Influences of roll-to-roll process and polymer substrate anisotropies on the tensile failure of thin oxide films

The influence of internal stress anisotropy resulting from anisotropic loading in a roll-to-roll (R2R) process, and polymer substrate anisotropy on the crack onset strain (COS) of thin oxide coatings was analyzed. Experimental data obtained for R2R processed films were compared with data obtained using an isotropic sheet-to-sheet (S2S) process with the same anisotropic substrate. In the R2R case the COS was found to increase by 20% between the transverse direction and the machine direction. In the S2S case the COS was found to be independent of orientation, except at a 45° in-plane orientation with respect to the machine direction, where it was 15% higher. The internal stress in the machine direction could not be determined, presumably due to deposition-induced curvature changes of the polymer substrate, and was therefore fitted to the COS data. Fracture mechanics analysis and finite element modeling of the experimental data showed that the influence of substrate anisotropy was marginal, and that it was the process-induced internal strain in the coating which controlled the COS. © 2010 Elsevier B.V

Die Rolle der Gasdiffusionselektroden in der Zink‐Luft‐ und Lithium‐Luft‐Batterie

Metall‐Luft‐Batterien, v. a. als wiederaufladbare Variante, sind branchenübergreifend derzeit von großem Interesse. Neben dem potenziell kostengünstigen Zink‐Luft‐System hat in den vergangenen zehn Jahren das potenziell hochenergetische Lithium‐Luft‐System große Aufmerksamkeit erfahren, das ursprünglich als Hochenergiespeicher für die Elektromobilität gedacht war. In diesem Beitrag wird der Fokus auf wiederaufladbare Zink‐Luft‐ und Lithium‐Luft‐Systeme gelegt. Insbesondere wird die Rolle der Gasdiffusionselektrode beschrieben sowie ein Ausblick über aktuelle Trends bei der Weiterentwicklung gegeben

Investigation of the degradation mechanisms of silicon thin film anodes for lithium-ion batteries

Silicon is a promising material for negative electrodes in lithium-ion batteries. The degradation of silicon was investigated using thin films between 5 and 50 nm deposited on substrates of varying roughness. We used differential capacity plots to examine the degradation behavior of thin films during cycling. We found that the delamination of the thin films from the substrate depends on the surface roughness and film thickness. The delamination changes the morphology of the thin film and is characterized through the formation of Li15Si4. The morphology change is also accompanied by reduced coulombic efficiency and an increasing cell polarization. The transient occurrence of Li15Si4 is explained by the processes during cycling. It may be prevented by stress induced potential suppression which was observed in very thin films as the polarization increases with decreasing layer thickness

Investigation of electron transfer properties of the SEI on metallic lithium electrodes by SECM at open circuit

The electron transfer at metallic lithium was characterized using the feedback mode of scanning electrochemical microscopy (SECM) and 2,5-di-tert-butyl-1,4-dimethoxybenzene (DBDMB) as redox mediator at open circuit. As a result the solid electrolyte interphase (SEI) at Li is not passivating towards DBDMB as redox mediator. In comparison to charged graphite composite electrodes, the electron transfer rate is smaller at Li and the ranges for the electron transfer rates at both electrodes overlap. Both, graphite composite and Li electrodes show a local variation of electron transfer rates and temporal changes within a time span of hours. In addition, significant short term changes of SEI passivity occur at both electrodes. However, the frequency of such events is smaller for metallic Li then on graphite

Verhalten von Gesamtöstriol, nichtkonjugiertem Östriol, Human Placenta Lactogen und Oxytocinase im Serum sowie der Gesamtöstrogene im Urin von schwangeren Frauen nach Gabe von Betamethason

Peer Reviewe