Reactions between alumina, magnesia, spinel, beryllia, and graphite have been studied in vacuum by measuring the amount of carbon monoxide formed. Two types of reactions were observed: a diffusion‐controlled reaction with alumina, beryllia, and thoria, and a phase boundary‐controlled reaction with magnesia, beryllia, spinel, and titania. The following activation energies were obtained: 316 kcal for , 40 kcal for below 1700°C (parabolic rate law), 61.3 kcal for above 1700°C (linear rate law), 59.8 kcal for , 59.5 kcal for spinel, and 59 kcal for . The relative reactivities of these oxides with graphite increase in the following order: , spinel, , , , . For the reactions following a linear rate law a mechanism is proposed. It was concluded that the reaction proceeds over the gas phase by dissociation of the oxide into atomic oxygen and that the desorption of carbon monoxide from the graphite surface is the rate‐determining step.
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Komarek et al. (1963) studied this question.