目前钠还原氟钽酸钾制备的钽粉无法满足高端电容器对钽粉形态均匀性和氧含量的要求。本文利用镁还原氧化钽-酸洗工艺制备钽粉,采用X射线衍射仪、扫描电子显微镜、能谱仪、激光粒度仪、氧氮氢分析仪和电感耦合等离子体发射光谱仪等,研究还原产物酸洗前后的物相组成、微观形貌、元素含量,以及钽粉的粒度分布。结果表明：钽粉颗粒遗传了原料的形貌。当n(Mg)∶n(Ta2O5)=5∶1时,由于钽晶粒较细小且具有较高活性,部分钽粉在酸洗过程中吸氢演变为Ta2H,此时还原剂镁不足,未反应的Ta2O5与MgO形成难以与钽粉分离的Mg4Ta2O9;当n(Mg)∶n(Ta2O5)=7.5∶1时,氧化钽被完全还原为钽;当n(Mg)∶n(Ta2O5)=10∶1时,钽粉中氧的质量分数降低至0.58%,且形态均匀性明显提升。
Currently, the tantalum powders prepared by sodium reduction of potassium fluorotantalate cannot meet the requirements of high-end capacitors for the morphology uniformity and oxygen content of tantalum powders. This paper prepared tantalum powders by magnesium reduction of tantalum oxide-acid leaching process. The phase composition, micro-morphology, element content, and particle size distribution of tantalum powders before and after the acid leaching were studied using X-ray diffractometer, scanning electron microscope, energy spectrometer, laser particle size analyzer, oxygen/nitrogen/hydrogen analyzer, and inductively coupled plasma emission spectrometer. The results indicate that the tantalum powder particles inherit the morphology of the raw material. When n(Mg)∶n(Ta2O5)=5∶1, a few of the tantalum powders absorb hydrogen forming Ta2H during acid leaching owing to the fine grain and high activity of the tantalum, the insufficient magnesium led to the formation of Mg4Ta2O9 resulting from the reaction of unreacted Ta2O5 and MgO at this moment, which is difficult to separate from tantalum powders; when n(Mg)∶n(Ta2O5)=7.5∶1, the tantalum oxides are completely reduced to tantalum; when n(Mg)∶n(Ta2O5)=10∶1, the oxygen content of tantalum powders decreases to 0.58%, and the morphology uniformity is obviously improved.
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