Crystal structure, microstructure and magnetic properties of Ni nanoparticles elaborated by hydrothermal route

Abstract

We report on the crystal structure, microstructure and magnetic properties of Ni nanoparticles (NPs), with an average diameter of around 40nm, produced by hydrothermal method. A series of Ni powders was synthesized at relatively low temperature (140°C) by varying the NaOH concentration. The crystal structure, microstructure and magnetic properties were investigated by means of XRD, MEB coupled to EDX and VSM magnetometry. The XRD patterns show Bragg reflections corresponding to Ni with face centred cubic (fcc) crystal structure. EDX spectra confirm the purity of Ni powders. Moreover, the SEM micrographs show that the Ni-NPs are agglomerated forming entities of 1–5μm in average size with different morphologies that change as the NaOH concentration increases. While those entities exhibit a flower-like form at the lowest concentration, a dendritic shape appears for the highest one. The room temperature values for the coercive field (<200Oe) and saturation magnetization (≈52Am2/kg) were obtained from the magnetic hysteresis loops. We discuss about the influence of the particle morphology on the magnetic behaviour.