Electrodeposition, Microstructure and Magnetic Properties of Nickel-Cobalt-Copper Alloy Powders

Abstract

Powders of Ni-Co alloys containing small amounts of Cu were produced by electrodeposition from an ammonium bath. Cathodic polarization curves were recorded and partial current densities for alloy deposition and hydrogen evolution were determined. At a current density of 100 mA cm −2 , the electrodeposition process resulted in Ni 79.1 Co 18.6 Cu 2.3 powder with an average grain size of 6.8 nm, composed of an amorphous matrix and FCC nanocrystals. The deposition of Cu with Ni and Co led to a higher proportion of the amorphous phase, smaller nanocrystals and smaller powder particles in the electrodeposit than in the alloy without copper. During annealing at temperatures ranging from 25 • C to 160 • C, no structural changes occurred in the powder. Upon structural relaxation in the temperature range of 160-350 • C, the powders cooled at 25 • C showed greater magnetic permeability. At temperatures between 350 • C and 430 • C, the amorphous phase exhibiting relatively lower magnetization underwent crystallization, accompanied by the formation of small-sized FCC nanocrystals, which had relatively higher magnetization values, leading to an increase in the magnetic permeability of the cooled powder. At temperatures above 430 • C, the formation of large crystalline grains at the expense of small ones caused a decrease in magnetization.

Characterization of Ternary CuNiCo Metallic Nanoparticles Produced by Hydrogen Reduction

“…An increase in the Cu content in the metal powder promotes the nanoparticles' self-sintering and the further coalescence of the obtained ternary alloy powder-possibly due to its lower melting point (see Table 3). A similar phenomenon was observed by [20] as it is reported that the presence of copper may cause a nucleation effect during deposition. The elemental mapping of the 10Cu80Ni10Co metallic powder reduced at 300 • C is shown in Figure 9.…”

“…This result suggests that the three metal powders, under these compositions, may constitute a single FCC phase, with the same matrix as in the three alloys. The same XDS result for a Cu-Ni-Co alloy produced by different methodologies can be found in the literature, where it the presence of a similar FCC phase is mentioned [6,8,11,14,19,20]. The calculations of the Rietveld method were not accomplished due to the lack of reported phases that contain these elements (Cu, Ni and Co) in the Inorganic Crystal Structure Rietveld's Database (ICSD).…”

“…However, it is well known that one of the challenges of obtaining nanoparticles' alloy content is the production process and thus, different methodologies have been investigated, which can be categorized as either chemical or physical based techniques. There is electrodeposition [5,6,[18][19][20], vapor deposition [21,22], mechanical alloying [3], synthesis by hydrazine reduction [17], positive microemulsion [23], and melt spinning [15]. Electrodeposition is the most common studied method which has allowed to obtain uniform, smooth and fine-grained alloys with adequate morphology for specific applications [18].…”

“…Electrodeposition is the most common studied method which has allowed to obtain uniform, smooth and fine-grained alloys with adequate morphology for specific applications [18]. Nonetheless, it incorporates a certain complexity that complicates its application at a large scale [5,14,[16][17][18]20]. The hydrogen reduction of homogeneous co-precipitated oxides has been mentioned as an alternative method to obtain binary alloys [24][25][26] and nanocomposites [27][28][29][30], but it has not yet been studied as a method of obtaining ternary alloys.…”

Influence of Ni2+/Co2+ ratio in electrolyte on morphology, structure and magnetic properties of electrolytically produced Ni-Co alloy powders

“…Electrodeposition of the binary Ni−Co system has been studied comprehensively, mainly due to its importance in the soft magnetism field [37,38]. The possibility to obtain different nanostructures and/or morphologies provides an excellent opportunity for establishing correlations between structure and magnetism of these alloys, and consequently to tailor their magnetic properties.…”