J. Kubisztal

Young's modulus and adhesion coefficient of amorphous Ni-P coatings on a metal substrate

In the present paper the Youngs modulus and adhesion coefficient of amorphous Ni–P coatings obtained from aqueous solutions were determined. The measurements were carried out using a vibrating reed apparatus. In the temperature range 550–590 K, crystallization of Ni and formation of nickel phosphide Ni3P were observed. The Youngs modulus of Ni–P amorphous layers on stainless steel at room temperature was found to be about 112 GPa. The adhesion coefficient γ of the examined layers depends on the layer thickness a f and strongly decreases for a f > 8 μm. This dependence corresponds to the change of the relative adhesion coefficient of about 40% for 8 μm < a f < 15 μm. It was also shown that the adhesion coefficient does not depend on the temperature, at least in the range 300–550 K.

Magnetic and Elastic Properties of Nanocomposites Containing Soft (Ni) and Hard (SrFe12O19) Magnetic Particles

In the present paper magnetic and elastic properties of the Ni+SrFe12O19 nanocomposites were examined in detail. Samples were in two forms: i) mechanically pressed cylindrical pellets and ii) filled polymer (amine-epoxy resin) coating on aluminum substrate. The so called apparent Young’s modulus was determined by measurements of the free flexural vibrations frequency by means of vibrating reed technique. Magnetic research was carried out using VSM magnetometer. It was shown that replacement of SrFe12O19 with nano Ni powder results in an increase in material resistivity to elastic deformation. The influence of size reduction of SrFe12O19 powder particles on magnetic parameters of the studied nanocomposites were discussed in detail.

Electrodeposition and Thermal Treatment of Nickel Coatings Containing Molybdenum and Silicon

Ni+Mo+Si coatings were obtained by electrolytic codeposition of crystalline nickel with molybdenum and silicon powders from an electrolyte containing suspension of these powders. These coatings were obtained in galvanostatic conditions, at the current density of -0.100 A cm-2. Thermal treatment of these coatings in argon atmosphere was done at temperature of 1100oC for 1 hour. A scanning electron microscope was used for surface morphology characterization of the coatings. Chemical composition of obtained coatings was determined by Xray fluorescence spectroscopy method and phase composition investigations were conducted by Xray diffraction method. It was found that introduction of molybdenum and silicon into nickel matrix, causes of obtained coatings about very rough surface. Thermal treatment of these coatings influenced their surface. The surface after thermal treatment is more compact and less rough than the as-deposited one.

Production and Electrochemical Characterization of Nickel Based Composite Coatings Containing Chromium Group Metal and Silicon Powders

The Ni+Cr+Si, Ni+Mo+Si and Ni+W+Si composite coatings were obtained by electrodeposition of crystalline nickel from an electrolyte containing suspension of suitable metallic and non-metallic components (Cr, Mo, W and Si). These coatings were obtained galvanostatically at the current density of jdep = -0.100 A cm-2 and at the temperature of 338 K. Chemical composition of the coatings was determined by energy dispersive spectroscopy (EDS). The electrochemical activity of these electrocatalysts was studied in the process of hydrogen evolution reaction (HER) in 5 M KOH solution using steady-state polarization and electrochemical impedance spectroscopy (EIS) methods. The kinetic parameters of the HER on particular electrode materials were determined. It was found that Ni+Mo+Si composite coatings are characterized by enhanced electrochemical activity towards the HER as compared with Ni+W+Si and Ni+Cr+Si coatings due to the presence of Mo and increase in electrochemically active surface area.

Preparation and Structural Examinations of Gd+Ni Nanocomposites

In the paper Gd+Ni nanoparticles were obtained using chemical reaction of Gd nanopowder in the bath based on C4H6O4Ni (pH=7) at temperature 323 K. TEM examinations show Gd+Ni nanoparticles (about 200 nm) covered by GdF3 intermediate layer and Ni-P final layer Magnetization vs. temperature (5-320 K) show the Curie point of Gd at 290 K and at low temperature a paramagnetic component related to GdF3. The obtained Gd+Ni nanopowder of 200 nm in diameter can be used in future application without fear of oxidation.

ELECTROLYTIC Ni-BASED COMPOSITE COATINGS CONTAINING MOLYBDENUM AND SILICON FOR HYDROGEN EVOLUTION REACTION

Ni + Mo + SiNi composite coatings were prepared by codeposition of Ni with powders of molybdenum and silicon (covered with the electroless plated nickel — SiNi) on a steel substrate from the nickel bath in which Mo and SiNi particles were suspended by stirring. Deposition was conducted under galvanostatic conditions. Deposits were characterized by the presence of Mo and Si phases embedded into the nickel matrix. For comparison Ni + Mo composite coatings without silicon were obtained under comparable conditions. Incorporation of Mo and SiNi powders into electrolytic nickel matrix causes an increase in the real surface area of the deposits.