Roswell John Ruka

Role of Crystal Orientation in the Oxidation of Iron

The interface between a metal and its oxide or other corrosion films is a zone of great interest in the general phenomena of protection of metals. The system of iron and its oxides is considered in this work. Experiments are made using the electron diffraction high temperature camera on the oxidation of single crystals of iron. Definite orientation effects are found between the metal and the oxide if the oxidation is carried out slowly, for example, in a 50 per cent ‐50 per cent mixture at 750°C or in high vacuum. Rapid oxidation shows that the original orientation effects are not carried through to thick films.The orientation effects are interpreted in terms of two principles: (a) the conservation of similar repeat distances in the two lattices and (b) conservation of atom density. The effect of the forward and reverse solid phase reaction is studied and it is shown that the orientation effects are carried through to the newly formed oxide. The results are discussed in their relationships to the general phenomena of oxidation and corrosion.

Kinetics of solid phase reactions in oxide films on iron — The reversible transformation at or near 570°C

The forward and reverse reactions, Fe3O4 + Fe ⇄ 4FeO, are studied by electron diffraction methods. In thin films the forward reaction occurs at temperatures 170°C below the equilibrium value. The mechanism of the forward reaction is shown to be governed by the diffusion of iron. Studies on the reverse reaction as a function of time, temperature, and oxide composition indicate a nucleation and a growth process is rate controlling.

Direct utilization of hydrocarbon fuels in high temperature solid oxide electrolyte fuel cells

Utilization of hydrocarbon fuels such as methane and bottled natural gas has been successfully demonstrated in the operation of high-temperature solid oxide electrolyte fuel cells. Previous experimental work is reviewed, and the operation of air tubular fuel cells containing yttria-stabilized-zirconia solid electrolyte at 1000 degrees C and 250 mA/cm/sup 2/ current density, maintaining fuel and oxidant utilizations of 85% and 25%, respectively, is reported. Stable cell voltages and hydrocarbon reformation profiles along the cell length were obtained during the cell tests.<<ETX>>