)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 equilibriumphase diagram and there is no intermetallic formation except that of Fe3Aland FeAl.