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Design of powder preheating for cold spray technology
Kalina, Jan ; Čupera, Jan (referee) ; Řehořek, Lukáš (advisor)
Cold spray is a technology that ranks among the thermal coatings. Its main idea is to prevent both the sprayed and the underlying material from reaching the melting temperature in order to reduce the level of surface oxidation. Cold spray is a relatively young technology that is still being researched. The effect of preheating the sprayed material on the material characteristics of the cold spray is one of the research questions. As part of this work, a device for preheating the powder to temperatures of up to 650 °C is designed in such a way as to minimize interference with the current construction of the Cold Spray workstation at the ÚMVI FSI BUT in Brno. The design is based on significant simplifications of the thermal model of the preheating device and heat losses. In the theoretical part, the reader was introduced to the history of Cold Spray, the effects of various technological parameters of Cold Spray on the resulting spray. Furthermore, the requirements for the preheater device were discussed, several variants of the device design were proposed, and the equations used for the device design were written. In the practical part, the required data for the design of the equipment is obtained for the required materials of the sprayed material, different temperatures, and other input parameters of the Cold Spray injection with the help of equations from the theoretical part. Based on them, the final design of the preheater device is compiled.
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Utilization of immiscible alloys for the SERS substrates
Klimšová, Zuzana ; Čupera, Jan (referee) ; Adam, Ondřej (advisor)
Surface-enhanced Raman spectroscopy (SERS) is an analytical method that enables the sensitive detection of biological molecules by enhancing the Raman signal on nanoporous metal substrates. This bachelor's thesis focuses on the preparation of immiscible alloys, specifically Cu75Ag25, using powder metallurgy and its application for SERS. The aim was to develop a fine-grained, two-phase microstructure suitable for SERS analysis. The process included mechanical alloying and isostatic pressing, followed by heat treatment to achieve the optimal microstructure. The results show that mechanical alloying and subsequent heat treatment create a fine two-phase microstructure suitable for further research as SERS substrates. The thesis also explores the possibility of preparing SERS substrates by casting and describes the structure of such prepared samples. The casting was conducted in a vacuum induction furnace, ensuring high material purity. Comparative studies between samples prepared by casting and powder metallurgy revealed differences in the resulting microstructures. The results indicate that powder metallurgy provides finer structures suitable for SERS applications, while cast samples exhibit coarser microstructures. Differential scanning calorimetry (DSC) was used to analyze the thermal properties of the samples, contributing to a better understanding of the kinetics of phase transformations. This thesis provides a comprehensive view of various methods for preparing SERS substrates and their impact on the resulting microstructures.
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Design of powder preheating for cold spray technology
Kalina, Jan ; Čupera, Jan (referee) ; Řehořek, Lukáš (advisor)
Cold spray is a technology that ranks among the thermal coatings. Its main idea is to prevent both the sprayed and the underlying material from reaching the melting temperature in order to reduce the level of surface oxidation. Cold spray is a relatively young technology that is still being researched. The effect of preheating the sprayed material on the material characteristics of the cold spray is one of the research questions. As part of this work, a device for preheating the powder to temperatures of up to 650 °C is designed in such a way as to minimize interference with the current construction of the Cold Spray workstation at the ÚMVI FSI BUT in Brno. The design is based on significant simplifications of the thermal model of the preheating device and heat losses. In the theoretical part, the reader was introduced to the history of Cold Spray, the effects of various technological parameters of Cold Spray on the resulting spray. Furthermore, the requirements for the preheater device were discussed, several variants of the device design were proposed, and the equations used for the device design were written. In the practical part, the required data for the design of the equipment is obtained for the required materials of the sprayed material, different temperatures, and other input parameters of the Cold Spray injection with the help of equations from the theoretical part. Based on them, the final design of the preheater device is compiled.
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Influence of heat treatment on microstructure of iron alloys with carbon
Hranický, Pavel ; Jan, Vít (referee) ; Čupera, Jan (advisor)
The work focuses on the influence of hardening on the structure of specially prepared iron alloys with carbon, with as little admixture of other elements. The effect of hardening is judged by the hardness of the resulting alloy. Two hardening temperatures, one optimal for the hardness of the resulting structure and one high, are used. Hardening takes place in water. Four different alloys are examined for which the carbon content ranges from 0.01 % to 3.00 %. The results are evaluated on the basis of hardness, microhardness and observation of the resulting structures and phases on the light and electron microscopy. Part of the thesis is a review summarizing the knowledge about the heat treatment of iron alloys with an emphasis on hardening.
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Multimaterial structures preparation by using deposition methods
Novotná, Hana ; Čupera, Jan (referee) ; Řehořek, Lukáš (advisor)
This master’s thesis deals with origin, structure and mechanical properties of architectured material. The theoretical part deals with composits and theory of architectured materials. Further, the cold spray technology is described and it is used to create the network of grooves in the architectured material. In the experimantal part the influence of groof geometry and profil on the mechanical properties of the resulting architectured material is researched. Microstructure and hardness of the samples were also examined.
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Heat treatment of aluminum alloys
Adami, Martin ; Čupera, Jan (referee) ; Němec, Karel (advisor)
This bachelor theses deals with description aluminium alloys, theirs applications in engineering and theirs heat treatment. First part is focused on pure aluminium and its production. The other one is about distribution aluminium alloys by possibility of precipitation hardening.
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Cold Spray coatings on high strength steels
Šesták, Stanislav ; Čupera, Jan (referee) ; Řehořek, Lukáš (advisor)
This bachelor’s thesis focuses on possible applications of the Cold Spray additive technology in context of high strength steels. The theoretical part of this work represents an extensive research on the topic of Cold Spray technology, showing connections between many of the mechanisms of this technology. This part also focuses specifically on high strength steels, their types, microstructures and properties. The experimental part of this work examines four samples of Cold Spray coatings on a high strength steel. After depositing these coatings, microstructure and microhardness analysis are provided.
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Effect of electron beam remeltin on binary mixtures deposited by the cold spray method
Novotný, David ; Řehořek, Lukáš (referee) ; Čupera, Jan (advisor)
This bachelor’s thesis deals with the effect of an electron beam remelting on binary mixtures of Fe-Al and Ni-Al, which were deposited by Cold spray. The Research study is focused on the basic principles of function and usage of the electron beam technology and the Cold spray method. Furthermore, binary systems of Fe-Al and Ni-Al are, along with their binary diagrams, also described in this part. In the Experimental part, the samples were remelted by an electron beam and consequently, the changes in microstucture were examined using electron and optical microscope.
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Microscopy: tool for material analysis
Pleskalová, Kateřina ; Řehořek, Lukáš (referee) ; Čupera, Jan (advisor)
This thesis deals with description of the microscopic techniques that are used to analyse materials. The introductory part briefly summarizes the history of microscopy. The first part of the thesis is focused on light microscopy and the confocal microscopy technique is more elaborated here. The second part of the thesis is focused on basic techniques of electron microscopy, which means transmission electron microscopy and scanning electron microscopy. At the end of each chapter, there is summarization of limits and advantages of these techniques. The preparation of metallographic samples is also briefly described for these microscopic techniques.
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Heat treatment of iron alloys with carbon
Kubíček, Antonín ; Štěpánek, Roman (referee) ; Čupera, Jan (advisor)
This thesis deals with the processes of heat treatment, their impacts on microstructure of iron alloys with carbon and their influence on hardness of these alloys. In the research part of this thesis are discussed the alloys, which are found within the Fe-Fe3C metastable system, principles and technologies of heat treatment processing with focus on the annealing, methods of microstructure examination and hardness measurement. In the experimental part is documented and evaluated the influence of various types of annealing on hypoeutectoid and hypereutectoid steels and the influence of graphitization on the hypoeutectic cast iron. The evaluation involves comparison of microstructures obtained by light and scanning electron microscopy and comparing the hardness in the green state and after annealing.
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