Effect of gold coating on emissivity and absorptivity of Ti-6Al-4V alloy

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

SMV-2022-10: CRYSA project – CRYostat Straps for the Athena space telescope

The goal of the project, from the point of view of the Cryogenics and Superconductivity group at the Institute of Scientific Instruments of the Czech Academy of Sciences (ISI Brno), resides in a cooperation with OHB Czechspace and the Institute of Physics of Materials of the CAS (IPM) in order to select and experimentally measure the properties of materials suitable for mounting a device at a very low temperature (cryostat straps), which will be part of the upcoming Athena space telescope of the European Space Agency (ESA). The project consortium will conduct a survey of available materials and, based on this review, will select two most suitable and commercially available materials, which will be later tested in individual CAS institutes. Materials must meet two basic properties – high mechanical stiffness and low thermal conductivity. Members of the Cryogenics and Superconductivity group at ISI Brno will perform, with the help of special equipment and cooling using liquid helium bath, thermal conductivity measurements and the exposure of selected materials to low temperatures for next mechanical tests at the IPM. The outputs of this project will help ESA with the selection of the optimal material for the construction of the straps supporting the given Athena cryostat

SMV-2021-23: Low-temperature emission of electromagnetic radiation by a special coating intended for a space probe

This contractual research was focused on emission of thermal radiation by a special coating, which will be applied on part of the surface of JUICE space probe to ensure optimal heat management of the instrument. In cooperation with the ordering party, two samples, deposited by a special coating with different thickness, were designed and fabricated. Goal of the project was to evaluate the total hemispherical emissivity in wide temperature range from 20 to 300 K. The results will help the ordering party to choose optimal thickness of the surface coating to be used for the probe

SMV-2019-08: Heat transfer by thermal radiation in a kapton foil-based multilayer insulation

The aim of the study was emission of thermal radiation emitted by a foil made of material known as black kapton coated with a special layer. Such foils are often part of Multi-Layer Insulations (MLI) used in order to minimise the impact of the external environment on the spacecraft. The thermal radiative properties of both sides of the foil sample were tested under high vacuum using dedicated apparatus cooled by liquid helium. Sample temperatures ranged from 20 K up to 280 K

SMV-2021-25: Degree of thermal radiation emission by special layers for space applications

The subject of the contract research was the analysis of the relative ability of thermal radiation in the entire present electromagnetic spectrum of special surfaces, which will be used by the European Space Agency as heat radiators for the Athena satellite. In cooperation with the ordering party, two pairs of samples have been designed and manufactured, each pair with different highly-emissive coating. An aluminium alloy was used as the base substrate. The so-called total hemispherical emissivity in the temperature range from 20 K to 320 K was measured individually for each sample, using our dedicated cryogenic apparatus. In the frame of this contract, we have also provided our expert opinion and comparison with data from our own database in order to help interpret the obtained results

SMV-2019-07: Emission of thermal radiation of a niobium sample at very low temperatures

The aim of the study was verification of the radiative heat emission from a niobium disc. The sample was prepared and installed in a special cryogenic apparatus. The thermal radiative properties of the sample were tested in the apparatus placed in a liquid helium bath. The sample was kept under high vacuum and at temperatures ranging from 7 K to 280 K. Two different temperature controllers were used and a new system for data collection and processing were developed due to very low signal of the sample at lowest temperatures

SMV-2022-06: Thermal radiation of space probes components

As a part of the upcoming project ARIEL of the European Space Agency, the ordering party Admatis Ltd. needed to determine the temperature dependence of the relative rate of thermal radiation of six different thermoregulatory coatings intended for some external surfaces of the space probe ARIEL. Coatings were tested using a special dedicated method, operating in a liquid helium bath, for temperature interval from approximately -253 °C up to room temperatures. During the cryogenic tests, the character of the total hemispherical radiation of the given layers at all wavelengths was determined. As part of the research, the interpretation and comparison of the measured data was also carried out, based on our experience and using our unique low-temperature database of cryogenic measurements. The results will help the ordering party to select a layer with optimal thermal properties for the given application

SMV-2022-07: Cryogenic tests of aluminium foils with low emission and absorption of thermal radiation

The research was focused on the heat transfer by thermal radiation, specifically the interaction of thermal radiation with several different types of aluminium foils, used mainly in the so-called multilayer insulation (MLI). From the supplied raw material, samples suitable for testing were fabricated at the ISI Brno and then examined according to the requirements of the company. We focused on the temperature dependence of the relative ability of the samples to emit or absorb thermal radiation at all wavelengths and in all directions. The experimental verification then took place in a dedicated apparatus cooled by a liquid helium bath for a temperature range from about -253 °C to room temperature, which required choosing an optimal configuration of the apparatus and verifying its calibration. After the individual measurements, the received data were processed, the temperature stability of the foils at low temperatures was evaluated and their thermal-radiation properties were compared with our own low-temperature database of cryogenic measurements. The project contributed to selection of the optimal foil for the intended application, i. e. for use in MLI

SMV-2021-24: Emissivities of multilayer reflective foils and highly absorptive coatings with different morphology

This contractual research dealt with materials of very different ability to emit thermal radiation. First project was focused on aluminium-based multilayer foils designed for high reflection of incident light. In the second project we have studied special highly emissive coatings prepared by two different companies. The goal was to determine total hemispherical emissivity of each sample at required temperatures. In the case of the highly emissive coatings the ordering party´s goal was also to evaluate the influence of morphology on the final emission of thermal radiation. Namely, we have tested flat, pyramidal and grooved surfaces with each of the mentioned coatings. This unique research required special shape of samples, modification of the dedicated method for measurement emissivities and absorptivities at cryogenic temperatures and also new calibration procedure and data evaluation. For the first time we used a shielding collar, newly designed and developed in our lab, to cover the circumference of the sample discs and prevent leak of part of the measured thermal radiation. This research extended our knowledge in the field of impact of surface morphology on thermal radiation emission

SMV-2020-25: Emission of electromagnetic radiation by thin gold layers at cryogenic temperatures

The aim of the contract research was analysis of the ability of gold layers deposited on aluminium substrate to emit electromagnetic waves (thermal radiation) at cryogenic temperatures. Four different samples were designed and fabricated in cooperation with the ordering party. Very low signal of the samples required using of our dedicated instrument together with development of an individual calibration processes for each experiment. The instrument measured emission of thermal radiation at all wavelengths and between temperatures 20 and 320 K, reached using a liquid helium bath. The vacuum was kept by cryopumping so the parasitic heat transfer by the residual gas was negligible. One of the samples reached emissivity values typical for an alloyed gold layer. However, values reached by other three samples were significantly lower, even below the level of our sputtered high purity gold coating. The results allow the ordering party to choose optimal type of surface deposition for their intended application