【摘要】 在前文内,作者曾利用固体电解质定氧电池对含Nb铁液中Nb的自身活度相互作用系数e_Nb^Nb进行了研究。本文是铁液中Nb的热力学行为研究的继续,旨在求出其中Mn对Nb活度系数的影响。本文利用前文同一实验方法及设备,在1853K及1873K两个温度进行实验。和前文不同,渣层不用固态NbO₂而是用液态Nb₂O₅热力学分析证明,铁液中的[Nb]可以将Nb₂O₅还原为NbO₂,而在铁液中有足够量[Nb]的条件下,[Mn]将不参加还原Nb₂O₅的反应而无MnO生成。因之,电池组装和前文相同,可写为: Mo|Mo,MoO₂|ZrO₂（MgO）|[Nb],NbO₂|Mo,Mo+ZrO₂金属陶瓷同样地根据下式:[Nb]+2[O]=NbO₂（s）由测得的α_O可计算α_Nb。实验证明,当[Nb]>1％时,[Mn]还原Nb₂O₅的反应即可基本上被抑制。对渣层进行X射线结构分析证实Nb₂O₅已基本上在平衡条件下变成NbO₂。根据前文的Fe-Nb二元系的资料,利用同一浓度法及同一活度法计算出f_Nb^Nb。作两个温度的lgf_Nb^Mn对[％Mn]的直线图,两种方法得出基本上一致的结果:1853K,e_Bb^Mn=0.18;1873K,e_Bn^Mn=0.11。其温度关系式可大体上由下式表达:e_Bb^Mn=12100/T-6.35 当铁液中[％Nb]小于0.5时,[Mn]就能还原Nb₂O₅,所得渣层成分复杂,形成MnO-Nb₂O₅-NbO₂的熔体,而NbO₂及MnNb₂O₆可能以饱和相出现,使渣层成为粘滞的二相体。经数据处理估计出MnNb₂O₆的生成自由能为: Mn_（1）+Nb_（s）+3O₂=MnNb₂O_6（s）;△G°=-367000+13.3T,卡 MnO_（s）+Nb₂O_5（1）=MnNb₂O_6（5）;△G°=156000-93.2T,卡对渣层进行X射线结构分析,发现有MnNb₂O₆,Nb₂O₅,NbO₂及一些FeNb₂O₆存在。今后进行低[Nb]量的Fe-Mn-Nb三元系研究时,最好渣层采用固态NbO₂。更多还原

【Abstract】 In the previous paper written by the present authors, an investigation on the self interaction coefficient of the activity of Nb in molten iron with the solid electrolyte oxygen cell technique was reported. This paper is a continuation of the same research on the study of the thermodynamic behaviour of Nb in iron melt, the effect of Mn upon the activity coefficient of Nb being studied at 1853 K and 1873 K with the same experimental method and equipment. Instead of using solid NbO₂ as the slag layer over the iron melt, liquid Nb₂O₅ was used. Preliminary thermodynamic analysis has shown that [Nb] in the iron melt could reduce Nb₂O₅ into NbO₂, and in the presence of a certain fair amount of [Nb] in the iron melt, [Mn] in the iron melt would not take part in the reduction of Nb₂O_s and no MnO was formed, so that the cell assembly could be written similarly as in the previous paper as: Mo|Mo, MoO₂‖ZrO₂（MgO）‖[Nb], NbO₂|Mo, Mo+ZrO₂ cermet Henceforth, value of α_Nb could be calculated from values of α_o by the same reaction as before: [Nb]+2[O]=NbO_2（s）It was shown experimentally that an amount of [Nb] bigger than 1% would suffice to suppress the reduction of [Mn] upon Nb₂O₅ and prevent the formation of MnO. X-ray diffraction analysis of the slag layer confirmed that practically all Nb₂O₅ was converted into NbO₂ by [Nb] under equilibrium conditions, with data from the previous work for the binary Fe-Nb system, values of f_Nb^Mn for the ternary Fe-Nb-Mn system were calculated on the "same concentration" as well as the "same activity" basis, and these values, after treating lg f_Nb^Mn vs [%Mn] at the two different temperatures as a straight-line relation, led to practically identical results for e_Nb^Mn: 1853 K, e₍Nb_<sup>Mn=0.18, 1873K, e_Nb^Mn=0.11. Its relation with temperature might be roughly represented by: e_Nb^Mn=12100/T-6.35 When the [%Nb] content in the iron melt was small, say below 0.5%, it was found that [Mn] would react with Nb₂O₅ to form a slag layer of complicated composition of Nb₂O₅-NbO₂-MnO, probably saturated with NbO₂ and MnNb₂O₆, and forming a viscous two-phase melt. Evaluation of the experimental data gave estimated values of the free energy of formation of MnNb₂O₆ as follow: Mn_（1）+Nb_（s）+3O₂=MnNb₂O_6（s） △G°=-367000+13.3T, cal MnO_（s）+Nb₂O_5（1）=MnNb₂O_6（s） △G°=156000-93.2T, cal X-ray diffraction analysis of the complicated slag identified the presence of MnNb₂O₆, Nb₂O₅ and some FeNb₂O₆. It is to be recommended that it would be more preferable to use NbO₂ as the slag layer over the iron melt in case that the Fe-Nb-Mn system of rather small content of [Nb] is to he studied.更多还原