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Klein T.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Klein T.,Institute for Corrosion Protection Dresden | Zihlmann D.,Eawag - Swiss Federal Institute of Aquatic Science and Technology | Zihlmann D.,ETH Zurich | And 10 more authors.
Water Research | Year: 2016

Traditionally, chemical and physical methods have been used to control biofouling on membranes by inactivating and removing the biofouling layer. Alternatively, the permeability can be increased using biological methods while accepting the presence of the biofouling layer. We have investigated two different types of metazoans for this purpose, the oligochaete Aelosoma hemprichi and the nematode Plectus aquatilis. The addition of these grazing metazoans in biofilm-controlled membrane systems resulted in a flux increase of 50% in presence of the oligochaetes (Aelosoma hemprichi), and a flux increase of 119-164% in presence of the nematodes (Plectus aquatilis) in comparison to the control system operated without metazoans. The change in flux resulted from (1) a change in the biofilm structure, from a homogeneous, cake-like biofilm to a more heterogeneous, porous structure and (2) a significant reduction in the thickness of the basal layer. Pyrosequencing data showed that due to the addition of the predators, also the community composition of the biofilm in terms of protists and bacteria was strongly affected. The results have implications for a range of membrane processes, including ultrafiltration for potable water production, membrane bioreactors and reverse osmosis. © 2015 Elsevier Ltd. Source

Berger L.-M.,Fraunhofer Institute for Ceramic Technologies and Systems | Toma F.-L.,Fraunhofer Institute for Material and Beam Technology | Scheitz S.,TU Dresden | Trache R.,Fraunhofer Institute for Material and Beam Technology | And 2 more authors.
Materialwissenschaft und Werkstofftechnik | Year: 2014

With exception of ZrO2, the individual oxides and binary compositions in the system Al2O3-Cr2O 3-TiO2 are the most important oxide materials for the preparation of thermally sprayed coatings. In this contribution selected results of recent own research activities are summarized. This includes the comparison of microstructures, phase compositions, and properties of coatings, deposited by atmospheric plasma spraying (APS) and high velocity oxy-fuel (HVOF) spraying. The possibilities arriving from the use of suspensions as feedstock are reviewed. Special attention is paid to the advantage of use of binary compositions in this system. Tribological, electrical and corrosion properties of the coatings are discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Bolelli G.,University of Modena and Reggio Emilia | Borner T.,University of Modena and Reggio Emilia | Borner T.,Institute for Corrosion Protection Dresden | Milanti A.,University of Modena and Reggio Emilia | And 6 more authors.
Surface and Coatings Technology | Year: 2014

Fe-based coatings are promising alternatives to Ni-based ones, because of lower cost and lower toxicity. Following a previous research, where the sliding wear resistance of HVOF-sprayed Fe-Cr-Ni-Si-B-C alloy coatings was found to compare favorably with that of a Ni-Cr-B-Si-C alloy and of electroplated chromium, the present study investigates the wear resistance of Fe-Cr-Ni-Si-B-C. +. WC-Co composite coatings. The Fe-alloy feedstock powder was therefore blended with 0, 20 and 40. wt.% of a WC-12. wt.% Co powder and sprayed by HVOF and HVAF processes. HVAF-sprayed coatings exhibit less structural alteration than HVOF-sprayed ones, which results in lower intrinsic nanohardness of both Fe-alloy and WC-Co splats; however, HVOF- and HVAF-sprayed coatings exhibit similar Vickers microhardness. Somewhat poorer interlamellar bonding in HVAF-sprayed coatings results in a greater tendency to microcracking during dry sliding wear testing at room temperature; however, dry sliding wear rates of HVOF- and HVAF-sprayed samples never differ significantly. The reinforcing effect of WC-Co decreases the wear rate of composite coatings (≈10-6mm3/(Nm)) by more than order of magnitude, compared to unreinforced ones (≈1-2*10-5mm3/(Nm)).As the test temperature is increased to 400°C and 700°C, the dry sliding wear rates of all samples increase (up to 10-4mm3/(Nm) or greater). The greatest changes are observed when the WC-Co content is larger, as it suffers from oxidation and thermal alteration more than the Fe-alloy matrix. The abrasive wear resistance of the Fe-based coatings, evaluated by rubber-wheel testing, is also significantly improved by the addition of WC-Co. © 2014 Elsevier B.V. Source

Potthoff A.,Fraunhofer Institute for Ceramic Technologies and Systems | Weil M.,ECT Oekotoxikologie GmbH | Meissner T.,Fraunhofer Institute for Ceramic Technologies and Systems | Meissner T.,Institute for Corrosion Protection Dresden | Kuhnel D.,Helmholtz Center for Environmental Research
Science and Technology of Advanced Materials | Year: 2015

During the last decade, nanomaterials (NM) were extensively tested for potential harmful effects towards humans and environmental organisms. However, a sound hazard assessment was so far hampered by uncertainties and a low comparability of test results. The reason for the low comparability is a high variation in the (1) type of NM tested with regard to raw material, size and shape and (2) procedures before and during the toxicity testing. This calls for tailored, nanomaterial-specific protocols. Here, a structured approach is proposed, intended to lead to test protocols not only tailored to specific types of nanomaterials, but also to respective test system for toxicity testing. There are existing standards on single procedures involving nanomaterials, however, not all relevant procedures are covered by standards. Hence, our approach offers a detailed way of weighting several plausible alternatives for e.g. sample preparation, in order to decide on the procedure most meaningful for a specific nanomaterial and toxicity test. A framework of several decision trees (DT) and flow charts to support testing of NM is proposed as a basis for further refinement and in-depth elaboration. DT and flow charts were drafted for (1) general procedure - physicochemical characterisation, (2) choice of test media, (3) decision on test scenario and application of NM to liquid media, (4) application of NM to the gas phase, (5) application of NM to soil and sediments, (6) dose metrics, (S1) definition of a nanomaterial, and (S2) dissolution. The applicability of the proposed approach was surveyed by using experimental data retrieved from studies on nanoscale CuO. This survey demonstrated the DT and flow charts to be a convenient tool to systematically decide upon test procedures and processes, and hence pose an important step towards harmonisation of NM testing. © 2015 National Institute for Materials Science. Source

Gehrke J.,Institute for Corrosion Protection Dresden | Lebelt P.,Institute for Corrosion Protection Dresden
Stahlbau | Year: 2015

The usage of corrosion protection systems, consisting of organic or metallic coatings, are comprehensively described in partly extensive technical rules for the application on thin metal sheets (3 mm sheet thickness maximum) up to massive steel structures with ultimate limit state design. After determining of existing on-site corrosion category and defining the desired term of protection time, the appropriate corrosion protection systems for a particular object can be selected from tables. Furthermore, numerous comments can be found for corrosion-resistant construction, for surface preparation and pretreatment of the substrate and the processing conditions of the corrosion protection system in the relevant regulations. A professional corrosion protection for steel structures must be carried out by implementation of technical rules mentioned in quality assurance measures, both in planning and in the execution of corrosion protection work. © 2015 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. Source

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