TY - JOUR A1 - Strommer, Bettina A1 - Schulze, Dietmar A1 - Schartel, Bernhard A1 - Böhning, Martin T1 - The quantification of anisotropy in graphene/natural rubber nanocomposites: Evaluation of the aspect ratio, concentration, and crosslinking N2 - In the processing of nanocomposites, high shear stresses at elevated tempera-tures orient two-dimensional nanoparticles like graphene. This orientationleads to anisotropic mechanical, thermal or barrier properties of the nanocom-posite. This anisotropy is addressed in this study by comparing graphene (few-layer graphene, FLG) with a nanoscaled carbon black (nCB) at a filler contentof 3 phr, by varying the vulcanization, and by comparing different FLG con-tents. Transmission electron microscopy gives insight into the qualitative ori-entation in the nanocomposite with FLG or nCB. The storage moduli paralleland normal to the orientation reveal the direction dependency of reinforce-ment through dynamic mechanical analysis (DMA). Dimensional swellingmeasurements show a restriction of the expansion parallel to the FLG orienta-tion, and an increased expansion normal to the orientation. The vulcanizationsystem and crosslinking determine the respective level of property values, andhigher crosslinking densities increase the anisotropy in DMA resulting invalues of up to 2.9 for the quantified anisotropy factor. With increasing FLGcontent, the anisotropy increases. A comparison of the results reveals swellingmeasurements as the most suitable method for the determination of anisot-ropy. Compared to recent literature, the presented processing induces higheranisotropy, leading to higher reinforcing effects in the direction of orientation KW - Natural rubber KW - Graphene KW - Nanocomposite KW - Mechanical properties KW - Swelling PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-571522 DO - https://doi.org/10.1002/app.53753 SN - 1097-4628 VL - 140 IS - 16 SP - 1 EP - 15 PB - Wiley online library CY - Hoboken, New Jersey (USA) AN - OPUS4-57152 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Emamverdi, Farnaz A1 - Huang, J. A1 - Szymoniak, Paulina A1 - Bojdys, M. J. A1 - Böhning, Martin A1 - Schönhals, Andreas T1 - Structure and molecular mobility of phosphinine-based covalent organic frameworks – glass transition of amorphous COFs N2 - Two-dimensional covalent organic frameworks (COFs) based on phosphinine and thiophene building blocks have been synthesized with two different side groups. The materials are denoted as CPSF-MeO and CPSF-EtO where CxxF correspond to the covalent framework, whereas P and S are related to heteroatoms phosphorous and sulfur. MeO and EtO indicate the substituents, i.e. methoxy and ethoxy. Their morphologies were studied by scanning electron microcopy and X-ray scattering. The absence of crystalline reflexes in the X-ray pattern reveal that both materials are amorphous and can be considered as glasses. Furthermore, N2 adsorption measurements indicate substantial Brunauer–Emmett–Teller (BET) surface area values pointing to the formation of three-dimensional pores by stacking of the aromatic 2D layer. An analysis of the porosity of both COFs showed a mean radius of the pores to be of ca. 4 nm, consistent with their chemical structure. The COFs form nanoparticles with a radius of around 100 nm. The thermal behavior of the COFs was further investigated by fast scanning calorimetry. These investigations showed that both COFs undergo a glass transition. The glass transition temperature of CPSF-EtO is found to be ca. 100 K higher than that for CPSF-MeO. This large difference in the glass transition is discussed to be due to a change in the interaction of the COF sheets induced by the longer ethoxy group. It might be assumed that for CPSF-EtO more individual COF sheets assemble to larger stacks than for CPSF-MeO. This agrees with the much larger surface area value found for CPSF-EtO compared to CPSF-MeO. To corroborate the results obtained be fast scanning calorimetry dielectric measurements were conducted which confirm the occurrence of a dynamic glass transition. The estimated temperature dependence of the relaxation rates of the dielectric relaxation and their absolute values agrees well with the data obtained by fast scanning calorimetry. Considering the fragility approach to the glass transition, it was further found that CPSF-MeO is a fragile glass former whereas CPSF-EtO behaves as a strong glass forming material. This difference in the fragility points also to distinct differences in the interaction between the 2D COF molecules in both materials. KW - Covalent Organic frameworks PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-596770 DO - https://doi.org/10.1039/d3ma01123b SP - 1 EP - 10 PB - Royal Society of Chemistry (RSC) AN - OPUS4-59677 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kemmler, Samuel A1 - Cuéllar, Pablo A1 - Artinov, Antoni A1 - Luu, Li-Hua A1 - Farhat, Abbas A1 - Philippe, Pierre A1 - Rettinger, Christoph A1 - Köstler, Harald T1 - A fully-resolved micromechanical simulation of piping erosion during a suction bucket installation N2 - Granular fluidization phenomena such as piping erosion represent a challenge to the delicate installation process of offshore suction bucket foundations. A detailed analysis of the complex conditions in terms of soil composition, soil state, and foundation installation parameters that may lead to piping can be very demanding, if at all possible, solely by experimental means or using macroscopic continuum-based seabed models. The present paper presents a fully-resolved fluid-coupled micromechanical approach for a three-dimensional numerical simulation of the installation process of a suction bucket using the lattice Boltzmann method and discrete element method. The developed model is validated using well-established benchmarks and calibrated by means of experimental data from physical model tests on relevant scenarios focusing on the local fluidization of fixed embedded suction buckets as well as on the suction-driven installation of unrestrained buckets. The qualitative and quantitative agreement with the experimental data both endorse the proposed methodology and highlight the physical soundness of the obtained results. Thereby, the paper shows that three-dimensional analyses of relevant local scenarios at a real scale with little macromechanical model assumptions are feasible. KW - Micromechanical simulation KW - Fluid–solid coupling KW - Piping erosion KW - Suction bucket foundation KW - Offshore wind support structure KW - High-performance computing PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-633790 DO - https://doi.org/10.1016/j.compgeo.2025.107375 SN - 0266-352X VL - 186 SP - 1 EP - 17 PB - Elsevier B.V. AN - OPUS4-63379 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rappsilber, Tim A1 - Krüger, Simone A1 - Raspe, Tina A1 - Wagner, Patrick A1 - Liebner, Christian A1 - Strzyz, Thaddeus A1 - Tschirschwitz, Rico T1 - Hazard classification of different lithium-ion battery types after triggering thermal runaway N2 - For a better understanding of relevant parameters influencing the thermal runaway, this work classifies the behavior of six different types of lithium-ion batteries. Based on 145 repeatable tests, this research has created a unique and detailed database of battery behavior during thermal runaway. It contains information about changes in cell temperature, voltage, mass loss, smoke gas release and gas pressure. When it comes to characterizing the thermal runaway behavior across different cell types, this work eliminates the need for complex meta-analyses, which can only provide limited information due to the different test conditions in different test benches. In a pressure-resistant 100 dm³ autoclave and an 8-m³ room with connected multi gas analysis, 24 setups were examined under identical conditions. The investigations were carried out as a function of the variation parameters cell geometry, cathode active material, state of charge and initiation method of thermal runaway. The analysis of the measurement data reveals clear differences in the thermal runaway behavior of the tested cell types and can be used as a reference for determining the hazard potential in individual assessment categories of different cells. All measured values from both test benches as well as the visual evaluation of the cell behavior during the test runs in the 8 m³ room are made available in a comprehensive data table in the supplementary material. KW - Lithium Ion KW - Thermal Runaway KW - State of charge KW - Hazard classification KW - gas emission PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-634429 DO - https://doi.org/10.1016/j.jlp.2025.105691 SN - 0950-4230 VL - 97 SP - 1 EP - 15 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-63442 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schwarz, W. A1 - Wilsch, Gerd A1 - Katsumi, N. A1 - Ebell, Gino A1 - Völker, Tobias T1 - Ion distribution in concrete overlay, mapped by laser induced breakdown spectroscopy (LIBS), modified by an embedded zinc anode N2 - Galvanic corrosion protection by embedded zinc anodes is an accepted technique for the corrosion protection of reinforcing steel in concrete. Galvanic currents flow between the zinc anode and the steel reinforcement due to the potential difference that is in the range of a few hundred mV. The ion distribution was studied on two steel reinforced concrete specimens admixed with 3 wt.% chloride/wt. cement and galvanically protected by a surface applied EZ-anode. On both specimens, a zinc anode was embedded and glued to the concrete surface by a geo-polymer-based chloride-free binder. At one specimen, the EZ-anode was operated for 2,5 years, the EZ-anode at the other specimen was not electrically connected to the reinforcement, this specimen serves as a reference. Both specimens have been stored under identical conditions. The ion distribution between the anode (EZ-ANODE) and cathode (steel reinforcement) was studied by laser-induced breakdown spectroscopy (LIBS) after 7 months, 12 months, and 2,5 years. Results of the LIBS studies on the specimen with activated EZ-anode after 7 months, 12 months, and 2,5 years and of the reference specimen after 2,5 years are reported. Results show that diffusion of ions contributes to the changes in the ion distribution but migration, especially of chlorides towards the EZ-anode is significant despite the weak electric field – several hundred millivolts - generated by the galvanic current. Results show that chloride ions accumulate near the zinc-anode as in water-insoluble zinc-hydroxy chlorides - Simonkollite. T2 - ICCRRR 2022 CY - Capetown, South Africa KW - Corrosion KW - LIBS KW - Zinc KW - Anode PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-560576 DO - https://doi.org/10.1051/matecconf/202236404023 SN - 2261-236X VL - 364 SP - 1 EP - 7 PB - EDP Sciences CY - Les Ulis AN - OPUS4-56057 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heyn, A. A1 - Meist, M. A1 - Michael, O. A1 - Babutzka, M. A1 - Valet, Svenja A1 - Ebell, Gino T1 - Electrochemical characterization of surfaces of galvanized steels under different exposure conditions using gel electrolytes N2 - The corrosion behavior of galvanized steels and zinc components under atmospheric exposure depends mostly on the corrosion product‐based cover layer formation under the prevailing conditions. The use of agar‐based gel electrolytes makes it possible to use electrochemical methods to obtain a characteristic value from these cover layers that describe their current and future protective capacity. It is shown here that different states of galvanized steel can be distinguished very well under laboratory conditions and that this method is also suitable for use under practical conditions. Based on the characteristic values and assuming future time of wetness, it is very easy to draw up a forecast for the future corrosion rate, which provides plausible values. KW - Materials Chemistry KW - Metals and Alloys KW - Surfaces, Coatings and Films KW - Mechanical Engineering KW - Mechanics of Materials KW - Environmental Chemistry KW - Corrosion KW - Znc PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-599234 DO - https://doi.org/10.1002/maco.202414389 SP - 1 EP - 16 PB - Wiley VHC-Verlag AN - OPUS4-59923 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Boschmann Käthler, C. A1 - Ebell, Gino A1 - Keßler, S. A1 - Schiegg, Y. A1 - Dauberschmidt, C. A1 - Angst, U. M. T1 - A comparison of methods to assess the resistance of reinforcing steel against chloride‐induced corrosion in concrete - Particular consideration of 12% chromium steel N2 - The critical chloride content Ccrit is an indicator of the corrosion resistance of reinforcing steels in concrete. In this article, several experimental methods for determining the critical chloride content Ccrit of mild and alloyed (12% Cr) steel in cementitious materials are compared. The methods used include accelerated polarization tests and tests employing more natural (unpolarized) conditions in which chloride ingress occurs by diffusion and capillary uptake. The advantages and disadvantages of the methods are discussed, in particular, against the objective of reaching a compromise between applicability to practice and feasibility in laboratory testing. KW - Chloride‐induced corrosion KW - Critical chloride content KW - Reinforced concrete KW - Testing methods PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-628485 DO - https://doi.org/10.1002/maco.202112826 SN - 0947-5117 VL - 73 IS - 3 SP - 306 EP - 325 PB - Wiley-VCH CY - Weinheim AN - OPUS4-62848 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ebell, Gino A1 - Tannert, S. A1 - Lehmann, Jens A1 - Müller, H. T1 - Offshore Weathering Campaign on a North Sea Wind Farm Part One: Corrosivity Categories N2 - The aim of this study is to investigate the corrosion behavior of materials and coatings in offshore environments, with a focus on determining the corrosivity categories at different locations on wind turbines. The collaboration between the authors enabled a 3‐year weathering campaign at the Hohe See and Albatros offshore wind farms in the North Sea. Metal panels were installed on two wind turbines to assess the corrosivity of different atmospheric conditions. Preliminary results indicate significant variations in corrosivity depending on location and material used, suggesting that current standards may not fully reflect real‐world conditions. The results of the study will help to optimize material selection and corrosion protection strategies for offshore wind farms, potentially extending their lifetime and reducing operating costs. KW - Corrosion KW - Offshore KW - Wind PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-628995 DO - https://doi.org/10.1002/maco.202414711 SN - 1521-4176 SP - 1 EP - 10 PB - Wiley CY - Weinheim AN - OPUS4-62899 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schnell, Alexander A1 - Rübner, Katrin A1 - Seher, Julia A1 - Müller, Constanze A1 - Müller, Anette A1 - Liebezeit, Steffen A1 - Fenner, Jacob A1 - Martin, Falk A1 - Pniok, Nicole T1 - Manufacturing and Application of Lightweight Aggregates from Construction and Demolition Waste N2 - The objective of the REALight project is the development of a thermal process to produce lightweight aggregates in pilot scale and the implantation of a method to recover gypsum. Beside construction and demolition waste, various industrial by‐products are studied as raw materials. The raw materials have so far been unused or used in applications with lower quality requirements. To prove the performance of the lightweight aggregates, their technical properties are tested and their use in different applications is studied, e.g., for lightweight mortars as well as lightweight concretes. KW - Construction and demolition waste KW - Flue gas desulfurization gypsum KW - Industrial by-products KW - Infra-lightweight concrete KW - Lightweight aggregates PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-604643 DO - https://doi.org/10.1002/cite.202300211 SN - 0009-286X VL - 96 IS - 7 SP - 969 EP - 975 PB - Wiley-VCH GmbH CY - Weinheim AN - OPUS4-60464 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Robens-Radermacher, Annika A1 - Kujath, Cezary A1 - Bos, Freek A1 - Mechtcherine, Viktor A1 - Unger, Jörg F. T1 - Mechanical properties of 3D printed concrete: a RILEM TC 304-ADC interlaboratory study-Design and implementation of a database system for querying, sharing, and analyzing experimental data N2 - Interlaboratory studies are essential for implementing standardized test methods for new innovative materials or technologies such as 3D concrete printing, certifying reference materials, and validating methods. They provide the basis for recommendations and design standards. Typically, the collected data are used only for one study and are published in paper form, without open access to the raw data files. However, preserving the collected data and analysis procedures in a shareable and reusable way leads to advantages for further usage. New data with the same structure can be added or the data can be analyzed by a new analysis procedure generating new knowledge. Additionally, resources are saved by avoiding the repetition of the same measurements. In line with the recent digitalization trend in material science and engineering, a database for the interlaboratory study on mechanical properties of 3D printed concrete conducted in RILEM Technical Committee 304-ADC is established. The challenges and experiences from defining the data structure, uploading the data, and using the database for evaluations are discussed. The openBIS software is used to create and fill the database, while an export method to an SQLite format is developed and discussed to generate a shareable and reusable database. With the exported database, querying the data is possible independently of a particular data management system. Additionally, examples of data processing with reusable workflows automating the analysis procedure are demonstrated. KW - Data management KW - Interlaboratory study KW - 3D concrete printing KW - Database KW - Reusability PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-634627 DO - https://doi.org/10.1617/s11527-025-02650-9 SN - 1871-6873 VL - 58 IS - 184 SP - 1 EP - 37 PB - Springer Nature AN - OPUS4-63462 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -