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

Abstract

Nickel−cobalt (Ni−Co) alloy powders were produced galvanostatically by using sulphate electrolytes with various ratios of Ni 2+ /Co 2+ (mole ratios). The morphology, phase structure, chemical composition and magnetic properties were examined by scanning electron microscope (SEM), X-ray diffractometer (XRD), atomic emission spectrometer (AES), and SQUID-based magnetometer, respectively. Morphology of the particles changed from cauliflower-like and dendritic to coral-like and spongy-like ones with increasing Ni 2+ /Co 2+ ratio from 0.25 to 4.0. XRD analysis of the Ni−Co powders revealed that the decrease of Ni 2+ /Co 2+ ratios (the increase of Co content) caused a change of structure from face centered cubic (FCC) obtained for the ratios of 4.0, 1.5 and 0.67 to a mixture of FCC and hexagonal closed-packed (HCP) phases for the ratio of 0.25. The increasing content of nickel led to change of mechanism of electrolysis from irregular (up to ~40 wt.% Ni in the electrolytes) to close to equilibrium (between ~40 and 60 wt.% Ni in the electrolytes) and anomalous co-deposition (over 60 wt.% Ni in the electrolytes) type. All of the obtained Ni−Co alloy samples behaved as soft magnetic materials while their magnetic parameters showed immediate composition dependence since both coercivity and saturation magnetization almost linearly increased with increase of the Co content.

Growth inhibition of bacterial pathogens by photo-catalyst process of nano-alloys FeCuNi doped TiO2 under ultraviolet irradiation

“…MDA is the final product from the result of an oxide saturated process in the cell membrane. Figure 10 shows the numbers of MDA product which were formed from a series of ·OH radical attacking process in the bacteria cell partition that was determined by applying the TBARs method [ 47 ].…”

“…The inhibition of FeCuNi–TiO 2 photo-catalyst at microbe can be explained by the attack from O 2 radicals and ·OH of photo-generated electron holes on the catalyst surface. Among the three types of species, ·OH radical is the most reactive because it has very effective oxidation capabilities for various kinds of organic compounds, such as microbe cells [ 47 ].…”

Co-deposition of Co–Ni alloy catalysts from an ethylene glycol system for the hydrogen evolution reaction

“…Although these Co–Ni alloys with different surface morphologies and various Co contents could be prepared from aqueous systems containing Co 2+ and Ni 2+ (as seen in Table 1), these electrodeposition processes were usually accompanied by an intensive hydrogen evolution reaction (HER), resulting in a profound effect on the current efficiency and quality of the Co–Ni alloy coatings. 3,5,6,8–23 Importantly, a few holes 6,9,11,19,21 and/or microcracks 3,5,16 (as seen in Table 1) could be found on the Co–Ni alloys electrodeposited from aqueous systems, resulting in a profound effect on the catalytic stability for the HER.…”