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Improvement of corrosion properties of MgAl-LDH coating on AZ31
Gromov, Egor ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
The subject of this bachelor thesis was the preparation and characterization (morphological and chemical) of layered double hydroxide (LDH) coatings with and without the addition of organic substances on AZ31 magnesium alloy treated by plasma electrolytic oxidation (PEO) to improve the corrosion resistance of the alloy. The samples were prepared at three different temperatures (100, 110 and 120 °C) for 4 or 24 h to determine the effect of the conditions on the quality of the LDH coating formed. For testing, samples were prepared with the addition of salicylic and tartaric acid. The corrosion resistance of the AZ31 alloy with coatings was described using the potentiodynamic polarization method and compared with the AZ31 alloy containing PEO coating. This was followed by a description of the morphological and elemental composition by SEM-EDS analysis, which confirmed the formation of MgAl-LDH. The best corrosion properties, according to the PDP method, were exhibited by the sample without the addition of acids, prepared at 100 °C for 4 h, but the greatest thickness of the LDH coating was obtained under conditions of 120 °C and 24 h. The samples with the addition of salicylic acid or tartaric acid showed poorer corrosion resistance compared to the LDH coatings prepared in the absence of organic substances.
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Effect of EDTA on properties of layered double hydroxides deposited on Mg substrates
Tkadlec, Tomáš ; Doskočil, Leoš (referee) ; Buchtík, Martin (advisor)
The subject of the bachelor's thesis was the preparation and characterization of MgAl LDH coatings on Mg substrates prepared by powder metallurgy with the aim of improving corrosion resistance. The coatings were prepared in a reaction mixture with various concentrations of EDTA. The corrosion resistance of the coated samples was analyzed using potentiodynamic measurements and compared with uncoated Mg. The sample prepared with a 5mM concentration of EDTA in the reaction mixture showed the best corrosion resistance. Higher concentrations of EDTA led to a deterioration of corrosion properties. The morphology and structure of the coatings and the elemental composition were described using electron microscopy and EDS analysis. Phase analysis was performed using X-ray diffraction (XRD). It was demonstrated that EDTA affects the structure of LDH coatings. The concentration of EDTA above 25mM in the reaction mixture results in the formation of Al(OH)3 coatings.
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Preparation and characterization of layered double hydroxides on Mg substrates prepared by powder metalurgy
Kobzinková, Eliška ; Doskočil, Leoš (referee) ; Buchtík, Martin (advisor)
This thesis deals with the preparation and characterization of double-layered hydroxides (LDH) on Mg substrates prepared by powder metallurgy. The theoretical part deals with magnesium, magnesium powder metallurgy, and LDH coatings and methods of their preparation with a focus on MgAl-LDH. The theoretical part is concluded with a research study of current research in the field of preparation of LDH coatings on magnesium substrates and the influence of process parameters on the properties of coatings. The experimental part covers the process of optimization of MgAl-LDH on Mg samples prepared by powder metallurgy. In particular, the morphology and structure of the coatings and their elemental composition were evaluated. The evaluation was carried out using a scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS). The optimized MgAl-LDH coatings were also evaluated for electrochemical corrosion properties by potentiodynamic tests in Hank's solution corrosion environment and phase analysis by X-ray diffraction (XRD).
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Preparation of yttrium-based coating to increase the corrosion resistance of AZ31 magnesium alloy
Kolařík, Václav ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
The subject of the bachelor thesis was the preparation and characterization (morphological and chemical) of coatings based on layered double hydroxides (LDH) with yttrium on AZ31 magnesium alloy to improve the corrosion resistance of the alloy. The coatings were prepared under mild and hydrothermal conditions and the synthesis was supported by thermodynamic assumptions. The corrosion resistance of the AZ31 alloy with coatings was described by potentiodynamic measurements and compared with the pure AZ31 alloy. This was followed by a description of the morphological and elemental composition through SEM-EDS analysis, and confirmation of the formation of the structures observed by this method was performed through FTIR analysis. The best coating prepared under mild conditions was a sample prepared at 90 °C for 24 h with a yttrium concentration of 0,05 M and under hydrothermal conditions it was a coating prepared at 120 °C for 30 h with a yttrium concentration of 0,075 M. SEM-EDS and FTIR analysis did not show the formation of MgY-LDH but the formation of Mg(OH)2. Yttrium was minorly represented in the coatings where it could be present, e.g. as Y(OH)3. Yttrium was shown to have a positive effect on the preparation of the coatings compared to the sample prepared without yttrium under the same reaction conditions.
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Preparation of yttrium-based coating to increase the corrosion resistance of AZ31 magnesium alloy
Kolařík, Václav ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
The subject of the bachelor thesis was the preparation and characterization (morphological and chemical) of coatings based on layered double hydroxides (LDH) with yttrium on AZ31 magnesium alloy to improve the corrosion resistance of the alloy. The coatings were prepared under mild and hydrothermal conditions and the synthesis was supported by thermodynamic assumptions. The corrosion resistance of the AZ31 alloy with coatings was described by potentiodynamic measurements and compared with the pure AZ31 alloy. This was followed by a description of the morphological and elemental composition through SEM-EDS analysis, and confirmation of the formation of the structures observed by this method was performed through FTIR analysis. The best coating prepared under mild conditions was a sample prepared at 90 °C for 24 h with a yttrium concentration of 0,05 M and under hydrothermal conditions it was a coating prepared at 120 °C for 30 h with a yttrium concentration of 0,075 M. SEM-EDS and FTIR analysis did not show the formation of MgY-LDH but the formation of Mg(OH)2. Yttrium was minorly represented in the coatings where it could be present, e.g. as Y(OH)3. Yttrium was shown to have a positive effect on the preparation of the coatings compared to the sample prepared without yttrium under the same reaction conditions.
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