ABSTRACT

Traditionally, electroplating has involved the continuous deposition of a single layer of metal at constant current. However, electrodeposition of alternate layers can offer benefits such as reduced wear, improved corrosion resistance and higher tensile strength. The alternate layers can involve different morphology or thickness of metal, different metals or the alloy composition of layers with and without included particles. In the case of a single bath, electrocrystallisation is continuous but layers can be tailored to have different chemical composition, phase composition, morphology and microstructure. The composition of layers can also be systematically modified in a gradient fashion. The thickness of each metal layer can vary from >20 μm down to ≈1 nm; in the case of nanometre thick layers, up to 500 layers of 1 nm thick individual layers might be involved. Compact multilayer deposition from a single bath is often achieved by applying a potential waveform in the laboratory or pulsed current in industry. While multilayer electrodeposition is going through a phase of rediscovery, growth and diversification, the field can be traced back to a patent involving Cu–Ni multilayers, in 1905. Progress in multi-layered electrodeposition has made use of contemporary trends in electroplating research, including self-assembled layers, nanowire arrays and the use of deep eutectic solvents for electrolytes. The developing uses of multilayer deposits are seen to span industries as diverse as wear and corrosion resistant coatings, tool bits and heavy engineering. Speciality uses include electronic, optical and magnetic materials as well as catalytic electrode surfaces for electrochemical technology. Recommendations are made for topics which deserve further R & D.

摘要

传统上，电镀涉及以恒定电流连续沉积单层金属。然而，交替层的电沉积可以提供诸如减少磨损、改进的耐腐蚀性和更高的拉伸强度等好处。交替层可涉及不同形态或金属厚度、不同金属或具有和不具有包含颗粒的层的合金成分。在单个浴的情况下，电结晶是连续的，但可以定制层以具有不同的化学成分、相成分、形态和微观结构。层的组成也可以以梯度方式系统地修改。每个金属层的厚度可以从 >20 μm 到 ≈1 nm 不等；在纳米厚层的情况下，可能涉及多达 500 层 1 nm 厚的单个层。通常通过在实验室中施加电位波形或在工业中施加脉冲电流来实现单浴的紧凑多层沉积。虽然多层电沉积正在经历重新发现、增长和多样化的阶段，但该领域可以追溯到 1905 年涉及 Cu-Ni 多层的专利。多层电沉积的进展利用了电镀研究的当代趋势，包括自组装层、纳米线阵列和使用低共熔溶剂作为电解质。多层沉积物的发展用途被视为跨越多个行业，如耐磨和耐腐蚀涂层、工具钻头和重型工程。专业用途包括电子、用于电化学技术的光学和磁性材料以及催化电极表面。对值得进一步研发的课题提出建议。