Electrolytic Production and Structure of Ni+Al+Ti Composite Coatings

Abstract

The Ni+Al+Ti composite coatings were prepared by the electrodeposition under the galvanostatic conditions at the deposition current denisty ofjdep= -225 mA cm-2. Phase composition investigations were conducted by X-ray diffraction (XRD) method. The surface morphology, cross-section and chemical composition of the coatings were examined using a scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. Thermal treatment of the obtained composite coatings was conducted in argon atmosphere at the temperature of 800oC for 12 h. It was found that the as-deposited Ni+28at.%Al+25at.%Ti composite coating is a three-phase material (Ni, Al and Ti phases). The thermal treatment caused the chemical reaction in solid state of the heated coating, and a new multi-phase material was formed containing Ni and Al metallic phases as well as NiAl, Ni2Al3, Ni3Al, NiTi, NiTi2and Ni3Ti intermetallic phases. Thus obtained composite coatings may be useful in the applications as materials in the electrochemical processes.

Comparison of Electrochemical Properties of Ni+NiAl and Ni Coatings in an Alkaline Solution

“…1 it can be also deduced that Ni requires larger energy input for the given hydrogen evolution rate, while the electrode Ni+NiAl requires lower energy input. The reason of the increased activity of the electrode Ni+NiAl towards HER may be connected with its composite character as it was observed also in our studies of the mechanism and kinetics of HER on other composite electrodes [2,3,5,7]. X-ray diffraction pattern for such a type of the Ni+NiAl coating was shown in our previous work [3].…”

“…A frequency range from 10 kHz to 0.1 Hz was covered with 10 points per decade. The real, Z', and imaginary, Z", components of the complex plane plots were analysed using a modified version of a complex non-linear least-squares fitting program (CNLS) [2,3,5,7] from which the experimental parameters of the appropriate electrical equivalent circuit were determined.…”

“…The experimental results of the EIS investigations of the electrode | electrolyte interface show that the ac behavior of the Ni+NiAl and Ni electrodes could be described by the one-CPE electrode model which leads to a rotated semicircle on the complex-plane plot and explains ac impedance behavior of the electrode containing shallow pores on the surface [2,3,5,7]. This electrical equivalent circuit consists of the solution resistance, R s , in series with a parallel connection of CPE and charge-transfer resistance, R ct .…”

“…In the one-CPE model, the double layer capacitance, C dl , is substituted by a constant phase element. Its impedance is given as [2,3,5,7]:…”

“…Presently, electrodeposition of composite coatings containing nanoparticles of metal or intermetallic compound powders in a metallic matrix is proposed for production of a new class of electrode materials for hydrogen electroevolution reaction (HER) [1][2][3]. Possibility of co-deposition of the nanosized particles suspended in the galvanic bath using agitation (typically electromagnetic, mechanical or a rotating disc electrode) and/or surfactants, and the metal of the composite coating matrix, has been reported many times.…”