The Mechanical Properties of Nickel Oxide and Their Relationship to the Morphology of Thick Oxide Scales Formed on Nickel.

摘要

The oxidation of metals that form P-type semiconducting oxide scales,such as NiO on nickel and CoO on cobalt,takes place by outward cation diffusion and inward vacancy diffusion. The large number of cation vacancies precipitate in the scale near the oxide-metal interface and many coalesce to form macroscopic pores,resulting in a transition from a dense,columnar scale to a duplex scale which contains an inner,fine-grain equiaxed,porous layer. Increasing temperature and/or purity eliminate the transition,which has been found to depend upon oxide plasticity. The mechanical properties of bulk nickel oxides having a range of porosities have been studied in compression. The development of the duplex structure in scales during oxidation has been shown to depend upon inhibition of slip. Grain size,porosity,and impurities play an important role;all of these effects are discussed in detail. (Author)