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Abstract
The oxidation in air of porous nickel, iron, and copper specimens has been studied. It has been established that the kinetics of oxidation of porous bodies, as determined by weight-increment measurements, cannot be described by a quadratic equation.
The oxidation kinetics of porous metals depends upon the size and porosity of the specimens. These specific oxidation characteristics are associated with a change in the total surface area taking part in the reaction, caused by blocking of the pore outlets by the oxides formed. Oxidation of porous bodies is accompanied by the formation of oxides in both the surface and the interior of the specimen, and by an increase in the electrical resistance of the material.
It has been established that a spontaneous rise in the specimen temperature, caused by the heat of reaction, takes place during oxidation. Prolonged oxidation of porous bodies is accompanied by shrinkage due to sintering of the core of the specimen, in the case of nickel and copper, and by a volume increase in the case of iron.
Notes
* Manuscript received 20 May 1963. Contribution to a Symposium on “Residual Porosity in Powder Metallurgy” to be held in London on 21 and 22 October 1963.