Na_3AlF_6-K_3AlF_6-AlF_3电解质体系铝溶解度的研究

Solubility of Aluminium in Na_3AlF_6-K_3AlF_6-AlF_3 Electrolyte System

采用质量差法研究了不通电时Na3AlF6-K3AlF6-AlF3体系中铝的溶解度。实验首先测定了不同时间内铝溶解的情况,并确定铝饱和溶解的时间为3 h。主要研究了初晶温度、过热度、电解质组成,以及电解质融化之后的熔盐深度对铝溶解度的影响。实验选用刚玉坩埚盛装电解质。测试结果表明,初晶温度为670～900℃的电解质,铝的溶解度为0.05%～0.50%(质量分数)。在初晶温度较低的电解质中,铝的溶解度较低,反之较高。对于某个特定体系来说,提高过热度会增加铝的溶解度。电解质的组成对铝溶解度的影响是:增大KR,可以降低铝的溶解度;AlF3含量增加,铝溶解度降低;对于KR=30,AlF3=26%(质量分数)的电解质,出现了异常的情况。另外,减少电解质的用量,降低熔盐的深度,也会造成铝的挥发损失,并最终导致铝的溶解增加。总之,影响铝溶解度的因素是多方面的,抑制铝的溶解损失,可以从改变电解质的组成、降低初晶温度、减少铝的挥发等方面着手。

The dissolubility of aluminium in Na3AlF6-K3AlF6-AlF3 electrolyte system was studied by mass difference methods.The dissoluble amount of aluminium in different times was measured,and found that aluminium was saturated 3 h later.Influence factors,such as liquidus temperature,superheat degree,electrolyte components,and the depth of molten salt were focused.The results showed that the solubility of aluminium ranged from 0.05% to 0.50% for electrolyte system with liquidus temperature of 670~900 ℃.For electrolyte system with lower liquidus temperatures,the solubility of aluminium was lower too,vice versa.For a single system,the increase of superheat degree would increase the solubility of aluminum.The effect of electrolyte composition on the solubility of aluminum as follows： Increasing KR value would reduce the solubility of aluminium.However,as to the system KR=30,AlF3=26%（mass fraction）,did not meet above regulations.Besides,reduced electrolyte amount,lowered the depth of molten salt,and led to the volatilization loss of aluminium.In short,the factors affecting the dissolubility of aluminium were various.To change electrolyte components,reduce liquidus temperature and volatilization of aluminum would restrain aluminium loss.