Volatilization kinetics of chromium oxide, manganese oxide, and manganese chromium spinel at high temperatures in environments containing water vapor

Performance degradation of solid oxide fuel cells due to chromium volatilization is a well-investigated issue in the literature. Therefore, retention coatings were developed to distinctly reduce the chromium volatilization. One approach was by alloying with manganese to ferritic steels to form manganese chromium spinel which is reported to decrease chromium volatilization by 61-75%. In the present paper, the volatilization rates of pure manganese chromium spinel ceramics were examined as well as those of the two oxides forming this spinel-pure chromium oxide and pure manganese oxide-in synthetic air containing 10% water vapor (high p(O-2)) and argon/hydrogen containing 10% water vapor (low p(O-2)) at 850 degrees C, 950 degrees C, and 1,050 degrees C. Chromium oxide showed higher volatilization rates in high p(O-2), whereas manganese oxide demonstrated higher volatilization rates in low p(O-2). Contradictory to the literature, manganese chromium spinel displayed the highest volatilization rates in both atmospheres and nonlinear kinetics behavior. This deviation from linear behavior can be attributed to diffusion-controlled volatilization in high p(O-2).