Synthesis of Fe-Ni invar alloy nanopowder by the electrical explosion of wire in the liquid

The present work studied the synthesis of Fe–Ni Invar alloy nanopowder by the electrical explosion of wire (EEW) in deionized water. X-ray diffraction (XRD) was used to investigate the phase of the nanopowder. It indicated that the as-synthesized nanopowder had γ-Fe–Ni solid solution and FeO phase. Pure γ-Fe–Ni phase was obtained when the as-synthesized powder was reduced under the hydrogen at 700 °C for 30 min. Particle sizes of the as-synthesized and the reduced powders were observed by electron transmission microscope. The as-synthesized and the reduced nanopowders were in a nearly spherical shape with average size of 32.5 and 180 nm, respectively. The as-synthesized particles had a core–shell structure that was composed of γ-Fe–Ni in the core and FeO in the shell. The alloy compositions of the wire before exploding and the reduced nanopowder determined by electron probe microanalysis were almost the same. The hysteresis loop of the as-synthesized nanopowder, the hydrogen-reduced nanopowder and the sintered sample were examined with a vibrating sample magnetometer. The sintered sample had the smallest coercivity with a value of 14.26 Oe.