Iron-Nickel Alloy with Starfish-like Shape and Its Unique Magnetic Properties: Effect of Reaction Volume and Metal Concentration on the Synthesized Alloy

Abstract

Iron-nickel alloy is an example of bimetallic nanostructures magnetic alloy, which receives intensive and significant attention in recent years due to its desirable superior ferromagnetic and mechanical characteristics. In this work, a unique starfish-like shape of an iron-nickel alloy with unique magnetic properties was presented using a simple, effective, high purity, and low-cost chemical reduction. There is no report on the synthesis of such novel shape without complex precursors and/or surfactants that increase production costs and introduce impurities, so far. The synthesis of five magnetic iron-nickel alloys with varying iron to nickel molar ratios (10–50% Fe) was undertaken by simultaneously reducing Fe(II) and Ni(II) solution using hydrazine hydrate as a reducing agent in strong alkaline media for 15 min at 95–98 °C. The effect of reaction volume and total metal concentration on the properties of the synthesized alloys was studied. Alloy morphology, chemical composition, crystal structure, thermal stability, and magnetic properties of synthesized iron-nickel alloys were characterized by means of SEM, TEM, EDX, XRD, DSC and VSM. ImageJ software was used to calculate the size of the synthesized alloys. A deviation from Vegard’s law was recorded for iron molar ration higher than 30%., in which superstructure phase of FeNi3 was formed and the presence of defects in it, as well as the dimensional effects of nanocrystals. The saturation magnetization (Ms), coercivity (Hc), retentivity (Mr), and squareness are strongly affected by the molar ratio of iron and nickel and reaction volume as well as the total metal concentration.

Dynamic Tracking of NiFe Smart Catalysts using In Situ X-Ray Absorption Spectroscopy for the Dry Methane Reforming Reaction

“…The EXAFS modeling (shown in Figures S6b and S7b, Tables S1 and S2) also results in about 1% lattice expansion for the reduced state perovskite, at both Fe and Ni K-edges, compared to the pure Ni metal. The overall expansion of the crystal lattice observed for the reduced state is in good agreement with the literature that reports a larger lattice constant (3.57–3.59 Å) for FeNi alloy than that of pure Ni metal (3.52 Å). − Another significant observation from the reduced state XAS data is that neither the Ni nor Fe K-edge data show the remnants of the perovskite phase, indicating that most of the Fe and Ni exsolve out of the parent perovskite structure to form FeNi alloy. This differs from the XRD (Figure ) and STEM-HAADF images (Figure b,f), where some residual Fe is still in the lattice in the form of LaFeO 3 .…”