Kinetics of the oxidation of iron carbide dispersed in a carbon matrix with water vapor.

The reaction of iron carbide embedded in a carbon matrix with water vapor was studied in the temperature range 300-500 degrees C and the partial pressure of water vapor p(H(2)O) = 0.63-3.26 kPa. At these conditions the superfine magnetite and hematite are the products of this reaction. High oxidation temperature and low partial pressure of water vapor are favorable conditions to obtain only magnetite phase dispersed in a carbon matrix. The oxidation rate of iron and iron carbide is the same for both of them in the initial, kinetic stage of the reaction. It was observed that carbon deposit caused an increase in the reaction rate as a result of spillover effect. The oxidation rate of iron carbide distributed in a carbon matrix increases linearly with the carburization degree of the sample. The reaction rate is also linearly dependent on the partial pressure of water vapor. The apparent activation energy was determined as 110 kJ/mol.