Standard Gibbs Free Energy of Formation of MnO-saturated MnO Cr2O3 Solid Solution at 1873K.

Abstract

The standard Gibbs free energy of formation of MnO-saturated MnO.Cr 2 O 3 solid solution (stoichiometric MnO.Cr 2 O 3 ), which is one of important thermodynamic properties of the MnO-SiO 2 -CrO x inclusion system to clarify the equilibrium relation among molten stainless steel and the inclusions formed during the stainless steel Si-deoxidation process, was determined at 1 873 K. By equilibrating molten iron or copper with MnO-saturated MnO.Cr 2 O 3 crucible under controlled oxygen partial pressure, P O2 , the standard Gibbs free energy changes of the following reactions at 1 873 K were determined to be: Mn (mass%, in molten Fe)+2Cr (mass%, in molten Fe)+2O 2 (g) =MnO.Cr 2 O 3 (MnO-satd.): ΔG°/kJ=-755±4 (P O2 =2×10 -6 -6×10 -5 Pa) Mn (mass%, in molten Cu)+2Cr (mass%, in molten Cu)+2O 2 (g) =MnO.Cr 2 O 3 (MnO-satd.): ΔG°/kJ=-807±7 (P O2 =3×10 -5 -1.5×10 -4 Pa) Mn (I)+2 Cr (s)+2 O 2 (g)=MnO.Cr 2 O 3 (MnO-satd.): ΔG o f ,MnO.Cr 2 O 3 /kJ.mol -1 =-958±8 (PO 2 =2×10 -6 -1.5×10 -4 Pa) The values of ΔG° and ΔG° f ,MnO.Cr 2 O are independent of the oxygen partial pressure within the P O range in the present study.