National Repository of Grey Literature 42 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
SMV-2022-43: Absorptivity and emissivity of materials for use in space
Králík, Tomáš
This contractual research was aimed at verifying the thermal radiation properties of the emissivity of coatings and covering foils for space probes. Half of the experiments were focused on thermal regulation coatings, the purpose of which is to passively maintain the optimal temperature of the device, the balance between thermal radiation and absorption of visible radiation. Some foils had unique thermochromic properties, where their thermal radiative properties change sharply with their own temperature. The second part of the research was focused on the effect of contamination of a clean metal surface with dust simulating lunar regolith on the absorption of thermal radiation. As part of this research, five differently contaminated surfaces were measured. This unique data will enable the contractor to better design apparatus for work on the surface of the Moon or other planets. The contractor selected and supplied\nsamples of materials in the form of foils and coated sheets, which had to be modified into a sample suitable for the apparatus operated at the ISI Brno. A material labelled EAC‐1A was used as a lunar regolith simulant. The goal of the project was to evaluate the so‐called total hemispheric emissivity or absorptivity in the temperature range from 20 K to 300 K.
SMV-2022-42: Emissivity of coatings for space mission ARIEL
Králík, Tomáš
This contractual research was aimed at verifying the thermal emissivity of materials planned for use in the optical system of the ARIEL infrared telescope located in orbit around the earth. The contractor selected several samples of the coating with high light absorption. However, the thermal radiation properties of this coating were not yet known. The goal of the project was to evaluate the so-called total hemispheric emissivity in the temperature range from 20 K to 300 K. The results will enable the customer to model the temperature distribution inside the optical path of the telescope.
Low-temperature emissivity of thin Al2O3 layers deposited on copper substrate
Frolec, Jiří ; Králík, Tomáš ; Nyman, L. ; Pudas, M. ; Kallio, E.
Copper is commonly used in cryogenic systems due to its high thermal and electrical conductivity along with excellent solderability. Very low emissivity values of copper surface also reduce in cryogenic systems heat load transferred by thermal radiation. These values may be, however, enhanced by a prospective coating, deposited usually in order to prevent chemical changes on highly reactive copper surface. This paper focuses on protective layers of Al2O3 with thicknesses up to 28 nm, deposited on polished copper. We measured total hemispherical emissivity at cryogenic temperatures before and after the coating process. Contribution of Al2O3 layer to original copper emissivity increased with rising temperature of the layer and with the layer thickness. However, emissivity of the coated copper stayed below 2%, allowing usage of the coated copper in systems where low heat load by thermal radiation is needed. Preliminary tests with oxygen plasma shows that deposited layers can effectively protect the copper surface against oxidation and maintain the original thermal-radiative properties.
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.
SMV-2021-40: Thermal emission of CFRP material in vaccum
Králík, Tomáš
This contractual research was focused on the evaluation of the thermal emissivity of material for the structural beam of the space telescope ARIEL. The material is a carbon fibre composite. The knowledge of the thermal emissivity of this material is important for modelling the temperature of the telescope. Its temperature should be passively kept at 55 K only by thermal radiation. The goal of the project was to evaluate the total hemispherical emissivity of the composite in the temperature range from 20 to 300 K. The data was used to decide if the structural beams should be coated with an additional highly emissive layer or not.
SMV-2021-41: Emissivity of the materials for space missions
Králík, Tomáš
This contractual research was focused on evaluation of the thermal emissivity of materials used for space probes to ensure optimal passive thermal control of the device. The ordering party has chosen several types of materials in a form of foils or coated sheets. The materials were shaped to fit in the measurement apparatus. Goal of the project was to evaluate the total hemispherical emissivity in temperature range from 20 to 300 K. The results will help the ordering party to model the temperature distribution cooled in space only by the thermal radiation.
SMV-2020-53: Thermal radiation of gold plated surfaces for low temperature applications
Králík, Tomáš
The goal of this experimental study was evaluation of the thermal radiation rate by a surface of an alloy coated with a thin layer of gold. The alloy without gold coating would have of about five time higher rate of the emission or absorption of the thermal radiation. Higher thermal emission makes the thermal control of the parts of space or cryogenics apparatuses more difficult. The contractor has coated three samples of the alloy with gold by various processes. Two other coated samples were cleaned by an industrial cleaning process.\nThe emission of the thermal radiation from the surface of the samples was experimentally evaluated in the range of the sample temperatures from 20 K to 320 K compared to the black body at the same temperature. The results of the study enable to routinely produce parts for satellites or cryogenics with guaranteed thermal emissivity.\n
Zhodnocení stavu Knínického potoka z hlediska znečištění fosforečnany
Králík, Tomáš
This bachelor thesis Condition assessment of the stream Knínický potok in terms of phosphate pollution occupies with monitoring of water pollution in the stream Knínický potok which was carried out from April 2015 to march 2017. The monitored factors were total phosphorus, phosphates, pH, conductivity, dissolved oxygen and tempera-ture. The theoretical part outlines the problematics of different water types, water pollution especially phosphorus pollution and the related legislation. The practical part describes the profiles selected for water sampling, methodology of both fieldwork and laboratory work and also the characteristics of the area. The essential part are the measurement results with commentary, evaluated and compared to the provision of government 401/2015 Sb, in an effective version and to the ČSN 75 7221. According to the results, the main source of pollution is water drained from the wastewater treatment plant. Parameter with the worst measured results was total nitrogen, which has reached extremely high above the NEK limit.
SMV-2019-10: Characterisation of Cu alloys at low temperatures
Králík, Tomáš
The goal of the project was to measure the electrical conductivity of eight samples made of pure or alloyed copper at the temperatures 4.2 K, 77 K and 300 K for the as received, annealed and hardened state. The electrical conductivity is correlated with the thermal conductivity and the ratio between electrical conductivity at 300 K and 4.2 K (RRR value) gives the purity of the metal including mechanical defects in the material. Pure copper is excellent conductor of heat and electric current but it does not have required strength properties compared to the alloyed coppers. The measured temperature dependence of the electrical conductivity enables to compare the copper materials and to choose one with optimal properties for the current leads of the fusion reactor. \nThe samples with a cross section 0.15-0.3 mm^2 and length 33-70 mm were cut by slow milling. One of the samples of each material was annealed at 980°C for 1.5 hour and the second was hardened at 480°C for 5 hours. All samples (24 pcs) were soldered with Indium solder on a special holder with contacts for the four wire electric resistance measurement. The electrical resistance was measured by a AC resistance bridge Lake Shore 372.\n

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33 Králík, Tomáš
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