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研究了NaCl-KCl-K2HfF6体系下,以海绵铪和还原铪粉作可溶性阳极,不锈钢为阴极,熔盐电解精炼铪的工艺条件。采用X射线衍射物相分析(XRD)对不同方法制备的铪氟酸钾进行了分析,采用示差扫描量热法(DSC)测量了NaCl-KCl-K2HfF6熔盐体系的熔点,采用扫描电镜(SEM)对该熔盐体系下电解精炼得到的铪粉进行了观察,并采用激光衍射散射式粒度分布测定仪测定了铪粉的粒度分布。结果表明氟硅酸钾烧结法制备的铪氟酸钾纯度高,无有害杂质。最佳工艺条件为:熔盐组成为K2HfF620%(质量分数),NaCl∶KCl为1∶1(摩尔比);电解温度750℃;阳极料为海绵铪和还原铪粉时,电流密度分别为1.2和0.5 A·cm-2。在此条件下得到的铪粉精炼效果良好,产品主要杂质总含量降低至0.07%以下。阴极电流密度较低时,电解得到的铪粉形貌是粗大的块状颗粒,粒度分布在80～150μm之间。增大电流密度,铪粉粒度减小,并出现类似树枝状形貌。进一步增大电流,出现细小的不规则颗粒,粒度分布在40～90μm。增加电解时间可以提高杂质元素与铪之间的分离效果。
Under NaCl-KCl-K2HfF6 system, hafnium sponge and reduced hafnium powder as soluble anode, stainless steel as cathode, molten salt electrolysis of hafnium process conditions. The melting point of NaCl-KCl-K2HfF6 molten salt system was measured by differential scanning calorimetry (DSC). X-ray diffraction (XRD) analysis of potassium hafnium difluoride prepared by different methods using scanning electron microscopy Hafnium powder obtained by electrolytic refining under the molten salt system was observed and the particle size distribution of hafnium powder was measured by laser diffraction scattering particle size distribution analyzer. The results show that potassium fluosilicate prepared by potassium fluosilicate sintering has high purity and no harmful impurities. The optimum technological conditions are as follows: the composition of molten salt is K2HfF620% (mass fraction), NaCl: KCl is 1: 1 (molar ratio); the electrolysis temperature is 750 ℃; the current densities of hafnium sponge and reducing hafnium powder are 1.2 And 0.5 A · cm-2. The hafnium powder obtained under this condition has a good refining effect, and the total content of major impurities in the product is reduced to below 0.07%. When the cathode current density is low, the hafnium powder morphology obtained by electrolysis is coarse massive particles with particle size distribution between 80 and 150 μm. Increasing the current density, hafnium powder particle size decreases, and similar dendritic morphology. Further increase the current, the emergence of small irregular particles, particle size distribution in the 40 ~ 90μm. Increase the electrolysis time can improve the separation between the impurity elements and hafnium.