TY - CONF A1 - Bauer, J. A1 - Miclea, P.-T. A1 - Braun, U. A1 - Altmann, Korinna A1 - Turek, M. A1 - Hagendorf, C. T1 - Microplastic detection and analysis in water samples N2 - Microplastic detection in water samples becomes important for tracing microplastic sources. Microplastic may harm desalination facilities by blocking filters and disturbing the marine food chain. Thermo analytical methods such as pyrolysis gas chromatography mass spectroscopy, and spectroscopic methods like (micro) Raman spectroscopy or (micro) Fouriertransform infrared spectroscopy in combination with appropriate filters and sample preparation are suitable for analyzing microplastics on a scale from 1 µm to 1000 µm fast and unambiguous. While the thermo analytical methods are suitable for larger sample volumes, Raman spectroscopy and Fouriertransform infrared spectroscopy are able to detect and analyze single microplastic particles for instance in bottled water. Machine learning algorithms ensure a reliable classification of different plastic materials. T2 - International Conference on Sustainable Energy-Water-Environment Nexus in Desert Climate 2019 CY - Ar-Rayyan, Qatar DA - 02.12.2019 KW - Microplastics KW - Water samples PY - 2022 SP - 111 EP - 113 PB - Springer AN - OPUS4-56240 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Ahiboz, D. A1 - Andresen, Elina A1 - Manley, P. A1 - Resch-Genger, Ute A1 - Würth, Christian A1 - Becker, C. T1 - Enhanced photon upconversion using erbium-doped nanoparticles interacting with silicon metasurfaces N2 - Photon upconversion (UC) using trivalent erbium (Er+3) doped crystals is a promising concept to harness near infrared photons of the solar spectrum which cannot be directly absorbed by silicon solar cells. However, their UC efficiency at low-intensity 1 sun illumination is not relevant on device level so far. Exploiting giant near-field enhancement effects on metasurfaces is an appealing approach to enable efficient UC at low irradiance conditions. Here, we report on more than 1000-fold enhanced photon UC of NaYF4:Er+3 nanoparticles interacting with the near-fields supported by a silicon metasurface under 1550 nm excitation. T2 - 48th Photovoltaic Specialists Conference (PVSC) CY - Online meeting DA - 20.06.2021 KW - Nano KW - Nanomaterial KW - Upconversion nanoparticle KW - Lanthanide KW - Photoluminescence KW - Quantum yield KW - Photophysics KW - Lifetime KW - Sensor KW - Excitation power density KW - Brightness KW - NIR KW - Mechanism KW - Modeling KW - Simulation KW - Energy transfer KW - Photonic crystal KW - Enhancement strategy PY - 2021 U6 - https://doi.org/10.1109/pvsc43889.2021.9518495 SP - 1 EP - 3 PB - IEEE CY - Berlin AN - OPUS4-53786 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Florian, Camilo A1 - Deziel, J.-L. A1 - Kirner, Sabrina V. A1 - Siegel, J. A1 - Bonse, Jörn T1 - Femtosecond laser-induced oxidation in the formation of periodic surface structures N2 - Micro- and nanostructuring with laser-induced periodic surface structures (LIPSS) has been demonstrated to be feasible in a wide variety of materials including metals, semiconductors and dielectrics. Suitable processing regimes for flat, curved and complex surfaces have been identified for many materials, allowing the generation of diverse applications in fields such as optics, tribology and medicine, to name a few. A common side effect when producing such structures in air environment is the formation of a thin surface oxide layer in the laser irradiated areas. Previous studies have shown that oxidation plays an important role in the tribological performance for which the structures where created, and very recently it has been shown that the laser-induced oxide graded layers may contribute to the formation of a new type of embedded low-spatial frequency LIPSS (LSFL) with annomalous orientation parallel to the laser polarization, in addition to the appearance of the well-known high-spatial frequency LIPSS (HSFL) at the surface. In this contribution, we explore this effect experimentally for chromium nitride (CrN) irradiated with femtosecond laser pulses and compare the findings to finite-difference time-domain (FDTD) simulations of the intensity distributions at different depth positions. T2 - 2021 Conference on Lasers and Electro-Optics/Europe – European Quantum Electronics Virtual Conferences CY - Munich, Germany DA - 21.06.2021 KW - Femtosecond laser ablation KW - Finite-difference time-domain calculations KW - Laser-induced periodic surface structures (LIPSS) KW - Surface oxidation PY - 2021 SN - 978-1-6654-1876-8 U6 - https://doi.org/10.1109/CLEO/Europe-EQEC52157.2021.9542774 VL - 2021 SP - 1 PB - Institute of Electrical and Electronics Engineers (IEEE) CY - Piscataway, NJ, USA AN - OPUS4-53457 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Oster, Simon A1 - Maierhofer, Christiane A1 - Mohr, Gunther A1 - Hilgenberg, Kai A1 - Ulbricht, Alexander A1 - Altenburg, Simon T1 - Investigation of the thermal history of L-PBF metal parts by feature extraction from in-situ SWIR thermography N2 - Laser powder bed fusion is used to create near net shape metal parts with a high degree of freedom in geometry design. When it comes to the production of safety critical components, a strict quality assurance is mandatory. An alternative to cost-intensive non-destructive testing of the produced parts is the utilization of in-situ process monitoring techniques. The formation of defects is linked to deviations of the local thermal history of the part from standard conditions. Therefore, one of the most promising monitoring techniques in additive manufacturing is thermography. In this study, features extracted from thermographic data are utilized to investigate the thermal history of cylindrical metal parts. The influence of process parameters, part geometry and scan strategy on the local heat distribution and on the resulting part porosity are presented. The suitability of the extracted features for in-situ process monitoring is discussed. T2 - Thermosense: Thermal Infrared Applications XLIII CY - Online meeting DA - 12.04.2021 KW - SWIR camera KW - Additive manufacturing (AM) KW - Selective laser melting (SLM) KW - Laser beam melting (LBM) KW - In-situ monitoring KW - Infrared thermography PY - 2021 SN - 978-1-5106-4324-6 U6 - https://doi.org/10.1117/12.2587913 VL - 11743 SP - 1 EP - 11 PB - SPIE - The international society for optics and photonics AN - OPUS4-52535 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - D'Accardi, E. A1 - Ulbricht, Alexander A1 - Krankenhagen, Rainer A1 - Palumbo, D. A1 - Galietti, U. T1 - Capability of active thermography to detect and localize pores in Metal Additive Manufacturing materials N2 - Active thermography is a fast, contactless and non-destructive technique that can be used to detect internal defects in different types of material. Volumetric irregularities such as the presence of pores in materials produced by the Additive Manufacturing processes can strongly affect the thermophysical and the mechanical properties of the final component. In this work, an experimental investigation aimed at detecting different pores in a sample made of stainless AISI 316L produced by Laser Powder Bed Fusion (L-PBF) was carried out using pulsed thermography in reflection mode. The capability of the technique and the adopted setups in terms of geometrical and thermal resolution, acquisition frequency and energy Density of the heating source were assessed to discern two contiguous pores as well as to detect a single pore. Moreover, a quantitative indication about the minimum resolvable pore size among the available and analysed defects was provided. A powerful tool to assess the Limits and the opportunities of the pulsed technique in terms of detectability and localizability was provided by comparing active thermography results to Computed Tomography as well as a related Finite Element Analysis (FEA) to simulate the pulsed heating transfer with Comsol. T2 - 49th Italian Association for Stress Analysis Conferencee (AIAS 2020) CY - Online meeting DA - 02.09.2020 KW - Additive manufacturing KW - Laser powderbed fusion KW - Pores KW - Thermography KW - Micro-CT PY - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-519231 VL - 1038 SP - 1 EP - 17 PB - Institute of Physics CY - London AN - OPUS4-51923 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Altenburg, Simon A1 - Scheuschner, Nils A1 - Straße, Anne A1 - Gumenyuk, Andrey A1 - Maierhofer, Christiane T1 - Towards the determination of real process temperatures in the LMD process by multispectral thermography N2 - Due to the rapid thermal cycles involved in additive manufacturing of metals, high internal stresses and peculiar microstructures occur, which influence the parts mechanical properties. To systematically examine their formation, in-process measurements of the temperature are needed. Since the part emissivity is strongly inhomogeneous and rapidly changing in the process, the applicability of thermography for the determination of thermodynamic temperatures is limited. Measuring the thermal radiation in different wavelengths simultaneously, temperature and emissivity can be separated. Here, we present results of a preliminary study using multispectral thermography to obtain real temperatures and emissivities in directed energy deposition (DED) processes. T2 - Thermosense: Thermal Infrared Applications XLIII CY - Online meeting DA - 12.04.2021 KW - Additive Manufacturing KW - Process monitoring KW - Multispectral thermography KW - Laser metal deposition KW - TES KW - LMD KW - Temperature emissivity separation PY - 2021 U6 - https://doi.org/10.1117/12.2587881 VL - 2021 SP - 77 EP - 83 PB - SPIE AN - OPUS4-52516 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zaghdoudi, Maha A1 - Weber, Mike A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Numerical Modelling of Compression Stress Relaxation and Compression Set of Elastomer O-Ring During Aging N2 - Elastomer seals are used in many industrial applications due to their excellent mechanical properties at a wide range of temperatures. Their high versatility and recovery potential under several load conditions make them well suitable for the application in containers designed for transport, storage and/or disposal of radioactive materials. In containers for low and intermediate level radioactive waste, elastomer seals are used as barrier seals, and as auxiliary seals in storage and transportation casks (dual purpose casks) for heat generating radioactive waste, such as spent fuel and high-level waste. While a seal exchange at defined intervals is typical in many conventional applications, it is impossible or at least hard to perform when principles of minimization of radiation exposure have to be considered and prohibit an unnecessary cask handling. An extensive knowledge of the change of the elastomer’s properties during aging and the availability of reliable end-of-lifetime criteria to guarantee the permanent safe enclosure of the radioactive material is mandatory. As BAM is involved in most of the national cask licensing procedures and in the evaluation of cask-related long-term safety issues, great efforts have been already made and are still planned to scientifically support this task. Compression stress relaxation and compression set were identified as key indicators of elastomer long-term performance and quantitatively investigated in comprehensive test programs. Among other representative types of elastomers, specimens made from ethylene propylene diene rubber (EPDM) were tested before, during and after aging to capture the most important of their complex mechanical properties. In the presented study, exemplary results were used to simulate the compression stress relaxation and the compression set of elastomer O-rings during aging. Regarding the influence of temperature, the time-temperature superposition principle is applied in the relaxation analysis of elastomer O-rings. The proposed model is implemented in the commercial finite element software ABAQUS/Standard® [1] with a sequential temperature displacement coupling. Numerical results match the experimental compression stress relaxation measurements well. The prediction of compression set values after long-term aging shows a relatively good agreement with the experimental results. Nevertheless, all input parameters derived from the specimen tests, additional assumptions concerning boundary conditions and modeling strategy are discussed with regard to the identified slight discrepancies. The possibility to extend the finite element model to represent the O-ring seal’s ability to recover after a (fast) partial release is taken into account. T2 - ASME 2020 Pressure Vessels & Piping Conference (PVP2020) CY - Online meeting DA - 03.08.2020 KW - Compression Set KW - O-ring KW - Simulation KW - Sequential analysis KW - Ageing KW - stress relaxation PY - 2020 SN - 978-0-7918-8388-4 U6 - https://doi.org/10.1115/PVP2020-21270 SP - PVP2020-21270 PB - ASME AN - OPUS4-51490 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schmidt, Wolfram A1 - Olonade, K. A. A1 - Mbugua, R. N. A1 - Lenz, F. J. A1 - Tchetgnia Ngassam, I. T1 - Bio-Based Rheology Modifiers for High Performance Concrete – Possible Modes of Actions and Case Study for Cassava Starch in West Africa N2 - Polymers that help tailoring rheological properties during the casting process have become inevitable constituents for all kinds of high-performance concrete technologies. Due to lacking industries, these typically crude-oil based admixtures are not readily available in many parts of the world, which limits the implementation of more sustainable high-performance construction technologies in these regions. Alternative polymers, which often demand for less processing, can be derived from local plant-based resources. The paper provides experimental data of flow tests of cement pastes with polysaccharides from Triumfetta pendrata A. Rich, acacia gum and cassava without and in the presence of polycarboxylate ether superplasticizer. The flow tests are amended by observations of the zeta potentials and the hydrodynamic diameters in the presence of and without calcium ions in the dispersion medium. The results show that in the presence of and without calcium ions all polysaccharides provide negative zeta potentials, yet, they affect flowability and thixotropy in different ways. Cassava starch, acacia gum, and the gum of Triumfetta pendrata A. Rich qualified well for robustness improvement, strong stiffening, and additive manufacturing, respectively. The reason for the different effects can be found in their average sizes and size distribution. Due to the promising results, a flow chart for local value chains is derived on the example of yet unused cassava wastes, which can be converted in parallel. T2 - 3rd International Conference on the Application of Superabsorbent Polymers CY - Skukuza, South Africa KW - Admixtures KW - Polysaccharides KW - Rheology KW - Thixotropy KW - Concrete PY - 2020 SN - 978-3-030-33341-6 SN - 978-3-030-33342-3 U6 - https://doi.org/10.1007/978-3-030-33342-3_17 SP - 158 EP - 166 PB - Springer AN - OPUS4-58404 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Scheuschner, Nils A1 - Altenburg, Simon A1 - Straße, Anne A1 - Gumenyuk, Andrey A1 - Maierhofer, Christiane T1 - In-situ thermographic monitoring of the laser metal deposition process N2 - In this paper shortwave infrared (SWIR) thermographic measurements of the manufacturing of thin single-line walls via laser metal deposition (LMD) are presented. As the thermographic camera is mounted fixed to the welding arm, an acceleration sensor was used to assist in reconstructing the spatial position from the predefined welding path. Hereby we could obtain data sets containing the size of the molten pool and the oxide covered areas as functions of the position in the workpiece. Furthermore, the influence of the acquisition wavelength onto the thermograms was investigated in a spectral range from 1250 nm to 1550 nm. All wavelengths turned out to be usable for the in-situ process monitoring of the LMD process. The longer wavelengths are shown to be beneficial for the lower temperature range, while shorter wavelengths show more details within the molten pool. T2 - Sim-AM 2019 - 2. International Conference on Simulation for Additive Manufacturing CY - Pavia, Italy DA - 11.09.2019 KW - Additive manufacturing KW - 3D printing KW - Thermography KW - Direct energy deposition KW - Laser Metal Deposition KW - 3D Druck KW - Laser Pulver Auftragsschweißen KW - Additive Fertigung KW - Thermografie PY - 2019 UR - http://congress.cimne.com/SIM-AM2019/frontal/Doc/proceedings.pdf SN - 978-84-949194-8-0 SP - 246 EP - 255 AN - OPUS4-49086 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Legall, Herbert A1 - Schwanke, Christoph A1 - Bonse, Jörn A1 - Krüger, Jörg T1 - X-ray emission during ultrashort pulse laser processing N2 - The industrial use of ultrashort laser pulses has made considerable progress in recent years. The reasons for this lie in the availability of high average powers at pulse repetition rates in the several 100 kHz range. The advantages of using ultrashort laser pulses in terms of processing precision can thus be fully exploited. However, high laser intensities on the workpiece can also lead to the generation of unwanted X-rays. Even if the emitted X-ray dose per pulse is low, the accumulated X-ray dose can become significant for high-repetition-rate laser systems so that X-ray exposure safety limits must be considered. The X-ray emission during ultrashort pulse laser processing was investigated for a pulse duration of 925 fs at 1030 nm wavelength and 400 kHz repetition rate. Industrially relevant materials such as steel,aluminum and glass were treated. Tungsten served as reference. X-ray spectra were recorded, and X-ray dose measurements were performed for laser treatment in air. For laser intensities > 2 × 10^13 W/cm2, X-ray doses exceeding the regulatory exposure limits for members of the public were found. Suitable X-ray protection strategies are proposed. T2 - SPIE Photonics West CY - San Francisco, USA DA - 02.02.2019 KW - Laser-induced X-ray emission KW - Ultrashort laser material interaction KW - Radiation protection PY - 2019 SN - 978-1-5106-2459-7 U6 - https://doi.org/10.1117/12.2516165 SN - 0277-786X SN - 1996-756X VL - 10908 SP - 1090802-1 EP - 1090802-7 PB - SPIE - The international society for optics and photonics CY - Bellingham, WA, USA AN - OPUS4-47510 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -