Experimental and statistical optimization of the hydrogen reduction process of nickel oxide

Reduction of nickel oxide (NiO) by hydrogen gas is an affordable and simple way in comparison with the other chemical methods to produce and retrieve the pure nickel powder. Properties of the reduced Ni powder are dependent on many parameters such as the temperature, holding time, and hydrogen gas flow. The main reported mechanism of hydrogen reduction contains the decomposition of the oxide into gas-state phases and then condensation of the product supersaturated vapor. In the present work, experimental investigation and statistical optimization of these effective parameters on the nickel oxide hydrogen reduction were performed according to Taguchi’s experimental design and related statistical analyses. The produced powder was characterized by oxygen elemental analyses, scanning electron microscopy, and X-ray diffraction. The results showed that the temperature affects the reduction rate of nickel oxide to a significant extent, and the optimized conditions for desirable powder reduction and morphology were determined as 900°C of temperature, 60 min for holding time, and 300 cc/min of gas flow. Finally, a regression equation was derived based on the experimental results, which can predict the reduction rate for each combination of the parameters in the studied range.