Nanoparticles of Ni carbide of about 50nm in diameter were synthesized by the reduction of Ni salt in a polyol solution in the presence of polyvinylpyrrolidone (PVP). It was found that the aggregation of nanoparticles was suppressed when PVP was added to the polyol solution during synthesis. Diffraction peaks of the fcc and hexagonal structures were observed for the specimen synthesized without PVP. On the other hand, no peaks assigned to the fcc structure and no spontaneous magnetization were observed for the specimen synthesized with 50 g/L PVP, although pure bulk Ni are fcc structure and ferromagnetic at room temperature. Additionally, small peaks were observed in the X-ray diffraction pattern at 2θ = 26.2, 35.7 and 47.8°, originated not from the impurity phase but from the hexagonal phase. The specimen synthesized with 50 g/L PVP was fundamentally identified as Ni carbide with a Ni 3C-type structure, as small peaks mentioned above were assigned to superlattice peaks. The structure parameters of the Ni carbide were refined by Rietveld analysis. It is concluded that the formation of the Ni carbide nanoparticles with Ni 3C-type structure in the polyol solution is enhanced by the addition of PVP.
- Nickel carbide