Formation of Al-Ni master alloys using nickel anode

Nickel anode was investigated as a potential anode of aluminium electrowinning for preparation of Al-Ni master alloys. The electrolysis tests were carried out in Na3AlF6-Al2O3 based melts at 940℃. The results show that the cell voltage during electrolysis has only minor instability, and there exists NiO phase in electrolyte after 0.5 h electrolysis. Ni content in A1-Ni master alloys increases with increasing the electrolysis time. Concentration limit of Ni in Al-Ni master alloys can be up to 33.8% （mass fraction）. However, substantial corrosion of the Ni-metal substrate is observed, and the oxide scale on the nickel anode after electrolysis is porous and loose that does not prevent corrosion of the substrate.     

Density and ionic structure of NdF3-LiF melts

NdF3-LiF melts are commonly used in the electrolysis process of metallic neodymium production. Research on the density and ionic structure of the electrolyte is important for its close connection with the electrolysis mechanism and process. In this paper, the density of LiF-NdF3 melts was studied by the Archimedes method. The results showed that the density decreased with increasing temperature and LiF contents. The changing law was discussed and explained in terms of the micro ionic structure of the melts....     

铝电解质成分对钠和电解质渗透行为的影响

分别从电解质分子比、氧化铝含量和添加剂氟化镁含量的变化方面,研究电解质成分对钠和冰晶石-氧化铝熔液向阴极碳块渗透的影响.结果表明,随着电解质分子比的增加,阴极碳块中渗透的物质增多,分子比越大,渗透就越深.加大氧化铝的含量使钠向阴极碳块的渗透能力增强.添加剂氟化镁能够减小钠和电解质向阴极碳块的渗透.     

不锈钢表面电镀Cu-Mn_3O_4复合涂层

铁素体不锈钢的热膨胀系数与固体氧化物燃料电池(SOFC)的组元相近,成本低廉,具有良好的抗氧化性,已被广泛用作SOFC电池堆的金属连接体材料.但是表面Cr2O3膜的挥发会导致SOFC阴极Cr中毒,缩短SOFC的服役寿命.为解决这一问题,本文利用电镀的方法在铁素体不锈钢(SUS 430)连接体表面沉积CuMn3O4复合涂层,研究了复合电镀Cu-Mn3O4涂层的电镀工艺,结果表明:复合电镀的适宜工艺参数为:溶液pH值为3,阴极电流密度为2.12 A/dm2,镀液温度为35℃,溶液中Mn3O4粉末添加量为20 g/L.并研究了涂覆不锈钢在800℃空气中的氧化行为及氧化膜的导电性能.涂覆Cu-Mn3O4不锈钢氧化后表面生成CuO、(Mn,Cu)3O4和(Fe,Cu)3O4尖晶石氧化物,表面氧化物的导电性良好,并能有效阻止Cr向外迁移和扩散.     

铝电解槽中黏土质砖的抗渗性研究

通过浸泡法和坩埚法对铝电解槽用黏土质砖进行抗渗性研究,利用X射线衍射法对工业上已经使用过的黏土质砖进行分析.结果表明,黏土质耐火砖在高分子比的电解质中浸泡2h后,质量损失率是47.25%,而黏土质保温砖经90min的浸泡后完全溶解在电解质里.坩埚法试验中,耐火砖要比保温砖的抗渗性能好,但两种砖都不耐电解质渗透.工业电解槽中,渗透到黏土质砖的电解质中含有大量的NaF,黏土质砖中的莫来石变成了霞石.     

Equivalent conductivity and its activation energy of NaF-AlF3 melts

Electrical conductivity of NaF-AlF3 melts was measured by continuously varying cell constant(CVCC) technique. Relationships between equivalent conductivity at 990-1 030 ℃ and temperature and composition, and relationship between equivalent conductivity activation energy and composition of the melts were then studied on the basis of two-step decomposition mechanism of AlF63-. According to the changes of molar fractions of different anions in NaF-AlF3 melts, courses of dependence of equivalent conductivity and its activation energy on composition were analyzed. The results show that the influence of temperature on equivalent conductivity of the melts is small in the researched temperature range, and equivalent conductivity increases with increasing the molar fraction of AlF3; there is a minimum point in the activation energy-composition curve when molar fraction of AlF3 is 0.29.     

Identification of structural entities in NdF3-LiF melts with cryoscopic method

Nd-F species in NdF3-LiF melts were studied using cryoscopic method.Liquidus temperatures of melts of various compositions were determined by differential thermal analysis(DTA).Based on the different model calculations,NdF4- was identified as the most likely Nd-F entity in the melts in which the mole fraction of NdF3 was lower than 20%,considering only one single Nd species in the melt,and which was formed in accordance with Temkin model or Flood model.Then,activities of different components in the melts were researched.The results show that activity of LiF decreases,and that of NdF3 increases with increasing the mole fraction of NdF3.The value of activity coefficient of NdF3 is higher than 1,and that of LiF is lower than 1.     

电极材料对铝电解阴极过程研究的影响

电解铝工业中铝的析出发生在阴极上,研究铝析出反应的机理对实际工况有很好的指导意义。研究发现,炭电极上的Al、Na共沉积现象严重,致使循环伏安曲线上Al的析出峰被掩盖。因此人们试图用一些金属电极Ni、Pt、Au、Ta、Cu、W等来代替炭电极,但研究发现大部分金属电极都与Al反应生成合金,干扰了对真实电极过程的研究。只有W与Al的合金化作用较小,因此对冰晶石一氧化铝熔体的阴极电化学研究采用了W电极。而目前TiH2基可湿润阴极是极具发展前景的铝电解槽阴极材料,但这方面的研究还很不够,需做进一步的研究。     

Nd(III)在NaF-KF熔盐钨电极上电化学行为

钕铁硼磁体中稀土元素钕占据较大比重,从钕铁硼废料回收稀土有重大意义。为进一步了解钕在高温下氟化物熔盐的行为,本文在1 063 K采用NaF-KF(摩尔比2:3)电解质体系,加入质量分数为1%的NdF₃,以Pt为参比电极,钨棒为对电极,用循环伏安法等电化学暂态测试研究了Nd(III)在惰性钨电极上的电化学过程,探究Nd(III)的还原机理。结果显示:Nd(III)于NaF-KF-NdF₃熔盐中在惰性钨电极上的电化学还原过程是受扩散控制的不可逆的一步反应:Nd(III)+3e-=Nd,1 063 K时循环伏安法得到Nd(III)的扩散系数为2.107×10-5 cm2/s,钕的成核机制为瞬时成核。      

新型炼铝电极材料

研制了一种新型铝电解金属陶瓷惰性阳极,阳极基体由Fe-Ni-Co-Al-O构成.在电解温度960℃,氧化铝质量浓度为6.0%,阳极电流密度为1.0 A/cm2,分子比为2.6的电解质中对其进行了10 h的电解.电解过程平稳,电解铝产品纯度达到96%～99%,阳极气体中氧气的含量为98%,反电动势为2.45 V,高于理论值0.25～0.35 V.此阳极具备较好的导电性、抗氧化和耐腐蚀性.采用X射线衍射和电子探针微分析仪(EPMA)对电解后的阳极进行分析,发现阳极表面存在铁酸镍、铝酸铁等尖晶石型化合物,阳极表面下层为铝酸铁、钴酸镍等陶瓷相以及金属相;金属相和陶瓷相相互弥散分布构成结构致密的金属陶瓷层.