Electro-Deposition of Tantalum on Tungsten and Nickel in LiF-NaF-CaF2 Melt Containing K2TaF7 — Electrochemical Study
Electro-Deposition of Tantalum on Tungsten and Nickel in LiF-NaF-CaF2 Melt Containing K2TaF7 — Electrochemical Study
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DOI：
10.2320/matertrans.44.259
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发表时间：
2003-02
影响因子：
1.2
通讯作者：
M. Mehmood;N. Kawaguchi;H. Maekawa;Y. Sato;T. Yamamura;M. Kawai;K. Kikuchi
中科院分区：
文献类型：
--
作者：
M. Mehmood;N. Kawaguchi;H. Maekawa;Y. Sato;T. Yamamura;M. Kawai;K. Kikuchi
研究了在含1- 2mol%K2TaF7的55mol%LiF-35mol%NaF-10mol%CaF2熔体中700 ℃下钽的电沉积。这已被用来确定在镍和钨基体上制备钽电解涂层的机械特性。金属钽的电沉积主要通过Ta（V）i的电还原发生。例如，TaF 2- 7，电位<-0.5 V（相对于用作准参比电极的镍）。在<-0.55V的电位下，TaOF 2- 5也经历还原以形成金属钽。在LiF-NaF-CaF 2熔体中，TaOF 2- 5还原产生的氧离子被氧离子吸收剂从表面去除。纯金属钽没有任何截留盐成功地沉积在钨上恒电流极化在合理的低电流密度。镍的另一个特征是由于钽的欠电位沉积，在比纯钽的电位高约0.25 V的电位下形成金属间化合物。这种金属间化合物在短时间内覆盖表面，随后沉积纯钽，尽管由于扩散，金属间化合物在纯钽存款和基底的界面处继续生长。其它次级反应是（i）在-0. 25 V，（ii）在电极表面发生歧化反应，导致钽的部分溶解。(iii)在盐表面形成粉末状金属钽的相应反硝化反应。
Electrochemical study has been carried out on the electro-deposition of tantalum in 55mol%LiF-35 mol%NaF-10 mol%CaF 2 melt containing 1-2 mol%K 2 TaF 7 at 700°C. This has been done for determining the mechanistic features for preparing electrolytic coating of tantalum on nickel and tungsten substrates. Electro-deposition of metallic tantalum occurs primarily by electro-reduction of Ta(V) i. e., TaF 2- 7 at a potential of < - 0.5 V (vs. nickel used as a quasi reference electrode). At potentials < - 0.55 V, TaOF 2- 5 also undergoes reduction to form metallic tantalum. The oxide ions generated by reduction of TaOF 2- 5 are removed from the surface by an oxide ion getter in the LiF-NaF-CaF 2 melt. Pure metallic tantalum without any entrapped salt is successfully deposited on tungsten by galvanostatic polarization at reasonably low current densities. An additional feature on nickel is the formation of an intermetallic compound at potential ∼0.25 V nobler than that of pure tantalum as a result of underpotential deposition of tantalum. This intermetallic compound covers the surface within a short time followed by deposition of pure tantalum, although intermetallic compound keeps growing at the interface of pure tantalum deposit and the substrate as a result of diffusion. Other secondary reactions are (i) a low activity reduction of Ta (V) to Ta (II) at -0. 25 V, (ii) a conproportionation reaction at the surface of electrode leading to partial dissolution of tantalum and. (iii) a corresponding disproportionation reaction that forms powdery metallic tantalum at the salt surface.