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Magnesium alloys
Březina, Matěj ; Šoukal, František (referee) ; Zmrzlý, Martin (advisor)
The study is focused on corrosion and corrosion protection of magnesium and magnesium alloys. The theoretical part describes properties of magnesium and magnesium alloys. It shows their advantages as well as their disadvantages and discusses ideal use for these alloys. The theoretical part analyses basic corrosion characteristics and typical corrosion processes. It deals with types of corrosion protection and ways of its use. The experimental part was focused on metallographic analysis and corrosion behavior of magnesium alloy AZ91. Metallographic methods were used for preparing AZ91 to corrosion tests. The experimental part compared corrosion rate and degradation of pure AZ91 and AZ91 with conversion coating (phosphate-permanganate) in 3,5% sodium chloride solution in times: 1, 8 and 48 hours.
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Fluoride conversion coatings on magnesium materials
Staněk, Jan ; Wasserbauer, Jaromír (referee) ; Březina, Matěj (advisor)
This bachelor thesis deals with the topic of corrosion protection of magnesium materials by conversion coatings. The aim is to characterize and compare properties of fluoride conversion coatings formed on wrought magnesium sample and magnesium sample prepared by powder metallurgy. Basic knowledge of pure magnesium, magnesium alloys, powder metallurgy, corrosion, and protection against it are described in the theoretical part. Recent results of corrosion protection by fluoride conversion coatings on magnesium materials are summarised in the recherché part. The experimental part is focused on preparation of fluoride conversion coatings on each type of sample by immersion in Na[BF4] molten salt and by dipping in hydrofluoric acid. Surface morphology and composition of coatings were characterized by EDS analysis and corrosion protection was evaluated by potentiodynamic measurements.
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Detection of P2P Networks
Březina, Matej ; Matoušek, Petr (referee) ; Tobola, Jiří (advisor)
This document deals with design, implementation and testing of software system for detecting p2p (peer-to-peer) networks based on combination of BPF prefiltering and POSIX regular expressions packet payload matching with known p2p protocol communications. The proposed detection system includes a database with some rules of most effuse p2p protocols in format resembling to definitions for L7-filter classifier. The application is implemented in C, runs in userspace and is targeted to all POSIX compatible platforms. The combination of detector with user attached QoS controlling is complete solution for traffic reduction of common p2p protocols.
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Preparation and properties of porous magnesium material
Ďubašák, Matej ; Kosár, Petr (referee) ; Březina, Matěj (advisor)
Magnesium is a lightweight metal suitable for various technical and biomedical applications due to its great strength-weight ratio and biocompatibility. The powder metallurgy (PM) of magnesium presents a modern method of porous magnesium processing, in which are reached specific mechanical properties influenced by high purity, material structure and controlled porosity during this process. This thesis deals with preparation and characterization of porous magnesium material which is prepared from a magnesium powder containing a particles with average size of 50 µm. The preparation process consists of powder pressing and sintering of green compacts. The properties of porous magnesium prepared by PM method depend on conditions of every individual process. The compaction pressure and sintering temperature were altered to optimize a preparation proces. There were examined mechanical properties (3 point bending, hardness) and optical properties (fractography and metallography). Obtained properties of porous magnesium prepared by PM were compared with technical literature.
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Preparation of Mg-Al based bulk materials via powder metallurgy
Jakůbek, Zdeněk ; Fintová, Stanislava (referee) ; Březina, Matěj (advisor)
This diploma thesis is focused on preparation of Mg-Al based bulk materials via powder metallurgy. The bulk materials were prepared by cold pressing, cold pressing followed by sintering, cold pressing followed by sintering and artificial aging, SPS (spark plasma sintering), SPS followed by solution annealing, SPS followed by solution annealing and artificial aging. The prepared materials were characterized in terms of microstructure and physical and mechanical properties. The properties of the prepared materials differed depending on the method of preparation and Al content. All materials after heat treatment were consisted of solid solution (Mg), intermetallic phase Mg17Al12 and MgO. The composition of the materials depended on Al content. Sintering by the SPS method resulted in material with better mechanical properties compared to materials whose first step of preparation was cold pressing.
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Preparation of Mg-Al-Ti bulk materials via powder metallurgy
Brescher, Roman ; Doskočil, Leoš (referee) ; Březina, Matěj (advisor)
This diploma thesis deals with research and preparation of bulk materials based on the Mg–Al–Ti system. The theoretical part summarizes the basic knowledge about magnesium alloys, focusing mainly on Mg–Al and Mg–Ti systems. Furthermore, basic information on powder metallurgy methods was included here, from the production of powder materials, through their compaction, to heat treatment and spark plasma sintering (SPS). The theoretical part ends with literature review on the current research of the Mg–Al–Ti system. In the experimental part, bulk materials based on the Mg–Al–Ti system was prepared using traditional methods of powder metallurgy, as well as using the SPS method. The microstructure of the material, elemental and phase composition was examined in this thesis. Subsequently, Vickers hardness and flexural strength were measured, and fractographic observation of the fracture surface was performed. It was found that the aluminum was completely dissolved during the heat treatment, but the titanium particles remained almost intact in the material and worked as a particulate reinforcement. Materials prepared by methods of conventional powder metallurgy showed increased porosity compared to materials prepared by the SPS, resulting in lower hardness and flexural strength. The hardness increased with increasing the amount of aluminum and titanium and with the amount of magnesium phase . Fractographic observation of the fracture surface suggests that a diffuse connection between the reinforcement and the matrix may have occurred after the sintering process.
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Preparation and characterization of fluoride conversion coating on magnesium material
Šmíd, Jakub ; Doskočil, Leoš (referee) ; Březina, Matěj (advisor)
This thesis deals with the preparation of fluoride conversion coating on magnesium material. The effect of the coating time on the formation of the coating was investigated and the corrosion resistance of the resulting coatings was measured. The theoretical part is focused on magnesium and its alloys, powder metallurgy, corrosion and protection against it. Furthermore, conversion coatings, especially fluoride coatings, and their applications are discussed. The review section focuses on the current state of research in the field of fluoride conversion coatings. The experimental part describes the procedures of sample preparation and coating formation. The effect of time on the formation of the coating is investigated by monitoring the microstructure, mainly by elemental analysis of the surface of the samples in the section. Furthermore, the corrosion resistance of the samples is measured by potentiodynamic polarization in NaCl solution.
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Study of the influence of alloying elements on the solubility of titanium in magnesium
Staněk, Jan ; Buchtík, Martin (referee) ; Březina, Matěj (advisor)
This master’s thesis deals with the study of the influence of aluminium and zinc on the solubility of titanium in magnesium. The theoretical part summarizes the basic knowledge about magnesium and magnesium alloys with a focus on systems containing aluminium, zinc and titanium. It also describes powder metallurgy technology, specifically the preparation, compaction and sintering of metal powders. The theoretical part ends with literature review on the current research of ternary and quaternary magnesium alloys. The experimental part focuses on the preparation of magnesium materials alloyed with titanium, zinc and aluminium by powder metallurgy and the basic structural and mechanical characterisation of the prepared materials. The effect of alloying elements and temperature on the solubility of titanium particles in magnesium was investigated. It was found that the main condition for the dissolution of titanium in magnesium is the temperature of 800 °C and the presence of aluminium, which initiates the reaction by forming intermetallic compounds with titanium. After incorporation of titanium into the material structure, new intermetallic compounds were formed with all elements not previously described in the literature, in addition to the structures described.
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Fluoride conversion coatings on magnesium materials
Staněk, Jan ; Wasserbauer, Jaromír (referee) ; Březina, Matěj (advisor)
This bachelor thesis deals with the topic of corrosion protection of magnesium materials by conversion coatings. The aim is to characterize and compare properties of fluoride conversion coatings formed on wrought magnesium sample and magnesium sample prepared by powder metallurgy. Basic knowledge of pure magnesium, magnesium alloys, powder metallurgy, corrosion, and protection against it are described in the theoretical part. Recent results of corrosion protection by fluoride conversion coatings on magnesium materials are summarised in the recherché part. The experimental part is focused on preparation of fluoride conversion coatings on each type of sample by immersion in Na[BF4] molten salt and by dipping in hydrofluoric acid. Surface morphology and composition of coatings were characterized by EDS analysis and corrosion protection was evaluated by potentiodynamic measurements.
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Optimization of surface pretreatment of steel and aluminum alloy for subsequent application of powder paint
Běloch, Martin ; Březina, Matěj (referee) ; Wasserbauer, Jaromír (advisor)
This diploma thesis deals with various procedures of surface pretreatment of steel and aluminum alloy for subsequent application of powder coating substance. The work begins with an overview of the general characteristics of the materials used. The core part of the work is then a summary of the individual methods of pretreatment that can be used to modify the material surface. A special chapter is devoted to methodologies for the application of powder substances. Before separate application, the sample must first be carefully pretreated to ensure removal of organic compounds (e.g. oils from primary processing - grinding, cutting), or dust impurities to ensure the correct barrier effect. After dividing the individual methods of surface preparation, a powder paint system with a total thickness of approximately 50 µm is applied to the test material. Samples with different surface pretreatments will be compared both in terms of mechanical properties and in terms of electrochemical properties.
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