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 tran smission electron microscopy, X-ray diffraction and differential scann ing calorimetry. The time evolution of the reaction is similar in the two samples, although slower in Ni80B20. Reaction begins with the form ation of o-Ni3B and of a disordered phase. The final products are nano crystalline o-Ni3B and unreacted nickel in Ni80B20 and nanocrystalline t-Ni2B in Ni60B40. Different milling conditions, tested on the Ni60B4 0 sample, do not modify the path but affect the rate of the solid stat e reaction.