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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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Cu-Fe-based immiscible alloys prepared by casting in a copper mold
Zabloudilová, Eva ; Němec, Karel (referee) ; Adam, Ondřej (advisor)
Immiscible alloys are characterized by a positive enthalpy of mixing. The resulting microstructure of these alloys is therefore made up of separated phases. The microstructure and mechanical properties of the material can be influenced not only by the cooling rate of the sample during casting, but also by the addition of alloying elements. This bachelor's thesis is devoted to alloys based on Cu-Fe, which is characterized by the presence of a miscibility gap. Ni, Mn, Co and Cr were selected as alloying elements. The alloys were prepared using Rapid solidification by casting into a copper mold and their microstructure, chemical composition and hardness were subsequently evaluated. Subsequently, the influence of individual elements on the resulting properties of the alloys was evaluated.
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Multicomponent Alloys Based on Immiscible Systems Prepared by Powder Metallurgy Route
Adam, Ondřej ; Svoboda, Jiří (referee) ; Sopoušek, Jiří (referee) ; Jan, Vít (advisor)
Immiscible alloys are a relatively well-known group of materials, however, they are still being intensively studied, especially from the point of view of heterogeneous materials with very good mechanical properties, but also electrical properties, for example. The main part of the research deals with cast materials, although in the case of immiscible alloys, there is a risk of liquid separation, which results in the loss of mechanical properties. This dissertation deals with the study of Cu-Fe-based immiscible alloys prepared by powder metallurgy methods. The theoretical part summarizes basic information about immiscible alloys, their microstructure, properties, and production options. The experimental part is first devoted to the choice of the suitable chemical composition of the studied alloys and subsequently to the optimization and influence of the mechanical alloying parameters on the properties of prepared powders. The main part of the experiments contains a complex structural, phase, and thermal analysis of Cu50Fe50 and Cu50(FeCo)50 alloys. In both alloys, a dual-phase ultrafine-grained microstructure was formed after sintering. The most significant of the presented results is the excellent resistance to grain coarsening compared to the other ultrafine-grained materials, where even after sintering at very high temperatures, the average grain size remained below 1 micron. The presumed reason is the immiscible nature of the studied alloys.
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