Papers by Author: Grzegorz Dercz

Abstract: The growth morphology and arrangement of tungsten and β-phase (Al (Fe, Cu)) in Al‑Cu‑Fe‑W alloy were analyzed. The composition of Al₆₅Cu₂₀Fe₁₄W₁ (at.%) was used for preparation of ingots containing the icosahedral quasicrystalline phase.The ingots were obtained in a two-stage process. At the first stage the induction melting of the elements and preliminary homogenization by mechanical mixing were carried out. The second stage was realized by vertical Bridgman technique of directional crystallization. The X-ray phase analysis, optical and scanning electron microscopy (SEM) observations and chemical analysis were performed. It was stated that the whiskers of tungsten were irregularly distributed in the volume of ingots. They often form a clump-like agglomerations. The whiskers have different diameters and length. Minimal diameter of the whiskers was about 10 – 100 nm and maximal – several dozen micrometers. The whiskers of tungsten formed a clump-like frames on which the membrane form of β-phase was stretched out or a non-planar oval forms.

Abstract: The electrode processes are often studied on iron for the needs of hydrogen technologies. This paper presents the use of the resources of the “MicroScan” program in manual methods to determine the stereological parameters of the Armco iron. For this purpose, the average number of particles per one unit of the N_A surface area and the average surface area of the grains in the 〈A flat structure were determined, using the planimetric, the Jeffries and the comparative methods. The linear method was used to determine the average number of segments per one length unit of the N_L structure and the average length of the circuits of grains in the 〈L flat structure. It was found out that the mean values of the determined parameters were in line with the PN-84/H-04507 standard and small differences existing in the obtained results were due to the jumping character of the pattern scale of the mentioned standard. The relative error of the N_A and A parameters indicates that the planimetric method allows to achieve the most accurate measurement of the size of the grain.

Abstract: The coulometric or anodic de-plating technique can be used for measuring the thickness of coatings on virtually all substrates such as steel, non-ferrous metals or insulating material bases. This study reports on application of an electrochemical de-plating technique for measuring the thickness of multilayer Ni/Cu coatings electrodeposited on a steel substrate. Principles of a coulometric method by local anodic dissolution according to ISO 2177:2003 have been explained. The phase analysis of the Ni/Cu multi-layer coatings was performed using GIXD technique. The summary of the GIXD diffraction patterns obtained in this experiment indicates that such electrocoating is composed of two sub-layers of nickel and copper.

Abstract: This work deals with the development of new electrochemical ways to improve the cathode activity towards hydrogen evolution reaction. An in situ composite electrodeposition technique has been proposed to obtain the porous Ni+MoO₂ coatings by simultaneous co-deposition of Ni and MoO₂ onto a Cu substrate from a nickel plating bath containing 10 g dm^-3 of MoO₂ powder suspended by magnetic stirring. Electrodeposition was conducted at 30°C at the deposition current density of j_d = 50-250 mA cm^-2. SEM, EDS, and XRD measurements, were applied for physical and chemical characterization of the obtained coatings. It was found that by controlling the deposition conditions it was possible to obtain porous Ni+MoO₂ coatings containing from 10 to 15 at.% of MoO₂. The XRD results confirmed their diphase structure with a polycrystalline Ni matrix into which a crystalline component in the form of MoO₂ particles was built-in.

Abstract: The present work deals with the influence of sodium hypophosphite content in the plating bath on the chemical composition and structure of the obtained nickel electrocoatings. Electrodeposition of the Ni-P coatings was conducted under galvanostatic conditions at room temperature from the Watts type bath containing different amounts of sodium hypophosphite (0-30 g dm^-3). The chemical and physical characteristics of the obtained Ni-P deposits and comparable Ni coating, were performed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) methods. It was found that the addition of sodium hypophosphite as amorphizator to the Ni-plating bath influences both the structure and chemical composition of the obtained Ni electrodeposits. With increase in the content of sodium hypophosphite in the bath, surface morphology of the amorphous Ni-P coatings becomes more developed what is of key-importance for electroevolution of hydrogen on such electrodes.

Abstract: The Ni+Al+Ti composite coatings were prepared by the electrodeposition under the galvanostatic conditions at the deposition current denisty of j_dep = -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 800^oC 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, NiTi₂ and Ni₃Ti intermetallic phases. Thus obtained composite coatings may be useful in the applications as materials in the electrochemical processes.

Abstract: The Ni-Mo+MoO₂ composite coatings were obtained onto the steel substrate using an in situ co-deposition of a Ni-Mo alloy and MoO₂ powder particles maintained in suspension in the potassium pyrophosphate bath. To characterize the physical and chemical properties of the obtained coatings, SEM, EDS, and XRD methods, were applied. It was found that the co-deposited MoO₂ particles strongly influenced the properties of the Ni-Mo alloy coating. In comparison with the comparable Ni-Mo deposit containing 45 at.% of Mo, the presence of MoO₂ embedded into the composite coating diminished the content of Mo alloyed with Ni to 23 at.%. The electrodeposited Ni-Mo+MoO₂ composite coating obtained under proposed electrochemical conditions contained 25 at.% of MoO₂. The effect of the embedded MoO₂ as composite component on changes of the surface morphology and structure of the Ni-Mo binary alloy, was also discussed.

Abstract: The object of this work was to obtain the Ni+MoS₂ composite electrocoatings by in situ co-deposition of molybdenum (IV) sulfide particles (< 2 μm) and nickel from a suspension plating bath. Physical and chemical characterization of the coatings was carried out using SEM, EDS, and XRD methods. The chemical composition of these coatings of a diphase structure (Ni, MoS₂) was found to be dependent on the current density and temperature of electrodeposition. The optimal electrochemical conditions for embedding of the maximum amount of 26.4 wt.% of MoS₂ into the crystalline nickel matrix, were experimentally determined. The co-deposition process of MoS₂ particles and metallic nickel was discussed based on the adsorption mechanism. Such porous Ni+MoS₂ composite coatings can be proposed as electrode material for hydrogen electroevolution.

Abstract: The binary Ni-Mo alloy coatings of high Mo content were obtained on a steel substrate by dc current electrodeposition from alkaline solutions of pH 7.5-9.0. The pyrophosphate baths contained nickel chloride as a source of nickel ions, and dihydrate sodium molybdate supplied molybdenum. The constant current electrodpeposition at the deposition current denisty of j_d = 30-240 mA cm^-2 was performed at 60°C. The physical and chemical properties of the obtained electrocoatings were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray fluorescence (XRF) methods. All obtained Ni-Mo alloys reveal the amorphous structure, and their chemical composition strongly depends on the operating parameters of electrodeposition. The maximal content of Mo was found to be 45 at.%. The complicated mechanism of the induced co-deposition of the Ni-Mo alloy, has been discussed.

Abstract: This review work was focused on conventional and modern electrodes which play an important role in electrochemical systems. Among many types of existing electrode materials, some of the most prominent materials from the conventional (metals and their alloys, graphite and mixed metal oxides) and the modern (amorphous, modified and composite) electrodes, have been outlined. What is also discussed is the recent intensive usability of nanocrystalline electrodes of better properties than their microcrystalline equivalents, and development trend of electrode materials.