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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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SMV-2016-17: Thermal radiative properties of solar coatings and spacers for multilayer insulations
Králík, Tomáš
The experimental study was about evaluation of thermal radiation of special coatings used against excessive warming by solar radiation. A part of this study was aimed on thermal properties of spacers for multilayer insulations where the heat is transferred by combination of the thermal conduction and radiation. All the measurements were done in the vacuum and in the temperature range from 10 K and 300 K at conditions simulating real environment of the usage of the materials.
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Very low temperature measurement
Mráz, Dominik ; Harabiš, Vratislav (referee) ; Chmelař, Milan (advisor)
This bachelor thesis is focused on low temperature measurement, respectively on temperature sensors classsification, their accuracy, temperature range and linearity. It deals especially in use of these sensors in cryogenic applications. It contains temperature sensor block diagram, including the description of each block. It also contains schematic designs with description of each design’s function, components and the reason why it’s used. Additionally the realization of the temperature sensor is described and it’s testing.
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Very low temperature measurement (to -160 of degrees Celsius)
Vlček, Josef ; Rampl, Ivan (referee) ; Chmelař, Milan (advisor)
his semestral thesis deals with measurement of low temperatures (down to -160 degrees Celsius). This thesis describes basics of cryotherapy and its practical implementation. It also deals with different types of temperature sensors which means theoretical description of their work, thein advantages and disadvantages. The main goal is to put a recommendation of which of this sensors is the most suitable for practical implementation of the thermometer.
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Low temperature tests and fracture toughness of selected ceramic materials
Beck, Branislav ; Drdlík, Daniel (referee) ; Chlup, Zdeněk (advisor)
Diploma thesis deals with the determination of fracture toughness values of sintered silicon carbide and casted basalt using both the Single Edge V-Notch Beam (SEVNB) and the Chevron Notched Beam (CNB) methods at room and cryogenic temperatures. The first part of this thesis offers general overview and categorization of ceramic materials. Fracture mechanics of the ceramic materials and available fracture toughness testing methods are discussed in following chapters. The last section in the theoretical part is aimed to the microstructure and properties of the silicon carbide. Experimental part of the work summarizes methods used for characterization of selected materials from the microstructural and fracture point of view. Preparation of samples for microstructural observation and samples for fracture toughness determination are described in details. The results of the fracture toughness data for sintered silicon carbide and cast-basalt obtained at room temperature and at -100 °C are displayed. Consideration of possible measurements errors and application of various fracture toughness testing methods are discussed in the next chapter of this work. The difference in the fracture toughness values with the decrease of testing temperature was found. The difference depends on both, the used method of fracture toughness determination and the material used for the tests. The most important results gained during the experimental work are summarized in the chapter “Conclusions”.
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SMV-2015-19: Influence of the compression on the thermal conductivity of the MLI spacers
Králík, Tomáš
The experimental study was aimed on characterisation of the thin insulation materials – spacers used in multilayer insulations (MLI). The MLI is composed of reflective foils interleaved by insulating spacers. The samples were made of various materials (glass fibre, polyester, silk). The measurement was done in unique apparatus developed at ISI Brno in the year 2014. The main goal of the study was to evaluate the influence of the compression by a precisely controlled load on the thermal conductivity in the range of temperatures 10 K and 300 K. The not yet available results of the study enable optimisation of the MLI with requested properties.
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SMV-2014-21: Thermal properties of MLI spacers
Králík, Tomáš
The goal of the project is to develop and build an apparatus enabling to measure the heat flow across a sample of the MLI spacer. This is thin woven or nonwoven textile. The requested parameter of the measurement is precisely controlled compression of the sample between contact surfaces with defined temperature in the range of 10 K – 300 K. The compression equals to the load 0.2 g-2 g and it has to be constant despite the thermal dilatations in the apparatus. An electromechanical loading system with load sensor in a feedback control placed in the warm part of the apparatus was developed for this apparatus. The force is mechanically transferred to the cryogenic part of the apparatus.
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Cold tolerance of terrestrial isopod
SOUČKOVÁ, Kateřina
The woodlice, Porcellio scaber (Latreille, 1804), is a terrestrial isopod. Its metabolic reserves and body size are important factors affecting the fitness attributes, such as survival at unfavourable conditions. The larger and heavier individuals did not survive longer than smaller individuals. Amount of glycogen and body weight (fresh and dry) appeared to be an inapplicable parameter in the observed differences among individuals during survival at low temperature. We compared three treatments (long day, short day, natural autumn conditions) of Porcellio scaber and found differences in amount of energy reserves and cryoprotectants.
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