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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NbO_2而是用液态Nb_2O_5热力学分析证明,铁液中的[Nb]可以将Nb_2O_5还原为NbO_2,而在铁液中有足够量[Nb]的条件下,[Mn]将不参加还原Nb_2O_5的反应而无MnO生成。因之,电池组装和前文相同,可写为: Mo|Mo,MoO_2|ZrO_2(MgO)|[Nb],NbO_2|Mo,Mo+ZrO_2金属陶瓷同样地根据下式:[Nb]+2[O]=NbO_2(s)由测得的α_O可计算α_(Nb)。实验证明,当[Nb]>1％时,[Mn]还原Nb_2O_5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Nb_2O_5已基本上在平衡条件下变成NbO_2。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Nb_2O_5,所得渣层成分复杂,形成MnO-Nb_2O_5-NbO_2的熔体,而NbO_2及MnNb_2O_6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MnNb_2O_6的生成自由能为: Mn_((1))+Nb_((s))+3O_2=MnNb_2O_(6(s));△G°=-367000+13.3T,卡 MnO_((s))+Nb_2O_(5(1))=MnNb_2O_(6(5));△G°=156000-93.2T,卡对渣层进行X射线结构分析,发现有MnNb_2O_6,Nb_2O_5,NbO_2及一些FeNb_2O_6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NbO_2。
In the foregoing, the authors have studied the self-activity interaction coefficient e Nb (Nb) of Nb in Nb-containing molten iron using a solid electrolyte constant oxygen cell. This article is the continuation of the study on the thermodynamic behavior of Nb in molten iron, and aims to find the effect of Mn on the activity coefficient of Nb. In this paper, using the same experimental methods and equipment, in the 1853K and 1873K two temperature experiments. Unlike the above, the slag layer does not use solid-state NbO 2 but liquid-phase Nb 2 O 5 thermodynamics analysis shows that [Nb] in the molten iron can reduce Nb 2 O 5 to NbO 2, whereas in the case of a sufficient amount of [Nb] Will not participate in the reaction of reducing Nb 2 O 5 without MnO formation. Therefore, the cell assembly is the same as the previous one and can be written as follows: Mo | Mo, MoO 2 | ZrO 2 (MgO) | [Nb], NbO 2 | Mo, Mo + ZrO 2 cermet is similarly based on the following formula: [Nb] +2 [O ] = NbO 2 (s) α_ (Nb) can be calculated from the measured α_O. Experiments show that when [Nb]> 1%, [Mn] reduction of Nb 2 O 5 reaction can be basically inhibited. X-ray structural analysis of the slag layer confirmed that Nb 2 O 5 has been changed to NbO 2 substantially at equilibrium. According to the above data of Fe-Nb binary system, f Nb (Nb) was calculated by the same concentration method and the same activity method. For the two graphs of lgf_ (Nb) ~ (Mn) versus [% Mn] at two temperatures, the two methods yielded essentially consistent results: 1853 K, e Bb Mn = 0.18; 1873 K e_ Bn) ~ (Mn) = 0.11. The temperature relationship can be expressed as follows: e Bb Mn = 12100 / T-6.35 When [% Nb] is less than 0.5 in molten iron, [Mn] can reduce Nb 2 O 5, Complex, forming a melt of MnO-Nb 2 O 5 -NbO 2, while NbO 2 and MnNb 2 O 6 may appear as a saturated phase, causing the slag layer to become a viscous two-phase body. The free energy of formation of MnNb_2O_6 was estimated by data processing as Mn_ (1) + Nb_ (s) + 3O_2 = MnNb_2O_ (6 (s)), ΔG ° = -367000 + 13.3T, (5 (1)) = MnNb_2O_ (6 (5)); △ G = 156000-93.2T, X-ray structure analysis of the slag layer showed that MnNb_2O_6, Nb_2O_5, NbO_2 and some FeNb_2O_6 were present . In the future, when the amount of [Nb] Fe-Mn-Nb ternary system is studied, the solid state NbO 2 is the best slag layer.