MECHANICALLY ACTIVATED REDUCTION OF NICKEL-OXIDE WITH GRAPHITE

The reduction of nickel oxide with graphite during ball milling at bot h ambient and elevated temperatures was investigated using X-ray diffr action (XRD), simultaneous thermogravimetry and differential thermal a nalysis (TG/DTA), and electron microscopy. It was found that milling a t ambient temperature did not result in the reduction of nickel oxide to nickel, However, milling significantly reduced the critical reactio n temperature for the reduction, from 1350 K for the unmilled sample t o similar to 650 K for samples milled for 12 hours or longer. This red uction in reaction temperature is rationalized in terms of the microst ructural refinement observed in the milled samples. The reduction of n ickel oxide to nickel was observed to occur at elevated temperatures d uring milling. The thermodynamics and kinetics of the reduction reacti on are discussed.