Oxidation behaviour of Fe3Alnanoparticles prepared by hydrogen plasma–metal reaction

Abstract

Fe3Alnanoparticles have been synthesized by the hydrogen plasma–metal reactionmethod. In order to study the oxidation behaviour of the intermetallicnanoparticles, changes in morphology, particle size and crystal structure duringheat treatment in air were investigated by transmission electron microscopy andx-ray diffraction. The as-prepared nanoparticles were stable both in shapeand structure at 473 K where the iron nanoparticles were known to beoxidized fully. The high oxidation resistance of intermetallic nanoparticleswas attributed to the aluminum oxide layer. The oxidation of Fe3Alnanoparticles proceeded slowly below 573 K and rapidly above thistemperature. The oxides formed between 473 and 673 K were Al2O3and a mixture of iron oxides (α-Fe2O3 and γ-Fe2O3)changing into single phase α-Fe2O3at 873 K. The nanoparticles started to grow by coalescence at 573 K and themean particle size was larger than 100 nm above 673 K.