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Proceeding of: Sixth International Conference on Tethers in Space, Madrid, June 12-14, 2019 The Electrodynamic Tether Technology for Passive Consumable-less Deorbit Kit (E.T.PACK) is a project aimed at the development of a deorbit kit based on low-work-function Tether (LWT) technology, i.e., a fully passive and electrically floating system made of a long conductive tape coated with a low-work-function material. The LWT interacts passively with the environment (ambient plasma, magnetic field, and solar radiation) to exchange momentum with the planet's magnetosphere, thus enabling the spacecraft to de-orbit and/or re-boost without the need for consumables. The main goal is to develop a deorbit kit and related software with Technology Readiness Level 4 and promote a follow-up project to carry out an in-orbit experiment. The planned kit in the experiment has three modes of operation: fully passive LWT and conventional electrodynamic tether equipped with an active electron emitter in passive and active modes. Several activities of the project pivot around the C12A7 : e- electride, which will be used in four hardware elements: (i) LWT (ii) hollow cathode, (iii) photo-enhanced thermionic emission device to convert solar photon energy into electrical energy, and (iv) a hollow cathode thruster. These elements, some of which do not belong to the deorbit kit, are synergetic with the main stream of the project and common to some tether applications like in-orbit propulsion and energy generation. This work explains the activities of E.T.PACK and the approach for solving its technological challenges. After reviewing past progresses on electrodynamic tethers and thermionic materials, we present a preliminary concept of the kit for the in-orbit experiment, some simulation results, and the key hardware elements. This work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 828902 (E.T.PACK project). GSA work is supported by the Ministerio de Ciencia, Innovaci on y Universidades of Spain under the Grant RYC-2014-15357. SN work is supported by Comunidad de Madrid (Spain) under the Grant 2018/T2IND/11352

Na-ion solid state batteries operating at room temperature are typically supposed to have a metallic Na anode for sufficiently high energy density. The less known but due to easy processing very promising Na-conducting Na5YSi4O12 glass ceramic is investigated regarding it`s interface resistance in contact with metallic Na electrodes. Two types of this material, with and without P-addition, are investigated. The surface is treated by polishing to induce a defined roughness. Highly polished surfaces lead to incomplete covering with Na metal by application of pressure sufficiently low to avoid the breaking of ceramic. In contrast, surfaces with higher roughness could be covered more homogeneously with Na and thus exhibited significantly reduced interface resistance. These measurements reveal the intrinsically small interface resistance between Na5YSi4O12 glass ceramics and metallic Na, which makes Na5YSi4O12 to promising electrolyte for Na-ion solid state batteries. It is found that prolonged contact of the electrolyte with humid air, like several days or weeks, leads to a strongly increased interface resistance. Thus, storage conditions and surface treatment of the samples after air contact need to be considered carefully.

The corrosion behaviour of Si 3 N 4 ceramics with constant composition (Y 2 O 3 –Al 2 O 3 additives) but of different shapes – plate, cylinder and ball – was investigated in 0.5 mol/l H 2 SO 4 at 90 °C. The corrosion kinetics were measured using weight losses and thickness of the corrosion layers. The investigation showed that the corrosion depends on the shape of the samples. The differences in corrosion kinetics cannot be explained by the shrinking core mechanism. They are caused by different formation rates of the passivating SiO 2 -rich layers in the corroded materials.

Zur Herstellung von Verbunden aus Kupferfolien und Keramik fur die Leistungselektronik finden silberbasierte Aktivlote Verwendung. Die sauerstoffempfindlichen Lotbestandteile (z. B. Titan) oxidieren in herkommlichen Erhitzungsmikroskopen und verhinderten ein Aufschmelzen des Lots. In dem Beitrag werden Untersuchungen mit einem neu entwickelten Erhitzungsmikroskop L74 DIL der Firma Linseis diskutiert, das im Hochvakuum (ca. 5∙10−5 mbar) arbeitet und Sauerstoffgehalte in dynamischen Atmospharen (Normaldruck, ca. 5 l/h Argon) von ca. 0,5 ppm zulasst. Dadurch kann der Schmelzprozess des Lotes und die Benetzung des Keramiksubstrates direkt beobachtet werden. Der Einsatz von thermoanalytischen Methoden zur komplexen Charakterisierung thermischer Prozesse ist ein geeigneter Weg zur Optimierung von Materialien und technischen Prozessen. Dies wird anhand der Analyse der Prozesse beim Loten von Keramik demonstriert.

Different components of hard metals such as TiC, TiN, pure Ti and the binder metals Fe, Co and Ni were investigated in neutral sodium nitrate solutions by cyclovoltammograms at current densities up to 35 A/cm 2 . All combinations of TiN and TiC dissolve anodically. The surface of pure Ti is blocked by the anodic surface oxide which is not removed by cathodic current densities up to 30 A/cm 2 . Cathodically all samples were conductive and showed a strong hydrogen evolution. The binder metals Fe, Co and Ni should be free of oxide films at cathodic potentials. Anodically, Co dissolves in an active state while Fe and Ni show a potential shift to the passive region. Our surface model developed for machining of Fe seems to be applicable to all other materials except pure Ti.

The silver paste composition for the front side has a strong influence on the firing behaviour, contact formation and resulting efficiency of the solar cell. It is state of the art that the paste glass is needed for etching the ARC silicon nitride during firing and also plays a major role for the transport of silver to the silicon surface. However, the kinetics of the silver transport is still under discussion. A main challenge to understand the underlying mechanisms is the analysis of the microstructure evolution of the paste during firing in the high speed PV firing cycle. In this work PV high speed firing conditions were simulated by usage of a simple laboratory furnace. The microstructural evolution of a model paste was observed and correlated to obtained contact resistances. Moreover, systematic variations of the paste glass were investigated. The overall contact formation kinetics can be divided into two independent but strongly interacting single kinetic phenomena: (i) the reaction kinetics at the wafer surface and (ii) the phase transport kinetics of the silver paste. The reaction kinetic at the wafer surface is composed by three important single reactions: silver solution and precipitation in the amorphous interface layer, interface layer growth, and silicon etching. The phase transport kinetics of the metallization paste determines the quantity of glass that is mixed with the etching products in the interface layer and is dominated by the densification rate of the silver powder and the viscous flow of the paste glass. The paste glass has crucial influence for both kinetics (i) and (ii). In this study the paste glass chemistry has a dominating impact compared to the glass rheology. By an appropriate choice of the raw materials regarding the sinter behaviour and targeted selection of the powder properties substantial control over the paste contacting performance is possible.