Atomic oxygen effects on boron nitride and silicon nitride: A comparison of ground based and space flight data
The effects of atomic oxygen on boron nitride (BN) and silicon nitride (Si3N4) were evaluated in a low Earth orbit (LEO) flight experiment and in a ground based simulation facility. In both the inflight and ground based experiments, these materials were coated on thin (approx. 250A) silver films, and the electrical resistance of the silver was measured in situ to detect any penetration of atomic oxygen through the BN and Si3N4 materials. In the presence of atomic oxygen, silver oxidizes to form silver oxide, which has a much higher electrical resistance than pure silver. Permeation of atomic oxygen through BN, as indicated by an increase in the electrical resistance of the silver underneath, was observed in both the inflight and ground based experiments. In contrast, no permeation of atomic oxygen through Si3N4 was observed in either the inflight or ground based experiments. The ground based results show good qualitative correlation with the LEO flight results, indicating that ground based facilities such as the one at Los Alamos National Lab can reproduce space flight data from LEO.
Oxidation‐resistant reflective surfaces for solar dynamic power generation in near earth orbit
Reflective surfaces for Space Station power generation systems are required to withstand the atomic oxygen‐dominated environment of near earth orbit. Thin films of platinum and rhodium, which are corrosion‐resistant reflective metals, have been deposited by ion beam sputter deposition onto various substrate materials. Solar reflectances were then measured as a function of time of exposure to a rf‐generated air plasma. Similarly, various protective coating materials, including MgF2, SiO2, Al2O3, and Si3N4, were deposited onto silver‐coated substrates and then exposed to the plasma. Analysis of the films both before and after exposure by both electron spectroscopy for chemical analyses (ESCA) and Auger spectroscopy was also performed. The results indicate that Pt and Rh do not suffer any loss in reflectance over the duration of the tests. Also, each of the coating materials survived the plasma environment. The ESCA and Auger analyses are discussed as well.
The Role of Human Rights in EU-US Bilateral Relations
This report aims to analyse the different dimensions and levels of EU-US relations, to survey the instruments the EU uses in this relation and to provide some recommendations for future EU actions. It provides an overview of the main similarities and differences between the EU and the US regarding human rights, and measures the influence of the EU on the state and practice of human rights in the United States. Likewise, this report analyses how the United States may affect human rights in the EU and its Member States, notably in light of US policies that are strongly criticized by the EU from a human rights-based perspective.