Co-Mn oxides supported on hierarchical macro-mesoporous silica for CO and VOCs oxidation

The hierarchical macro-mesoporous silica (MMS) was used for a first time as a support for catalysts for oxidation reactions. The macro-mesoporous silica was synthesized by the emulsions templating mechanism and modified separately or simultaneously using cobalt and manganese oxides. The obtained materials were characterized by different physicochemical methods and tested in the oxidation of CO and n-hexane combustion reactions. The modification of the MMS materials does not change significantly the mesopores characteristics; however, its pores are partially blocked by the oxides. For Co-MM sample agglomerates consisting of Co3O4 with average size of 100−150 nm and small spherical aggregates, encapsulated in the mesopores are formed. The amorphous manganese oxide preferentially fills up the mesopores in Mn-MM sample. Mixed oxide Co-Mn phases situated in the mesoporous network are formed in the bi-component Co-Mn samples. No significant change is observed either in the texture, or in the structural features of the catalysts after reaction. The highest catalytic activity for Co-MM sample in CO and n-hexane oxidation is related to the predomination of Co3+ species on the surface of Co3O4 and the more accessible oxide particles located outside the mesopores. The encapsulation of mixed Co-Mn oxides particles in the pores of the macro-mesoporous silica is responsible for a lower catalytic activity in comparison with that of the mono-component cobalt sample

The Sariçiçek Howardite Fall in Turkey: Source Crater of HED Meteorites on Vesta and İmpact Risk of Vestoids

The Sariçiçek howardite meteorite shower consisting of 343 documented stones occurred on 2 September 2015 in Turkey and is the first documented howardite fall. Cosmogenic isotopes show that Sariçiçek experienced a complex cosmic ray exposure history, exposed during ~12–14 Ma in a regolith near the surface of a parent asteroid, and that an ~1 m sized meteoroid was launched by an impact 22 ± 2 Ma ago to Earth (as did one third of all HED meteorites). SIMS dating of zircon and baddeleyite yielded 4550.4 ± 2.5 Ma and 4553 ± 8.8 Ma crystallization ages for the basaltic magma clasts. The apatite U-Pb age of 4525 ± 17 Ma, K-Ar age of ~3.9 Ga, and the U,Th-He ages of 1.8 ± 0.7 and 2.6 ± 0.3 Ga are interpreted to represent thermal metamorphic and impact-related resetting ages, respectively. Petrographic, geochemical and O-, Cr- and Tiisotopic studies confirm that Sariçiçek belongs to the normal clan of HED meteorites. Petrographic observations and analysis of organic material indicate a small portion of carbonaceous chondrite material in the Sariçiçek regolith and organic contamination of the meteorite after a few days on soil. Video observations of the fall show an atmospheric entry at 17.3 ± 0.8 kms-1 from NW, fragmentations at 37, 33, 31 and 27 km altitude, and provide a pre-atmospheric orbit that is the first dynamical link between the normal HED meteorite clan and the inner Main Belt. Spectral data indicate the similarity of Sariçiçek with the Vesta asteroid family (V-class) spectra, a group of asteroids stretching to delivery resonances, which includes (4) Vesta. Dynamical modeling of meteoroid delivery to Earth shows that the complete disruption of a ~1 km sized Vesta family asteroid or a ~10 km sized impact crater on Vesta is required to provide sufficient meteoroids ≤4 m in size to account for the influx of meteorites from this HED clan. The 16.7 km diameter Antonia impact crater on Vesta was formed on terrain of the same age as given by the 4He retention age of Sariçiçek. Lunar scaling for crater production to crater counts of its ejecta blanket show it was formed ~22 Ma ago

Structural, Optical and Electrical Properties of Multilayer Stacks ZnO:Al/Ag/ZnO:Al and ZrO2/Ag/ZrO2

AbstractStructural, optical and electrical properties of multilayer stacks ZnO:Al/Ag/ZnO:Al and ZrO2/Ag/ZrO2 are studied. The stacks are deposited on glass substrates without heating by r.f. magnetron sputtering consecutively of ZnO:Al and Ag or ZrO2 and Ag targets, respectively. The properties of the as-deposited and annealed in forming gas atmosphere, at 1800C for 1h are compared. The structural properties of the stacks are studied by TEM and SEM images and demonstrate semi-continuous granular structure of the Ag films. The Ag nanograins in ZrO2 based stacks have a larger size than in the ZnO based stacks. The spectra of transmittance and reflectance have bands resulting from interband transitions of d-shell electrons of Ag atoms and plasma resonance oscillations of free electrons. The sheet resistance of the as-deposited and annealed stacks is in the range 3.1-8.9Ω/□ and slightly changes after annealing. The deposited stacks have potential for application as a back reflector in thin film solar cells for improvement of light harvesting and their efficiency

Nanosecond laser ablation of composite thin films in liquid

Abstract We present a study on nanosecond laser ablation of thin composite films immersed in liquids. The composite films are obtained using a classical on-axis pulsed laser deposition technology, where the target consists of two sectors with different composition. Multicomponent films containing ZnO, TiO2, and Ag, are thus deposited on a substrate. The as-prepared composite films are then immersed in double distiled water and irradiated by nanosecond laser pulses. This results in the production of colloids composed by multicomponent nanoparticles. The optical properties of the colloids are evaluated by optical transmittance measurements in the UV-VIS spectral range. Transmission electron microscopy is used to visualize the nanostructures formed in the solution, as well as to evaluate their size distribution. The phase composition of the samples is determined by selected area electron diffraction.</jats:p