Properties of Nanocrystalline Fe-Ni Particles Prepared by Thermal Reduction of Oxalate Precursors

Abstract

Recent technological advancements require development of cost-effective and high-performance magnets which ideally do not contain rare earth metals or noble metals. The promising candidates are Fe-Ni-based alloys, in particular, the Fe50Ni50 L10 phase (tetrataenite), which has a great perspective for producing hard magnetic materials. Our study explores a promising method for preparing nanoparticles of Fe-Ni alloy from an iron-nickel oxalate precursor. The coprecipitation method was employed to prepare oxalate precursors, followed by controlled thermal decomposition in a reducing hydrogen atmosphere. The morphology and properties of the resulting particles were analysed using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Mössbauer spectroscopy (MS), and magnetic measurements.The SEM analysis revealed that the particles have approximately cube-shaped unit cell morphology with a size in a range of 1 -2 m. Upon annealing, the samples contain multiple phases with varying Fe-Ni content. Magnetic measurements confirmed the formation of magnetically suitable Fe-Ni phases in the samples after annealing. Mössbauer spectroscopy emerged as a highly effective method for characterizing individual phases of the Fe-Ni system.