Magnetic field assisted polyol synthesis of cobalt carbide and cobalt microwires

Abstract

Cobalt–cobalt carbide [CoxC (x = 2 or 3)] and cobalt (FCC-Co) microwires have been synthesized using a polyol method in the presence of a high external magnetic field of 4.3 kOe. It was reported before that the synthesis of these particles in the absence of magnetic field leads to the formation of spherical particles. Analysis of the X-ray diffraction (XRD) scans indicates that the synthesized CoxC wires consist of four phases’ α-Co, β-Co, Co3C, and Co2C. The percent composition of these phases was 53.3 % Co3C, 26.8 % Co2C, 12.5 % α-Co, and 7.4 % β-Co. XRD analysis of the as-synthesized cobalt wires shows that it consists of single-phase FCC-Co. Based on Scherrer analysis of the XRD data, the average crystallite sizes of the cobalt carbide and the cobalt particles are 18.5 and 16.3 nm, respectively. Scanning electron microscopy (SEM) studies show that the diameter of CoxC wires is in the range of 1.6(±0.2) μm with their length varying between 18 and 30 μm while the diameter of the cobalt wires is 1.65(±0.1). The SEM results infer that the morphology of the growing particles was controlled by the magnetic field with the applied field directs the growth of the particles into wires. The magnetic measurements indicate a superparamagnetic character of the cobalt wires and a soft ferromagnetic nature of the synthesized CoxC chains. The degree and field range of the interactions between magnetic domains have been investigated using a Henkel plot.