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Potential of AZ series magnesium alloys for ureteral stent manufacturing
Trnková, Zuzana ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
This master's thesis focuses on investigating the potential of magnesium alloys AZ31 and AZ91 for the production of ureteral stents. Potentiodynamic polarization (PDP) and electrical impedance spectroscopy (EIS) methods were used for electrochemical testing. Surface and microscopic analysis were conducted using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). Immersion tests were used to characterize the corrosion solution and surface of AZ31 and AZ91 alloys. Fourier transform infrared spectroscopy (FTIR) with ATR module was used to determine the corrosion products on the surface of the alloys. The results showed that the AZ series alloys have potential for ureteral stent manufacturing, with AZ31 appearing to be more suitable than AZ91 as it provides more stable corrosion protection in the long term and the corrosion products do not form large particles that could lead to undesirable encrustation. Urea has also been shown to have a negligible impact on corrosion of AZ31 and AZ91 at lower concentrations, but at higher concentrations a significant impact on corrosion has been observed (especially in the case of AZ31).
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Malonate and succinate as potential corrosion inhibitors of AZ31 magnesium alloy in 0.9% NaCl
Tkáčová, Karolína ; Buchtík, Martin (referee) ; Doskočil, Leoš (advisor)
The aim of this work was to evaluate the inhibitory effects of malonic acid, succinic acid and their mixture in a 0,15M NaCl solution at pH 7 on AZ31 magnesium alloy. The theoretical part focuses on magnesium, its alloys and alloying elements. It also discusses magnesium corrosion in aqueous environments and the influence of microstructure on corrosion. The final section is dedicated to corrosion inhibitors and small aliphatic acids. The practical part of this work involves potentiodynamic measurements, immersion tests, and subsequent analysis of alloy surfaces. The following concentrations of acids were chosen for studying inhibitory properties: 0.025M, 0.05M, 0.075M, and 0.1M, as well as various mixtures of both acids. Suppression of corrosion was observed in immersion tests for both acids individually and in their mixture. The best inhibitory results in both potentiodynamic polarization (PDP) analysis and immersion tests were achieved with a mixture of 0.025M malonic acid solution and 0.075M succinic acid solution.
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Use of acoustic emission technology to assess corrosion of materials
Procházka, Adam ; Vašíková, Simona (referee) ; Binar, Tomáš (advisor)
The thesis deals with the description of acoustic emission as a non-destructive testing method and its use in the detection of material corrosion. The first part describes the theoretical principles dealing with the explanation of what acoustic emission is, how it is defined according to the standard, what are the types of acoustic emission and how it is tested. It then discusses corrosion, the types of corrosive environments where corrosion occurs and the types of corrosion tests. It also describes where acoustic emission has been used in practice and what experiments it has been used for in terms of material monitoring. The next part of the paper describes the experiment of acoustic emission measurement on grey cast iron samples, describes the fabrication of the samples, the use of corrosion protectors, and the placement of the samples in a condensation chamber for continuous testing. The last part is the evaluation of the results .
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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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Surface cleaning of archaeological objects by plasma generated in water solutions
Tihonová, Jitka ; Grossmannová, Hana (referee) ; Krčma, František (advisor)
This bachelor thesis is focused on the plasma surface treatment of historical ceramics by low temperature electrical discharges in water solution. Four samples were chosen - two of the Lusatian Urnfields Culture and two of Anabaptist Faience. The treatment was done at minimum power of the power supply. Stainless steel electrode and a specially designed electrode system with wolfram wire in the quartz glass capillary were used for generation of discharge using an audio frequency power supply. Elemental analysis by scanning electron microscopy (SEM) was done before and after the treatment and values were compared with the elemental analysis of material’s core. Samples of the Lusatian Urnfields Culture were successfully treated without any surface damage. The first one of samples of Anabaptist Faience was damaged. The experiment was repeated on the glass to determine the cause. It was find out that damage was probably caused by thermal stress. The second one of Anabaptist Faience was already treated without damage. Next research will be focused on determining specific conditions of the power supply, modification of water solution and modification of sample’s surface for the most efficient ancient ceramics cleaning.
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Determination of climatic factor on the degradation of various solar cells types
Peroutka, Tomáš ; Jandová, Kristýna (referee) ; Vaněk, Jiří (advisor)
In this work are discussed photovoltaic cells. There are also discussed basic concepts of radiation source for solar cells. Also mentioned the issue of semiconductors and even the history and evolution of the solar cells. A large part deals with possibilities of photovoltaic cells degradation. In one chapter is an attempt to bring some types of photovoltaic cells and a description of the production of these modules.The practical part deals with photovoltaic modules degradation and its evaluation. Following part compares measured values with the values provided by producer of photovoltaic modules.
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Evaluation of electrochemical characteristics of AZ61 wrought magnesium alloy
Kotek, Jakub ; Minda, Jozef (referee) ; Fintová, Stanislava (advisor)
This work is focused on evaluation the electrochemical characteristics of AZ61 wrought magnesium alloy. Electrochemical impedance spectroscopy and potentiodynamic tests were used to evaluate the electrochemical characteristic of the alloy. Values of polarization resistance were determined with electrochemical impedance spectroscopy. Values of corrosion potential and corrosion current density were determined with potentiodynamic tests. Sodium chloride solution at a concentration of 0.1 mol·dm-3 was used as a corrosion medium. Outcome of this work is to estimate an influence of fabrication, chemical composition and surface treatment on the corrosion properties of magnesium alloy.
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Biodegradable metal materials for bone tissue prosthetics
Panáková, Olga ; Vondrák, Jiří (referee) ; Sedlaříková, Marie (advisor)
This paper is focused on use of metal materials as a bone replacement. For coherence of this text is necessary theoretical preamble which is consisting of describing metal properties, aimed particularly at corrosion, valuation methods of disposition to corrosion and mainly corrosion itself. This paper also includes description of techniques of preparation, which involves selection of material and its procession. Furthermore there are stated results of experiments. Those are amended with pictures.
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Stainless steel for steam sterilizer components
Hradil, David ; Němec, Karel (referee) ; Pacal, Bohumil (advisor)
The thesis titled "Stainless steel for steam sterilizer components" is focused on the selection of the optimum stainless steel for the device, in our case, pure steam generator. In this thesis are introduced the main mechanisms and types of corrosion. There are divided and characterized by various types of stainless steels. The choice of material is carried out with regard to the working environment and the technological possibilities of the individual types of stainless steels.
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Surface treatments in mechanical engineering
Čudová, Monika ; Kubíček, Jaroslav (referee) ; Žák, Ladislav (advisor)
The project was developed within the bachelor study presents experimental verification of two given varnishes. They are applied on a specially made plate. It was based on literary studies of corrosion coatings issues - coatings and practical tests. The samples were painted and tested according to the standards. The samples were tested on adhesion of varnishes, bending test and salt stray test. Finally all tests were evaluated.
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