TY - JOUR A1 - Huang, K. A1 - Liu, H. A1 - Kraft, Marco A1 - Shikha, S. A1 - Zheng, X. A1 - Agren, H. A1 - Würth, Christian A1 - Resch-Genger, Ute A1 - Zhang, Y. T1 - A protected excitation-energy reservoir for efficient upconversion luminescence N2 - Lanthanide-doped upconversion nanoparticles (UCNPs) are of great interest for biomedical applications. Currently, the applicability of UCNP bionanotechnology is hampered by the generally low luminescence intensity of UCNPs and inefficient energy Transfer from UCNPs to surface-bound chromophores used e.g. for photodynamic therapy or analyte sensing. In this work, we address the low-Efficiency issue by developing versatile core-Shell nanostructures, where high-concentration sensitizers and activators are confined in the core and Shell Region of representative hexagonal NaYF2:Yb,Er UCNPs. After Doping concentration optimization, the sensitizer-rich core is able to harvest/accumulate more excitation energy and generate almost one order of Magnitude higher luminescence intesity than conventional homogeneously doped nanostructures. At the same time, the activator Ions located in the Shell enable a ~6 times more efficient resonant energy Transfer from UCNPs to surface-bound acceptor dye molecules due to the short distance between donor-acceptor pairs. Our work provides new insights into the rational design of UCNPs and will greatly encrease the General applicability of upconversion nanotechnologies. KW - Fluorescence KW - Lanthanide KW - Upconversion KW - Brightness KW - Quantification KW - Nanoparticle KW - Absolute fluorometry KW - NIR KW - IR KW - Quantum yield KW - Integrating sphere spectroscopy KW - Method KW - Energy transfer KW - Shell KW - Particle architecture PY - 2017 DO - https://doi.org/10.1039/c7nr06900f SN - 2040-3372 SN - 2040-3364 VL - 10 IS - 1 SP - 250 EP - 259 PB - The Royal Society of Chemistry AN - OPUS4-43893 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Resch-Genger, Ute ED - Scholz, Norman ED - Behnke, Thomas T1 - Determination of the critical micelle concentration of neutral and ionic surfactants with fluorometry, conductometry, and surface tension - a method comparison N2 - Micelles are of increasing importance as versatile carriers for hydrophobic substances and nanoprobes for a wide range of pharmaceutical, diagnostic, medical, and therapeutic applications. A key Parameter indicating the Formation and stability of micelles is the critical micelle concentration (CMC). In this respect, we determined the CMC of common anionic, cationic, and non-ionic surfactants fluorometrically using different fluorescent probes and fluorescence Parameters for Signal detection and ompared the results with conductometric and surface Tension measurements. Based upon These results, requirements, Advantages, and pitfalls of each methods are discussed. Our study underlines the versatility of fluorometric methods that do not impose specific requirements on surfactants and are especially suited for the quantification of very low CMC values. Conductivity and surface Tension measurements yield smaller uncertainties particularly for high CMC values, yet are more time- and substance consuming and not suitable for every surfactant. KW - Fluorescence KW - Methods KW - Critical micelle concentration (CMC) KW - Conductometry KW - Fluorescence probe KW - Dye KW - Nile Red KW - Pitfalls KW - Method evaluation KW - Uncertainty PY - 2017 DO - https://doi.org/10.1007/s10895-018-2209-4 SN - 1053-0509 SN - 1573-4994 VL - 28 IS - 1 SP - 465 EP - 476 AN - OPUS4-43905 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wolf, Marcus A1 - Afanasiev, Roman A1 - Böllinghaus, Thomas A1 - Pfennig, A. T1 - Investigation of Corrosion Fatigue of Duplex Steel X2CrNiMoN22-5 3 Exposed to a Geothermal Environment under Different Electrochemical Conditions and Load Types N2 - Corrosion fatigue (CF) of duplex stainless steel (DSS) X2CrNiMoN22-5-3 was investigated in in-situ geothermal conditions of the Northern German Basin (NGB). The influence of the load type on CF behavior of the alloy was examined by applying push/pull and rotating bending cyclic load to failure. The hour-glass shaped specimens with both polished and precisely turned surface finish were tested in corrosion chambers allowing for the permanent circulation of Northern German Basin electrolyte heated to 369 K. Additionally, the influence of a protective cathodic potential on the CF life expectancy was investigated by employing a potentiostat. The rotating bending cyclic load led to a higher CF life expectancy, which decreased with increasing duration of the experiment due to a higher deterioration rate of the material. The application of a cathodic potential caused a significant increase of the CF lifespan from 4.7 x 105 (open-circuit potential (OCP)) to 107 cycles (preset threshold cycle number) for the potential range from USHE = – 450 to – 900 mV. Microstructural analysis of the CF damage revealed horizontal grain attack within corrosion pit cavities, multiple fatigue cracks and preferable deterioration of the austenitic phase. T2 - 13th International Conference on Greenhouse Gas Control Technologies, GHGT-13 CY - Lausanne, Switzerland DA - 14.11.2016 KW - Different load cases KW - Corrosion fatigue KW - DSS KW - Geothermal environment KW - Different electrochemical conditions PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-439231 DO - https://doi.org/10.1016/j.egypro.2017.03.1657 SN - 1876-6102 VL - 114 SP - 5337 EP - 5345 PB - Elsevier Science AN - OPUS4-43923 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Madia, Mauro A1 - Beier, H. Th. T1 - Fatigue strength and life determination of weldments based on fracture mechanics N2 - The paper provides an overview on the results of a German cluster project on the use of fracture mechanics to the determination of the fatigue strength of weldments with fatigue cracks originating at the weld toes. The approach includes (a) a concept for short crack propagation for which the common ΔK concept is not applicable and the crack closure effects are still being gradually build-up, (b) a method for determining fatigue life relevant initial crack sizes as they are needed in any fracture mechanics analysis and (c) multiple cracking and crack coalescence at load levels higher than the endurance limit. The analyses are stochastically performed. Both, the endurance limit and the finite life branch of the S-N curve are determined. Besides a brief introduction into the approach, validation examples are presented. These comprise different weldment types (butt welds, cross joints and longitudinal stiffened plates), two steels (S355NL and S960QL) of quite different strengths, different weld geometries due to different welding techniques (WIG, MAG), as-welded and stress relieved welds and different stress ratios varying from R = -1 to R = 0.5. T2 - FDMD 2017 CY - Lecco, Italy DA - 19.09.2017 KW - Weldments KW - Fatigue strength KW - Fracture mechanics KW - Initial crack size KW - Short crack propagation KW - Multiple crack propagation PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-438500 DO - https://doi.org/10.1016/j.prostr.2017.11.106 SN - 2452-3216 VL - 7 SP - 407 EP - 414 PB - ScienceDirect CY - Lecco, Italy AN - OPUS4-43850 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Engl, T. A1 - Eberl, N. A1 - Gorse, C. A1 - Krüger, T. A1 - Schmidt, T. A1 - Plarre, Rüdiger A1 - Adler, C. A1 - Kaltenpoth, M. T1 - Ancient symbiosis confers desiccation resistance to stored grain pest beetles N2 - Microbial symbionts of insects provide a range of ecological traits to their hosts that are beneficial in the context of biotic interactions. However, little is known about insect symbiont-mediated adaptation to the abiotic environment, for example, temperature and humidity. Here, we report on an ancient clade of intracellular, bacteriome-located Bacteroidetes symbionts that are associated with grain and Wood pest beetles of the phylogenetically distant families Silvanidae and Bostrichidae. In the saw-toothed grain beetle Oryzaephilus surinamensis, we demonstrate that the symbionts affect cuticle thickness, melanization and hydrocarbon profile, enhancing desiccation resistance and thereby strongly improving fitness under dry conditions. Together with earlier observations on Symbiont contributions to cuticle biosynthesis in weevils, our findings indicate that convergent acquisitions of bacterial mutualists represented key adaptations enabling diverse pest beetle groups to survive and proliferate under the low ambient humidity that characterizes dry grain storage facilities. KW - Bacteroidetes KW - Cuticle KW - Desiccation resistance KW - Grain pest beetles KW - Symbiosis PY - 2017 DO - https://doi.org/10.1111/mec.14418 SN - 1365-294X SN - 0962-1083 VL - 27 IS - 8 SP - 2095 EP - 2108 AN - OPUS4-44013 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nolze, Gert A1 - Dietrich, D. A1 - Lampke, T. A1 - Del-Solar-Velarde, N. A1 - Nickel, D. A1 - Chapoulie, R. A1 - Castillo Butters, L.J. T1 - The potential of EBSD and EDS for ceramics investigations - Case studies on sherds of pre-Columbian pottery N2 - The work focuses on the potential of structural and chemical examinations by scanning electron microscopy based methods for archaeometric studies on ceramics. Achieved by a single preparation technique (polished block sections), the feasibility and benefits of electron backscatter diffraction are demonstrated as case studies using polychrome examples of pre-Columbian pottery (Wari, Moche and Cajamarca). Elemental and phase maps allow for separate consideration of clay and temper. Identification of mineral phases and intergrowths of temper particles provide information for clarifying clay procurement and firing techniques with respect to local versus non-local pottery to enlighten trade relations, technological transfer and shared heritage of pre-Columbian cultures. KW - SEM–EDS/EBSD KW - Pre-Columbian ceramics KW - Temper KW - Pseudobrookite KW - Titanite PY - 2017 VL - 60 IS - 3 SP - 489 EP - 501 AN - OPUS4-45096 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chandra, K. A1 - Kranzmann, Axel T1 - High temperature oxidation of 9–12% Cr ferritic/martensitic steels under dual-environment conditions N2 - In normal operations, the opposite surfaces of the power plant components are exposed to two different environments, i.e. air/flue gas on the one side and steam on the other side. Exposure under such dual-environment can lead to accelerated corrosion of the components on the air side. The oxidation behaviour of ferritic/martensitic steel T92 was investigated under dual-environment in a specially designed test equipment. The samples were exposed to dry oxyfuel flue gas (CO2–27%N2–2%O2–1%SO2) on one side and to steam on the other side up to 1000 h at 650°C. The formation of oxide scales was characterised by optical microscopy and scanning electron microscopy with attached energy-dispersive spectroscopy. Oxidation rate of specimens under dual-Environment condition was almost three times higher than that in single-environment condition. This is explained based on hydrogen transport through the bulk alloy from the steam side to the flue gas side. KW - Oxidation KW - Dual-environment KW - Oxyfuel KW - Ferritic/martensitic steel KW - Steam PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-457101 DO - https://doi.org/10.1080/1478422X.2017.1374049 VL - 53 IS - 31 SP - 27 EP - 33 PB - Taylor & Francis AN - OPUS4-45710 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meschut, G. A1 - Janzen, V. A1 - Rethmeier, Michael A1 - Gumenyuk, Andrey A1 - Frei, J. T1 - Charakterisierung des Bruch- und Festigkeits verhaltens von widerstandspunktgeschweißten Aluminiumverbindungen N2 - Die Reduktion des Fahrzeuggewichts ist ein wesentlicher Ansatz zur Ver-ringerung des Energie- und Ressourcenverbrauchs und damit zur Senkung der CO2-Emissionen im Automobilbau. In der Karosserieentwicklung kann der vermehrte Einsatz von Aluminiumwerkstoffen einen bedeutenden Beitrag dazu leisten. Im preissensitiven Umfeld des Karosseriebaus etabliert sich das bei Stahlanwendungen genutzte Widerstandspunktschweißen zunehmend auch für Aluminiumverbindungen. Verfahrensbedingte Herausforderungen, wie verkürzte Elektrodenstandzeiten und mangelnde Kenntnis über den Einfluss von Imperfektionen auf die Festigkeit, begrenzen dennoch die Weiterverbreitung des Verfahrens und stellen die Prozessrobustheit insgesamt in Frage. Im Rahmen des hier vorgestellten Forschungsvorhabens wurden das Auftreten verschiedener Brucharten experimentell untersucht und Prognosefunktionen zur Abschätzung der Tragfähigkeit von Widerstandspunktschweißverbindungen unter verschiedenen Belastungsfällen erstellt. Anschließend wurde der Einfluss von Oberflächenrissen und Rissen in der Schweißlinse auf die Scherzugfestigkeit sowohl experimentell als auch simulativ analysiert. KW - Aluminium KW - Widerstandspressschweißen KW - Rissbildung KW - Festigkeit KW - Werkstofffragen PY - 2017 UR - http://www.schweissenundschneiden.de/article/charakterisierung-des-bruch-und-festigkeitsverhaltens-von-widerstandspunktgeschweissten-aluminiumverbindungen/ VL - 69 IS - 3 SP - 126 EP - 133 PB - DVS Media GmbH AN - OPUS4-39577 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sun, C. A1 - Tian, X. A1 - Wang, L. A1 - Liu, Y. A1 - Wirth, Cynthia A1 - Günster, Jens A1 - Li, D. A1 - Jin, Z. T1 - Effect of particle size gradation on the performance of glass-ceramic 3D printing process N2 - Particle size gradation is regarded as an effective method for overcoming the contradicting requirements in three-dimensional printing (3DP). In present work, particle size gradation was optimized to obtain both acceptable flowability of the powder material and high-strength 3D-printed glass-ceramic products. The effect of gradation on the printing process, sintering process and performance of the 3D-printed glass-ceramic products was investigated comprehensively. The glass-ceramic powders with three size ranges were mixed in certain proportions and applied to print parts. The result showed parts printed with powder mixed by 60 wt% 45–100 µm and 40 wt% 0–25 µm particles had satisfactory density of 1.60 g/cm³ and bending strength of 13.8 MPa. The flowability decreased with an increasing proportion of fine particles. Part density was determined by the powder bulk density in the powder bed as well as the shrinkage during sintering while strength of part was found to be dependent on the sintering degree. KW - Flowability KW - Glass-ceramic KW - Particle size gradation KW - Three-dimensional printing KW - Mechanical properties PY - 2017 DO - https://doi.org/10.1016/j.ceramint.2016.09.197 SN - 0272-8842 VL - 43 IS - 1 SP - 578 EP - 584 PB - Elsevier AN - OPUS4-39783 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Würth, Christian A1 - Kaiser, Martin A1 - Wilhelm, Stefan A1 - Grauel, Bettina A1 - Hirsch, Th. A1 - Resch-Genger, Ute T1 - Excitation power dependent population pathways and absolute quantum yields of upconversion nanoparticles in different solvents N2 - The rational design of brighter upconversion nanoparticles (UCNPs) requires a better understanding of the radiationless deactivation pathways in these materials. Here, we demonstrate the potential of excitation power density (P)-dependent studies of upconversion (UC) luminescence intensities, slope factors, and absolute quantum yields (ΦUC) of popular β-NaYF4:20% Yb3+,2% Er3+ UCNPs of different surface chemistries in organic solvents, D2O, and water as a tool to gain deeper insight into the UC mechanism including population and deactivation pathways particularly of the red emission. Our measurements, covering a P regime of three orders of magnitude, reveal a strong difference of the P-dependence of the ratio of the green and red luminescence bands (Ig/r) in water and organic solvents and P-dependent population pathways of the different emissive energy levels of Er3+. In summary, we provide experimental evidence for three photon processes in UCNPs, particularly for the red emission. Moreover, we demonstrate changes in the excited population dynamics via bi- and triphotonic processes dependent on the environment, surface chemistry, and P, and validate our findings theoretically KW - Upconverion KW - Quantum Yield KW - Photo physics PY - 2017 UR - http://pubs.rsc.org/en/content/articlepdf/2017/nr/c7nr00092h DO - https://doi.org/10.1039/c7nr00092h SN - 2040-3364 SN - 2040-3372 VL - 9 IS - 12 SP - 4283 EP - 4294 PB - The Royal Society of Chemistry AN - OPUS4-39849 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -