Impact of spinel forming systems (Fe-/Mg-/Mn-Al-O) as functional coating materials for carbon-bonded alumina filters on steel melt filtration

Since solid, non-metallic inclusions influence considerably the quality of casted steel products, carbon-bonded alumina foam filters are used in secondary metallurgical treatments to remove these particles from steel melts. In order to attain a significant improvement of the filtration process, five different carbonaceous spinel compounds from the Fe-/Mg-/Mn-Al-O systems are applied on carbon-bonded alumina filters in this study and investigated with regard of their filtration efficiency. However, these spinel compounds decompose partially during sintering at 1400?°C under reducing atmosphere, wherefore the resulting coatings contain not only spinel compounds, but also oxidic and metallic components. The subsequent interaction with molten steel leads to the development of multicrystal structures on the filter surface, which stem from interfacial reactions between coating materials, molten steel, and inclusions. As a result of this procedure, a reduction of almost 60% alumina inclusions is measured with the aid of an automatic SEM, whereby spinel compounds from the Fe-Mn-Al-O system achieve highest filtration efficiencies.     

Nitrification and denitrification as a source for NO and NO2 production in high-strength wastewater

Laboratory and half-technical scale experiments were performed to evaluate nitric oxide (NO) and nitrogen dioxide (NO2) production during biological N-elimination from wastewater with high ammonium concentration (about 700 mg N L-1). In a laboratory scale bioreactor with biomass retention, the ammonia oxidizer Nitrosomonas europaea and the denitrifier Paracoccus denitrificans were grown as reference organisms in co-culture in order to simulate the nitrifying and denitrifying community of wastewater treatment plants. Synthetic wastewater and sludge liquor from the municipal wastewater treatment plant in Lueneburg (Germany) were used. In the laboratory scale reactor, during the treatment of synthetic wastewater, 0.28% of the oxidized ammonium-N was released as NO-N by a pure culture of Nitrosomonas. A simultaneously nitrifying and denitrifying co-culture only released 0.04 to 0.2%. NO2 formation was not observed. NO production was much higher in sludge liquor. A pure culture of Nitrosomonas produced 0.52% NO + NO2-N (= NOx-N), a co-culture of Nitrosomonas and Paracoccus even 1.64% NOx-N. The production rate strongly depended on the media and the organisms used. In a co-culture of N. europaea and P denitrificans, Nitrosomonas was shown to be the most efficient NO producer. NO production increased with ammonium oxidation rate and with nitrite concentration of the medium. In synthetic wastewater, NO production was not influenced by reduced oxygen content. However, in sludge liquor NO production rate increased with decreasing O2 concentration. Here, for the first time, the formation of significant amounts of NO2 during simultaneous nitrification/denitrification could be demonstrated. In half-technical scale experiments, only 0.07% of the oxidized ammonium-N was released as NO-N from the nitrification stage. NO2 was not detectable. Release of nitric oxide from the denitrification stage was mainly diffusion limited and the amount produced did not exceed 0.0001%. A calculation on the basis of the results presented, revealed that biological treatment of nitrogen-rich wastewater is not a significant source for pollution of the atmosphere with NOx in industrial areas.     

A Comparison of Multiple-Exposure Methods of Sensitizing Photographic Emulsions for Short Duration Exposures

Multiple-exposure methods of sensitizing photographic emulsions for recording light flashes of less than 10^-4 seconds duration were compared. Hypersensitization could not be used because of the graininess produced. Maximum emulsion sensitivity for the photography of large objects was obtained by using a combination of high intensity pre-exposure (of less than 10^-4 seconds duration), and subsequent post-exposure with very low intensity light. A 3.4-fold increase in sensitivity was obtained. Both high intensity pre-exposure, and low intensity post-exposure were more effective than pre-fogging. For the photography of very fine objects the total developed density and the graininess must be kept to a minimum. It appears that high intensity pre-exposure and low intensity post-exposure will give optimum results when the sensitizing exposures produce density changes of approximately 0.03 and 0.10, respectively.     

Fabrication of periodically aligned vertical single-crystalline anatase TiO2 nanotubes with perfect hexagonal open-ends using chemical capping materials

A vertically aligned anatase TiO2 （A-TiO2） nanotube array has been fabricated by coating a ZnO nanorod （NR） template with a TiO2 precursor solution. After coating, the ZnO NR cores were selectively etched in an acidic environment to form TiO2 nanotubes （NTs）. More specifically, after growing the ZnO NRs via a hydrothermal method, one drop of the TiO2 precursor solution was cast to coat the ZnO NRs, the tops of which were previously covered with chemical capping materials by electrostatic interaction, and then the sample was sintered. Finally, the sample was immersed in an acidic solution resulting in selective etching of the ZnO NR cores. Thus, only TiO2 NTs remained on the substrate. The capping material is effectively used to create a perfect, hexagonal open-ended TiO2 NT array, which interestingly extends onset absorption towards the visible region.     

Characterization and Physical Explanation of Energetic Particles on Planck HFI Instrument

The Planck High Frequency Instrument (HFI) has been surveying the sky continuously from the second Lagrangian point (L2) between August 2009 and January 2012. It operates with 52 high impedance bolometers cooled at 100 mK in a range of frequency between 100 GHz and 1 THz with unprecedented sensitivity, but strong coupling with cosmic radiation. At L2, the particle flux is about 5 \(\hbox {cm}^{-2}\,\hbox {s}^{-1}\) and is dominated by protons incident on the spacecraft. Protons with an energy above 40 MeV can penetrate the focal plane unit box causing two different effects: glitches in the raw data from direct interaction of cosmic rays with detectors (producing a data loss of about 15 % at the end of the mission) and thermal drifts in the bolometer plate at 100 mK adding non-Gaussian noise at frequencies below 0.1 Hz. The HFI consortium has made strong efforts in order to correct for this effect on the time ordered data and final Planck maps. This work intends to give a view of the physical explanation of the glitches observed in the HFI instrument in-flight. To reach this goal, we performed several ground-based experiments using protons and \(\alpha \) particles to test the impact of particles on the HFI spare bolometers with a better control of the environmental conditions with respect to the in-flight data. We have shown that the dominant part of glitches observed in the data comes from the impact of cosmic rays in the silicon die frame supporting the micro-machined bolometric detectors propagating energy mainly by ballistic phonons and by thermal diffusion. The implications of these results for future satellite missions will be discussed.