Features of thermoreactivity of electrolytic nickel coatings with different surface morphologies

Abstract

Nickel coatings consisting of oriented structures have unique catalytic properties. However, the temperature range for the use of such coatings is not determined, and a comprehensive study of their thermal properties in aggressive environments is required. This work studied the influence of the characteristics of the habit of nickel crystals on their reactivity with increasing temperature (thermoreactivity). The authors studied nickel coatings produced by electrodeposition with the addition of inhibitory additives, in the form of alkali metal chlorides to the electrolyte. Differential thermal analysis was used to study the reactivity of coatings in temperature fields. Oxygen was used as an aggressive medium. The phase composition of the samples after heating was determined, using a powder X-ray diffractometer. The introduced additives in the form of alkali metal chlorides allowed forming coatings consisting of crystals of a cone-shaped habit. It was found that the introduction of additives, in the form of alkali metal salts into the electrolyte, makes it possible to change the habit of nickel crystals, and increase the surface area of the coating by approximately 10–15 %. The study showed that electrodeposited nickel coatings, consisting of crystals in the form of micro- and nanocones, have (compared to the control coating) a reduced thermoreactivity. Experimental data allowed concluding that a decrease in the intensity of oxidation on the coatings under study, may be associated with the presence of a preferential development of certain crystallographic faces of the crystals, which causes a change in the nature of the nickel-oxygen interaction, and as a consequence, a change in the oxidation intensity.

Keywords

• nickel coatings
• nickel electrodeposition
• cone-shaped crystals
• thermoreactivity