Reduction of nickel oxide by carbon: I. Interaction between nickel oxide and pyrolytic graphite

The interaction of micron-sized particles of nickel oxide with pieces of stress-recrystallized pyrolytic graphite has been studied between 950 and 1000 degrees C using optical and scanning electron microscopy. The gases evolved (CO and CO2) upon reduction of NiO to nickel were continuously pumped out of the system in most of the runs. Examination of the cleavage (basal) surface and prismatic (edge) surface of the pyrolytic graphite after reaction reveals considerable mobility of selected oxide particles, creating shallow channels and pits on the graphite surface. Attack at the prismatic surface is more general and rapid than at the cleavage surface. Periodic examination of the cleavage surface during reaction revealed that many particles do not show any mobility or reaction, suggesting that reaction takes place only at active sites. Copyright (C) 1996 Elsevier Science Ltd.