This paper describes the reduction of nickel oxide under different gas mixture. The influence of gas mixture on phase, density, morphology and pore size of reduced nickel oxide were studied. Nickel oxide pellets sintered at 1400⁰C were reduced under various hydrogen-nitrogen gas mixtures, namely 40% H₂-60% N₂, 60% H₂-40% N₂, 80% H₂-20% N₂. Phase identification, density measurement and observation of morphology were conducted on samples before and after reduction process. Under all gas mixtures, nickel oxide was completely reduced to nickel. Density of the samples decreased in the range of 21% to 32% depends on H₂ percentage used. Results from the density shows that the higher the H₂ gas concentration, the smaller the density changes. Significant change in porosity of the sample before and after reduction was observed. Size of pore after reduction determined by H₂ concentration used during reduction where the higher the H₂ concentration resulted in large pore size.
