The continued development of multilayered and compositionally modulated electrodeposits

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 m 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, toolbits and heavy engineering. Speciality uses include electronic, optical and magnetic materials as well as catalytic electrode surfaces for electrochemical technology. Recommendations are made on aspects which deserve further R & D.

Structural Properties of Zn-Fe Alloy Coatings and Their Corrosion Resistance

“…For a thorough assessment of the structure of multilayer coatings, however, a number of characteristics, such as the structural, surface, and interface roughness, as well as the sub-layer coherency, must normally be determined [16]. These multilayer alloy coatings are prepared by a new technique, the single bath technique (SBT), which is gaining much interest because it exhibits superior corrosion properties [17][18][19][20][21]. From the literature, it is indicated that there is not much work that has been reported concerning the deposition optimization of multilayer deposits to produce nanostructured multilayer deposits for superior corrosion resistance (CR).…”

Spacer Layer Thickness Dependence of the Giant Magnetoresistance in Electrodeposited Ni-Co/Cu Multilayers

“…In addition to the above-mentioned physical deposition methods, it was demonstrated by Alper et al [ 25 , 26 ] in 1993 that the cost-efficient and simple technique of electrodeposition can also be tailored to a level that enables the preparation of magnetic/non-magnetic multilayers exhibiting the GMR phenomenon. The study of GMR in electrodeposited multilayers has considerably expanded since that time as summarized in several reviews [ 27 , 28 , 29 , 30 , 31 , 32 , 33 ] and has remained an active area of research [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. The electrodeposition method is accessible for the preparation of magnetic/non-magnetic multilayers in which the magnetic layers are composed of the FM elements Fe, Co and Ni and their mutual alloys, whereas the non-magnetic spacer layer is in most cases Cu.…”

“…The electrodeposition method is accessible for the preparation of magnetic/non-magnetic multilayers in which the magnetic layers are composed of the FM elements Fe, Co and Ni and their mutual alloys, whereas the non-magnetic spacer layer is in most cases Cu. The basic elements of multilayer fabrication by electrochemical methods have been described in detail in some recent reviews [ 28 , 31 , 32 , 33 ].…”

“…It should be pointed out, however, that in the majority of papers reported on the GMR of electrodeposited multilayers [ 27 , 28 , 29 , 30 , 31 , 32 , 33 ], two major aspects of the deposition conditions and the magnetoresistance evaluation have not been properly considered, although these aspects have a profound influence on the interpretation of the GMR results obtained.…”