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Nataliia Kovalska – Effect of the electrodeposition conditions on the morphology, composition and mechanical properties of Fe-P

The task of this research work is the development and application of environmental friendly electrolytes and electrodeposition processes for novel Fe based coatings. While ternary alloys are the final aim of this PhD thesis within the Marie Sklodowska-Curie ITN, SELECTA (G.A. No 642642) the focus laid on Fe-P alloys in the first step. The work includes the study of the underlying electrochemical relations such as monitoring the electrochemical current/ potential relations and optimization of electrolytes composition and electrochemical conditions (i. e: parameters, anodes, electrolyte flow) enabling the adjustment of the electrolyte composition and choice of the deposition parameters.

Various test samples were deposited, producing nanocrystalline and amorphous Fe-P alloy coatings. All chemicals used are fulfilling the Horizon 2020 guidline of the European Union. Whenever needed, the choice of materials and the electrolyte design will be revised and synthesis procedures will be modified in order to attain not only optimized material performance, but also meeting environmental requirements, such as using nonhazardous electrolytes, e. g. citrate and glycine based electrolytes. The coating properties and performance are optimized, with a surface morphology tailored from ultrasmooth to nanoporous to meet specific technological demands. The synthesis of porous metallic films using different approaches is another option.

This presentation will include the electrochemical set up and evaluation, the definition and testing of general plating parameters as well as the layer characterization in terms of corrosion, wear and mechanical properties. Modern plating techniques such as pulse and pulse reverse plating; in 2 and 3 electrode configurations will be used for layer optimization and tailoring of the micro-structure of the deposit. A possibility of formation of non-equilibrium alloys has been discovered and it has been found that a change in the plating conditions of the electrodeposition process results in a change of the phase structure. The suitable electrolyte composition for deposition of compact, non-powdery layers has been elaborated and the deposits of amorphous and crystalline Fe-P coatings from different electrolyte composition have been studied.

The resulting layers electrodeposited from the set of formulated galvanic electrolytes con-tained alloys with iron and as much as 5-17% of phosphorus from solution containing phosphite as phosphorus source. It was observed that the high phosphorus iron alloys have an amorphous structure and are more resistant against corrosion attack. The alloys are bright as metallic deposited but their reflectivity is lower than those of buffed coatings of pure iron. Phosphite is a satisfactory source of phosphorus for the electrodeposition of crystalline Fe-P deposits. The morphology structure was observed with scanning electron microscope (FEG-SEM Hitachi S-4800). The morphology determined using X-ray diffraction analysis (XRD Hitachi TM3000).