TY - JOUR A1 - Yin, Huajie A1 - Chapala, P. A1 - Bermeshev, M. A1 - Pauw, Brian Richard A1 - Schönhals, Andreas A1 - Böhning, Martin T1 - Influence of Trimethylsilyl Side Groups on the Molecular Mobility and Charge Transport in Highly Permeable Glassy Polynorbornenes N2 - Superglassy polymers with a large fractional free volume have emerged as novel materials with a broad range of applications, especially in the field of membrane separations. Highly permeable addition-type substituted polynorbornenes with high thermal resistance and chemical stability are among the most promising materials. The major obstacle for extending the practical membrane application is their strong tendency to physical aging, leading to a partial decline in their superior transport performance over time. In the present study, broadband dielectric spectroscopy with complementary X-ray scattering techniques were employed to reveal changes in microporous structure, molecular mobility, and conductivity by systematic comparison of two polynorbornenes with different numbers of trimethylsilyl side groups. Their response upon heating (aging) was compared in terms of structure, dynamics, and charge transport behavior. Furthermore, a detailed analysis of the observed Maxwell−Wagner−Sillars polarization at internal interfaces provides unique information about the microporous structure in the solid films. The knowledge obtained from the experiments will guide and unlock potential in synthesizing addition-type polynorbornenes with versatile properties. KW - Dielectric spectroscopy KW - Molecular mobility KW - Electrical conductivity KW - Gas separation membranes PY - 2019 DO - https://doi.org/10.1021/acsapm.9b00092 SN - 2637-6105 VL - 1 IS - 4 SP - 844 EP - 855 PB - ACS CY - Washington DC AN - OPUS4-47838 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yin, Huajie A1 - B, Yang A1 - Chua, Y. Z. A1 - Szymoniak, Paulina A1 - Carta, M A1 - Malpass-Evans, R A1 - McKeown, N A1 - Harrison, W A1 - Budd, P A1 - Schick, C A1 - Böhning, Martin A1 - Schönhals, Andreas T1 - Effect of backbone rigidity on the glass transition of polymers of in-trinsic microporosity probed by fast scanning calorimetry N2 - Polymers of Intrinsic Microporosity (PIMs) of high performance have developed as materials with a wide application range in gas separation and other energy-related fields. Further optimization and long-term behavior of devices with PIMs require an understanding of the structure-property relationships including physical aging. In this context the glass transi-tion plays a central role, but with conventional thermal analysis a glass transition is usually not detectable for PIMs be-fore their thermal decomposition. Fast scanning calorimetry provides evidence of the glass transition for a series of PIMs, as the time scales responsible for thermal degradation and for the glass transition are decoupled by employing ultrafast heating rates of tens of thousands K s-1. The investigated PIMs were chosen considering the chain rigidity. The estimated glass transition temperatures follow the order of the rigidity of the backbone of the PIMs. KW - Polymers of intrinsic microporosity KW - Fast scanning calormetry PY - 2019 DO - https://doi.org/10.1021/acsmacrolett.9b00482 SN - 2161-1653 VL - 8 IS - 8 SP - 1022 EP - 1028 PB - ACS Publications AN - OPUS4-48617 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yin, Huajie A1 - Schönhals, Andreas A1 - Böhning, Martin T1 - Molecular Mobility and Charge Transport in Polymers of Intrinsic Microporosity (PIMs) as Revealed by Dielectric Spectroscopy N2 - Polymeric membranes represent a low-cost, energy efficient solution for gas separation. Recently polymers of intrinsic microporosity (PIMs) have emerged as prestigious membrane materials featuring a large concentration of pores smaller than 1 nm, a BET surface area larger than 700 m2/g and high gas permeability and selectivity. Unusual chain structure combining rigid segments with sites of contortion gives rise to the intrinsic microporosity. However, this novel class of glassy polymers are prone to pronounced physical aging. The initial microporous structures approach a denser state via local small scale fluctuataions, leading to a dramatic reduction in the gas permeabilities. For the first time, dielectric relaxation spectroscopy with state-of-the-art high-resolution analyzers was employed to investigate three representative PIMs with a systematic change in chain rigidity: PIM-EA-TB 〉 PIM-1 〉 PIM-MDPH-TB. The molecular mobility, the charge transport and their response upon heating (aging) in the polymers were measured in a broad temperature range through isothermal frequency scans during different heating / cooling cycles. Multiple dielectric processes following Arrhenius behavior were observed for the investigated polymers. Local fluctuations, Maxwell-Wagner-Sillars (MWS) polarization and structural relaxation phenomena were discussed and attempted to be correlated with the structural features of PIMs. Moreover, all PIMs showed conductivity in the glassy state. The significant increase in the conductivity with increasing temperature far below the glass transition temperature of PIMs is explained in terms of the loosely packed microporous structure and the formation of local intermolecular agglomerates due to interaction of π-electrons in aromatic moieties of the polymer backbone. T2 - American Chemical Society (ACS) National Meeting & Expo 2019 CY - Orlando, FL, USA DA - 31.03.2019 KW - Dielectric spectroscopy KW - Polymeric membrane KW - Polymers of intrinsic microporosity PY - 2019 AN - OPUS4-47805 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yin, Huajie A1 - Chua, Y. Z. A1 - Yang, B. A1 - Schick, C. A1 - Böhning, Martin A1 - Schönhals, Andreas T1 - Probing the glass transition temperature of polymers of intrinsic microporosity (PIMs) by fast scanning calorimeter N2 - High performance polymers of intrinsic microporosity (PIMs) have emerged as novel materials with broad applications from gas separation to electronic devices. Sufficiently rigid, even contorted polymer chains show only limited molecular mobility, therefore undergo inefficient packing and give rise to intrinsic microporosity with pore size generally smaller than 1 nm and BET surface areas larger than 700 m2/g. Further performance optimization and long-term stability of devices incorporating PIMs rely on our understanding of structure-processing-property relationships and physical aging, in which glass transition plays a key role. Up to now no glass transition temperature (Tg) of PIMs could be detected with conventional thermal analysis techniques before degradation. Decoupling the time scales responsible for the glass transition and the thermal decomposition is a reliable strategy to overcome this. This was achieved by employing fast scanning calorimetry (FSC) based on a chip sensor, which is capable to heat and cool a small sample (ng-range) with ultrafast rates of several ten thousand K/s. FSC provides definitive evidence of glass transition of a series of PIMs with a special consideration on the chain rigidity. The determined glass transition temperature of these PIMs follows the order of the rigidity of their backbone structures. FSC provides the first clear-cut experimental evidence of the glass transition of PIM-EA-TB with a Tg of 663 K, PIM-1 of 644 K and PIM-DMDPH-TB of 630 K at a heating rate of 1Χ104 K/s. Local fluctuations are featured in glass transition of highly rigid PIMs. As conformational changes are prevented by the backbone rigidity, the glass transition must rather be assigned to local small scale fluctuations. T2 - American Chemical Society (ACS) National Meeting & Expo 2019 CY - Orlando, FL, USA DA - 31.03.2019 KW - Glass transition KW - Polymers of intrinsic microporosity KW - Fast scanning calorimeter PY - 2019 AN - OPUS4-47806 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yildirim, Arda A1 - Szymoniak, Paulina A1 - Sentker, K. A1 - Butschies, M. A1 - Bühlmeyer, A. A1 - Huber, P. A1 - Laschat, S. A1 - Schönhals, Andreas T1 - Dynamics and ionic conductivity of ionic liquid crystals forming a hexagonal columnar mesophase N2 - For the first time, the molecular mobility of two linear-shaped tetramethylated guanidinium triflate ionic liquid crystals (ILCs) having different length of alkyl chains were investigated by a combination of broadband dielectric spectroscopy (BDS) and specific heat spectroscopy (SHS). By self-assembly, these ILCs can form a hexagonal ordered mesophase besides plastic crystalline phases and the isotropic state. Three dielectric active processes were found by BDS for both samples. At low temperatures, a γ-process in the plastic crystalline state is observed which is assigned to localized fluctuations of methyl groups including nitrogen atoms in the guanidinium head. At higher temperatures but still in the plastic crystalline state, an α1-process takes place. An α2 process was detected by SHS but with a completely different temperature dependence of the relaxation times than that of the α1-relaxation. This result is discussed in detail, and different molecular assignments of the processes are suggested. At even higher temperatures, electrical conductivity is detected and an increase in the DC conductivity by four orders of magnitude at the phase transition from the plastic crystalline to the hexagonal columnar mesophase is found. This result is traced to a change in the charge transport mechanism from a delocalized electron hopping in the stacked aromatic systems (in the plastic phase) to one dominated by an ionic conduction in the quasi-1D ion channels formed along the supermolecular columns in the ILCs hexagonal mesophases. KW - Ionic liquid crystalls PY - 2018 DO - https://doi.org/10.1039/c7cp08186c SN - 1463-9084 SN - 1463-9076 VL - 20 IS - 8 SP - 5626 EP - 5635 PB - Royal Society of Chemistry AN - OPUS4-44254 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yildirim, Arda A1 - Sentker, K. A1 - Smales, Glen Jacob A1 - Pauw, Brian Richard A1 - Huber, P. A1 - Schönhals, Andreas T1 - Collective orientational order and phase behavior of a discotic liquid crystal under nanoscale confinement N2 - The phase behavior and molecular ordering of hexakishexyloxy triphenylene (HAT6) DLC under cylindrical nanoconfinement is studied utilizing differential scanning calorimetry (DSC) and dielectric spectroscopy (DS), where cylindrical nanoconfinement is established through embedding HAT6 into the nanopores of anodic aluminum oxide membranes (AAO), and a silica membrane with pore diameters ranging from 161 nm down to 12 nm. Both unmodified and modified pore walls were considered, and in the latter case the pore walls of AAO membranes were chemical treated with n octadecylphosphonic acid (ODPA) resulting in the formation of a 2.2 nm thick layer of grafted alkyl chains. Phase transition enthalpies decrease with decreasing pore size, indicating that a large proportion of the HAT6 molecules within the pores has a disordered structure, which increases with decreasing pore size for both pore walls. In the case of the ODPA modification the amount of ordered HAT6 is increased compared to the unmodified case. The pore size dependencies of the phase transition temperatures were approximated using the Gibbs Thomson equation, where the estimated surface tension is dependent on the molecular ordering of HAT6 molecules within the pores and upon their surface. DS was employed to investigate the molecular ordering of HAT6 within the nanopores. These investigations revealed that with a pore size of around 38 nm, for the samples with the unmodified pore walls, the molecular ordering changes from planar axial to homeotropic radial. However, the planar axial configuration, which is suitable for electronic applications, can be successfully preserved through ODPA modification for most of the pore sizes. KW - Discotic Liquid Crystals KW - Nanoconfinement PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-475222 DO - https://doi.org/10.1039/c8na00308d SN - 2516-0230 VL - 1 IS - 3 SP - 1104 EP - 1116 PB - RSC AN - OPUS4-47522 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yildirim, Arda A1 - Krause, Christina A1 - Zorn, R. A1 - Schönhals, Andreas T1 - Multiple glassy dynamics of a homologous series of triphenylene-based columnar liquid crystals – A study by broadband dielectric spectroscopy, advanced calorimetry and Neutron Scattering N2 - Hexakis(n-alkyloxy)triphenylene) (HATn) consisting of an aromatic triphenylene core and alkyl side chains are model discotic liquid crystal (DLC) systems forming a columnar mesophase. In the mesophase, the molecules of HATn self-assemble in columns, which has one-dimensional high charge carrier mobility along the columns. Here, a homologous series of HATn with different length of the alkyl chain (n=5,6,8,10,12) is investigated using differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques including fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). The investigation of the phase behavior was done utilizing DSC experiments and the influence of the alkyl chain length on the phase behavior was revealed. By the dielectric investigations a γ-relaxation due to localized fluctuations as well as two glassy dynamics the αcore and αalkyl relaxation were observed in the temperature range of the plastic crystalline phase. Moreover, the observed glassy dynamics were further studied employing advanced calorimetry. All observed relaxation processes are attributed to the possible specific molecular fluctuations and discussed in detail. From the results a transition at around n=8 from a rigid constrained (n=5,6) to a softer system (n=10,12) on a molecular lenght scale was revealed with increasing alkyl chain length. A counterbalance of two competing effects of a polyethylene like behavior of the alkyl chains in the intercolumnar domains and self-organized confinement is discussed in the context of a hindered glass transition. The results were confirmed by in- and quasielastic neutron scattering T2 - Confit 2022 CY - Grenoble, France DA - 10.10.2022 KW - Glassy Dynamics KW - Discotic Liquid Crystals PY - 2022 AN - OPUS4-56661 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yildirim, Arda A1 - Krause, Christina A1 - Zorn, R. A1 - Lohstroh, W. A1 - Schneider, G. J. A1 - Zamponi, M. A1 - Holerer, O. A1 - Frick, B. A1 - Schönhals, Andreas T1 - Complex molecular dynamics of a symmetric model discotic liquid crystal revealed by broadband dielectric, thermal and neutron spectroscopy N2 - The molecular dynamics of the triphenylene-based discotic liquid crystal HAT6 is investigated by broadband dielectric spectroscopy, advanced dynamical calorimetry and neutron scattering. Differential scanning calorimetry in combination with X-ray scattering reveals that HAT6 has a plastic crystalline phase at low temperatures, a hexagonally ordered liquid crystalline phase at higher temperatures and undergoes a clearing transition at even higher temperatures. The dielectric spectra show several relaxation processes: a localized gamma-relaxation a lower temperature and a so called alpha-2-relaxation at higher temperatures. The relaxation rates of the alpha-2-relaxation have a complex temperature dependence and bear similarities to a dynamic glass transition. The relaxation rates estimated by hyper DSC, Fast Scanning calorimetry and AC Chip calorimetry have a different temperature dependence than the dielectric alpha-2-relaxation and follows the VFT-behavior characteristic for glassy dynamics. Therefore, this process is called alpha-1-relaxation. Its relaxation rates show a similarity with that of polyethylene. For this reason, the alpha-1-relaxation is assigned to the dynamic glass transition of the alkyl chains in the intercolumnar space. Moreover, this process is not observed by dielectric spectroscopy which supports its assignment. The alpha-2-relaxation was assigned to small scale translatorial and/or small angle fluctuations of the cores. The neutron scattering data reveal two relaxation processes. The process observed at shorter relaxation times is assigned to the methyl group rotation. The second relaxation process at longer time scales agree in the temperature dependence of its relaxation rates with that of the dielectric gamma-relaxation. KW - Discotic Liquid Crystals PY - 2020 DO - https://doi.org/10.1039/c9sm02487e VL - 16 IS - 8 SP - 2005 EP - 2016 PB - Royal Chemical Society AN - OPUS4-50466 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yildirim, Arda A1 - Krause, Christina A1 - Huber, P. A1 - Schönhals, Andreas T1 - Multiple glassy dynamics of a homologous series of triphenylene-based columnar liquid crystals – A study by broadband dielectric spectroscopy and advanced calorimetry N2 - Hexakis(n-alkyloxy)triphenylene) (HATn) consisting of an aromatic triphenylene core and alkyl side chains are model discotic liquid crystal (DLC) systems forming a columnar mesophase. In the mesophase, the molecules of HATn self-assemble in columns, which has one-dimensional high charge carrier mobility along the columns. Here, a homologous series of HATn with different length of the alkyl chain (n = 5,6,8,10,12) is investigated using differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques including fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). The investigation of the phase behavior was done utilizing DSC experiments and the influence of the alkyl chain length on the phase behavior was revealed. By the dielectric investigations probing the molecular mobility, a c-relaxation due to localized fluctuations as well as two glassy dynamics, the acore- and aalkyl-relaxation, were observed in the temperature range of the plastic crystalline phase. Moreover, the observed glassy dynamics were further studied employing advanced calorimetry. All observed relaxation processes are attributed to the possible specific molecular fluctuations and discussed in detail. From the results a transition at around n = 8 from a rigid constrained (n = 5,6) to a softer system (n = 10,12) was revealed with increasing alkyl chain length. A counterbalance of two competing effects of a polyethylene-like behavior of the alkyl chains in the intercolumnar domains and self-organized confinement is discussed in the context of a hindered glass transition. KW - Discotic liquid crystals KW - Broadband dielectric spectroscopy KW - Advanced calorimetry PY - 2022 DO - https://doi.org/10.1016/j.molliq.2022.119212 VL - 358 SP - 1 EP - 10 PB - Elsevier B.V. AN - OPUS4-54721 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yildirim, Arda A1 - Kolmangadi, Mohamed Aejaz A1 - Bühlmeyer, A. A1 - Huber, P. A1 - Laschat, S. A1 - Schönhals, Andreas T1 - Electrical conductivity and multiple glassy dynamics of crow-ether based columnar liquid crystals N2 - The phase behavior of two unsymmetrical triphenylene crown ether-based columnar liquid crystals (CLCs) bearing different lengths of alkyl chains, KAL465 and KAL468, was investigated using differential scanning calorimetry (DSC). A plastic crystalline (Cry), columnar liquid crystalline (Colh) and an isotropic phase were observed along with two glass transitions in the Cry phase. The molecular mobility of the KAL compounds was further studied by a combination of broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques. By the BDS investigations, three dielectric active relaxation processes were observed for both samples. At low temperatures, a γ-process in the Cry state was detected and is assigned to the localized fluctuations taking place in the alkyl chains. An α2-process takes place at higher temperatures in the Cry phase. An α3 process was found in the Colh mesophase. The advanced calorimetric techniques consist of fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS) employing temperature modulated DSC and FSC (TMDSC and TMFSC). The advanced calorimetric investigations revealed that besides the α2 process in agreement with BDS, a second dynamic glass transition (α1-process) is present which is not observed by dielectric spectroscopy. The results are in good agreement with the glass transitions detected by DSC for this process. The temperature dependences of the relaxation rates of the α1 , α2 and α3 processes are all different. Therefore, different molecular assignments for the relaxation processes are proposed. In addition to the relaxation processes, a conductivity contribution was explored by BDS for both KAL compounds. The conductivity contribution appears in both Cry and Colh phases, where the conductivity increases by ca. one order of magnitude at phase transition from the crystalline to the hexagonal phase. KW - Columnar Liquid Crystal PY - 2020 DO - https://doi.org/10.1021/acs.jpcb.0c06854 VL - 124 IS - 39 SP - 8728 EP - 8739 PB - ACS AN - OPUS4-51374 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yildirim, Arda A1 - Bühlmeyer, A. A1 - Hayash, S A1 - Haenle, J. C. A1 - Sentker, K. A1 - Krause, Christina A1 - Huber, Patrick A1 - Laschat, Sabine A1 - Schönhals, Andreas T1 - Multiple glassy dynamics in dipole functionalized triphenylene-based discotic liquid crystals revealed by broadband dielectric spectroscopy and advanced calorimetry – assessment of the molecular origin N2 - A selected series of dipole functionalized triphenylene-based discotic liquid crystals (DLCs) was synthesized and investigated in a systematic way to reveal the phase behavior and molecular dynamics. The later point is of particular importance to understand the charge transport in such systems which is the key property for their applications such as organic field-effect transistors, solar cells or as nanowires in molecular electronics, and also to tune the properties of DLCs. The mesomorphic properties were studied by polarizing optical microscopy, X-ray diffraction, and differential scanning calorimetry, which were compared to the corresponding unfunctionalized DLC. The molecular dynamics were investigated by a combination of state-of-the-art broadband dielectric spectroscopy (BDS) and advanced calorimetry such as fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). Besides localized fluctuations, surprisingly multiple glassy dynamics were detected for all materials for the first time. Glassy dynamics were proven for both processes unambiguously due to the extraordinary broad frequency range covered. The a1-process is attributed to fluctuations of the alky chains in the intercolumnar space because a polyethylene-like glassy dynamics is observed. This corresponds to a glass transition in a confined three-dimensional space. The a2-process found at temperatures lower than a1-process, is assigned to small scale rotational and/or translational in plane fluctuations of the triphenylene core inside distorted columns. This can be considered as a glass transition in a one-dimensional fluid. Therefore, obtained results are of general importance to understand the glass transition, which is an unsolved problem of condensed matter science. KW - Discotic Liquid Crystals KW - Broadband dielectric spectroscopy KW - Flash DSC KW - Specific heat spectroscopy PY - 2019 DO - https://doi.org/10.1039/c9cp03499d SN - 1463-9076 VL - 21 IS - 33 SP - 18265 EP - 18277 PB - RSC AN - OPUS4-48739 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yildirim, Arda A1 - Szymoniak, Paulina A1 - Sentker, K. A1 - Butschies, M. A1 - Bühlmeyer, A. A1 - Laschat, S. A1 - Huber, P. A1 - Schönhals, Andreas T1 - Molecular Mobility and Ionic Conductivity of Ionic Liquid Crystals Forming a Hexagonal Columnar Mesophase N2 - For the first time, the molecular mobility of two linear-shaped tetramethylated guanidinium triflates ionic liquid crystals (ILCs) having different length of alkyl chains was investigated by a combination of broadband dielectric spectroscopy (BDS) and specific heat spectroscopy (SHS). SHS was carried out by differential AC-chip calorimetry at higher frequencies and temperature modulated DSC at lower frequencies. These ILCs can form a hexagonal ordered columnar mesophase. Two relaxation processes were found by BDS for both samples. At low temperatures, a γ-processes is observed which is assigned to specific localized fluctuations. At higher temperatures, α1-processes take place. α2 processes were also detected by SHS but with a completely different temperature dependence of the relaxation times. Different molecular assignments of α1- and α2-processes are suggested. At even higher temperatures, conductivity was detected by BDS. T2 - Spring Meeting of German Physical Society CY - Berlin, Germany DA - 12.03.2018 KW - Ionic liquid crystals PY - 2018 AN - OPUS4-44504 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yildirim, Arda A1 - Sentker, K. A1 - Huber, P. A1 - Schönhals, Andreas T1 - Collective Orientational Order and Phase Behavior of a Discotic Liquid Crystal under Confinement N2 - Discotic liquid crystals (DLCs) are a promising class of soft matter for electronic applications. This is due to their ability to self-organize into columns in a hexagonal columnar mesophase, driven by the overlapping of the π orbitals of their aromatic cores. This leads to a high charge-carrier mobility along the column axis. Previous studies on DLCs showed that their properties, such as phase transition temperatures and enthalpies, are susceptible to nanoconfinement. In this study, 2,3,6,7,10,11 hexakis[hexyloxy] triphenylene (HAT6) was confined into parallel aligned cylindrical nanopores of anodic aluminum oxide (AAO) membranes by melt infiltration. Furthermore, the pore surfaces of a series of membranes were chemically modified, resulting in a more hydrophobic pore surface than the unmodified ones. Collective orientational order and phase behavior of HAT6 confined into modified and unmodified nanopores of AAO were investigated by broadband dielectric spectroscopy and differential scanning calorimetry respectively. T2 - Spring Meeting of German Physical Society CY - Berlin, Germany DA - 12.03.2018 KW - Discotic Liquid Crystals PY - 2018 AN - OPUS4-44506 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yildirim, Arda T1 - Liquid Crystals Forming a Columnar Mesophase: Structure, Dynamics and Electric Conductivity N2 - The molecular dynamics and ionic conductivity of ionic liquid crystals (ILCs) forming a columnar mesophase, two linear-shaped tetramethylated guanidinium triflates ILCs having different lengths of alkyl chains, were investigated by a combination of Broadband Dielectric Spectroscopy (BDS) and Specific Heat Spectroscopy (SHS). Three processes were detected by BDS; at low temperature γ-process, at higher temperatures α-process and at even higher temperatures conductivity. The γ-process indicates localized fluctuations, and the α-process designates cooperative fluctuations. Slightly different restrictions were found for conductivity processes of LC536 and LC537 due to the slightly different lengths of alky chains. The conductivity mechanisms in the plastic crystalline and the columnar mesophase have been revealed by BDS and different charge carriers were assigned for the different phases. Furthermore, the cooperative dynamics were also probed by SHS. The cooperative dynamics probed by the different techniques (BDS and SHS) compared, and assigned to the different restrictions on the cooperativity due to the difference in the sensitivity of the techniques. T2 - Seminar Vortrag Technische Universität Berlin CY - Berlin, Germany DA - 28.06.2018 KW - Columnar Liquid Crystals KW - Ionic Liquid Crystals PY - 2018 AN - OPUS4-45383 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yildirim, Arda A1 - Sentker, Kathrin A1 - Huber, Patrick A1 - Schönhals, Andreas T1 - Collective Orientational Order and Phase Behavior of a Discotic Liquid Crystal under Confinement N2 - Discotic liquid crystals (DLCs) are a promising class of soft matter for electronic applications. This is due to their ability to self-organize into columns in a hexagonal columnar mesophase, driven by the overlapping of the π orbitals of their aromatic cores. This leads to a high charge-carrier mobility along the column axis. Embedding liquid crystals into nanopores of anodic aluminum oxide (AAO) results in a 2D nanoconfinement of these materials. This confinement affects their properties, compared to the bulk, such as phase transition temperatures and enthalpies, molecular mobility, and crystallization. In this study, 2,3,6,7,10,11 hexakis[hexyloxy] triphenylene (HAT6) was confined into parallel aligned cylindrical nanopores of AAO membranes by melt infiltration. The membrane as confining hosts used have varying pore diameters, from 10 nm to 160 nm, covering a broad pore size range, thus, a better understanding of the confinement effect on phase behavior and molecular configuration in the pores. Furthermore, it is aimed to obtain axial ordering or to increase degree of axial ordering by chemically modifying the surfaces of the pores. Therefore, the pore surfaces the membranes were chemically modified, resulting in a more hydrophobic pore surface than the unmodified ones. The phase behavior was explored by a power-compensated DSC allowing the detecting of small changes in the phase behavior. In the literature, dielectric spectroscopy was demonstrated as a method to monitor molecular order inside the pores. Here, we also investigate the collective orientational order, corresponding to dominating molecular ordering, by dielectric spectroscopy. T2 - 10th Conference on Broadband Dielectric Spectroscopy and its Applications CY - Brussles, Belgium DA - 26.08.2018 KW - Confined Columnar Liquid Crystals PY - 2018 AN - OPUS4-45916 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yildirim, Arda A1 - Sentker, Kathrin A1 - Bühlmeyer, Andrea A1 - Laschat, Sabine A1 - Huber, Patrick A1 - Schönhals, Andreas T1 - Molecular dynamics of dipole functionalized triphenylene-based discotics N2 - Since discovery of discotic liquid crystals (DLCs), consisting of a disklike rigid aromatic core and flexible alkyl chains attached to the core, dating back to Chandrasekhar’s work in 1977, they have been extensively investigated to reveal their fundamental properties and potential for applications. The researches on DLCs in last decades showed that DLCs can be considered as promising materials for organic electronic applications since they exhibit one dimensional high charge mobility along the column axis in a columnar mesophase. The mobilies of the rigid aromatic core and the flexible alkyl chains can influence their application properites, e.g. the charge carrier mobility, therefore, it needs to be explored in detailed. In this study, a series of dipole functionalized triphenylene-based discotics, forming a columnar mesophase, were investigated to reveal the influence of the functionalization on phase behavior, molecular dynamics and as well as conductivity. The molecular mobility of the discotics was probed by broadband dielectric spectroscopy (BDS). In addition to conductivity and localized dynamics, glassy dynamics were also observed. The phase behavior of the material was explored by a power-compansated differential scanning calorimetry (DSC). Beside the phase transition temperatures and enthalpies, thermal glass transitions were found for all the materials. Moreover, the glassy dynamics were further investigated by Flash DSC, which is a chip-based calorimetry technique allows fast heating and cooling rates as high as 10000K/s. T2 - 10th Conference on Broadband Dielectric Spectroscopy and its Applications CY - Brussles, Belgium DA - 26.08.2018 KW - Columnar liquid crystals PY - 2018 AN - OPUS4-45918 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yildirim, Arda A1 - Szymoniak, Paulina A1 - Sentker, Kathrin A1 - Huber, Patrick A1 - Schönhals, Andreas T1 - Molecular Mobility and Ionic Conductivity of Ionic Liquid Crystals Forming a Hexagonal Columnar Mesophase N2 - For the first time, the molecular mobility of two linear-shaped tetramethylated guanidinium triflates ionic liquid crystals (ILCs) having different length of alkyl chains was investigated by a combination of broadband dielectric spectroscopy (BDS) and specific heat spectroscopy (SHS). By self-assembly, these ILCs can form a hexagonal ordered mesophase besides plastic crystalline phases and the isotropic state. SHS was carried out by differential AC-chip calorimetry at higher frequencies and temperature modulated DSC at lower frequencies. Two relaxation processes were found by BDS for both samples. At low temperatures, a γ-processes is observed which is assigned to specific localized fluctuations. At higher temperatures, α1-processes take place. α2 processes were also detected by SHS but with a completely different temperature dependence of the relaxation times. Different molecular assignments of α1- and α2-processes are suggested. At even higher temperatures, conductivity was detected by BDS. An increase in the DC conductivity by four orders of magnitude at the phase transition from the plastic crystalline to the hexagonal columnar mesophase is found. This result is traced to a change in the charge transport mechanism from a delocalized electron hopping in the stacked aromatic systems (in the plastic phase) to one dominated by an ionic conduction in the quasi-1D ion channels formed along the supermolecular columns in the ILC hexagonal mesophases. T2 - 10th Conference on Broadband Dielectric Spectroscopy and its Applications CY - Brussles, Belgium DA - 26.08.2018 KW - Ionic Liquid Crystals PY - 2018 AN - OPUS4-45914 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yildirim, Arda A1 - Bühlmeyer, A. A1 - Hayashi, S. A1 - Haenle, J. C. A1 - Sentker, K. A1 - Huber, P. A1 - Laschat, S. A1 - Schönhals, Andreas T1 - Molecular Dynamics of Dipole Functionalized Triphenylene-based Discotics N2 - In this study, the molecular dynamics of a series of dipole functionalized triphenylene-based discotics, forming a columnar mesophase, were investigated by broadband dielectric spectroscopy (BDS). In addition to conductivity and localized dynamics, glassy dynamics were also observed. At higher temperatures an α1-processes and at low temperatures an α2 processes were detected having a completely different temperature dependence of its relaxation times. Different molecular assignments of α1- and α2-processes are suggested. The phase behavior of the material was explored under helium purge down to 100 K by differential scanning calorimetry (DSC). Besides the phase transition temperatures and enthalpies, one or two thermal glass transitions were found for all the materials. Moreover, the glassy dynamics were further investigated by Flash DSC, which is a chip-based calorimetry technique allowing for fast heating and cooling rates as high as 10000K/s. T2 - Spring Meeting of German Physical Society CY - Regensburg, Germany DA - 01.04.2019 KW - Liquid Crystals PY - 2019 AN - OPUS4-47827 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yesilcicek, Yasemin A1 - Haas, S. A1 - Suárez Ocano, Patricia A1 - Zaiser, E. A1 - Hesse, René A1 - Többens, D. M. A1 - Glatzel, U. A1 - Manzoni, Anna Maria T1 - Controlling Lattice Misfit and Creep Rate Through the γ' Cube Shapes in the Al10Co25Cr8Fe15Ni36Ti6 Compositionally Complex Alloy with Hf and W Additions N2 - Trace elements play an important role in the fine-tuning of complex material properties. This study focuses on the correlation of microstructure, lattice misfit and creep properties. The compositionally complex alloy Al10Co25Cr8Fe15Ni36Ti6 (in at. %) was tuned with high melting trace elements Hf and W. The microstructure consists of a γ matrix, γ' precipitates and the Heusler phase and it is accompanied by good mechanical properties for high temperature applications. The addition of 0.5 at.% Hf to the Al10Co25Cr8Fe15Ni36Ti6 alloy resulted in more sharp-edged cubic γ′ precipitates and an increase in the Heusler phase amount. The addition of 1 at.% W led to more rounded γ′ precipitates and the dissolution of the Heusler phase. The shapes of the γ' precipitates of the alloys Al9.25Co25Cr8Fe15Ni36Ti6Hf0.25W0.5 and Al9.25Co25Cr8Fe15Ni36Ti6Hf0.5W0.25, that are the alloys of interest in this paper, create a transition from the well-rounded precipitates in the alloy with 1% W containing alloy to the sharp angular particles in the alloy with 0.5% Hf. While the lattice misfit has a direct correlation to the γ' precipitates shape, the creep rate is also related to the amount of the Heusler phase. The lattice misfit increases with decreasing corner radius of the γ' precipitates. So does the creep rate, but it also increases with the amount of Heusler phase. The microstructures were investigated by SEM and TEM, the lattice misfit was calculated from the lattice parameters obtained by synchrotron radiation measurements. KW - High entropy alloy KW - Lattice misfit KW - Creep KW - Transmission electron microscopy KW - X-ray diffraction PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-565655 DO - https://doi.org/10.1007/s44210-022-00009-1 SP - 1 EP - 9 PB - Springer AN - OPUS4-56565 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yesilcicek, Yasemin A1 - Wetzel, Annica A1 - Witt, Julia A1 - Stephan-Scherb, C. A1 - Ozcan, Ozlem T1 - Investigation on gradient Fe-Ni-Cr-Mn alloy using diffusion multiples N2 - The high-throughput synthesis and characterization of potential material combinations plays an important role in accelerating the development of new materials. Diffusion controlled synthesis of gradient alloys is widely used to create phase diagrams, and it is also one of the most effective combinatorial approaches for rapid realization of potential material combinations. This study focuses on the synthesis and investigation of the quaternary multi-principle-element alloy (MPEA) FeNiCrMn by means of diffusion multiples, the correlation of their microstructural and chemical characterization data with their application relevant properties like local mechanical and corrosion properties. A diffusion system was set up by combining an equimolar ternary alloy (FeNiCr) with a single diffusing metallic component (Mn) with the highest interdiffusion coefficient. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to collect microstructural and compositional information which were correlated to local mechanical properties studied with nanoindentation. Local corrosion properties were investigated by means of Atomic Force Microscopy (AFM) and Scanning Electrochemical Microscopy (SECM). We have observed that a >50 μm deep homogeneous diffusion zone was formed the thickness of which scales with the duration of the thermal treatment. Beyond the Mn-concentration gradient in the FeNiCr matrix, a distinct Cr-rich secondary phase, characterized by high hardness and elastic modulus values appeared. We synthesized MPEAs with selected compositions from the diffusion zone as well as the Cr-rich phase as bulk alloys for electrochemical corrosion studies under different environmental conditions. The presentation will summarize the results of our correlative study on the mechanical properties and corrosion resistance of the quaternary multi-principle-element alloy (MPEA) FeNiCrMn family. T2 - MRS Spring 2023 CY - San Francisco, California, USA DA - 10.04.2023 KW - Chemically Complex Materials KW - CCMat KW - Diffusion multiples PY - 2023 AN - OPUS4-59404 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yesilcicek, Yasemin A1 - Wetzel, Annica A1 - Witt, Julia A1 - Dimper, Matthias A1 - Ozcan, Ozlem T1 - Corrosion and mechanical properties of multi principal element alloys designed by using diffusion couples N2 - The efficient exploration of novel alloy chemistries is crucial for advancing the development of new materials. Diffusion-controlled synthesis of gradient alloys is an intelligent approach for creating phase diagrams and to effectively identify potential material combinations with tailored properties. This project focusses on the design of quaternary multi-principle-element alloys (MPEAs) using diffusion couples. Our diffusion system contains an equimolar ternary alloy (FeNiCr) and additional single diffusing elements e.g. Mn and Mo. We determined the optimal temperature ranges for the diffusion thermal treatment by means of ThermoCalc simulations with the aim to form single-phase MPEAs. Microstructure and chemical characterization of the diffusion couples were performed by means of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). For most alloy couples, the diffusion zone contained a single-phase alloy matrix with diffusion-induced compositional gradient as well as precipitation phases. This heterogeneity makes the diffusion couples interesting materials to investigate local mechanical and corrosion properties. Thus, local corrosion properties were examined using Atomic Force Microscopy (AFM) and Scanning Electrochemical Microscopy (SECM). Nanoindentation was used for the analysis of local mechanical properties. Based on the results of the local corrosion analysis, we have selected single-phase alloy chemistries along the diffusion zone and reproducibly synthesized these alloys in bulk for detailed corrosion studies by means of potentiodynamic polarization and SECM. The presentation will briefly summarize our methodology and motivation for using diffusion couples as an efficient tool for exploring phase diagrams of MPEAs in the search for new alloy chemistries and the results of our correlative study on the mechanical and corrosion properties of these materials. T2 - 244th ECS Meeting CY - Gothenburg, Sweden DA - 08.10.2023 KW - Chemically Complex Materials KW - CCMat KW - Corrosion PY - 2023 AN - OPUS4-59407 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Yesilcicek, Yasemin A1 - Wetzel, Annica A1 - Witt, Julia A1 - Dimper, Matthias A1 - Ozcan, Ozlem T1 - Correlation of corrosion and mechanical properties of Fe-Ni-Cr-Mn alloy synthesized by diffusion multiples N2 - The efficient exploration of novel alloy compositions is crucial for advancing the development of new materials. One widely utilized approach for creating phase diagrams is the use of diffusion-controlled synthesis for gradient alloys. This method is also an effective means for rapidly identifying potential material combinations. The present study focusses on the exploration of quaternary multi-principle-element alloys (MPEAs) using diffusion multiples. We established a diffusion system by combining an equimolar ternary alloy (FeNiCr) with single diffusing elements Mn and Mo. Using ThermoCalc simulations, we determined suitable temperature ranges where we can expect the formation of single-phase alloys. Depending on the diffusion constants of the selected metals, diffusion times were adjusted to obtain diffusion zones with a depth of greater than 50 μm. Microstructural and compositional information was gathered via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) and correlated to local mechanical properties evaluated by means of nanoindentation. Local corrosion properties were examined using Atomic Force Microscopy (AFM) and Scanning Electrochemical Microscopy (SECM). Our results indicate that the ThermoCalc simulations have a good predictive power for crystallographic phases. However, especially with the Mn-FeNiCr system, formation of Cr-rich secondary phases were observed, which led to Cr-depletion and thus to localized corrosion processes in the matrix at the vicinity of the secondary phases. Based on the results of the local electrochemical tests, we have selected single-phase compositions along the diffusion zone and synthesized these alloys in bulk for corrosion studies by means of potentiodynamic polarization and SECM. The presentation will summarize our methodology using diffusion couples as an efficient tool for exploring compositional spaces of MPEAs in the search for novel single-phase alloys and the results of our correlative study on the mechanical and corrosion properties of these materials. T2 - EUROCORR2023 CY - Brussels, Belgium DA - 27.08.2023 KW - Chemically Complex Materials KW - CCMat KW - Corrosion PY - 2023 AN - OPUS4-59408 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Xue, Boyang A1 - You, Yi A1 - Riedel, Jens T1 - High-throughput underwater elemental analysis by μJ-laser-induced breakdown spectroscopy at a kHz repetition rate: part II, understanding the high repetition-rate from a fundamental perspective N2 - The technological advances in lasers enabled the wide application of laser-induced breakdown spectroscopy (LIBS) as a powerful analytical means for elemental analyses. Rather than commonly used lasers that operate at several to several-tens of Hz, the high repetition rate ones that operate at tens of kHz showed superior analytical advantages while implying unique excitation pathways. Specifically, the production of excited atomic hydrogen and oxygen, which can serve as internal standards, is quite different from that in commonly reported double-pulse LIBS. In this part of the work, it was found that the atomic emitters stemming from water are not related to cavitation bubbles. Moreover, the emitter productions of dissolved species, e.g., Na+, and water-related species, e.g., H-α, are two distinctive mechanisms. Towards analytical applications of the high repetition-rate system, the fundamental investigation can provide important guidelines to address real-life challenges. In this part of the work, the high repetition-rate regime of operation is explored from a more kinetic perspective. KW - High repetition rate KW - Laser-induced breakdown spectroscopy PY - 2020 DO - https://doi.org/10.1039/D0JA00291G VL - 35 IS - 12 SP - 2912 EP - 2919 PB - Royal Society of Chemistry AN - OPUS4-51565 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Xue, Boyang A1 - You, Yi A1 - Gornushkin, Igor B. A1 - Zheng, R. A1 - Riedel, Jens T1 - High-throughput underwater elemental analysis by μJ-laser-induced breakdown spectroscopy at kHz repetition rates: part I, ultrasound-enhanced optical emission spectroscopy towards application perspectives N2 - In recent years, laser-induced breakdown spectroscopy (LIBS) has gained significant attention as a means for simple elemental analyses. The suitability of LIBS for contactless analysis allows it to be a perfect candidate for underwater applications. While the majority of LIBS systems still rely upon sub-kHz pulsed lasers, this contribution introduces 10s-kHz low pulse-energy lasers into underwater LIBS to improve the throughput and statistical validity. Interestingly, the spectral component significantly changed above a critical laser repetition-rate threshold. Spectral lines of atomic hydrogen and oxygen stemming from water become visible beyond a ∼10 kHz repetition rate. This observation suggests a different plasma dynamic compared to low repetition rates. When the pulse-to-pulse interval becomes sufficiently short, a cumulative effect begins to be significant. Apparently, the new phenomena occur on a timescale corresponding to a threshold rate of ∼10 kHz, i.e. ∼100 μs. Analytically, the high repetition rates result in improved statistical validity and throughput. More plasma events per unit time allowed the use of low efficiency Echelle spectrometers without compromising on the analytical performance. Meanwhile, the presence of H I and O I out of the water (as the matrix) also offers internal standardization in underwater elemental analysis. Since the laser fluence was on the lower edge of the plasma threshold, an additional ultrasound source was introduced to induce external perturbation, which significantly improved the plasma formation stability. A huge advantage of LIBS is the possibility of detecting almost all elements within a sample simultaneously. Throughout the periodic table, chlorine is one of the most challenging elements. Consequently, Ca2+ and Na+ were used as samples to demonstrate the capability of this high repetition-rate LIBS platform. As an ambitious benchmark for our system, chlorine detection in water was also discussed. KW - High repetition rate KW - Laser-induced breakdown spectroscopy PY - 2020 DO - https://doi.org/10.1039/D0JA00290A VL - 35 IS - 12 SP - 2901 EP - 2911 PB - The Royal Society of Chemistry AN - OPUS4-51564 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Xue, Boyang A1 - Riedel, Jens A1 - Gornushkin, Igor B. A1 - Zheng, R. A1 - You, Yi T1 - High-throughput underwater elemental analysis through optical emission spectroscopy with ultrasound-assisted μJ-laser-induced breakdown at kHz repetition rate N2 - The elemental analysis of seawater is often critical to the understanding of marine chemistry, marine geochemistry, and the deep-sea ecosystems. Laser-induced breakdown spectroscopy (LIBS) with the advantage of rapid multi-elements detection, has a great potential for in-situ elemental analysis of seawater. In practice, it is crucial to create a compact, low cost and power saving instrument for the long-term deep-sea observation. A recently appeared diode-pumped solid-state (DPSS) laser seems to be a promising candidate as it is both compact and robust. Additionally, its high repetition rate up to hundreds of kHz can provide a considerable throughput for LIBS analysis. However, the DPSS lasers operate at moderate pulse energies, usually less than one mJ, which cannot sustain stable breakdowns in bulk water. To ensure stable laser-induced plasmas underwater with such a μJ-DPSS laser, we introduced an ultrasound source to assist the breakdown process. The phase interface and mass flow generated by the near-field ultrasound can greatly reduce the breakdown threshold and enhance element-specific emissions. Meanwhile, the high repetition-rate pulses can also improve the breakdown probability and generate unique emission lines originated from the water molecule. We further demonstrate that the high repetition-rate DPSS laser combined with the Echelle spectrometer can provide effective quantitative analysis for metal elements in bulk water. T2 - 10th Euro-Mediterranean Symposium on Laser-Induced Breakdown Spectroscopy, EMSLIBS 2019 CY - Czech, Brno DA - 08.09.2019 KW - Ultrasound KW - Underwater LIBS KW - µJ-DPSS laser KW - High repetition-rate PY - 2019 AN - OPUS4-49223 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wurzler, Nina A1 - Sobol, Oded A1 - Altmann, Korinna A1 - Radnik, Jörg A1 - Özcan Sandikcioglu, Özlem T1 - Preconditioning of AISI 304 stainless steel surfaces in the presence of flavins—Part I: Effect on surface chemistry and corrosion behavior N2 - Stainless steel AISI 304 surfaces were studied after a mild anodic polarization for oxide growth in the presence and absence of two derivatives of vitamin B2 (riboflavin and flavin mononucleotide) that can be secreted by metal‐reducing bacteria and act as a chelating agent for iron species. The alterations in oxide chemistry were studied by means of surface‐sensitive techniques such as X‐ray photoelectron spectroscopy and time‐of‐flight secondary ion mass spectrometry analysis. The complementary electrochemical characterization revealed a preferential growth of an oxide/hydroxide iron‐rich film that is responsible for an altered pit initiation and nucleation behavior. These findings suggest that as the corrosion behavior is determined by the interplay of the chemical and electronic properties, only a mild anodic polarization in the presence of redox‐active molecules is able to alter the chemical and electronic structure of the passive film formed on stainless steel AISI 304. This helps to achieve a profound understanding of the mechanisms of microbially influenced corrosion (MIC) and especially the possible effects of the redox‐active biomolecules, as they may play an important role in the corrosion susceptibility of stainless steel surfaces. KW - Corrosion KW - Stainless steel KW - Surface analysis PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-528117 DO - https://doi.org/10.1002/maco.202012191 VL - 72 IS - 6 SP - 974 EP - 982 PB - Wiley AN - OPUS4-52811 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wurzler, Nina A1 - Schütter, Jan David A1 - Wagner, R. A1 - Dimper, Matthias A1 - Hodoroaba, Vasile-Dan A1 - Lützenkirchen-Hecht, D. A1 - Özcan Sandikcioglu, Özlem T1 - Preconditioning of AISI 304 stainless steel surfaces in the presence of flavins—Part II: Effect on biofilm formation and microbially influenced corrosion processes N2 - Biofilm formation and microbially influenced corrosion of the iron-reducing microorganism Shewanella putrefaciens were investigated on stainless steel surfaces preconditioned in the absence and presence of flavin molecules by means of XANES (X-ray absorption near-edge structure) analysis and electrochemical methods. The results indicate that biofilm formation was promoted on samples preconditioned in electrolytes containing minute amounts of flavins. On the basis of the XANES results, the corrosion processes are controlled by the iron-rich outer layer of the passive film. Biofilm formation resulted in a cathodic shift of the open circuit potential and a protective effect in terms of pitting corrosion. The samples preconditioned in the absence of flavins have shown delayed pitting and the samples preconditioned in the presence of flavins did not show any pitting in a window of −0.3- to +0.0-V overpotential in the bacterial medium. The results indicate that changes in the passive film chemistry induced by the presence of minute amounts of flavins during a mild anodic polarization can change the susceptibility of stainless steel surfaces to microbially influenced corrosion. KW - Biofilms KW - XANES KW - Microbially influenced corrosion (MIC) PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-528130 DO - https://doi.org/10.1002/maco.202012192 VL - 72 IS - 6 SP - 983 EP - 994 PB - Wiley AN - OPUS4-52813 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wurzler, Nina A1 - Schütter, J. D. A1 - Wagner, R. A1 - Dimper, M. A1 - Lützenkirchen-Hecht, D. A1 - Özcan Sandikcioglu, Özlem T1 - Trained to corrode: Cultivation in the presence of Fe(III) increases the electrochemical activity of iron reducing bacteria – An in situ electrochemical XANES study N2 - This paper reports results from in situ electrochemical X-ray absorption near-edge spectroscopy (XANES) studies of the corrosion processes on model thin iron films in the presence of iron reducing bacteria Shewanella putrefaciens. Here we investigate the electrochemical activity of two cultures grown in the presence and absence of Fe(III) citrate in the culture medium. The XANES spectra and the OCP data of the Fe sample incubated with the culture grown in absence of Fe(III) did not show any significant changes during twenty hours of monitoring. In the case of the culture grown in Fe(III) containing medium, an accelerated dissolution of the iron film was observed together with the formation of a mixed Fe(II)-Fe(III) hydroxide surface layer. The open circuit potential (OCP) steadily approached the free corrosion potential of iron in neutral chloride containing electrolytes, indicating a continuous dissolution process without passivation. KW - Microbiologically influenced corrosion KW - XANES KW - Electrochemistry KW - Iron reducing bacteria PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-505732 DO - https://doi.org/10.1016/j.elecom.2020.106673 VL - 112 SP - 106673 PB - Elsevier B.V. AN - OPUS4-50573 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wurzler, Nina A1 - Schutter, Jan David A1 - Wagner, R. A1 - Dimper, Matthias A1 - Lützenkirchen-Hecht, D. A1 - Özcan Sandikcioglu, Özlem T1 - Abundance of Fe(III) during cultivation affects the microbiologically influenced corrosion (MIC) behaviour of iron reducing bacteria Shewanella putrefaciens N2 - The effect of the presence of Fe(III) during the cultivation on the electrochemical activity and corrosion behaviour of dissimilatory iron reducing bacteria Shewanella putrefaciens was studied by means of ex situ and in situ X-ray absorption near-edge spectroscopy (XANES). Stainless steel AISI 304 and thin iron films were studied as substrates. XANES analysis indicated an accelerated iron dissolution and growth of an oxide/hydroxide film for the culture grown with Fe(III) in comparison to the culture grown in absence of Fe(III). Electrochemical Analysis indicated that the biofilm resulted in acceleration of the general corrosion but provides protection against local corrosion. KW - Stainless Steel KW - XANES KW - Iron KW - Cyclic Voltammetry KW - Microbiological Corrosion PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-513788 DO - https://doi.org/10.1016/j.corsci.2020.108855 VL - 174 SP - 108855 PB - Elsevier Ltd. AN - OPUS4-51378 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wurzler, Nina A1 - Hidde, Gundula A1 - Schenderlein, Matthias A1 - Özcan Sandikcioglu, Özlem T1 - Effect of organic conditioning layers adsorbed on stainless steel AISI 304 on the attachment and biofilm formation of electroactive bacteria Shewanella putrefaciens CN32 N2 - The initial attachment and subsequent biofilm formation of electroactive bac-teriaShewanella putrefaciensCN32 was investigated to clarify the influence oforganic conditioning layers. A selection of macromolecules and self-assembledmonolayers (SAMs) of different chain lengths and functional groups were pre-pared and characterized by means of infrared spectroscopy in terms of theirchemistry. Surface energy and Zeta (ζ-) potential of the conditioning layers wasdetermined with contact angle and streaming current measurements. Amongthe studied surface parameters, a high polar component and a high ratio ofpolar-to-disperse components of the surface energy has emerged as a successfulindicator for the inhibition of the initial settlement ofS. putrefacienson stainlesssteel AISI 304 surfaces. Considering the negative surface charge of planktonicS. putrefacienscells, and the strong inhibition of cell attachment by positivelycharged polyethylenimine (PEI) conditioning layers, our results indicate thatelectrostatic interactions do play a subordinate role in controlling the attach-ment of this microorganism on stainless steel AISI 304 surfaces. For the biofilmformation, the organization of the SAMs affected the local distribution of thebiofilms. The formation of three-dimensional and patchy biofilm networks waspromoted with increasing disorder of the SAMs. KW - Bacterial attachment KW - Conditioning films KW - Self-assembled monolayers KW - Stainless steel PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-559887 DO - https://doi.org/10.1002/eng2.12458 VL - 4 IS - 1 SP - 1 EP - 12 PB - Wiley online library AN - OPUS4-55988 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wurzler, Nina A1 - Wagner, Ralph A1 - Schutter, Jan David A1 - Das, Chayanika A1 - Dimper, Matthias A1 - An, Biwen A1 - Koerdt, Andrea A1 - Lützenkirchen-Hecht, Dirk A1 - Özcan Sandikcioglu, Özlem T1 - Effect of cultivation conditions on the electrochemical activity of metal reducing bacteria (mrb) on stainless steel surfaces N2 - Investigation of the electrochemical activity of two cultures grown with and without abundance of Fe(III) and their different ability to reduce and therefore dissolve iron oxides in steel and model iron thin films. T2 - Eurocorr2019 CY - Sevilla, Spain DA - 09.09.2019 KW - X-ray spectroscopic techniques KW - Microbiologically influenced corrosion KW - MIC KW - XANES KW - Metal reducing bacteria KW - In situ PY - 2019 AN - OPUS4-49692 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wurzler, Nina A1 - Kleinbub, Sherin A1 - Koerdt, Andrea A1 - Özcan Sandikcioglu, Özlem T1 - Effect of conditioning layers on the attachment and biofilm formation of electroactive bacteria on stainless steel N2 - The characteristics of different molecules chosen as representatives for specific functionalities in conditioning layers play an important role on attachment behavior and later biofilm formation of bacteria. The chemical composition is a major component influencing the attachment but there is a conglomerate of influences. T2 - Eurocorr2018 CY - Krakow, Poland DA - 09.09.2018 KW - Conditioning layer KW - Stainless steel KW - Bacterial attachment PY - 2018 AN - OPUS4-46487 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Woydt, Mathias A1 - Wäsche, Rolf A1 - Brandt, Guido A1 - Ehrke, Roman T1 - Tribology in hot steam - for waste heat recovery or for energy harvesting - N2 - The wear rates of self-amted alumina couples show that friction as well as wear is largely determined by the above mentioned hydro-thermal conditions. The presence of water and ist amount available in the surrounding system either in liquid or in gaseous from plays a key role for friction and wear behavior and cabe benefical for the tribological profile of steam degradation resistant materials. Hot steam enhances the tribo-chemical formations of oxides and hydroxides on MgO-ZrO2, alumina and antimony impregnated carbon. T2 - 21th International Colloquium Tribology CY - Stuttgart/Ostfildern, Germany DA - 09.01.2018 KW - Friction KW - Alumina KW - Hot steam PY - 2018 AN - OPUS4-43895 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wolff, M. A1 - Wonneberger, R. A1 - Freiberg, K.E. A1 - Hertwig, Andreas A1 - Bonse, Jörn A1 - Giebeler, L. A1 - Koitzsch, A. A1 - Kunz, C. A1 - Weber, H. A1 - Hufenbach, J.K. A1 - Müller, F.A. A1 - Gräf, S. T1 - Formation of laser-induced periodic surface structures on Zr-based bulk metallic glasses with different chemical composition N2 - Bulk metallic glasses (BMG) are amorphous metal alloys known for their unique physical and mechanical properties. In the present study, the formation of femtosecond (fs) laser-induced periodic surface structures (LIPSS) on the Zr-based BMGs Zr46Cu46Al8, Zr61Cu25Al12Ti2, Zr52.5Cu17.9Al10Ni14.6Ti5 (Vit105) and Zr57Cu15.4Al10Ni12.6Nb5 (Vit106) was investigated as a function of their different chemical composition. For this purpose, LIPSS were generated on the sample surfaces in an air environment by fs-laser irradiation (λ = 1025 nm, τ = 300 fs, frep = 100 kHz). The surface topography was characterized by scanning electron microscopy and atomic force microscopy. Moreover, the impact of LIPSS formation on the structure and chemical surface composition was analyzed before and after fs-laser irradiation by X-ray diffraction and X-ray photoelectron spectroscopy as well as by transmission electron microscopy in combination with energy dispersive X-ray spectroscopy. Despite the different chemical composition of the investigated BMGs, the fs-laser irradiation resulted in almost similar properties of the generated LIPSS patterns. In the case of Zr61Cu25Al12Ti2, Vit105 and Vit106, the surface analysis revealed the preservation of the amorphous state of the materials during fs-laser irradiation. The study demonstrated the presence of a native oxide layer on all pristine BMGs. In addition, fs-laser irradiation results in the formation of laser-induced oxide layers of larger thickness consisting of an amorphous ZrAlCu-oxide. The precise laser-structuring of BMG surfaces on the nanoscale provides a versatile alternative to thermoplastic forming of BMG surfaces and is of particular interest for the engineering of functional material surfaces. KW - Bulk metallic glasses KW - Femtosecond laser KW - Laser-induced periodic surface structures (LIPSS) KW - Chemical analysis KW - Oxidation PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-581799 DO - https://doi.org/10.1016/j.surfin.2023.103305 SN - 2468-0230 VL - 42 SP - 1 EP - 11 PB - Elsevier B.V. AN - OPUS4-58179 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Wolf, Jako A1 - Stawski, Tomasz A1 - Smales, Glen Jacob A1 - Thünemann, Andreas A1 - Emmerling, Franziska T1 - SI Files for "Towards automation of the polyol process for the synthesis of silver nanoparticles" N2 - The graphml file: reaction_graph_AgNP.graphml is included. It contains topological information (Fig. 1 in the main text) about the reaction setup and metadata with reaction condtions. It used by the Python API used to control the Chemputer. SAXS reports. The complete report sheets generated by McSAS are included. They contain extended information characterising the size distributions and the fitting parameters. NP3_I: saxs_report_NP3_I.pdf NP3_II: saxs_report_NP3_II.pdf NP3_III: saxs_report_NP3_III.pdf NP3_IV: saxs_report_NP3_IV.pdf NP5_I: saxs_report_NP5_I.pdf NP5_II: saxs_report_NP5_II.pdf NP5_III: saxs_report_NP5_III.pdf KW - Automated synthesis KW - Silver KW - Nanoparticles PY - 2022 DO - https://doi.org/10.5281/zenodo.5910614 PB - Zenodo CY - Geneva AN - OPUS4-55197 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wolf, J. A1 - Stawski, Tomasz A1 - Smales, Glen Jacob A1 - Thünemann, Andreas A1 - Emmerling, Franziska T1 - Towards automation of the polyol process for the synthesis of silver nanoparticles N2 - Metal nanoparticles have a substantial impact across diferent felds of science, such as photochemistry, energy conversion, and medicine. Among the commonly used nanoparticles, silver nanoparticles are of special interest due to their antibacterial properties and applications in sensing and catalysis. However, many of the methods used to synthesize silver nanoparticles often do not result in well-defned products, the main obstacles being high polydispersity or a lack of particle size tunability. We describe an automated approach to on-demand synthesis of adjustable particles with mean radii of 3 and 5 nm using the polyol route. The polyol process is a promising route for silver nanoparticles e.g., to be used as reference materials. We characterised the as-synthesized nanoparticles using small-angle X-ray scattering, dynamic light scattering and further methods, showing that automated synthesis can yield colloids with reproducible and tuneable properties. KW - Sillver KW - Nanoparticles KW - Automated synthesis KW - Chemputer KW - Scattering KW - SAXS PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-546803 DO - https://doi.org/10.1038/s41598-022-09774-w VL - 12 IS - 1 SP - 1 EP - 9 PB - Nature Springer AN - OPUS4-54680 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witte, Steffen A1 - Radtke, Martin A1 - de Oliveira Guilherme Buzanich, Ana A1 - Grunewald, Christian A1 - Reinholz, Uwe A1 - Riesemeier, Heinrich A1 - Emmerling, Franziska T1 - XAFS@BAMline N2 - X-ray Absorption fine structure spectroscopy (XAFS) is a frequently employed technique in order to investigate structural composition and Change of chemical compounds such as catalytic species or corrosion processes. These structural properties are essential (i) to understand underlying reaction mechanism and (ii) to further improve the design of materials. While XAFS measurements are usually performed with ionization Chambers or simple fluorescence detectors, we at BAMline specialize in measurements with innovative set-ups that meet Specialrequirements such as time resolution, (3D-) spatial Resolution or demanding sample environments. This contribution presents various available XAFS configurations with their corresponding applications. In particular, these comprise single -shot XAFS for time- resolved measurements, grazing-exit XAFS with energy and a spatially resolved detector for the characterization of thin films and an in situ grazing incidence Setup for the characterization of corrosion layers. Additionally,the possibility of analyzing Minute samples in total-reflection geometry is demonstrated. T2 - EXRS 2018 CY - Ljubljana, Slovenia DA - 24.06.2018 KW - XANES KW - XAFS KW - BAMline KW - Synchrotron KW - TXRF PY - 2018 AN - OPUS4-46361 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witte, Steffen A1 - Kulow, Anicó A1 - Seeberg, D. A1 - de Oliveira Guilherme Buzanich, Ana A1 - Radtke, Martin A1 - Reinholz, Uwe A1 - Grunewald, Christian A1 - Riesemeier, Heinrich A1 - Wohlrab, S. T1 - S2XAFS@work: Customization for the Characterization of VOx based Catalysts N2 - X-ray absorption fine structure spectroscopy (XAFS) is a frequently employed technique in order to investigate structural composition and change of chemical compounds such as catalytic species. These structural properties are essential (i) to understand underlying reaction mechanism and (ii) to further improve the design of efficient catalysts. This investigation is based on a newly developed XAFS setup comprising both time- and lateral-resolved XAFS information simultaneously in a single-shot (S2XAFS). The primary broadband beam is generated by a filter/X-ray-mirror combination (bandpass). The transmitted beam through the sample is diffracted by a convexly bent Si (111) crystal, producing a divergent beam. This, in turn, is collected by an area sensitive detector with a theta to 2 theta geometry. This facile, stable and scanningless setup was tested at the BAMline @ BESSY-II (Berlin, Germany). This contribution focuses on further experimental optimizations allowing the characterization of supported vanadium oxide (VOx) based catalysts at the lower hard X-ray regime (5 to 6 keV). First S2XAFS measurements of these catalysts are presented herein. Supported VOx catalysts show promising results in the oxidation of methane to formaldehyde. S2XAFS allows determining the structural composition of the metal (i.e. vanadium) based on a fast and smart setup. It is therefore an ideal tool to identify crucial roles of chemical compounds in catalytic reactions. T2 - XAFS 2018 CY - Cracow, Poland DA - 22.07.2018 KW - XANES KW - XAFS KW - BAMline KW - Synchrotron PY - 2018 AN - OPUS4-46362 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witte, Steffen A1 - de Oliveira Guilherme Buzanich, Ana A1 - Fittschen, U.E.A. A1 - Radtke, Martin A1 - Reinholz, Uwe A1 - Wobrauschek, P. A1 - Streli, C. T1 - TXRF-XANES: a unique experimental setup for chemical speciation of traces down to pg range N2 - Description of the set-up and first results for TXRF-XANES at BAMline T2 - XAFS 2018 CY - Cracow, Poland DA - 22.07.2018 KW - TXRF KW - XANES KW - Synchrotron KW - BAMline PY - 2018 AN - OPUS4-46363 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witt, Julia T1 - In situ Atomic Force Microscopy (AFM) studies of corrosion processes on thin film coated AA2024-T3 aluminium alloy surfaces N2 - The performance of functional coatings relies strongly on the stability of the polymer-metal interface. The increasing utilization of multi-material structures in the automotive and aerospace industry necessitates a fundamental understanding of the processes leading to interface degradation for the development of novel strategies to increase corrosion and delamination resistance. The aim of this project is to investigate the corrosion processes at the buried interface of thin film coated aluminium alloy AA2024-T3 under corrosive and coupled corrosive-mechanical load. A spin coating procedure was developed to synthesize epoxy-like coatings and their nanofiller loaded composites with controlled thickness by layer-by-layer deposition of poly[(o-cresyl glycidyl ether)-co-formaldehyde] and poly-(ethylenimine) bi-layers. Our results indicate that the incorporation of graphene into the epoxy-based coatings leads to the improvement of mechanical and barrier properties. Furthermore, the functional groups play important roles in the interfacial bonding between polymer matrix and the nanofillers. Atomic force microscopy (AFM) results indicate very homogeneous and dense films with a thickness of ~25 nm per bi-layer and the successful integration of the nanofillers into the composite coatings. Ellipsometry measurements of film thickness verified a proportional film growth with the number of deposited layers. The degradation and delamination behavior of the coating systems was characterized by means of in situ AFM corrosion experiments. Complementary energy dispersive X-ray spectroscopy (EDX) analysis was used to correlate the corrosion and delamination behavior with the different intermetallic particle chemistries and distributions. The presentation will summarize our results on the effect of coating composition and build-up on the local corrosion processes on thin film covered AA2024-T3 aluminium alloys. T2 - Eurocorr 2021 CY - Online meeting DA - 20.09.2021 KW - In situ AFM KW - Corrosion KW - Thin epoxy-based films PY - 2021 AN - OPUS4-54053 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witt, Julia A1 - Almalla, Ahed A1 - Özcan Sandikcioglu, Özlem T1 - In situ AFM studies of deformation and corrosion processes on AA2024-T3 aluminium alloy N2 - The performance of functional coatings and adhesively joined hybrid components relies strongly on the stability of the polymer-metal interface. With the increasing utilization of multi-material structures in the automotive and aerospace industry, it is of great scientific and technical interest to understand the processes leading to interface degradation and to develop novel strategies to increase corrosion and delamination resistance. The aim of this project is to develop thin epoxy-based films on aluminium alloy AA2024-T3 as a model system and to investigate their interfacial stability under corrosive and coupled corrosive-mechanical load. Electrochemical and spectroscopic methods were used for the characterisation of the film properties and in situ corrosion experiments were performed by means of AFM. The deformation properties of the aluminium alloy and the model coatings were investigated by means of scanning Kelvin probe force microscopy (SKPFM) utilizing the integrated tensile stage. The presentation will give a brief overview of the capabilities of the new AFM setup to foster future collaborations and summarize our work on the interface stability of model coatings. T2 - Abteilungskolloquium FB6 CY - Berlin, Germany DA - 27.11.2018 KW - Corrosion KW - In situ Atomic Force Microscopy (AFM) KW - Aluminium alloy KW - Scanning Kelvin Probe Force Microscopy (SKPFM) PY - 2018 AN - OPUS4-48027 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witt, Julia A1 - Almalla, Ahed A1 - Özcan Sandikcioglu, Özlem T1 - AFM-Untersuchungen von funktionellen Beschichtungen und Strukturänderungen unter mechanischer Beanspruchung N2 - Die Rasterkraftmikroskopie (AFM) hat sich in den letzten Jahren als eine vielseitige Abbildungstechnik von Oberflächen mit einer sehr hohen Ortsauflösung etabliert. Über die Untersuchung der reinen Oberflächentopographie sind erweiterte Modi in der Lage, gleichzeitig Informationen über die elektrischen und magnetischen Eigenschaften sowie Adhäsionsprozesse auf Oberflächen zu liefern. Interessanter wird es, wenn das AFM mit geeigneten Messzellen für in-situ-Untersuchungen in kontrollierten Atmosphären oder in Elektrolyten unter elektrochemischer Kontrolle ausgestattet ist. Dies ermöglicht die Untersuchung von Korrosions- und Adhäsionsprozessen unter Bedingungen, die die Betriebsumgebung repräsentieren. Ein aktueller Forschungsschwerpunkt unseres Fachbereiches liegt in den Untersuchungen der Deformationseigenschaften von Funktionsschichten auf Leichtmetalllegierungen, sowie in situ Untersuchungen des Korrosionsverhaltens unter kombinierter korrosiver und mechanischer Beanspruchung mittels AFM. Durch die Integrierung eines Zug-Druckmoduls in den Probentisch des Rasterkraftmikroskops haben wir jetzt die Möglichkeit, verschiedene Materialien uniaxialen Umformversuchen mit bis zu 5 kN Kraft zu unterziehen. Dabei können unter anderem auch zyklische Belastungen genutzt werden, um Ermüdungsprozesse zu simulieren. Da die Messungen in situ ohne die De- und Remontage der Probe durchgeführt werden, ermöglicht der Aufbau nicht nur Messungen mit präziser Positionssteuerung, sondern auch die Untersuchung von Prozessen im elastischen Bereich, die für die Aufklärung der Mechanismen, die zu Ermüdungsversagen führen, entscheidend sind. Die Posterpräsentation wird detaillierte Informationen zum neuen AFM-Setup liefern und unsere aktuellen Ergebnisse zur Verformung dünner Schutzschichten auf AA2024-T3 zusammenfassen. T2 - Hybrid, Materials and Structures CY - Bremen, Germany DA - 18.04.2018 KW - Kelvinsondenkraftmikroskopie KW - Funktionelle Beschichtungen KW - Kombinierete korrosive und mechanische Beanspruchung KW - Lokale Korrosion KW - Delamination KW - Deformation PY - 2018 AN - OPUS4-46522 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witt, Julia A1 - Almalla, Ahed A1 - Stepien, Daniel A1 - Özcan Sandikcioglu, Özlem T1 - Multilayer thin coatings for corrosion protection of AA2024-T3 aluminium alloy N2 - The performance of adhesively joined hybrid components relies strongly on the stability of the adhesive-material interface. With the increasing utilization of multi-material structures in the automotive and aerospace industry, it is of great scientific and technical interest to understand the processes leading to adhesive failure and to develop novel strategies to increase corrosion and delamination resistance of adhesive joints. The aim of this study is to develop thin epoxy based films and their carbon nanofiller loaded composites on aluminium alloy AA2024-T3 and to investigate their interfacial stability under corrosive and coupled corrosive-mechanical load. Spin coating was used for the layer-by-layer deposition of poly[(o-cresyl glycidyl ether)-co-formaldehyde] and poly-(ethylenimine) bi-layers. Carbon nanofillers are introduced either by mixing into the coating components or in between individual layers. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis was performed to investigate the porosity and water uptake of the model films, respectively. Atomic force microscopy (AFM) results indicated a very homogeneous and dense film with low surface roughness. The bi-layer thickness ranged between 30 to 40 nm. Electrochemical measurements show a higher corrosion resistance with the increase of the bi-layer number. The main novelty of this contribution is the in-situ AFM investigations under coupled corrosive-mechanical load. For this purpose, a tensile module capable of uniaxial stretching and compression with up to 5 kN force was integrated into the AFM stage. Stretching experiments were performed to investigate the mechanical properties and adhesion of the films, as well as structural changes of the film morphology during uniaxial deformation. The contribution will provide detailed information on the new AFM setup and summarize our results on the stability of model epoxy and nanocomposite films on AA2024-T3. T2 - EURADH 2018 CY - Lisbon, Portugal DA - 05.09.2018 KW - Electrochemical Empedance Spectroscopy (EIS) KW - Scanning Kelvin Probe Force Microscopy (SKPFM) KW - Corrosion KW - Delamination KW - Aluminium KW - Epoxide PY - 2018 AN - OPUS4-46513 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Witt, Julia T1 - Exploring innovative Materials and in situ techniques N2 - Presentation of some projects conducted in recent years related to corrosion studies and research on electrocatalysis. The talk was part of a seminar at the University of Toronto and took place within the framework of a scientific exchange stay. T2 - Seminar at the University of Toronto CY - Toronto, Canada DA - 11.10.2023 KW - Multi-principal element alloys (MPEAs) KW - Electrocatalysis KW - Corrosion KW - Materials acceleration platforms (MAPs) PY - 2023 AN - OPUS4-59029 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wintzheimer, S. A1 - Szczerba, Wojciech A1 - de Oliveira Guilherme Buzanich, Ana A1 - Kashiwaya, S. A1 - Klein, A. A1 - Jaegermann, W. A1 - Toupance, T. A1 - Shmeliov, A. A1 - Nicolosi, V. A1 - Heuzé, K. A1 - Mandel, K. A1 - Dembski, S. T1 - Discovering the determining parameters for the photocatalytic activity of TiO2 colloids based on an anomalous dependence on the specific surface area N2 - The photocatalytic (PC) performance of titanium dioxide (TiO2) nanoparticles strongly depends on their specific surface, the presence of crystal defects, their crystal phase, and the exposed crystal facets. In order to understand which of these factors contributes most significantly to the PC activity of TiO2 colloids, all of them have to be individually analyzed. This study entails the synthesis of five anatase nanocrystal samples. By maintaining the same reactant ratios as well as hydrothermal sol–gel synthesis route and only varying the autoclaving time or temperature, different crystallite sizes are obtained under comparable experimental conditions. A decrease in PC performance with increase in specific surface area is found. Such an unexpected counterintuitive result establishes the basis for a better understanding of the crucial factors that ultimately determine the PC activity. These are investigated by studying nanocrystals bulk and surface structure and morphology using a selection of complementary analysis methods (X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), X-ray diffraction (XRD)…). It is found that a change in the nanocrystal morphology from an equilibrium state truncated tetragonal bipyramid to a more elongated rod-like structure accompanied by an increase in oxygen vacancies is responsible for an augmented PC activity of the TiO2 nanocrystals. KW - Ti-based colloids KW - Photocatalysis KW - Spectroscopy KW - XAFS PY - 2018 DO - https://doi.org/10.1002/ppsc.201800216 SN - 0934-0866 SN - 1521-4117 VL - 35 IS - 9 SP - 1800216, 1 EP - 10 PB - Wiley Online Library AN - OPUS4-46068 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wilke, Marco A1 - Röder, Bettina A1 - Paul, Martin A1 - Weller, Michael G. T1 - Sintered glass monoliths as supports for affinity columns N2 - A novel stationary phase for affinity separations is presented. This material is based on sintered borosilicate glass readily available as semi-finished filter plates with defined porosity and surface area. The material shows fast binding kinetics and excellent long-term stability under real application conditions due to lacking macropores and high mechanical rigidity. The glass surface can be easily modified with standard organosilane chemistry to immobilize selective binders or other molecules used for biointeraction. In this paper, the manufacturing of the columns and their respective column holders by 3D printing is shown in detail. The model system protein A/IgG was chosen as an example to examine the properties of such monolithic columns under realistic application conditions. Several specifications, such as (dynamic) IgG capacity, pressure stability, long-term performance, productivity, non-specific binding, and peak shape, are presented. It could be shown that due to the very high separation speed, 250 mg antibody per hour and column can be collected, which surpasses the productivity of most standard columns of the same size. The total IgG capacity of the shown columns is around 4 mg (5.5 mg/mL), which is sufficient for most tasks in research laboratories. The cycle time of an IgG separation can be less than 1 min. Due to the glass material’s excellent pressure resistance, these columns are compatible with standard HPLC systems. This is usually not the case with standard affinity columns, limited to manual use or application in low-pressure systems. The use of a standard HPLC system also improves the ability for automation, which enables the purification of hundreds of cell supernatants in one day. The sharp peak shape of the elution leads to an enrichment effect, which might increase the concentration of IgG by a factor of 3. The final concentration of IgG can be around 7.5 mg/mL without the need for an additional nano-filtration step. The purity of the IgG was > 95% in one step and nearly 99% with a second polishing run. KW - Affinity Chromatography KW - Affinity Extraction KW - Affinity Separation KW - Protein Purification KW - Down Stream Processing KW - Antibody Purification KW - Diagnostic Antibodies KW - Therapeutic Antibodies KW - Automated Purification KW - HPLC KW - FPLC KW - IgG determination KW - Concentration step KW - Monoclonal Antibodies KW - Polyclonal Antibodies KW - Human Plasma KW - Glass Support KW - Borosilicate Glass KW - Monolith KW - Sintered Material KW - Additive Manufacturing KW - Column holder KW - Construction KW - Open Science KW - Citizen Science KW - Protein A KW - Regeneration KW - High-Speed Separations KW - Robustness PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-527581 DO - https://doi.org/10.3390/separations8050056 SN - 2297-8739 VL - 8 IS - 5 SP - 1 EP - 16 PB - MDPI CY - Basel AN - OPUS4-52758 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - INPR A1 - Wilke, Marco A1 - Röder, Bettina A1 - Paul, Martin A1 - Weller, Michael G. T1 - Sintered Glass Monoliths as New Supports for Affinity Columns N2 - A novel stationary phase for affinity separations is presented. This material is based on sintered borosilicate glass readily available as semi-finished filter plates with defined porosity and surface area. The material shows fast binding kinetics and excellent long-term stability under real application conditions due to lacking macropores and high mechanical rigidity. The glass surface can be easily modified with standard organosilane chemistry to immobilize selective binders or other molecules used for biointeraction. In this paper, the manufacturing of the columns and their respective column holders by 3D printing is shown in detail. The model system protein A/IgG was chosen as an example to examine the properties of such monolithic columns under realistic application conditions. Several specifications, such as (dynamic) IgG capacity, pressure stability, long-term performance, productivity, non-specific binding, and peak shape, are presented. It could be shown that due to the very high separation speed, 250 mg antibody per hour and column can be collected, which surpasses the productivity of most standard columns of the same size. The total IgG capacity of the shown columns is around 4 mg (5.5 mg/mL), which is sufficient for most tasks in research laboratories. The cycle time of an IgG separation can be less than 1 minute. Due to the glass material's excellent pressure resistance, these columns are compatible with standard HPLC systems. This is usually not the case with standard affinity columns, limited to manual use or application in low-pressure systems. The use of a standard HPLC system also improves the ability for automation, which enables the purification of hundreds of cell supernatants in one day. The sharp peak shape of the elution leads to an enrichment effect, which might increase the concentration of IgG by a factor of 3. The final concentration of IgG can be around 7.5 mg/mL without the need for an additional nanofiltration step. The purity of the IgG was > 95% in one step and nearly 99% with a second polishing run. KW - Affinity Chromatography KW - Glass KW - Purification KW - Antibodies KW - Solid support KW - HPLC KW - FPLC KW - Separation PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-529117 DO - https://doi.org/10.20944/preprints202103.0298.v1 SN - 2310-287X SP - 1 PB - MDPI CY - Basel AN - OPUS4-52911 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wilke, Manuel A1 - Akhemtova, Irina A1 - Rademann, K. A1 - Emmerling, Franziska T1 - Mechanochemical synthesis of cerium(IV)-phosphonates N2 - The syntheses and crystal structures of two cerium(IV) phosphonates are presented. Cerium(IV) bis(phenylphosphonate) Ce(O3PC6H5)2 1 can be formed from precipitation and mechanochemical reaction, whereas cerium(IV) bis(carboxymethylphosphonate) monohydrate Ce(O3PCH2COOH)2 H2O 2 is only accessible via ball milling. All reactions proceed very fast and are completed within a short time span. In situ measurements for the syntheses of 1 show that the product occurs within seconds or a few minutes, respectively. The structures were solved from powder X-ray diffraction data. KW - In situ studies KW - Mechanochemistry KW - XRD PY - 2018 DO - https://doi.org/10.1007/s10853-018-2507-x SN - 0022-2461 SN - 1573-4803 VL - 53 IS - 19 SP - 13733 EP - 13741 PB - Springer Science + Business Media B.V. AN - OPUS4-45672 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wiesner, Yosri A1 - Hoffmann, Thomas A1 - Range, David A1 - Altmann, Korinna T1 - Microplastics in sediments of the river Rhine—A workflow for preparation and analysis of sediment samples from aquatic river systems for monitoring purposes N2 - AbstractMicroplastics (MP) can be detected in all environmental systems. Marine and terrestrial aquatic systems, especially the transported suspended solids, have often been the focus of scientific investigations in the past. Sediments of aquatic river systems, on the other hand, were often ignored due to the time‐consuming sample preparation and analysis procedures. Spectroscopic measurement methods counting particle numbers are hardly suitable as detection methods, because there are plenty of natural particles next to a small number of MP particles. Integral methods, such as thermoanalytical methods are determining the particle mass independently of the inorganic components.In this study, a workflow for sample preparation via density separation and subsequent analysis by thermal extraction desorption‐gas chromatography/mass spectrometry is presented, which leads to representative and homogeneous samples and allows fast and robust MP mass content measurements suitable for routine analysis. Polymers were identified and quantified in all samples. Polyethylene and styrene‐butadiene rubber are the dominant polymers, besides polypropylene and polystyrene. Overall, total polymer masses between 1.18 and 337.0 µg/g could be determined. Highest MP concentrations in riverbed sediment are found in sites characterized by low flow velocities in harbors and reservoirs, while MP concentrations in sandy/gravelly bed sediments with higher flow velocities are small. KW - Microplastics KW - Density separation KW - TED-GC/MS KW - NaI PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-597335 DO - https://doi.org/10.1002/appl.202200125 SP - 1 EP - 10 PB - Wiley VHC-Verlag AN - OPUS4-59733 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wiesner, Yosri A1 - Bednarz, Marius A1 - Braun, Ulrike A1 - Bannick, Claus Gerhard A1 - Ricking, Mathias A1 - Altmann, Korinna T1 - A promising approach to monitor microplastic masses in composts N2 - Inputs of plastic impurities into the environment via the application of fertilizers are regulated in Germany and the EU by means of ordinances. Robust and fast analytical methods are the basis of legal regulations. Currently, only macro- and large microplastic contents (>1 mm) are measured. Microplastics (1–1,000 µm), are not yet monitored. Thermal analytical methods are suitable for this purpose, which can determine the mass content and can also be operated fully automatically in routine mode. Thermal extraction desorption-gas chromatography/mass spectrometry (TED-GC/MS) allows the identification of polymers and the determination of mass contents in solid samples from natural environments. In accordance with the German or European Commission (EC) Fertiliser Ordinance, composting plants should be monitored for microplastic particles with this method in the future. In this context a compost plant was sampled. At the end of the rotting process, the compost was sieved and separated in a coarse (>1 mm) and a fine fraction (<1 mm). The fine fraction was processed using density separation comparing NaCl and NaI as possible salt alternative and screened for microplastic masses by TED-GC/MS with additional validation and quality assurance experiments. With TED-GC/MS total microplastics mass contents of 1.1–3.0 μg/mg in finished compost could be detected with polyethylene mainly. What differs much to the total mass of plastics in the coarse fraction with up to 60 μg/mg, which were visually searched, identified via ATR-FTIR and gravimetrically weighted. KW - Microplastics KW - TED-GC/MS KW - Compost KW - Monitoring KW - Soil PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-586688 DO - https://doi.org/10.3389/fenvc.2023.1281558 SN - 2673-4486 VL - 4 SP - 1 EP - 12 PB - Frontiers Media CY - Lausanne AN - OPUS4-58668 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -