Cr Volatilization from Cr₂O₃ Exposed to Ar-20%CO₂ and Ar-20%CO₂–40%H₂O at 600–800 °C

Chromium volatilization from the surface of Cr 2 O 3 pellets was investigated in the atmospheres containing Ar–20%CO 2 and Ar–20%CO 2 –40%H 2 O at 600–800 °C. The measured fluxes of Cr-loss were 3–6 orders of magnitude higher than the fluxes calculated based on the conventional reaction: 1/2Cr 2 O 3(s) + 3/4O 2(g) + H 2 O (g) = CrO 2 (OH) 2(g) considering both the case that O 2 and H 2 O were from impurities and thermal decomposition of CO 2 and H 2 O at equilibrium. As CrO 3 was detected on the surface of Cr 2 O 3 pellets after exposure to CO 2 -containing environments, the possible mechanism to explain chromium volatilization phenomena is proposed as chromium volatile matters should mainly be generated from the reaction between Cr 2 O 3 and CO 2 producing CrO 3 on the surface of Cr 2 O 3 . The CrO 3 may directly volatilize as the volatile phase of CrO 3 in dry conditions or consecutively react with H 2 O to produce CrO 2 (OH) 2 in humidified conditions.