TY - JOUR A1 - Ghasem Zadeh Khorasani, Media A1 - Silbernagl, Dorothee A1 - Platz, D. A1 - Sturm, Heinz T1 - Insights into Nano-Scale Physical and Mechanical Properties of Epoxy/Boehmite Nanocomposite Using Different AFM Modes N2 - Understanding the interaction between nanoparticles and the matrix and the properties of interphase is crucial to predict the macroscopic properties of a nanocomposite system. Here, we investigate the interaction between boehmite nanoparticles (BNPs) and epoxy using different atomic force microscopy (AFM) approaches. We demonstrate benefits of using multifrequency intermodulation AFM (ImAFM) to obtain information about conservative, dissipative and van der Waals tip-surface forces and probing local properties of nanoparticles, matrix and the interphase. We utilize scanning kelvin probe microscopy (SKPM) to probe surface potential as a tool to visualize material contrast with a physical parameter, which is independent from the mechanics of the surface. Combining the information from ImAFM stiffness and SKPM surface potential results in a precise characterization of interfacial region, demonstrating that the interphase is softer than epoxy and boehmite nanoparticles. Further, we investigated the effect of boehmite nanoparticles on the bulk properties of epoxy matrix. ImAFM stiffness maps revealed the significant stiffening effect of boehmite nanoparticles on anhydride-cured epoxy matrix. The energy Dissipation of epoxy Matrix locally measured by ImAFM shows a considerable increase compared to that of neat epoxy. These measurements suggest a substantial alteration of epoxy structure induced by the presence of boehmite. KW - Nanomechanics KW - Intermodulation-AFM KW - Interphase KW - Boehmite KW - Epoxy PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-476040 DO - https://doi.org/10.3390/polym11020235 SN - 2073-4360 VL - 11 IS - 2 SP - 235, 1 EP - 19 PB - MDPI AN - OPUS4-47604 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Falk, Florian A1 - Menneken, M. A1 - Stephan-Scherb, Christiane T1 - Real-time observation of high- temperature gas corrosion in dry and wet SO2-containing atmosphere N2 - Sulfur and water have a fundamental impact on the corrosion rate and potential failure of materials. It is therefore necessary to understand the mechanisms, rates, and potential means of transport, as well as the reactions of these elements with an alloy. This paper investigates the effect of water vapor in the initial stages of SO2 corrosion of an Fe-9Cr-0.5Mn model alloy at 650°C in situ under laboratory conditions using energy-dispersive x-ray diffraction analysis. Two separate experiments were run, one with a 99.5% Ar + 0.5% SO2 atmosphere and one with a 69.5% Ar + 0.5% SO2 + 30% H2O atmosphere. With a wet atmosphere, the alloy formed a scale with decreasing oxygen content towards the scale–alloy interface. Sulfides were identified above and below a (Fe, Cr)3O4 layer in the inner corrosion zone. In contrast to this, the overall scale growth was slower in a dry SO2 atmosphere. KW - Early oxidation KW - Early sulfidation KW - Ferritic steels PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-472844 UR - https://link.springer.com/article/10.1007/s11837-019-03335-9#enumeration DO - https://doi.org/10.1007/s11837-019-03335-9 SN - 1047-4838 SN - 1543-1851 VL - 71 SP - 1 EP - 6 PB - Springer CY - New York AN - OPUS4-47284 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - An, Biwen Annie A1 - Shen, Y. A1 - Voordouw, J. A1 - Voordouw, G. T1 - Halophilic methylotrophic methanogens may contribute to the high ammonium concentrations found in shale oil and shale gas reservoirs N2 - Flow-back and produced waters from shale gas and shale oil fields contain high ammonium, which can be formed by methanogenic degradation of methylamines into methane and ammonium. Methylamines are added to fracturing fluid to prevent clay swelling or can originate from metabolism of the osmolyte triglycinebetaine (GB). We analyzed field samples from a shale gas reservoir in the Duvernay Formation and from a shale oil reservoir in the Bakken formation in Canada to determine the origin of high ammonium. Fresh waters used to make fracturing fluid, early flow-back waters, and late flow back waters from the shale gas reservoir had increasing salinity of 0.01, 0.58, and 2.66 Meq of NaCl, respectively. Microbial community analyses reflected this fresh water to saline transition with halophilic taxa including Halomonas, Halanaerobium, and Methanohalophilus being increasingly present. Early and late flow-back waters had high ammonium concentrations of 32 and 15 mM, respectively. Such high concentrations had also been found in the Bakken produced waters. Enrichment cultures of Bakken produced waters in medium containing mono, di-, or trimethylamine, or triglycinebetaine (GB) converted these substrates into ammonium (up to 20 mM) and methane. The methylotrophic methanogen Methanohalophilus, which uses methylamines for its energy metabolism and uses GB as an osmolyte, was a dominant community member in these enrichments. Halanaerobium was also a dominant community member that metabolizes GB into trimethylamine, which is then metabolized further by Methanohalophilus. However, the micromolar concentrations of GB measured in shale reservoirs make them an unlikely source for the 1,000-fold higher ammonium concentrations in flow-back waters. This ammonium either originates directly from the reservoir or is formed from methylamines, which originate from the reservoir, or are added during the hydraulic fracturing process. These methylamines are then converted into ammonium and methane by halophilic methylotrophic methanogens, such as Methanohalophilus, present in flow-back waters. KW - Methanogen KW - Oil and gas industry KW - Shale KW - Halophile KW - Corrosion PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-474982 DO - https://doi.org/10.3389/fenrg.2019.00023 SN - 2296-598X VL - 7 SP - 1 EP - 13 PB - Frontiers Media CY - Lausanne AN - OPUS4-47498 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liehr, Sascha A1 - Jäger, L. A. A1 - Karapanagiotis, Christos A1 - Münzenberger, Sven A1 - Kowarik, Stefan T1 - Real-time dynamic strain sensing in optical fibers using artificial neural networks N2 - We propose to use artificial neural networks (ANNs) for raw measurement data interpolation and signal shift computation and to demonstrate advantages for wavelength-scanning coherent optical time domain reflectometry (WS-COTDR) and dynamic strain distribution measurement along optical fibers. The ANNs are trained with synthetic data to predict signal shifts from wavelength scans. Domain adaptation to measurement data is achieved, and standard correlation algorithms are outperformed. First and foremost, the ANN reduces the data analysis time by more than two orders of magnitude, making it possible for the first time to predict strain in real-time applications using the WS-COTDR approach. Further, strain noise and linearity of the sensor response are improved, resulting in more accurate measurements. ANNs also perform better for low signal-to-noise measurement data, for a reduced length of correlation input (i.e., extended distance range), and for coarser sampling settings (i.e., extended strain scanning range). The general applicability is demonstrated for distributed measurement of ground movement along a dark fiber in a telecom cable. The presented ANN-based techniques can be employed to improve the performance of a wide range of correlation or interpolation problems in fiber sensing data analysis and beyond. KW - Distributed vibration sensing KW - Distributed acoustic sensing KW - Coherent optical time domain reflectometry KW - Optical fiber sensor KW - Artificial neural network KW - Real time measurement KW - Distributed strain sensing PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-474832 UR - https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-5-7405 DO - https://doi.org/10.1364/OE.27.007405 SN - 1094-4087 VL - 27 IS - 5 SP - 7405 EP - 7425 PB - Optical Society of America AN - OPUS4-47483 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Palkowski, Carsten A1 - Zottl, A. A1 - Malenkovic, I. A1 - Simo, Anne T1 - Fixing efficiency values by unfixing compressor speed: Dynamic test method for heat pumps N2 - The growing market penetration of heat pumps indicates the need for a performance test method that better reflects the dynamic behavior of heat pumps. In this contribution, we developed and implemented a dynamic test method for the evaluation of the seasonal performance of heat pumps by means of laboratory testing. Current standards force the heat pump control inactive by fixing the compressor speed. In contrast, during dynamic testing, the compressor runs unfixed while the heat pump is subjected to a temperature profile. The profile consists of the different outdoor temperatures of a typical heating season based on the average European climate and also includes temperature changes to reflect the dynamic behavior of the heat pump. The seasonal performance can be directly obtained from the measured heating energy and electricity consumption making subsequent data interpolation and recalculation with correction factors obsolete. The method delivers results with high precision and high reproducibility and could be an appropriate method for a fair rating of heat pumps. KW - Heat pump KW - Dynamic test method KW - Seasonal performance factor KW - Variable frequency drive KW - Energy label PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-476944 DO - https://doi.org/10.3390/en12061045 SN - 1996-1073 VL - 12 IS - 6 SP - 1045, 1 EP - 16 PB - MDPI CY - Basel, Switzerland AN - OPUS4-47694 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Palkowski, Carsten A1 - Schwarzenberg, S. A1 - Simo, Anne T1 - Seasonal cooling performance of air conditioners: The importance of independent test procedures used for MEPS and labels N2 - Minimum energy performance standards and labels are commonly used tools to reduce the household energy use thus mitigating greenhouse gas emissions. However, the technical foundation for minimum energy performance standards and labels are test procedures for rating and testing of appliances. To de- termine the seasonal cooling performance of air conditioners, the current test standards require fixing of the compressor speed of the units to achieve steady-state conditions; this way of operation, how- ever, differs from real-life use. To make the seasonal cooling performance testing better reflect the real use conditions, this study proposes a compensation method which can be conducted independently from manufacturer data and still allows modulation of the tested units. Our results show that the tested units behave differently under part-load conditions, which results in a lower energy efficiency rating for some of the tested devices. KW - Air conditioner KW - Independent test method KW - Real use behavior KW - Seasonal energy efficiency ratio KW - Minimum energy performance standards KW - Energy label PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-485813 DO - https://doi.org/10.1016/j.ijrefrig.2019.05.021 SN - 0140-7007 VL - 104 SP - 417 EP - 425 PB - Elsevier AN - OPUS4-48581 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Knieschewski, Arno A1 - Stamminger, R. A1 - Simo, Anne T1 - Cost analysis of screening methods to find non-compliant models using the example of tumble dryers N2 - The European energy label was established to reduce energy consumption in Europe. All classes and values on the energy label are stated by the supplier. The task of market surveillance is to ensure correct labels and to validate their values through compliance tests. However, this can only be done for a small fraction of all models on the market, since physical tests are expensive. Screening methods can be used to narrow down the number of critical products before compliance tests are done to decrease the costs of finding non-compliant models. This study shows a mathematical approach to analyze the cost benefits of screening methods to find non-compliant models. Furthermore, the analysis presented has been applied to 18 screening methods for tumble dryers. The performance test for tumble dryers consists of seven test runs. All screening methods evaluated are composed of a reduced number of test runs. The most efficient screening method reduces the surveillance costs by 40 %. KW - Screening method KW - Market surveillance KW - Tumble dryer KW - Energy label PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-486762 DO - https://doi.org/10.1007/s12053-019-09805-y SN - 1570-646X SN - 1570-6478 VL - 12 IS - 7 SP - 1707 EP - 1715 PB - Springer CY - Dordrecht AN - OPUS4-48676 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Haustein, T. A1 - Busweiler, Sabine A1 - Haustein, V. A1 - von Laar, C. A1 - Plarre, Rüdiger T1 - Laboratory breeding of Korynetes caeruleus (Coleoptera: Cleridae) for the biological of Anobium punctatum) (Coleoptera, Ptinidae) N2 - Larvae and adults of Korynetes caeruleus (de Geer 1775) (Coleoptera: Cleridae) were collected from old churches and reared in the laboratory on Anobium punctatum (de Geer 1774) (Coleoptera: Ptinidae). Breeding success of K. caeruleus was low, but basic parameters of this species’ developmental cycle were identifi ed. At 21°C and 75% relative humidity and a fourmonth cold period at 4°C, the development of K. caeruleus from egg to adult appearance lasted 2 years. The pupal stage may be reached and completed after one and a half years. Feeding on larvae of A. punctatum by larvae of K. caeruleus was observed and consisted of a combination of sucking haemolymph and consuming body parts. The sickle-like mandibles of larvae of K. caeruleus penetrate the cuticle of prey larvae; this is followed by pumping and sucking body movements. Adult beetles of A. punctatum were not attacked by K. caeruleus larvae. Feeding behaviour of adult K. caeruleus was not investigated. KW - Cultural heritage KW - Coleoptera KW - Korynetes caeruleus KW - Cleridae KW - Ptinidae KW - Anobium punctatum KW - Biological pest control KW - Life history data KW - Laboratory breeding KW - Wood protection PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-494999 DO - https://doi.org/10.14411/eje.2019.038 SN - 1802-8829 VL - 116 SP - 362 EP - 371 PB - České Budějovice AN - OPUS4-49499 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kindrachuk, Vitaliy A1 - Fedelich, Bernard A1 - Rehmer, Birgit A1 - Peter, Frauke T1 - Computational methods for lifetime prediction of metallic components under high-temperature fatigue N2 - The issue of service life prediction of hot metallic components subjected to cyclic loadings is addressed. Two classes of lifetime models are considered, namely, the incremental lifetime rules and the parametric models governed by the fracture mechanics concept. Examples of application to an austenitic cast iron are presented. In addition, computational techniques to accelerate the time integration of the incremental models throughout the fatigue loading history are discussed. They efficiently solve problems where a stabilized response of a component is not observed, for example due to the plastic strain which is no longer completely reversed and accumulates throughout the fatigue history. The performance of such an accelerated Integration technique is demonstrated for a finite element simulation of a viscoplastic solid under repeating loading–unloading cycles. KW - Fatigue KW - Incremental lifetime models KW - Finite element analysis PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-481215 UR - https://www.mdpi.com/2075-4701/9/4/390 DO - https://doi.org/10.3390/met9040390 SN - 2075-4701 VL - 9 IS - 4 SP - 390, 1 EP - 24 PB - mdpi CY - Basel, Switzerland AN - OPUS4-48121 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wegner, Karl David A1 - Dussert, F. A1 - Truffier-Boutry, D. A1 - Benayad, A. A1 - Beal, D. A1 - Mattera, L. A1 - Ling, W. L. A1 - Carrière, M. A1 - Reiss, P. T1 - Influence of the Core/Shell Structure of Indium Phosphide Based Quantum Dots on Their Photostability and Cytotoxicity N2 - With the goal to improve their photostability, InP-based QDs are passivated with three types of inorganic shells, namely (i) a gradient ZnSexS1−x shell, (ii) an additional ZnS shell on top of the gradient shell with two different thicknesses (core/shell/shell, CSS), (iii) an alumina coating on top of ZnS. All three systems have photoluminescence Quantum yields (PLQY) > 50%and similar PL decay times (64–67 ns). To assess their photostability they are incorporated into a transparent poly (methyl methacrylate) (PMMA) matrix and exposed to continuous irradiation with simulated sunlight in a climate chamber. The alumina coated core/shell system exhibits the highest stability in terms of PLQY Retention as well as the lowest shift of the PL maximum and lowest increase of the PL linewidth, followed by the CSS QDs and finally the gradient shell system. By means of XPS studies we identify the degradation of the ZnS outer layer and concomitant xidation of the emissive InZnP core as the main origins of degradation in the gradient structure. These modifications do not occur in the case of the alumina-capped sample, which exhibits excellent chemical stability. The gradient shell and CSS systems could be transferred to the aqueous phase using surface ligand exchange with penicillamine. Cytotoxicity studies on human primary keratinocytes revealed that exposure for 24 h to 6.25–100 nM of QDs did not affect cell viability. However, a trend toward reduced cell proliferation is observed for higher concentrations of gradient shell and CSS QDs with a thin ZnS shell, while CSS QDs with a thicker ZnS shell do not exhibit any impact. KW - Indium phosphide KW - Quantum dots KW - Cytotoxicity KW - Photostability PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-494249 DO - https://doi.org/10.3389/fchem.2019.00466 VL - 7 SP - Article Number: 466 PB - Frontiers Media SA AN - OPUS4-49424 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Otto, Peter A1 - de Lorenzis, L. A1 - Unger, Jörg F. T1 - Explicit dynamics in impact simulation using a NURBS contact interface N2 - In this paper, the impact problem and the subsequent wave Propagation are considered. For the contact discretization an intermediate non-uniform rational B-spline (NURBS) layer is added between the contacting finite element bodies, which allows a smooth contact formulation and efficient element-based integration. The impact event is ill-posed and requires a regularization to avoid propagating stress oscillations. A nonlinear mesh-dependent penalty regularization is used, where the stiffness of the penalty regularization increases upon mesh refinement. Explicit time integration methods are well suited for wave propagation problems, but are efficient only for diagonal mass matrices. Using a spectral element discretization in combination with a NURBS contact layer the bulk part of the mass matrix is diagonal. KW - Explicit dynamics KW - Impact simulation KW - Isogeometric analysis KW - mortar method KW - spectral elements PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506041 DO - https://doi.org/10.1002/nme.6264 VL - 121 IS - 6 SP - 1248 EP - 1267 PB - Wiley Online Libary AN - OPUS4-50604 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zinke, R. A1 - Virothi, N. A1 - Köhler, F. A1 - Klippel, A. A1 - Schalau, Sebastian A1 - Krause, U. T1 - Experimental measurement of initial evaporation mass flows from gasoline spills and comparison with empirical models N2 - In this paper, we investigate the evaporation mass flow originating from spills of gas-oline. Large spills of gasoline may form during partial or complete roof sinkings or inthe case of perforations at various deck fittings at external floating roof tanks usedfor the storage. Additionally, spills may form in the retention area in the case of leak-ages at pipes or at the hull. The aim is to predict the order of magnitude of real-scaleevaporation mass flow. The determined evaporation mass flows will be used in arelated project as input values for subsequent dispersion modeling in the vicinity ofthe tanks. This is relevant for questions of fire and explosion protection as well as forenvironmental protection aspects in tank farms or refineries, which use externalfloating roof tanks. The measurements presented in this paper were compared withpredictions by empirical models and investigations of evaporations from small floorspills, round-bottom flask, or from Petri dishes published in the literature. The maingoal of this paper is to test the applicability of empirical models to provide reasonableevaporation mass flows as input for CFD dispersion simulations. KW - Spill evaporation PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-504322 DO - https://doi.org/10.1002/prs.12128 VL - 39 IS - 3 SP - e12128 PB - Wiley Online Libary AN - OPUS4-50432 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kapa, Thomas A1 - Schreier, Andy A1 - Krebber, Katerina T1 - A 100-km BOFDA Assisted by First-Order Bi-Directional Raman Amplification N2 - We present, to our knowledge for the first time, a 100-km Brillouin Optical Frequency-Domain Analysis (BOFDA) employing a 200-km fiber loop. Compared to our previous publication, enhanced sensor length, sensor accuracy and spatial resolution are presented. The performance improvements are achieved by applying distributed Raman amplification (DRA) and a digital high-pass filter. We report on temperature measurements over sensing distances of 75 km and 100 km both with a 12.5-m spatial resolution. Temperature changes of 5 °C have been measured along 75 km sensing fiber. A temperature change of 30 °C has been detected at 99.5 km. KW - Distributed sensing KW - Fiber optics sensors KW - Stimulated Brillouin scattering PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-476577 DO - https://doi.org/10.3390/s19071527 SN - 1424-8220 VL - 19 IS - 7 SP - 1527, 1 EP - 9 PB - MDPI CY - Basel, Switzerland AN - OPUS4-47657 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Teng, Jun A1 - Tang, De-Hui A1 - Zhang, Xiao A1 - Hu, Wei-Hua A1 - Said, Samir A1 - Rohrmann, Rolf G. T1 - Automated modal analysis for tracking structural change during construction and operation phases N2 - The automated modal analysis (AMA) technique has attracted significant interest over the last few years, because it can track variations in modal parameters and has the potential to detect structural changes. In this paper, an improved density-based spatial clustering of applications with noise (DBSCAN) is introduced to clean the abnormal poles in a stabilization diagram. Moreover, the optimal system model order is also discussed to obtain more stable poles. A numerical Simulation and a full-scale experiment of an arch bridge are carried out to validate the effectiveness of the proposed algorithm. Subsequently, the continuous dynamic monitoring system of the bridge and the proposed algorithm are implemented to track the structural changes during the construction phase. Finally, the artificial neural network (ANN) is used to remove the temperature effect on modal frequencies so that a health index can be constructed under operational conditions. KW - Automated Modal Analysis for Tracking Structural Change during Construction and Operation Phases PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-475116 UR - https://www.mdpi.com/1424-8220/19/4/927/pdf DO - https://doi.org/10.3390/s19040927 SN - 1424-8220 VL - 19 IS - 4 SP - 927, 1 EP - 23 PB - MDPI AG CY - Basel, Switzerland AN - OPUS4-47511 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ren, J. A1 - Weigert, Florian A1 - Weber, F. A1 - Wang, Y. A1 - Choudhury, S. A1 - Xiao, J. A1 - Lauermann, I. A1 - Resch-Genger, Ute A1 - Bande, A. A1 - Petit, T. ED - Petit, Tristan T1 - Influence of surface chemistry on optical, chemical and electronic properties of blue luminescent carbon dots N2 - Carbon dots have attracted much attention due to their unique optical, chemical and electronic properties enabling a wide range of applications. The properties of carbon dots can be effectively adjusted through modifying their chemical composition. However, a major challenge remains in understanding the core and surface contributions to optical and electronic transitions. Here, three blue luminescent carbon dots with carboxyl, amino and hydroxyl groups were comprehensively characterized by UV-vis absorption and emission spectroscopy, synchrotron-based X-ray spectroscopy, and infrared spectroscopy. The influence of the surface functionality on their fluorescence was probed by pH-dependent photoluminescence measurements. Moreover, the hydrogen bonding interactions between water and the surface groups of carbon dots were characterized by infrared spectroscopy. Our results show that both core and surface electronic states of blue luminescent carbon dots contribute to electronic acceptor levels while the chemical nature of the surface groups determines the hydrogen bonding behavior of the carbon dots. This comprehensive spectroscopic study demonstrates that the surface chemistry has a profound influence on the electronic configuration and surface–water interaction of carbon dots, thus affecting their photoluminescence properties. KW - Quantum dots KW - Spectroscopy KW - UV Vis KW - Fluorescence KW - Surface chemistry PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-472325 DO - https://doi.org/10.1039/c8nr08595a SN - 2040-3372 VL - 11 IS - 4 SP - 2056 EP - 2064 PB - RSC AN - OPUS4-47232 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Priebe, Nsesheye Susan A1 - Gluth, Gregor A1 - Sturm, Patrick A1 - Vogler, Nico A1 - Kühne, Hans-Carsten T1 - Comparison of calcined illitic clays (brick clays) and low-grade kaolinitic clays as supplementary cementitious materials N2 - The use of calcined clays as supplementary cementitious materials (SCMs) has been identified as a viable option to decrease the CO2 emissions related to cement production. However, while extensive data is available about kaolinitic clays in this context, other clays such as illitic clays appear to be under-studied. Therefore, in the present study, two illitic clays were compared to two low-grade kaolinitic clays in terms of transformations in the calcination temperature range 650–900 °C, and performance of the calcined clays in blended cement pastes as measured by strength evolution, heat release, hydrated phase formation and portlandite consumption. The illitic clays required a higher calcination temperature for complete dehydroxylation of their illite than what is necessary for dehydroxylation of kaolinite. These higher calcination temperatures also led to particle sintering, significantly decreasing the specific surface area of the illitic clays, particularly for the clay with the higher Fe2O3 content. Nevertheless, while the kaolinitic clays generally exhibited the best performance as SCM, the illitic clay with lower Fe2O3 content performed similar to the kaolinitic clays when calcined at optimum temperature and applied at a moderate substitution rate. These findings demonstrate that several different clays have the potential to be used as SCM and indicate possible routes to identify suitable deposits for this purpose. KW - Blended cement KW - Calcined clay KW - Brick clay KW - Illite KW - Kaolinite PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-488195 DO - https://doi.org/10.1617/s11527-019-1393-2 SN - 1359-5997 SN - 1871-6873 N1 - Geburtsname von Priebe, Nsesheye Susan: Msinjili, N. S. - Birth name of Priebe, Nsesheye Susan: Msinjili, N. S. VL - 52 IS - 5 SP - Article Number 94 PB - Springer Nature AN - OPUS4-48819 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Otto, Peter A1 - Lorenzis, L. A1 - Unger, Jörg F. T1 - Explicit dynamics in impact simulation using a NURBS contact interface N2 - In this paper, the impact problem and the subsequent wave propagation are considered. For the contact discretization an intermediate NURBS layer is added between the contacting finite element bodies, which allows a smooth contact formulation and efficient element‐based integration. The impact event is ill‐posed and requires a regularization to avoid propagating stress oscillations. A nonlinear mesh dependent penalty regularization is used, where the stiffness of the penalty regularization increases upon mesh refinement. Explicit time integration methods are well suited for wave propagation problems, but are efficient only for diagonal mass matrices. Using a spectral element discretization and the coupled FE‐NURBS approach the bulk part of the mass matrix is diagonal. KW - Impact simulation KW - Explicit dynamics KW - Isogeometric analysis KW - Spectral elements KW - Mortar method PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-494947 DO - https://doi.org/10.1002/nme.6264 SP - 1 EP - 21 PB - Wiley Online Libary AN - OPUS4-49494 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zirnstein, Benjamin A1 - Schulze, Dietmar A1 - Schartel, Bernhard T1 - Mechanical and fire properties of multicomponent flame retardant EPDM rubbers using aluminum trihydroxide, ammonium polyphosphate, and polyaniline N2 - In this study, multicomponent flame retardant systems, consisting of Ammonium polyphosphate (APP), aluminum trihydroxide (ATH), and polyaniline (PANI), were used in ethylene propylene diene monomer (EPDM) rubber. The multicomponent system was designed to improve flame retardancy and the mechanical properties of the rubber compounds, while simultaneously reducing the amount of filler. PANI was applied at low loadings (7 phr) and combined with the phosphorous APP (21 phr) and the mineral flame retardant ATH (50 phr). A comprehensive study of six EPDM rubbers was carried out by systematically varying the fillers to explain the impact of multicomponent flame retardant systems on mechanical properties. The six EPDM materials were investigated via the UL 94, limiting oxygen index (LOI), FMVSS 302, glow wire tests, and the cone calorimeter, showing that multicomponent flame retardant systems led to improved fire performance. In cone calorimeter tests the EPDM/APP/ATH/PANI composite reduced the maximum average rate of heat emission (MARHE) to 142 kW·m-2, a value 50% lower than that for the unfilled EPDM rubber. Furthermore, the amount of phosphorus in the residues was quantified and the mode of action of the phosphorous flame retardant APP was explained. The data from the cone calorimeter were used to determine the protective layer effect of the multicomponent flame retardant systems in the EPDM compounds. KW - EPDM KW - Rubber KW - Flame retardant KW - Polyaniline KW - Aluminum trihydroxide (ATH) PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-482769 DO - https://doi.org/10.3390/ma12121932 SN - 1996-1944 VL - 12 IS - 12 SP - 1932, 1 EP - 22 PB - MDPI AN - OPUS4-48276 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hussels, Maria-Teresa A1 - Chruscicki, Sebastian A1 - Arndt, Detlef A1 - Scheider, Swen A1 - Prager, Jens A1 - Homann, Tobias A1 - Habib, Abdel Karim T1 - Localization of transient events threatening pipeline integrity by fiber-optic distributed acoustic sensing N2 - Pipe integrity is a central concern regarding technical safety, availability, and environmental compliance of industrial plants and pipelines. A condition monitoring system that detects and localizes threats in pipes prior to occurrence of actual structural failure, e.g., leakages, especially needs to target transient events such as impacts on the pipe wall or pressure waves travelling through the medium. In the present work, it is shown that fiber-optic distributed acoustic sensing (DAS) in conjunction with a suitable application geometry of the optical fiber sensor allows to track propagating acoustic waves in the pipeline wall on a fast time-scale. Therefore, short impacts on the pipe may be localized with high fidelity. Moreover, different acoustic modes are identified, and their respective group velocities are in good agreement with theoretical predications. In another set of experiments modeling realistic damage scenarios, we demonstrate that pressure waves following explosions of different gas mixtures in pipes can be observed. Velocities are verified by local piezoelectric pressure transducers. Due to the fully distributed nature of the fiber-optic sensing system, it is possible to record accelerated motions in detail. Therefore, in addition to detection and localization of threatening events for infrastructure monitoring, DAS may provide a powerful tool to study the development of gas explosions in pipes, e.g., investigation of deflagration-to-detonation-transitions (DDT). KW - Distributed acoustic sensing (DAS) KW - Distributed vibrations sensing (DVS) KW - Fiber-optic sensing KW - Condition monitoring KW - Pipeline integrity KW - Gas explosion PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-488555 DO - https://doi.org/10.3390/s19153322 SN - 1424-8220 VL - 19 IS - 15 SP - 3322, 1 EP - 20 PB - MDPI CY - Basel, CH AN - OPUS4-48855 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Provis, J. L. A1 - Arbi, K. A1 - Bernal, S. A. A1 - Bondar, D. A1 - Buchwald, A. A1 - Castel, A. A1 - Chithiraputhiran, S. A1 - Cyr, M. A1 - Dehghan, A. A1 - Dombrowski-Daube, K. A1 - Dubey, A. A1 - Ducman, V. A1 - Gluth, Gregor A1 - Nanukuttan, S. A1 - Peterson, K. A1 - Puertas, F. A1 - van Riessen, A. A1 - Torres-Carrasco, M. A1 - Ye, G. A1 - Zuo, Y. T1 - RILEM TC 247-DTA round robin test: mix design and reproducibility of compressive strength of alkali-activated concretes N2 - The aim of RILEM TC 247-DTA ‘Durability Testing of Alkali-Activated Materials’ is to identify and validate methodologies for testing the durability of alkali-activated concretes. To underpin the durability testing work of this committee, five alkali-activated concrete mixes were developed based on blast furnace slag, fly ash, and flash-calcined metakaolin. The concretes were designed with different intended performance levels, aiming to assess the capability of test methods to discriminate between concretes on this basis. A total of fifteen laboratories worldwide participated in this round robin test programme, where all concretes were produced with the same mix designs, from single-source aluminosilicate precursors and locally available aggregates. This paper reports the mix designs tested, and the compressive strength results obtained, including critical insight into reasons for the observed variability in strength within and between laboratories. KW - Alkali-activated materials KW - Alkali-activated slag KW - Compressive strength KW - Concrete KW - Mix-design PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-489131 DO - https://doi.org/10.1617/s11527-019-1396-z SN - 1359-5997 SN - 1871-6873 VL - 52 IS - 5 SP - Article Number 99 PB - Springer Nature AN - OPUS4-48913 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hoevelmann, J. A1 - Stawski, T. M. A1 - Besselink, R. A1 - Freeman, H. M. A1 - Dietmann, K. M. A1 - Mayanna, S. A1 - Pauw, Brian Richard A1 - Benning, L. G. T1 - A template-free and low temperature method for the synthesis of mesoporous magnesium phosphate with uniform pore structure and high surface area N2 - Mesoporous phosphates are a group of nanostructured materials with promising applications, particularly in biomedicine and catalysis. However, their controlled synthesis via conventional template-based routes presents a number of challenges and limitations. Here, we show how to synthesize a mesoporous Magnesium phosphate with a high surface area and a well-defined pore structure through thermal decomposition of a crystalline struvite (MgNH4PO4·6H2O) precursor. In a first step, struvite crystals with various morphologies and sizes, ranging from a few micrometers to several millimeters, had been synthesized from supersaturated aqueous solutions (saturation index (SI) between 0.5 and 4) at ambient pressure and temperature conditions. Afterwards, the crystals were thermally treated at 70–250 °C leading to the release of structurally bound water (H2O) and ammonia (NH3). By combining thermogravimetric analyses (TGA), scanning and transmission electron microscopy (SEM, TEM), N2 sorption analyses and small- and wide-angle X-ray scattering (SAXS/WAXS) we show that this decomposition process results in a pseudomorphic transformation of the original struvite into an amorphous Mg-phosphate. Of particular importance is the fact that the final material is characterized by a very uniform mesoporous structure with 2–5 nm wide pore channels, a large specific surface area of up to 300 m2 g−1 and a total pore volume of up to 0.28 cm3 g−1. Our struvite decomposition method is well controllable and reproducible and can be easily extended to the synthesis of other mesoporous phosphates. In addition, the so produced mesoporous material is a prime candidate for use in biomedical applications considering that Magnesium phosphate is a widely used, non-toxic substance that has already shown excellent biocompatibility and biodegradability. KW - Struvite KW - SAXS KW - Scattering KW - Nanoporous KW - Geology PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-477130 DO - https://doi.org/10.1039/c8nr09205b VL - 11 IS - 14 SP - 6939 EP - 6951 PB - Royal Society of Chemistry AN - OPUS4-47713 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Descalzo, Ana B. A1 - Ashokkumar, Pichandi A1 - Shen, Z. A1 - Rurack, Knut T1 - On the Aggregation Behaviour and Spectroscopic Properties of Alkylated and Annelated BoronDipyrromethene (BODIPY) Dyes in Aqueous Solution N2 - The tendency of boron-dipyrromethene (BODIPY) dyes to associate in water is well known, and usually a cause for inferior fluorescence properties. Synthetic efforts to chemically improve BODIPYs’ water solubility and minimize this problem have been numerous in the past. However, a deeper understanding of the phenomena responsible for fluorescence quenching is still required. Commonly, the spectroscopic behaviour in aqueous media has been attributed to aggregate or excimer formation, with such works often centring on a single BODIPY family. Herein, we provide an integrating discussion including very diverse types of BODIPY dyes. Our studies revealed that even subtle structural changes can distinctly affect the association behaviour of the fluorophores in water, involving different photophysical processes. The palette of behaviour found ranges from unperturbed emission, to the formation of H or J aggregates and excimers, to the involvement of tightly bound, preformed excimers. These results are a first step to a more generalized understanding of spectroscopic properties vs. structure, facilitating future molecular design of BODIPYs, especially as probes for biological applications. KW - Aggregates KW - BODIPY KW - Excimers KW - Fluorescence KW - Photophysics PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-497771 DO - https://doi.org/10.1002/cptc.201900235 SN - 2367-0932 VL - 4 IS - 2 SP - 120 EP - 131 PB - WILEY-VCH CY - Weinheim AN - OPUS4-49777 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Liu, H. A1 - Song, W. A1 - Gröninger, Delia A1 - Zhang, L. A1 - Lu, Y. A1 - Chan, K. S. A1 - Zhou, Z. A1 - Rurack, Knut A1 - Shen, Z. T1 - Real-time monitoring of newly acidified organelles during autophagy enabled by reaction-based BODIPY dyes N2 - Real-time monitoring of newly acidified organelles during autophagy in living cells is highly desirable for a better understanding of intracellular degradative processes. Herein, we describe a reaction-based boron dipyrromethene (BODIPY) dye containing strongly electron-withdrawing diethyl 2-cyanoacrylate groups at the α-positions. The probe exhibits intense red fluorescence in acidic organelles or the acidified cytosol while negligible fluorescence in other regions of the cell. The underlying mechanism is a nucleophilic reaction at the central meso-carbon of the indacene core, resulting in the loss of π-conjugation entailed by dramatic spectroscopic changes of more than 200 nm between its colorless, non-fluorescent leuco-BODIPY form and its red and brightly emitting form. The reversible transformation between red fluorescent BODIPY and leuco-BODIPY along with negligible cytotoxicity qualifies such dyes for rapid and direct intracellular lysosome imaging and cytosolic acidosis detection simultaneously without any washing step, enabling the real-time monitoring of newly acidified organelles during autophagy. KW - Autophagy KW - BODIPY KW - Fluorescence KW - Lysosome KW - Real-time imaging PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-498358 UR - https://www.nature.com/articles/s42003-019-0682-1 DO - https://doi.org/10.1038/s42003-019-0682-1 SN - 23993642 VL - 2 SP - 442 PB - Nature Research CY - London AN - OPUS4-49835 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Büchele, Dominique A1 - Chao, Madlen A1 - Ostermann, Markus A1 - Leenen, M. A1 - Bald, Ilko T1 - Multivariate chemometrics as a key tool for prediction of K and Fe in a diverse German agricultural soil-set using EDXRF N2 - Within the framework of precision agriculture, the determination of various soil properties is moving into focus, especially the demand for sensors suitable for in-situ measurements. Energy-dispersive X-ray fluorescence (EDXRF) can be a powerful tool for this purpose. In this study a huge diverse soil set (n = 598) from 12 different study sites in Germany was analysed with EDXRF. First, a principal component analysis (PCA) was performed to identify possible similarities among the sample set. Clustering was observed within the four texture classes clay, loam, silt and sand, as clay samples contain high and sandy soils low iron mass fractions. Furthermore, the potential of uni- and multivariate data evaluation with partial least squares regression (PLSR) was assessed for accurate Determination of nutrients in German agricultural samples using two calibration sample sets. Potassium and iron were chosen for testing the performance of both models. Prediction of these nutrients in 598 German soil samples with EDXRF was more accurate using PLSR which is confirmed by a better overall averaged deviation and PLSR should therefore be preferred. KW - XRF KW - Chemometrics KW - Soil KW - Agriculture KW - Multivariate PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-498671 DO - https://doi.org/10.1038/s41598-019-53426-5 VL - 9 SP - 17588 PB - Nature AN - OPUS4-49867 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yildirim, Arda A1 - Sentker, K. A1 - Smales, Glen Jacob A1 - Pauw, Brian Richard A1 - Huber, P. A1 - Schönhals, Andreas T1 - Collective orientational order and phase behavior of a discotic liquid crystal under nanoscale confinement N2 - The phase behavior and molecular ordering of hexakishexyloxy triphenylene (HAT6) DLC under cylindrical nanoconfinement is studied utilizing differential scanning calorimetry (DSC) and dielectric spectroscopy (DS), where cylindrical nanoconfinement is established through embedding HAT6 into the nanopores of anodic aluminum oxide membranes (AAO), and a silica membrane with pore diameters ranging from 161 nm down to 12 nm. Both unmodified and modified pore walls were considered, and in the latter case the pore walls of AAO membranes were chemical treated with n octadecylphosphonic acid (ODPA) resulting in the formation of a 2.2 nm thick layer of grafted alkyl chains. Phase transition enthalpies decrease with decreasing pore size, indicating that a large proportion of the HAT6 molecules within the pores has a disordered structure, which increases with decreasing pore size for both pore walls. In the case of the ODPA modification the amount of ordered HAT6 is increased compared to the unmodified case. The pore size dependencies of the phase transition temperatures were approximated using the Gibbs Thomson equation, where the estimated surface tension is dependent on the molecular ordering of HAT6 molecules within the pores and upon their surface. DS was employed to investigate the molecular ordering of HAT6 within the nanopores. These investigations revealed that with a pore size of around 38 nm, for the samples with the unmodified pore walls, the molecular ordering changes from planar axial to homeotropic radial. However, the planar axial configuration, which is suitable for electronic applications, can be successfully preserved through ODPA modification for most of the pore sizes. KW - Discotic Liquid Crystals KW - Nanoconfinement PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-475222 DO - https://doi.org/10.1039/c8na00308d SN - 2516-0230 VL - 1 IS - 3 SP - 1104 EP - 1116 PB - RSC AN - OPUS4-47522 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gramse, G. A1 - Schönhals, Andreas A1 - Kienberger, F. T1 - Nanoscale dipole dynamics of protein membranes studied by broadband dielectric microscopy N2 - We investigate the nearfield dipole mobility of protein membranes in a wide frequency range from 3 kHz to 10 GHz. The results of our nanoscale dielectric images and spectra of bacteriorhodopsin (bR) reveal Debye relaxations with time constants of τ ∼ 2 ns and τ ∼ 100 ns being characteristic of the Dipole moments of the bR retinal and α-helices, respectively. However, the dipole mobility and therefore the protein biophysical function depend critically on the amount of surface water surrounding the protein, and the characteristic mobility in the secondary structure is only observed for humidity levels <30%. Our results have been achieved by adding the frequency as a second fundamental dimension to quantitative dielectric microscopy. The key elements for the success of this advanced technique are the employed heterodyne detection scheme, the broadband electrical signal source, a high frequency optimized cabling, development of calibration procedures and precise finite element modelling. Our study demonstrates the exciting possibilities of broadband dielectric microscopy for the investigation of dynamic processes in cell bioelectricity at the individual molecular level. Furthermore, the technique may shed light on local dynamic processes in related materials science applications like semiconductor Research or nano-electronics. KW - Broadband dielectric microscopy PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-475230 DO - https://doi.org/10.1039/c8nr05880f SN - 2040-3372 VL - 11 IS - 10 SP - 4303 EP - 4309 PB - RSC AN - OPUS4-47523 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Röhsler, Andreas A1 - Sobol, Oded A1 - Unger, Wolfgang A1 - Böllinghaus, Thomas T1 - Comprehensive study of deuterium-induced effects in in austenitic stainless steel AISI 304L N2 - The damaging impact of hydrogen on the austenitic stainless steel AISI 304 L was analysed. To this aim, samples were charged electrochemically with the hydrogen isotope deuterium (2H, D) and examined with time-of-flight secondary ion mass spectrometry (ToF-SIMS) and electron backscatter diffraction (EBSD). The fusion of the obtained chemical and structural information revealed local enrichment of deuterium in austenite, transformation into martensite, crack formation and severe roughening of the specimen surface. The results indicated that martensite was not only formed during charging but also during Desorption and ToF-SIMS examinations. Furthermore, cross-sections of deuterium-charged samples revealed that in preferred deformation bands a g/ε/a 0 evolution is taking place. By means of microscopic analyses and carrier gas hot extraction (CGHE), it was found that the use of NaAsO2 as recombination poison decreased the uptake of hydrogen significantly and resulted in severe precipitation on the specimen surfaces. This is in contrast to the popular presumption that NaAsO2 enhances the uptake of hydrogen (and deuterium) during electrochemical charging by hampering its recombination from Atoms to molecules. KW - AISI 304L KW - Hydrogen KW - ToF-SIMS KW - Deuterium KW - Martensite PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-477540 DO - https://doi.org/10.1016/j.ijhydene.2019.03.058 SN - 0360-3199 SN - 1879-3487 VL - 44 IS - 23 SP - 12228 EP - 12238 PB - Elsevier Ltd. AN - OPUS4-47754 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schwibbert, Karin A1 - Menzel, F. A1 - Epperlein, N. A1 - Bonse, Jörn A1 - Krüger, Jörg T1 - Bacterial adhesion on femtosecond laser-modified polyethylene N2 - In this study, femtosecond laser-induced sub-micrometer structures are generated to modify polyethylene (PE) surface topographies. These surfaces were subjected to bacterial colonization studies with Escherichia coli and Staphylococcus aureus as test strains. The results reveal that the nanostructures do not influence S. aureus coverage, while the adhesion of E. coli is reduced. KW - Bacterial adhesion KW - Laser-modified surface KW - Polyethylene KW - Laser-induced nanostructures KW - Biofilm PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-492280 DO - https://doi.org/10.3390/ma12193107 VL - 12 IS - 19 SP - 3107 PB - MDPI CY - Basel, Schweiz AN - OPUS4-49228 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gharaati, S. A1 - Wang, Cui A1 - Förster, C. A1 - Weigert, Florian A1 - Resch-Genger, Ute A1 - Heinze, K. T1 - Triplet–Triplet Annihilation Upconversion in a MOF with AcceptorFilled Channels N2 - In summary, we report a highly modular solid TTA-UC system comprising of a crystalline, thermally stable PCN222(Pd) MOF with CA-coated MOF channels and with a DPA annihilator embedded in a solution-like environment in the MOF channels. This solid material displays blue upconverted delayed emission with a luminescence lifetime of 373 us, a threshold value of 329 mW*cm-2 and a triplet–triplet energy transfer efficiency of 82%. This optical application adds another facet to the versatile chemistry of PCN-222 MOFs. The design concept is also applicable to other TTA-UC pairs and enables tuning of the UCL color, for example, by replacing DPA with other dyes as exemplarily shown for 2,5,8,11-tetra-tert-butyl-perylene, that yields UCL at 450 nm. Current work aims to reduce the oxygen sensitivity and to increase the retention of the trapped annihilators in organic environments, for example, by tuning the chain length of the carboxylic acid and by coating the MOF surface. In addition, the TTA-UC efficiency will be further enhanced by reducing the reabsorption of the UC emission caused by Pd(TCPP) and by optimizing the sensitizer/annihilator interface. KW - Porphyrin KW - Method KW - MOF KW - Fluorescence KW - Dye KW - Sensor KW - Oxygen sensitive KW - Single molecule KW - DPA KW - Lifetime KW - Upconverstion KW - Quantum yield KW - Triplet-triplet annihilation KW - Sensitization KW - Energy transfer KW - NMR PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-500580 DO - https://doi.org/10.1002/chem.201904945 VL - 26 IS - 5 SP - 1003 EP - 1007 PB - Wiley-VCH Verlag CY - Weinheim AN - OPUS4-50058 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kembuan, C. A1 - Saleh, Maysoon I. A1 - Rühle, Bastian A1 - Resch-Genger, Ute A1 - Graf, C. T1 - Coating of upconversion nanoparticles with silica nanoshells of 5–250 nm thickness N2 - A concept for the growth of silica shells with a thickness of 5–250 nm onto oleate-coated NaYF4:Yb3+/Er3+ upconversion nanoparticles (UCNP) is presented. The concept enables the precise adjustment of shell thicknesses for the preparation of thick-shelled nanoparticles for applications in plasmonics and sensing. First, an initial 5–11 nm thick shell is grown onto the UCNPs in a reverse microemulsion. This is followed by a stepwise growth of these particles without a purification step, where in each step equal volumes of tetraethyl orthosilicate and ammonia water are added, while the volumes of cyclohexane and the surfactant Igepal® CO-520 are increased so that the ammonia water and surfactant concentrations remain constant. Hence, the number of micelles stays constant, and their size is increased to accommodate the growing core–shell particles. Consequently, the formation of core-free silica particles is suppressed. When the negative zeta potential of the particles, which continuously decreased during the stepwise growth, falls below −40 mV, the particles can be dispersed in an ammoniacal ethanol solution and grown further by the continuous addition of tetraethyl orthosilicate to a diameter larger than 500 nm. Due to the high colloidal stability, a coalescence of the particles can be suppressed, and single-core particles are obtained. This strategy can be easily transferred to other nanomaterials for the design of plasmonic nanoconstructs and sensor systems. KW - Reverse microemulsion KW - Silica coating KW - Stepwise growth KW - Thick shells KW - Upconversion nanoparticles PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-502769 DO - https://doi.org/10.3762/bjnano.10.231 SN - 2190-4286 VL - 10 SP - 2410 EP - 2421 PB - Beilstein-Institut zur Förderung der Chemischen Wissenschaften CY - Frankfurt, M. AN - OPUS4-50276 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Javaheri, E. A1 - Lubritz, J. A1 - Graf, B. A1 - Rethmeier, Michael T1 - Mechanical Properties Characterization of Welded Automotive Steels N2 - Among the various welding technologies, resistance spot welding (RSW) and laser beam welding (LBW) play a significant role as joining methods for the automobile industry. The application of RSW and LBW for the automotive body alters the microstructure in the welded areas. It is necessary to identify the mechanical properties of the welded material to be able to make a reliable statement about the material behavior and the strength of welded components. This study develops a method by which to determine the mechanical properties for the weldment of RSW and LBW for two dual phase (DP) steels, DP600 and DP1000, which are commonly used for the automotive bodies. The mechanical properties of the resistance spot weldment were obtained by performing tensile tests on the notched tensile specimen to cause an elongation of the notched and welded area in order to investigate its properties. In order to determine the mechanical properties of the laser beam weldment, indentation tests were performed on the welded material to calculate its force-penetration depth-curve. Inverse numerical simulation was used to simulate the indentation tests to determine and verify the parameters of a nonlinear isotropic material model for the weldment of LBW. Furthermore, using this method, the parameters for the material model of RSW were verified. The material parameters and microstructure of the weldment of RSW and LBW are compared and discussed. The results show that the novel method introduced in this work is a valid approach to determine the mechanical properties of welded high-strength steel structures. In addition, it can be seen that LBW and RSW lead to a reduction in ductility and an increase in the amount of yield and tensile strength of both DP600 and DP1000. KW - Mechanical property KW - Laser beam welding KW - Dual phase steel KW - Resistance spot welding PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-502269 DO - https://doi.org/10.3390/met10010001 VL - 10 IS - 1 SP - 1 EP - 20 PB - MDPI AN - OPUS4-50226 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Radnik, Jörg A1 - Dang, T. T. H. A1 - Gatla, S. A1 - Raghuwanshi, V. S. A1 - Tatchev, D. A1 - Hoell, A. T1 - Identifying the location of Cu ions in nanostructured SAPO-5 molecular sieves and its impact on the redox properties N2 - Combining X-ray Absorption Fine Spectroscopy (XAFS) with Anomalous Small-Angle X-ray Scattering (ASAXS) determines the location of Cu2+ ions in silicoaluminophosphate (SAPO-5) frameworks prepared by hydrothermal crystallization or impregnation. As expected, for the hydrothermally prepared sample, incorporation in the SAPO-5 framework was observed. For the first time preferential location of Cu2+ ions at the inner and outer surfaces of the framework is determined. Temperature-Programmed Reduction (TPR) and X-ray Photoelectron Spectroscopy (XPS) investigations demonstrated that such Cu2+ is stable in an argon (Ar) atmosphere up to 550 °C and can only be reduced under a hydrogen atmosphere. In contrast, Cu2+ deposited by impregnation on the pure SAPO-5 framework can be easily reduced to Cu+ in an Ar atmosphere. At lower Cu amounts, mononuclear tetrahedrally coordinated Cu species were formed which are relatively stable in the monovalent form. In contrast, at higher Cu amounts, CuO particles were found which change easily between the mono- and bivalent species. KW - Nanostructured material KW - Molecular sieves KW - X-ray absorption Fine Spectroscopy KW - Anomalous Small Angle X-ray Scattering KW - X-ray Photoelectron Spectroscopy PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-474793 DO - https://doi.org/10.1039/c8ra10417d SN - 2046-2069 VL - 9 IS - 12 SP - 6429 EP - 6437 PB - RSC AN - OPUS4-47479 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lisec, Jan A1 - Jaeger, Carsten A1 - Rashid, R. A1 - Munir, R. A1 - Zaidi, N. T1 - Cancer cell lipid class homeostasis is altered under nutrient-deprivation but stable under hypoxia N2 - Background: Cancer cells modify the balance between fatty acid (FA) synthesis and uptake under metabolic stress, induced by oxygen/nutrient deprivation. These modifications were shown to alter the levels of individual triglyceride (TG) or phospholipid sub-species. To attain a holistic overview of the lipidomic profiles of cancer cells under stress we performed a broad lipidomic assay, comprising 244 lipids from six major classes. This assay allowed us to perform robust analyses and assess the changes in averages of broader lipid-classes, stratified on the basis of saturation index of their fatty-acyl side chains. Methods: Global lipidomic profiling using Liquid Chromatography-Mass Spectrometry was performed to assess lipidomic profiles of biologically diverse cancer cell lines cultivated under metabolically stressed conditions. Results: Neutral lipid compositions were markedly modified under serum-deprived conditions and, strikingly, the cellular level of triglyceride subspecies decreased with increasing number of double bonds in their fatty acyl chains. In contrast and unexpectedly, no robust changes were observed in lipidomic profiles of hypoxic (2% O2) Cancer cells despite concurrent changes in proliferation rates and metabolic gene expression. Conclusions: Serum-deprivation significantly affects lipidomic profiles of cancer cells. Although, the levels of individual lipid moieties alter under hypoxia (2% O2), the robust averages of broader lipid classes remain unchanged. KW - Tumor metabolism KW - Fatty acid metabolism KW - Lipidomic profile KW - Metabolic stress PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-481061 DO - https://doi.org/10.1186/s12885-019-5733-y SN - 1471-2407 VL - 19 SP - 501, 1 EP - 11 PB - Springer Nature AN - OPUS4-48106 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Duewer, D. L. A1 - Murray, J. A. A1 - Wood, L. J. A1 - Wise, S. A. A1 - Hein, Sebastian A1 - Koch, Matthias A1 - Philipp, Rosemarie A1 - Werneburg, Martina A1 - Hackenberg, R. A1 - Polzer, J. A1 - Avila, M. A. A1 - Serrano, V. A1 - Kakoulides, E. A1 - Alexopoulos, C. A1 - Giannikopoulou, P. A1 - Gui, E. M. A1 - Lu, T. A1 - Teo, T. L. A1 - Hua, T. A1 - Dazhou, C. A1 - Chunxin, L. A1 - Changjun, Y. A1 - Hongmei, L. A1 - Nammoonnoy, J. A1 - Sander, L. C. A1 - Lippa, K. A1 - Quinn, L. A1 - Swiegelaar, C. A1 - Fernandes-Whaley, M. A1 - Gören, A. C. A1 - Gökcen, T. T1 - CCQM-K95.1 Low-polarity analytes in a botanical matrix: Polycyclic aromatic hydrocarbons (PAHs) in tea N2 - Extraction, chromatographic separation, and quantification of low-concentration organic compounds in complex matrices are core challenges for reference material producers and providers of calibration services. Evidence of successful participation in formal, relevant international comparisons is needed to document measurement capability claims made by national metrology institutes (NMIs) and designated institutes (DIs). To enable NMIs and DIs to update or establish their claims, in 2014 the Organic Analysis Working Group (OAWG) initiated CCQM-K95.1 "Low-Polarity Analytes in a Botanical Matrix: Polycyclic Aromatic Hydrocarbons (PAHs) in Tea". This was a follow-on comparison from CCQM-K95 which was completed in 2014. The polycyclic aromatic hydrocarbons (PAHs) benz[a]anthracene (BaA) and benzo[a]pyrene (BaP) are considered priority pollutants by U.S. Environmental Protection Agency and are regulated contaminants in food, pose chromatographic separation challenges, and for which exist well-characterized measurement procedures and standard materials. BaA and BaP in a smoked tea were therefore selected as representative target measurands for CCQM-K95.1. Ten NMIs participated in CCQM-K95.1. The consensus summary mass fractions for the two PAHs are in the range of (50 to 70) ng/g with relative standard deviations of (6 to 10) %. Successful participation in CCQM K95.1 demonstrates the following measurement capabilities in determining mass fraction of organic compounds, with molar mass of 100 g/mol to 500 g/mol and having polarity pKow −2, in a botanical matrix ranging in mass fraction from 10 ng/g to 1000 ng/g: (1) value assignment of primary reference standards (if in-house purity assessment carried out), (2) value assignment of single and/or multi-component organic solutions, (3) extraction of analytes of interest from the matrix, (4) cleanup and separation of analytes of interest from interfering matrix or extract components, and (5) separation and quantification using gas chromatography or liquid chromatography. KW - Benz[a]anthracene (BaA) KW - Benzo[a]pyrene (BaP) KW - Gas chromatography (GC) KW - Isotope dilution (ID) KW - Liquid chromatography (LC) KW - Mass spectrometry (MS) KW - Polycyclic aromatic hydrocarbon (PAH) KW - Yerba mate tea PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-471430 DO - https://doi.org/10.1088/0026-1394/56/1A/08002 SN - 0026-1394 SN - 1681-7575 VL - 56 IS - 1 A SP - 08002, 1 EP - 89 PB - IOP Science AN - OPUS4-47143 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brüngel, R. A1 - Rückert, J. A1 - Wohlleben, W. A1 - Babick, F. A1 - Ghanem, A. A1 - Gaillard, C. A1 - Mech, A. A1 - Rauscher, H. A1 - Hodoroaba, Vasile-Dan A1 - Weigel, S. A1 - Friedrich, C. M. T1 - NanoDefiner e-Tool: An Implemented Decision Support Framework for Nanomaterial Identification N2 - The European Commission’s recommendation on the definition of nanomaterial (2011/696/EU) established an applicable standard for material categorization. However, manufacturers face regulatory challenges during registration of their products. Reliable categorization is difficult and requires considerable expertise in existing measurement techniques (MTs). Additionally, organizational complexity is increased as different authorities’ registration processes require distinct reporting. The NanoDefine project tackled these obstacles by providing the NanoDefiner e-tool: A decision support expert system for nanomaterial identification in a regulatory context. It providesMT recommendations for categorization of specific materials using a tiered approach (screening/confirmatory), and was constructed with experts from academia and industry to be extensible, interoperable, and adaptable for forthcoming revisions of the nanomaterial definition. An implemented MT-driven material categorization scheme allows detailed description. Its guided workflow is suitable for a variety of user groups. Direct feedback and explanation enable transparent decisions. Expert knowledge is Held in a knowledge base for representation of MT performance criteria and physicochemical particle type properties. Continuous revision ensured data quality and validity. Recommendations were validated by independent case studies on industry-relevant particulate materials. Besides supporting material identification and registration, the free and open-source e-tool may serve as template for other expert systems within the nanoscience domain. KW - EC nanomaterial definition KW - Decision support KW - Expert system KW - Nanomaterial KW - Nanoparticles PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-492449 DO - https://doi.org/10.3390/ma12193247 VL - 12 IS - 19 SP - 3247 PB - MDPI CY - Basel, CH AN - OPUS4-49244 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nöller, Renate A1 - Danielewski, A. A1 - Giel, R. A1 - Overgaauw, E. A1 - Hahn, Oliver T1 - Material analysis of Aztec codices in Berlin. Assignment of small fragments compiled as cutouts on one plate in Humboldt’s “Atlas pittoresque du voyage” N2 - The collection Manuscripta Americana in Berlin consists of fragmented codices acquired by Alexander von Humboldt in Mexico. Some of these Humboldt Codices are published as hieroglyphic writings of the Aztecs in “Vues des Cordilleres et Monuments des Peuples indigènes de l’Amerique”. Starting from a special compilation of seven fragments on plate 36 in the “Atlas”, we investigated the corresponding original fragments using material analysis in order to clarify their historical relations. The analyses were carried out with X-ray fluorescence analysis, VIS spectroscopy, and infrared spectroscopy in diffuse reflection and revealed typical indigenous colors like cochineal, indigo, and organic yellows (e.g. mangrove and zacatlaxcalli). Four fragments under investigation show exactly the same material and thus must once have belonged together in one compendium. An additional manuscript from Mizquiahuala also shown on plate 36 can be matched to another one that is not published in the “Atlas”. KW - Manuscripts KW - Alexander von Humboldt KW - Non-destructiv testing KW - Colourants KW - Writing materials PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-498971 DO - https://doi.org/10.1080/20548923.2019.1682816 SN - 2054-8923 SP - 1 EP - 14 PB - Routledge, Taylor & Francis Group CY - London AN - OPUS4-49897 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Greco, A. A1 - Starostin, V. A1 - Karapanagiotis, Christos A1 - Hinderhofer, A. A1 - Gerlach, A. A1 - Pithan, L. A1 - Liehr, Sascha A1 - Schreiber, Frank A1 - Kowarik, Stefan T1 - Fast fitting of reflectivity data of growing thin films using neural networks N2 - X-ray reflectivity (XRR) is a powerful and popular scattering technique that can give valuable insight into the growth behavior of thin films. This study Shows how a simple artificial neural network model can be used to determine the thickness, roughness and density of thin films of different organic semiconductors [diindenoperylene, copper(II) phthalocyanine and alpha-sexithiophene] on silica from their XRR data with millisecond computation time and with minimal user input or a priori knowledge. For a large experimental data set of 372 XRR curves, it is shown that a simple fully connected model can provide good results with a mean absolute percentage error of 8–18% when compared with the results obtained by a genetic least mean squares fit using the classical Parratt formalism. Furthermore, current drawbacks and prospects for improvement are discussed. KW - Artificial neural networks KW - X-ray reflectivity PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-498997 DO - https://doi.org/10.1107/S1600576719013311 SN - 1600-5767 VL - 52 SP - 1342 EP - 1347 PB - Wiley AN - OPUS4-49899 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Buljak, V. A1 - Oesch, Tyler A1 - Bruno, Giovanni T1 - Simulating fiber-reinforced concrete mechanical performance using CT-based fiber orientation data N2 - The main hindrance to realistic models of fiber-reinforced concrete (FRC) is the local materials property variation, which does not yet reliably allow simulations at the structural level. The idea presented in this paper makes use of an existing constitutive model, but resolves the problem of localized material variation through X-ray computed tomography (CT)-based pre-processing. First, a three-point bending test of a notched beam is considered, where pre-test fiber orientations are measured using CT. A numerical model is then built with the zone subjected to progressive damage, modeled using an orthotropic damage model. To each of the finite elements within this zone, a local coordinate system is assigned, with its longitudinal direction defined by local fiber orientations. Second, the parameters of the constitutive damage model are determined through inverse analysis using load-displacement data obtained from the test. These parameters are considered to clearly explain the material behavior for any arbitrary external action and fiber orientation, for the same geometrical properties and volumetric ratio of fibers. Third, the effectiveness of the resulting model is demonstrated using a second, “control” experiment. The results of the “control” experiment analyzed in this research compare well with the model results. The ultimate strength was predicted with an error of about 6%, while the work-of-load was predicted within 4%. It demonstrates the potential of this method for accurately predicting the mechanical performance of FRC components. KW - Fiber-reinforced concrete KW - X-ray computed tomography (CT) KW - Anisotropic fiber orientation KW - Inverse analysis PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-474728 DO - https://doi.org/10.3390/ma12050717 SN - 1996-1944 VL - 12 IS - 5 SP - 717, 1 EP - 16 PB - MDPI AN - OPUS4-47472 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Artzt, K. A1 - Haubrich, J. A1 - Requena, G. A1 - Bruno, Giovanni T1 - Exploring the correlation between subsurface residual stresses and manufacturing parameters in laser powder bed fused Ti-6Al-4V N2 - Subsurface residual stresses (RS) were investigated in Ti-6Al-4V cuboid samples by means of X-ray synchrotron diffraction. The samples were manufactured by laser powder bed fusion (LPBF) applying different processing parameters, not commonly considered in open literature, in order to assess their influence on RS state. While investigating the effect of process parameters used for the calculation of volumetric energy density (such as laser velocity, laser power and hatch distance), we observed that an increase of energy density led to a decrease of RS, although not to the same extent for every parameter variation. Additionally, the effect of support structure, sample roughness and LPBF machine effects potentially coming from Ar flow were studied. We observed no influence of support structure on subsurface RS while the orientation with respect to Ar flow showed to have an impact on RS.We conclude recommending monitoring such parameters to improve part reliability and reproducibility. KW - Additive manufacturing KW - Synchrotron X-ray diffraction KW - Residual stress KW - Ti-6Al-4V PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-474281 DO - https://doi.org/10.3390/met9020261 SN - 2075-4701 VL - 9 IS - 2 SP - 261, 1 EP - 13 PB - MDPI AN - OPUS4-47428 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Laquai, René A1 - Gouraud, F. A1 - Müller, Bernd R. A1 - Huger, M. A1 - Chotard, T. A1 - Antou, G. A1 - Bruno, Giovanni T1 - Evolution of Thermal Microcracking in Refractory ZrO2-SiO2 after Application of External Loads at High Temperatures N2 - Zirconia-based cast refractories are widely used for glass furnace applications. Since they have to withstand harsh chemical as well as thermo-mechanical environments, internal stresses and microcracking are often present in such materials under operating conditions (sometimes in excess of 1700 °C). We studied the evolution of thermal (CTE) and mechanical (Young’s modulus) properties as a function of temperature in a fused-cast refractory containing 94 wt.% of monoclinic ZrO2 and 6 wt.% of a silicate glassy phase. With the aid of X-ray refraction techniques (yielding the internal specific surface in materials), we also monitored the evolution of microcracking as a function of thermal cycles (crossing the martensitic phase transformation around 1000 °C) under externally applied stress. We found that external compressive stress leads to a strong decrease of the internal surface per unit volume, but a tensile load has a similar (though not so strong) effect. In agreement with existing literature on -eucryptite microcracked ceramics, we could explain These phenomena by microcrack closure in the load direction in the compression case, and by microcrack propagation (rather than microcrack nucleation) under tensile conditions. KW - Electro-fused zirconia KW - Microcracking KW - Synchrotron x-ray refraction radiography (SXRR) KW - Thermal expansion PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-477431 DO - https://doi.org/10.3390/ma12071017 VL - 12 IS - 7 SP - 1 EP - 15 PB - MDPI AN - OPUS4-47743 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mieller, Björn T1 - Influence of test procedure on dielectric breakdown strength of alumina N2 - Dielectric strength testing of ceramics can be performed with various setups and parameters. Comparisons of results from different sources are often not meaningful, because the results are strongly dependent on the actual testing procedure. The aim of this study is to quantify the influence of voltage ramp rate, electrode size, electrode conditioning, and sample thickness on the measured AC dielectric strength of a commercial alumina. Mean values, Weibull moduli, and failure probabilities determined in standardized short time tests are evaluated and related to withstand voltage tests. Dielectric strength values in the range from 21.6 to 33.2 kV/mm were obtained for the same material using different testing procedures. Short time tests resulted in small standard deviations (< 2 kV/mm) and high Weibull moduli around 30, while withstand tests at voltage levels with low and virtual zero failure probability in short time tests resulted in large scatter of withstand time and Weibull moduli < 1. The strong decrease in Weibull moduli is attributed to progressive damage from partial discharge and depolarization during AC testing. These findings emphasize the necessity of a thorough documentation of testing procedure and highlight the importance of withstand voltage tests for a comprehensive material characterization. KW - Ceramic KW - High-voltage testing KW - Dielectric breakdown KW - Alumina PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-483852 DO - https://doi.org/10.1007/s40145-018-0310-4 SN - 2226-4108 SN - 2227-8508 VL - 8 IS - 2 SP - 247 EP - 255 PB - Springer AN - OPUS4-48385 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Strangfeld, Christoph A1 - Johann, Sergej A1 - Bartholmai, Matthias T1 - Smart RFID Sensors Embedded in Building Structures for Early Damage Detection and Long-Term Monitoring N2 - In civil engineering, many structures are made of reinforced concrete. Most Degradation processes relevant to this material, e.g., corrosion, are related to an increased level of material moisture. Therefore, moisture monitoring in reinforced concrete is regarded as a crucial method for structural health monitoring. In this study, passive radio frequency identification (RFID)-based sensors are embedded into the concrete. They are well suited for long-term operation over decades and are well protected against harsh environmental conditions. The energy supply and the data transfer of the humidity sensors are provided by RFID. The sensor casing materials are optimised to withstand the high alkaline environment in concrete, having pH values of more than 12. Membrane materials are also investigated to identify materials capable of enabling water vapour transport from the porous cement matrix to the embedded humidity sensor. By measuring the corresponding relative humidity with embedded passive RFID-based sensors, the cement hydration is monitored for 170 days. Moreover, long-term moisture monitoring is performed for more than 1000 days. The Experiments show that embedded passive RFID-based sensors are highly suitable for long-term structural health monitoring in civil engineering. KW - RFID based sensors KW - Embedded sensors KW - Corresponding relative humidity KW - Porous building materials KW - Reinforced concrete KW - Corrosion KW - Civil engineering PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-500831 DO - https://doi.org/10.3390/s19245514 VL - 19 IS - 24 SP - 1 EP - 18 PB - MDPI CY - Basel, Swiss AN - OPUS4-50083 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sebald, M.A. A1 - Gebauer, J. A1 - Sommerfeld, Thomas A1 - Koch, Matthias T1 - First Synthesis of (−)-Altenuene-D3 Suitable as Internal Standard for Isotope Dilution Mass Spectrometry N2 - Metabolites from Alternaria fungi exhibit a variety of biological properties such as phytotoxic, cytotoxic, or antimicrobial activity. Optimization of a literature procedure culminated in an efficient total synthesis of (−)-altenuene as well as a stable isotope-labeled derivative suitable for implementation in a LC-MS/MS method for mycotoxin analysis. KW - Altenuene KW - Alternaria mycotoxins KW - Food safety KW - Isotope-labeled KW - SIDA-LC-MS/MS KW - Suzuki coupling PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-500696 DO - https://doi.org/10.3390/molecules24244563 SN - 1420-3049 VL - 24 SP - 4563 PB - MDPI CY - Basel AN - OPUS4-50069 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kneipp, Janina A1 - Zancajo, Victor M.R. A1 - Diehn, S. A1 - Filiba, N. A1 - Elbaum, R. T1 - Spectroscopic Discrimination of Sorghum Silica Phytoliths N2 - Grasses accumulate silicon in the form of silicic acid, which is precipitated as amorphous silica in microscopic particles termed phytoliths. These particles comprise a variety of morphologies according to the cell type in which the silica was deposited. Despite the evident morphological differences, phytolith chemistry has mostly been analysed in bulk samples, neglecting differences between the varied types formed in the same species. In this work, we extracted leaf phytoliths from mature plants of Sorghum bicolor (L.) Moench. Using solid state NMR and thermogravimetric analysis, we show that the extraction methods alter greatly the silica molecular structure, its condensation degree and the trapped organic matter. Measurements of individual phytoliths by Raman and synchrotron FTIR microspectroscopies in combination with multivariate analysis separated bilobate silica cells from prickles and long cells, based on the silica molecular structures and the fraction and composition of occluded organic matter. The variations in structure and composition of sorghum phytoliths suggest that the biological pathways leading to silica deposition vary between these cell types. KW - Phytoliths KW - Biosilicification KW - Raman KW - Sorghum KW - Solid state NMR KW - Synchrotron FTIR PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-502672 DO - https://doi.org/10.3389/fpls.2019.01571 VL - 10 SP - 1571 PB - Frontiers Media CY - Lausanne AN - OPUS4-50267 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schmidt, C. A1 - Hensen, C. A1 - Wallmann, K. A1 - Liebetrau, V. A1 - Tatzel, Michael A1 - Schurr, S. L. A1 - Kutterolf, S. A1 - Haffert, L. A1 - Geilert, Sonja A1 - Hübscher, C. A1 - Lebas, E. A1 - Heuser, A. A1 - Schmidt, M. A1 - Strauss, H. A1 - Vogl, Jochen A1 - Hansteen, T. T1 - Origin of High Mg and SO4 Fluids in Sediments of the Terceira Rift, Azores‐Indications for Caminite Dissolution in a Waning Hydrothermal System N2 - During R/V Meteor cruise 141/1, pore fluids of near surface sediments were investigated to find indications for hydrothermal activity in the Terceira Rift (TR), a hyperslow spreading center in the Central North Atlantic Ocean. To date, submarine hydrothermal fluid venting in the TR has only been reported for the D. João de Castro seamount, which presently seems to be inactive. Pore fluids sampled close to a volcanic cone at 2,800‐m water depth show an anomalous composition with Mg, SO4, and total alkalinity concentrations significantly higher than seawater and a nearby reference core. The most straightforward way of interpreting these deviations is the dissolution of the hydrothermally formed mineral caminite (MgSO4 0.25 Mg (OH)2 0.2H2O). This interpretation is corroborated by a thorough investigation of fluid isotope systems (δ26Mg, δ30Si, δ34S, δ44/42Ca, and 87Sr/86Sr). Caminite is known from mineral assemblages with anhydrite and forms in hydrothermal recharge zones only under specific conditions such as high fluid temperatures and in altered oceanic crust, which are conditions generally met at the TR. We hypothesize that caminite was formed during hydrothermal activity and is now dissolving during the waning state of the hydrothermal system, so that caminite mineralization is shifted out of its stability zone. Ongoing fluid circulation through the basement is transporting the geochemical signal via slow advection toward the seafloor. KW - Isotope ratio KW - Delta value KW - Pore fluids KW - Magnesium KW - Hydrothermal fluid PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-503430 DO - https://doi.org/10.1029/2019GC008525 VL - 20 IS - 12 SP - 6078 EP - 6094 PB - Wiley AN - OPUS4-50343 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sarhan, R. M. A1 - Koopman, W. A1 - Schuetz, R. A1 - Schmid, Thomas A1 - Liebig, F. A1 - Koetz, J. A1 - Bargheer, M. T1 - The importance of plasmonic heating for the plasmondriven photodimerization of 4-nitrothiophenol N2 - Metal nanoparticles form potent nanoreactors, driven by the optical generation of energetic electrons and nanoscale heat. The relative influence of these two factors on nanoscale chemistry is strongly debated. This article discusses the temperature dependence of the dimerization of 4-nitrothiophenol (4-NTP) into 4,4′-dimercaptoazobenzene (DMAB) adsorbed on gold nanoflowers by Surface-Enhanced Raman Scattering (SERS). Raman thermometry shows a significant optical heating of the particles. The ratio of the Stokes and the anti-Stokes Raman signal moreover demonstrates that the molecular temperature during the reaction rises beyond the average crystal lattice temperature of the plasmonic particles. The product bands have an even higher temperature than reactant bands, which suggests that the reaction proceeds preferentially at thermal hot spots. In addition, kinetic measurements of the reaction during external heating of the reaction environment yield a considerable rise of the reaction rate with temperature. Despite this significant heating effects, a comparison of SERS spectra recorded after heating the sample by an external heater to spectra recorded after prolonged illumination shows that the reaction is strictly photo-driven. While in both cases the temperature increase is comparable, the dimerization occurs only in the presence of light. Intensity dependent measurements at fixed temperatures confirm this finding. KW - Nanoparticles KW - Plasmonic heating KW - Raman spectroscopy PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-475140 DO - https://doi.org/10.1038/s41598-019-38627-2 SN - 2045-2322 VL - 9 IS - 1 SP - 3060, 1 EP - 8 PB - Nature Publishing Group AN - OPUS4-47514 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Domonov, D.P. A1 - Pechenyuk, S.I. A1 - Semushina, Y.P. A1 - Yusenko, Kirill T1 - Solid state transformation in inner coordination sphere of [Co(NH3)6][Fe(C2O4)3]·3H2O as a route to access catalytically active Co-Fe materials N2 - Thermal decomposition of [Co(NH₃)₆][Fe(C₂O₄)₃]∙3H₂O in argon atmosphere, at a low heating rate (3°/min), and in large amounts of the initial complex (~0.1 mole), has been studied. It was possible to distinguish four decomposition steps upon heating: In the temperature range of 50⁻100 °C-the loss of crystal water; 100⁻190 °C-stability region of dehydrated complex; 230⁻270 °C-the range of stability of intermediate phase with the formula CoFe(NH₃)₂(C₂O₄)₂; 270⁻350 °C-thermal decomposition of the intermediate with the formation of metallic products and further air oxidation with the formation of Co1.5Fe1.5O₄. Catalytic properties of thermolysis products were tested in the decomposition reaction of H₂O₂ (inactive), oxidation of acetone (average activity), and decomposition of ammonium perchlorate (highly active). KW - Double complex salts KW - Catalysts KW - Single-source precursors PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-474014 DO - https://doi.org/10.3390/ma12020221 SN - 1996-1944 VL - 12 IS - 2 SP - 221, 1 EP - 10 PB - mdpi CY - Zürich AN - OPUS4-47401 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mekonnen, Tessema Fenta A1 - Panne, Ulrich A1 - Koch, Matthias T1 - Glucosylation and Glutathione Conjugation of Chlorpyrifos and Fluopyram Metabolites Using Electrochemistry/Mass Spectrometry N2 - Xenobiotics and their reactive metabolites are conjugated with native biomolecules such as glutathione and glucoside during phase II metabolism. Toxic metabolites are usually detoxified during this step. On the other hand, these reactive species have a potential health impact by disrupting many enzymatic functions. Thus, it is crucial to understand phase II conjugation reactions of xenobiotics in order to address their fate and possible toxicity mechanisms. Additionally, conventional methods (in vivo and in vitro) have limitation due to matrix complexity and time-consuming. Hence, developing fast and matrix-free alternative method is highly demandable. In this work, oxidative phase I metabolites and reactive species of chlorpyrifos (insecticide) and fluopyram (fungicide) were electrochemically produced by using a boron-doped diamond electrode coupled online to electrospray mass spectrometry (ESI-MS). Reactive species of the substrates were trapped by biomolecules (glutathione and glucoside) and phase II conjugative metabolites were identified using liquid chromatography (LC)-MS/MS, and/or Triple time of flight (TripleTOF)-MS. Glutathione conjugates and glucosylation of chlorpyrifos, trichloropyridinol, oxon, and monohydroxyl fluopyram were identified successfully. Glutathione and glucoside were conjugated with chlorpyrifos, trichloropyridinol, and oxon by losing a neutral HCl. In the case of fluopyram, its monohydroxyl metabolite was actively conjugated with both glutathione and glucoside. In summary, seven bioconjugates of CPF and its metabolites and two bioconjugates of fluopyram metabolites were identified using electrochemistry (EC)/MS for the first time in this work. The work could be used as an alternative approach to identify glutathione and glucosylation conjugation reactions of other organic compounds too. It is important, especially to predict phase II conjugation within a short time and matrix-free environment. KW - Pesticide KW - Bioconjugation KW - Oxidative metabolism KW - EC/MS PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-475932 DO - https://doi.org/10.3390/molecules24050898 VL - 24 IS - 5 SP - 898 EP - 910 PB - MDPI AN - OPUS4-47593 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Choi, Youngeun A1 - Schmidt, Carsten A1 - Tinnefeld, Philip A1 - Bald, Ilko A1 - Roedinger, Stefan T1 - A new reporter design based on DNA origami nanostructures for quantification of short oligonucleotides using microbeads N2 - The DNA origami technique has great potential for the development of brighter and more sensitive reporters for fluorescence based detection schemes such as a microbead-based assay in diagnostic applications. The nanostructures can be programmed to include multiple dye molecules to enhance the measured signal as well as multiple probe strands to increase the binding strength of the target oligonucleotide to these nanostructures. Here we present a proof-of-concept study to quantify short oligonucleotides by developing a novel DNA origami based reporter system, combined with planar microbead assays. Analysis of the assays using the VideoScan digital imaging platform showed DNA origami to be a more suitable reporter candidate for quantification of the target oligonucleotides at lower concentrations than a conventional reporter that consists of one dye molecule attached to a single stranded DNA. Efforts have been made to conduct multiplexed analysis of different targets as well as to enhance fluorescence signals obtained from the reporters. We therefore believe that the quantification of short oligonucleotides that exist in low copy numbers is achieved in a better way with the DNA origami nanostructures as reporters. KW - Origami KW - Nanostructures KW - Microbeads KW - DNA origami KW - Oligonucleotides PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-476443 DO - https://doi.org/10.1038/s41598-019-41136-x SN - 2045-2322 VL - 9 SP - 4769, 1 EP - 8 PB - Nature AN - OPUS4-47644 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Treiling, S. A1 - Wang, Cui A1 - Förster, C. A1 - Reichenauer, F. A1 - Kalmbach, J. A1 - Boden, P. A1 - Harris, J. P. A1 - Carrella, L. M. A1 - Rentschler, E. A1 - Resch-Genger, Ute A1 - Reber, C. A1 - Seitz, M. A1 - Gerhards, M. A1 - Heinze, K. T1 - Luminescence and Light-Driven Energy and Electron Transfer from an Exceptionally Long-Lived Excited State of a Non-Innocent Chromium(III) Complex N2 - Photoactive metal complexes employing Earth‐abundant metal ions are a key to sustainable photophysical and photochemical applications. We exploit the effects of an inversion center and ligand non‐innocence to tune the luminescence and photochemistry of the excited state of the [CrN6] chromophore [Cr(tpe)2]3+ with close to octahedral symmetry (tpe=1,1,1‐tris(pyrid‐2‐yl)ethane). [Cr(tpe)2]3+ exhibits the longest luminescence lifetime (τ=4500 μs) reported up to date for a molecular polypyridyl chromium(III) complex together with a very high luminescence quantum yield of Φ=8.2 % at room temperature in fluid solution. Furthermore, the tpe ligands in [Cr(tpe)2]3+ are redox non‐innocent, leading to reversible reductive chemistry. The excited state redox potential and lifetime of [Cr(tpe)2]3+ surpass those of the classical photosensitizer [Ru(bpy)3]2+ (bpy=2,2′‐bipyridine) enabling energy transfer (to oxygen) and photoredox processes (with azulene and tri(n‐butyl)amine). KW - Quantum yield KW - Cr(III) complex KW - Longst luminescence lifetime KW - Electron transfer PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-494870 DO - https://doi.org/10.1002/anie.201909325 VL - 58 SP - 2 EP - 13 PB - Wiley-VCH AN - OPUS4-49487 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -