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Scintillation Secondary Electrons Detector for ESEM
Čudek, Pavel ; Kadlec, Jaromír (referee) ; Rek, Antonín (referee) ; Jirák, Josef (advisor)
The thesis deals with the scintillation secondary electron detector for environmental scanning electron microscope, its design and construction. The starting point was numerical simulation of electrostatic fields and electron trajectories in the electrode system of the detector and simulation of pressure distribution and flow of gases in different parts of the detector. On the basis of modeling and simulation, construction changes of the detector were gradually implemented. Detection efficiency of each version of the detector was determined by the method described in the work. This method enables to evaluate signal level from the captured images of the specimen, quality of images was stated from signal to noise ratio. The thesis describes the whole process of the detector improvement from initial state, when the detector operated with lower efficiency in the pressure range from 300 to 900 Pa, to final version that enables usage of the detector in the range from vacuum up to 1000 Pa of water vapors in the specimen chamber of the microscope.
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Diffusion of carbon in welding joints of low alloys and high alloy steels.
Zdvořáček, Marek ; Rek, Antonín (referee) ; Stránský, Karel (advisor)
Content of a document result measurements and analysis carbon´s diffusion at welding joint created from hight alloyed austenitic steel CSN 417242 and not alloyed steel CSN 412 050. Samples have been put throught isothermal anneal in a temperature range 500 °C up to 1100°C. Aim one´s effort to metalographyic quantification carburized and uncarburized zone. The next part of the document content measuring x-ray energy through microanalysis, where has been record course of a carbon disintegration and selected replacements elements at whole length of the welding joint . At the end of experimental part has been gauged course microhardness HV 0,05 at whole lenght of welding joint, from an acquired data has been chose the most optimal temperature of isothermal anneal, to produce the smallest structural notch.
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Scintillation Secondary Electrons Detector for ESEM
Čudek, Pavel ; Kadlec, Jaromír (referee) ; Rek, Antonín (referee) ; Jirák, Josef (advisor)
The thesis deals with the scintillation secondary electron detector for environmental scanning electron microscope, its design and construction. The starting point was numerical simulation of electrostatic fields and electron trajectories in the electrode system of the detector and simulation of pressure distribution and flow of gases in different parts of the detector. On the basis of modeling and simulation, construction changes of the detector were gradually implemented. Detection efficiency of each version of the detector was determined by the method described in the work. This method enables to evaluate signal level from the captured images of the specimen, quality of images was stated from signal to noise ratio. The thesis describes the whole process of the detector improvement from initial state, when the detector operated with lower efficiency in the pressure range from 300 to 900 Pa, to final version that enables usage of the detector in the range from vacuum up to 1000 Pa of water vapors in the specimen chamber of the microscope.
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Diffusion of carbon in welding joints of low alloys and high alloy steels.
Zdvořáček, Marek ; Rek, Antonín (referee) ; Stránský, Karel (advisor)
Content of a document result measurements and analysis carbon´s diffusion at welding joint created from hight alloyed austenitic steel CSN 417242 and not alloyed steel CSN 412 050. Samples have been put throught isothermal anneal in a temperature range 500 °C up to 1100°C. Aim one´s effort to metalographyic quantification carburized and uncarburized zone. The next part of the document content measuring x-ray energy through microanalysis, where has been record course of a carbon disintegration and selected replacements elements at whole length of the welding joint . At the end of experimental part has been gauged course microhardness HV 0,05 at whole lenght of welding joint, from an acquired data has been chose the most optimal temperature of isothermal anneal, to produce the smallest structural notch.
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Small-Volume Reactive Metal Alloys Prepared by Electron Beam Melting
Zobač, Martin ; Vlček, Ivan ; Zobačová, Jitka ; Rek, Antonín
The paper deals with the preparation of small volumes of reactive metal alloys (particularly titanium), utilizing an electron beam as the heat source. The melting was performed in a vacuum environment in order to prevent the compounds from reacting with atmospheric components. The water-cooled crucible avoids any contamination of the alloy, which would have otherwise arisen during the heating of the materials. The composition of resulting alloys were then investigated by energy-dispersive X-ray spectroscopy
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Depozice a zpracování uhlíkových nanotrubek připravených metodou PECVD za atmosférického tlaku
Kučerová, Z. ; Zajíčková, L. ; Jašek, O. ; Eliáš, M. ; Synek, P. ; Matějková, Jiřina ; Rek, Antonín ; Buršík, Jiří
Carbon nanotubes (CNTs) were synthesized by plasma enhanced chemical vapor deposition from mixture of argon, methane and hydrogen using microwave plasma torch at atmospheric pressure. Nanotubes grew on a complex substrate system consisting of silicon wafer, buffer layer and thin catalytic iron film. As confirmed by scanning electron microscopy (SEM), this deposition technique produces bundles or ropes of nanotubes covered by crust composed of catalytic particles, amorphous carbon and other impurities such as fullerenes or other carbon nanoparticles. Because many scientific and technological applications, as well as characterization techniques require individual nanotubes a great attention has to be paid to the post-deposition processing of the deposit. The nanotube bundle could be separated by ultrasonication of the deposit in organic or inorganic liquid. Most commonly used liquids are water or ethanol.
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