Preparation of Ni1 − xFex nanoparticles with a composition gradient and a proposed formation mechanism

Abstract

Ni-Fe alloy nanoparticles were able to be prepared by a one-step hydrazine reduction, where the formation mechanism is unclear. In this paper, Ni1xFex nanoparticles with a composition gradient were prepared, and the change in composition gradient in the Ni1 − xFex nanoparticles was found to be affected by Fe content. Furthermore, it was surprising that the increase in Fe content significantly increased the formation rate of Ni1 − xFex nanoparticles, which was difficult to explain via thermodynamics. By further analyzing the element distribution and microstructure of the intermediate products of the Ni1 − xFex nanoparticles, a formation mechanism was proposed for the Ni1 − xFex nanoparticles. In this formation mechanism, Ni1 − xFex(OH)2 was confirmed as the reduced intermediate, and the composition distribution of the Ni1 − xFex nanoparticles was primarily controlled by reaction kinetics. Finally, the existence of the composition gradient in the Ni1 − xFex nanoparticles had a great effect on their coercivity, due to the change in internal stress. This work provides a reference for preparation and a performance study of alloy nanoparticles with a composition gradient.