Oxidation behavior of U₃Si (3.9 wt% Si) in air at 250-400°C

The oxidation of U₃Si was studied using a thermogravimetric analyzer and an XRD in the temperature range from 250 to 400°C in air. From XRD studies it was found that U₃Si converted to UO₂, U₂O₅ and Si after 200 h at temperatures up to 275°C and it converted to UO₂, U₃O₇, SiO and SiO₂ after 200 h at the temperature of 300°C. U₃O₈ began to be formed at the temperature of 325°C. The linear reaction rate was observed at lower temperatures up to 275°C in the experimental range of reaction time. For higher temperatures, however, the reaction rate was nearly linear at initial stage of reaction and more sharply increased after a certain time due to cracking, breaking and pulverizing in the specimen. The reaction was controlled by diffusion rather than chemical reaction kinetics. The averaged rate assuming a linear rate equation could be expressed with activation energies that were 122.29 kJ/mol and 69.65 kJ/mol the temperature ranges of 250 ≤ T(°C) ≤ 300 and 300 ≤ T(°C) ≤ 400 respectively.