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 - TY - JOUR A1 - Weidner, Steffen A1 - Kricheldorf, H. R. T1 - The Role of Transesterification in SnOct 2 - Catalyzed Polymerizations of Lactides N2 - l-lactide or meso-lactide are polymerized either at 120 °C where the polymerization process of l-lactide is accompanied by crystallization, or at 180 °C where poly(l-lactide) remains in the molten state. Polymerizations at 120 °C initially yield even-numbered chains (with respect to lactic acid units) having relatively low dispersity, but the fraction of odd-numbered chains increases with time and the entire molecular weight distribution changes. Traces of cyclics are only formed after 7 d. Polymerizations at 180 °C yield equilibrium of even and odd-numbered chains from the beginning, but at low monomer/initiator ratios and short reaction times (<4 h) cyclics are again not formed. They appear at longer reaction times and entail higher dispersities. The results are discussed in terms of five different transesterification mechanisms. KW - Polylactides KW - MALDI KW - Transesterification KW - Sn catalysts PY - 2017 DO - https://doi.org/10.1002/macp.201600331 SN - 1022-1352 VL - 218 IS - 3 SP - 1600331 PB - Wiley AN - OPUS4-39753 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Steppan, Enrico A1 - Mantzke, Philipp A1 - Steffens, Benjamin A1 - Rhode, Michael A1 - Kannengießer, Thomas T1 - Thermal desorption analysis for hydrogen trapping in microalloyed high-strength steels N2 - Hydrogen can have an extreme degradation effects in steels, particularly concerning the mechanical properties. These effects can lead to hydrogen-assisted cracking in microalloyed high-strength steels during fabrication and/or operation in industrial applications. In order to study these effects, electrochemically charged tensile specimens were tested to elucidate the degradation of their properties. The carrier gas hot extraction (CGHE) method, which functionally combines a mass spectrometer with a thermal desorption analysis (TDA) process, was used for the detection of ultra-low diffusible hydrogen concentrations in the material specimens. The mass spectrometer provided rapid and automatic determination of hydrogen concentration, whereas the TDA presented the activation energy within the respective test specimen at the specific temperature. Additionally, specimen temperature was carefully monitored to reduce the evaluation error for local effusion peaks. A quenching and deformation dilatometer was used for the analysis of typical heat-affected zones during the welding process for a high reproducibility of the homogenous microstructures that were studied. The present work shows the interaction between hydrogen and lattice defects in different microalloyed materials and heat-affected zones of weldable fine-grained steels. These steels were prepared in a quenched and tempered condition and in a thermo-mechanically rolled condition. These preparations were made according to German standard DIN EN 10025-6 and to DIN EN 10149-2, respectively. The trapping characteristics of two steel grades, S690QL and S700MC, were studied with respect to the activation energy dependent on carbon content and microalloying elements such as Ti, Nb, Mo, Cr, and V. The two steel grades exhibited several types of traps: carbide formations, dislocations, and/or grain boundaries were common, which can influence activation energy and hydrogen solubility. The type and dimension of inclusions or particles also affected the hydrogen trapping behavior. A decrease of carbon and specific alloying elements in thermo-mechanically hot rolled steels led to a change in the activation energy binding the trapped hydrogen. This thermo-mechanically hot rolled steel revealed an increased interaction between hydrogen and precipitations. The higher carbon content in the quenched and tempered steel led to a higher interaction between hydrogen and iron carbide, specifically in the martensitic phase. Furthermore, the trapping behavior in heat-affected zones showed a significant increase in activation energy, especially in the coarse-grained microstructure. These previously mentioned various effects were studied to better understand the degradation of mechanical properties in these two steels. KW - Microalloyed steels KW - Hydrogen embrittlement KW - Heating KW - Chemical analysis KW - Microstructure KW - Heat-affected zone PY - 2017 DO - https://doi.org/10.1007/s40194-017-0451-z SN - 0043-2288 SN - 1878-6669 VL - 61 IS - 4 SP - 637 EP - 648 PB - Springer CY - Berlin Heidelberg AN - OPUS4-40190 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Myrach, Philipp A1 - Jonietz, Florian A1 - Meinel, Dietmar A1 - Suwala, Hubert A1 - Ziegler, Mathias T1 - Calibration of thermographic spot weld testing with X-ray computed tomography N2 - The paper presents an attempt for the calibration of an active thermography method that is suitable for the non-destructive evaluation of spot welds. Nowadays, the quality of spot welds is commonly characterised by the application of random chisel tests, which are time consuming, expensive and destructive. Recently a non-destructive testing method by means of active thermography was proposed that relies on the fact that the mechanical connection formed by the spot weld also serves as a thermal bridge between the two steel sheets joined in the welding process. It is shown in this paper that this thermal bridge can be thermographically characterised by extracting a measure for the spot weld diameter and hence the quality of the spot weld. The determination of the absolute value of the diameter hereby relies on a calibration of the testing system, which is performed by means of X-ray computed tomography in this study. The experiments were carried out using different experimental approaches, namely transmission as well as reflection geometry wSetup in reflectionith laser illumination. A comprehensive evaluation of samples produced using different welding currents, hence different quality, was carried out in order to validate the thermographic results. KW - Thermography KW - Spot welds KW - Spot welding KW - Computed thomography KW - Non-destructive testing PY - 2017 DO - https://doi.org/10.1080/17686733.2017.1281554 SN - 1768-6733 SN - 2116-7176 VL - 14 IS - 1 SP - 122 EP - 131 PB - Taylor & Francis CY - London AN - OPUS4-40180 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Klingelhoeffer, Hellmuth A1 - Aegerter, J. A1 - Scherm, T. A1 - Schenuit, E. A1 - Sotheran, S. A1 - Loveday, M. A1 - Bosch, P. A1 - Bloching, H. A1 - Olbricht, Jürgen A1 - McEnteggart, I. T1 - Discussion on "Analysis on the issues in ISO 6892-1 and TENSTAND WP4 report based on the data of confirm tests by 21 laboratories" N2 - The authors, Li et al., of the paper entitled “Analysis on the Issues in ISO 6892-1 and TENSTAND WP4 Report Based on Data to Confirm Tests by 21 Laboratories” (J. Test. Eval. DOI: 10.1520/JTE20150479 (online only)) have expressed views that the authors of this rebuttal believe to be based on fundamental misunderstandings and misinterpretations of the tensile testing standard ISO 6892-1:2009, ISO 6892-1:2016, and its former versions, thus leading to erroneous conclusions. This refutation is intended to clarify the understanding of ISO 6892-1 and to address the misunderstandings and the misinterpretations of the authors of the paper. The present standard ISO 6892-1:2016 has a long history dating back to the 1970s. At that time, the tensile testing procedure was standardized on the National and International scale in parallel. To understand the present standard, the knowledge of the history helps to understand the background of details of the testing procedure implemented today. The history of the tensile testing standard has been discussed extensively during the annual international standardization meeting of ISO committee TC 164 SC1 for the last few years, at which some of the authors of the Li et al. paper attended. The authors continue to disagree with facts that were agreed by the consortium of the European research project TENSTAND and by the present international experts involved in ISO TC 164 SC1. It appears that the principal objective of the authors regarding their present publication was to increase the testing speed during tensile testing. However, the international standardization community has previously declined similar proposals by some of the authors. Many arguments presented by Li et al. were thus refuted. The conclusions of their paper are misleading and the international standardization community for tensile testing refused to revise the present standard, ISO 6892-1 (2016), according the authors’ proposals. KW - Tensile testing procedure KW - ISO 6892-1 KW - TENSTAND WP4 Final Report PY - 2017 DO - https://doi.org/10.1520/JTE20160526 SN - 0090-3973 SN - 1945-7553 VL - 45 IS - 3 SP - 1105 EP - 1114 PB - ASTM International CY - West Conshohocken, PA, USA AN - OPUS4-40267 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shashev, Yury A1 - Kupsch, Andreas A1 - Lange, Axel A1 - Evsevleev, Sergei A1 - Müller, Bernd R. A1 - Osenberg, Markus A1 - Manke, Ingo A1 - Hentschel, Manfred P. A1 - Bruno, Giovanni T1 - Optimizing the visibility of X-ray phase grating interferometry N2 - The performance of grating interferometers coming up now for Imaging interfaces within materials depends on the efficiency (visibility) of their main component, namely the phase grating. Therefore, experiments with monochromatic synchrotron radiation and corresponding simulations are carried out. The visibility of a Phase grating is optimized by different photon energies, varying detector to grating distances and continuous rotation of the phase grating about the grid lines. Such kind of rotation changes the projected grating shapes, and thereby the distribution profiles of phase shifts. This yields higher visibilities than derived from ideal rectangular shapes. By continuous grating rotation and variation of the propagation distance, we achieve 2D visibility maps. Such maps provide the visibility for a certain combination of grating orientation and detector position. Optimum visibilities occur at considerably smaller distances than in the standard setup. KW - Synchrotron, BAMline KW - Talbot-Lau interferometer KW - X-ray imaging KW - X-ray refraction KW - Grating interferometry KW - X-ray phase contrast PY - 2017 DO - https://doi.org/10.3139/120.111097 SN - 0025-5300 VL - 59 IS - 11-12 SP - 974 EP - 980 PB - Hanser Verlag AN - OPUS4-42955 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lehmann, Jens A1 - Leonhard, H. T1 - Korrosionsschutz bekennt Farbe - Schnelltest auf Korrosionsgefahr bei nicht rostenden Stählen N2 - In Chemieanlagen ist die Passivschicht von Rohrsystemen und Behältern aus nichtrostendem Stahl nicht nur durch den rauen Produktionsalltag gefährdet. Auch im Neuzustand können Schäden entstehen, bspw. durch Schleifvorgänge oder eine unvollständige Entfernung von Anlauffarben nach dem Schweißen. TÜV SÜD Chemie Service beteiligte sich an der Prüfung eines von der Bundesanstalt für Materialforschung und -prüfung (BAM) entwickelten Korrosionsschnelltests. KorroPads liefern in nur 15 Minuten eine valide Aussage zum Zustand der Passivschicht auf den Werkstoffoberflächen. KW - Nichtrostender Stahl KW - Korrosionsschnelltest KW - KorroPad KW - Passivschicht PY - 2017 SN - 0340-9961 VL - 46 IS - 11 SP - 46 EP - 48 PB - Hüthig GmbH CY - Heidelberg AN - OPUS4-43120 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heitz, J. A1 - Plamadeala, C. A1 - Muck, M. A1 - Habidzadeh, H. A1 - Baumgartner, W. A1 - Weth, A. A1 - Steinwender, C. A1 - Blessberger, H. A1 - Kellermair, J. A1 - Kirner, Sabrina V. A1 - Krüger, Jörg A1 - Bonse, Jörn A1 - Guntner, A. S. A1 - Hassel, A. W. T1 - Laser-induced microstructures on Ti substrates for reduced cell adhesion N2 - The abstract summarizes the poster presented at the "Kardiologie im Zentrum - Fortbildung der Klinik für Kardiologie und Intensivmedizin Kepler Universitätsklinikum Linz", held between October 20th and 31st in Linz, Austria. The poster has been awarded the 2nd place of the "Best Poster Award". T2 - Kardiologie im Zentrum - Fortbildung der Klinik für Kardiologie und Intensivmedizin Kepler Universitätsklinikum Linz CY - Linz, Austria DA - 20.10.2017 KW - Femtosecond laser processing KW - Titanium alloy KW - Cell adhesion KW - Pacemaker PY - 2017 UR - http://www.kup.at/kup/pdf/14098.pdf SN - 1024-0098 VL - 24 IS - 11-12 SP - 292 EP - 292 PB - Krause & Pachernegg GmbH CY - Gablitz, Austria AN - OPUS4-43160 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Resch-Genger, Ute A1 - Pilch, A. A1 - Würth, Christian A1 - Kaiser, Martin A1 - Wawrzynczyk, D. A1 - Kurnatowska, M. A1 - Arabasz, S. A1 - Prorok, K. A1 - Samoc, M. A1 - Strek, W. A1 - Bednarkiewicz, A. T1 - Shaping luminescent properties of Yb3+ and Ho3+ co-doped upconverting core-shell ß-NaYF4 nanoparticles by dopant distribution and spacing N2 - At the core of luminescence color and lifetime Tuning of rare earth doped upconverting nanoparticles (UCNPs), is the understanding of the Impact of the particle architecture for commonly used sensitizer (S) and activator (A) Ions. In this respect, a series of core@Shell NaYF4 UCNPs doped with Yb3+ and Ho3+ ions are presented here, where the same dopant concentrations are distributed in different particle architectures following the scheme: YbHo core and YbHo@..., ...@YbHo, Yb@Ho, Ho@Yb, YbHo@Yb, and Yb@YbHo core-Shell NPs. As refealed by quantitative steady-state and time-resolved luminescence studies, the relative spatial Distribution of the A and S ions in the UCNPs and their protection from surface quenching has a critical Impact on ther luminescence characteristics. Although the increased amount of Yb3+ Ions boosts UCNP Performance by amplifying the Absorption, the Yb3+ ions can also efficiently dissipate the energy stored in the material through energy Migration to the surface, thereby reducing the Overall energy Transfer Efficiency to the activator ions. The results provide yet another proof that UC Phosphor chemistry combined with materials Engineering through intentional core@shell structures may help to fine-tune the luminescence Features of UCNPs for their specific future applications in biosensing, bioimaging, photovoltaics, and Display technologies. KW - Fluorescence KW - Upconversion KW - NIR KW - Nonlinear KW - Nanoparticle KW - Surface chemistry KW - Quantum yield KW - Liftetime KW - Nanocrystal KW - Lanthanide KW - Ho(III) KW - Yb(III) KW - Mechanism KW - Absolute flourescence KW - Excitation power density dependence PY - 2017 DO - https://doi.org/10.1002/smll.201701635 SN - 1613-6810 VL - 13 IS - 47 SP - 1701635, 1 EP - 13 PB - WILEY-VCH Verlag GmbH & co. KGaA CY - Weinheim AN - OPUS4-43629 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bakir, Nasim A1 - Gumenyuk, Andrey A1 - Rethmeier, Michael T1 - Investigation of solidification cracking susceptibility during laser beam welding using an in-situ observation technique N2 - Using the novel optical measurement technique together with the optical flow algorithm, a twodimensional deformation analysis during welding has been conducted. This technique provides for the first time a measurement of the strain field locally in the immediate vicinity of the assumed solidification front. The described procedure of the opticalmeasurement allows to determine the real martial-dependent values of critical strain and strain rate characterising transition to the hot cracking during laser welding processes. The local critical strain that obtained in the assumed solidification showed that the local critical strain decreases as the strain rate increases. Moreover, this phenomenon has also been shown with results from the CTW-test, since the global strain decreases with an increase in the external strain rate. KW - Novel optical measurement KW - Local critical strain KW - Solidification cracking KW - Laser beam Welding PY - 2017 DO - https://doi.org/10.1080/13621718.2017.1367550 SN - 1362-1718 SP - 1 EP - 7 PB - Taylor & Francis AN - OPUS4-42918 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Theiler, Geraldine A1 - Gradt, Thomas T1 - Gleitverhalten von PEEK-Kompositwerkstoffen in Wasserstoffumgebung N2 - Die Reibeigenschaften von PEEK Materialien gegen Stahlscheiben wurden in Luft, Vakuum und Wasserstoffumgebung untersucht. KW - PEEK-Komposite KW - Wasserstoff KW - Vakuum KW - Graphit PY - 2017 SN - 0724-3472 VL - 64 IS - 6 SP - 52 EP - 59 AN - OPUS4-42919 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marko, A. A1 - Graf, B. A1 - Rethmeier, Michael T1 - Statistical analysis of weld bead geometry in Ti6Al4V laser cladding N2 - The process of laser cladding has become more important during recent years because of its broad application for cladding, repair or additive manufacturing. In the field of mechanical engineering, one use is the repair of turbine blades. For high quality and reliability of the repaired components, it is necessary to adjust the weld bead geometry to the specific repair task. The bead geometry influences the metallurgical bonding and the degree of dilution as well as the formation of defects like pores or cracks. Therefore, it is important to know the effects of the different parameters on the welding bead. A valuable tool to meet this industrial challenge is the design of experiments (DoE). In this context, the user can choose between a huge number of test plans. Greater Profit of information is expected by a larger test range. In order to confirm the acceptance, a five-step full factorial test plan is compared to a central composite design in this paper. Moreover, the limits of the experimental range are indicated and restrictions can be derived. As the results show, the essential effects are detected with a full factorial test plan as well as with a central composite design. Merely the effect strength could not always be specified unambiguously. On this account and in consideration of cost efficiency, the use of central compound design is recommended in industrial applications. KW - Laser metal deposition KW - Design of experiments KW - Laser cladding KW - Cladding parameter KW - Additive manufacturing PY - 2017 DO - https://doi.org/10.3139/120.111077 SN - 0025-5300 SN - 2195-8572 VL - 59 IS - 10 SP - 837 EP - 843 PB - Carl Hanser Verlag CY - München AN - OPUS4-42882 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jensen, S. A. A1 - Rosu, Dana Maria A1 - Hertwig, Andreas A1 - Hansen, P.-E. T1 - Use of Rayleigh-Rice Theory for Analysis of Ellipsometry Data on Rough CIGS Films N2 - Ellipsometry is a useful tool for studying the optical properties of thin films such as photovoltaic devices. We employ Müller matrix ellipsometry to study the thin film photovoltaic material copper indium gallium selenide Cu(In,Ga) Se2 (CIGS), a commercially relevant material with high energy conversion efficiency. Confocal microscopy reveals an rms roughness of 68 nm, which greatly affects the ellipsometry data. Rayleigh-Rice theory is employed to account for the optical properties of the surface roughness in the ellipsometry experiment, and a library search method is used to compare Müller parameters calculated for various CIGS compositions, to the measured data. The Müller parameters calculated with the Rayleigh-Rice model are found to correspond well with the measured data, and a surface roughness of 37nm and a correlation length of 125nm are extracted. KW - Photovoltaics KW - Thin Films KW - Ellipsometry KW - Scattering Theory KW - Optical Wavefield KW - Simulation KW - Müller Polarimetry KW - Multidimensional Spectroscopy PY - 2017 DO - https://doi.org/10.1002/pssc.201700217 SN - 1862-6351 VL - 14 IS - 12 SP - 1700217, 1 EP - 5 PB - WILEY-VCH Verlag GmbH & Co. KGaA CY - Weinheim AN - OPUS4-43390 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, Hans R. A1 - Weidner, Steffen A1 - Scheliga, Felix T1 - Cyclic poly(l-lactide) via ring-expansion polymerization by means of dibutyltin 4-tert-butylcatecholate N2 - Five new catalysts are prepared from dibutyltin oxide and catechol (HCa), 2,3-dihydroxynaphthalene (NaCa), 4-tert-butyl catechol (BuCa), 4-cyano catechol (CyCa), and 4-benzoyl catechol (BzCa), but only BuCa gives useful results. When benzyl alcohol is used as an initiator, linear chains having benzyl ester end groups are formed in a slow polymerization process. In contrast to cyclic or noncyclic dibutyltin bisalkoxides, neat BuCa yields cyclic poly(l-lactide)s via a fast ring-expansion polymerization. Under certain conditions, a high-melting crystalline phase (Tm = 191 °C) is obtained. At 160 °C and short reaction times even-numbered cycles are slightly prevailing, but, surprisingly, at 120 °C, odd-numbered cycles are predominantly formed. These results definitely prove that a ring-expansion mechanism is operating. KW - Lactides KW - MALDI TOF MS KW - Morphology KW - Ring-opening polymerization KW - Tin catalysts PY - 2017 DO - https://doi.org/10.1002/macp.201700274 SN - 1521-3935 SN - 1022-1352 VL - 218 IS - 22 SP - 1700274, 1 EP - 1700274, 10 PB - Wiley VCH CY - Weinheim AN - OPUS4-43583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Seidel, R. A1 - Kraffert, K. A1 - Kabelitz, Anke A1 - Pohl, M.N. A1 - Kraehnert, R. A1 - Emmerling, Franziska A1 - Winter, B. T1 - Detection of the electronic structure of iron-(III)-oxo oligomers forming in aqueous solutions N2 - The nature of the small iron-oxo oligomers in iron-(III) aqueous solutions has a determining effect on the chemical processes that govern the formation of nanoparticles in aqueous phase. Here we report on a liquid-Jet photoelectron-spectroscopy experiment for the investigation of the electronic structure of the occurring iron-oxo oligomers in FeCl3 aqueous solutions. The only iron species in the as-prepared 0.75 M solution are Fe3+ monomers. Addition of NaOH initiates Fe3+ hydrolysis which is followed by the formation of iron-oxo oligomers. At small enough NaOH concentrations, corresponding to approximately [OH]/[Fe] = 0.2–0.25 ratio, the iron oligomers can be stabilized for several hours without engaging in further aggregation. Here, we apply a combination of non-resonant as well as iron 2p and Oxygen 1s resonant photoelectron spectroscopy from a liquid microjet to detect the electronic structure of the occurring species. Specifically, the oxygen 1s partial electron yield X-ray absorption (PEY-XA) spectra are found to exhibit a peak well below the onset of liquid water and OH (aq) absorption. The iron 2p absorption gives rise to signal centered between the main absorption bands typical for aqueous Fe3+. Absorption bands in both PEY-XA spectra are found to correlate with an enhanced photoelectron Peak near 20 eV binding energy, which demonstrates the sensitivity of resonant photoelectron (RPE) spectroscopy to mixing between iron and ligand orbitals. These various signals from the iron-oxo oligomers exhibit Maximum intensity at [OH]/[Fe] = 0.25 ratio. For the same ratio, we observe changes in the pH as well as in complementary Raman spectra, which can be assigned to the Transition from monomeric to oligomeric species. At approximately [OH]/[Fe] = 0.3 we begin to observe particles larger than 1 nm in radius, detected by small-angle X-ray scattering. KW - Iron-oxo oligomers KW - XPS KW - Electronic structure PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-433468 DO - https://doi.org/10.1039/c7cp06945f SN - 1463-9076 SN - 1463-9084 VL - 19 IS - 48 SP - 32226 EP - 32234 AN - OPUS4-43346 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Szczerba, Wojciech A1 - Schneider, M. A1 - Żukrowski, J. A1 - de Oliveira Guilherme Buzanich, Ana A1 - Riesemeier, Heinrich A1 - Sikora, M. A1 - Mandel, K. T1 - Spectroscopic Study of the Role of Metal Ions in the Adsorption Process of Phosphate in Nanoscaled Adsorbers Based on Metal (Zn/ Fe/Zr) Oxyhydroxides N2 - Currently great effort is made to find materials and technologies for the recycling of phosphate from wastewater. Herein, we present an in-depth study of the Phosphate adsorption mechanism of a promising adsorber material, a Zn−Fe−Zr oxyhydroxide-based nanostructured precipitate. The behavior of the multicomponent nanomaterial, consisting of both crystalline and amorphous parts, is investigated via X-ray absorption fine structure spectroscopy and Mössbauer spectroscopy, revealing the importance of the nanostructured composition for the phosphate adsorption. We found evidence that adsorption takes place especially in the vicinity of iron sites in the amorphous part of the material. KW - Zn-Fe-Zr nanoparticles KW - Adsorption of phosphate KW - XAFS KW - Catalysis PY - 2017 DO - https://doi.org/10.1021/acs.jpcc.7b04773 SN - 1932-7447 VL - 121 IS - 45 SP - 25033 EP - 25042 PB - ACS Publications AN - OPUS4-43348 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Martynenko, Irina A1 - Litvin, A.P. A1 - Purcell-Milton, F. A1 - Baranov, A. V. A1 - Fedorov, A.V. A1 - Gun´ko, Y.K. T1 - Application of semiconductor quantum dots in bioimaging and biosensing N2 - In this review we present new concepts and recent progress in the application of semiconductur quantum dots (QD) as labels in two important areas of biology, bioimaging and biosensing. We analyze the biologically relevant properties of QDs focusing on the following topics: QD surface treatment and stability labeling of cellular structures and receptors with QDs, incorporation of QDs in living cells, cytotoxicity of QDs and influence of the biolocical environment on the biological and optical properties of QDs. Initially, we consider utilization of QDs as agants in high-resolution bioimaging techniques that can provide information at the molecular levels. The deverse range of modern live-cell QD-based imaging techniques with resolution far beyond the diffraction limit of light is examined. In each technique, we discuss the pros and cons of QD use and deliberate how QDs can be further engineered to facilitate their application in the respective imaging techniques and to produce significant improvements in resolution. Then we review QD-based point-of-care bioassays, bioprobes, and biosensors designed in different formats ranging from analytic biochemistry assays and ELISA, to novel point-of-care smartphone integrated QD-based biotests. Here, a wide range of QD-based fluorescence bioassays with optical transduction, electrochemiluminescence and photoelectrochemical assays are discussedc. Finally, this review provides an analysis of the prospects of application of QDs in selected important Areas of biology. KW - Fluorescence KW - Semiconductor quantum dot KW - Imaging KW - Quantification KW - Nanoparticle KW - NIR KW - IR KW - Quantum yield KW - Method KW - Microscopy KW - Assay KW - Bioconjugate PY - 2017 DO - https://doi.org/10.1039/c7tb01425b VL - 5 IS - 33 SP - 6701 EP - 6727 PB - Royal Society of Chemistry AN - OPUS4-43027 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lehmann, Jens A1 - Leonhard, H. T1 - Sichere Werkstoffauswahl - Korrosionsschnelltest für nichtrostende Stähle N2 - Anlagenkomponenten aus nichtrostendem Stahl sind durch eine Passivschicht auf der Oberfläche vor Korrosion geschützt. Ist diese unvollständig ausgebildet oder beschädigt, geht der Schutz verloren. Hohe Investitionen für Reparaturen und Instandhaltung können die Folge sein. TÜV Süd Chemie Service beteiligte sich an der Prüfung eines von der Bundesanstalt für Materialforschung und -prüfung (BAM) entwickelten Verfahrens zur Charakterisierung der Korrosionsbeständigkeit der Passivschicht. Der KorroPad-Schnelltest liefert in nur 15 Minuten ein valides Prüfergebnis. KW - Nichtrostender Stahl KW - Korrosionsschnelltest KW - KorroPad KW - Passivschicht PY - 2017 SN - 0720-5953 VL - 69 IS - 11-12 SP - IW10 EP - IW11 PB - Springer-VDI-Verlag GmbH & Co. KG CY - Düsseldorf AN - OPUS4-43228 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -