Suchergebnisse

The up-coming strict emission legislation demands new and improved catalysts for diesel vehicle deNOx. The demand for low-temperature activity is especially challenging. H 2 -assisted NH 3 -SCR over Ag/Al 2 O 3 has shown a very promising low-temperature activity and a combination of Ag/Al2O3 and Fe-BEA can give a high NOx conversion in a broad temperature window without the need to dose H2 at higher temperatures. The aim of this study has been to investigate the combined Ag/Al 2 O 3 and Fe-BEA catalyst system both at laboratory-scale and in full-scale enginebench testing. The catalysts were combined both in a sequential dual-bed layout and a dual-layer layout where the catalysts were coated on top of each other. The Ag/Al 2 O 3 catalyst was also investigated with the aim of improving the sulphur tolerance and low-temperature activity by testing different alumina-supports. A large focus of this study has been the preparation of monolithic catalyst bricks for the catalyst testing. A high S BET and higher Ag loading gave a high sulphur tolerance and activity. It was believed that the high S BET is needed to give a higher NH 3 adsorption capacity, necessary for the SCR reaction. A higher Ag loading gives more Ag sites and probably a favourable Ag dispersion. Testing with sulphur gave an increased activity of the catalysts. Testing of monolithic catalysts showed a similar activity enhancement after a few standard test cycles. A change in the dispersion or state of Ag can be possible reasons for the activation seen and the activation was believed to be related to Ag and not the alumina. Small-scale laboratory testing showed that it was preferred to have Ag/Al 2 O 3 either upstream or as the outer layer of Fe-BEA. This was attributed to complete NH 3 oxidation over Fe-BEA giving a deficit of NH 3 over the Ag/Al 2 O 3 if it was placed downstream or as the inner layer. Full-scale engine testing, on the other hand, showed the opposite for a dual-brick layout. High NO 2 concentrations are believed to give fast-SCR over the Fe-BEA when it was placed upstream of the Ag/Al 2 O 3 . The activity of the combined catalyst layouts were higher than the activity for individual catalysts when less or no H 2 was co-fed in the small-scale case showing that there were synergistic effects by combining them. The dual-layer layout showed the best performance which is believed to be attributed the short diffusion distance between the layers allowing diffusion of reaction intermediates between them. Ag/Al 2 O 3 only and the combined Ag/Al 2 O 3 – Fe-BEA systems were active during the transient NEDC. The NO x conversions were not very high which is related to the very low temperature of the NEDC and the lower than expected activity of the Ag/Al 2 O 3 catalyst seen in stationary testing. The most interesting result was that the catalyst systems showed NOx conversion already from the start of the cycle, before any NH3 or H2 was dosed. NO x storage over the Ag/Al2O3 was believed to be the most likely explanation for this. The NOx conversion could be enhanced by dosing of NH 3 and H 2 at temperatures lower than 150°C that was used as standard starting temperature of dosing. However, dosing too early inhibited the NO x conversion.

Result of the first ozone monitoring in ambient air Nature Park of Kopacki Rit (Eastern Croatia) are reported for the growth season in 2008. The measured hourly concentrations of ozone in the air do not exceed the limit value of 110 mu g m(-3) statutory regulation by Croatian legalization for the protection of human health. There were only 13 days exceeding of the target value of 120 mu g m(-3) (8-h averages) as established in the European Union guidelines on ozone pollution in ambient air. In contrast to the measured AOT40 whose value does not exceed the critical level of 18 000 (mu g m(-3)).h for vegetation injury, an estimated AOT40 value was somewhat higher. The relationships between O-3 and meteorological variables were investigated by a principal component analysis (PCA). Fourier analysis methods applied to ozone concentrations data showed that the most important variations in the O-3 data are represented by usual daily cycles.

In der Studie geht es um die Einschätzungen verschiedener Staaten und nationaler Gruppen durch Schüler und Schülerinnen der Klassen 8 bis 10. Zur Einschätzung der Staaten VR Polen, BRD, UdSSR, USA und DDR werden zehn aktuelle und relevante gesellschaftliche Faktoren vorgegeben, die eine relativ breit gefächerte Beurteilung dieser Staaten erlauben. Neben sehr aktuellen Bereichen, wie z.B. zu den Problemen der Abrüstung und der Sicherung der Menschenrechte, werden auch solche Fragen berücksichtigt, die zum Teil traditionelle und historisch begründete Einstellungen erfassen. (ICA)

Infrared transparent electrodes (IR-TEs) have recently attracted much attention for industrial and military applications. The simplest method to obtain high IR transmittance is to reduce the electrode film thickness. However, for films several tens of nanometres thick, this approach unintentionally suppresses conduction due to surface electron scattering. Here, we demonstrate low sheet resistance (65% at the 2.5-μm wavelength) in Sn-doped In(2)O(3) (ITO) epitaxial films for the thickness range of 17−80 nm. A combination of X-ray spectroscopy and ellipsometry measurements reveals a persistent electronic bandstructure in the 8-nm-thick film compared to much thicker films. This indicates that the metallicity of the film is preserved, despite the ultrathin film configuration. The high carrier mobility in the ITO epitaxial films further confirms the film's metallicity as a result of the improved crystallinity of the film and the resulting reduction in the scattering defect concentration. Thus, ITO shows great potential for IR-TE applications of transparent photovoltaic and optoelectronic devices.

(Al,Cr)(2)O-3 coatings with Al/( Al + Cr) = 0.5 or Al = 70 at. %, doped with 0, 5, or 10 at. % Si, were deposited on hard metal and Si(100) substrates to elucidate the influence of Si on the resulting coatings. The chemical analysis of the coatings showed between 3.3 and 7.4 at. % metal fraction Si incorporated into all studied coatings depending on cathode Si composition. The incorporated Si content does not change significantly with different oxygen flows covering a wide range of deposition conditions from low to high O-2 flow during growth. The addition of Si promotes the metastable B1-like cubic structure over the thermodynamically stable corundum structure. The hardness determined by nanoindentation of the as-deposited coatings is slightly reduced upon Si incorporation as well as upon increased Al content. Si is found enriched in droplets but can also be found at a lower content, evenly spread, without visible segregation at the similar to 5 nm scale, in the actual oxide coating. The positive effect of improved cathode erosion upon Si incorporation has to be balanced against the promotion of the metastable B1-like structure, having lower room temperature hardness and inferior thermal stability compared to the corundum structure. Published by the AVS. ; Funding Agencies|Swedish Research Council (VR)Swedish Research Council [621-212-4368, 330-2014-6336, 2018-03957]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation [KAW2016.0358]; Marie Sklodowska Curie Actions, Cofund [INCA 600398]; Swedish Foundation for Strategic Research (SSF) through the Future Research Leaders 6 program; Swedish Research Council VR-RFISwedish Research Council [821-2012-5144, 2017-00646_9]; Swedish Foundation for Strategic Research (SSF)Swedish Foundation for Strategic Research [RIF14-0053]; VINNOVAVinnova [2018-04290]

The rapid pace of development for hybrid perovskite photovoltaics has recently resulted in promising figures of merit being obtained with regard to device stability. Rather than relying upon expensive barrier materials, realizing market-competitive lifetimes is likely to require the development of intrinsically stable devices, and to this end accelerated aging tests can help identify degradation mechanisms that arise over the long term. Here, oxygen-induced degradation of archetypal perovskite solar cells under operation is observed, even in dry conditions. With prolonged aging, this process ultimately drives decomposition of the perovskite. It is deduced that this is related to charge build-up in the perovskite layer, and it is shown that by efficiently extracting charge this degradation can be mitigated. The results confirm the importance of high charge-extraction efficiency in maximizing the tolerance of perovskite solar cells to oxygen. ; This work was supported by SABIC and by the EPSRC, including by the Supergen Supersolar Consortium (EP/J017361/1) and the European Union Seventh Framework Program [FP7 2007-2003] under grant agreement 604032 of the MESO project. GE is supported by the EPSRC and Oxford Photovoltaics Ltd. through a Nanotechnology KTN CASE award. JW acknowledges the Swire Educational Trust for supporting his D.Phil. study at Oxford. We thank Sian Dutton (University of Cambridge) for access to XRD facilities and Felix Deschler (University of Cambridge) for helpful discussions. ; This is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1002/aenm.201600014