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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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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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Role of the superconductivity in radiative heat transfer
Králík, Tomáš ; Musilová, Věra ; Srnka, Aleš ; Fořt, Tomáš ; Frolec, Jiří
The absorption and emission of thermal radiation by metals is related to their electrical properties that are influenced by impurities, defects and temperature. We show by some examples of measurements on common metals how different can be the thermal radiative properties. When the heat is transferred across a microscopic vacuum gap in the near field regime, it is possible to achieve a step-like change of the heat\ntransfer based on a superconducting transition. An interesting feature of this effect is the nonlinear thermal conductivity effecting a change of the sign of the differential thermal conductivity across the vacuum gap.
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Effect of gold coating on emissivity and absorptivity of Ti-6Al-4V alloy
Frolec, Jiří ; Králík, Tomáš ; Musilová, Věra ; Urban, Pavel
The article provides experimental analysis of total hemispherical emissivity and absorptivity of Ti-6Al-4V alloy before and after deposition of 1-2 .pí.m gold layer. We measured their dependences on the temperature of thermal radiation (varying from 20 K to 320 K) and confronted these results with mechanically polished copper, i.e. with material known for extremely low emissivity and absorptivity. Galvanic deposition of pure gold resulted in significant lowering of original emissivity of Ti-6Al-4V bare surfaces from 15.8 percent to 3.4 percent at 300 K and from 4.1 percent to 1.1 percent at 20 K. Our findings about thermal-radiative properties have practical relevance for an improvement of a low temperature part of an ultra-high vacuum scanning probe microscope\n(UHV-SPM) designed by our group and could also be useful for other applications and low temperature systems.
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SMV-2016-16: Emission and absorption of the thermal radiation of metallic materials for space crafts
Králík, Tomáš
The goal of the experimental study was verification of the radiative heat exchange by emission or absorption of the thermal radiation of materials for parts of a future meteorological satellite. The samples were coated by a protective metallic layer by a magnetron sputtering. It is supposed that this coating substantially decreases the emission of a thermal radiation in comparison with the bare alloy. Within the study were verified also the thermal radiative properties of samples made of bare sandblasted alloy, samples with the protective coating and samples treated by anodic oxidation. The thermal radiative properties were measured in high vacuum with sample temperatures in the range from 25 K to 320 K.
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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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Enhanced HTML Editor
Králík, Tomáš ; Bařina, David (referee) ; Řezníček, Ivo (advisor)
Subject of this bachelor's thesis was design of extended HTML editor. Reader is familiarized with HTML and JavaScript languages at first. Following is overview of existing WYSIWYG HTML editors and their comparison. The design of extended HTML editor requires a specification of disadvantages of existing editors. From these, the requirments for extended HTML editor were formed. The editor was designed and implemented using JavaScript and Dojo library. Two web applications were created for testing: blog and encyclopedia. The blog application was used for an user interface testing. Users tried out designed editor and editor TinyMCE during the testing. The results of the testing are summarized in conclusion together with proposal of a future work.
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