Akio Yamaguchi1 and Joichiro Moriyama1
1Department of Metallurgy, Faculty of Engineering University of Kyoto, Kyoto
The H2 reduction of single crystals (<80 mesh) of NiO were studied for the purpose of investigating the reaction kinetics and detecting the dependence of reduction rate over the temperature range (220° ∼ 290°C) by means of Delmon's interruption method. The time dependence of reduction can be described by the equation 1-(1-x)1/3=kt, where x is fraction of reduction, t is time, k is rate constant and k was found to be approximately in inverse proportion to particle radii. In view of the above result, it seemed most reasonable to assume that the reduction of each particle started independently with a same probability and then proceeded identically. From the experiment of the annealed NiO single crystals the lack of uniformity in crystals was considered to influence the accelaration of the reduction rate. The value of activation energies of reduction (30.0 kcal/mol) of single crystales (325 ∼ 400 mesh) agreed approximately with those of NiO powder prepared from carbonate, hydroxide and nitrate (31.2, 30.5 and 31.6 kcal/mol, respectively).
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