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CO—CO_2混合气与Fe—Nb—C熔体和NbO_2(s)的平衡实验是在Al_2O_3或ZrO_2坩埚中进行的。实验表明,在1073～1273K间的低温下产生碳沉积是不可避免的。熔体上方的气相氧分压用固体电解质电池测定。与熔体中Nb成平衡的氧化物被确定为NbO_2(s)。测得1823K时反应[Nb]+O_2=NbO_2(s)的平衡常数K=6.31×10~(10),因此,可得反应的标准自由能: ΔG°=-377150(J/mol)求出了碳对Nb和Nb对碳的活度相互作用系数为: e~C_(Nb)=-0.74;e~(Nb)_C=-0.092
The equilibrium experiment of CO-CO 2 mixture with Fe-Nb-C melt and NbO 2 (s) was carried out in Al 2 O 3 or ZrO 2 crucible. Experiments show that in the 1073 ~ 1273K low temperature carbon deposition is inevitable. The gas phase oxygen partial pressure above the melt was measured with a solid electrolyte battery. The oxide that is in equilibrium with Nb in the melt is identified as NbO 2 (s). The equilibrium constant of reaction [Nb] + O 2 = NbO 2 (s) is found to be 6.31 × 10 ~ (10) at 1823K. Therefore, the standard free energy of the reaction can be obtained as ΔG ° = -377150 (J / mol) The activity coefficients of carbon for Nb and Nb on carbon are as follows: e ~ C_ (Nb) = - 0.74; e ~ (Nb) _C = -0.092