Anomalous Electrodeposition of Alloys

合金的异常沉积是指在某些条件下，非贵金属优先于贵金属沉积。本项目旨在通过实验和数学模型来了解电镀过程中异常共沉积的机理。以前关于镍-铁共沉积的工作表明，氢氧化物物种的变化转移导致了异常；这项工作确定了这一机制是否可以扩展到解释镍铁、钴和锌相互合金的异常共沉积。研究了缓冲镀液pH的影响。数学模型由两部分组成：平衡计算和一维扩散模型，其中包括缓冲和水解反应的影响。这种现象在铁、钴、镍和锌的相互合金中最为常见。这些合金因其高强度、高硬度和高磁性而被广泛应用于电镀薄膜。电沉积锌镍为钢提供腐蚀保护；高铁镍铁(如因瓦铁)用于需要低热膨胀的地方，包括微波导轨。光学。激光外壳和印刷电路板；钴-镍、铁-钴和镍-铁等铁磁合金广泛用于电子和磁性设备，包括计算机存储器、磁屏蔽和磁记录头。

Anomalous deposition of alloys is defined by the less noble metal depositing preferentially to the more noble metal under certain conditions. This project aims to understand the mechanism of anomalous codeposition in plating processes using experiments and mathematical modelling. Previous work on the codeposition of nickel-iron suggests that change transfer in the monohydroxide species causes the anomaly; this work ascertains whether or not this mechanism can be extended to explain anomalous codeposition of the mutual alloys of nickel iron, cobalt, and zinc. The effect of buffering the pH of the plating bath is also investigated. Mathematical modelling consists of two parts: equilibrium calculations and one- dimensional diffusion modelling which includes the effects of buffering and of hydrolysis reactions. This phenomenon is most commonly encountered with the mutual alloys of iron, cobalt, nickel, and zinc. These alloys are widely used in electroplated films because of their high strength, hardness, and magnetic properties. Electrodeposited zinc-nickel provides corrosion protection for steel; high-iron nickel-iron (such as Invar) is used where low thermal expansion is required including microwave guides. optics. laser housings, and printed circuit boards; ferromagnetic alloys such as cobalt-nickel, iron-cobalt, and nickel-iron are widely used in electronic and magnetic devices including computer memory, magnetic shielding, and magnetic recording heads.