Catalytic synthesis and enhanced Curie temperature of ε-Fe3N@C nanostructure synthesized in a tetraethylenepentamine solution

ε-Fe3N@C nanocrystals without oxidation are one-pot synthesized by using the iron(II) acetylacetonate and tetraethylenepentamine (TEPA) as Fe and N precursors under a low temperature (533 K) in the presence of a small quantity of Pt atoms as the co-catalyst. The ε-Fe3N@C nanoparticles with a core-shell structure are nearly spherical and have a wide particle size distribution of 100-500 nm in diameter. Fe nanoparticles obtained by reduction of Fe2+ with TEPA are an effective catalyzer for decomposing TEPA to produce N and C atoms at a temperature much lower than the boiling point of TEPA. The diffusion of N atoms into Fe nanoparticles for the formation of ε-Fe3N@C is proposed, based on the results obtained by kinetically controlling the synthetic temperature and surfactants. The ε-Fe3N@C nanoparticles have an excellent saturation magnetization of 135.5 emu/g at room temperature. A significantly enhanced Curie temperature (TC) of 614 K is reached in the present ε-Fe3N@C nanoparticles, which is much higher than the TC values in the previously reported ε-Fe3Nx.