The role of oxide grain boundary character distribution in nickel oxidation kinetics

Oxidation rate on Ni (100) single crystal substrate is over one order of magnitude faster than that on Ni (111). In order to understand this difference in the oxidation rate, the Grain Boundary Character Distribution (GBCD) in the oxide formed on two substrates has been calculated. GBCD is a major factor that affects the diffusion of Ni ion along oxide grain boundaries. It is found that the probability of the existence of Sigma3 grain boundary in the oxide formed at the early stage of oxidation on (111) substrate is much higher than that that on (100) substrate due to the lattice matching between the oxide and substrate. The difference between the oxide GBCDs is used to simulate the oxidation processes on two different substrates. Good agreement between the simulated and experimental results is obtained.