Strategy for Ultrafine Ni Fibers and Investigation of the Electromagnetic Characteristics

A simple and practical approach for synthesizing ultrafine Ni fibers under normal pressure via the reduction of Ni2+ ions by hydrazine hydrate in the absence of any templates or external magnetic field is reported. The mechanisms and a simplified model of formation for the Ni fibers are proposed, and the correlated magnetic properties and electromagnetic characteristics of the Ni products are studied systematically. The results of a series of comparative studies indicate that the feeding sequence of the reactants and the concentration of NaOH solution are critical to controlling the shape of the target products from fiber to sphere. The Ni fibers have an enhanced magnetic coercivity compared with that of the Ni spheres. The composites filled with Ni fibers have an electromagnetic wave absorbance within the frequency range 2.0-18.0 GHz stronger than that for the Ni sphere-filled composites. Specifically, by properly adjusting the matching thicknesses, a minimum reflection loss (RL) of -39.5 dB at 4.8 GHz and an absorbance band of less than -20 dB within 3-16 GHz are obtained for the Ni fiber-filled composites, showing that the Ni fibers may have promising application for electromagnetic wave absorbance.