TY - JOUR A1 - Gottlieb, Cassian A1 - Millar, Steven A1 - Grothe, S. A1 - Wilsch, Gerd T1 - 2D evaluation of spectral LIBS data derived from heterogeneous materials using cluster algorithm JF - Spectrochimica Acta Part B N2 - Laser-induced Breakdown Spectroscopy (LIBS) is capable of providing spatially resolved element maps in regard to the chemical composition of the sample. The evaluation of heterogeneous materials is often a challenging task, especially in the case of phase boundaries. In order to determine information about a certain phase of a material, the need for a method that offers an objective evaluation is necessary. This paper will introduce a cluster algorithm in the case of heterogeneous building materials (concrete) to separate the spectral information of non-relevant aggregates and cement matrix. In civil engineering, the information about the quantitative ingress of harmful species like Cl−, Na+ and SO2−4 is of great interest in the evaluation of the remaining lifetime of structures (Millar et al., 2015; Wilsch et al., 2005). These species trigger different damage processes such as the alkali-silica reaction (ASR) or the chloride-induced corrosion of the reinforcement. Therefore, a discrimination between the different phases, mainly cement matrix and aggregates, is highly important (Weritz et al., 2006). For the 2D evaluation, the expectation-maximizationalgorithm (EM algorithm; Ester and Sander, 2000) has been tested for the application presented in this work. The method has been introduced and different figures of merit have been presented according to recommendations given in Haddad et al. (2014). Advantages of this method will be highlighted. After phase separation, non-relevant information can be excluded and only the wanted phase displayed. Using a set of samples with known and unknown composition, the EM-clustering method has been validated regarding to Gustavo González and Ángeles Herrador (2007). KW - LIBS KW - Concrete KW - EM-clustering KW - Heterogeneity PY - 2017 DO - https://doi.org/10.1016/j.sab.2017.06.005 SN - 0584-8547 VL - 2017 IS - 134 SP - 58 EP - 68 PB - Elsevier B.V. AN - OPUS4-40644 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Miccoli, Lorenzo A1 - Gerrard, C. A1 - Perrone, C. A1 - Gardei, André A1 - Ziegert, C. T1 - A collaborative engineering and archaeology project to investigate decay in historic rammed earth structures: The case of the Medieval preceptory in Ambel JF - International Journal of Architectural Heritage N2 - This study assesses the structural vulnerability of part of a later medieval earthen building at Ambel (near Zaragoza, Spain), once a preceptory or monastic house belonging to the Military Orders. An inspection of its morphology and materials coupled with the results of an extensive campaign of static monitoring reveals marked structural inhomogeneities, the product of more than a thousand years of construction, failure, and repair from the 10th century to the present day. Building materials are inappropriately juxtaposed, there are discontinuities between construction phases and fundamental concerns remain over the long-term stability of the structure. The current condition of the structure is mainly influenced by structural discontinuities introduced at the time of construction, the unintended consequences of repair and modification and the material decay that has affected the base of the rammed earth walls. The overall findings of the static monitoring show that there is no related damage, variations in crack widths are related to the building seasonal cycle. While static analysis is an essential prerequisite before a suitable maintenance program can be fully defined, this study argues that no evaluation of the structural behavior of any historic building can afford to ignore its archaeological “biography” of modification and repair. KW - Archaeology KW - Historical earthen building KW - Materials characterization KW - Rammed earth KW - Static monitoring PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-396274 DO - https://doi.org/10.1080/15583058.2016.1277283 VL - 11 IS - 5 SP - 636 EP - 655 PB - Taylor & Francis Group AN - OPUS4-39627 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hentrich, D. A1 - Taabache, Soraya A1 - Brezesinski, G. A1 - Lange, Nele A1 - Unger, Wolfgang A1 - Kübel, C. A1 - Bertin, Annabelle A1 - Taubert, A. T1 - A dendritic amphiphile for efficient control of biomimetic calcium phosphate mineralization JF - Macromolecular Bioscience N2 - The phase behavior of a dendritic amphiphile containing a Newkome-type dendron as the hydrophilic moiety and a cholesterol unit as the hydrophobic segment is investigated at the air–liquid interface. The amphiphile forms stable monomolecular films at the air–liquid interface on different subphases. Furthermore, the mineralization of calcium Phosphate beneath the monolayer at different calcium and phosphate concentrations versus mineralization time shows that at low calcium and Phosphate concentrations needles form, whereas flakes and spheres dominate at higher concentrations. Energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electron diffraction confirm the formation of calcium phosphate. High-resolution transmission electron microscopy and electron diffraction confirm the predominant formation of octacalcium phosphate and hydroxyapatite. The data also indicate that the final products form via a complex multistep reaction, including an association step, where nano-needles aggregate into larger flake-like objects. KW - Dendritic amphiphile KW - Calcium phosphate KW - Biomineralization PY - 2017 DO - https://doi.org/10.1002/mabi.201600524 SN - 1616-5187 SN - 1616-5195 VL - 17 IS - 8 SP - Article 1600524, 1 EP - 14 AN - OPUS4-41825 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ho, Y.T. A1 - Adriani, G A1 - Beyer, Sebastian A1 - Nhan, P.-T. A1 - Kamm, R. D. A1 - Kah, J.C.Y. T1 - A facile method to probe the vascular permeability of nanoparticles in nanomedicine applications JF - Nature Scientific Reports N2 - The effectiveness of nanoparticles (NP) in nanomedicine depends on their ability to extravasate from vasculature towards the target tissue. This is determined by their permeability across the endothelial barrier. Unfortunately, a quantitative study of the diffusion permeability coefficients (Pd) of NPs is difficult with in vivo models. Here, we utilize a relevant model of vascular-tissue interface with tunable endothelial permeability in vitro based on microfluidics. Human umbilical vein endothelial cells (HUVECs) grown in microfluidic devices were treated with Angiopoietin 1 and cyclic adenosine monophosphate (cAMP) to vary the Pd of the HUVECs monolayer towards fluorescent polystyrene NPs (pNPs) of different sizes, which was determined from image analysis of their fluorescence intensity when diffusing across the monolayer. Using 70 kDa dextran as a probe, untreated HUVECs yielded a Pd that approximated tumor vasculature while HUVECs treated with 25 μg/mL cAMP had Pd that approximated healthy vasculature in vivo. As the size of pNPs increased, its Pd decreased in tumor vasculature, but remained largely unchanged in healthy vasculature, demonstrating a trend similar to tumor selectivity for smaller NPs. This microfluidic model of vascular-tissue interface can be used in any laboratory to perform quantitative assessment of the tumor selectivity of nanomedicine-based systems. KW - Nanoparticle PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-397053 DO - https://doi.org/10.1038/s41598-017-00750-3 SN - 2045-2322 VL - 7 IS - 1 SP - Article 707, 1 EP - 13 PB - Macmillan AN - OPUS4-39705 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Unger, Jörg F. A1 - Kindrachuk, Vitaliy T1 - A Fourier transformation-based temporal integration scheme for viscoplastic solids subjected to fatigue deterioration JF - International Journal of Fatigue N2 - Using continuum damage mechanics (CDM) for lifetime prediction requires numerical integration of evolving damage until the onset of failure. The primary challenge for the simulation of structural fatigue failure is caused by the enormous computational costs due to cycle-by-cycle temporal integration throughout the whole loading history, which is in the order of 103–107 cycles. As a consequence, most approaches circumvent this problem and use empirical methods such as Wöhler curves. They are well suited for approximating the lifetime, but they are not capable to capture a realistic degradation of the material including redistribution of stresses. The main objective of the paper is to provide a technique for finite element (FE) simulations of structures under fatigue loading while reducing computational costs. A Fourier transformation-based temporal integration (FTTI) scheme is proposed, which adapts the conventional FE method for modeling the viscoplastic deterioration in a structure subjected to cyclic loading. The response fields are represented by a Fourier series which assumes a temporal scale separation: a microchronological (short time) scale arises from the oscillatory loading and a macrochronological (long time) scale is due to the slow material relaxation resulting from yielding and damage evolution. The original dynamic boundary value problem (BVP) is approximated by the stationary BVP on the microchronological scale. Alternation of the displacement field on the macrochronological scale is correlated with evolution of the history variables by means of a high order adaptive cycle jump method. Performance and significant acceleration of the FE simulations is demonstrated at different loading scenarios for a constitutive damage model where the progressive damage accumulation is driven by viscoplastic yielding. KW - Fatigue KW - Accelerated time integration KW - Continuum damage mechanics KW - Fourier series PY - 2017 DO - https://doi.org/10.1016/j.ijfatigue.2017.03.015 SN - 0142-1123 SN - 1879-3452 VL - 100 IS - 1 SP - 215 EP - 228 PB - Elsevier Ltd. AN - OPUS4-39616 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Daly, M. A1 - Burnett, T. L. A1 - Pickering, E. J. A1 - Tuck, O. C. G. A1 - Léonard, Fabien A1 - Kelley, R. A1 - Withers, P. J. A1 - Sherry, A. H. T1 - A multi-scale correlative investigation of ductile fracture JF - Acta Materialia N2 - The use of novel multi-scale correlative methods, which involve the coordinated characterisation of matter across a range of length scales, are becoming of increasing value to materials scientists. Here, we describe for the first time how a multi-scale correlative approach can be used to investigate the nature of ductile fracture in metals. Specimens of a nuclear pressure vessel steel, SA508 Grade 3, are examined following ductile fracture using medium and high-resolution 3D X-ray computed tomography (CT) analyses, and a site-specific analysis using a dual beam plasma focused ion beam scanning electron microscope (PFIB-SEM). The methods are employed sequentially to characterise damage by void nucleation and growth in one volume of interest, allowing for the imaging of voids that ranged in size from less than 100 nm to over 100 mm. This enables the examination of voids initiated at carbide particles to be detected, as well as the large voids initiated at inclusions. We demonstrate that this multi-scale correlative approach is a powerful tool, which not only enhances our understanding of ductile failure through detailed characterisation of microstructure, but also provides quantitative information about the size, volume fractions and spatial distributions of voids that can be used to inform models of failure. It isfound that the vast majority of large voids nucleated at MnS inclusions, and that the volume of a void varied according to the volume of its initiating inclusion raised to the power 3/2. The most severe voiding was concentrated within 500 mm of the fracture surface, but measurable damage was found to extend to a depth of at least 3 mm. Microvoids associated with carbides (carbide-initiated voids) were found to be concentrated around larger inclusion-initiated voids at depths of at least 400 mm. Methods for quantifying X-ray CT void data are discussed, and a procedure for using this data to calibrate parameters in the Gurson-Tvergaard Needleman (GTN) model for ductile failure is also introduced. KW - Gurson model KW - SA508 KW - Correlative tomography KW - Void nucleation & growth KW - X-ray computed tomography PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-414547 UR - http://www.sciencedirect.com/science/article/pii/S1359645417302203?via%3Dihub DO - https://doi.org/10.1016/j.actamat.2017.03.028 VL - 130 SP - 56 EP - 68 PB - Elsevier AN - OPUS4-41454 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Huang, K. A1 - Liu, H. A1 - Kraft, Marco A1 - Shikha, S. A1 - Zheng, X. A1 - Agren, H. A1 - Würth, Christian A1 - Resch-Genger, Ute A1 - Zhang, Y. T1 - A protected excitation-energy reservoir for efficient upconversion luminescence JF - Nanoscale N2 - Lanthanide-doped upconversion nanoparticles (UCNPs) are of great interest for biomedical applications. Currently, the applicability of UCNP bionanotechnology is hampered by the generally low luminescence intensity of UCNPs and inefficient energy Transfer from UCNPs to surface-bound chromophores used e.g. for photodynamic therapy or analyte sensing. In this work, we address the low-Efficiency issue by developing versatile core-Shell nanostructures, where high-concentration sensitizers and activators are confined in the core and Shell Region of representative hexagonal NaYF2:Yb,Er UCNPs. After Doping concentration optimization, the sensitizer-rich core is able to harvest/accumulate more excitation energy and generate almost one order of Magnitude higher luminescence intesity than conventional homogeneously doped nanostructures. At the same time, the activator Ions located in the Shell enable a ~6 times more efficient resonant energy Transfer from UCNPs to surface-bound acceptor dye molecules due to the short distance between donor-acceptor pairs. Our work provides new insights into the rational design of UCNPs and will greatly encrease the General applicability of upconversion nanotechnologies. KW - Fluorescence KW - Lanthanide KW - Upconversion KW - Brightness KW - Quantification KW - Nanoparticle KW - Absolute fluorometry KW - NIR KW - IR KW - Quantum yield KW - Integrating sphere spectroscopy KW - Method KW - Energy transfer KW - Shell KW - Particle architecture PY - 2017 DO - https://doi.org/10.1039/c7nr06900f SN - 2040-3372 SN - 2040-3364 VL - 10 IS - 1 SP - 250 EP - 259 PB - The Royal Society of Chemistry AN - OPUS4-43893 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wu, C. A1 - Schwibbert, Karin A1 - Achazi, K. A1 - Landsberger, Petra A1 - Gorbushina, Anna A1 - Haag, R. T1 - Active antibacterial and antifouling surface coating via a facile one-step enzymatic cross-linking JF - Biomacromolecules N2 - Prevention of microbial contamination of surfaces is one of the biggest challenges for biomedical applications. Establishing a stable, easily produced, highly antibacterial surface coating offers an efficient solution but remains a technical difficulty. Here, we report on a new approach to create an in situ hydrogel film-coating on glass surfaces made by enzymatic cross-linking under physiological conditions. The cross-linking is catalyzed by horseradish peroxidase (HRP)/glucose oxidase (GOD)-coupled cascade reactions in the presence of glucose and results in 3D dendritic polyglycerol (dPG) scaffolds bound to the surface of glass. These scaffolds continuously release H2O2 as long as glucose is present in the system. The resultant polymeric coating is highly stable, bacterial-repellent, and functions under physiological conditions. Challenged with high loads of bacteria (OD540 = 1.0), this novel hydrogel and glucose-amended coating reduced the cell viability of Pseudomonas putida (Gram-negative) by 100% and Staphylococcus aureus (Gram-positive) by ≥40%, respectively. Moreover, glucose-stimulated production of H2O2 by the coating system was sufficient to kill both test bacteria (at low titers) with >99.99% Efficiency within 24 h. In the presence of glucose, this platform produces a coating with high effectiveness against bacterial adhesion and survival that can be envisioned for the applications in the glucose-associated medical/oral devices. KW - Antifouling KW - Surface coating KW - Biofilm KW - Bacterial adhesion PY - 2017 DO - https://doi.org/10.1021/acs.biomac.6b01527 SN - 1525-7797 SN - 1526-4602 VL - 18 IS - 1 SP - 210 EP - 216 AN - OPUS4-39003 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Homberg, U. A1 - Baum, D. A1 - Prohaska, S. A1 - Günster, Jens A1 - Krauss-Schüler, Stefanie T1 - Adapting trabecular structures for 3D printing: an image processing approach based on μCT data JF - Biomedical Physics and Engineering Express N2 - Materials with a trabecular structure notably Combine advantages such as lightweight, reasonable strength, and permeability for fl uids. This combination of advantages is especially interesting for tissue engineering in trauma surgery and orthopedics. Bone-substituting scaffolds for instance are designed with a trabecular structure in order to allow cell migration for bone ingrowth and vascularization. An emerging and recently very popular technology to produce such complex, porous structures is 3D printing. However, several technological aspects regarding the scaffold architecture, the printable resolution, and the feature size have to be considered when fabricating scaffolds for bone tissue replacement and regeneration. Here, we present a strategy to assess and prepare realistic trabecular structures for 3D printing using image analysis with the aim of preserving the structural elements. We discuss critical conditions of the printing system and present a 3-stage approach to adapt a trabecular structure from μ CT data while incorporating knowledge about the printing system. In the first stage, an image-based extraction of solid and void structures is performed, which results in voxel- and graph-based representations of the extracted structures. These representations not only allow us to quantify geometrical properties such as pore size or strut geometry and length. But, since the graph represents the geometry and the topology of the initial structure, it can be used in the second stage to modify and adjust feature size, volume and sample size in an easy and consistent way. In the final reconstruction stage, the graph is then converted into a voxel representation preserving the topology of the initial structure. This stage generates a model with respect to the printing conditions to ensure a stable and controlled voxel placement during the printing process. KW - Additive manufacturing, 3D printing KW - Trabecular structures KW - Image-based analysis PY - 2017 DO - https://doi.org/10.1088/2057-1976/aa7611 SN - 2057-1976 VL - 3 IS - 3 SP - Article 035027, 1 EP - 14 PB - IOP Publishing Ltd AN - OPUS4-40744 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Colombo, P. A1 - Schmidt, J. A1 - Franchin, G. A1 - Zocca, Andrea A1 - Günster, Jens T1 - Additive manufacturing techniques for fabricating complex ceramic components from preceramic polymers JF - American Ceramic Society Bulletin N2 - Capsule summary THE MATERIALS Manufacturers can use preceramic polymers to produce ceramic components in a range of compositions using a variety of additive manufacturing technologies. Preceramic polymers even can overcome some of the problems that are intrinsic to additive manufacturing in general. THE APPLICATION Modifying the composition, molecular architecture, and molecular weight of preceramic polymers allows adaptation of these materials to specific processing requirements of individual additive manufacturing technologies. THE OPPORTUNITY Further development of new additive manufacturing technologies, in addition to improvement of existing technologies, will enable manufacturing of advanced ceramic components with enhanced mechanical characteristics and new functional properties. KW - Additive manufacturing KW - Preceramic polymers PY - 2017 VL - 96 IS - 3 SP - 16 EP - 23 AN - OPUS4-40747 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pasternak, H. A1 - Launert, B. A1 - Kannengießer, Thomas A1 - Rhode, Michael T1 - Advanced residual stress assessment of plate girders through welding simulation JF - Procedia Engineering / Modern Building Materials, Structures and Techniques N2 - This article provides an impression on potentials in applying nowadays welding simulation tools in construction design. This is carried out exemplary on plate girders from two structural steel grades. The calculated residual stresses are compared with measurements by sectioning method. It has been repeatedly stated that present Eurocode models fail to approximate the residual stresses. Especially for high strength steel (HSS) only limited information is available on realistic occurring residual stresses in typical I-girders. The investigations are aimed to give further guidance on these values. A few proposals on advanced models are discussed. T2 - MBST 2016 - Modern Building Materials, Structures and Techniques CY - Vilnius, Litunia DA - 26.05.2016 KW - Residual stresses KW - Plate girders KW - I-shape sections KW - High-strength steel KW - Welding simulation PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-392177 UR - http://www.sciencedirect.com/science/article/pii/S1877705817305192 DO - https://doi.org/10.1016/j.proeng.2017.02.013 SN - 1877-7058 IS - 172 SP - 23 EP - 30 PB - Elsevier CY - Amsterdam, Niederlande AN - OPUS4-39217 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Giebson, C. A1 - Voland, K. A1 - Ludwig, H.-M. A1 - Meng, Birgit T1 - Alkali-silica reaction performance testing of concrete considering external alkalis and preexisting microcrack JF - Structural Concrete N2 - In concrete elements, simultaneously subjected to cyclic loadings and external alkalis, the risk for damage caused by or under participation of an alkali-silica reaction (ASR) is particularly high. This is of particular concern for concrete pavements due to the increasing heavy vehicle traffic and the application of sodium chloride (NaCl) de-icer during winter. Since 2004, the climate simulation concrete prism test (CS-CPT) has been used successfully to evaluate job mixtures for pavements by considering the impact of alkali-containing de-icers. However, the role of mechanical predamage on ASR is largely unclear. In a joint research project, the CS-CPT has been used to investigate the influence of preexisting microcracks on ASR. It was evident that an ASR initiated earlier in the predamaged concrete prisms due to the more rapid ingress of NaCl solution through the microcracks. KW - Alkali-silica reaction KW - Climate simulation concrete prism test KW - External alkalis KW - Laser-induced breakdown spectroscopy KW - Microcracks KW - Pavement concrete PY - 2017 DO - https://doi.org/10.1002/suco.201600173 SN - 1464-4177 SN - 1751-7648 VL - 18 IS - 4 SP - 528 EP - 538 PB - Ernst & Sohn AN - OPUS4-42574 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Cabeza, Sandra A1 - Artzt, Katia A1 - Haubrich, J. A1 - Klaus, M. A1 - Genzel, Ch. A1 - Requena, G. A1 - Bruno, Giovanni T1 - An Assessment of Subsurface Residual Stress Analysis in SLM Ti-6Al-4V JF - Materials N2 - Ti-6Al-4V bridges were additively fabricated by selective laser melting (SLM) under different scanning speed conditions, to compare the effect of process energy density on the residual stress state. Subsurface lattice strain characterization was conducted by means of synchrotron diffraction in energy dispersive mode. High tensile strain gradients were found at the frontal surface for samples in an as-built condition. The geometry of the samples promotes increasing strains towards the pillar of the bridges. We observed that the higher the laser energy density during fabrication, the lower the lattice strains. A relief of lattice strains takes place after heat treatment. KW - Selective laser melting KW - Additive manufacturing KW - Heat treatment KW - Ti-6Al-4V KW - Synchrotron X-ray diffraction KW - Residual stress PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-395759 DO - https://doi.org/10.3390/ma10040348 SN - 1996-1944 VL - 10 IS - 4 SP - Article 348, 1 EP - 14 AN - OPUS4-39575 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhou, Peng A1 - Ogle, Kevin A1 - Erning, Johann Wilhelm A1 - Hutchinson, Michael John A1 - Scully, John T1 - An in situ kinetic study of brass dezincification and corrosion JF - Electrochimica Acta N2 - The kinetics of the anodic dissolution of brass (CuZn42 and CuZn21Si3P) in synthetic tap water were investigated by atomic emission spectroelectrochemistry. Elemental Cu and Zn dissolution rates were measured in situ and in real time during galvanostatic dissolution. A complete mass/charge balance for the system yielded, as a function of applied current and a function of time, the quantity of Cu in the dezincification layer and the quantity of Cu and Zn in the oxide layer. In this way, a complete kinetic characterization of the fundamental chemical processes occurring during dezincification was realized for the first time. The oxide layer was composed primarily of Cu2O as indicated by grazing incidence XRD and Raman analysis. The soluble Cu oxidation product was determined to be Cu(II) by a mass/charge balance. Zn was oxidized to soluble Zn(II) leaving behind a trivial amount of solid Zn corrosion product on the surface. The kinetic analysis depicts a two-stage dissolution process of dezincification: a first stage of a rapid growth of the dezincified layer and a second stage where the growth of dezincified layer was much slower. The Cu2O layer grows continually during the exposure. KW - Dezincification KW - Spectroelectrochemistry KW - Brass PY - 2017 DO - https://doi.org/10.1016/j.electacta.2017.01.078 SN - 0013-4686 SN - 1873-3859 VL - 229 SP - 141 EP - 154 PB - Elsevier AN - OPUS4-39164 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Engl, T. A1 - Eberl, N. A1 - Gorse, C. A1 - Krüger, T. A1 - Schmidt, T. A1 - Plarre, Rüdiger A1 - Adler, C. A1 - Kaltenpoth, M. T1 - Ancient symbiosis confers desiccation resistance to stored grain pest beetles JF - Molecular Ecology N2 - Microbial symbionts of insects provide a range of ecological traits to their hosts that are beneficial in the context of biotic interactions. However, little is known about insect symbiont-mediated adaptation to the abiotic environment, for example, temperature and humidity. Here, we report on an ancient clade of intracellular, bacteriome-located Bacteroidetes symbionts that are associated with grain and Wood pest beetles of the phylogenetically distant families Silvanidae and Bostrichidae. In the saw-toothed grain beetle Oryzaephilus surinamensis, we demonstrate that the symbionts affect cuticle thickness, melanization and hydrocarbon profile, enhancing desiccation resistance and thereby strongly improving fitness under dry conditions. Together with earlier observations on Symbiont contributions to cuticle biosynthesis in weevils, our findings indicate that convergent acquisitions of bacterial mutualists represented key adaptations enabling diverse pest beetle groups to survive and proliferate under the low ambient humidity that characterizes dry grain storage facilities. KW - Bacteroidetes KW - Cuticle KW - Desiccation resistance KW - Grain pest beetles KW - Symbiosis PY - 2017 DO - https://doi.org/10.1111/mec.14418 SN - 1365-294X SN - 0962-1083 VL - 27 IS - 8 SP - 2095 EP - 2108 AN - OPUS4-44013 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Marko, A. A1 - Graf, B. A1 - Gook, S. A1 - Rethmeier, Michael T1 - Application of D-optimum experimental designs in consideration of restrictions for laser metal deposition JF - Global Nuclear Safety N2 - The process of laser metal deposition can be applied in many ways. Mostly, it is relevant to coating, for repair welding and for additive manufacturing. To increase the effectiveness and the productiveness, a good process understanding is necessary. Statistical test planning is effectual and often used for this purpose. For financial and temporal reasons, a restriction of the test space is reasonable. In this case, it is recommended to use a D-optimal experimental design which is practically applied to extend existing test plans or if process Limits are known. This paper investigates the applicability of a D-optimum experimental design for the laser metal deposition. The results are compared to the current results of a full factorial test plan. Known restrictions are used for the limitation of the test space. Ti6Al4 is utilized as Substrate material and powder. Comparable results of the D-optimal experimental design and of the full factorial test plan can be demonstrated. However, 80 % of time can be saved by the experimental procedure. For this reason, the application of D-optimal experimental design for laser metal deposition is recommend. KW - Design of experiments KW - Repair welding KW - Additive manufacturing KW - Cladding parameter KW - Laser metal deposition KW - Laser cladding PY - 2017 SN - 2499-9733 SN - 2305-414Х VL - 3 IS - 24 SP - 46 EP - 60 AN - OPUS4-44344 LA - rus AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schumacher, David A1 - Antin, K.-N. A1 - Zscherpel, Uwe A1 - Vilaça, P. T1 - Application of different X-ray techniques to improve in-service carbon fiber reinforced rope inspection JF - Journal of Nondestructive Evaluation N2 - Carbon fiber reinforced polymer ropes are gaining in significance in the fields of civil engineering and hoisting applications. Thus, methods of non-destructive testing (NDT) need to be developed and evaluated with respect to new challenges and types of defects. Particularly important is the development of in-service testing solutions which allow the integration in global online monitoring systems. Conventional methods like electrical resistivity or strain measurements using optical fibers are already in use. This study investigates the possibility of using various X-ray techniques to increase the reliability and significance of NDT and their applicability to in-service testing. Conventional film radiography is the most common technique; however, even after image enhancement of the digitized film, this technique lacks contrast sensitivity and dynamic range compared to digital detector array (DDA) radiography. The DDA radiography is a highly sensitive method; yet, the limitation is that it delivers 2D images of 3D objects. By the use of co-planar translational laminography the detectability of planar defects is superior to 2D methods due to multiple projection angles. Apart from this, it can be used on-site due to a rather simple setup and robust equipment. In this work two photon counting detectors (PCD) with different sensor materials (Si and CdTe) were used. The results show that the resolution and defect recognition is lower in case of DDA radiography and laminography using PCDs compared to high-resolution computed tomography. However, the DDA radiography and laminography are sensitive enough to both fiber breakage and delaminations and can be significantly advantageous in terms of measurement time and adaptability for on-site monitoring. KW - X-ray imaging KW - Digital radiography KW - Co-planar translational laminography KW - Computed tomography KW - Photon counting detectors KW - Carbon fiber reinforced polymer KW - Rope PY - 2017 DO - https://doi.org/10.1007/s10921-017-0441-5 SN - 0195-9298 SN - 1573-4862 VL - 36 IS - 4 SP - Paper 62, 1 PB - Springer International Publishing AG CY - Cham, Switzerland AN - OPUS4-41781 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Martynenko, Irina A1 - Litvin, A.P. A1 - Purcell-Milton, F. A1 - Baranov, A. V. A1 - Fedorov, A.V. A1 - Gun´ko, Y.K. T1 - Application of semiconductor quantum dots in bioimaging and biosensing JF - Journal of Materials Chemistry B N2 - In this review we present new concepts and recent progress in the application of semiconductur quantum dots (QD) as labels in two important areas of biology, bioimaging and biosensing. We analyze the biologically relevant properties of QDs focusing on the following topics: QD surface treatment and stability labeling of cellular structures and receptors with QDs, incorporation of QDs in living cells, cytotoxicity of QDs and influence of the biolocical environment on the biological and optical properties of QDs. Initially, we consider utilization of QDs as agants in high-resolution bioimaging techniques that can provide information at the molecular levels. The deverse range of modern live-cell QD-based imaging techniques with resolution far beyond the diffraction limit of light is examined. In each technique, we discuss the pros and cons of QD use and deliberate how QDs can be further engineered to facilitate their application in the respective imaging techniques and to produce significant improvements in resolution. Then we review QD-based point-of-care bioassays, bioprobes, and biosensors designed in different formats ranging from analytic biochemistry assays and ELISA, to novel point-of-care smartphone integrated QD-based biotests. Here, a wide range of QD-based fluorescence bioassays with optical transduction, electrochemiluminescence and photoelectrochemical assays are discussedc. Finally, this review provides an analysis of the prospects of application of QDs in selected important Areas of biology. KW - Fluorescence KW - Semiconductor quantum dot KW - Imaging KW - Quantification KW - Nanoparticle KW - NIR KW - IR KW - Quantum yield KW - Method KW - Microscopy KW - Assay KW - Bioconjugate PY - 2017 DO - https://doi.org/10.1039/c7tb01425b VL - 5 IS - 33 SP - 6701 EP - 6727 PB - Royal Society of Chemistry AN - OPUS4-43027 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wu, Cheng-Chieh A1 - Weisbrich, S. A1 - Neitzel, F. ED - Emri, Igor T1 - Approximate model for geometrical complex structures JF - Materials Today: Proceedings N2 - Many engineering structures are nowadays made of composite materials or metal foam. These modern engineering materials contain very complex inner geometry. To simulate the deformational behaviour of these structures often requires a high number of discretisation elements. This in turn yields a very large system of linear equations that are extremely time and memory consuming or practically impossible to solve. It is therefore desirable to find an approach to overcome this obstacle. In this paper a numerical method is proposed to find an approximate substitute model for geometrical complex structures. T2 - 33rd Danubia Adria Symposium on Advances in Experimental Mechanics CY - Portorož, Slovenia DA - 20.09.2016 KW - Adjustment calculation KW - Finite element method KW - Substitute model KW - Complex structures PY - 2017 UR - http://www.sciencedirect.com/science/article/pii/S2214785317308593 DO - https://doi.org/10.1016/j.matpr.2017.06.084 SN - 2214-7853 VL - 4 IS - 5, Part 1 SP - 5995 EP - 6000 PB - Elsevier CY - Amsterdam, Netherlands AN - OPUS4-42794 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madia, Mauro A1 - Zerbst, Uwe A1 - Beier, T. A1 - Tchoffo Ngoula, D. T1 - Approximation of the crack driving force for cracks at notches under static and cyclic loading JF - Procedia Structural Integrity N2 - The work deals with the efficient calculation of the elastic-plastic crack driving force (J-integral for monotonic loading andΔJ-integral under cyclic loading) for short cracks at notches as essential parameter for the reliable static and fatigue assessment of notched structures. The J- or ΔJ-integral is calculated based on analytical solutions for stress intensity factors, estimated by means of well-known weight function solutions in the case of cracks under power-law stress distributions. A plasticity-correction function is applied to the stress intensity factors to obtain the final expression of the crack driving force. The comparison between analytical solutions and finite element calculations in case of cracks at the weld toe in welded joints shows good agreement. T2 - 2nd International Conference on Structural Integrity CY - Funchal, Madeira, Portugal DA - 04.09.2017 KW - Structural integrity KW - Fracture mechanics KW - Crack driving force KW - Notches PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-425577 DO - https://doi.org/10.1016/j.prostr.2017.07.111 SN - 2452-3216 VL - 5 SP - 875 EP - 882 PB - Elsevier B.V. AN - OPUS4-42557 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ward, H. A1 - Burger, M. A1 - Chang, Y.-J. A1 - Fürstmann, P. A1 - Neugebauer, S. A1 - Radebach, A. A1 - Sproesser, G. A1 - Pittner, Andreas A1 - Rethmeier, Michael A1 - Uhlmann, E. A1 - Steckel, J. Ch. T1 - Assessing carbon dioxide emission reduction potentials of improved manufacturing processes using multiregional input output frameworks JF - Journal of Cleaner Production N2 - Evaluating innovative process technologies has become highly important within the last decades. As standard tools different Life Cycle Assessment methods have been established, which are continuously improved. While those are designed for evaluating single processes they run into difficulties when it comes to assessing environmental impacts of process innovations at macroeconomic level. In this paper we develop a multi-step evaluation framework building on multi regional inputeoutput data that allows estimating macroeconomic impacts of new process technologies, considering the network characteristics of the global economy. Our procedure is as follows: i) we measure differences in material usage of process alternatives, ii) we identify where the standard processes are located within economic networks and virtually replace those by innovative process technologies, iii) we account for changes within economic systems and evaluate impacts on emissions. Within this paper we exemplarily apply the methodology to two recently developed innovative technologies: longitudinal large diameter steel pipe welding and turning of high-temperature resistant materials. While we find the macroeconomic impacts of very specific process innovations to be small, its conclusions can significantly differ from traditional process based approaches. Furthermore, information gained from the methodology provides relevant additional insights for decision makers extending the picture gained from traditional process life cycle assessment. KW - Economic wide technology replacement KW - Sustainability assessment KW - Multi-regional inputeoutput data KW - Life-cycle assessment KW - Greenhouse gas mitigation KW - Process innovations PY - 2017 DO - https://doi.org/10.1016/j.jclepro.2016.02.062 SN - 0959-6526 SN - 1879-1786 VL - 163 SP - 154 EP - 165 PB - Elsevier Ltd. AN - OPUS4-41356 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weltschev, Margit T1 - Auswahl eines Kennwertes für den Vergleich des mechanischen Leistungsniveaus von Polyethylenformstoffen für Gefahrgutverpackungen T1 - Parameter selection for the comparison of the mechanical level of performance of polyethylene molding materials for packagings of dangerous goods JF - Materials Testing N2 - Zum Vergleich der Polyethylenformstoffe für eine Bauart von Gefahrgutverpackungen und IBC wurden die Materialkennwerte: Schmelze-Massefließrate MFR, Dichte D, Kerbschlag-zähigkeit acN bei -30 °C, Spannungsrissbeständigkeit (bestimmt mit dem Full Notch Creep Test) und Beständigkeit gegen oxidativen Abbau Ox (bestimmt durch den prozentualen Anstieg des MFR in Salpetersäure) in der DIN EN 15507 – Verpackung – Verpackungen zur Beförderung gefährlicher Güter – Vergleichende Werkstoffprüfung von Polyethylensorten ausgewählt. Das Ziel der Untersuchungen war die Auswahl eines Kennwertes für die Bestimmung des mechanischen Leistungsniveaus von Polyethylenformstoffen, da unter Druck Verpackungen beulen oder knicken. Zur Auswahl standen drei Prüfverfahren: a) Bestimmung der Biegesteifigkeit S nach DIN 53 350 (Prinzip von Ohlsen). b) Bestimmung der Biegefestigkeit σfM und Biegedehnung ɛfM nach DIN EN ISO 178 c) Bestimmung der Druckkraft Fmax und Verformung dL bei Fmax nach DIN EN ISO 604. Die Prüfmethode zur Bestimmung der Biegesteifigkeit nach DIN 53 350 eignet sich zum Vergleich des mechanischen Leistungsniveaus der Formstoffe. Zur Verbesserung der Reproduzierbarkeit der Ergebnisse sollte der Skalierungsbereich der Prüfapparatur erweitert wer-den, um genauere Messergebnisse zu erzielen. Der Dreipunktbiegeversuch nach DIN EN ISO 178 eignet sich bei verformungsfähigen Kunststoffen, wie dem Polyethylen, zur Bestimmung der Biegefestigkeit σfM. Dieser Ver-such besitzt den Nachteil, dass am Ort des maximalen Biegemoments in der Randschicht, wo auch die maximale Biegespannung erzeugt wird, zusätzlich der Biegestempel angreift. Die Messergebnisse haben gezeigt, dass die Druckprüfung nach DIN EN ISO 604 sich sehr gut zur Bewertung des mechanischen Verhaltens der Polyethylenformstoffe unter Druckbelastung (Stapeldruckprüfung der Verpackungen) eignet. KW - Gefahrgutverpackung KW - Polyethylen KW - Biegesteifigkeit KW - Biegefestigkeit KW - Druckkraft PY - 2017 DO - https://doi.org/10.3139/120.111025 SN - 0025-5300 VL - 59 IS - 5 SP - 466 EP - 471 PB - Carl Hanser Verlag GmbH & Co.KG CY - München AN - OPUS4-40145 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kropidlowski, K. A1 - Uhlmann, E. A1 - Woydt, Mathias T1 - Außen-Längs-Runddrehen mit Niobcarbid-Schneidstoff JF - WB Werkstoff + Betrieb N2 - Als Alternative zu Wolframcarbid wird zurzeit Niobcarbid beim Drehen unter extremen Bedingungen untersucht, vorerst ohne Beschichtungen und ohne Kühlschmierstoffe. Aufgrund seiner besonderen Eigenschaften zeigt Niobcarbid als Schneidstoff ein großes Potenzial. KW - Niobcarbid KW - Drehen KW - Schneidstoff PY - 2017 IS - 7-8 SP - 58 EP - 61 PB - Carl Hanser CY - München AN - OPUS4-41129 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Resch-Genger, Ute ED - Mousavi, M. ED - Thomasson, B. ED - Li, M. ED - Kraft, Marco ED - Würth, Christian ED - Andersson-Engels, S. T1 - Beam-profile-compensated quantum yield measurements of upconverting nanoparticles JF - Physical chemistry, chemical physics (PCCP) N2 - The quantum yield is a critically important parameter in the development of lanthanide-based upconverting nanoparticles (UCNPs) for use as novel contrast agents in biological imaging and optical reporters in assays. The present work focuses on the influence of the beam Profile in measuring the quantum yield (f) of nonscattering dispersions of nonlinear upconverting probes, by establishing a relation between f and excitation light power density from a rate equation analysis. A resulting 60% correction in the measured f due to the beam profile utilized for excitation underlines the significance of the beam profile in such measurements, and its impact when comparing results from different Setups and groups across the world. KW - Fluorescence KW - Lanthanide KW - Upconversion KW - Brithtness KW - Quantification KW - Nanoparticle KW - Absolute fluoreometry KW - NIR KW - IR KW - Quantum yield KW - Integrating sphere spectroscopy KW - Method PY - 2017 DO - https://doi.org/10.1039/c7cp03785f SN - 1463-9076 SN - 1463-9084 VL - 19 IS - 33 SP - 22016 EP - 22022 PB - Royal Society of Chemistry AN - OPUS4-42583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Radunz, Sebastian A1 - Tschiche, Harald Rune A1 - Moldenhauer, Daniel A1 - Resch-Genger, Ute T1 - Broad range ON/OFF pH sensors based on pKa tunable fluorescent BODIPYs JF - Sensors and Actuators B:Chemical N2 - A set of highly fluorescent, pH-responsive boron dipyrromethene dyes covering the pH range of 5-12 is presented for broad range pH measurements in mixed aqueous-organic median and polymer matrices. Readout in the intensity Domain with low cost and miniaturized Instrumentation utilizes reversible protonation induced switching ON of their initially completely quenched flourescence mediated by photoinduced electron Transfer. All dyes, rationally designed to reveal closely matching Absorption and Emission properties, are accessible via facile two-step reactions in Overall yields of up to 20%. By modifying the Substitution pattern of the meso-Aryl substiuent, the pKa values could be fine-tuned from 6 to 11. Integration of these molecules into polymeric films by a simple mixing procedure yielded reversible and longterm stable pH sensors for naked eye detection. KW - Fluorescence KW - Sensor KW - PH KW - Dye KW - BODIPY KW - Synthesis KW - Quantification KW - Film KW - Quantum yield KW - Lifetime KW - PET PY - 2017 DO - https://doi.org/10.1016/j.snb.2017.05.080 SN - 0925-4005 VL - 251 SP - 490 EP - 494 PB - Elsevier AN - OPUS4-41782 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Al-Terkawi, Abdal-Azim A1 - Scholz, G. A1 - de Oliveira Guilherme Buzanich, Ana A1 - Reinsch, Stefan A1 - Kemnitz, E. A1 - Emmerling, Franziska T1 - Ca- and Sr- tetrafluoroisophthalates: mechanochemical synthesis, characterization, and ab initio structure determination JF - DALTON TRANSACTIONS N2 - New fluorinated coordination polymers were prepared mechanochemically by milling the alkaline earth metal hydroxides MII(OH)2·xH2O (MII: Ca, Sr) with tetrafluoroisophthalic acid (H2mBDC-F4). The structures of [{Ca(mBDC-F4)(H2O)2}·H2O] and [{Sr(mBDC-F4)(H2O)2}·H2O] were determined based on ab initio calculations and their powder X-ray diffraction (PXRD) data. The compounds are isomorphous and crystallize in the orthorhombic space group P212121. The determined structures were validated by using extended X-ray absorption (EXAFS) data. The new materials were thoroughly characterized using elemental analysis, thermal analysis, magic angle spinning NMR, and attenuated total reflection-infrared spectroscopy. Further characterization methods such as BET, dynamic vapor sorption, and scanning electron microscopy imaging were also used. Our investigations indicate that mechanochemistry is an efficient method for preparing such materials. KW - Mechanochemistry KW - In situ KW - XRD KW - Coordination polymers PY - 2017 UR - http://pubs.rsc.org/-/content/articlehtml/2017/dt/c7dt00734e DO - https://doi.org/10.1039/c7dt00734e VL - 46 IS - 18 SP - 6003 EP - 6012 AN - OPUS4-41516 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Myrach, Philipp A1 - Jonietz, Florian A1 - Meinel, Dietmar A1 - Suwala, Hubert A1 - Ziegler, Mathias T1 - Calibration of thermographic spot weld testing with X-ray computed tomography JF - Quantative InfraRed Thermography Journal N2 - The paper presents an attempt for the calibration of an active thermography method that is suitable for the non-destructive evaluation of spot welds. Nowadays, the quality of spot welds is commonly characterised by the application of random chisel tests, which are time consuming, expensive and destructive. Recently a non-destructive testing method by means of active thermography was proposed that relies on the fact that the mechanical connection formed by the spot weld also serves as a thermal bridge between the two steel sheets joined in the welding process. It is shown in this paper that this thermal bridge can be thermographically characterised by extracting a measure for the spot weld diameter and hence the quality of the spot weld. The determination of the absolute value of the diameter hereby relies on a calibration of the testing system, which is performed by means of X-ray computed tomography in this study. The experiments were carried out using different experimental approaches, namely transmission as well as reflection geometry wSetup in reflectionith laser illumination. A comprehensive evaluation of samples produced using different welding currents, hence different quality, was carried out in order to validate the thermographic results. KW - Thermography KW - Spot welds KW - Spot welding KW - Computed thomography KW - Non-destructive testing PY - 2017 DO - https://doi.org/10.1080/17686733.2017.1281554 SN - 1768-6733 SN - 2116-7176 VL - 14 IS - 1 SP - 122 EP - 131 PB - Taylor & Francis CY - London AN - OPUS4-40180 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, Luman A1 - de Greef, Nils A1 - Kalinka, Gerhard A1 - Van Bilzen, Bart A1 - Locquet, Jean-Pierre A1 - Verpoest, Ignaas A1 - Won Seo, Jin T1 - Carbon nanotube-grafted carbon fiber polymer composites: Damage characterization on the micro scale JF - Composites Part B N2 - Multiwall carbon nanotubes (CNTs) e carbon fibers (CFs)hybrid materials were produced by directly growing CNTs on CFs by means of chemical vapor deposition. For the latter, the oxidative dehydrogenation reaction of C2H2 and CO2 was applied, which allows growing CNTs without damaging the CF surface. Uni-directional nano-engineered carbon fiber reinforced composites (nFRCs) were fabricated by impregnating these hybrid materials with epoxy. The nFRCs subjected to single fiber push-out tests revealed a decrease of the interfacial shear strength (IFSS) of about 36% compared to the carbon fiber composites without CNTs. By means of transverse three-point bending tests performed on pre-notched composite beams inside a scanning electron microscope, the fracturing behavior parallel to the fibers was studied in-situ. The nFRCs showed significantly reduced fiber/matrix debonding while CNTs pull-out, CNTs bridging as well as matrix failure occurred. These results demonstrate that the presence of CNTs in nFRCs affects the stress distribution and consequently the damage Initiation as well as the damage propagation. The presence of CNTs suppresses the stress concentration at the fiber/Matrix interface and reduces the debonding of CFs from the matrix. However, our results indicate that the stress concentration shifts towards the CNTs' ends/matrix interface and causes promoted matrix failure leading to lower IFSS. KW - Carbon fibres nanotubes interface PY - 2017 DO - https://doi.org/10.1016/j.compositesb.2017.06.004 SN - 1359-8368 SN - 1879-1069 VL - 126 SP - 202 EP - 210 PB - Elsevier CY - Niederlande AN - OPUS4-42202 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Le, Quynh Hoa A1 - Vestergaard, M.C. A1 - Tamiya, E T1 - Carbon-based nanomaterials in biomass-based fuel-fed fuel cells JF - Sensors N2 - Environmental and sustainable economical concerns are generating a growing interest in biofuels predominantly produced from biomass. It would be ideal if an energy conversion device could directly extract energy from a sustainable energy resource such as biomass. Unfortunately, up to now, such a direct conversion device produces insufficient power to meet the demand of practical applications. To realize the future of biofuel-fed fuel cells as a green energy conversion device, efforts have been devoted to the development of carbon-based nanomaterials with tunable electronic and surface characteristics to act as efficient metal-free electrocatalysts and/or as supporting matrix for metal-based electrocatalysts. We present here a mini review on the recent advances in carbon-based catalysts for each type of biofuel-fed/biofuel cells that directly/indirectly extract energy from biomass resources, and discuss the challenges and perspectives in this developing field KW - Carbon-based nanomaterials KW - Biofuel cells KW - Biomass KW - Carbon nanotubes KW - Graphene KW - Carbon nanodots PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-428226 UR - http://www.mdpi.com/1424-8220/17/11/2587/htm DO - https://doi.org/10.3390/s17112587 SN - 1424-8220 VL - 17 IS - 11 SP - 2587, 1 EP - 2587, 21 PB - MDPI AG CY - Basel, Switzerland AN - OPUS4-42822 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wollschläger, Nicole A1 - Häusler, Ines A1 - Ortel, Erik A1 - Hodoroaba, Vasile-Dan A1 - Palasse, L. A1 - Dirscherl, K. T1 - Characterization of porous, TiO2 nanoparticle films using on-axis TKD in SEM – a new nano-analysis tool for a large-scale application JF - Microscopy and Microanalysis N2 - A combined methodical approach is tested with respect to the characterization of the inner structure of porous TiO2 layers as typically used in modern dye sensitized solar cells (DSSC). Their performance is directly linked to the surface area of the pore network. The micrometer thick layer employed was manufactured by screen-printing of a starting TiO2 powder constituted of shape-controlled, bipyramidal anatase nanoparticles on FTO/glass substrates. The analytical methods exploited in our study are Focused Ion Beam (FIB) slicing followed by 3D reconstruction as well as the new approach transmission Kikuchi diffraction (TKD) technology in the scanning electron microscope (SEM). Size and shape distribution of the TiO2 NPs within the layer can be extracted. SEM in transmission mode and atomic force microscopy (AFM) have been used to verify the dimensional data obtained by the new combined methodical approach. Its analytical benefits but also the challenges and limitations are highlighted. KW - TiO2 KW - TKD KW - Particle size distribution KW - Nanoparticles KW - Porous film PY - 2017 UR - https://www.cambridge.org/core/services/aop-cambridge-core/content/view/8A8B29335A2F4D0CB6922F6F5A19C5DC/S1431927617003397a.pdf/characterization_of_porous_tio2_nanoparticle_films_using_onaxis_tkd_in_sem_a_new_nanoanalysis_tool_for_a_largescale_application.pdf DO - https://doi.org/10.1017/S1431927617003397 VL - 23 IS - S1 (July) SP - 542 EP - 543 PB - Cambridge University Press CY - New York, NY, U.S.A. AN - OPUS4-41924 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wollschläger, Nicole A1 - Palasse, L. A1 - Häusler, Ines A1 - Dirscherl, K. A1 - Oswald, F. A1 - Narbey, S. A1 - Ortel, Erik A1 - Hodoroaba, Vasile-Dan T1 - Characterization of the inner structure of porous TiO2 nanoparticle films in dye sensitive solar cells (DSSC) by focused ion beam (FIB) tomography and transmission Kikuchi diffraction (TKD) in the scanning electron microscope (SEM) JF - Materials Characterization N2 - A combined methodical approach is tested for the first time with respect to the characterization of the inner structure of porous TiO2 layers infiltrated with ruthenium molecular sensitizer as typically used in modern dye sensitized solar cells (DSSC). Their performance is directly linked to the surface area ‘offered’ by the pore Network to the dye. The micrometer thick layer employed was manufactured by screen-printing of a starting TiO2 powder constituted of shape-controlled, bipyramidal anatase nanoparticles (NPs) on FTO/glass substrates. The analytical methods exploited in our study are Focused Ion Beam (FIB) slicing followed by 3D reconstruction as well as the new approach transmission Kikuchi diffraction (TKD) technology in the scanning electron microscope (SEM). While the first method results in the visualization of the 3D pore network within the TiO2 layer, the second one can be successfully applied to analyze the crystal orientation of grains (i.e. NPs in our case) in nanometer resolution. Moreover, size and shape distribution of the TiO2 NPs within the layer can be extracted. SEM in transmission mode and atomic force microscopy (AFM) have been used to verify the dimensional data obtained by the new combined methodical approach. Its analytical benefits but also the challenges and limitations are highlighted. KW - Transmission Kikuchi diffraction KW - Focused ion beam tomography KW - Titanium dioxide KW - Nanoparticles KW - Porosity KW - Particle size KW - DSSC PY - 2017 DO - https://doi.org/10.1016/j.matchar.2017.06.030 SN - 1044-5803 SN - 1873-4189 VL - 131 SP - 39 EP - 48 PB - Elsevier AN - OPUS4-40875 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meschut, G. A1 - Janzen, V. A1 - Rethmeier, Michael A1 - Gumenyuk, Andrey A1 - Frei, J. T1 - Charakterisierung des Bruch- und Festigkeits verhaltens von widerstandspunktgeschweißten Aluminiumverbindungen JF - Schweißen und Schneiden N2 - Die Reduktion des Fahrzeuggewichts ist ein wesentlicher Ansatz zur Ver-ringerung des Energie- und Ressourcenverbrauchs und damit zur Senkung der CO2-Emissionen im Automobilbau. In der Karosserieentwicklung kann der vermehrte Einsatz von Aluminiumwerkstoffen einen bedeutenden Beitrag dazu leisten. Im preissensitiven Umfeld des Karosseriebaus etabliert sich das bei Stahlanwendungen genutzte Widerstandspunktschweißen zunehmend auch für Aluminiumverbindungen. Verfahrensbedingte Herausforderungen, wie verkürzte Elektrodenstandzeiten und mangelnde Kenntnis über den Einfluss von Imperfektionen auf die Festigkeit, begrenzen dennoch die Weiterverbreitung des Verfahrens und stellen die Prozessrobustheit insgesamt in Frage. Im Rahmen des hier vorgestellten Forschungsvorhabens wurden das Auftreten verschiedener Brucharten experimentell untersucht und Prognosefunktionen zur Abschätzung der Tragfähigkeit von Widerstandspunktschweißverbindungen unter verschiedenen Belastungsfällen erstellt. Anschließend wurde der Einfluss von Oberflächenrissen und Rissen in der Schweißlinse auf die Scherzugfestigkeit sowohl experimentell als auch simulativ analysiert. KW - Aluminium KW - Widerstandspressschweißen KW - Rissbildung KW - Festigkeit KW - Werkstofffragen PY - 2017 UR - http://www.schweissenundschneiden.de/article/charakterisierung-des-bruch-und-festigkeitsverhaltens-von-widerstandspunktgeschweissten-aluminiumverbindungen/ VL - 69 IS - 3 SP - 126 EP - 133 PB - DVS Media GmbH AN - OPUS4-39577 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Frasca, Daniele A1 - Schulze, Dietmar A1 - Böhning, Martin A1 - Krafft, Bernd A1 - Schartel, Bernhard T1 - Chlorbutylkautschuk/Multilayergraphen-Nanocomposites JF - GAK Gummi Fasern Kunststoffe N2 - In den letzten Jahren werden zunehmend Nanopartikel als Füllstoff für Polymere vorgeschlagen und auch erfolgreich in Elastomer-Nanocomposites eingesetzt. In dieser Arbeit wird Multilayergraphen (MLG) als Nanofüllstoff näher untersucht, der sich bereits bei geringen Konzentrationen als effizient erweist. MLG besteht aus nur etwa zehn Graphenlagen. Chlorbutylkautschuk (CIIR)/MLG-Nanocomposites mit verschiedenen MLG-Gehalten wurden mit Hilfe eines ultraschallunterstützen Mischverfahrens in Lösung hergestellt und auf einem Walzwerk weiterverarbeitet. Das Einmischen von MLG führt zu einer deutlichen Verbesserung der rheologischen und mechanischen Eigenschaften, des Vernetzungsverhaltens sowie der Barrierewirkung gegenüber Gasen. Bereits der Zusatz von 3 phr MLG zu CIIR führt zu einem mehr als zweifach höheren E-Modul und zu einer Reduktion der Permeabilität von O2 und CO2 um 30 %. Höhere Konzentrationen an Nanofüllstoff resultieren in einer weiteren Verbesserung der Eigenschaften der Nanocomposites. Weiterhin zeigten die CIIR/MLG-Nanocomposites auch eine geringere Entflammbarkeit. KW - Elastomere KW - Nanokomposite KW - Graphen KW - Chlorbutylkautschuk PY - 2017 SN - 0176-1625 VL - 70 IS - 5 SP - 311 EP - 322 PB - Dr. Gupta Verlag CY - Ratingen AN - OPUS4-40327 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kalinka, Gerhard A1 - ElAbshihy, K. T1 - Circumventing boundary effects while characterizing epoxy/copper interphases using nanoindentation JF - Composite Interfaces N2 - Characterization of the size and mechanical properties of interphases is essential when designing multicomponent materials. When nanoindentation is used to investigate the size and mechanical properties of an interphase, a common challenge is that the indenter or the stress zone formed around it are often restricted by the reinforcement, making it difficult to distinguish the mechanical property variations caused by the interphase itself from those caused by the boundary effect. In this work, a testing system was developed that allows determining the indent affected zone and accounting for it in the interphase measurements of an epoxy/Cu system. Using finite element analysis, we confirmed the validity of the proposed system. Nanoindentation was used to investigate the Interphase between copper and two different epoxy systems; amine-cured and anhydride-cured. Nanoindentation results showed that a copper layer that is only 10 nm thick still exhibits a constriction effect on the indentations in its vicinity. The amine-cured epoxy did not show any sign of interphase existence using the introduced method. However, a soft interphase with a thickness of ~1.7 μm was measured on theanhydride-cured epoxy. Furthermore, we show that the proposed system can be used to determine the interphase thickness as well as its relative mechanical properties regardless of the indentation depth. This system can be further used for investigating other polymer/metal interphases to better understand the factors influencing them, thus helping engineer the interphase size and properties to enhance composite performance. KW - Interphase KW - Polymer-metal KW - Epoxy KW - Copper KW - Composites KW - Nanoindentation PY - 2017 DO - https://doi.org/10.1080/09276440.2017.1286878 SN - 0927-6440 SN - 1568-5543 VL - 24 IS - 9 SP - 833 EP - 848 PB - Taylor & Francis CY - UK AN - OPUS4-39128 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Friedrich, Jörg A1 - Altmann, Korinna A1 - Wettmarshausen, Sascha A1 - Hidde, Gundula T1 - Coating of carbon fibers with adhesion-promoting thin polymer layers using plasma polymerization or electrospray ionization technique—A comparison JF - Plasma Processes and Polymers N2 - Plasma polymers and electrospray-ionization (ESI) polymer layers are compared for most efficient adhesion promotion in carbon fiber-epoxy resin composites. The ultra-thin ESI layers (2–30 nm) of commercial poly(acrylic acid) and poly-(hydroxyethylmethacrylate) produce an significant increase of adhesion measured by single-fiber pull out tests. However, plasma Treatment has also advantages, such as simultaneous activation of the fiber substrate. Chemical structure and composition are rather far from the regular structure of commercial polymers as deposited by ESI processing. KW - Plasma polymers KW - Electrospray ionization polymers KW - Poly(acrylic acid) KW - Poly- (hydroxyethylmethacrylate) PY - 2017 DO - https://doi.org/10.1002/ppap.201600074 SN - 1612-8869 SN - 1612-8850 VL - 14 IS - 3 SP - e1600074-1 EP - 14 AN - OPUS4-40510 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bochnig, M. S. A1 - Oh, M.-J. A1 - Nagel, T. A1 - Jost-Brinkmann, P.-G. A1 - Ziegler, Fred T1 - Comparison of the shock absorption capacities of different mouthguards JF - Dental Traumatologie N2 - In this in vitro study, the protective qualities of different mouthguard types were examined during small hard object collisions. The aim was to investigate inconclusive aspects of hard inserts, nylon nets, and air spaces as reinforcements in the anterior region and the protection qualities of ethylene vinyl acetate (EVA). Five different mouthguards with a labial thickness between 2 mm and 11 mm made of materials of varying stiffness were investigated. As a negative control, the same experiments were performed without a mouthguard. Different combinations of EVA and labial inserts ((polyethylene terephthalate glycol-modified [PETG]), nylon mesh, air space) were tested. Using a stainless steel pendulum device, blows of different energy (0.07-2.85 joules) were applied to the center of the crown of a pivoted tooth in a custom-built jaw model. A laser Doppler vibrometer measured the tooth deflection, while an acceleration sensor attached to the pendulum measured the braking accelerations. Tooth deflection was reduced up to 99.7% compared to no mouthguard, and the braking acceleration was reduced up to 72.2% by increasing the mouthguards' labial thickness in combination with labial inserts of different stiffness and a built-in air space between the front teeth and the mouthguard. The mouthguards made of soft materials (EVA with nylon mesh) showed slightly better protection qualities than the more rigid mouthguards of similar thickness (PETG; P<.05). However, with increasing impact energy, their protective capacities decreased to a greater extent than the stiffer mouthguards. The combination of increased labial thickness and labial inserts of varying stiffness and eventually an air space offers the best protection capacities for hard, small object collisions. KW - Shock absorbtion KW - Hard object collisions KW - Mouthguard PY - 2017 DO - https://doi.org/10.1111/edt.12324 SN - 1600-4469 VL - 33 IS - 3 SP - 205 EP - 213 PB - John Wiley & Sons, Ltd CY - Hoboken, NJ, USA AN - OPUS4-41098 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nguyen, Thi Yen A1 - Roessler, Ernst A1 - Rademann, Klaus A1 - Emmerling, Franziska T1 - Control of organic polymorph formation: crystallization pathways in acoustically levitated droplets JF - Zeitschrift für Kristallographie - Crystalline Materials N2 - Theoretical and experimental studies indicate that crystal nucleation can take more complex pathways than expected on the ground of the classical nucleation theory. Among these pathways are the formation of pre-nucleation clusters and amorphous precursor phases. A direct in situ observation of the different pathways of nucleation from solution is challenging since the paths can be influenced by heterogeneous nucleation sites, such as container walls. Here, we provide insights into the crystallization process using the in situ combination of an acoustic levitator, Raman spectroscopy, and X-ray scattering. The contactless sample holder enables the observation of homogeneous crystallization processes and the detection of intermediates and final crystalline forms. We provide evidence for the existence of multiple pathways of nucleation based on the investigation of the crystallization of organic molecules from different solvents. Starting from a diluted solution, a supersaturation is reached during the experiment due to the evaporation of the solvent. The highly supersaturated solution reveals different pathways of crystallization. Depending on the degree of supersaturation either the thermodynamically stable or the metastable crystal form is observed. KW - Crystallization KW - In situ XRD KW - Polymorphism KW - Polyamorphism KW - Raman spectroscopy PY - 2017 DO - https://doi.org/10.1515/zkri-2016-1964 SN - 2194-4946 SN - 2196-7105 VL - 232 IS - 1-3 SP - 15 EP - 24 PB - De Gruyter CY - Berlin AN - OPUS4-39708 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Breitenbach, Romy A1 - Silbernagl, Dorothee A1 - Toepel, J. A1 - Sturm, Heinz A1 - Broughton, William J. A1 - Sassaki, G. L. A1 - Gorbushina, Anna T1 - Corrosive extracellular polysaccharides of the rock-inhabiting model fungus Knufia petricola JF - Extremophiles N2 - Melanised cell walls and extracellular polymeric matrices protect rock-inhabiting microcolonial fungi from hostile environmental conditions. How extracellular polymeric substances (EPS) perform this protective role was investigated by following development of the model microcolonial black fungus Knufia petricola A95 grown as a sub-aerial biofilm. Extracellular substances were extracted with NaOH/formaldehyde and the structures of two excreted polymers studied by methylation as well as NMR analyses. The main polysaccharide (~ 80%) was pullulan, also known as α-1,4-; α-1,6-glucan, with different degrees of polymerisation. Αlpha-(1,4)-linked-Glcp and α-(1,6)-linked-Glcp were present in the molar ratios of 2:1. A branched galactofuromannan with an α-(1,2)-linked Manp main chain and a β-(1,6)-linked Galf side chain formed a minor fraction (~ 20%). To further understand the roles of EPS in the weathering of minerals and rocks, viscosity along with corrosive properties were studied using atomic force microscopy (AFM). The kinetic viscosity of extracellular K. petricola A95 polysaccharides (≈ 0.97 × 10-6 m2 s-1) ranged from the equivalent of 2% (w/v) to 5% glycerine, and could thus profoundly affect diffusion-dominated processes. The corrosive nature of rock-inhabiting fungal EPS was also demonstrated by its effects on the aluminium coating of the AFM cantilever and the silicon layer below. KW - Corrosion KW - EPS KW - Melanised microcolonial fungi (MCF) KW - Pullulan KW - Sub-aerial biofilms (SAB) KW - α-1,4- and α-1,6-glucans KW - AFM cantilever vibration KW - Nanoviscosity KW - Nanocorrosion of aluminium and silicon PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-435910 DO - https://doi.org/10.1007/s00792-017-0984-5 SN - 1433-4909 SN - 1431-0651 VL - 22 IS - 2 SP - 165 EP - 175 PB - Springer CY - Berlin AN - OPUS4-43591 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Epping, Ruben A1 - Panne, Ulrich A1 - Falkenhagen, Jana T1 - Critical conditions for liquid chromatography of statistical copolymers: Functionality type and composition distribution characterization by UP-LCCC/ESI-MS JF - Analytical Chemistry N2 - Statistical ethylene oxide (EO) and propylene oxide (PO) copolymers of different monomer compositions and different average molar masses additionally containing two kinds of end groups (FTD) were investigated by ultra high pressure liquid chromatography under critical conditions (UP-LCCC) combined with electrospray ionization time-of flight mass spectrometry (ESI-TOFMS). Theoretical predictions of the existence of a critical adsorption point (CPA) for statistical copolymers with a given chemical and sequence distribution1 could be studied and confirmed. A fundamentally new approach to determine these critical conditions in a copolymer, alongside the inevitable chemical composition distribution (CCD), with mass spectrometric detection, is described. The shift of the critical eluent composition with the monomer composition of the polymers was determined. Due to the broad molar mass distribution (MMD) and the presumed existence of different end group functionalities as well as monomer sequence distribution (MSD), Gradient separation only by CCD was not possible. Therefore, isocratic separation conditions at the CPA of definite CCD fractions were developed. Although the various present distributions partly superimposed the separation process, the goal of separation by end group functionality was still achieved on the basis of the additional dimension of ESI-TOF-MS. The existence of HO-H besides the desired allylO-H end group functionalities was confirmed and their amount estimated. Furthermore, indications for a MSD were found by UPLC/MS/MS measurements. This approach offers for the first time the possibility to obtain a fingerprint of a broad distributed statistical copolymer including MMD, FTD, CCD, and MSD. KW - Polymer KW - Liquid chromatography at critical conditions KW - ESI-TOF-MS PY - 2017 DO - https://doi.org/10.1021/acs.analchem.6b04064 SN - 0003-2700 SN - 1520-6882 VL - 89 IS - 3 SP - 1778 EP - 1786 AN - OPUS4-39240 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wilke, Manuel A1 - Kabelitz, Anke A1 - Zimathies, Annett A1 - Rademann, K. A1 - Emmerling, Franziska T1 - Crystal structure and in situ investigation of a mechanochemical synthesized 3D zinc N-(phosphonomethyl)glycinate JF - Journal of Materials Science N2 - The mechanochemical synthesis of the zinc N-(phosphonomethyl)glycinate Zn(O₃PCH₂NH₂CH₂CO₂) H₂O is presented. The structure was solved from powder X-ray diffraction (PXRD) data. In the three-dimensional pillared structure, the Zn atoms are coordinated tetrahedrally. In situ investigations of the reaction process with synchrotron PXRD and Raman spectroscopy reveal a two-step process including the formation of an intermediate. KW - Mechanochemistry KW - Metal phosphonate KW - In situ PY - 2017 DO - https://doi.org/10.1007/s10853-017-1121-7 SN - 0022-2461 SN - 1573-4803 VL - 52 IS - 20 SP - 12013 EP - 12020 PB - Springer CY - New York AN - OPUS4-41490 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Matoga, D. A1 - Roztocki, K. A1 - Wilke, Manuel A1 - Emmerling, Franziska A1 - Oszajca, M. A1 - Fitta, M. A1 - Bałanda, M. T1 - Crystalline bilayers unzipped and rezipped: solid-state reaction cycle of a metal–organic framework with triple rearrangement of intralayer bonds JF - CrystEngComm N2 - We present a series of remarkable structural transformations for a family of layered metal–organic frameworks (MOFs) in a three-step solid-state reaction cycle. The cycle represents new dynamic behavior of 2D coordination polymers and involves the sequence of reactions: {[Mn2(ina)4(H2O)2]·2EtOH}n (JUK-1) → {(NH4)2[Mn(ina)2(NCS)2]}n·xH2O (JUK-2) → {[Mn2(ina)2(Hina)2(NCS)2]}n (JUK-3) → JUK-1 (Hina = isonicotinic acid), each accompanied by rearrangement of intralayer coordination bonds and each induced by a different external stimulus. In situ investigation of the first step of the cycle by combined synchrotron X-ray diffraction and Raman spectroscopy reveals direct mechanochemical unzipping of JUK-1 bilayers to respective JUK-2 layers with reaction rates dependent on the milling conditions. In contrast, the reverse zipping of JUK-2 layers involves two steps and proceeds through a new MOF (JUK-3) whose structure was elucidated by powder X-ray diffraction. Magnetic measurements confirm conversions of manganese nodes in the reaction cycle. The findings indicate the possibility of developing coordination-based assemblies with large structural responses for use in smart stimuli-responsive systems and sensor technologies. KW - Mechanochemistry KW - In situ KW - XRD KW - MOF PY - 2017 UR - http://pubs.rsc.org/is/content/articlehtml/2017/ce/c7ce00655a DO - https://doi.org/10.1039/C7CE00655A VL - 19 SP - 2987 EP - 2995 AN - OPUS4-41517 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Leng, Jing A1 - Kang, N. A1 - Wang, D.-Y. A1 - Wurm, Andreas A1 - Schick, C. A1 - Schönhals, Andreas T1 - Crystallization behavior of nanocomposites based on poly(L-lactide) and MgAl layered double hydroxides - Unbiased determination of the rigid amorphous phases due to the crystals and the nanofiller JF - Polymer N2 - Semicrystalline polymers have to be described by a three phase model consisting of a mobile amorphous (MAF), a crystalline (CF), and a rigid amorphous fraction (RAF). For nanocomposites based on a semicrystalline polymer the RAF is due to both the crystallites (RAFcrystal) and the filler (RAFfiller). Polymer nanocomposite based on poly(L-lactide) and MgAl layered double hydroxide nanofiller were prepared. Due to the low crystallization rate of PLA ist crystallization can be suppressed by a high enough cooling rate, and the RAF is due only to the nanofiller. The MAF, CF, and RAF were estimated by Temperature Modulated DSC. For the first time CF, MAF, RAFcrystal, and RAFfiller could be estimated. It was found, that RAFfiller increases linearly with the concentration of the nanofiller for this system. Furthermore, RAFcrystal is only slightly influenced by the presence of the nanofiller. KW - Polymer based nanocomposites PY - 2017 DO - https://doi.org/10.1016/j.polymer.2016.11.065 SN - 0032-3861 SN - 1873-2291 VL - 108 SP - 257 EP - 264 PB - Elesevier AN - OPUS4-39052 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nolze, Gert A1 - Winkelmann, Aimo T1 - Crystallometric and projective properties of Kikuchi diffraction patterns JF - Journal of Applied Crystallography N2 - Kikuchi diffraction patterns can provide fundamental information about the lattice metric of a crystalline phase. In order to improve the possible precision and accuracy of lattice parameter determination from the features observed in Kikuchi patterns, some useful fundamental relationships of geometric crystal-lography are reviewed, which hold true independently of the actual crystal symmetry. The Kikuchi band positions and intersections and the Kikuchi band widths are highly interrelated, which is illustrated by the fact that all lattice plane trace positions of the crystal are predetermined by the definition of only four traces. If, additionally, the projection centre of the gnomonic projection is known, the lattice parameter ratios and the angles between the basis vectors are fixed. A further definition of one specific Kikuchi band width is sufficient to set the absolute sizes of all lattice parameters and to predict the widths of all Kikuchi bands. The mathematical properties of the gnomonic projection turn out to be central to an improved interpretation of Kikuchi pattern data, emphasizing the importance of the exact knowledge of the projection centre. KW - EBSD KW - Crystallography KW - Kikuchi patterns KW - Projective geometry PY - 2017 DO - https://doi.org/10.1107/S1600576716017477 SN - 1600-5767 VL - 50 IS - Part 1 SP - 102 EP - 119 PB - International Union of Crystallography AN - OPUS4-39061 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Erdmann, Maren A1 - Trappe, Volker A1 - Sturm, Heinz A1 - Braun, Ulrike A1 - Dümichen, Erik T1 - Cure conversion of structural epoxies by cure state analysis and in situ cure kinetics using nondestructive NIR spectroscopy JF - Thermochimica Acta N2 - Non-isothermal heating rate kinetics was applied to two epoxy resin systems. In situ near-infrared (NIR) measurements were taken with a heatable NIR cell which allowed the cure to be monitored by characteristic absorption bands. An autocatalyzed reaction of the nth order was shown to describe the epoxy conversion curves. Differential Scanning Calorimetry (DSC) was used as a complementary method. The kinetic models developed by both NIR and DSC are in good accordance with experimental epoxy conversion in the in situ NIR setup for single and multiple cure temperature ramps. A linear calibration curve of the characteristic absorption bands of epoxy normalized to aromatic vibrations was introduced. The curing degree of structural epoxies that were cured according to an industrial temperature cure profile was determined by NIR using the calibration curve. The epoxy conversions of the structural components showed good agreement with the experimental in situ NIR. Several degrees of cure for structural specimens were evaluated by NIR and residual reaction enthalpy by DSC. We present the non-destructive NIR spectroscopy as an alternative to determine fast and non-destructive epoxy conversion, particularly suitable for high degrees of cure on structural components. KW - Epoxy resin KW - Curing kinetics KW - In situ near-infrared (NIR) spectroscopy KW - Differential scanning calorimetry (DSC) PY - 2017 UR - http://www.sciencedirect.com/science/article/pii/S0040603117300205 DO - https://doi.org/10.1016/j.tca.2017.01.010 SN - 0040-6031 SN - 1872-762X VL - 650 SP - 8 EP - 17 PB - Elsevier B.V. AN - OPUS4-39123 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, Hans R. A1 - Weidner, Steffen A1 - Scheliga, Felix T1 - Cyclic poly(l-lactide) via ring-expansion polymerization by means of dibutyltin 4-tert-butylcatecholate JF - Macromolecular Chemistry and Physics N2 - Five new catalysts are prepared from dibutyltin oxide and catechol (HCa), 2,3-dihydroxynaphthalene (NaCa), 4-tert-butyl catechol (BuCa), 4-cyano catechol (CyCa), and 4-benzoyl catechol (BzCa), but only BuCa gives useful results. When benzyl alcohol is used as an initiator, linear chains having benzyl ester end groups are formed in a slow polymerization process. In contrast to cyclic or noncyclic dibutyltin bisalkoxides, neat BuCa yields cyclic poly(l-lactide)s via a fast ring-expansion polymerization. Under certain conditions, a high-melting crystalline phase (Tm = 191 °C) is obtained. At 160 °C and short reaction times even-numbered cycles are slightly prevailing, but, surprisingly, at 120 °C, odd-numbered cycles are predominantly formed. These results definitely prove that a ring-expansion mechanism is operating. KW - Lactides KW - MALDI TOF MS KW - Morphology KW - Ring-opening polymerization KW - Tin catalysts PY - 2017 DO - https://doi.org/10.1002/macp.201700274 SN - 1521-3935 SN - 1022-1352 VL - 218 IS - 22 SP - 1700274, 1 EP - 1700274, 10 PB - Wiley VCH CY - Weinheim AN - OPUS4-43583 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H. R. A1 - Weidner, Steffen A1 - Scheliga, F. T1 - Cyclic poly(L-lactide)s via ring-expansion polymerizations catalysed by 2,2-dibutyl-2- stanna-1,3-dithiolane JF - Polymer Chemistry N2 - L-Lactides were polymerized in bulk at 120 or 160 °C with cyclic dibutyltin catalysts derived from 1,2-dimercaptoethane or 2-mercaptoethanol. Only linear chains having one benzyl ester and one OH-end group were obtained when benzyl alcohol was added. When L-lactides were polymerized with neat dibutyl-2-stanna-1,3-dithiolane, exclusively cyclic polylactides were formed even at 120 °C. The temperature, time and monomer/catalyst ratio (M/C) were varied. These results are best explained by a combination of ring-expansion polymerization and ring-extrusion of cyclic oligo- or polylactides with Elimination of the cyclic catalyst. Neither syntheses of linear polylactides nor of cyclic lactides involved racemization up to 20 h at 160 °C. KW - Ring-expansion polymerization KW - MALDI KW - Polylactides PY - 2017 DO - https://doi.org/10.1039/C6PY02166B SN - 1759-9954 SN - 1759-9962 VL - 8 IS - 9 SP - 1589 EP - 1596 PB - Royal Society of Chemistry AN - OPUS4-39748 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H. R. A1 - Weidner, Steffen A1 - Scheliga, F. T1 - Cyclic Polylactides via Simultaneous Ring-Opening Polymerization and Polycondensation Catalyzed by Dibutyltin Mercaptides JF - Journal of Polymer Science A - Polymer Chemistry N2 - L-Lactide is polymerized in bulk at 160 8C either with dibutyltin bis(benzylmercaptide) (SnSBzl), dibutyltin bis(benzothiazole 2-mercaptide) (SnMBT), or with dibutyltin bis(pentafluorothiophenolate) (SnSPF) as catalysts. SnSBzl yields linear polylactides having benzylthio-ester end groups in addition to cyclic polylactides, whereas SnMBT and SnSPF mainly or exclusively yield cyclic polylactides. This finding, together with model reactions, indicates that the SnS catalysts promote a combined ring-opening polymerization and polycondensation process including end-to-end cyclization. SnMBT caused slight racemization (3%–5%), when used at 160 8C. With SnSPF optically pure cyclic poly(L-lactide)s with high-molecular weights can be prepared at 160 8C. KW - Cyclopolymerization KW - Catalysts KW - MALDI-TOF MS KW - Polyester KW - Ring-opening polymerization PY - 2017 DO - https://doi.org/10.1002/pola.28762 VL - 55 IS - 22 SP - 3767 EP - 3775 PB - Wiley Periodicals AN - OPUS4-42600 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H. A1 - Weidner, Steffen A1 - Scheliga, F. ED - Shaplov, A. T1 - Cyclization and dispersity of polyesters JF - Macomolecular Symposia N2 - Two classes of polyesters were prepared by irreversible polycondensations. The dependence of the dispersities on the experimental parameters such as synthetic method, chemical structure, molecular weight and initial monomer concentration was determined. At first it was demonstrated that it is essential for a correct calculation of Mn and Mw to include all oligomers down to the dimers in the evaluation of SEC curves. Furthermore, it was demonstrated for poly(e-caprolactone)s and polylactides that reversible polycondensations and ring-opening polymerizations with equilibration yield identical products. Finally, the dependence of the dispersity on various experimental Parameters was determined for equilibrated poly(e-caprolactone)s and polylactides. KW - Irreversible polycondensation KW - Polycaprolactone KW - Polylactide KW - Dispersity KW - MALDI-TOF MS PY - 2017 DO - https://doi.org/10.1002/masy.201600169 SN - 1022-1360 SN - 1521-3900 VL - 375 IS - 1 SP - Article 1600169, 1 EP - 6 PB - Wiley-VCH AN - OPUS4-42407 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zerbst, Uwe A1 - Hilgenberg, Kai T1 - Damage development and damage tolerance of structures manufactured by selective laser melting - a review JF - 3rd International symposium on fatigue design and material defects (FDMD 2017) N2 - The additive manufacturing technology of Selective Laser Melting (SLM) experiences a rapid development within an increasing marked of quite different application fields. The properties of SLM materials and structures are influenced by a number of tech-nological parameters such as the metal powder (particle size, homogeneity, cleanliness), the laser tool (power, beam diameter, pulse lengths), the scanning operation (speed, sequence and orientation of melting paths), parameters of the over-all equipment (design and preheating of the base plate, currents and turbulence in the protective gas atmosphere) and, last not least, the hatching strategy including the build-up direction of the structure with respect to the loading direction of the component. For the perspective use of SLM structures as load carrying, safety-relevant components the knowledge of their mechanical properties is necessary. It is essential to understand these in the context of the manufacturing-related features and at the back-ground of the basic characteristics of metallic materials: crystal lattice, microstructure and material defects. The paper provides an overview on factors which affect the mechanical parameters stiffness, strength, ductility, toughness, fatigue crack propagation and fatigue strength in the context of selective laser melting. T2 - FDMD 2017 CY - Lecco, Italy DA - 19.09.2017 KW - Fatigue strength KW - Fracture mechanics KW - Initial crack size KW - Short crack propagation KW - Multiple crack propagation PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-438511 DO - https://doi.org/10.1016/j.prostr.2017.11.071 SN - 2452-3216 VL - 7 SP - 141 EP - 148 PB - ScienceDirect CY - Lecco, Italy AN - OPUS4-43851 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Hertwig, Andreas A1 - Heidari, M. A1 - von Klitzing, R. A1 - Napolitano, S. A1 - Sferrazza, M. A1 - Schönhals, Andreas T1 - Decoupling of dynamic and thermal glass transition in thin films of a PVME/PS blend JF - ACS Macro Letters N2 - The discussions on the nanoconfinement effect on the glass transition and glassy dynamics phenomena have yielded many open questions. Here, the thickness dependence of the thermal glass transition temperature of thin films of a PVME/PS blend is investigated by ellipsometry. Its thickness dependence was compared to that of the dynamic glass transition (measured by specific heat spectroscopy), and the deduced Vogel temperature (T0). While and T0 showed a monotonous increase, with decreasing the film thickness, the dynamic glass transition temperature () measured at a finite frequency showed a non-monotonous dependence that peaks at 30 nm. This was discussed by assuming different cooperativity length scales at these temperatures, which have different sensitivities to composition and thickness. This non-monotonous thickness dependence of disappears for frequencies characteristic for T0. Further analysis of the fragility parameter, showed a change in the glassy dynamics from strong to fragile, with decreasing film thickness. KW - Thin polymeric films KW - Ellipsometry KW - Specific heat spectroscopy PY - 2017 DO - https://doi.org/10.1021/acsmacrolett.7b00625 SN - 2161-1653 VL - 6 IS - 10 SP - 1156 EP - 1161 PB - ACS Publications AN - OPUS4-42266 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -