Solid-liquid phase coexistence and structural transitions in palladium clusters

We use molecular dynamics with an embedded atom potential to study the behavior of palladium nanoclusters near the melting point in the microcanonical ensemble. We see transitions from both fcc and decahedral ground state structures to icosahedral structures prior to melting over a range of cluster sizes. In all cases this transition occurs during solid-liquid phase coexistence and the mechanism for the transition appears to be fluctuations in the molten fraction of the cluster and subsequent recrystallization into the icosahedral structure.Comment: 8 pages, 6 figure

Pressurized single cell testing of solid oxide cells

Pressurized operation of Solid Oxide Cells (SOCs) enhances the performance in the fuel cell mode and is mandatory for coupling with gas turbines. For electrolysis, energy demand and balance of plant to pressurize hydrogen or syngas can be reduced. Today’s facilities for pressurization of SOCs rely on voluminous pressure vessels that enclose the cells/stacks. Inside such vessel, fuel- and oxidant pressures have to match the vessel pressure to avoid a deterioration of the cells/stacks. Here, a single cell is operated without a pressure vessel in a metallic cell housing sealed towards the cell by a glass-ceramic sealant. Any differential pressure is avoided by a downstream combustor, an approach that is limited to test benches. In our experiments we found that this sealing concept can withstand pressure drops of up to 10 bar towards ambient pressure even after a full thermal cycle. As to be expected from numerous previous studies, open-circuit voltage as well as performance increased signifi- cantly with increasing pressure. The power density increased by 20 % in air/dry H2 at 850 ◦C and 11 bar

Probing the effect of surface strain on CO binding to Pd thin films.

We report measurements to investigate the effects of mechanical strain on the binding energy of carbon monoxide (CO) on the (111) surface of a 16 nm thin film of palladium (Pd) grown on rutile titanium dioxide (r-TiO2). The lattice mismatch between Pd and the r-TiO2 leads to a tensile mechanical in-plane stress in the Pd layer of approximately 0.38 GPa. We observe an increase of (40 ± 10) kJ mol–1 in the CO binding energy for the 16 nm sample compared to a bulk Pd(111) crystal, which is in qualitative agreement with expectations based on the d-band model

Validation of SCIAMACHY tropospheric NO₂-columns with AMAXDOAS measurements

International audienceTropospheric NO2 vertical and slant columns from the new satellite instrument SCIAMACHY on ENVISAT are validated by measurements of the Airborne Multi AXis DOAS (AMAXDOAS) instrument on board the DLR Falcon. The results presented here were obtained in February 2003 on a flight over the Alps, the Po-Valley and the Mediterranean. The tropospheric vertical column measured by AMAXDOAS varied between 16.2 and 35.2*1015molec/cm2 over the Po-Valley where SCIAMACHY data resulted in 19.9 to 37*1015molec/cm2. Over less polluted areas a similarly good agreement was found. The linear correlation between the two datasets results in a slope of 0.93. The slight differences observed can be attributed to the different spatial resolution and the temporal mismatch between the measurements over the Po-Valley

Skelettmotor Schlussbericht

With 15 refs., 61 figs.Available from Volkswagenwerk A.G., Wolfsburg (DE). Forschung Aggregatetechnik und Messtechnik / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman