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    PREPARATION OF PEO COATINGS ON AZ31 MAGNESIUM ALLOY IN THE PRESENCE OF HUMIC ACID
    (Tanger Ltd, 2024-06-06) Doskočil, Leoš; Šomanová, Pavlína; Wasserbauer, Jaromír; Kajánek, Daniel; Buchtík, Martin
    Magnesium materials are desirable for surface treatment because of their low corrosion resistance. The preparation of coatings on AZ31 alloy by plasma electrolytic oxidation (PEO) in a bath with and without humic acid was investigated. The coatings were characterized using a scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR). The corrosion properties were tested using the potentiodynamic polarization method in 0.15 M NaCl. The results show that the PEO coatings had significantly higher corrosion resistance than the AZ31 alloy. The PEO coating prepared in the presence of 5 mg/l humic acid (10 min deposition) appeared to have slightly better corrosion resistance than the PEO coating prepared in the absence of humic acid.
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    EFFECT OF GLYCEROL-2-PHOSPHATE AND EDTA ON THE PREPARATION OF CAP COATING ON AZ31 MAGNESIUM ALLOY UNDER NEUTRAL pH CONDITION
    (Tanger Ltd, 2024-06-06) Doskočil, Leoš; Horák, Tomáš; Wasserbauer, Jaromír; Wolanský, Petr; Buchtík, Martin
    Magnesium and its alloys are very promising candidates for the development of degradable implants, but their application is limited by high corrosion rates. The corrosion resistance of magnesium materials can be increased by suitable surface treatment. In this work, calcium phosphate (CaP) coatings were hydrothermally prepared with and without organic additives (ethylenedinitrilotetraacetic acid, 2-glycerol- phosphate) on AZ31 alloy with Mg(OH)(2) interlayer. The morphology was dependent on the additive used and the composition of the coatings corresponded to hydroxyapatite. The corrosion resistance of the coatings in 0.15 M NaCl was much higher than that of AZ31 alloys, but the protective function was mainly attributed to the Mg( OH)(2) interlayer. The CaP coating could mainly provide biocompatibility.
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    PREPARATION OF Mg-Al LDH COATING ON AZ31 MAGNESIUM ALLOY UNDER MILD CONDITIONS
    (Tanger Ltd, 2024-06-06) Šomanová, Pavlína; Buchtík, Martin; Wasserbauer, Jaromír; Doskočil, Leoš
    Magnesium and its alloys are interesting materials but they have low corrosion resistance. Magnesium-aluminium double layered hydroxide (Mg-Al LDH) coatings were prepared on AZ31 alloy by hydrothermal method at 50 degrees C, 70 degrees C and 90 degrees C at different reaction times (3 h, 6 h and 24 h). The coatings were characterized by scanning electron microscope (SEM) with energy dispersive X-ray spectroscope (EDS), Xray diffraction (XRD) and potentiodynamic polarization measurements in 0.15 M NaCI. The optimum conditions for the preparation of the coating included a temperature of 90 degrees C and a reaction time of 24 h, as the coating was composed of Mg-Al LDH and exhibited the highest corrosion resistance.
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    Biaxial porosity gradient and cell size adjustment improve energy absorption in rigid and flexible 3D-printed reentrant honeycomb auxetic structures
    (Elsevier, 2024-06-01) Štaffová, Martina; Ondreáš, František; Žídek, Jan; Jančář, Josef; Lepcio, Petr
    This paper compares different uniaxial and biaxial graded designs of auxetic reentrant honeycomb structures to enhance their mechanical properties, especially the specific energy absorption under compressive load. The lattice structures were 3D printed using the vat photopolymerization masked-stereolithography technique from two different materials - tough (OR) and flexible (FR). The results were evaluated from a material and structural point of view, investigating the effect of porosity, cell number, size, graded design, and fracture mode. The universally best energy-absorbing performance was found in a biaxially graded structure with a center-wise location of the highest local porosity. Depending on the used resin, its energy absorption capacity was up to 2-3 times enhanced compared to a reference uniform-porosity auxetic design. The presented data constitutes a fundamental understanding of auxetic structures and identifies practical approaches for tuning the auxetic structures' performance regarding their mechanical response. Finally, this study demonstrates the potential of shape versatility offered by 3D printing and other additive manufacturing techniques.
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    Antimycotic effects of the plasma gun on the yeast Candida glabrata tested on various surfaces
    (WILEY-V C H VERLAG GMBH, 2024-07-04) Trebulová, Kristína; Orel, Inna; Pouvesle, Jean Michel; Robert, Eric; Rouillard, Amaury; Stancampiano, Augusto; Hrudka, Jan; Menčík, Přemysl; Kozáková, Zdenka; Měšťánková, Zuzana; Kužmová, Darina; Paličková, Ivana; Čížek, Alois; Krčma, František
    This work focuses on the antimycotic effects of the plasma gun as a potential tool for the treatment of superficial infections. Candida glabrata was chosen as a model microorganism. The preliminary tests have been done on the agar plates to establish the basic plasma parameters. To render this research more appropriate to the real application, more complex inoculation substrates, pork skin and 3D-printed models of the dog ear canal have been used. The results of this work confirm the high efficiency of cold plasma in the inhibition of yeasts on different surfaces and will lead to further experiments.