Effect of deposition current density and annealing temperature on the microstructure and magnetic properties of nanostructured Ni-Fe-W-Cu alloys

Milica Spasojevic,Dusan Markovic,Aleksa Maricic,Miroslav Spasojevic,Zoran Vukovic,Lenka Ribic-Zelenovic

doi:10.2298/sos1902209s

Abstract

Ni-Fe-W-Cu alloy powders were obtained by electrodeposition from an ammonium citrate bath at current densities ranging between 70 and 600 mA cm-2. As the deposition current density increased, the contents of Fe and W in the alloy increased, and those of Ni and Cu decreased. The total cathodic polarization curve was recorded, and partial polarization curves for Ni, Fe and W deposition and hydrogen evolution were determined. The current efficiency of alloy deposition was measured. The powders contained an amorphous matrix and FCC nanocrystals of the solid solution of Fe, W and Cu in Ni. At high current densities, small-sized nanocrystals exhibiting high internal microstrain values were formed. Powder particles were dendrite- and cauliflower-shaped. The dendrites had a large number of secondary branches and higher-order branches containing interconnected globules. The density of branches was higher in particles formed at high current densities. The powders formed at high current densities exhibited higher magnetization. Annealing at temperatures up to 460?C resulted in structural relaxation, accompanied by an increase in magnetization. At temperatures above 460?C, amorphous matrix crystallization and FCC crystal growth took place, accompanied by a decrease in magnetization.

Highlights

Nanostructured materials have been increasingly used in a wide range of technologies
Nickel-iron-tungsten-copper alloy powders were deposited on the titanium cathode at current densities of 70 mA cm-2, 200 mA cm-2, 400 mA cm-2 and 600 mA cm-2 from an ammonium citrate bath
The chemical composition of the powders was determined by atomic absorption analysis

Summary

Introduction

Nanostructured materials have been increasingly used in a wide range of technologies. Nickel-iron-tungsten alloys are in wide use in different industries for the fabrication of a variety of devices, such as inductor cores for electromagnets [2,3,4], magnetic devices [5], microwave noise filters [6], magnetic recording heads [7,8,9] and tunable noise suppressors [10]. They are used as catalysts in some chemical processes and as cathodes for the electrochemical production of hydrogen [11].

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