Browsing by Author "Alakushev M."

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    AN EFFECT OF NH4SCN ON DEPOSITION OF Sn-Co AND Sn-Ni POWDERS IN A FLUORIDE-CHLORIDE ELECTROLYTE
    (2020-01-01) Ignatova K.; Alakushev M.
    The cyclic voltammetry method is applied to investigate the kinetics of tin, cobalt and nickel deposition as well as that of Sn-Co and Sn-Ni alloy powders in a fluoride-chloride electrolyte. The content of the components used and that of an ammonium rhodanide (NH4SCN) additive are varied. The conditions of Sn-Co and Sn-Ni alloy powders deposition are determined in electrolytes of a different composition. It is shown that the addition of NH4SCN of about 5 g L−1−10 g L−1 favors the alloying. The further increase of the additive concentration facilitates the formation of smooth coatings greatly suppressing that of powders.
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    Effect of H3Po3 and Nah2Po2 in the electrolyte on the composition and microstructure of Ni-Co-P alloys
    (2019-01-01) Ignatova K.; Alakushev M.; Kozhukharov S.; Marcheva Y.; Vladimirova S.; Avdeev G.
    The effect of two phosphorus-containing additives (phosphorous acid, H3PO3 and sodium hypophosphite, NaH-2PO2) in modified Watt's electrolyte (pH = 2; 80°S) on the deposition kinetics, morphology, component and phase composition of Ni-Co-P coatings was studied. When only one of the studied additives is present in the solution, the P content in the coatings reaches maximum of 15 % and their structure is amorphous. The P and Ni incorporation in the coatings is facilitated when the electrolytes with prevailing concentrations of H3PO3 are used. The maximal P content (over 30 %) in the coatings was reached when both additives were present in the electrolyte. These coatings possess mixed structure with nano-dimensional amorphous phase and crystal hexagonal phase of solid solutions Ni2P and Ni2P-Co2P. The increasing of the current density causes P content decrement and the resulting crystal phase is tetragonal, composed by solid solutions of Ni3P and Ni3P-Co3P.
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    ELECTRODEPOSITION OF Sn-Co POWDERS BY STATIONARY AND PULSE MODE
    (2021-01-01) Ignatova K.; Lilova D.; Vladimirova L.; Alakushev M.
    Sn-Co powders with homogeneous distribution of components in powder particles were obtained by constant and pulse potential modes from a fluoride-chloride electrolyte. Morphology, elemental and phase compositions by SEM, EDX, SEM-Mapping andXDR analysis were investigated. Under stationary conditions, the potential increment leads to an increase in cobalt content from 3.6 wt.% to 56.4 wt.%, and to a structural alteration of the powders from network-shaped to a dendritic form with an average particle size between 15 and 30 µm, depending on the total metal concentration. The powders, obtained by pulse mode at a lower pulse frequency (100 Hz), contain particles with an irregular dendritic structure, characterized by the greatest thickness of the main axes of the dendrites. Increasing the pulse frequency to 1000 Hz results in a finer dispersed structure (r < 10 µm) and the cobalt content achieves 70.5 wt.% under these conditions. The obtained Sn-Co powders are mixed structures of amorphous phase and inclusions of microcrystalline phases of tetragonal β-Sn, hexagonal α-Co, CoO and SnO2 and only in stationary mode an additional phase of SnF2 exists.
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    INFLUENCE OF ELECTROLYTE COMPOSITION AND ITS TEMPERATURE ON THE PROPERTIES OF Sn-Co POWDER
    (2021-01-01) Alakushev M.; Ignatova K.
    The conditions for electrodeposition of Sn-Co powders in a fluoride-chloride electrolyte with different Co2+/Sn2+ ratios have been determined. Both, the effect of electrolyte temperature and the value of the initial current density on the morphology, component and phase composition of Sn-Co powders, were investigated. A wide range of powder compositions, depending on the increase of Co2+/Sn2+ ratio, was obtained - from 7 wt. % Co to over 85 wt. % Co. The deposited Sn-Co powders are characterized by a very diverse morphology, which varies from needle-like and cross-linked in the Sn-enriched powders to typically dendritic in Co-enriched ones. By increasing the electrolyte temperature from 20oC to 60oC, the share ofparticles with a size of about 5 - 10 µm reaches above 50 %. The main elements (tin, cobalt and oxygen) are evenly distributed in the structure of the individual particles.