PREPARATION OF NI POWDER BY MECHANOCHEMICAL PROCESS

A solid state displacement reaction between NiCl2 and Mg, induced by m echanical milling, has been employed for the production of fine nickel powder. The reaction ignites after a definite incubation period, lead ing to a sharp temperature rise of the vial. The observed overall temp erature rise during milling is due to two effects (i) mechanical worki ng, and (ii) chemical reaction. Ignition has been shown to occur as a result of a critical combination of chemical mixing, lattice strain an d milling induced temperature rise. This is related to the incubation time observed after a room temperature hold. The reaction product (NiMgCl2) has been leached with dilute HCl to obtain nickel powder which is in the size range of 10-500 nm. (C) 1997 Elsevier Science S.A.