Investigation of nickel product structures developed during the gaseous reduction of solid nickel oxide

The product microstructures developed during the reduction of dense synthetic nickel oxide in H-2-N-2 and H-2-H2O mixtures between 300 A degrees C and 1000 A degrees C are reported. A number of distinctly different types of nickel product structures have been identified, namely, coarse fibrous nickel with fissures, fine porous nickel-planar interface, large porous nickel-irregular interface, and dense nickel layer. The influences of gas composition and temperature on the conditions for formation of these microstructures, and their evolution with temperature and time, have been systematically investigated. The condition for formation of the various microstructure types was summarized on morphology maps as functions of reducing gas partial pressure, thermodynamic driving force, and reaction temperature