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    Characterization of Powder Metallurgy Processed Pure Magnesium Materials for Biomedical Applications
    (MDPI AG, 2017-10-31) Březina, Matěj; Minda, Jozef; Doležal, Pavel; Hasoňová, Michaela; Fintová, Stanislava; Zapletal, Josef; Wasserbauer, Jaromír; Ptáček, Petr
    Magnesium and its alloys are modern lightweight materials applicable in a wide range of industrial fields from aerospace and automotive to biomedical applications. Its main advantages are a good strength to weight ratio and biocompatibility in combination with biodegradability. However, due to the high reactivity of pure Mg and the mechanical properties, not really sufficient for engineering applications, mainly magnesium alloys are used. Good mechanical properties of magnesium and its alloys can be furthermore significantly upgraded by decreasing the grain size, nowadays performed mainly via severe plastic deformation (SPD) techniques, powder metallurgy (PM) processing or by a combination of both methods
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    Influence of the Composition of the Hank’s Balanced Salt Solution on the Corrosion Behavior of AZ31 and AZ61 Magnesium Alloys
    (MDPI, 2017-11-01) Tkacz, Jakub; Slouková, Karolína; Minda, Jozef; Drábiková, Juliána; Fintová, Stanislava; Doležal, Pavel; Wasserbauer, Jaromír
    namic tests and electrochemical impedance spectroscopy. The influence of the solution composition and material surface finish was examined also through the analysis of corrosion products created on the samples’ surface after electrochemical measurements in terms of scanning electron microscopy using energy-dispersive spectroscopy. Obtained data revealed the differences in the response of the magnesium alloys to enriched Hank’s Balanced Salt Solution—HBSS+ (with Mg2+ and Ca2+ ions) and Hank’s Balanced Salt Solution—HBSS (without Mg2+ and Ca2+ ions). Both examined alloys exhibited better corrosion resistance from the thermodynamic and kinetic point of view in the enriched HBSS+. AZ61 magnesium alloy reached higher values of polarization resistance than AZ31 magnesium alloy in both the used corrosion solutions. Phosphate-based corrosion products were characteristic for the AZ31 and AZ61 alloys tested in the HBSS (without Mg2+ and Ca2+ ions). The combination of phosphate-based corrosion products and clusters of MgO and Mg(OH)2 was typical for the surface of samples tested in the enriched HBSS+ (with Mg2+ and Ca2+ ions). Pitting corrosion attack was observed only in the case of enriched HBSS+.
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    Improvement of AZ91 Alloy Corrosion Properties by Duplex NI-P Coating Deposition
    (MDPI, 2020-03-17) Wasserbauer, Jaromír; Buchtík, Martin; Tkacz, Jakub; Fintová, Stanislava; Minda, Jozef; Doskočil, Leoš
    The corrosion behavior of duplex Ni-P coatings deposited on AZ91 magnesium alloy was studied. The electroless deposition process of duplex Ni-P coating consisted in the preparation of low-phosphorus Ni-P coating (5.7 wt.% of P), which served as a bond coating and high-phosphorus Ni-P coating (11.5 wt.% of P) deposited on it. The duplex Ni-P coatings with the thickness of 25, 50, 75 and 100 µm were deposited on AZ91 magnesium alloy. The electrochemical corrosion behavior of coated AZ91 magnesium alloy was investigated by electrochemical impedance spectroscopy and potentiodynamic polarization method in 0.1 M NaCl. Obtained results showed a significant improvement in the corrosion resistance of coated specimens when compared to uncoated AZ91 magnesium alloy. From the results of the immersion tests in 3.5 wt.% NaCl, 10% solution of HCl and NaOH and 5% neutral salt spray, a noticeable increase in the corrosion resistance with the increasing thickness of the Ni-P coating was observed.
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    Comparison of Electrochemical Methods for the Evaluation of Cast AZ91 Magnesium Alloy
    (MDPI AG, 2016-11-15) Tkacz, Jakub; Minda, Jozef; Fintová, Stanislava; Wasserbauer, Jaromír
    Linear polarization is a potentiodynamic method used for electrochemical characterization of materials. Obtained values of corrosion potential and corrosion current density offer information about material behavior in corrosion environments from the thermodynamic and kinetic points of view, respectively. The present study offers a comparison of applications of the linear polarization method (from 100 mV to +200 mV vs. EOCP), the cathodic polarization of the specimen (100 mV vs. EOCP), and the anodic polarization of the specimen (+100 mV vs. EOCP), and a discussion of the differences in the obtained values of the electrochemical characteristics of cast AZ91 magnesium alloy. The corrosion current density obtained by cathodic polarization was similar to the corrosion current density obtained by linear polarization, while a lower value was obtained by anodic polarization. Signs of corrosion attack were observed only in the case of linear polarization including cathodic and anodic polarization of the specimen.
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    Preparation and Characterization of Zinc Materials Prepared by Powder Metallurgy
    (MDPI, 2017-09-27) Hasoňová, Michaela; Doležal, Pavel; Fintová, Stanislava; Březina, Matěj; Zapletal, Josef; Wasserbauer, Jaromír
    The use of zinc-based materials as biodegradable materials for medical purposes is offered as a possible alternative to corrosion-less resistant magnesium-based materials. Zinc powders with two different particle sizes (7.5 µm and 150 µm) were processed by the methods of powder metallurgy: cold pressing, cold pressing followed by sintering and hot pressing. The microstructure of prepared materials was evaluated in terms of light optical microscopy, and the mechanical properties were analyzed with Vickers microhardness testing and three-point bend testing. Fractographic analysis of broken samples was performed with scanning electron microscopy. Particle size was shown to have a significant effect on compacts mechanical properties. The deformability of 7.5 µm particle size powder was improved by increased temperature during the processing, while in the case of larger powder, no significant influence of temperature was observed. Bending properties of prepared materials were positively influenced by elevated temperature during processing and correspond to the increasing compacting pressures. Better properties were achieved for pure zinc prepared from 150-µm particle size powder compared to materials prepared from 7.5 µm particle size powder.