Preparation and magnetic properties of single phase Ni2Si by reverse Rochow reaction

Abstract

Single phase Ni₂Si nanoparticles (NPs) have been successfully synthesized by using the Rochow reverse reaction, in which organosilanes ((CH₃)_nSiCl_4−n) are used as the silicon source. The results demonstrate that the crystalline size and phase of nickel silicide can be controlled through changing the organosilanes and reaction time. A formation mechanism of Ni₂Si NPs has been proposed, which involved reaction deposition and subsequently diffusion of Si atoms. Magnetism performance tests indicate that the saturation magnetization and coercive field of Ni₂Si NPs depend greatly on the environmental temperature and particle size. The blocking temperature (T_B) of the materials was found to strongly depend on selecting the organosilanes precursor:  in the case of the Ni₂Si-0 (148 K) and Ni₂Si-2 (336 K). This novel methodology opens a route to prepare other classes of metal silicides with single phase and stoichiometry. The as-prepared single phase Ni₂Si nanoparticles can find applications in ferrofluids, imaging, and magnetic separation due to its special magnetic behavior depending on the applied temperature (below or above T_B).