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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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    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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    Nondestructive evaluation of the interface between ceramic coating and stainless steel by electromagnetic method
    (IOP Conference Series, 2016-09-02) Savin, Adriana; Steigmann, Rosina; Iftimie, Nicoleta; Nový, František; Vizureanu, Petrica; Craus, Mihail-Liviu; Fintová, Stanislava
    Protecting coatings as thermal barrier coating (TBC) are used for yield improvement of equipment working at high temperature. Zirconia doped with yttria ceramics are considered a good TBC material due of its low thermal conductivity, refractory, chemical inertness and compatible thermal expansion coefficient with metallic support. The paper proposes the use of an electromagnetic method for evaluation of coatings on stainless steel using a sensor with metamaterial lens and comparison of the results with those obtained by complementary methods.
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    Characterization of Electroless Ni–P Coating Prepared on a Wrought ZE10 Magnesium Alloy
    (MDPI, 2018-03-07) Buchtík, Martin; Kosár, Petr; Wasserbauer, Jaromír; Tkacz, Jakub; Doležal, Pavel
    Electroless low-phosphorus Ni–P coating was deposited on a wrought ZE10 magnesium alloy including an advanced pre-treatment of the material surface before deposition. Uniform Ni–P coating with an average thickness of 10 µm was formed by 95.6 wt % Ni and 4.4 wt % P. The content of Ni and P was homogeneous in the entire cross-section of the coating. Applying the Ni–P coating to the magnesium substrate, the surface microhardness increased from 60 ± 4 HV 0.025 to 690 ± 30 HV 0.025. Using the scratch test, it was determined that deposited Ni–P coating exhibits a high degree of adhesion to the magnesium substrate. Electrochemical corrosion properties of Ni–P coating were analyzed using the polarization tests in 0.1 M NaCl, while the deposited Ni–P coating showed an improvement of the corrosion resistance when compared to the ZE10 magnesium alloy. Using the scanning electron microscopy analysis, it was determined that the fine morphology of the deposited Ni–P coating did not contain visible microcavities. The absence of macrodefects due to the adequate pre-treatment before coating was reflected on the mechanism of the coated ZE10 degradation in a 0.1 M NaCl solution.
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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.