Coking behavior of nickel and a rhodium based catalyst used in steam reforming for power-to-gas applications

This paper proposes partial steam reforming of natural gas as a chemical storage option for excess electricity. Thermodynamic simulations with Aspen Plus^® show that highest process efficiencies are reached at low steam-to-carbon (S/C) ratios in the feed. However, coke deposition due to unwanted side or follow-up reactions and thus catalyst deactivation is likely in this operation range. In an experimental evaluation three catalysts were selected to test their resistance towards coking: two nickel based and one rhodium based noble metal catalyst. They were tested regarding their long-term stability at S/C ratios as low as 0 to 0.1 and reaction temperatures between 450 and 500 °C. A different reaction and deactivation behavior was observed for nickel and the noble metal catalysts. The measured life times of the noble metal catalyst were by a factor of at least 100 higher than for the two selected nickel catalysts at the applied reforming conditions. Furthermore, after each reforming experiment, a temperature-programmed oxidation (TPO) analysis was performed for the spent catalysts. Based on literature data, the measured CO₂ peaks at corresponding temperatures were related to the different forms of solid carbon depositions. Main carbonaceous species found on the nickel catalysts were of filamentous nature, whereas one or two more reactive C species with monoatomic or polymeric structure at much lower amount were detected on the noble metal catalyst. Further SEM analysis confirmed these findings.     

High‐Temperature Creep Behavior of Dense SiOC‐Based Ceramic Nanocomposites: Microstructural and Phase Composition Effects

In this work, dense monolithic polymer‐derived ceramic nanocomposites (SiOC, SiZrOC, and SiHfOC) were synthesized via hot‐pressing techniques and were evaluated with respect to their compression creep behavior at temperatures beyond 1000°C. The creep rates, stress exponents as well as activation energies were determined. The high‐temperature creep in all materials has been shown to rely on viscous flow. In the quaternary materials (i.e., SiZrOC and SiHfOC), higher creep rates and activation energies were determined as compared to those of monolithic SiOC. The increase in the creep rates upon modification of SiOC with Zr/Hf relies on the significant decrease in the volume fraction of segregated carbon; whereas the increase of the activation energies corresponds to an increase of the size of the silica nanodomains upon Zr/Hf modification. Within this context, a model is proposed, which correlates the phase composition as well as network architecture of the investigated samples with their creep behavior and agrees well with the experimentally determined data.     

Reinforcement of a Magnesium‐Ammonium‐Phosphate Cement with Calcium Phosphate Whiskers

Self‐setting resorbable phosphate cements are characterized by an excellent biocompatibility and bioactivity. However, poor mechanical properties restrict their application. Most studies which characterize phosphate cements mechanically focus on strength measurements. Examinations of mechanical reliability and facture toughness were hardly performed. In this study, calcium phosphate whisker‐reinforced magnesium‐ammonium‐phosphate (struvite) cements were examined at the whisker–matrix interface and the measured strength, reliability and toughness values were correlated to these observations. Moreover, the toughening mechanisms were evaluated. It was shown that whisker incorporation is not beneficial for material strength. It led to a strength decrease from 29.8 to 21.8 MPa by the incorporation of 15 vol% calcium‐deficient hydroxyapatite (CDHA) whiskers compared to the pure struvite cement. Weibull statistics and microstructural observations revealed that this is caused by the whisker–matrix interface, which acts as a flaw. In contrast with that, the reliability increases upon whisker incorporation. Furthermore, the critical stress intensity factor K_IC as well as the work‐of‐fracture γ_wof increase from 0.52 to 0.60 MPam^1/2 and from 9.5 to 12.9 J/m² by the addition of 15 vol% CDHA whiskers compared to the original struvite cement. It was shown that whisker pull‐out and crack deflection are the main mechanisms responsible for this increase.     

Beyond Cognitive Framing Processes: Anger Mediates the Effects of Responsibility Framing on the Preference for Punitive Measures

A new stream of research indicates that framing effects are based on emotional as well as cognitive processes. However, it is not entirely clear whether emotions mediate framing effects and what the moderators of emotional mediation processes are. To address these questions, we conducted an experiment in which the framing of responsibility for a social problem was manipulated (ambivalent vs. high‐responsibility frame). We find that the high‐responsibility frame increased the preference for punitive measures by increasing responsibility beliefs and eliciting anger. Furthermore, we find that trait anger moderates the framing effect on anger and that responsibility beliefs are positively associated with anger intensity. The significance of these findings for framing research and suggestions for future studies are discussed.     

The Effect of Gradual Fluorination on the Properties of FnZnPc Thin Films and FnZnPc/C60 Bilayer Photovoltaic Cells

Motivated by the possibility of modifying energy levels of a molecule without substantially changing its band gap, the impact of gradual fluorination on the optical and structural properties of zinc phthalocyanine (F_nZnPc) thin films and the electronic characteristics of F_nZnPc/C₆₀ (n = 0, 4, 8, 16) bilayer cells is investigated. UV–vis measurements reveal similar Q‐ and B‐band absorption of F_nZnPc thin films with n = 0, 4, 8, whereas for F₁₆ZnPc a different absorption pattern is detected. A correlation between structure and electronic transport is deduced. For F₄ZnPc/C₆₀ cells, the enhanced long range order supports fill factors of 55% and an increase of the short circuit current density by 18%, compared to ZnPc/C₆₀. As a parameter being sensitive to the organic/organic interface energetics, the open circuit voltage is analyzed. An enhancement of this quantity by 27% and 50% is detected for F₄ZnPc‐ and F₈ZnPc‐based devices, respectively, and is attributed to an increase of the quasi‐Fermi level splitting at the donor/acceptor interface. In contrast, for F₁₆ZnPc/C₆₀ a decrease of the open circuit voltage is observed. Complementary photoelectron spectroscopy, external quantum efficiency, and photoluminescence measurements reveal a different working principle, which is ascribed to the particular energy level alignment at the interface of the photoactive materials.     

Thermotropic systems with fixed domains exhibiting enhanced overheating protection performance

Within this study, a time saving photo‐initiated miniemulsion polymerization process (duration of polymerization was 15 min) was established in order to encapsulate a paraffin wax with an acrylate polymer shell. The obtained freeze‐dried latex was an off‐white powder exhibiting spherical particles with mean diameters around 400 nm and a concentration of paraffin wax around 56%. Mixing the reaction product with a UV‐curable resin matrix resulted in thermotropic overheating protection glazings with high light‐shielding efficiency. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40417.