Mechanochemical synthesis of bimetallic FeNi and CoNi nano-alloys at room temperature

Abstract

The bimetallic CoNi (S1) and FeNi (S2) nano-alloys were synthesized by chemical co-reduction of theirs MCl2 (M = FeII, CoII and NiII) salts by aluminum nanoparticles in an acidic solid-state reaction at room temperature. The products were characterized by Fourier transform infrared spectroscopy (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy-dispersive X-ray (EDX), and vibrating sample magnetometer (VSM). The X-ray diffraction patterns of products S1 and S2 revealed the presence of intermetallic, metallic, and unreacted aluminum phases. The products weight fractions were calculated using Rietveld refinement. Quantitative XRD analysis of S1 shows a weight fraction of CoNi 58.58 wt%, Co 6.04 wt%, Ni 30.14 wt% and unreacted aluminum 5.23 wt%. Whereas, calculation in S2 shows weight fraction FeNi, Fe, Ni and unreacted aluminum 22.87, 44.20, 18.16 and 14.77 wt% respectively. The weight fraction of the interme- tallic CoNi phase is more than the intermetallic FeNi phase which is associated with Hum-Ruhter rules for the alloy formation, such as electronegativity, as explained in the Van Arkel-Ketelaar triangle. FESEM image of S1 and S2 show particles size distribution in the region 40–140 nm and 30–130 nm respectively. The hysteresis loop of S1 and S2 show magnetic saturation 88.374 emu/g and 61.298 emu/g respectively.