Publikationen

The electrodeposition of aluminum-nickel coatings was performed by pulsed direct current in the ionic liquid (IL) 1.5:1 AlCl3:EMIm]Cl containing nickel nanoparticles (Ni NPs), for reactive dispersion coating application. Several electrochemical and characterization techniques were used to shed more light on the mechanism of Ni particle incorporation into the Al matrix. Thus, particle incorporation at the early stage of the deposition would mainly take place via particle adsorption at the substrate. However, as the thickness of the coating increases, it seems that the main mechanism for particle incorporation is via the reduction of ions adsorbed at the particles surface. Although a considerable high incorporation of Ni NPs has been achieved from the IL containing the highest concentration of Ni NPs (i.e. ∼33 wt% from a 20 g/L of Ni NPs bath), a high concentration of NPs in the IL resulted having a negative effect in terms of quality of the coatings, due to solidification of the electrolyte in a poorly conductive compound. Moreover, almost equivalent amounts of Ni and Al (Ni ∼45 wt.%and Al ∼44 wt.%) have been detected in some areas of the coatings. Such a layer composition would be desired for the targeted application.

In metal-air batteries, the integrated solid-state cathode is considered a promising design because it can solve the problem of high interfacial resistance of conventional solid-state cathodes. However, solid discharge products cannot be efficiently decomposed in an integrated solid-state cathode, resulting in batteries that are unable to operate for long periods of time. Herein, an integrated solid-state cathode (Gel-Tempo cathode) of sodium-air batteries (SABs) capable of promoting efficient decomposition of discharge product Na2O2 is designed. The Gel-Tempo cathode is synthesized by cationic-π interaction of redox mediator 2,2,6,6-tetramethyl-1-piperidinyloxy (Tempo) and ionic liquid with carbon nanotubes. The Gel-Tempo cathode serves multiple functions as a redox mediator, flame retardancy, and high stability to air. In quasi-solid-state SABs, the Gel-Tempo cathode reduces overpotential to 1.15 V and improves coulomb efficiency to 84.5% (at a limited discharge capacity of 3000 mAh g−1) compared to gel cathodes. Experiments and density functional theory calculations indicate that Tempo significantly reduces the Gibbs free energy in the decomposition reaction of Na2O2, and high Tempo content is more conducive to enhancing the decomposition kinetics of Na2O2 and hence resulting in an ultra-long cycle life (1746 h). This work is crucial to promote practical applications of SABs, providing guidelines for functionalization design of integrated solid-state cathodes for metal-air batteries.

Cholesterin hat es bis in den Alltagssprachgebrauch gebracht. Allein deshalb ist es für Praktika im Chemiestudium ein interessanter Vertreter der Steroide. Zudem ist es einfach zu gewinnen.

In reservoir rocks, the term “ageing” refers to extended exposition to crude oil; a typically water-wet sandstone will then gradually become oil-wet as a consequence of the deposition of insoluble fractions of oil onto the surface grains. Rocks have been aged artificially by subjecting them to a bitumen solution at elevated temperature in order to achieve comparable surface properties for three different types of rock: Bentheimer, Berea Buff and Liège Chalk. Using saturated and aromatic model compounds as proxies for crude oil, the nuclear magnetic resonance (NMR) relaxation dispersion in native and aged rocks was compared and correlated to the properties of paramagnetic impurities in these rock types. Perfluorated liquids were found to follow the same trend as deuterated and naturally occurring oil components, suggesting they can be used as suitable tracers for wettability studies since the 19F nucleus is absent in natural sources. By combining electron paramagnetic resonance (EPR) and dynamic nuclear polarization (DNP) it becomes possible to identify and quantify the origin of the dominating relaxation processes between native and aged rocks, providing an alternative approach to assess wettability in natural rocks.

Real-time surveillance is a crucial element in the response to infectious disease outbreaks. However, the interpretation of incidence data is often hampered by delays occurring at various stages of data gathering and reporting. As a result, recent values are biased downward, which obscures current trends. Statistical nowcasting techniques can be employed to correct these biases, allowing for accurate characterization of recent developments and thus enhancing situational awareness. In this paper, we present a preregistered real-time assessment of eight nowcasting approaches, applied by independent research teams to German 7-day hospitalization incidences during the COVID-19 pandemic. This indicator played an important role in the management of the outbreak in Germany and was linked to levels of non-pharmaceutical interventions via certain thresholds. Due to its definition, in which hospitalization counts are aggregated by the date of case report rather than admission, German hospitalization incidences are particularly affected by delays and can take several weeks or months to fully stabilize. For this study, all methods were applied from 22 November 2021 to 29 April 2022, with probabilistic nowcasts produced each day for the current and 28 preceding days. Nowcasts at the national, state, and age-group levels were collected in the form of quantiles in a public repository and displayed in a dashboard. Moreover, a mean and a median ensemble nowcast were generated. We find that overall, the compared methods were able to remove a large part of the biases introduced by delays. Most participating teams underestimated the importance of very long delays, though, resulting in nowcasts with a slight downward bias. The accompanying prediction intervals were also too narrow for almost all methods. Averaged over all nowcast horizons, the best performance was achieved by a model using case incidences as a covariate and taking into account longer delays than the other approaches. For the most recent days, which are often considered the most relevant in practice, a mean ensemble of the submitted nowcasts performed best. We conclude by providing some lessons learned on the definition of nowcasting targets and practical challenges.