【作者】 杨勇；

【导师】 李保卫； 张邦文；

【作者基本信息】 内蒙古科技大学 ， 材料学， 2009， 硕士

【摘要】 铌是我国比较紧缺的稀有金属之一,我国的铌资源80%储存在包头白云鄂博矿,且主要以铌铁矿、铌铁金红石、易解石等形式存在。铌铁矿（FeNb₂O₆）作为铌精矿的主要矿物,具有很高的经济价值。本文人工合成纯铌铁矿,然后对铌铁矿进行碳热还原,对还原热力学进行了理论分析。采用等温和非等温TG-DSC结合XRD研究了还原反应过程,深入的探讨了铌铁矿还原的动力学机理。热力学分析表明,铌氧化物的还原顺序为Nb₂O₅到NbO₂,NbO₂到NbO,NbO到NbC,NbC到Nb。等温热重分析得到了主体还原过程的表观活化能E=515.2KJ/mol,还原反应的速率常数k与温度T的关系为lnk=36-61995/T,反应的动力学方程为[（1-α）-1/3-1]2= kt,为三维扩散Z-L-T方程,表明气体CO在产物层中过的内扩散为整个反应的限制性环节。对非等温热分析及XRD分析表明,FeNb₂O₆碳热还原分两步进行:在1100-1240℃,FeNb₂O₆首先被还原为金属Fe和NbO₂,该步骤E=264.4KJ/mol,lnk=17.6-31799/T,反应的动力学方程为α+（1-α）ln（1-α）=kt;在1250-1350℃,第一步的还原产物NbO₂被还原为NbC,该步骤E=482.7KJ/mol,lnk=17.6-31799/T,反应的动力学方程为[（1-α）^-1/3-1]²=kt,与等温法得到的结果一致。非等温热分析法能得到整个还原过程的动力学参数。更多还原

【Abstract】 Niobium is one of rare metal in short on market in China. Niobium resource with 80% through China is deposited in Baiyunebo Ore, and the minerals concerned are niobite, fersmite and ilmenorutile. Niobite （FeNb₂O₆）, usually the main phase composition in niobium concentrate, is of high value in economy. In present paper, pure niobite was synthesized in our laboratory, then subjected to carbothermic reduction. The reaction thermodynamics was analyzed, and the kinetics was investigated using isothermal and non-isothermal thermogravimetry and XRD techniques, the underlying mechanism was discussed.Thermodynamics study indicates that niobium oxide is reduced stage by stage, following the sequence of Nb₂O₅ to NbO₂, then to NbO, and to NbC finally.According to isothermal thermogravimetry for overall-range reduction reaction, the activation energy E=515.2 KJ/mol, the rate constant of reaction k is correlated with temperature T by the relationship lnk=36-61995/T, and the reaction kinetics follows the ZLT 3-D diffusion equation [（1-α）^-1/3-1]²= kt, whereαdenotes loss-in-weight rate. It indicates that CO gas diffusion cross the reaction product layer is the controlling step in carbothermic reduction of FeNb₂O₆.The combining of non-isothermal thermogravimetry with XRD techniques shows FeNb₂O₆ reduction consists of two stages: the first is at the temperature range of 1100-1240℃, FeNb₂O₆ is reduced by CO gass to Fe and NbO₂, the kinetics can be characterized by E=264.4KJ/mol, lnk=17.6-31799/T, andα+（1-α）ln（1-α）=kt. The second occurs at T=1250-1350℃, the first-stage product NbO₂ is reduced to NbC, correspondingly, E=482.7KJ/mol, lnk=17.6-31799/T, [（1-α）^-1/3-1]²=kt, in accord with the results obtained by isothermal thermogravimetry.更多还原