Reaction synthesis of bulk Fe-Al intermetallic materials

Bakalářská práce se zabývá aluminidy železa. V literární studii jsou rozebrány nejznámější a nejpoužívanější intermetalické materiály, difúze a další možné technologie výroby. V experimentální části bylo použito nástřiku, který byl vyroben metodou cold spray. V této práci jsou rozebrány změny mikrostruktury v závislosti na teplotě žíhání. Práce obsahuje fotografie mikrostruktury a výsledky analýz z elektronového mikroskopu a z měření mikrotvrdosti.Bachelor’s thesis deals with iron aluminides. In literature analysis are the best known and the most widely used intermetallics materials, diffusion and other possible processing technologies of intermetallic materials. In experimental part was used sprayed coating. This sprayed coating was produced by cold gas-dynamic spray. In this thesis were analysed changes in microstructure of iron aluminides depending on annealing temperature. This thesis contains photographs of microstructure and analyses from electron microscopy and measurement of microhardness.

Reaction synthesis of bulk intermetallic materials from cold spray deposits from binary powders containing iron

Diplomová práce se zabývá studiem reakční syntézy materiálů Fe–Al, Fe–Cu a Fe–Ni, které byly vyrobeny metodou kinetického naprašování. V literární studii jsou popsány tyto jednotlivé systémy a pro každý tento systém je zde uveden a zároveň i popsán jeho rovnovážný binární diagram. Kromě tohoto je tady stručně vysvětlena difúze, Kirkendallův jev a další možné technologie výroby intermetalických materiálů. V experimentální části byly jednotlivé vzorky nástřiků žíhány a poté byly zkoumány změny mikrostruktury. Práce obsahuje fotografie mikrostruktury, výsledky mikrostrukturních a chemických analýz z elektronového mikroskopu, fázové analýzy difrakcí rentgenova záření a výsledky z měření mikrotvrdosti.This thesis deals with reaction synthesis of materials Fe–Al, Fe–Cu and Fe–Ni from cold spray. In literature analysis are introduced these systems and for each system there is brief description of binary equilibrium diagram. Furthermore here are some short explanations of diffusion, Kirkendall effect and other possible processing technologies of intermetallic materials. In experimental part, samples of sprayed materials were annealed and then microstructural changes were investigated. This thesis contains photographs of microstructure, results from scanning electron microscopy, X-ray, and measurements of microhardness.

Microstructural study of AZ91C magnesium alloy castings produced by investment casting in as-cast state and after heat treatment

In this article, the microstructure of AZ91C magnesium alloy castings produced by investment casting was investigated. Castings were studied in as-cast state and after T4 and T6 heat treatment. The identification of all phases in microstructure was carried out using a scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS) analysis. The influence of cooling rate after casting, temperature of solution annealing, temperature of artificial aging and cooling rate after heat treatment on the microstructural characteristics such as secondary dendrite arm spacing (SDAS) or grain size was studied. The SDAS analyses were carried out using a light microscopy with the subsequent image analysis. Except of Mg-Al solid solution and Mg17Al12 precipitates, the microstructure contains other phases based on Mg-Si and (Al,Si)-Mn in globular or needle morphology. The SDAS in as-cast state was measured and was of tens of micrometers, but after T4 heat treatment, the gran size exceeded 100 µm and the Mg17Al12 phase was still undissolved along the grain boundaries in samples with thicker wall dimension. After T6 heat treatment, continuous and discontinuous precipitates of Mg17Al12 phase were formed, most of them were nearby the grain boundaries proving the inhomogeneous distribution of Al atoms in solid solution after T4 heat treatment

The role of different high energy ball milling conditions of molybdenum powder on the resulting particles size and morphology

High energy ball milling is a powder processing method in which the powder particle size can be decreased to micrometer size in a relatively short period of time. This method is based on the friction and the high energy kinetic collisions between the balls and the trapped powder particles. The milling process is influenced by many process variables such as mainly the rotational speed, ball to powder weight ratio and processing time. In the present study, high energy ball milling process was performed for molybdenum powder using a high energy ball mill under different milling conditions varying the: (i) rotational speed from 600 to 800 rpm, (ii) ball to powder weight ratio of 100:3 and 100:6, (iii) milling time in the range of 10 to 60 minutes, (iv) process control agent using polyethylene glycol, and (v) milling atmosphere under air or nitrogen. The used initial molybdenum powder was of globular morphology and 100 µm in particle size. The powders after milling were characterized by a scanning electron microscope (SEM) and a laser diffraction size analysis. The particle size of milled powders was decreased down to 1.1 µm. As the most effective ball to powder weight ratio was found 100:6 with the milling speed of 800 rpm. The milling time played a crucial role for the refinement of particles up to 45 min, where the further milling had negligible effect on the overall trend of particle size evolution

The history of German and Czech minority schools in Plesna

Práce je věnována vývoji základní školy v Plesné v průběhu 20. století. Zabývala jsem se německou měšťanskou školou, která v Plesné vznikla sloučením evangelické a katolické školy. Ve třetí kapitole naleznete historii české menšinové školy v Plesné, která zde existovala paralelně s německou měšťanskou školou. Kapitola také nastiňuje složitou situace Čechů v pohraničí. Ve čtvrté kapitole jsem se věnovala vývoji školy po skončení 2. světové války, kdy v Plesné byla obecná škola a měšťanská střední školy, které byly v 50. letech sloučeny v jednu základní školu. Práce se hlavně věnuje historii školy, ale ukazuje i kulturně-politickou situaci v obci. V závěru práce je přepis rozhovoru s bývalými učitelkami, které na škole působily řadu let.ObhájenoThe work is dedicated to the development of an elementary school in the fungus in the 20th century. I dealt with the German town school, which was founded in Plesná merger of the Evangelical and Catholic schools. In the third chapter contains the history of the Czech minority schools in Plesná, which existed in parallel with the German town school. The chapter also outlines the difficult situation of the Czechs in the border region. In the fourth chapter is devoted to the development of school after the 2nd World War, when Plesná was an elementary school and middle school council, which were in the 50s merged into one elementary school. The work is essentially devoted to the history of the school, but also shows the political and cultural situation in the village. The conclusion is a transcript of an interview with a former teacher who worked for many years the school

The history of Chebsko in the didactic applications

Tato diplomová práce se zabývá využitím regionální historie Chebska ve vyučování dějepisu na 2. stupni základních škol prostřednictvím historických exkurzí. Práce je rozdělena na teoretickou a praktickou část. Teoretická část obsahuje historii vybraného regionu. V praktické části se nachází didaktická aplikace jednotlivých exkurzí. Celá práce má pomoci učitelům dějepisu při výuce regionálních dějin Chebska.ObhájenoThis master thesis deals with using history of region named Chebsko in History lessons at upper stage of primary schools through historical excursions. The thesis is divided into two parts, theoretical and practical. The theoretical part contains the history of the selected region. There is the didactic application of individual excursions in the practical part. The aim of the thesis is to help History teachers in the teaching of regional history this area Chebskp

Depozice hydroxyapatitu a trikalcium fosfátových povlaků ze suspenze pomocí plazmového nástřiku: Vliv rychlosti depozice

This research focuses on the deposition of hydroxyapatite (HA) and tricalcium phosphate (TCP) coatings produced by suspension plasma spraying (SPS) using in-house liquid feedstock suspensions. The work studied the effects of torch speed on the thickness, microstructure, and crystalline composition of the coatings. SPS allowed the deposition of HA and TCP coatings with thickness between 28 and 90 um. The coatings presented lamellar microstructure with complex porosity between the splats. Micropores ranging from 0.2 to 6 m and close mesopores, from 8 to 45 m, had a spherical morphology and were homogenously distributed within the coatings. Water evaporation during SPS allowed the retention of pure and crystalline HA coatings. In contrast, the presence of water molecules led to the formation of HA as a secondary phase in the TCP coatings, which formed -TCP as the major component due to the high temperature reached by the powder during deposition