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Charpy tests of load measuring pins from ČSN 19 312 material
Šperl, Martin ; Gajdoš, Lubomír ; Bejdl, Jan
Charpy tests of load measuring pins from ČSN 19312 steel were carried out at the temperature 20 °C, 0 °C, -20 °C, and\n-40 °C with the aim to verify that Charpy notch toughness of the pins keeps its average magnitude even at -40 °C. The results showed that the steel did not exhibit a typical S-type transit curve in the temperature range 20 °C ÷ -40 °C due to which the Charpy notch toughness at -40 °C practically did not differ from that at higher temperatures.
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SMV-2021-42: Thermal properties of MLI spacers
Králík, Tomáš
Super insulations are special types of thermal insulations used in industrial applications of low temperatures and the apparatuses for the exploration of Space. They are composed of many layers of reflective foils interleaved by thin fabric- the spacer. The goal of the project was the experimental evaluation of the heat transfer across the sample of the spacer used in the super insulation. The evaluation was done under defined compression of the sample in vacuum and temperatures in the range from 10 K to 300 K. The thickness of the sample was simultaneously measured together with the thermal properties of the sample by using electrical capacity. All measurements were done in a unique apparatus Spaceman at conditions simulating the real environment where the materials are used.
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Conceptual design of a gear tester for space applications
Florián, Vojtěch ; Černohlávek, Mikuláš (referee) ; Košťál, David (advisor)
This bachelor thesis deals with the creation of a conceptual design of gears tester for space applications. The tester must simulate space conditions and test whether the gear can operate in those conditions. It is more important to test the wheel material than its geometry. The work is divided into theoretical and practical part. In the theoretical part, a search of current knowledge of the issue is created. The second part describes several conceptual designs of testers and their models. Subsequently, a concept that can most faithfully simulate real conditions in low orbit is selected and described in detail. The final design of this concept will facilitate the testing of gears and minimize their failure rate during operation.
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Comparison of different types of commercial lithium-ion batteries and their properties under low temperature
Bičák, Tomáš ; Máca, Josef (referee) ; Libich, Jiří (advisor)
The diploma thesis deals with the issue of lithium-ion batteries. Describes development, technologies and materials used. The diploma thesis describes the operating principle, characteristics, advantages and disadvantages. The work is focused on the characteristic properties of commercial lithium-ion batteries under standard conditions and at reduced temperatures. At reduced temperatures, changes in properties due to low temperatures are observed. Furthermore, in this work they compare the measured values with the values given by the manufacturers.
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Analysis of critical parameters of the batteries for space applications
Šimek, Michal ; Šedina, Martin (referee) ; Kazda, Tomáš (advisor)
This thesis deals with the use of lithium-ion batteries for space applications. Primary and secondary electrochemical sources and their comparison are described in the paper. The main part of this work deals with lithium-ion batteries, their history, properties and used materials, deals with the use of li-ion batteries for space applications in terms of temperature and describes the effects of temperatures on li-ion batteries. At the last chapter deals with a lithium plating and his detection. In the practical part, a methodology for the detection of cast plating is proposed, which I then test on a number of cells, which I measure at various practical workloads.
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SMV-2018-23: Experimental estimation of the influence of the contamination on thermal radiative properties of adhesive tapes for cryogenic applications
Králík, Tomáš
The goal of this research cooperation, was to estimate an influence of possible contamination of the outer side of aluminium adhesive tapes on its thermal radiative properties in the temperature range from 10 K to 300 K. The aluminium adhesive tapes are commonly used for joining of multilayer insulations, for covering of spots with high emission or absorption of thermal radiation or holes in radiation shields. They are also used for fixation of electric wires. As low as possible emission or absorption of thermal radiation of the tapes is one of the important requirements. This fulfils only clean metallic surfaces. There are two types of adhesive tapes used in the industry. The first type has a special treatment of the outer side so the adhesive do not visibly stick on the outer side after unwinding of the tape. The second type has a lining made of silicon paper, which covers the adhesive side of the tape and protect the outer side. The lining is removed just before the application of the tape.\nThe tapes and an aluminium foil laminated on a PET foil were applied on copper plates suitable for special apparatus Emister developed at ISI Brno. The absorption of thermal radiation by the sample was measured in this apparatus. The source of the thermal radiation was a black reference sample with temperature in the range from 10 K to 300 K. The temperature of the sample of the tape in the range from 5 K to 33 K. The vacuum in the cryogenic part of the apparatus is kept by cryopumping so the parasitic heat transfer by the residual gas is negligible. \nThe conditions in the apparatus are very similar to those in common cryogenic devices and they enable to gain thermal absorptivity of the tapes and very precise comparison of the samples.\n
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Design of a Non-Resonant General Purpose Sample Holder for Terahertz Electron Paramagnetic Resonance Spectroscopy
Martínek, Tomáš ; Sojka, Zbigniew (referee) ; Neugebauer, Petr (advisor)
Cílem diplomové práce je navrhnout konstrukční řešení držáků vzorků pro vysokofrekvenční elektron paramagnetickou resonanci. Předmětem návrhu je vytvořit jednoduchý zamykací systém pro spojování mikrovlnného vlnovodu a držáku vzorku. Dále navrhnout systém s řešením držáku pro více vzorků. Toto unikátní provedení držáku povede k několikanásobné úspoře celkového času měření vzorků. Poslední návrh spočívá v optimalizaci držáku vzorku s možností naklápění osy, kterou lze díky přímému napojení na piezoelektrický rotátor pootáčet s přesností na miliradiány. Oba typy držáku vzorku jsou navrženy s ohledem na automatizaci měření.
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SMV-2017-26: Upgrade of the apparatus Spaceman – capacitive system for the measurement of the sample thickness
Králík, Tomáš
The goal of this research cooperation, which is follow- up of the previous cooperation, was an upgrade of the apparatus Spaceman. The upgrade enables to obtain new data of the spacers used in the multilayer insulations. The spacer can be woven or non-woven textile made of glass, plastic or natural fibres. The apparatus Spaceman measures heat flow through a sample of the spacer in the range from 10 K to 290 K in vacuum. The temperature drop on the sample is typically 5 K. The apparatus was enhanced by a system for measurement of the in-situ sample thickness from evaluation of the electrical capacity between electrically conductive contact surfaces. The upgrade was done by particular disassembling of the apparatus, modification or exchange of some parts, welding of a new vacuum feed trough in the apparatus lid, development and installation of a new electronic in the vacuum space. The electronic is placed in the upper part of the apparatus at room temperature and the electrical capacitance is measured by a special cryogenic coaxial cable. The electronic is able to cancel a parasitic capacitance of the cable. Some modifications were done on the Labview control software developed for the apparatus. The apparatus now enables to measure not only the thermal conductivity at various temperatures and loads but also changes of the sample thickness due to thermal dilatations and loads. It is also possible to evaluate an elastic behaviour of the sample at temperatures from 10 K to 290 K.
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Effect of thermal radiation on low temperature measurement for various types of temperature sensor installations
Urban, Pavel ; Hanzelka, Pavel ; Králík, Tomáš ; Vlček, Ivan ; Srnka, Aleš
We investigated an effect of thermal radiation (300 K) on precision of low temperature measurement of a sample holder (or sample) in an UHV SEM/SPM microscope working at range down to 20 K for various ways of temperature sensor mounting. We designed a special copper casing for installation of Lake Shore\ntemperature sensors (CernoxTM and Si diodes) encapsulated in SD packages. The sensor body is attached direct to the casing using indium solder. The current leads pertaining to the sensor are thermally anchored but electrically insulated from the casing. Quality of sensors installation in the casing was tested for various ways of mounting on a cooled plate. Insufficient thermal anchoring of electrical wires and thermal shielding were imitated. Comparative measurement was also performed with sensors in SD package mounted without\ncasing. The experiments proved that our special design of temperature sensors casing is adequate for intended application of temperature measurement of sample holder in UHV SEM/SPM microscope. In contrary, measurement precision of unprotected sensors was absolutely unsuitable.
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Studium magnetismu ve sloučeninách CeTX3
Moudřík, Jan ; Prokleška, Jan (advisor) ; Javorský, Pavel (referee)
Solid solutions of BaNiSn3 type CeTX3 (T and X denote a transition met- al and Si/Ge, respectively) compounds were studied. Polycrystalline samples of solid solutions CeCoxRh1−xSi3 (x = 0.5, x = 0.8, x = 0.9 and x = 1.0) and CeIr(SixGe1−x)3 (x = 0.1, x = 0.4, x = 0.6 and x = 0.8) were successfully grown. A superconducting transition at 0.7-0.9 K was exhibited by all four compositions of the solution CeCoxRh1−xSi3. Based on measurements of specific heat, we con- clude that the superconductivity is probably caused by impurity phases. We have determined crystallographic, thermodynamic and magnetic properties of the solu- tion CeIr(SixGe1−x)3. Magnetic phase transition temperatures were established, the character of the transitions changed significantly in all four compositions, the temperatures themselves did not. 1
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