TY - CONF A1 - Sturm, Heinz T1 - Modulated Lateral Force Microscopy: An AFM tool for Analysis and Modification of Polymer T2 - German-Russian Workshop "Contact Mechanics and Friction" CY - Berlin, Germany DA - 2009-10-05 PY - 2009 AN - OPUS4-20751 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Methoden der Rasterelektronen- und Rasterkraftmikroskopie zur Analyse von Faserverbundwerkstoffen T2 - 15. Nationales Symposium SAMPE Deutschland e.V. CY - Berlin, Germany DA - 2009-02-18 PY - 2009 AN - OPUS4-20750 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Using a SFM/ESEM hybrid for the analysis of vibrating surfaces T2 - MC 2009 Microscopy Conference CY - Graz, Austria DA - 2009-08-30 PY - 2009 AN - OPUS4-20706 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Henrichsen, H. A1 - Sturm, Heinz A1 - Boggild, P. A1 - Hansen, O. T1 - Submicron organic nanofiber devices with different anode-cathode materials: A simple approach N2 - The authors present a simple general method for simultaneously producing tens of submicron electrode gaps with different cathode and anode materials on top of nanofibers, nanowires, and nanotubes, with an optional gap size variation. Using this method, an ensemble of para-hexaphenylene (p6P) nanofiber devices of different length was fabricated with Sm and Au electrodes. The measured I-V characteristics are in agreement with a nonlinear hopping transport model, where domain barriers dominate the transport with an estimated domain size of 23±5 nm. KW - Nanofibers KW - Sub-micron electrode KW - Para-hexaphenylene KW - Samarium KW - Gold KW - I/V-characteristics KW - Nanolasers KW - Domain barriers PY - 2010 DO - https://doi.org/10.1116/1.3431088 SN - 1071-1023 SN - 0734-211X VL - 28 IS - 3 SP - 617 EP - 622 PB - American Institute of Physics CY - New York, NY AN - OPUS4-21573 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz A1 - Bonse, Jörn A1 - Wiggins, S. M. A1 - Solis, J. A1 - Lippert, Th. T1 - Dynamics of phase transitions in polymer thin films upon single femtosecond laser pulse irradiation T2 - Second International Conference on Photo-Induced Phase Transitions Cooperative, non-linear and functional properties CY - Rennes, France DA - 2005-05-24 PY - 2005 AN - OPUS4-7430 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz A1 - Cappella, Brunero T1 - Dynamic Plowing Lithography of Polymer Surfaces T2 - Workshop "Scanning Probe Microscopy in the New Millennium" CY - Faure, South Africa DA - 2001-02-26 PY - 2001 AN - OPUS4-7512 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sturm, Heinz A1 - Heyde, M. A1 - Rademann, K. T1 - Measuring SPM Piezo Displacement Responses PY - 1999 SN - 1551-9295 VL - 99 IS - 4 SP - 24 EP - 26 PB - Microscopy Society of America CY - Wappingers Falls, NY AN - OPUS4-6860 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Friction-induced explosive reactions N2 - The motivation to examine the influence of friction on surfaces of energetic materials (EM) has diverse backgrounds. On the one hand the very old hot spot theory predicts, that the size of such hot spot could be in the range of a molecule. The initiation of an EM could start by mechanical excitation, i.e. friction, and continues driven by an exothermal chemical reaction. Following such phenomena on the molecular scale with an imaging method such as AFM should enable us to separate several steps of ignition, if there are any. The experiments showed that HMX mainly undergoes a plastic deformation without further consequences. TNP however showed self healing in the wear track after scratching and simultaneously the destruction of a crystal edge outside the wear track. Additionally nanoparticles appear, tribologists call this "third body formation", which are proven to have a different chemical composition as the original TNP. The self healing effect on the surface is verified with experiments on self diffusion of TNP molecules to and fro the free edges of the crystal. The conclusion is that the formation of a hot spot can be shown to consist of several subsequent steps, separated temporally and locally. The goal to excite the thermal decomposition of a whole TNP crystal (nanoexplosion) was yet not reached due to unfavourable conditions related to thermal conductivity and build-up of pressure. T2 - Role of Third Bodies in Tribology, Colloquium of 5.1 CY - BAM, Berlin, Germany DA - 09.06.2016 KW - AFM KW - Energetic material KW - Hot spot KW - Friction PY - 2016 AN - OPUS4-36433 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Rhiem, S. A1 - Barthel, Anne-Kathrin A1 - Meyer-Plath, A. A1 - Hennig, M. P. A1 - Wachtendorf, Volker A1 - Sturm, Heinz A1 - Schäffer, A. A1 - Maes, H. M. T1 - Release of 14C-labelled carbon nanotubes from polycarbonate composites N2 - Waste disposal of carbon nanotube (CNT) containing products is expected to be the most important pathway for release of CNTs into the environment. In the present work, the use of radiolabelled CNTs (14C-CNT) for polycarbonate polymer nanocomposites with 1 wt% 14C-CNT content allowed for the first time to quantify and differentiate the CNT release according to the type of impact along the materials' ageing history. After an initial exposure of the nanocomposite by solar-like irradiation, further environmental impacts were applied to composite material. They aimed at mimicking disposal site conditions that may induce further ageing effects and CNT release. This study included shaking in water, rapid temperature changes, soaking in humic acid solution as well as waste water effluent, and, finally, gentle mechanical abrasion. All ageing impacts were applied sequentially, both on pristine (control) and on solar-irradiated nanocomposites. All experiments were accompanied by absolute quantification of radioactive release as well as chemical and morphological analyses of the nanocomposite surfaces using infra-red (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The morphological analysis showed that spectral irradiation can uncover CNT networks on the outer nanocomposite surface layers by polymer degradation. After having subjected the solar-irradiated nanocomposite to all studied disposal site effect, the total radioactive release was quantified to amount to 64 mg CNT/m2, whereas only 0.8 mg CNT/m2 were found for the un-irradiated control sample. Solar degradation of polymers was thus found to significantly increase the propensity of the studied polymer nanocomposites to release CNTs during ageing effects at the product's end-of-life typical for disposal sites. KW - Weathering KW - Carbon nanotubes KW - Nanocomposites KW - Release KW - Quantification PY - 2016 UR - http://www.sciencedirect.com/science/article/pii/S0269749116303748 DO - https://doi.org/10.1016/j.envpol.2016.04.098 SN - 0269-7491 VL - 215 IS - August SP - 356 EP - 365 PB - Elsevier Ltd. CY - Paris AN - OPUS4-36899 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Fritzsche, Sven A1 - Pauw, Brian Richard A1 - Weimann, Christiane A1 - Sturm, Heinz T1 - Test artifact for fs-LDW N2 - Data to generate the given graphs in the publication as well as raw images of the shown images. KW - stl code KW - Images KW - Graphs KW - Data PY - 2023 DO - https://doi.org/10.5281/zenodo.7671945 PB - Zenodo CY - Geneva AN - OPUS4-58096 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz A1 - Ghasem Zadeh Khorasani, Media A1 - Silbernagl, Dorothee T1 - Grenzflächen als Material: Konzepte und Beispiele zu nanoverstärkten Duroplasten N2 - Nachdem Jahrzehnte die Grenzfläche zwischen Kohlefaser und Duroplastmatrix optimiert wurde liegt das Augenmerk heute auf der Polymermatrix selbst. Diese lässt sich hinsichtlich ihres Elastizitätsmoduls und ihrer Bruchfestigkeit verbessern, indem Nanopartikel aus Böhmit (AlOOH) eindispergiert werden. Der Vortrag geht auf integrale und hochauflösend-bildgebende Methoden ein die ein Verständnis der komplexen Zusammenhänge ermöglichen. Nach einer chemischen in-situ Analyse des Aushärtvorgangs, aus welchem sich die Bedeutung der externer Parameter ablesen lässt, werden diverse hochauflösende, neue Methoden der Rasterkraftmikroskopie (AFM) eingeführt. Der lokalen Bestimmung des E-Moduls der Nanopartikel folgen Ausführungen zum temperaturabhängigen Chemismus des Böhmits, der während der Aushärtung Wasser freisetzt. Die hochauflösende Bestimmung der Oberflächenpotentiale, der Steifigkeit, der attraktiven Kräfte zwischen Spitze und Probe sowie der Energiedissipation im Kontakt stellen auf der Nanoskala eine komplexe Datenquelle dar, die auf der Makroskala einer Ergänzung bedarf: Durch Kombination von dynamisch-mechanisch-thermischer Analyse einerseits und Kartierung physikalischer Eigenschaften auf der Nanoskala andererseits kann der Zusammenhang zwischen chemischer Steuerung der Netzwerkbildung und den mechanischen Eigenschaften des Nanokomposits geklärt werden. Überraschend ist, dass bei geeigneter Steuerung der lokale E-Modul der Polymermatrix den des Füllstoffs übersteigt. Die Rissfortschrittsenergie wird in Böhmit-modifiziertem Epoxy verbessert absorbiert, die These dazu ist, dass die (010)-Gleitebenen, die nur durch Wasserstoffbrücken zusammen gehalten werden, einigermaßen schadlos geschert werden können. Daraus folgt, dass das System auf der Nanoskala über einen, wenn auch begrenzten, Selbstheilmechanismus verfügt. Zudem wird durch die hohe Heterogenität der Steifigkeit und Energiedissipation des Nanokomposits eine Risstrajektorie vielfach umgelenkt und somit früher gestoppt. Ergebnisse dieses Vortrags stammen aus einer Zusammenarbeit innerhalb des DFG-Forscherverbundes FOR2021 „Wirkprinzipien nanoskaliger Matrixadditive für den Faserverbundleichtbau“. T2 - Niedersächsisches Symposium Materialtechnik - NSM 2019 CY - Clausthal, Germany DA - 14.02.1019 KW - Nanokomposit KW - Böhmit KW - Risstrajektorie KW - Oberflächenpotential KW - Energiedissipation im Kontakt KW - Oberflächensteifigkeit KW - attraktive Wechelwirkung KW - Epoxy-Anhydrid Duroplast KW - Leichtbau PY - 2019 AN - OPUS4-47636 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Morys, Michael A1 - Illerhaus, Bernhard A1 - Sturm, Heinz A1 - Schartel, Bernhard T1 - Size is not all that matters: Residue thickness and protection performance of intumescent coatings made from different binders N2 - In addition to the acid source, charring agent, and blowing agent, the binder is a crucial part of an intumescent coating. Its primary task is to bind all compounds, but it also acts as a carbon source and influences the foaming process. A series of intumescent coatings based on five different binders was investigated in terms of insulation, foaming, mechanical impact resistance, and residue morphology. The Standard Time-Temperature modified Muffle Furnace (STT MuFu+ ) was used for the bench-scale fire resistance tests and provided data on temperature and residue thickness as well as well-defined residues. The residue morphology was analyzed by nondestructive m-computed tomography and scanning electron microscopy. A moderate influence of the binder on insulation performance was detected in the set of coatings investigated, whereas the foaming dynamics and thickness achieved were affected strongly. In addition, the inner structure of the residues showed a rich variety. High expansion alone did not guarantee good insulation. Furthermore, attention was paid to the relation between the microstructure transition induced by carbon loss due to thermo-oxidation of the char and the development of the thermal conductivity and thickness of the coatings during the fire test. KW - Intumescence KW - Morphology analysis KW - Computed tomography KW - Fire resistance KW - Bench-scale fire test KW - Fire protective coating PY - 2017 DO - https://doi.org/10.1177/0734904117709479 SN - 0734-9041 SN - 1530-8049 VL - 35 IS - 4 SP - 284 EP - 302 PB - Sage AN - OPUS4-40766 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Morys, Michael A1 - Illerhaus, Bernhard A1 - Sturm, Heinz A1 - Schartel, Bernhard T1 - Revealing the inner secrets of intumescence: Advanced standard time temperature oven (STT Mufu+)—my‐computed tomography approach N2 - Intumescent coatings have been used for fire protection of steel for decades, but there is still a need for improvement and adaptation. The key parameters of such coatings in a fire Scenario are thermal insulation, foaming dynamics, and cohesion. The fire resistance tests, large furnaces applying the standard time temperature (STT) curve, demand coated full‐scale components or intermediate‐scale specimen. The STT Mufu+ (standard time temperature muffle furnace+) approach is presented. It is a recently developed bench‐scale testing method to analyze the performance of intumescent coatings. The STT Mufu+ provides vertical testing of specimens with reduced specimen size according to the STT curve. During the experiment, the foaming process is observed with a high‐temperature endoscope. Characteristics of this technique like reproducibility and resolution are presented and discussed. The STT Mufu+ test is highly efficient in comparison to common tests because of the reduced sample size. Its potential is extended to a superior research tool by combining it with advanced residue analysis (μ‐computed tomography and scanning electron microscopy) and mechanical testing. The benefits of this combination are demonstrated by a case study on 4 intumescent coatings. The evaluation of all collected data is used to create performance‐based rankings of the tested coatings. KW - Bench‐scale fire testing KW - Computed tomography KW - Fire resistance KW - Intumescence KW - Residue analysis KW - Standard time temperature furnace PY - 2017 DO - https://doi.org/10.1002/fam.2426 SN - 0308-0501 SN - 1099-1018 VL - 41 IS - 8 SP - 927 EP - 939 PB - Wiley AN - OPUS4-42754 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz A1 - Braun, Ulrike T1 - Kunststoffe und deren Recycling – Materialwissenschaftliche Erkenntnisse, um mehr Recyclat einzusetzen N2 - Nach einer Übersicht zu den immer schneller aktualisierenden Rahmenbedingungen von Politik und Gesellschaft folgt eine Übersicht zu materialwissenschaftlichen Problemen des Recyclings von Kunststoffen. Lösungsansätze aus der Forschung reichen von einfacher Optimierung bis hin zur radikalen Neukonstruktion der polymeren Werkstoffe. Aus dem bereits möglichen Ansatz "performance-by-design" wird ein neuer Weg des "recycling-by-design" adressiert. Dies inkludiert methodisch eine skalenübergreifende Modellierung und die Depolarisation bis zum Monomer. T2 - Gefahrgut-Technik-Tage CY - Berlin, Germany DA - 07.11.2019 KW - Recycling KW - Kunststoff KW - Additiv KW - Polymer KW - Normung KW - Plastikstrategie KW - Grenzfläche als Material KW - Recycling-by-design PY - 2019 AN - OPUS4-49561 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz A1 - Altmann, Korinna A1 - Braun, Ulrike T1 - Notwendigkeit von (Realistischen) Referenzmaterialien N2 - Die Herstellung von Mikroplastik Referenzmaterialien wird vorgestellt. T2 - Statusfonferenz der BMBF Fördermassnahme "Plastik in der Umwelt" CY - Berlin, Germany DA - 09.04.2019 KW - Ringversuch KW - Mikroplastik KW - Referenzmaterialien PY - 2019 AN - OPUS4-47798 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Morys, Michael A1 - Illerhaus, Bernhard A1 - Sturm, Heinz A1 - Schartel, Bernhard T1 - Variation of intumescent coatings revealing different modes of action for good protection performance N2 - Thermal insulation and mechanical resistance play a crucial role for the performance of an intumescent coating. Both properties depend strongly on the morphology and morphological development of the foamed residue. Small amounts (4 wt%) of fiberglass, clay and a copper salt, respectively, are incorporated into an intumescent coating to study their influence on the morphology and Performance of the residues. The bench scale fire tests were performed on 75 x 75 x 2 mm³ coated steel plates according to the standard time–temperature curve in the Standard Time Temperature Muffle Furnace+ (STT Mufu+). It provided information about foaming dynamics (expansion rates) and thermal insulation. Adding the copper salt halved the expansion height, whereas the clay and fiberglass Change the height of the residue only moderately. The time to reach 500 °C was improved by 31% for clay and 15% for the other two fillers. Nondestructive micro computed tomography is used to assess the inner structure of the residues. A transition of the residue from a black, carbonaceous foam with closed cells into an inorganic, residual open cell sponge occurs at high temperatures. This transition is due to a loss of carbon; the change in microstructure is analyzed by scanning electron microscopy. Additional mechanical tests are performed and interpreted with respect to the results of the morphology analysis. Adding clay or copper salt improved the mechanical resistance tested by a factor 4. The additives significantly influence the thickness and foaming Dynamics as well as the inner structure of the residues, whereas their influence on insulation Performance is moderate. In conclusion, different modes of action are observed to achieve similar insulation performance during the fire test. KW - Intumescence KW - Coating KW - Bench scale fire testing KW - Computed tomography KW - Fire resistance PY - 2017 DO - https://doi.org/10.1007/s10694-017-0649-z SN - 0015-2684 SN - 1572-8099 VL - 53 IS - 4 SP - 1569 EP - 1587 PB - Springer AN - OPUS4-40751 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dittrich, Maria A1 - Paulo, Carlos A1 - Knabe, Nicole A1 - Sturm, Heinz A1 - Zaitsev, Vladimir A1 - Gorbushina, Anna T1 - Microscopic Raman study of fungal pigment using the genetically amenable rock inhabitant Knufia petricola as a model organism N2 - Fungal pigments such as melanin and carotenoids are distinctive markers of animal and plant pathogenic fungi as well as their environmental relatives. These complex pigments play important roles in pathogenicity and stress tolerance while also being useful as biomarkers. Accordingly, it is important to be able to identify in situ the pigments in black fungi, a group of clinical and environmental importance. In this study, wild-type and genetically modified strains of Knufia petricola A95 and wild fungal cells attached to ancient rock were investigated for their spectroscopic and microscopic Raman features and morphological appearance. Knockout mutants of melanin synthesis genes pks1 (polyketide synthase), sdh1 (scytalone dehydratase), and both pks1 and the carotenoid synthesis gene phd1 (phytoene desaturase) were studied We applied two different Raman microscopes using two lasers, with 633 nm and 488 nm wavelengths. We analyzed and compared Raman spectra between the measured reference substances and the mutant and wild-type strains. In the wild strain WT:A95, the peaks close to melanin peals were found at 1353 cm−1 and 1611 cm−1. There are no characteristic melanin peaks at 1580–1600 cm−1 and around 1350 cm−1 at the spectrum of the Δpks1/Δphd1 mutant and the Δsdh1 mutant. The Δpks1 mutant spectrum has the peaks at the beta-carotene v2 C-C in-plane stretch at 1155 cm−1 and v3 C-CH3 deformation at 1005 cm−1. The peaks of carotenoids and melanin were found in all mutants and the wild strain, except the Δpks1/Δphd1 mutant. Raman spectra allow for discrimination between the various pigments. Hence, interactions between natural fungal melanin, as well as other protective pigments, and complex environmental matrices can be characterized on a range of spatial and temporal scales. KW - Raman Spectroscopy KW - Instrumentation KW - Analytical Chemistry KW - Knufia petricola KW - Confocal microscopy KW - Atomic and Molecular Physics and Optics PY - 2023 DO - https://doi.org/10.1016/j.saa.2023.123250 SN - 1386-1425 VL - 303 SP - 1 EP - 11 PB - Elsevier BV AN - OPUS4-58792 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz A1 - Silbernagl, Dorothee A1 - Ghasem Zadeh Khorasani, Media T1 - Improving polymer matrix additives for composite structures: a focus on boehmite N2 - The aims of the Research Unit „Acting Principles of Nano-Scaled Matrix Additives for Composite Structures“ (DFG FOR 2021) are based on different synergetic pathways. Challenges are to achieve an improved damage tolerance combined with unchanged processability and a proof of the nano-based effect from molecular scale up to structural level. First of all, a comprehensive understanding of the acting mechanisms of nano-scaled ceramic additives onto polymer matrices of continuous fibre reinforced polymer composites with respect to improved matrix dominated properties is in focus. To proof of the nanoscopic and microscopic effects up to structural level; experimental investigations start on the functional correlation between the particle properties and the resulting properties of the epoxy as suspension and in the solid state. This includes tests for the resulting composite structures as well. Along the entire process chain different multi-scale simulations are performed from molecular modelling up to the macroscopic, structural level. The combination of experimental investigations and simulation methods enables a holistic understanding of the acting principles and basic mechanisms. Specialized techniques based on Scanning Force Microscopy are the basis of our analysis of physicochemical properties of the boehmite nanoparticles and their polymer environment. A surface map of mechanical properties as an input for simulations facilitate a deeper understanding of such composites across all scales. This enables us to understand the macroscopic structure-property relationship and to predict failure mechanisms as well as routes for optimization. T2 - 92nd DKG annual meeting and symposium on high performance ceramics CY - Berlin, Germany DA - 19.03.2017 KW - Boehmite nanoparticle KW - Intermodulation AFM KW - Composite structures KW - Pull-out test KW - Thermoset KW - Crack propagation energy PY - 2017 AN - OPUS4-39519 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hartmann, S A1 - Sturm, Heinz A1 - Blaudeck, T A1 - Hoelck, O A1 - Hermann, S A1 - Schulz, SE A1 - Wunderle, B. T1 - Experimental and computational studies on the role of surface functional groups in the mechanical behavior of interfaces between single-walled carbon nanotubes and metals N2 - To study the mechanical interface behavior of single-walled carbon nanotubes (CNTs) embedded in a noble metal, we performed CNT-metal pull-out tests with in situ scanning electron microscope experiments. Molecular dynamics (MD) simulations were conducted to predict force-displacement data during pull-out, providing critical forces for failure of the system. In MD simulations, we focused on the influence of carboxylic surface functional groups (SFGs) covalently linked to the CNT. Experimentally obtained maximum forces between 10 and 102 nN in palladium and gold matrices and simulated achievable pulling forces agree very well. The dominant failure mode in the experiment is CNT rupture, although several pull-out failures were also observed. We explain the huge scatter of experimental values with varying embedding length and SFG surface density. From simulation, we found that SFGs act as small anchors in the metal matrix and significantly enhance the maximum forces. This interface reinforcement can lead to tensile stresses sufficiently high to initiate CNT rupture. To qualify the existence of carboxylic SFGs on our CNT material, we performed analytical investigation by means of fluorescence labeling of surface species and discuss the results. With this contribution, we focus on a synergy between computational and experimental approaches involving MD simulations, nano scale testing, and analytics (1) to predict to a good degree of accuracy maximum pull-out forces of single-walled CNTs embedded in a noble metal matrix and (2) to provide valuable input to understand the underlying mechanisms of failure with focus on SFGs. This is of fundamental interest for the design of future mechanical sensors incorporating piezoresistive single-walled CNTs as the sensing element. KW - Oxygen-containing functionalities KW - Molecular-dynamics KW - Structural characterization KW - Reinforced composites KW - Raman spectroscopy KW - Shear strength KW - Polymer matrix KW - Pull-out KW - Simulation KW - Purification PY - 2016 DO - https://doi.org/10.1007/s10853-015-9142-6 SN - 0022-2461 SN - 1573-4803 VL - 51 IS - 3 SP - 1217 EP - 1233 AN - OPUS4-35795 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Stajanca, Pavol A1 - Mihai, L. A1 - Sporea, D. A1 - Negut, D. A1 - Sturm, Heinz A1 - Schukar, Marcus A1 - Krebber, Katerina T1 - Effects of gamma radiation on perfluorinated polymer optical fibers N2 - The paper presents the first complex study of Gamma radiation effects on a low-loss perfluorinated polymer optical fiber (PF-POF) based on Cytop® polymer. Influence of gamma radiation on fiber’s optical, mechanical and climatic performance is investigated. The radiation-induced attenuation (RIA) in the visible and near-infrared region (0.4 μm-1.7 mm) is measured and its origins are discussed. Besides attenuation increase, radiation is also shown to decrease the thermal degradation stability of the fiber and to increase its susceptibility to water. With regard to complex fiber transmission performance upon irradiation, the optimal operation wavelength region of PF-POF-based systems intended for use in Radiation environments is determined to be around 1.1 μm. On the other hand, the investigated fiber holds potential for low-cost RIA-based optical fiber dosimetry applications with sensitivity as high as 260 dBm⁻¹/kGy in the visible region. KW - Perfluorinated polymer optical fibers KW - Cytop KW - Gamma radiation KW - Radiation-induced attenuation PY - 2016 DO - https://doi.org/10.1016/j.optmat.2016.05.027 SN - 0925-3467 VL - 58 SP - 226 EP - 233 PB - Elsevier AN - OPUS4-36462 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Topolniak, Ievgeniia A1 - Elert, Anna Maria A1 - Knigge, Xenia A1 - Cifci, G. C. A1 - Radnik, Jörg A1 - Sturm, Heinz T1 - Polydopamine micropatterning for selective substrate bio-functionalization N2 - Inspired by the chemistry of mussel adhesive proteins, polydopamine (PDA) exhibits strong adhesion to nearly any kind of organic or inorganic surface and shows high ability for surface post-modification and secondary reactions. As a result, PDA has been widely used as a base adlayer to enable versatile surface chemistry and functionalization. It has shown great potential in wide range of applications including biomedical field (e.g., drug delivery, adhesives, photothermal therapy, bone and tissue engineering, cell adhesion, biosensing). However, implementation of PDA in microdevices is still hindered by insufficient spatial and temporal control of excited deposition methods. In this work we present a novel approach to fabricate tunable micropatterned substrates where mussel-inspired chemistry provides base for various surface modification [2]. Current approach applies Multiphoton Lithography (MPL) to initiate local PDA formation, and, therefore, does not require use of microstamp or photomask. As a result, the microstructures of complex designs can be produced with the spatial resolution down to 0.8 μm (Figure 1). The desired design can be easily altered by adjusting the stl model or the fabrication code. Unlike the conventional deposition of PDA based on dopamine auto-oxidation, our method does not require presence of strong oxidants, metal ions or alkaline pH. Herein-demonstrated deposition approach will significantly facilitate applications of polydopamine and other mussel-inspired materials in microdevices and high-resolution active microcomponents (e.g., in MEMS and microfluidics). Adjustment of MPL parameters revealed that the morphology and thickness of resulted PDA microstructures can be controlled by altering the laser power and its scanning velocity. As a result, it also enables the production of micropatterns with structural gradient. Apart from the glass substrate, we performed PDA patterning at surfaces of different nature such as polychlorotrifluoroethylene, polydimethylsiloxane, polyethylene terephthalate, silicon wafers, and fluorinated glass coverslips. We tested different composition of dopamine solution for its ability of PDA buildup. Solutions containing Tris buffer, phosphate buffer or DI water only as well as different pH (6.0, 7.0 and 8.5) could be successfully applied for high-precision PDA micropatterning. Moreover, the effect of antioxidants and purging of the solution with oxygen and nitrogen was investigated. In all cases, no decrease of deposition efficiency was observed. The chemical nature of PDA was confirmed by locally recorded vibrational and x-ray photoelectron spectra. To ensure post-modification potential of MPL deposited PDA we demonstrated one-step deposition of micropatterns with trypsin. Obtained bio-functionalised surface can be further applied as a protein sensing active microelement. T2 - Laser Precision Microfabrication CY - Dresden, Germany DA - 07.06.2022 KW - Polydopamine KW - Two-photon polymerisation KW - Micropatterning PY - 2022 AN - OPUS4-55064 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bhattacharya, Biswajit A1 - Michalchuk, Adam A. L. A1 - Silbernagl, Dorothee A1 - Yasuda, N. A1 - Feiler, Torvid A1 - Sturm, Heinz A1 - Emmerling, Franziska T1 - An atomistic mechanism for elasto-plastic bending in molecular crystals N2 - Mechanically flexible single crystals of molecular materials offer potential for a multitude of new directions in advanced materials design. Before the full potential of such materials can be exploited, insight into their mechanisms of action must be better understood. Such insight can be only obtained through synergistic use of advanced experimentation and simulation. We herein report the first detailed mechanistic study of elasto-plastic flexibility in a molecular solid. An atomistic origin for this mechanical behaviour is proposed through a combination of atomic force microscopy, μ-focus synchrotron X-ray diffraction, Raman spectroscopy, ab initio simulation, and computed elastic tensors. Our findings suggest that elastic and plastic bending are intimately linked and result from extensions of the same molecular deformations. The proposed mechanism bridges the gap between contested mechanisms, suggesting its applicability as a general mechanism for elastic and plastic bending in organic molecular crystals. KW - Mechanical property KW - Mechanical flexibility KW - Organic crystal PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-577722 DO - https://doi.org/10.1039/D2SC06470G SN - 2041-6520 VL - 14 IS - 13 SP - 3441 EP - 3450 PB - Royal Society of Chemisty (RSC) CY - London/Cambridge AN - OPUS4-57772 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Meyer-Plath, Asmus A1 - Beckert, F A1 - Tölle, FJ A1 - Sturm, Heinz A1 - Mülhaupt, R T1 - Stable aqueous dispersions of functionalized multi-layer graphene by pulsed underwater plasma exfoliation of graphite N2 - A process was developed for graphite particle exfoliation in water to stably dispersed multi-layer graphene. It uses electrohydraulic shockwaves and the functionalizing effect of solution plasma discharges in water. The discharges were excited by 100 ns high voltage pulsing of graphite particle chains that bridge an electrode gap. The underwater discharges allow simultaneous exfoliation and chemical functionalization of graphite particles to partially oxidized multi-layer graphene. Exfoliation is caused by shockwaves that result from rapid evaporation of carbon and water to plasma-excited gas species. Depending on discharge energy and locus of ignition, the shockwaves cause stirring, erosion, exfoliation and/or expansion of graphite flakes. The process was optimized to produce long-term stable aqueous dispersions of multi-layer graphene from graphite in a single process step without requiring addition of intercalants, surfactants, binders or special solvents. A setup was developed that allows continuous production of aqueous dispersions of flake size-selected multi-layer graphenes. Due to the well-preserved sp(2)-carbon structure, thin films made from the dispersed graphene exhibited high electrical conductivity. Underwater plasma discharge processing exhibits high innovation potential for morphological and chemical modifications of carbonaceous materials and surfaces, especially for the generation of stable dispersions of two-dimensional, layered materials. KW - Exfoliation KW - Graphene KW - Aqueous dispersion KW - Solution plasma KW - Functionalization KW - Electrohydraulic effect KW - Shear exfoliation KW - Oxide-films KW - Water PY - 2016 DO - https://doi.org/10.1088/0022-3727/49/4/045301 SN - 0022-3727 VL - 49 IS - 4 SP - 045301-1 EP - 045301-11 AN - OPUS4-35796 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hartmann, S. A1 - Shaporin, A. A1 - Hermann, S. A1 - Bonitz, J. A1 - Heggen, M. A1 - Meszmer, P. A1 - Sturm, Heinz A1 - Hölck, O. A1 - Blaudeck, T. A1 - Schulz, S. E. A1 - Mehner, J. A1 - Gessner, T. A1 - Wunderle, B. T1 - Towards nanoreliability of CNT-based sensor applications: Investigations of CNT-metal interfaces combining molecular dynamics simulations, advanced in situ experiments and analytics N2 - In this paper we present results of our recent efforts to understand the mechanical interface behaviour of single-walled carbon nanotubes (CNTs) embedded in metal matrices. We conducted experimental pull-out tests of CNTs embedded in Pd or Au and found Maximum forces in the range 10 - 102 nN. These values are in good agreement with forces obtained from molecular Dynamics simulations taking into account surface functional Groups (SFGs) covalently linked to the CNT material. The dominant failure mode in experiment is a CNT rupture, which can be explained with the presence of SFGs. To qualify the existence of SFGs on our used CNT material, we pursue investigations by means of fluorescence labeling of surface species in combination with Raman imaging. We also report of a tensile test system to perform pull-out tests inside a transmission electron microscope to obtain in situ images of CNT-metal interfaces under mechanical loads at the atomic scale. T2 - 2015 16th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems CY - Budapest, Hungary DA - 20.4.2015 KW - Carbon nanotube CNT KW - Metal matrix KW - Pull-out test KW - Molecular dynamics simulation KW - Surface functional groups KW - Fluorescence labeling KW - Raman imaging KW - Tensile test inside a TEM PY - 2015 SN - 978-1-4799-9950-7 VL - 2015 SP - 1 EP - 8 PB - IEEE AN - OPUS4-37625 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Fritzsche, Sven A1 - Weimann, Christiane A1 - Pauw, Brian Richard A1 - Sturm, Heinz T1 - 2PP-TestArtifact N2 - This repository contains a test artifact (TA), also called test structure, designed for two-photon polymerization (also known as Direct Laser Writing (DLW) or Two/Multi-photon lithography (2PA/MPA)). Test artifacts can be used to compare structures, to check options used by the slicer, check the state of the 2PP machine itself or to get a construction guidelines for a certain combination of power, velocity and settings. The associated paper can be found here: https://dx.doi.org/10.1088/1361-6501/acc47a General ideas behind the test artifact: 1. optimized for 2PP-DLW 2. should be fast and easy to analyse with optical microscopy or 3. scanning electron microscopy without tilt. 3. short time to fabricate 4. include a reasonable amount of different features 5. bulk and small structures on the substrate KW - Reference structure KW - Calibration structure KW - Test structure KW - Laser writing KW - Two-photon polymerization KW - 3D printing KW - Additive manufacturing KW - Microprinting KW - Multi-photon light structuring PY - 2023 DO - https://doi.org/10.6084/m9.figshare.22285204.v2 PB - Digital Science CY - Cambridge, MA, USA AN - OPUS4-57165 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - INPR A1 - Fritzsche, Sven A1 - Pauw, Brian Richard A1 - Weimann, Christiane A1 - Sturm, Heinz T1 - First of its kind: A test artifact for direct laser writing N2 - With Direct Laser Writing (DLW) maturing in all aspects as a manufacturing technology a toolset for quality assurance must be developed. In this work we want to introduce a first of its kind test artifact. Test artifacts are standardized 3D models with specific geometric feature to evaluate the performance of writing parameters. Test artifacts are already common in other 3D additive manufacturing technologies e.g. Selective Laser Melting. The test artifact introduced in this work was developed in particular to accommodate 1) the high geometrical resolution of DLW structures and 2) the limited possibilities to examine the resulting structure. Geometric accuracy, surface adhesion as well as confocal raman spectroscopy results were considered when evaluating the design of the test artifact. We will explain the individual features and design considerations of our DLW test artifact. The difference between two slicers, Cura and 3DPoli, and the implications on measured feature sizes and the general shape is quantified. The measured geometries are used to derive a general design guide for a specific combination of photoresist, laser power and scanning speed and to analyse the geometric accuracy of a structure produced using these guidelines. KW - Multi photon lithography KW - Test artifact KW - Two photon polymerization KW - Direct Laser Writing KW - Quality infrastructure PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-560530 DO - https://doi.org/10.20944/preprints202210.0259.v1 SP - 1 EP - 29 PB - MDPI CY - Basel AN - OPUS4-56053 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fortini, Renata A1 - Meyer-Plath, A. A1 - Kehren, D. A1 - Gernert, U. A1 - Agudo Jácome, Leonardo A1 - Sturm, Heinz T1 - Measurement of flexural rigidity of multi-walled carbon nanotubes by Dynamic Scanning Electron Microscopy N2 - In this work the flexural rigidity of individual large diameter multi-walled carbon nanotubes (MWCNTs) was investigated. The bending modulus were obtained by detecting the resonance frequencies of mechanically excited cantilevered carbon nanotubes using the so-called dynamic scanning electron microscopy technique, and applying the Euler–Bernoulli beam theory. For the nanotubes studied, we determined a modulus of up to 160 GPa. This agrees with values reported by other authors for MWCNTs produced by catalytic chemical vapor deposition, however, it is 6-8 times smaller than values reported for single and multi-walled carbon nanotubes produced by arc-discharge synthesis. Toxicological studies with carbon nanotubes have been showing that inhaled airborne nanofibers that reach the deep airways of the respiratory system may lead to serious, asbestos-like lung diseases. These studies suggested that their toxicity critically depends on the fiber flexural rigidity, with high rigidity causing cell lesions. To complement the correlation between observed toxicological effects and fiber rigidities, reliable and routinely applicable measurement techniques for the flexural rigidity of nanofibers are required. KW - Flexural rigidity KW - Bending modulus KW - Resonance frequency KW - Carbon nanotubes KW - Fiber toxicology PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-514190 DO - https://doi.org/10.3390/fib8050031 SN - 2079-6439 VL - 8 IS - 5 SP - 31 PB - MDPI AN - OPUS4-51419 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Szymoniak, Paulina A1 - Qu, Xintong A1 - Schönhals, Andreas A1 - Sturm, Heinz ED - Sinapius, M. ED - Ziegmann, G. T1 - Characterization of Polymer Nanocomposites N2 - The complex effect of nanoparticles on an epoxy-based and anhydride cured DGEBA/Boehmite nanocomposite with different particle concentrations is considered in this chapter. A combination of X-ray scattering, calorimetry (fast scanning and temperature modulated calorimetry) and dielectric spectroscopy was employed to characterize the structure, vitrification kinetics and the molecular dynamics of the nanocomposites. Firstly, the unfilled polymer was found to be intrinsically heterogeneous, showing regions with different crosslinking density, indicated by two separate dynamic glass transitions. Moreover, the glass transition temperature decreases with increasing nanoparticle concentration, as a result of changes in the crosslinking density. In addition, it was shown that the incorporation of nanoparticles can result in simultaneous increase in the number of mobile segments for low nanoparticle concentrations and on the other hand, for higher loading degrees the number of mobile segments decreases, due to the formation of an immobilized interphase. KW - Rigid amorphous fraction KW - Epoxy nanocomposites KW - X-ray scattering KW - Differential scanning calorimetry KW - Broadband dielectric spectroscopy KW - Flash DSC PY - 2021 DO - https://doi.org/10.1007/978-3-030-68523-2_4 SP - 55 EP - 77 PB - Springer Nature AN - OPUS4-52698 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Waniek, Tassilo A1 - Braun, U. A1 - Silbernagl, Dorothee A1 - Sturm, Heinz T1 - The impact of water released from boehmite nanoparticles during curing in epoxy-based nanocomposites N2 - The enhancing effect on mechanical properties of boehmite (γ-AlOOH) nanoparticles (BNP) in epoxy-based nanocomposites on the macroscopic scale encouraged recent research to investigate the micro- and nanoscopic properties. Several studies presented different aspects relatable to an alteration of the epoxy polymer network formation by the BNP with need for further experiments to identify the mode of action. With FTIR-spectroscopic methods this study identifies interactions of the BNP with the epoxy polymer matrix during the curing process as well as in the cured nanocomposite. The data reveals that not the BNP themselves, but the water released from them strongly influences the curing process by hydrolysis of the anhydride hardener or protonation of the amine accelerator. The changes of the curing processes are discussed in detail. The changes of the curing processes enable new explanation for the changed material properties by BNP discussed in recent research like a lowered glass transition temperature region (Tg) and an interphase formation. KW - Spectroscopy KW - Aluminium oxide hydroxide KW - Glass transition temperature KW - Material chemistry KW - Nanocomposites KW - Structure-property relationship PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-527202 DO - https://doi.org/10.1002/app.51006 VL - 138 IS - 39 SP - 51006 PB - Wiley Periodicals LLC CY - Hoboken AN - OPUS4-52720 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cano Murillo, Natalia A1 - Ghasem Zadeh Khorasani, Media A1 - Silbernagl, Dorothee A1 - Emamverdi, Farnaz A1 - Cacua, K. A1 - Hodoroaba, Vasile-Dan A1 - Sturm, Heinz T1 - Carrier Fibers for the Safe Dosage of Nanoparticles in Nanocomposites: Nanomechanical and Thermomechanical Study on Polycarbonate/Boehmite Electrospun Fibers Embedded in Epoxy Resin N2 - The reinforcing effect of boehmite nanoparticles (BNP) in epoxy resins for fiber composite lightweight construction is related to the formation of a soft but bound interphase between filler and polymer. The interphase is able to dissipate crack propagation energy and consequently increases the fracture toughness of the epoxy resin. Usually, the nanoparticles are dispersed in the resin and then mixed with the hardener to form an applicable mixture to impregnate the fibers. If one wishes to locally increase the fracture toughness at particularly stressed positions of the fiber-reinforced polymer composites (FRPC), this could be done by spraying nanoparticles from a suspension. However, this would entail high costs for removing the nanoparticles from the ambient air. We propose that a fiber fleece containing bound nanoparticles be inserted at exposed locations. For the present proof-of-concept study, an electrospun polycarbonate nonwoven and taurine modified BNP are proposed. After fabrication of suitable PC/EP/BNP composites, the thermomechanical properties were tested by dynamic mechanical analysis (DMA). Comparatively, the local nanomechanical properties such as stiffness and elastic modulus were determined by atomic force microscopy (AFM). An additional investigation of the distribution of the nanoparticles in the epoxy matrix, which is a prerequisite for an effective nanocomposite, is carried out by scanning electron microscopy in transmission mode (TSEM). From the results it can be concluded that the concept of carrier fibers for nanoparticles is viable. KW - Advanced materials KW - Electrospun nanocomposite fiber KW - Nanomechanical charecteisation KW - Nanosafety KW - Epoxy nanocomposites PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-528265 DO - https://doi.org/10.3390/nano11061591 VL - 11 IS - 6 SP - 1591 PB - MDPI CY - CH - 4020 Basel, Switzerland AN - OPUS4-52826 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Hahn, Marc Benjamin A1 - Sturm, Heinz A1 - Bier, F A1 - Solomun, Tihomir T1 - Biologische Konsequenzen einer nanoskaligen Energiedeposition: Fokussierung auf die Rolle niederenergetischer Elektronen T1 - Biological Consequence of Nanoscale Energy Deposition: Focusing on the Role of Low-Energy Electrons N2 - Bei der Behandlung von Krebs mittels Strahlentherapie sollen Tumorzellen abgetötet werden ohne das umliegende gesunde Gewebe zu zerstören. Um Strahlentherapien für Patienten verträglicher zu machen, ist ein besseres Verständnis der zugrundeliegenden Prozesse auf der molekularen Ebene nötig. Dabei sind der Energieeintrag und die Streuprozesse der Strahlung in der Umgebung der DNA von besonderem Interesse. Durch Streuung von hochenergetischer Strahlung in Wasser werden besonders viele Sekundärelektronen mit niedriger Energie erzeugt. Zur Untersuchung der Schädigungseffizienz dieser Elektronen wurde ein Verfahren zur direkten Bestrahlung von Lösungen mittels Elektronen variabler Energien enwtickelt. Dies wurde durch einen neu entwickelten Probenhalter mit einer für Elektronen durchlässigen Nanomembran ermöglicht. Mit diesem können Bestrahlungen an DNA, Proteinen, und Zellen bei verschiedenen pH-Werten oder Salzkonzentrationen durchgeführt werden. Parallel dazu wurde der ortsabhängige Energieeintrag innerhalb des Wassers durch Elektronenstreusimulationen bestimmt. Diese neuartige Kombination von Experiment und Simulation ermöglicht die Bestimmung der Schaden-Dosis-Relation für Elektronenbestrahlung von biologischen Systemen unter realistischen physiologischen Bedingungen. So konnten für die genutzten Primärelektronen wie die mittlere letale Dosis, bei der 50 Prozent der DNA geschädigt sind, mit 1,7 Gy bestimmt. Ebenfalls wurde das für mikrodosimetrische Modellierungen und Betrachtungen der sogenannten Linear energy transfer (LET) Effekte, wichtige Verhältnis von DNA Einzelstrangbrüchen (SSB) zu Doppelstrangbrüchen (DSB) als SSB/DSB = 12/1 bestimmt. Mit Hilfe eines Modells für das Targetvolumen der DNA wurde der mittlere mikroskopische letale Energieeintrag berechnet als E1/2 = 6 ± 4 eV . Es wurde gefolgert, dass weniger als zwei Ionisationsprozesse im sensitiven Targetvolumen der DNA im Mittel zu einem Einzelstrangbruch führen. Diese Methode ist unabhängig von den Primärpartikel und geometrischen Bedingungen. Deshalb ermöglicht sie die Vergleichbarkeit experimenteller Systeme mit inhomogenen Energieverteilungen, welches sonst nicht gegeben ist. Des weiteren wurden die Strahlenschutzfunktionen des Zellschutzmoleküls Ectoines und sein Einfluss auf Wasser und Biomoleküle untersucht. Seine Schutzfunktion gegen ionisierende Strahlung wurde auf die Erhöhung des Streuquerschnitts niederenergetischer Elektronen und seine Eigenschaft als OH-Radikalfänger zurückgeführt. Aufbauend auf unseren Erkenntnissen finden in klinischen Arbeitsgruppen Untersuchungen zu Einsatzmöglichkeiten im Umfeld der Strahlentherapie statt. Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 245767821 N2 - To cure cancer radiation therapy is used to kill tumor cells. It is based on radiation induced damage to biomolecules. Here DNA damage is of key interest due to its central role in apoptosis and mutation. Because of the high amount of water in biological tissue, most of the damage is caused by the secondary particles produced by the inelastic scattering of ionizing radiation and water. A detailed understanding of the underlying molecular processes under physiological conditions is the prerequisite to develop more efficient the-rapies. Therefore irradiations have to be performed in liquid, under consideration of the chemical environment. To make it possible to irradiate liquids with electrons within scanning electron microscopes a new sample holder was constructed incorporating an electron transparent nanomembrane. It makes it possible to irradiate DNA, proteins or cells at different pH and salinity. The median lethal dose for a model system of plasmid DNA and water was determined by the combination of experimental data, particle scattering simulations (Geant4-DNA) and diffusion calculations as D1/2 = 1.7 ± 0.3 Gy. From the convolution of plasmid positions and the spatially resolved energy deposit, as determined by electron scattering simulations, the histogram of the energy deposit within the target volume of the plasmids and the microscopic median lethal energy deposit was calculated as E1/2 = 6 ± 4 eV . It could be deduced, that on average less than two ionization Events are sufficient to cause a single-strand-break. The relation of single-strand-breaks (SSB) to double-strand-breaks (DSB), which is of importance for microdosimetric modeling, was determined as SSB : DSB = 12 : 1. The presented method for the Determination of microscopic dose-damage relations was further extended to be applicable for General irradiation experiments. It is independent of the type of primary radiation used, the experimental geometry, and the diffusional properties of the molecules under investigation. This way different experimental systems with varying, inhomogeneous energy deposit characteristics become comparable with each other, which is not possible when only macroscopic averaged values are taken into account. In addition, the radiation protection properties of the compatible solute Ectoine was investigated. The protective properties of ectoine result from the increase of the inelastic scattering probabilities of low Energy electrons at the acoustic vibrational modes of water and its properties as OH-radical scavenger. Based on our results, further investigations are conducted to evaluate the application of Ectoine in the context of radiation therapy. Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 245767821 KW - Ectoin KW - Ectoine KW - DNS KW - DNA KW - Cancer therapy KW - DNA damage KW - DNA radiation damage KW - Dosimetry KW - DFG KW - Electron irradiation KW - Ectoine DNA interaction KW - Ectoine radiation protection KW - Hydroxyl radicals KW - OH radicals KW - LEE KW - Low energy electrons KW - Microdosimetry KW - Radiation KW - Geant4 KW - Geant4-DNA KW - Radiation therapy KW - LET PY - 2021 UR - https://gepris.dfg.de/gepris/projekt/245767821/ergebnisse?context=projekt&task=showDetail&id=245767821&selectedSubTab=2& SP - 1 EP - 14 AN - OPUS4-52389 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Silbernagl, Dorothee A1 - Sturm, Heinz A1 - Plajer, A. J. T1 - Thioanhydride/isothiocyanate/epoxide ring-opening terpolymerisation: sequence selective enchainment of monomer mixtures and switchable catalysis N2 - We report a new sequence selective terpolymerisation in which three monomers (butylene oxide (BO) A, PhNCS B and phtalic thioanhydride (PTA) C) are selectively enchained into an (ABA′C)n sequence. PTA/PhNCS/BO ring-opening terpolymerisation ROTERP can be coupled with CS2 ROTERP to generate tetrapolymers and with εDL ROP in switchable catalysis for blockpolymer synthesis. KW - Blockcopolymer KW - 1H-NMR KW - TGA KW - DSC KW - AFM PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-552339 DO - https://doi.org/10.1039/d2py00629d SP - 1 EP - 5 PB - Royal Society of Chemistry CY - Cambridge, UK AN - OPUS4-55233 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bhattacharya, Biswajit A1 - Michalchuk, Adam A1 - Silbernagl, Dorothee A1 - Rautenberg, Max A1 - Schmid, Thomas A1 - Feiler, Torvid A1 - Reimann, K. A1 - Ghalgaoui, A. A1 - Sturm, Heinz A1 - Paulus, B. A1 - Emmerling, Franziska T1 - A Mechanistic Perspective on Plastically Flexible Coordination Polymers N2 - Mechanical flexibility in single crystals of covalently bound materials is a fascinating and poorly understood phenomenon. We present here the first example of a plastically flexible one-dimensional (1D) coordination polymer. The compound [Zn(m-Cl)2(3,5-dichloropyridine)2]n is flexible over two crystallographic faces. Remarkably, the single crystal remains intact when bent to 1808. A combination of microscopy, diffraction, and spectroscopic studies have been used to probe the structural response of the crystal lattice to mechanical bending. Deformation of the covalent polymer chains does not appear to be responsible for the observed macroscopic bending. Instead, our results suggest that mechanical bending occurs by displacement of the coordination polymer chains. Based on experimental and theoretical evidence, we propose a new model for mechanical flexibility in 1D coordination polymers. Moreover, our calculations propose a cause of the different mechanical properties of this compound and a structurally similar elastic material KW - Coordination polymer KW - Flexible crystals KW - Mechanical properties KW - Plastic deformation PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-504755 DO - https://doi.org/10.1002/anie.201914798 VL - 59 IS - 14 SP - 5557 EP - 5561 PB - Wiley-VCH AN - OPUS4-50475 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hahn, Marc Benjamin A1 - Smales, Glen Jacob A1 - Seitz, H. A1 - Solomun, Tihomir A1 - Sturm, Heinz T1 - Ectoine interaction with DNA: Influence on ultraviolet radiation damage N2 - Ectoine is a small zwitterionic osmolyte and compatible solute, which does not interfere with cell metabolism even at molar concentrations. Plasmid DNA (pUC19) was irradiated with ultraviolet radiation (UV-C at 266 nm) under quasi physiological conditions (PBS) and in pure water in the presence and absence of ectoine (THP(B)) and hydroxyectoine (THP(A)). Different types of UV induced DNA damage were analysed: DNA single-strand breaks (SSBs), abasic sites and cyclobutane pyrimidine dimers (CPDs). A complex interplay between these factors was observed with respect to the nature and occurrence of DNA damage with 266 nm photons. In PBS, the cosolutes showed efficient protection against base damage, whilst in pure water, a dramatic shift from SSB damage to base damage was observed when cosolutes were added. To test whether these effects are caused by ectoine binding to DNA, further experiments were conducted: small-angle X-ray scattering (SAXS), surface-plasmon resonance (SPR) measurements and Raman spectroscopy. The results show, for the first time, a close interaction between ectoine and DNA. This is in stark contrast to the assumption made by preferential exclusion models, which are often used to interpret the behaviour of compatible solutes within cells and with biomolecules. It is tentatively proposed that the alterations of UV damage to DNA are attributed to ectoine influence on nucleobases through the direct interaction between ectoine and DNA. KW - Ectoine KW - DNA KW - Radiation damage KW - Radiation protection KW - SSB KW - DNA damage KW - DNA protection KW - Compatible solute KW - Zwitterion KW - Hydroxyectoine KW - Salt KW - PBS KW - UV absorption KW - DNA strand-break KW - DNA base damage KW - Ectoine UV absorption KW - Ectoine DNA protection KW - Excited states KW - UV irradiation KW - UV-A KW - UV-B KW - UV-C KW - 266nm KW - UV photons KW - Ectoine-DNA binding KW - Raman spectroscopy KW - UV-Vis KW - Radical scavenger KW - OH scavenger KW - Hydroxyl radicals KW - CPD KW - Abasic site KW - Agarose gel electrophorese KW - SYBR gold KW - DNA melting temperature KW - Counterions KW - Preferential exclusion KW - Cancer KW - Therapy KW - UV protection KW - Sunscreen PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-505772 DO - https://doi.org/10.1039/d0cp00092b SN - 1463-9076 SN - 1463-9084 VL - 22 IS - 13 SP - 6984 EP - 6992 PB - Royal Society of Chemistry CY - Cambridge AN - OPUS4-50577 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cano Murillo, Natalia A1 - Ghasem Zadeh Khorasani, Media A1 - Silbernagl, Dorothee A1 - Hahn, Marc Benjamin A1 - Hodoroaba, Vasile-Dan A1 - Sturm, Heinz T1 - Nanomechanical study of polycarbonate/boehmite nanoparticles/epoxy ternary composite and their interphases N2 - Thermoplastic modified thermosets are of great interest especially due to their improved fracture toughness. Comparable enhancements have been achieved by adding different nanofillers including inorganic particles such as nanosized boehmite. Here, we present a nanomechanical study of two composite systems, the first comprising a polycarbonate (PC) layer in contact with epoxy resin (EP) and the second consisting of a PC layer containing boehmite nanoparticles (BNP) which is also in contact with an EP layer. The interaction between PC and EP monomer is tested by in situ Fourier transformed infrared (FT-IR) analysis, from which a reaction induced phase separation of the PC phase is inferred. Both systems are explored by atomic force microscopy (AFM) force spectroscopy. AFM force-distance curves (FDC) show no alteration of the mechanical properties of EP at the interface to PC. However, when a PC phase loaded with BNP is put in contact with an epoxy system during curing, a considerable mechanical improvement exceeding the rule of mixture was detected. The trend of BNP to agglomerate preferentially around EP dominated regions and the stiffening effect of BNP on EP shown by spatial resolved measurements of Young's modulus, suggest the effective presence of BNP within the EP phase. KW - Composites KW - Mechanical properties KW - Nanoparticles KW - Thermoplastics KW - Thermosets PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-515965 DO - https://doi.org/10.1002/app.50231 SN - 0021-8995 SN - 1097-4628 VL - 138 IS - 12 SP - 1 EP - 11 PB - Wiley CY - New York, NY AN - OPUS4-51596 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Topolniak, Ievgeniia A1 - Elert, Anna Maria A1 - Knigge, Xenia A1 - Ciftci, G. C. A1 - Radnik, Jörg A1 - Sturm, Heinz T1 - High precision micropatterning of polydopamine by Multiphoton Lithography N2 - Mussel-inspired polydopamine (PDA) initiated a multifunctional modification route that leads to the generation of novel advanced materials and their applications. However, existing PDA deposition techniques still exhibit poor spatial control, have a very limited capability of micropatterning and do not allow to locally tune PDA topography. Herein, we demonstrate PDA deposition based on Multiphoton Lithography (MPL) that enables full spatial and temporal control with nearly total freedom of patterning design. Using MPL, we achieve 2D microstructures of complex design with pattern precision of 0.8 μm without the need of a photomask or stamp. Moreover, this approach permits adjusting the morphology and thickness of the fabricated microstructure within one deposition step, resulting in a unique tunability of materials properties. The chemical composition of PDA is confirmed and its ability for protein enzyme immobilization is demonstrated. This work presents a new methodology for high precision and complete control of PDA deposition, enabling PDA incorporation in applications where fine and precise local surface functionalization is required. Possible applications include multicomponent functional elements and devices in microfluidics or lab-on-a-chip systems. KW - Multiphoton lithography KW - Polydopamine KW - Micropatterning PY - 2022 DO - https://doi.org/10.1002/adma.202109509 VL - 34 IS - 18 SP - e2109509 PB - Wiley online library AN - OPUS4-54535 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dudziak, Mateusz A1 - Topolniak, Ievgeniia A1 - Silbernagl, Dorothee A1 - Altmann, Korinna A1 - Sturm, Heinz T1 - Long-time behavior of surface properties of microstructures fabricated by multiphoton lithography N2 - The multiphoton lithography (MPL) technique represents the future of 3D microprinting, enabling the production of complex microscale objects with high precision. Although the MPL fabrication parameters are widely evaluated and discussed, not much attention has been given to the microscopic properties of 3D objects with respect to their surface properties and time-dependent stability. These properties are of crucial importance when it comes to the safe and durable use of these structures in biomedical applications. In this work, we investigate the surface properties of the MPL-produced SZ2080 polymeric microstructures with regard to the physical aging processes during the post-production stage. The influence of aging on the polymeric microstructures was investigated by means of Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). As a result, a time-dependent change in Young’s Modulus, plastic deformation, and adhesion and their correlation to the development in chemical composition of the surface of MPL-microstructures are evaluated. The results presented here are valuable for the application of MPL-fabricated 3D objects in general, but especially in medical technology as they give detailed information of the physical and chemical time-dependent dynamic behavior of MPL-printed surfaces and thus their suitability and performance in biological systems. KW - Multiphoton lithography KW - Additive manufacturing KW - Microfabrication KW - SZ2080 negative photo-resist KW - Young´s modulus KW - Aging KW - Surface properties KW - X-ray photoelectron spectroscopy KW - Atomic force microscopy KW - Force-distance-curve PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-542166 DO - https://doi.org/10.3390/nano11123285 SN - 2079-4991 VL - 11 IS - 12 SP - 1 EP - 12 PB - MDPI CY - Basel AN - OPUS4-54216 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sänger, Johanna Christiane A1 - Pauw, Brian Richard A1 - Riechers, Birte A1 - Zocca, Andrea A1 - Rosalie, Julian A1 - Maaß, Robert A1 - Sturm, Heinz A1 - Günster, Jens T1 - Entering a new dimension in powder processing for advanced ceramics shaping N2 - Filigree structures can be manufactured via two-photon-polymerization (2PP) operating in the regime of non-linear light absorption. For the first time it is possible to apply this technique to the powder processing of ceramic structures with a feature size in the range of the critical defect size responsible for brittle fracture and, thus, affecting fracture toughness of high-performance ceramics. In this way, tailoring of advanced properties can be achieved already in the shaping process. Traditionally, 2PP relies on transparent polymerizable resins, which is diametrically opposed to the usually completely opaque ceramic resins and slurries. Here we present a transparent and photocurable suspension of nanoparticles (resin) with very high mass fractions of yttria-stabilized zirconia particles (YSZ). Due to the extremely well dispersed nanoparticles, scattering of light can be effectively suppressed at the process-relevant wavelength of 800 nm. Sintered ceramic structures with a resolution of down to 500 nm were obtained. Even at reduced densities of 1 to 4 g/cm³, the resulting compressive strength with 4,5 GPa is equivalent or even exceeding bulk monolithic yttria stabilized zirconia. A ceramic metamaterial is born, where the mechanical properties of yttria stabilized zirconia are altered by changing geometrical parameters and gives access to a new class of ceramic materials. KW - Two-photon-polymerization KW - Ceramics KW - Powder processing KW - Transparency KW - Meta material KW - Yttria stabilized zirconia PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-564598 DO - https://doi.org/10.1002/adma.202208653 SN - 1521-4095 SP - 1 EP - 8 PB - Wiley-VCH CY - Weinheim AN - OPUS4-56459 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Zarinwall, A. A1 - Waniek, Tassilo A1 - Finke, B. A1 - Sadaat, R. A1 - Sturm, Heinz A1 - Garnweitner, G. ED - Sinapius, M. ED - Ziegmann, G. T1 - Particle Surface Modification N2 - Whilst a decisive role of the particle-matrix interphase on the mechanical properties of nanoparticle-filled polymers has been demonstrated in the last years, the arbitrary design of this interphase remains a very challenging goal. In principle, this could be realized via an appropriate surfacemodification of the nanofiller prior to its incorporation in the polymer. For most systems, such as for boehmite nanofillers, however, the interaction of organic modifiers with the particle surface has not been studied in detail, and only single studies are known rather than systematic investiga- tions on the effects of different chemical functions anchored on the particle surface. In this chapter, we present an extensive study on the binding of APTES, a common silane surface modifier, with boehmite, and show that thermogravimetric analysis (TGA) coupled with mass spectrometry (MS) is a convenient and highly suitable method to elucidate the ligand binding in detail. Furthermore, a two-step coupling strategy is presented, demonstrating that based on APTES anchored to the parti- cle surface, the condensation of various carboxylic acids can be utilized to enable highly diverse chemical properties of the nanofillers, which leads to very different particle-matrix interactions in the nanocomposites. KW - APTES KW - Boehmite KW - Nanoparticle KW - TGA-MS PY - 2021 SN - 978-3-030-68522-5 SN - 978-3-030-68523-2 DO - https://doi.org/10.1007/978-3-030-68523-2 SN - 2194-8240 SN - 2194-8259 SP - 119 EP - 142 PB - Springer Nature Switzerland AG CY - Cham AN - OPUS4-53727 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fritzsche, Sven A1 - Topolniak, Ievgeniia A1 - Weise, Matthias A1 - Sturm, Heinz T1 - Shape deviations of DLW microstructures in dependency of fabrication parameters N2 - Deep understanding of the effects associated with fabrication parameters and their influence on the resulting structures shape is essential for the further development of direct laser writing (DLW). In particular, it is critical for development of reference materials, where structure parameters are precisely fabricated and should be reproduced with use of DLW technology. In this study we investigated the effect of various fabrication and preparation parameters on the structural precision of interest for reference materials. A well-studied photo-curable system, SZ2080 negative photo-resist with 1 wt.% Michler's ketone (Bis) photo-initiator, was investigated in this work. The correlation between applied laser power, laser velocity, fabrication direction on the deviations in the structure shape were observed by means of white light interferometry microscopy. Moreover, influence of slicing and hatching distances as well as prebake time were studied as function of sample shape. Deviations in the structure form between the theoretically expected and the one detected after DLW fabrication were observed in the range up to 15%. The observed shape discrepancies show the essential importance of fine-tuning the fabrication parameter for reference structure production. KW - Direct laser writing KW - Fabrication parameters KW - Structural precision KW - SZ2080 negative photo-resist KW - White light interferometry microscopy PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-535906 DO - https://doi.org/10.1088/1361-6439/ac2a14 VL - 31 IS - 12 SP - 1 EP - 8 PB - IOP Science AN - OPUS4-53590 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Cano Murillo, Natalia A1 - Szymoniak, Paulina A1 - Smales, Glen Jacob A1 - Sturm, Heinz A1 - Schönhals, Andreas T1 - Electrospun nanocomposites fibers of polycarbonate and taurine modified boehmite nanoparticles - What can be learned from structural and thermal investigations N2 - Though the reinforcing properties of inorganic particles in thermosetting nanocomposites, has been exploited, the integration of nanoparticles continues to be challenging in terms of their homogeneous distribution and their manipulation which can contribute to occupational hazards. Due to a second encapsulations of nanoparticles, electrospun nanocomposite fibers containing nanoparticles might be an alternative for overcoming these issues, as the fiber nonwovens contains the nanoparticles allowing for safer manipulation. Here, the morphology, and the thermal properties of electrospun polycarbonate fibers containing taurine modified boehmite nanoparticles (BNP) are investigated by means of small and wide-angle X-ray scattering as well as fast scanning and temperature modulated fast scanning calorimetry for the first time. The latter techniques allow the investigation of the thermal properties of single fibers at heating rates up to 10^4 K s^-1 keeping its structure intact. A quantitative analysis of the scattering data reveals a porous structure of the fibers. The porous structure is quantified regarding the pore volume and the pore size. A constant amount of aggregation is found even for the highly BNP loaded fibers. Thermal analysis on the fibers reveals a rigid amorphous fraction (RAF) where it is known that RAF determinates the properties of a nanocomposite to a large extent. For the fibers RAF amounts up to 40 wt%, which is essential higher compared to equally formulated PC/BNP composite cast films. The RAF in the case of the fibers, is not only due to the presence of particles in the polymer but also due to orientation effects induced by the electrospinning process. KW - Nanocomposite fibers KW - Electrospinning KW - X-ray scattering KW - Fast scanning calorimetry KW - Rigid amorphous fraction PY - 2021 DO - https://doi.org/10.1021/acsapm.1c01265 VL - 3 IS - 12 SP - 6572 EP - 6585 PB - ACS AN - OPUS4-53871 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Silbernagl, Dorothee A1 - Ghasem Zadeh Khorasani, Media A1 - Cano Murillo, Natalia A1 - Elert, Anna Maria A1 - Sturm, Heinz ED - Glatzel, T. T1 - Bulk chemical composition contrast from attractive forces in AFM force spectroscopy N2 - A key application of atomic force microscopy (AFM) is the measurement of physical properties at sub-micrometer resolution. Methods such as force–distance curves (FDCs) or dynamic variants (such as intermodulation AFM (ImAFM)) are able to measure mechanical properties (such as the local stiffness, kr) of nanoscopic heterogeneous materials. For a complete structure–property correlation, these mechanical measurements are considered to lack the ability to identify the chemical structure of the materials. In this study, the measured attractive force, Fattr, acting between the AFM tip and the sample is shown to be an independent measurement for the local chemical composition and hence a complete structure–property correlation can be obtained. A proof of concept is provided by two model samples comprised of (1) epoxy/polycarbonate and (2) epoxy/boehmite. The preparation of the model samples allowed for the assignment of material phases based on AFM topography. Additional chemical characterization on the nanoscale is performed by an AFM/infrared-spectroscopy hybrid method. Mechanical properties (kr) and attractive forces (Fattr) are calculated and a structure–property correlation is obtained by a manual principle component analysis (mPCA) from a kr/Fattr diagram. A third sample comprised of (3) epoxy/polycarbonate/boehmite is measured by ImAFM. The measurement of a 2 × 2 µm cross section yields 128 × 128 force curves which are successfully evaluated by a kr/Fattr diagram and the nanoscopic heterogeneity of the sample is determined. KW - AFM force spectroscopy KW - Composites KW - Principle component analysis KW - Structure–property correlation KW - Van der Waals forces PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520175 DO - https://doi.org/10.3762/bjnano.12.5 SN - 2190-4286 VL - 12 IS - 5 SP - 58 EP - 71 PB - Beilstein Institute CY - Frankfurt am Main AN - OPUS4-52017 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zarinwall, A. A1 - Waniek, Tassilo A1 - Saadat, R. A1 - Braun, U. A1 - Sturm, Heinz A1 - Garnweitner, G. T1 - Comprehensive Characterization of APTES Surface Modifications of Hydrous Boehmite Nanoparticles N2 - Hydrous boehmite (γ-AlOOH) nanoparticles (BNP) show great potential as nanoscale filler for the fabrication of fiber reinforced nanocomposite materials. Notably, the particle−matrix interaction has been demonstrated to be decisive for improving the matrix-dominant mechanical properties in the past years. Tailoring the surface properties of the nanofiller enables to selectively design the interaction and thus to exploit the benefits of the nanocomposite in an optimal way. Here, an extensive study is presented on the binding of (3-aminopropyl)triethoxysilane (APTES), a common silane surface modifier, on BNP in correlation to different process parameters (concentration, time, temperature, and pH). Furthermore, a comprehensive characterization of the modified BNP was performed by using elemental analysis (EA), thermogravimetric analysis (TGA) coupled with mass spectrometry (TGA-MS), and Kaiser’s test (KT). The results show an increasing monolayer formation up to a complete surface coverage with rising APTES concentration, time, and temperature, resulting in a maximal grafting density of 1.3 molecules/nm². Unspecific multilayer formation was solely observed under acidic conditions. Comparison of TGA-MS results with data recorded from EA, TGA, and KT verified that TGA-MS is a convenient and highly suitable method to elucidate the ligand binding in detail. KW - Boehmite KW - Nanoparticle KW - Surface KW - APTES KW - Functionalization KW - BET KW - TGA KW - Grafting KW - Nanocomposite KW - Silane PY - 2020 DO - https://doi.org/10.1021/acs.langmuir.0c02682 VL - 37 IS - 1 SP - 171 EP - 179 PB - ACS Publications AN - OPUS4-51954 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Crasselt, Claudia A1 - Schmidt, Wolfram A1 - Sturm, Heinz T1 - Influence of Rheology Modifying Admixtures on Hydration of Cementitious Suspensions N2 - The presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has an enormous influence on the early hydration of cement. The hydration is retarded and the timing of formation and the morphology of hydrates is affected. This short paper presents experimental results about the influence of delayed addition time of PCE SPs on hydration of cement and alite pastes, investigated by isothermal heat flow calorimetry. For cement as well as for alite pastes the hydration is retarded with SP, whereby the high charge PCE has a stronger retarding effect than the low charge PCE. The retardation caused by PCE is much more pronounced for alite than for cement mixes. If PCE is added later to the mix, the induction period is shortened and the hydration is accelerated compared to simultaneous addition. This applies for cement and alite pastes. With delayed PCE addition the alite shows a clearly less retarded setting and main hydration than after simultaneous addition. It is obvious that for alite pastes there is less retardation the later the addition of SP. T2 - 6th International Symposium on Nanotechnology in Construction CY - Hong Kong, China DA - 02.12.2018 KW - Polycarboxylate ether (PCE) KW - Early hydration KW - Cement PY - 2018 SP - 1 EP - 8 AN - OPUS4-47204 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Topolniak, Ievgeniia A1 - Hodoroaba, Vasile-Dan A1 - Pfeifer, Dietmar A1 - Braun, Ulrike A1 - Sturm, Heinz T1 - Boehmite Nanofillers in Epoxy Oligosiloxane Resins: Influencing the Curing Process by Complex Physical and Chemical Interactions N2 - In this work, a novel boehmite (BA)-embedded organic/inorganic nanocomposite coating based on cycloaliphatic epoxy oligosiloxane (CEOS) resin was fabricated applying UV-induced cationic polymerization. The main changes of the material behavior caused by the nanofiller were investigated with regard to its photocuring kinetics, thermal stability, and glass transition. The role of the particle surface was of particular interest, thus, unmodified nanoparticles (HP14) and particles modified with p-toluenesulfonic acid (OS1) were incorporated into a CEOS matrix in the concentration range of 1–10 wt.%. Resulting nanocomposites exhibited improved thermal properties, with the glass transition temperature (Tg) being shifted from 30 °C for unfilled CEOS to 54 °C (2 wt.% HP14) and 73 °C (2 wt.% OS1) for filled CEOS. Additionally, TGA analysis showed increased thermal stability of samples filled with nanoparticles. An attractive interaction between boehmite and CEOS matrix influenced the curing. Real-time infrared spectroscopy (RT-IR) experiments demonstrated that the epoxide conversion rate of nanocomposites was slightly increased compared to neat resin. The beneficial role of the BA can be explained by the participation of hydroxyl groups at the particle surface in photopolymerization processes and by the complementary contribution of p-toluenesulfonic acid surface modifier and water molecules introduced into the system with nanoparticles. KW - Real-time infrared spectroscopy KW - Boehmite KW - Nanocomposite KW - Cationic photocuring KW - Cycloaliphatic epoxy oligosiloxane KW - Epoxy conversion degree PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-479628 DO - https://doi.org/10.3390/ma12091513 VL - 12 IS - 9 SP - 1513 PB - MDPI AN - OPUS4-47962 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ghasem Zadeh Khorasani, Media A1 - Elert, Anna Maria A1 - Hodoroaba, Vasile-Dan A1 - Agudo Jácome, Leonardo A1 - Altmann, Korinna A1 - Silbernagl, Dorothee A1 - Sturm, Heinz T1 - Short- and long-range mechanical and chemical interphases caused by interaction of Boehmite (γ-AlOOH) with anhydride-cured epoxy resins N2 - Understanding the interaction between boehmite and epoxy and the formation of their interphases with different mechanical and chemical structures is crucial to predict and optimize the properties of epoxy-boehmite nanocomposites. Probing the interfacial properties with atomic force microscopy (AFM)-based methods, especially particle-matrix long-range interactions, is challenging. This is due to size limitations of various analytical methods in resolving nanoparticles and their interphases, the overlap of interphases, and the effect of buried particles that prevent the accurate interphase property measurement. Here, we develop a layered model system in which the epoxy is cured in contact with a thin layer of hydrothermally synthesized boehmite. Different microscopy methods are employed to evaluate the interfacial properties. With intermodulation atomic force microscopy (ImAFM) and amplitude dependence force spectroscopy (ADFS), which contain information about stiffness, electrostatic, and van der Waals forces, a soft interphase was detected between the epoxy and boehmite. Surface potential maps obtained by scanning Kelvin probe microscopy (SKPM) revealed another interphase about one order of magnitude larger than the mechanical interphase. The AFM-infrared spectroscopy (AFM-IR) technique reveals that the soft interphase consists of unreacted curing agent. The long-range electrical interphase is attributed to the chemical alteration of the bulk epoxy and the formation of new absorption bands. KW - Nanocomposites KW - Interphase KW - Intermodulation AFM KW - Electron microscopy KW - Infrared nano AFM PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-483672 UR - https://www.mdpi.com/2079-4991/9/6/853/htm DO - https://doi.org/10.3390/nano9060853 SN - 2079-4991 VL - 9 IS - 6 SP - 853, 1 EP - 20 PB - MDPI AN - OPUS4-48367 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Crasselt, Claudia A1 - Schmidt, Wolfram A1 - Sturm, Heinz T1 - Influence of rheology modifying admixtures on early hydration of cementitious suspensions N2 - The presence of polycarboxylate ether (PCE) based superplasticizers (SPs) has enormous influence on the early hydration of cement. C3A as the most reactive phase of Portland cement plays a significant role in early hydration reactions and affects the rheological performance. Therefore, this paper presents experimental results about the influence of delayed addition of PCEs on the Hydration of cement and C3A-gypsum pastes investigated by isothermal heat flow calorimetry. Complementary in-situ XRD was carried out on C3A pastes to analyze hydration and phase changes related to the addition of PCE. Cement pastes with a delayed addition of PCE showed less Retardation compared to simultaneous addition. The alteration caused by PCE is much more pronounced for C3A-gypsum mixes. With a delayed addition of SP, the hydration of C3A is less retarded or even accelerated. It is obvious that there is less retardation the later the addition of SP. Furthermore, the PCE alter the hydration of C3A when added delayed and exhibit changes in kinetics and hydration rates. XRD results showed that more C3A is dissolved in the presence of PCE. Also, the gypsum depletion occurs earlier in the presence of PCE and even faster with delayed addition. Without PCE AFm starts to form just after the gypsum depletion. However, in the presence of PCE AFm already starts to form at the beginning of the hydration. Due to the faster gypsum depletion in the presence of PCE, also the transformation from ettringite into AFm begins earlier, but takes longer as without SP. T2 - 15th International Congress on the Chemistry of Cement CY - Prague, Czech Republic DA - 16.09.2019 KW - Cement KW - C3A KW - Early hydration KW - Polycarboxylate ether (PCE) KW - Delayed addition PY - 2019 SP - 1 EP - 8 AN - OPUS4-49104 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -