The synthesis of nanocrystalline nickel boride powders by ball milling of elemental components

Solid state reaction induced by ball milling the elemental components has been investigated on Ni60B40 and Ni80B20 mixtures by means of transmission electron microscopy, X-ray diffraction and differential scanning calorimetry. The time evolution of the reaction is similar in the two samples, although slower in Ni80B20. Reaction begins with the formation of o-Ni3B and of a disordered phase. The final products are nanocrystalline o-Ni3B and unreacted nickel in Ni80B20 and nanocrystalline t-Ni2B in Ni60B40. Different milling conditions, tested on the Ni60B40 sample, do not modify the path but affect the rate of the solid state reaction.