Nanostruktuursed pinnakatted auto-, lennu- ja kosmosetööstusele

Väitekirja elektrooniline versioon ei sisalalda publikatsiooneAlumiiniumsulamid on kerged ning suurepäraste mehaaniliste omadustega, mille tõttu kasutatakse neid laialdaselt komponentide valmistamiseks lennu- ja autotööstuses. Paraku on parimad alumiiniumsulamid tundlikud korrosiooni suhtes, mida saab takistada erinevate kaitsekatete abil. Põhiliseks väljakutseks on seejuures kaitse tagamine täppisdetailidele, mille mõõtmed ei tohi palju muutuda ja mis võivad olla keeruka kolmemõõtmelise kujuga ning sisaldada ka keermetega auke. Selle probleemiga tegeleti antud uurimustöös, kus uuriti nanokatete rakendamist alumiiniumsulamite korrosioonikindluse tõstmiseks. Erinevate keraamiliste kaitsekatete valmistamiseks kasutati uurimustöös aatomkihtsadestuse meetodit, millega kaeti erineva eeltöötlusega alumiiniumdetailide. Süstemaatiliste uuringute vältel töötati välja uudne meetod et valmistada nanostruktuurseid kaitsekatteid, mis tagasid alumiiniumdetailidele suurepärase kaitse korrosiooni eest. Samuti testiti kaitsekatet energeetilise atomaarse hapnikuga, millega simuleeriti 1 aasta pikkust kokkupuudet kosmose tingimustega madalal orbiidil. Uudne nanostruktuurne kate on praeguseks kantud üle 50-le alumiiniumdetailile satelliidil WISA Woodsat, kus tema eesmärk on tagada funktsionaalsus kriitilistele liikuvatele detailidele. Samuti uuritakse peagi uudse katte käitumist kosmoses materjalide testimise mooduli abil, mis on integreeritud satelliidile ESTCube-2.Aluminum alloys are widely used for manufacturing components in aerospace and automobile industries. Aluminum alloys are favored in these applications as they have light weight and superior mechanical properties but are also easy to process. However, these alloys are vulnerable to corrosion, which can be mitigated by using various protective coatings. The primary challenge with aluminum alloys in practical applications is the protection of high precision substrates that may also have a sophisticated three-dimensional shape or contain threaded cavities. This problem was addressed in this study, where the use of nanometric protective coatings was investigated. For that purpose, atomic layer deposition technique was used to grow various ceramic materials onto the aluminum alloy substrates that had received different pre-treatments. During these systematic studies, a technique was developed for the preparation of a novel nanostructured coating which protected the aluminum alloy against corrosion in salt spray tests. The novel coating also suffered only negligible damage from energetic atomic oxygen, which was used to simulate 1 year of exposure to space in low Earth orbit. Finally, the novel nanostructured coating was successfully applied on over 50 aluminum parts of satellite WISA Woodsat and will also be tested soon in space on the materials testing module on ESTCube-2.https://www.ester.ee/record=b552641

Nanostructured Coating for Aluminum Alloys Used in Aerospace Applications

The authors would like to acknowledge the Estonian Ministry of Education and Research by granting the projects IUT2–24, TLTFY14054T, PSG448, PRG4, SLTFY16134T and by the EU through the European Regional Development Fund under project TK141 (2014-2020.4.01.15-00). The atomic oxygen testing was performed in the framework of the “Announcement of opportunity for atomic oxygen in the ESTEC Materials and Electrical Components Laboratory/ESA-TECQE-AO-013375),” through a collaboration with Picosun Oy. The authors also thank Dr. Elo Kibena-Põldsepp for the electrodeposition of Ag onto the anodized substrates.A thin industrial corrosion-protection nanostructured coating for the Al alloy AA2024-T3 is demonstrated. The coating is prepared in a two-step process utilizing hard anodizing as a pre-treatment, followed by sealing and coating by atomic layer deposition (ALD). In the first step, anodizing in sulfuric acid at a low temperature converts the alloy surface into a low-porosity anodic oxide. In the second step, the pores are sealed and coated by low-temperature ALD using different metal oxides. The resulting nanostructured ceramic coatings are thoroughly characterized by cross-sectioning using a focused ion beam, followed by scanning electron microscopy, transmission electron microscopy, X-ray microanalysis, and nanoindentation and are tested via linear sweep voltammetry, electrochemical impedance spectroscopy, salt spray, and energetic atomic oxygen flow. The best thin corrosion protection coating, made by anodizing at 20 V, 1 °C and sealing and coating with amorphous Al2O3/TiO2 nanolaminate, exhibits no signs of corrosion after a 1000 h ISO 9227 salt spray test and demonstrates a maximum surface hardness of 5.5 GPa. The same coating also suffers negligible damage in an atomic oxygen test, which is comparable to 1 year of exposure to space in low Earth orbit. © 2022 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.Estonian Ministry of Education and Research by granting the projects IUT2–24, TLTFY14054T, PSG448, PRG4, SLTFY16134T; ERDF TK141 (2014-2020.4.01.15-00); Institute of Solid State Physics, University of Latvia as the Center of Excellence acknowledges funding from the European Union’s Horizon 2020 Framework Programme H2020- WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

Coulomb drag propulsion experiments of ESTCube-2 and FORESAIL-1

This paper presents two technology experiments – the plasma brake for deorbiting and the electric solar wind sail for interplanetary propulsion – on board the ESTCube-2 and FORESAIL-1 satellites. Since both technologies employ the Coulomb interaction between a charged tether and a plasma flow, they are commonly referred to as Coulomb drag propulsion. The plasma brake operates in the ionosphere, where a negatively charged tether deorbits a satellite. The electric sail operates in the solar wind, where a positively charged tether propels a spacecraft, while an electron emitter removes trapped electrons. Both satellites will be launched in low Earth orbit carrying nearly identical Coulomb drag propulsion experiments, with the main difference being that ESTCube-2 has an electron emitter and it can operate in the positive mode. While solar-wind sailing is not possible in low Earth orbit, ESTCube-2 will space-qualify the components necessary for future electric sail experiments in its authentic environment. The plasma brake can be used on a range of satellite mass classes and orbits. On nanosatellites, the plasma brake is an enabler of deorbiting – a 300-m-long tether fits within half a cubesat unit, and, when charged with -1 kV, can deorbit a 4.5-kg satellite from between a 700- and 500-km altitude in approximately 9–13 months. This paper provides the design and detailed analysis of low-Earth-orbit experiments, as well as the overall mission design of ESTCube-2 and FORESAIL-1.Peer reviewe

Coulomb drag propulsion experiments of ESTCube-2 and FORESAIL-1

This paper presents two technology experiments – the plasma brake for deorbiting and the electric solar wind sail for interplanetary propulsion – on board the ESTCube-2 and FORESAIL-1 satellites. Since both technologies employ the Coulomb interaction between a charged tether and a plasma flow, they are commonly referred to as Coulomb drag propulsion. The plasma brake operates in the ionosphere, where a negatively charged tether deorbits a satellite. The electric sail operates in the solar wind, where a positively charged tether propels a spacecraft, while an electron emitter removes trapped electrons. Both satellites will be launched in low Earth orbit carrying nearly identical Coulomb drag propulsion experiments, with the main difference being that ESTCube-2 has an electron emitter and it can operate in the positive mode. While solar-wind sailing is not possible in low Earth orbit, ESTCube-2 will space-qualify the components necessary for future electric sail experiments in its authentic environment. The plasma brake can be used on a range of satellite mass classes and orbits. On nanosatellites, the plasma brake is an enabler of deorbiting – a 300-m-long tether fits within half a cubesat unit, and, when charged with - 1 kV, can deorbit a 4.5-kg satellite from between a 700- and 500-km altitude in approximately 9–13 months. This paper provides the design and detailed analysis of low-Earth-orbit experiments, as well as the overall mission design of ESTCube-2 and FORESAIL-1.</p

Metallic impurity free carbon nanotube paste electrodes

Electrodes modified with carbon nanomaterials find wide ranging applications in electrochemistry such as in energy generation and storage through to applications in electroanalysis. A substantial limitation is the presence of metallic impurities which vary between batches and can produce erroneous results. Consequently we have explored the electrochemical properties of metallic impurity free carbon nanotube paste electrodes using potassium ferrocyanide and hydrogen peroxide as model compounds. In terms of the latter utilising cyclic voltammetry, a linear range from 0.75 to 3 mM with a limit of detection of 0.19 mM is possible using the electrochemical oxidation of hydrogen peroxide while using the electrochemical reduction of the target analyte, a linear range from 0.5 to 249 mM is possible with a detection limit of 0.43 mM. The ultra-small size of the carbon nanotubes and fabrication methodology result in a tightly bound carbon nanotube electrode surface which does not exhibit thin-layer behaviour resulting in highly reproducible electrodes with the %RSD found to be 5.5%. These analytical ranges, detection limits and reproducibility are technologically useful. The carbon nanotubes utilised are completely free from metallic impurities and do not require lengthy processing to remove impurities and consequently have no variation in the purity of the nanomaterial between batches as is commonly the case for other available carbon nanotube material. The impurity free nature of this nanomaterial allows for highly reproducible and intelligent sensors based on carbon nanotubes to be understood and realised for the first time

Prussian Blue Modified Solid Carbon Nanorod Whisker Paste Composite Electrodes: Evaluation towards the Electroanalytical Sensing of H2O2

Metallic impurity free solid carbon nanorod “Whiskers” (SCNR Whiskers), a derivative of carbon nanotubes, are explored in the fabrication of a Prussian Blue composite electrode and critically evaluated towards the mediated electroanalytical sensing of H2O2. The sensitivity and detection limits for H2O2 on the paste electrodes containing 20% (w/w) Prussian Blue, mineral oil, and carbon nanorod whiskers were explored and found to be 120 mA/(M cm2) and 4.1 μM, respectively, over the concentration range 0.01 to 0.10 mM. Charge transfer constant for the 20% Prussian Blue containing SCNR Whiskers paste electrode was calculated, for the reduction of Prussian Blue to Prussian White, to reveal a value of 1.8±0.2 1/s (α=0.43, N=3). Surprisingly, our studies indicate that these metallic impurity-free SCNR Whiskers, in this configuration, behave electrochemically similar to that of an electrode constructed from graphite

Data of oxygen reduction reaction on Pd nanocatalysts prepared by plasma-assisted synthesis on different carbon nanomaterials

This dataset contains the data presented in the figures of published paper "Oxygen reduction reaction on Pd nanocatalysts prepared by plasma-assisted synthesis on different carbon nanomaterials" Nanotechnology 32 035401 (https://doi.org/10.1088/1361-6528/abbd6f

An Oxygen Reduction Study of Graphene-Based Nanomaterials of Different Origin

The aim of this study is to compare the electrochemical behaviour of graphene-based materials of different origin, e.g., commercially available graphene nanosheets from two producers and reduced graphene oxide (rGO) towards the oxygen reduction reaction (ORR) using linear sweep voltammetry, rotating disc electrode and rotating ring-disc electrode methods. We also investigate the effect of catalyst ink preparation using two different solvents (2-propanol containing OH− ionomer or N,N-dimethylformamide) on the ORR. The graphene-based materials are characterised by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Clearly, the catalytic effect depends on the origin of graphene material and, interestingly, the electrocatalytic activity of the catalyst material for ORR is lower when using the OH− ionomer in electrode modification. The graphene electrodes fabricated with commercial graphene show better ORR performance than rGO in alkaline solution

Effect of Ball-Milling on the Oxygen Reduction Reaction Activity of Iron and Nitrogen Co-doped Carbide-Derived Carbon Catalysts in Acid Media

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