Electrodeposition of Ni from Various Non-Aqueous Media: The Case of Alcoholic Solutions

Abstract

Although electrodeposition from aqueous media has been widely used to obtain metallic deposits, there are cases where the application of non-aqueous solutions offers advantages over the traditional baths or even represents the only way to electrodeposit some metals. For this reason, a study of the electrodeposition of Ni from various alcoholic solutions was performed. Apart from a detailed cyclic voltammetry study of these solutions, the surface morphology, crystal structure and texture as well magnetic properties of the deposits have also been investigated. The best results were obtained with methanol as solvent, so results on Ni deposits prepared from this solution will be presented in more detail whereas the case of the other alcoholic solutions investigated will be summarized only briefly. Structural and magnetic properties of the deposits obtained have been compared to literature data on Ni samples obtained from various non-aqueous solvents. Electrodeposition of metals and alloys has long been an important topic of scientific and technical literature.1 The overwhelming majority of technologically relevant electroplating procedures are based on various aqueous solvents.2 In spite of the scattered appearance of the application of non-aqueous solvents, the breakthrough happened only when ionic liquids became a hot topic and many papers appeared about the electrodeposition of such metals from these electrolytes 3 that are not accessible with conventional aqueous electroplating.Apparently, Takei initiated first a series of studies for the electrodeposition of metals from non-aqueous solutions.4-8 The main motivation for his efforts was 7 the need for obtaining electrodeposits of metals like Al and Be which cannot be electrodeposited from aqueous solutions. There are also several other metals or alloys which have useful properties from the viewpoint of industrial applications but cannot be electrodeposited from aqueous solutions. In spite of the efforts after the works by Takei, the literature of metal and alloy electrodeposition from non-aqueous solutions is not very abundant (apart from the extended literature of electrodeposition from ionic liquids which was reviewed in Ref. 3).As to the electrodeposition of Ni from non-aqueous solutions, several papers have been published on this topic 3,4,6,7,9-16 but we shall here only briefly mention some of these results. Lee et al.14 reported the growth of nanocrystalline Ni films on n-Si(111) substrate by pulsed electrodeposition. A room-temperature methanol solution with dissolved NiCl 2 (in 0.1 M concentration by using the hydrated NiCl 2 salt) was used which was purged with high-purity nitrogen to remove the oxygen. The potential pulses were applied at various frequencies with a constant duty cycle of 50%. Nickel was also electrodeposited from a Ni(CF 3 COO) 2 -halide-methanol bath.6,7 Plating of nickel with various ceramic particles (also referred to as suspension plating) was carried out using an ethanol-based nickel bath. The effects of particle loading, current d...

Corrosion properties of nickel coatings obtained from aqueous and nonaqueous electrolytes

“…At a thickness of 9 μm, there were 24 pores per cm 2 in the coating formed from the aqueous solution, while the coating formed from a nonaqueous electrolyte had 19 pores per cm 2 . In the case of the ethanol solution, there is a possibility of salt film formation during electrodeposition due to chemical inclusion of alcoholate anions and nickel cations …”

“…Relatively uniform nickel layers were deposited, as shown in Figure A , B . Coatings deposited from ethanol‐based electrolyte had no clear defects associated with internal stresses, which has been reported in Neuróhr et al No visible surface cracking was observed with AFM, as can be seen in Figure E , F . The surfaces were homogeneously covered and are relatively flat with an average roughness (R a ) measured for 20 μm × 20 μm areas of 157 nm for the coating deposited from aqueous electrolyte and 164 nm for the coating deposited from nonaqueous electrolyte.…”

“…It is known that changing the solvent in the nickel electrolyte affects the mechanism of electrodeposition and, consequently, alters the properties of the nickel coatings formed. The use of nonaqueous electrolytes enables formation of nanocrystalline deposits and eliminates the effect of hydrogen, which can lead to the embrittlement of nickel coating . Nevertheless, electrodeposition of metals and alloys from nonaqueous solutions provides an easy and cost‐effective way to fabricate thin films.…”

“…The use of nonaqueous electrolytes enables formation of nanocrystalline deposits and eliminates the effect of hydrogen, which can lead to the embrittlement of nickel coating. 19,20 Nevertheless, electrodeposition of metals and alloys from nonaqueous solutions provides an easy and costeffective way to fabricate thin films. Conventional aqueous solutions cannot always be used as deposition electrolytes due to their narrow electrochemical window, low thermal stability, and poor solvent evaporation.…”

“…Several approaches for electrodeposition of Ni from nonaqueous solutions have been proposed. [20][21][22] A review of alcoholic solvents for Ni deposition was done by Neuróhr et al 20 The work reports that methanol has proved to be an appropriate medium for the deposition of compact nickel coatings from dry NiCl 2 salt and that Ni-containing deposits can be obtained from ethylene glycol, 1,2-propanediole, and 1,3-propanediole. For ethanol electrolyte, it was found that the film deposits lack the ferromagnetic component.…”