TY - CHAP A1 - Sokolowski-Tinten, K. A1 - Bonse, Jörn A1 - Barty, A. A1 - Chapman, H.N. A1 - Bajt, S. A1 - Bogan, M.J. A1 - Boutet, S. A1 - Cavalleri, A. A1 - Düsterer, S. A1 - Frank, M. A1 - Hajdu, J. A1 - Hau-Riege, S. A1 - Marchesini, S. A1 - Stojanonovic, N. A1 - Treusch, R. ED - Stoian, R. ED - Bonse, Jörn T1 - In-Situ Observation of the Formation of Laser-Induced Periodic Surface Structures with Extreme Spatial and Temporal Resolution N2 - Irradiation of solid surfaces with intense ultrashort laser pulses represents a unique way of depositing energy into materials. It allows to realize states of extreme electronic excitation and/or very high temperature and pressure and to drive materials close to and beyond fundamental stability limits. As a consequence, structural changes and phase transitions often occur along unusual pathways and under strongly nonequilibrium conditions. Due to the inherent multiscale nature—both temporally and spatially—of these irreversible processes, their direct experimental observation requires techniques that combine high temporal resolution with the appropriate spatial resolution and the capability to obtain good quality data on a single pulse/event basis. In this respect, fourth-generation light sources, namely, short wavelength and short pulse free electron lasers (FELs), are offering new and fascinating possibilities. As an example, this chapter will discuss the results of scattering experiments carried out at the FLASH free electron laser at DESY (Hamburg, Germany), which allowed us to resolve laser-induced structure formation at surfaces on the nanometer to submicron length scale and in temporal regimes ranging from picoseconds to several nanoseconds with sub-picosecond resolution. KW - Laser-induced periodic surface structures, LIPSS KW - Capillary waves KW - Time-resolved scattering KW - Pump-probe experiments KW - Free electron laser PY - 2023 SN - 978-3-031-14751-7 SN - 978-3-031-14752-4 DO - https://doi.org/10.1007/978-3-031-14752-4_6 VL - 239 SP - 257 EP - 276 PB - Springer Nature Switzerland AG CY - Cham, Switzerland AN - OPUS4-57297 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Richter, Anja T1 - Reducing Escherichia coli adhesion to PET by modulating spatial periods of laser-induced surface nanoripples N2 - Using nanofiber-like cell appendages, secreted proteins and sugars, bacteria can establish initial surface contact followed by irreversible adhesion and the formation of multicellular biofilms. Here, the stabilizing extracellular biofilm matrix together with physiological changes on the single cell level leads to an increased resilience towards harsh environmental conditions, antimicrobials, the host immune response and established cleaning procedures. Persistent microbial adhesion on e.g., medical implants, in water supply networks or food-processing industry is often associated with chronic inflammation, nosocomial and foodborne infections, enhanced biofouling and product contamination. To prevent persistent microbial colonization, antibacterial surface strategies often target the initial steps of biofilm formation and impede adhesion of single cells before a mature biofilm is being formed. While chemical coatings have been widely used, their restricted biocompatibility for eukaryotic cells and attenuated antibacterial-effects due to compound release limit their areas of application and alternative strategies focus on modified surfaces topographies to impede bacterial adhesion. In this work, we used ns-UV laser treatment (wavelength 248 nm and a pulse duration of 20 ns) to generate laser-induced periodic surface structures (LIPSS) with different submicrometric periods ranging from ~210 to ~610 nm on commercial poly(ethylene terephthalate) (PET) foils. Following structurally and chemically analyses, PET samples were subjected to bacterial colonization studies with Escherichia coli TG1, a bacterial test strain with a strong biofilm formation capacity due to the formation of nanofiber-like cell-appendages (pili). Bacterial adhesion tests revealed that E. coli repellence decisively depends on the spatial periods of the LIPSS with the strongest reduction (~91%) in cell adhesion observed for LIPSS periods of 214 nm. Scanning electron microscopy and additional biofilm studies using a pili-deficient E. coli TG1 strain revealed the importance of extracellular appendages in the bacterial repellence observed here, thus, pointing out new antibiotics-free strategies for antibacterial surfaces by impeding nanofiber-mediated bacterial adhesion. T2 - E-MRS Spring Meeting 2022 CY - Online meeting DA - 30.05.2022 KW - Laser-induced periodic surface structures (LIPSS) KW - Bacterial adhesion tests KW - Bacteria repellent surfaces KW - Polymer foils KW - E. coli PY - 2022 AN - OPUS4-54930 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zorn, R. A1 - Szymoniak, Paulina A1 - Kolmangadi, Mohamed Aejaz A1 - Malpass-Evans, R. A1 - McKeown, N. A1 - Tyagi, M. A1 - Böhning, Martin A1 - Schönhals, Andreas T1 - Low frequency vibrations and diffusion in disordered polymers bearing an intrinsic microporosity as revealed by neutron scattering N2 - The microscopic diffusion and the low frequency density of states (VDOS) of PIM-EATB(CH3) are investigated by inelastic and quasi-elastic neutron scattering where also the demethylated counterpart of PIM-EA-TB(H2) is considered. These intrinsic microporous polymers are characterized by large BET surface area values of several hundred m2/g and pore sizes between 0.5 and 2 nm. Detailed comparison is made to the archetype of polymers of intrinsic microporosity, PIM-1, and polynorbornenes also bearing a microporosity. Due to the wavelength of neutrons, the diffusion and vibrations can be addressed on microscopic length and time scales. From the inelastic neutron scattering experiments the low frequency density of states (VDOS) is estimated which shows excess contributions to the Debye-type VDOS known as Boson peak. It was found that the maximum frequency of the Boson peak decreases with increasing microporosity characterized by the BET surface area. However, besides the BET surface area, additional factors such as the backbone stiffness govern the maximum frequency of the Boson peak. Further the mean squared displacement related to microscopic motions was estimated from elastic fixed window scans. At temperatures above 175 K, the mean squared displacement PIM-EA-TB(CH3) is higher than that for the demethylated counterpart PIM-EA-TB(H2). The additional contribution found for PIM-EATB(CH3) is ascribed to the rotation of the methyl group in this polymer because the only difference between the two structures is that PIM-EA-TB(CH3) has methyl groups where PIM-EA-TB(H2) has none. A detailed comparison of the molecular dynamics is also made to that of PIM-1 and the microporous polynorbornene PTCNSi1. The manuscript focuses on the importance of vibrations and the localized molecular mobility characterized by the microscopic diffusion on the gas Transport in polymeric separation membranes. In the frame of the random gate model localized fluctuations can open or close bottlenecks between pores to enable the diffusion of gas molecules. KW - Polymer of intrisic microporosity KW - Neutron scattering KW - Boson peak KW - Methyl group rotation PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-538490 DO - https://doi.org/10.3390/cryst11121482 VL - 11 IS - 12 SP - 1 EP - 16 PB - MDPI CY - Basel AN - OPUS4-53849 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Emamverdi, Farnaz A1 - Yin, Huajie A1 - Smales, Glen Jacob A1 - Harrison, W. J. A1 - Budd, P. M. A1 - Böhning, Martin A1 - Schönhals, Andreas T1 - Polymers of intrinsic microporosity - Molecular mobility and physical aging revisited by dielectric spectroscopy and X‑ray scattering N2 - Polymers of intrinsic microporosity (PIMs) are promising candidates for the active layer in gas separation membranes due to their high permeability and reasonable permselectivity. These appealing properties originate from a microporous structure as a result of inefficient segment packing in the condensed state due to a combination of a ladder-like rigid backbone and sites of contortion. However, this class of polymers suffers from a significant decrease in the permeability with time due to physical aging, whereby typically, the permselectivity increases. The initial microporous structures approach a denser state via local rearrangements, leading to the reduction of the permeability. Hence, a detailed characterization of the molecular mobility in such materials can provide valuable information on physical aging. In this work, the dielectric behavior of PIM-1 films and their behavior upon heating (aging) were revisited by isothermal frequency scans during different heating/cooling cycles over a broad temperature range between 133 and 523 K (−140 to 250 °C). In addition, the obtained results were compared with data of samples that were annealed at ambient temperatures over different time scales. Multiple dielectric processes were observed: several relaxation processes due to local fluctuations and a Maxwell−Wagner−Sillars polarization effect related to the microporosity. The temperature dependence of the rates of all processes follows the Arrhenius law where the estimated activation energy depends on the nature of the process. The influence of the thermal history (aging) on the processes is discussed in detail. KW - Polymers of intrinsic microporosity PY - 2022 DO - https://doi.org/10.1021/acs.macromol.2c00934 VL - 55 SP - 7340 EP - 7350 PB - American Chemical Society CY - Washington, DC AN - OPUS4-55485 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schönhals, Andreas A1 - Szymoniak, Paulina A1 - Kolmangadi, Mohamed Aejaz A1 - Böhning, Martin A1 - Zamponi, M. A1 - Frick, B. A1 - Appel, M. A1 - Günther, G. A1 - Russina, M. A1 - Alentiev, D. A1 - Bermeshev, M. A1 - Zorn, R. T1 - Microscopic dynamics of highly permeable super glassy polynorbornenes revealed by quasielastic neutron scattering N2 - The molecular dynamics of addition-type poly(tricyclononenes) with Si-substituted bulky side groups has been investigated by a combination of neutron time-of-flight and neutron backscattering spectroscopy methods on a time scale from 0.1 ps to ca. 3 ns. The investigated poly(tricyclononenes) PTCNSi1 and PTCNSi2g both bear a high microporosity which makes them promising candidates for active separation layers for gas separation membranes. At least for larger gas molecules it is assumed that the pathways for diffusion require an enlargement of pre-existing micropores in terms of an activated zone. A low temperature relaxation process was found for both polymers by the performed neutron scattering experiments. This process was assigned to the methyl group rotation. It was analysed in terms of a jump diffusion in a three-fold potential. The analysis of the dependence of the elastic incoherent structure factor on the scattering vector yields the number of methyl groups which might be immobilized. For PTCNSi1 (3 methyl groups in the monomeric unit) it was found that all methyl groups take part in the methyl group rotation whereas for PTCNSi2g (6 methyl groups in monomeric unit) a considerable number of methyl groups are blocked in their rotation. This immobilization of methyl groups is due to the sterically demanding arrangement of the methyl groups in PTCNSi2g. This conclusion is further supported by the result that the activation energy for the methyl group rotation is three times higher for PTCNSi2g than that of PTCNSi1. KW - Highly permeably polynorbornenes KW - Polymers of intrinsic microporosity KW - Gas separation membranes KW - Quasielastic neutron scattering PY - 2021 DO - https://doi.org/10.1016/j.memsci.2021.119972 SN - 0376-7388 VL - 642 PB - Elesevier B.V. AN - OPUS4-53508 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kolmangadi, Mohamed Aejaz A1 - Szymoniak, Paulina A1 - Smales, Glen Jacob A1 - Bermeshev, M. A1 - Schönhals, Andreas A1 - Böhning, Martin T1 - Molecular mobility of polynorbornenes with trimethylsiloxysilyl side groups: Influence of the polymerization mechanism N2 - We report dielectric and calorimetric studies on metathesis and addition-type polytricyclononenes, both based on the same monomer bearing three pendant OSiMe3 groups. For the addition-type polymer, dielectric spectroscopy reveals a β*-process related to the microporosity, whereas for its metathesis counterpart, the segmental dynamics manifests as an α-process related to a glass transition. Besides active dielectric processes, a significant conductivity contribution is detected for both samples which for the microporous additiontype polymer is three orders of magnitude greater than for the metathesis polymer. The broadband dielectric spectroscopy is complemented by detailed calorimetric investigations, comprising DSC, FSC, and TMDSC. The calorimetric methods detected the glass transition for the metathesis polymer in agreement with the observed dielectric α-process. Furthermore, the already reported gas transport properties for both polymers are compared, setting them in correlation with the observed molecular mobility and conductivity behavior. The discussed results reflect significant differences in molecular mobility of the two polymers affecting the appearance of microporosity which strongly determines the gas transport properties. KW - Microporous polymers KW - Molecular mobility KW - Electrical conductivity KW - Membrane polymers KW - Gas separation PY - 2022 DO - https://doi.org/10.22079/JMSR.2021.538060.1495 SN - 2476-5406 VL - 8 IS - 3 SP - 1 EP - 9 PB - Membrane Processes Research Laboratory (MPRL) CY - Tehran AN - OPUS4-54303 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schönhals, Andreas T1 - Inelastic neutron scattering as a tool to investigate  polymers of intrinsic microporosity for green membrane processes and electronic applications N2 - Polymers with intrinsic microporosity are promising candidates for the active separation layer in green gas separation membranes and as active materials for electronic applicatons. Here, by means of inelastic neutron scattering, the vibrational density of states (VDOS) and the molecular mobility were investigated for PIM-1, the prototypical polymer with intrinsic microporosity. The results are compared to data measured for a more conventional high-performance polyimide used in gas separation membranes (Matrimid). The measured data show the characteristic low frequency excess contribution to the VDOS above the Debye sound wave level, generally known as the Boson peak in glass-forming materials. In comparison to the Boson peak of Matrimid, that of PIM-1 is shifted to lower frequencies. This shift is discussed considering the microporous, sponge-like structure of PIM-1 as providing a higher compressibility at the molecular scale than for conventional polymers. Elastic fixed window scans were measured on a neutron backscattering spectrometer to have an overview about the molecular dynamics at a time scale of ca. 1 ns. The temperature dependence of the estimated mean squared displacement shows a step-like increase in the temperature range from 100 K to 250 K indicating the onset of some molecular mobility. The nature of this motional process was analysed in detail by quasielastic neutron scattering combining Time-of-Flight and backscattering where the data are discussed with regard to both the q- and the temperature dependence. T2 - Symposium on Large Scale Facilities CY - Berlin, Germany DA - 09.03.2020 KW - Polymer membranen PY - 2020 AN - OPUS4-50546 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Maiwald, Michael A1 - Villajos Collado, José Antonio T1 - Metal-organic framework compounds as hydrogen storage materials to enhance the safety, capacity, and efficiency of hydrogen refueling stations N2 - Gas adsorption is based on physical properties between gases and solid materials, enriching the surface with packed gas molecules with a higher density than in the bulk phase. For using this mechanism as a gas storage strategy, highly porous materials are necessary since large surfaces in small volumes can provide the storage system with a higher density than the gas phase. In the case of hydrogen gas, the interaction forces with solid surfaces are generally low at room temperature but can increase considerably at low operating temperatures. As a counterpart, the storage pressure is considerably lower than that necessary by traditional gas compression. Amongst ultra-porous adsorbent materials for hydrogen cryoadsorption, metal-organic frameworks (MOFs) are a group of remarkable solids made from metallic nodes linked by organic molecules exhibiting a wide variety of composition, geometry, porous properties, and chemical functionality. The scientific community focused in the last years on enhancing both the specific area of materials and the interaction energy to extend the storage properties of cryoadsorption to ambient-temperature and use it as hydrogen storage mechanisms in vehicles. However, the found difficulty in achieving ultra-porous structures with high-enough interaction energies decreased this research interest in the last years. However, for a stationary application like hydrogen refueling stations, where space and weight are not such limits as in vehicles, cryoadsorption can still be considered a feasible candidate for hydrogen storage. Cryoadsorption is the only fast and fully reversible approach to store hydrogen at similar density values as compressed gas. Cryogenic operation is a technological challenge, but first, liquid nitrogen is cheap, and second, it is less energy-demanding than hydrogen liquefaction, which is indeed considered as feasible for transportation and storage. Cryoadsorption involves lower pressure than compressed gas, increasing safety in the storage facilities, but additional research on the construction materials properties is necessary to better understand their behavior in contact with hydrogen at cryogenic temperatures. However, the knowledge of all these mechanisms is important to identify the improvement opportunities based on, probably, the interphase between different solutions. To achieve the set project goals, this internal research report describes the work packages realised within the framework of the project. KW - Metal-organic frameworks (MOFs) KW - Hydrogen Storage KW - Reversible Hydrogen Storage KW - Hydrogen Fuelling Stations KW - Croyo-starage KW - High-pressure volumetric analyzer (HPVA) PY - 2021 SP - 1 EP - 48 CY - Berlin AN - OPUS4-53582 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Falqueto, J. B. A1 - Clark, A. H. A1 - Štefančič, A. A1 - Smales, Glen Jacob A1 - Vaz, C. A. F. A1 - Schuler, A. J. A1 - Bocchi, N. A1 - Kazzi, M. E. T1 - High performance doped Li-rich Li1+xMn2–xO4 cathodes nanoparticles synthesized by facile, fast, and efficient microwave-assisted hydrothermal route N2 - Li-rich nanoparticles of Li1+xMn2–xO4 doped with Al, Co, or Ni are successfully synthesized using a facile, fast, and efficient microwave-assisted hydrothermal route. Synchrotron X-ray diffraction confirms the formation of the crystalline cubic spinel phase type. X-ray absorption spectroscopy analysis at the Co and Ni K- and L-edges verifies that the dopants are within the Li1+xMn2–xO4 spinel structure and are inactive during cycling in the bulk and at the surface. Moreover, we demonstrate that nanocrystallinity and cationic doping play an important role in improving the electrochemical performance with respect to LiMn2O4 microparticles. They significantly reduce the charge-transfer resistance, lower the first cycle irreversible capacity loss to 6%, and achieve a capacity retention between 85 and 90% after 380 cycles, with excellent Coulombic efficiency close to 99% without compromising the specific charge at a 5C cycling rate. Furthermore, the Mn K- and L-edges attest that after long cycling, the Mn oxidation state in the bulk differs from that at the surface caused by the Mn disproportion reaction; however, the cationic doping helps mitigate the Mn dissolution with respect to the undoped Li1+xMn2–xO4 nanoparticles, as indicated by inductively coupled plasma atomic emission spectrometry. KW - XAS KW - SAXS KW - Li-ion battery KW - Cathode material KW - Spinel KW - The MOUSE PY - 2022 DO - https://doi.org/10.1021/acsaem.2c00902 SN - 2574-0962 VL - 5 IS - 7 SP - 8357 EP - 8370 PB - ACS Publ. CY - Washington, DC AN - OPUS4-55359 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Wetzel, Annica A1 - Oczan, Ozlem A1 - Nietzke, Jonathan A1 - Richter, Tim A1 - Schröpfer, Dirk T1 - Hydrogen diffusion and local Volta potential in high- and medium-entropy alloys N2 - High-entropy alloys (HEAs) are characterized by a solid solution of minimum five and medium-entropy alloys (MEAs) of minimum three principal alloying elements in equiatomic proportions. They show exceptional application properties, such as high-strength and ductility or corrosion resistance. Future HEA/MEA-components could be exposed to hydrogen containing environments like vessels for cryogenic or high-pressure storage where the hydrogen absorption and diffusion in these materials is of interest. In our study, we investigated the HEA Co20Cr20Fe20Mn20Ni20 and the MEA Co33.3Cr33.3Ni33.3. For hydrogen ingress, cathodic charging was applied and diffusion kinetic was measured by high-resolution thermal desorption spectros-copy using different heating rates up to 0.250 K/s. Peak deconvolution resulted in high-temperature desorption peaks and hydrogen trapping above 280 °C. A total hydrogen concentration > 40 ppm was identified for the MEA and > 100 ppm for HEA. This indicates two important effects: (1) delayed hydrogen diffusion and (2) considerable amount of trapped hydrogen that must be anticipated for hydrogen assisted cracking phenomenon. Local electrochemical Volta potential maps had been measured for the hydrogen free condition by means of high-resolution Scanning Kelvin Probe Force Microscopy (SKPFM). T2 - Symposium on Materials and Joining Technology CY - Online meeting DA - 07.09.2020 KW - Hydrogen KW - High-entropy alloy KW - Diffusion KW - Scanning kelvin probe force microscopy KW - Corrosion PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-511684 DO - https://doi.org/10.1088/1757-899X/882/1/012015 VL - 882 SP - 1 EP - 15 PB - IOP Publishing CY - Bristol AN - OPUS4-51168 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Batatia, Ilyes A1 - Benner, Philipp A1 - Chiang, Yuan A1 - Elena, Alin M. A1 - Kovács, Dávid P. A1 - Riebesell, Janosh A1 - Advincula, Xavier R. A1 - Asta, Mark A1 - Avaylon, Matthew A1 - Baldwin, William J. A1 - Berger, Fabian A1 - Bernstein, Noam A1 - Bhowmik, Arghya A1 - Bigi, Filippo A1 - Blau, Samuel M. A1 - Cărare, Vlad A1 - Ceriotti, Michele A1 - Chong, Sanggyu A1 - Darby, James P. A1 - De, Sandip A1 - Della Pia, Flaviano A1 - Deringer, Volker L. A1 - Elijošius, Rokas A1 - El-Machachi, Zakariya A1 - Fako, Edvin A1 - Falcioni, Fabio A1 - Ferrari, Andrea C. A1 - Gardner, John L. A. A1 - Gawkowski, Mikołaj J. A1 - Genreith-Schriever, Annalena A1 - George, Janine A1 - Goodall, Rhys E. A. A1 - Grandel, Jonas A1 - Grey, Clare P. A1 - Grigorev, Petr A1 - Han, Shuang A1 - Handley, Will A1 - Heenen, Hendrik H. A1 - Hermansson, Kersti A1 - Ho, Cheuk Hin A1 - Hofmann, Stephan A1 - Holm, Christian A1 - Jaafar, Jad A1 - Jakob, Konstantin S. A1 - Jung, Hyunwook A1 - Kapil, Venkat A1 - Kaplan, Aaron D. A1 - Karimitari, Nima A1 - Naik, Aakash A. A1 - Csányi, Gábor T1 - A foundation model for atomistic materials chemistry N2 - Atomistic simulations of matter, especially those that leverage first-principles (ab initio) electronic structure theory, provide a microscopic view of the world, underpinning much of our understanding of chemistry and materials science. Over the last decade or so, machine-learned force fields have transformed atomistic modeling by enabling simulations of ab initio quality over unprecedented time and length scales. However, early machine-learning (ML) force fields have largely been limited by (i) the substantial computational and human effort required to develop and validate potentials for each particular system of interest and (ii) a general lack of transferability from one chemical system to the next. Here, we show that it is possible to create a general-purpose atomistic ML model, trained on a public dataset of moderate size, that is capable of running stable molecular dynamics for a wide range of molecules and materials. We demonstrate the power of the MACE-MP-0 model—and its qualitative and at times quantitative accuracy—on a diverse set of problems in the physical sciences, including properties of solids, liquids, gases, chemical reactions, interfaces, and even the dynamics of a small protein. The model can be applied out of the box as a starting or “foundation” model for any atomistic system of interest and, when desired, can be fine-tuned on just a handful of application-specific data points to reach ab initio accuracy. Establishing that a stable force-field model can cover almost all materials changes atomistic modeling in a fundamental way: experienced users obtain reliable results much faster, and beginners face a lower barrier to entry. Foundation models thus represent a step toward democratizing the revolution in atomic-scale modeling that has been brought about by ML force fields. KW - Materials Design KW - Thermal Conducitivity KW - Nanoparticles KW - Batteries PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-647829 DO - https://doi.org/10.1063/5.0297006 SN - 0021-9606 VL - 163 IS - 18 SP - 1 EP - 89 PB - AIP Publishing AN - OPUS4-64782 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sachse, René T1 - Operando electrochemical spectroscopic ellipsometry: Material properties of highly active mesoporous IrO IrOxfilms revealed under realistic OER conditions N2 - Rising energy demand and the impending climate change require the development of a sustainable, fossil-free fuel and chemical production on a global scale. Hydrogen production via water electrolysis will be a fundamental cornerstone in this endeavor. The activity and stability of respective electrode coatings strongly depends on the coating's properties, i.e. phase composition, crystallinity, electrical conductivity, accessible surface, wettability and many other factors. The key to the development of improved catalysts is a better understanding of the relations between their performance, stability and physicochemical properties. However, those relations can be complex, and are strongly influenced also by the reaction environment. Hence, operando analysis of the catalyst material during catalysis at realistic potentials and current densities is highly desirable. Yet, many analytical techniques cannot be applied in liquid environments at realistic potentials and current densities. We propose environmental ellipsometric analysis in a dedicated electrochemical flow cell as a new method to evaluate gas evolution reactions operando under realistic working conditions. Figure 1 illustrates schematically the developed technique. Key factors to success are highly active model-type catalysts with template-controlled porosity, a suitable sample environment, a deep understanding of the spectroscopic method and respective model development, as well as concise cross validation with numerous other analytical techniques. The method was developed and validated by analyzing a calcination series (300 - 600°C) of mesoporous templated IrOx films ex-situ and operando under oxygen evolution reaction (OER) conditions. The employed environmental electrochemical spectroscopic ellipsometric analysis (ECSE) revealed during OER the change of optical and electronic properties, i.e. the dielectric functions (real ε1 and imaginary part ε2), electrical and electronic properties such as resistivity (ρ) and band-to-band transitions (p-d band transitions). Film thickness and porosity were validated by means of scanning electron microscopy (SEM), X-ray reflectometry (XRR) or ellipsometric porosimetry (EP), electrical and electronic properties by means of conductivity measurements, X-ray photoelectron spectroscopy (XPS) or UV-Vis-NIR absorption spectroscopy. The electronic structures of the catalysts from valence electron energy loss spectra (VEELS) derived from the real (ε1) and imaginary part (ε2) of the dielectric function from SE measurements reveal a direct correlation with electrochemical activities in OER. In the presentation reversible and irreversible potential-dependent changes of the catalyst properties during operation will be discussed along with the dynamics of gas formation, transport and dissolution at different potentials. T2 - 54. Jahrestreffen deutscher Katalytiker CY - Online meeting DA - 16.03.2021 KW - Spectroscopic ellipsometry KW - Electrocatalysis KW - Oxygen evolution reaction KW - Mesoporous iridium oxide films KW - Non-destructive operando analysis PY - 2021 AN - OPUS4-52928 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hodoroaba, Vasile-Dan T1 - Chemical Nanoscale Analysis of Mesoporous Mixed IrOx-TiOx Thin Films N2 - Porous films play an important role particularly in energy applications like photovoltaics, electrolysis or batteries. Thin film properties such as thickness, chemical composition, crystallinity of the framework, and porosity define the activity of the porous films. The accurate morpho-chemical characterisation of mesoporous thin films is a challenging analytical task which requires the consideration of new analytical approaches based on the combination of data of different methods able to address the structure and chemical composition at the nanoscale. In this contribution we characterise thin mesoporous iridium-titanium mixed oxide film properties by Electron Probe Microanalysis (EPMA) with Energy-Dispersive X-ray Spectroscopy (EDS) at an SEM applied in a dedicated “thin film analysis” approach. Thus, the film mass deposition, film thickness and the film density can be determined. Further, by dividing the measured film density to an assumed (theoretical) metal oxide framework (skeletal) density, the thin film porosity can be extracted, too. In order to assess the homogeneity of the thin film properties like the chemical composition, Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and Auger Electron Spectrometry are applied in the depth profiling mode, so that possible in-depth gradients are detected. Lateral inhomogeneities in the chemical composition and structure of the thin mesoporous films are also identified by applying the same methods in the line-scan or mapping mode, which can be further combined with in-depth sputtering for 3D information. The role of the spatial resolution of the analytical methods considered, which can go down well below 100 nm, will be highlighted. T2 - MaterialsWeek 2024 CY - Limassol, Cyprus DA - 17.06.2024 KW - Thin films KW - Mesoporous KW - IR oxide KW - Ti oxide KW - Porosity PY - 2024 AN - OPUS4-60452 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Salzmann, Christoph A1 - Heilmann, Maria A1 - Pellegrino, Francesco A1 - Durand, Bénédicte A1 - Taché, Olivier A1 - Zurutuza, Amaia A1 - Hodoroaba, Vasile-Dan T1 - Ongoing International Interlaboratory Comparisons on Size, Shape and (Relative) Concentration of Complex Nanoparticles under the Pre-Standardization Platform of VAMAS N2 - An overview with the basics of size and shape measurement of particles and 2D structures according to established methodologies (and popular imaging processing software packages) with imaging techniques is given. Main descriptors are explained based on case studies with ongoing interlaboratory comparisons under the pre-standardisation platform of VAMAS. KW - VAMAS KW - Interlaboratory comparison KW - Imaging KW - Size distribution KW - Particle concentration KW - 2D materials PY - 2024 DO - https://doi.org/10.1093/mam/ozae044.319 VL - 30 IS - Supplement 1 SP - 669 EP - 670 PB - Oxford University Press (OUP) AN - OPUS4-61183 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Knigge, Xenia A1 - Radnik, Jörg T1 - Advanced materials for the energy transition N2 - The climate crisis is the burning issue of our time. In order to avert the impending consequences, global efforts are being made in a wide variety of social and scientific fields. This report looks at a small part of these efforts, a technical aspect, namely the question of which AdMa are currently considered in techniques to support the energy transition. AdMa, i.e. materials that are rationally designed to have new or enhanced properties, and/or targeted or enhanced structural features, are used in all sectors of the energy transition. Questions of energy generation, storage and saving are considered here. This report is based on literature research and contains a general compilation of various AdMa that are used in the energy transition or are being researched for this purpose. From this compilation, ten materials that are considered particularly relevant for various reasons were selected and examined in more detail in relation to their use. The specific question here lies in the conflicting objective that the development of technologies for the energy transition is welcomed, but the use of AdMa may entail possible challenges in view of chemical safety as well as sustainability and circular economy. KW - Energy generation KW - Energy saving KW - Eneergy storage KW - Energy transportation PY - 2025 DO - https://doi.org/10.60810/openumwelt-7853 SN - 1862-4804 VL - 83 SP - 1 EP - 64 PB - Umweltbundesamt CY - Dessau-Roßlau AN - OPUS4-63529 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Radnik, Jörg T1 - Investigation of Fe-Ni-O nanoparticles for water splitting N2 - This study investigates the effect of varying iron-to-nickel ratios on the catalytic performance of Fe-Ni oxide nanoparticles (NPs) for the oxygen evolution reaction (OER). Addressing the issue of high energy wastage due to large overpotentials in OER, we synthesized and characterized different NP catalysts with different Fe: Ni oxide ratios. Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-ray Diffraction (XRD) were employed to determine the morphology, elemental and phase composition of the NPs. Furthermore, in-depth profiling with X-rayPhotoelectron Spectroscopy (XPS) and Hard X-ray Photoelectron Spectroscopy (HAXPES) revealedthat iron predominantly exists as oxide, while nickel exhibits both metallic and oxidic forms depending on the Fe content. XPS indicated an enrichment of iron at the NP surface, whereas HAXPES and EDSdata agreed on the bulk stoichiometry. T2 - PhI European User Meeting 2025 CY - Eibelstadt, Germany DA - 29.04.2025 KW - Oxygen evolution reaction KW - In depth analysis KW - (Hard) X-ray Photoelectron Spectroscopy PY - 2025 AN - OPUS4-63334 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Radnik, Jörg T1 - Methodological Challenges and Gaps: Physico-Chemical Characterisation N2 - The methodological challenges and gaps in the physico-chemical characterisation of graphene related 2D Materials (GR2M) are discussed. Solutions for filling the gaps are presented. T2 - OECD Graphene Expert Workshop CY - Paris, France DA - 26.11.2024 KW - Graphene related 2D materials KW - Structure activity relationsships KW - Classification PY - 2024 AN - OPUS4-61920 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhao, H. A1 - Chakraborty, Poulami A1 - Ponge, D. A1 - Hickel, Tilmann A1 - Sun, B. A1 - Wu, C.-H. A1 - Gault, B. A1 - Raabe, D. T1 - Hydrogen trapping and embrittlement in high-strength Al alloys N2 - Ever more stringent regulations on greenhouse gas emissions from transportation motivate efforts to revisit materials used for vehicles. High-strength aluminium alloys often used in aircrafts could help reduce the weight of automobiles, but are susceptible to environmental degradation. Hydrogen ‘embrittlement’ is often indicated as the main culprit; however, the exact mechanisms underpinning failure are not precisely known: atomic-scale analysis of H inside an alloy remains a challenge, and this prevents deploying alloy design strategies to enhance the durability of the materials. Here we performed near-atomic-scale analysis of H trapped in second-phase particles and at grain boundaries in a high-strength 7xxx Al alloy. We used these observations to guide atomistic ab initio calculations, which show that the co-segregation of alloying elements and H favours grain boundary decohesion, and the strong partitioning of H into the second-phase particles removes solute H from the matrix, hence preventing H embrittlement. Our insights further advance the mechanistic understanding of H-assisted embrittlement in Al alloys, emphasizing the role of H traps in minimizing cracking and guiding new alloy design. KW - Atomistic models KW - Hydrogen KW - Metals and alloys KW - Mechanical properties PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543631 DO - https://doi.org/10.1038/s41586-021-04343-z SN - 1476-4687 VL - 602 IS - 7897 SP - 437 EP - 441 PB - Nature Publ. Group CY - London AN - OPUS4-54363 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mendive Tapia, Eduardo A1 - Patrick, Christopher E A1 - Hickel, Tilmann A1 - Neugebauer, Jörg A1 - Staunton, Julie B T1 - Quantification of electronic and magnetoelastic mechanisms of first-order magnetic phase transitions from first principles: application to caloric effects in La(FexSi1-x)(13) N2 - La(FexSi1−x)13 and derived quaternary compounds are well-known for their giant, tunable, magneto- and barocaloric responses around a first-order paramagnetic-ferromagnetic transition near room temperature with low hysteresis. Remarkably, such a transition shows a large spontaneous volume change together with itinerant electron metamagnetic features. While magnetovolume effects are well-established mechanisms driving first-order transitions, purely electronic sources have a long, subtle history and remain poorly understood. Here we apply a disordered local moment picture to quantify electronic and magnetoelastic effects at finite temperature in La(FexSi1−x)13 from first-principles. We obtain results in very good agreement with experiment and demonstrate that the magnetoelastic coupling, rather than purely electronic mechanisms, drives the first-order character and causes at the same time a huge electronic entropy contribution to the caloric response. KW - Caloric effects KW - Ab initio thermodynamics KW - Magnetoeleastic couplin PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-587882 DO - https://doi.org/10.1088/2515-7655/acd027 SN - 2515-7655 VL - 5 IS - 3 SP - 1 EP - 16 PB - IOP Publishing AN - OPUS4-58788 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tehranchi, Ali A1 - Chakraborty, Poulami A1 - López Freixes, Martí A1 - McEniry, Eunan J. A1 - Gault, Baptiste A1 - Hickel, Tilmann A1 - Neugebauer, Jörg T1 - Tailoring negative pressure by crystal defects: Microcrack induced hydride formation in Al alloys N2 - Climate change motivates the search for non-carbon-emitting energy generation and storage solutions. Metal hydrides show promising characteristics for this purpose. They can be further stabilized by tailoring the negative pressure of microstructural and structural defects. Using systematic ab initio and atomistic simulations, we demonstrate that an enhancement in the formation of hydrides at the negatively pressurized tip region of the microcrack is feasible by increasing the mechanical tensile load on the specimen. The theoretical predictions have been used to reassess and interpret atom probe tomography experiments for a high-strength 7XXX-aluminium alloy that show a substantial enhancement of hydrogen concentration at structural defects near a stress-corrosion crack tip. These results contain important implications for enhancing the capability of metals as H-storage materials. KW - Physics and Astronomy (miscellaneous) KW - Hydrogen storage KW - Ab initio Simulation KW - Microcracks PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-587878 DO - https://doi.org/10.1103/PhysRevMaterials.7.105401 SN - 2475-9953 VL - 7 IS - 10 SP - 105401-1 EP - 105401-12 PB - American Physical Society (APS) AN - OPUS4-58787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -