STUDY OF THE KINETICS OF HYDROGEN REDUCTION OF NICKEL HYDROXIDE NANOPOWDERS UNDER ISOTHERMAL CONDITIONS

A study was conducted on the kinetics of obtaining metallic nickel nanopowder through the hydrogen reduction of nickel hydroxide (Ni(OH)2) under isothermal conditions. The initial Ni(OH)2 was obtained by chemical precipitation from aqueous solutions of nickel nitrate (Ni(NO3)2, 10 wt. %) and sodium hydroxide (NaOH, 10 wt. %) at room temperature and pH = 9, with continuous stirring of the reaction mixture. The hydrogen reduction process was carried out in a tubular furnace within a temperature range of 275–300 °C. It was found that the rate constant for nickel hydroxide reduction at 300 °C is approximately 1.86 times higher than at 275 °C. Accordingly, after 60 minutes of reduction, the degree of conversion at 300 °C is 1.4 times greater, indicating a significant effect of temperature on the reaction rate. The calculated activation energy of the process is about 68 kJ/mol, suggesting a kinetic-controlled reaction mechanism. It was shown that nickel nanoparticles synthesized by hydrogen reduction of nickel hydroxide nanopowders at 300 °C predominantly form flat flakes (average size ~96 nm) with significant agglomeration