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Reactivity and controll of properties of metallic materials
Ševčíková, Barbora ; Opravil, Tomáš (referee) ; Zmrzlý, Martin (advisor)
The main objective of the bachelor thesis is to investigate the reactivity and corrosion of materials, namely of magnesium alloys. The theoretical part comprises a brief summary of the existing knowledge on magnesium alloys in the field of metal corrosion and a description of essential properties of the examined and utilized material. These are followed by the protection technology and a material resistance analysis including the specification of the processes applied in the experimental part. The thesis is focused on a comparison of the microstructure and corrosion resistance of magnesium alloys AZ31, AZ61 and AZ91. The applied methodology lied on metallography preparation of light optical micrographs of the surface-region cross-sections and on corrosion tests. These were carried out in 3% sodium chloride solution where the samples were immersed for the period of 8 hours.
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Reactivity and controll of properties of metallic materials
Kouba, Jan ; Richtera, Lukáš (referee) ; Zmrzlý, Martin (advisor)
This study deals with properties of aluminum alloys that are used in aerospace industry, particularly with alloy 2024. In introduction, the fundamental questions of metallurgy of aluminum alloys and their basic properties are summarized. Then the specific parameters of alloy 2024 are commented. It is followed by short summary of aluminum inorganic chemistry and chemistry of its compounds. Next chapter is an introduction to corrosion and description of its particular forms. The following section sets out a summary of results of recent research in the field of aluminum alloys corrosion, some details about corrosion product analysis and published results concerning hypochlorites, what is the key substance in experimental part. The experimental part is focused on the influence of temperature and concentration of sodium hypochlorite solution on corrosion of Al 2024, cladded by pure aluminum.
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Proposal of rehabilitation of hot water network
Lžičař, Jakub ; Voltr, Aleš (referee) ; Raclavský, Jaroslav (advisor)
The bachelor thesis deals with hot water recirculation systems. It is mainly focused on the malfunctions that appear in the system. Firstly, the text elaborates general information about hot water recirculation systems, hot water distribution and its parts. The next part of the thesis describes materials used in hot water recirculation systems. Then the text deals with the malfunctions of hot water recirculation systems, design and assembly of the pipes. These chapters are followed by the case study. The case study helps to imagine the way of possible future reconstruction. The time schedule of the realization was attached to the bachelor thesis.
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Study of plasmachemical reduction of corrosive layers on bronze
Miková, Petra ; Selucká, Alena (referee) ; Krčma, František (advisor)
One of the important stages of the human history is certainly Bronze Age, on our territory dated 1900 - 800 BC. At that times, it was produced many objects of bronze, such as swords, spears, daggers, ornaments, jewelry. These artifacts are now found by archaeologists in excavations around the whole world. During the years there was an exposure to various types of substances and the environment and result in extensive corrosion of the used materials. To better understand the culture and traditions of our ancestors, it is necessary to carefully eliminate the corrosion and thorough inspection of these subjects. In this work, we consider the model corrosion layers removal by reduction in low-temperature hydrogen plasma. Plasma chemical reduction method was developed during the eighties years of last century and currently is further rapidly improved. Unfortunately, the process mechanism is not yet precisely known. Preparation of model corrosion layers were as follows: bronze blocks (weight approximately 80 g) were sharpend by electrical grinding machine (used paper 280 and then 600). Thus treated samples were rinsed in ethanol, dryed by hot dryer and stored in plastic bags. A Petri dish was placed at the bottom of the desiccator and it was poured by 20 ml of concentrated hydrochloric acid. Above the bowl has punched ceramic grid, on which the samples were placed. Closed desiccator was placed in darkness at the ambient laboratory temperature. To accelerate the samples corrosion process in a desiccator, the samples were sprinkled with acid. Plasma chemical treatment was carried out in a cylindrical reactor of quartz glass with outer copper electrodes. The RF (13.54 MHz) capacitivelly coupled plasma was used for the samples treatment. For each sample have been selected specific conditions: power (50 - 300 W), pulse (duty cycle of 10 – 25 %) or continuous mode. The optical emission spectroscopy monitored dependence of OH- intensity during the reduction. The decrease to the 1/10 of the maximum value leads to end the experiment. Based on this criterion, the treatment time of samples was in the range of 30 - 80 minutes. Corrosion has been removed from 7 samples. All the samples were covered by corrosion deep green color with a clearly visible crystalline structure before their inserting into the reactor. After the treatment, the color was dark black, and after leaving the air began to surface green, in some samples was observed in white and yellow tint. Surface top layer was removed on samples 1 and 5, where spontaneous dropout was reached. The pulse mode with duty cycle of 10 % and the powers of 200 and 300 W were applied for these two samples. The surface layer of samples treated with pulsed mode of 25 % was easily removable by spatula. The work demonstrated the applicability of hydrogen RF plasma in pulsed mode for the corrosion removal from bronze samples. The further work will be focused on the optimal treatment conditions search.
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Examination of the activity and possibility verification ability of various types of corrosion inhibitors
Kroča, Michal ; Švehla, Vladimír (referee) ; Drochytka, Rostislav (advisor)
The aim of the work is to describe the degradation of concrete structures from the perspective of corrosion of steel reinforcement. The basis of a detailed survey and analysis of additives containing corrosion inhibitors, designed to improve the concrete matrix and increased protection of steel reinforcement. The essential part is a summary of the detection methods designed to verify the presence of inhibitors in reinforced concrete (direct method) or anti - corrosion effect on steel reinforcement (indirect method). Subsequently, to compare the available products in the market based on their characteristics and parameters, including prices and environmental point of view. From the data obtained is drawn optimization calculation, the output of which is to determine nevhodnějšího product for protection of steel reinforcement embedded in concrete structures, especially at a dosage rate specified by the manufacturer.
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Study of properties of electrolytically modified NaCl solutions.
Brázda, Lukáš ; Mika, Otakar Jiří (referee) ; Mašek, Ivan (advisor)
This work concentrates on the study of properties of NaCl solutions, prepared by electrolysis and their using for disinfection of water. Then it is focused on reporting on possibality for corrosin of metals, whice are used in water distribution. For study was used 0,25 mol/l, 0,1 mol/l, 0,05 mol/l NaCl solutions and input direct-current voltage for electrolysis was 6V a 12 V. During the electrolysis pH and conducitivity were measured. After the end of electrolysis free active chlorine and chlorides were determined on the time. For electrolysis was used diaphragm.
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Biodegradable Metal Materials for Bone Tissue Prothetics
Panáková, O.
This paper is focused on use of metal materials as a bone replacement. This paper also includes description of techniques of preparation, which involves selection of material and its procession. Furthermore there are stated results of experiments, this is EDAX, electrochemical experiments and monitoring the decay of the sample. Those are amended with pictures.
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Origin, composition and stability of copper pigments in wall paintings
Švarcová, Silvie ; Bezdička, Petr ; Hradil, David
Blue and green copper pigments occur in a wide range of chemically close, although mineralogically different species, which makes their proper identification nontrivial. Furthermore, they can be of various origins – natural, artificial or formed as a result of corrosion of another copper pigment. The degradation of copper pigments is a serious problem in case of artworks exposed to corrosive environment, such as wall paintings or exterior stone polychromes. In this paper, we document the variability of copper pigments used in history on examples of selected wall paintings. The problem of origin and stability of copper pigments in wall paintings is solved using advanced microanalytical investigation of paint layers together with the laboratory experiments. Microanalytical features documenting natural or artificial origin of copper pigments as well as their secondary changes caused by corrosive environment are shown and discussed.
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