Size dependence of magnetic properties of Fe, Co and Ni nanoparticles prepared by the chemical-metallurgical method using surfactants

Abstract

The present study focuses on the synthesis of Fe, Co and Ni nanoparticles (NPs) by the chemical-metallurgical method with surfactant additives at the precipitation stage. The effect of surfactant additives on the dispersion, morphology and magnetic properties of the Fe, Co and Ni NPs was studied. The size characteristics of the NPs were measured by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and the Brunauer–Emmett–Teller method. Sodium dodecyl sulfate (SDS) and ethylenediaminetetraacetic acid disodium salt (EDTA) were used as surfactants in this study. Application of SDS and EDTA amounting to 0.1 wt% yielded an increase of 1.5–3 times the specific surface area of the reduced NPs. No surfactant traces were found in the reduced samples according to energy dispersive X-ray analysis. The mechanism of surfactant action is proposed. The surfactants reduce the critical radius of hydroxide clusters and prevent their growth and coagulation. The use of more dispersed hydroxides as precursors leads to the formation of NPs with a smaller particle size. The NPs with a diameter close to the critical size of the single-domain state for each material were obtained due to application of the surfactants. It was found that the saturation magnetization values of the Fe, Co and Ni NPs synthesized using surfactants are close to the values of micron-sized samples. This makes them suitable for many applications in mechanical engineering and technological industries.