CsCl对NaCl-KCl-CsCl熔盐物理性质及铌涂层电沉积行为的影响

Effect of CsCl on the physical properties of NaCl-KCl-CsCl molten salts and electrodeposition behavior of niobium coatings

摘要:

因其优异的综合理化性能，铌（Nb）被广泛应用于航空航天、核能和超导领域。其涂层制备方法中，熔盐电沉积技术沉积速率快、阴极电流效率高、绕镀性好，有望实现大规模工业化生产和应用。当前广泛使用的氟化物支持电解质体系毒性大、环保性差，亟待开展更环保的全氯化物支持电解质体系的开发工作。为实现支持电解质熔盐物性的调控和络合离子的稳定化，本文在NaCl-KCl体系中添加CsCl，制备全氯化物支持电解质体系，研究CsCl对支持电解质熔盐物理性质及Nb涂层电沉积行为的影响。结果表明，NaCl-KCl-CsCl三元混合熔盐的共晶温度约为485℃，随CsCl含量增加，熔盐的初晶温度先降低后增大，密度增大，电导率和表面张力减小。CsCl通过改变熔盐的初晶温度和电导率影响熔盐中离子的传质速度，进而影响电沉积Nb涂层的表面质量，其优选含量约为60wt.%。CsCl的添加可使熔盐中含氧络合离子NbOF63-的还原电位负于NbF72-，有助于获得不含氧杂质的Nb涂层。

Abstract:

Niobium (Nb) is widely used in aerospace, nuclear energy and superconducting fields, due to its excellent comprehensive physical and chemical properties. In the preparation methods of the Nb coating, the molten salt electrodeposition technology has fast deposition rate, high cathode current efficiency and is suitable for complex shape components, which is expected to realize large-scale industrialized production and application. Since the current widely used fluoride-supported electrolyte system is highly toxic and environmentally unfavorable, there is an urgent need to carry out the development of a more environmentally friendly all chloride supporting electrolyte system. To achieve the regulation of the molten salt’s physical properties of the supporting electrolyte and the stabilization of the complexing ions, this study adds CsCl to the NaCl-KCl system to prepare an all chloride supporting electrolyte system and investigates the effect of CsCl on the molten salt’s physical properties of the supporting electrolyte and the electrodeposition behavior of the Nb coating. The results showed that the eutectic temperature of the NaCl-KCl-CsCl ternary mixed molten salt was about 485 °C. With the increase of CsCl content, the initial crystallization temperature of molten salt decreased at first and then increased, the density increased, and the conductivity and surface tension decreased. CsCl affected the mass transfer rate of ions in molten salt by changing the initial crystal temperature and conductivity of molten salt, and then affected the surface quality of electrodeposited Nb coating, and its preferred content was about 60 wt.%. The addition of CsCl can make the reduction potential of the oxygen-containing complex ion NbOF63- in the molten salt negative to that of NbF72-, which was helpful to obtain Nb coatings without oxygen impurities.