REDUCTION OF NICKEL-OXIDE BY CARBON .1. 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 9 50 and 1000 degrees C using optical and scanning electron microscopy. The gases evolved (CO and CO2) upon reduction of NiO to nickel were co ntinuously pumped out of the system in most of the runs. Examination o f the cleavage (basal) surface and prismatic (edge) surface of the pyr olytic graphite after reaction reveals considerable mobility of select ed oxide particles, creating shallow channels and pits on the graphite surface. Attack at the prismatic surface is more general and rapid th an at the cleavage surface. Periodic examination of the cleavage surfa ce during reaction revealed that many particles do not show any mobili ty or reaction, suggesting that reaction takes place only at active si tes. Copyright (C) 1996 Elsevier Science Ltd.