Reduction of nickel oxide by carbon: II. Interaction between nickel oxide and natural graphite

The interaction of micron-sized particles of NiO with plate-like particles of natural graphite has been studied at 950 degrees C using scanning electron microscopy. The gases evolved (CO and CO2) upon reduction of NiO to Ni were continuously pumped out of the system. The graphite particles consisted of highly aligned, large crystallites. Attack occurred predominantly at the edge of prismatic surface of the particles, which constituted only 4-5% of the total surface area. Nickel produced in the reduction reaction covered the NiO with a sintered layer. Removal of the Ni layer revealed unsintered particles of NiO of similar shape to the original particles. The particles showed considerable porosity, presumably a result of selective attack at cracks in the NiO produced as reaction proceeds. (C) 1997 Elsevier Science Ltd.