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Eingeladener Vortrag
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Outstanding features favour the application of polymers and polymer composites in low-temperature technology. The booming hydrogen technology is a challenge for these materials, which are considered as seals and bearings in cryogenic pumps. In the present study, three types of thermoplastics, i.e., polyetheretherketone (PEEK), polyetherimide (PEI) and polyamide 6,6 (PA6,6), and one epoxy were considered as matrix materials. Micron-sized fillers, i.e., short carbon fibres, graphite flakes, and PTFE powders, were incorporated into these polymers together with nano-sized TiO2 particles. Optimised compositions of each matrix were selected from our previous works at room temperature in order to be studied at very low temperature conditions. In particular, frictional tests were carried out with polymer composite pins against polished steel surfaces under constant load over a certain distance in liquid hydrogen and liquid nitrogen. Afterwards, worn surfaces were analysed by using scanning electron microscopy (SEM). It was found out that the tribological properties in liquid hydrogen are dominated by the matrix materials, in particular thermoplastics perform generally slightly better than thermosetting resins.
Mittels lasergesteuerter gepulster Vakuumbogentechnologie (Laser-Arc) wurde eine reihe von reinen MoS2-Schichten sowie Kombinationsschichten aus MoS2 und tetraedrischem amorphen Kohlenstoff (ta-C) hergestellt. Mit diesen Schichtvarianten erfolgten tribologische Tests im Vakuum sowie in Atmosphäre. Dabei wurden im Hochvakuum reibungskoeffizienten bis zu 0,005 gemessen. Durch die Verwendung einer ta-C unterschicht konnte eine Lebensdauer von über 5×105 Lastzyklen erreicht werden. Zudem erwies sich diese unterschicht als vorteilhaft für das tribologische Verhalten der MoS2/ta-C Schichten unter atmosphärischen Bedingungen. -------------------------------------------------------------------------------------------------------------------------------------------
A series of MoS2 and combined MoS2/ta-C coatings were prepared by lasercontrolled arc evaporation (Laser-Arc) in order to study the tribological coating behaviour under vacuum and atmospheric conditions. Very low friction coefficients down to 0.005 were measured under high vacuum. By using a ta-C underlayer beneath the MoS2 a increased lifetime up to 5×105 load cycles could be obtained. Also under atmospheric conditions the underlayer had a beneficial effect on coating performance.
Tribologisches Verhalten der Werkstoffpaarung Polymerverbundwerkstoff/Stahl bei tiefen Temperaturen
(2005)
The tribological behavior of neat and filled PEEK and PEKK composites were compared in air and vacuum conditions. Very low friction and wear coefficient were obtained at low sliding speed while severe wear occurred at high speed. Experimental results are discussed by analysing the transfer film and wear debris.
The tribological characteristics of pure and graphite filled polymers were investigated in gaseous hydrogen at ambient temperatures and in LH2 at -253°C. It could be shown that the tribological properties of PI and PEEK materials is related to the formation of a transfer film. The influence of both hydrogen and cryogenic temperatures will be discussed in the presentation.
The development of hydrogen technologies is a key strategy to reduce greenhouse gas emission worldwide. Power-to-Gas is a challenging solution, in which hydrogen and methane can be used in mobility, industry, heat supply and electricity generation applications. This presentation deals with the tribological behaviour of polymer materials in hydrogen and methane, both in gas and in liquefied form.
Die Reibeigenschaften von PEEK-Materialien gegen Stahlscheiben wurden in Luft, Vakuum und Wasserstoffumgebung untersucht. Die Ergebnisse zeigen, dass reines PEEK umgebungsabhängig ist und die Desorption von Gasen im Vakuum zu hohen Verschleißraten führt. Die niedrigsten Verschleißraten sowohl in Vakuum als auch in einer Wasserstoffumgebung erzielen TiO2-Partikel. Ferner treten chemische Prozesse in den Materialien und im Tribokontakt auf und interagieren miteinander.