TY - JOUR A1 - Beck, Uwe A1 - Hertwig, Andreas A1 - Kormunda, M. A1 - Krause, Andreas A1 - Krüger, Hannes A1 - Lohse, Volkmar A1 - Nooke, Alida A1 - Pavlik, J. A1 - Steinbach, J. T1 - SPR enhanced ellipsometric gas monitoring on thin iron doped tin oxide layers N2 - In this work, thin iron doped tin oxide layers (3–6 nm) were investigated with regard to gas sensitivity by means of surface plasmon resonance (SPR) effect with ellipsometric readout. The experimental set-up was a Kretschmann configuration with gold as metal layer. The sensor system was exposed to different concentrations of methane in the low ppm range and the sensor response of an uncoated gold layer compared to a gold layer coated with iron doped tin oxide. The additional layer effects stability with regard to drift behavior of the sensor and an increase in sensitivity. Furthermore, the sensor is able to detect the toxic gas carbon monoxide in low concentration range (down to 0.5 ppm). The thin layers were investigated by X-ray photoelectron spectroscopy, secondary electron microscopy and spectroscopic ellipsometry. The possible mechanisms taking place on the surface are discussed. KW - Gas sensing KW - SPR effect KW - Iron doped tin oxide KW - Ellipsometry PY - 2011 DO - https://doi.org/10.1016/j.snb.2011.08.036 SN - 0925-4005 SN - 1873-3077 VL - 160 IS - 1 SP - 609 EP - 615 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-24826 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nooke, Alida A1 - Beck, Uwe A1 - Hertwig, Andreas A1 - Krause, Andreas A1 - Krüger, Hannes A1 - Lohse, Volkmar A1 - Negendank, Detlef A1 - Steinbach, J. T1 - On the application of gold based SPR sensors for the detection of hazardous gases N2 - A gas sensor system based on the surface plasmon resonance (SPR) effect in a 44 nm Au layer was studied. The usability of this sensor system was investigated for several analyte gases and gas mixtures which are interesting due to their flammability, toxicity or greenhouse effect. The SPR effect of gold was measured in nitrogen and compared with the gaseous alkane series which caused a shift of the position of the SPR effect. For in situ measurements, the phase shift Δ at the SPR angle (ψ minimum) in the analyte gas mixtures was measured for investigated gases in comparison with nitrogen. With this method, detection limits of different gases could be determined, which lie in a range interesting for safety engineering. Furthermore the aging effect of the gold layers which leads to loss in sensitivity of the sensor was investigated. KW - Ellipsometry KW - SPR effect KW - Gas sensing KW - Gold layer PY - 2010 DO - https://doi.org/10.1016/j.snb.2010.05.061 SN - 0925-4005 SN - 1873-3077 VL - 149 IS - 1 SP - 194 EP - 198 PB - Elsevier CY - Amsterdam [u.a.] AN - OPUS4-21673 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krause, Christina A1 - Yin, Huajie A1 - Cerclier, C. A1 - Morineau, D. A1 - Wurm, Andreas A1 - Schick, C. A1 - Emmerling, Franziska A1 - Schönhals, Andreas T1 - Molecular dynamics of a discotic liquid crystal investigated by a combination of dielectric relaxation and specific heat spectroscopy N2 - The molecular dynamics of the discotic liquid crystal pyrene-1,3,6,8-tetracarboxylic tetra(2-ethylhexyl)ester is studied by dielectric relaxation and specific heat spectroscopy. Dielectric spectroscopy shows 3 processes: a β-relaxation at low temperatures and an α-relaxation in the temperature range of the mesophases followed by conductivity. The dielectric α-relaxation is assigned to a restricted glassy dynamics in the plastic crystal as well as in the liquid crystalline phase. The obtained different Vogel–Fulcher–Tammann laws (different Vogel temperatures and fragility) are related to the different restrictions of the dipolar fluctuations in the corresponding phases. By means of specific heat spectroscopy glassy dynamics is also detected in the plastic crystalline phase but with quite a different temperature dependence of the relaxation times. This is discussed considering the different probes involved and how they are influenced by the structure. In the frame of the fluctuation approach a correlation length of glassy dynamics is calculated to 0.78 nm which corresponds to the core–core distance estimated by X-ray scattering. PY - 2012 DO - https://doi.org/10.1039/c2sm25610j SN - 1744-683X VL - 8 IS - 43 SP - 11115 EP - 11122 PB - RSC Publ. CY - Cambridge AN - OPUS4-26826 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nooke, Alida A1 - Beck, Uwe A1 - Hertwig, Andreas A1 - Krause, Andreas A1 - Krüger, Hannes A1 - Lohse, Volkmar A1 - Negendank, Detlef A1 - Steinbach, J. T1 - Ellipsometric detection of gases with the surface plasmon resonance effect on gold top-coated with sensitive layers N2 - An ellipsometric gas sensor based on the surface Plasmon resonance (SPR) effect of ~ 43 nm thick gold layers was investigated. To protect the gold layer from contamination and to improve the detection limits, the gold layers were top-coated with 5–6 nm thick layers of organic a-C:H or with inorganic metal oxides TiO2 or ZrO2. The additional layers increased the long-term stability, whereas the metal oxide layers protect better than a-C:H. Furthermore, the additional layers decreased the detection limits by one order of magnitude in case of a-C:H and two orders of magnitude in case of the oxides. It could be shown that the detection limits also depend on the kind of preparation (sol–gel process or physical vapour deposition) of the additional layers. KW - Gas sensor KW - SPR KW - Ellipsometry KW - Sensitive layer KW - TiO2 KW - ZrO2 KW - a-C:H PY - 2011 DO - https://doi.org/10.1016/j.tsf.2010.11.091 SN - 0040-6090 VL - 519 IS - 9 SP - 2659 EP - 2663 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-23353 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Hasenstab, Andreas A1 - Krause, Martin A1 - Rieck, C. A1 - Hillemeier, B. T1 - Use of Low Frequency Ultrasound Echo Technique to Determine Cavities in Wooden Construction Composites T2 - 6th International Symposium Non-Destructive Testing in Civil Engineering (NDT-CE) CY - Berlin, Germany DA - 2003-09-16 PY - 2003 UR - http://www.ndt.net/article/ndtce03/papers/p051/p051.htm SN - 3-931381-49-8 SP - 1(?) EP - 9(?) PB - DGZfP CY - Berlin AN - OPUS4-3230 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Hasenstab, Andreas A1 - Krause, Martin ED - Cziesielski, E. T1 - Ultraschallechoverfahren an Holz PY - 2004 SN - 3-433-01705-0 SP - 52 EP - 58 PB - Ernst CY - Berlin AN - OPUS4-3145 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Hasenstab, Andreas A1 - Rieck, C. A1 - Hillemeier, B. A1 - Krause, Martin T1 - Hohlstellenortung in Holzbalken mit dem Ultraschallverfahren N2 - Zusammenfassung Die Anwendung des Ultraschallecho-Verfahrens zur Hohlstellenortung in Holzbalken wird beschrieben. An Hand der Versuchsergebnisse wird der Einfluss der Anisotropie des Holzes auf die Messkopfanordnung und Schallgeschwindigkeit dargestellt. Mit der optimierten Messanordnung ist die erfolgreiche Detektierung von Nachbildungen von Minderdicken und Kernfäule möglich. Besonders klar sind Schäden in Faserrichtung (Kernfäulenachbildung) nachzuweisen. Die sehr guten Ergebnisse zeigen die Anwendbarkeit des Ultraschallecho-Verfahrens an Holz. T2 - Jahrestagung Zerstörungsfreie Materialprüfung 2002 CY - Weimar, Deutschland DA - 2002-05-06 KW - ZfP an Holzbauteilen KW - Fehlstellen KW - Minderdicken KW - Ultraschallecho-Experimente an Probekörpern PY - 2002 UR - http://www.ndt.net/article/dgzfp02/papers/p32/p32.htm SN - 3-931381-39-0 N1 - Serientitel: Berichtsband / Deutsche Gesellschaft für zerstörungsfreie Prüfung e. V. – Series title: Berichtsband / Deutsche Gesellschaft für zerstörungsfreie Prüfung e. V. IS - 80-CD PB - DGZfP CY - Berlin AN - OPUS4-1937 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Scheid, Marc A1 - Geißler, Andreas A1 - Krause, Ulrich T1 - Zum Einfluss der Turbulenz auf die Druckentlastung von Gas- und Staubexplosionen N2 - Der maßgebliche Einfluss turbulenter Strömungsbewegungen auf den Ablauf von Explosionen ist bereits seit längerem bekannt. Wegen der Schwierigkeit, Betrag und Richtung der turbulenten Schwankungsgeschwindigkeit in-situ zu messen, existieren jedoch nur wenige diesbezügliche experimentelle Daten. Es wurde deshalb eine aus drei Glassegmenten bestehende Versuchsapparatur mit etwa 100 l Volumen und einem Länge/Durchmesser-Verhältnis von 4,7 errichtet, die die gleichzeitige Messung der Strömungsgeschwindigkeit und deren turbulenter Fluktuation, der Ausbreitungsgeschwindigkeit der Flamme, der zeitlichen Entwicklung des Explosionsdruckes sowie im Falle von Staubexplosionen der Staubkonzentration erlaubte. Die Glassegmente wurden durch Metallflansche verbunden, an welche insgesamt sechzehn gleichmäßig über Umfang und Höhe verteilte Ventilatoren zur kontrollierten Erzeugung eines Turbulenzfeldes montiert waren. Die Explosionsversuche wurden mit einem Propan-Stickstoff-Sauerstoff-Gemisch sowie mit einem Maisstärke-Luft-Gemisch durchgeführt. Die Zündung der explosionsfähigen Gemische erfolgte durch einen Hochspannungsfunken. Als Berstfolien wurden zwei Polyethylenfolien (Dicke 10 und 15 µm) und drei Aluminiumfolien (Dicke 15, 20 und 22 µm) verwendet. Die Versuche zeigten sowohl bei Gas- als auch bei Staubexplosionen eine Zunahme des reduzierten Explosionsdruckes für wachsende turbulente Schwankungs-geschwindigkeiten im Bereich von 0 m/s bis 0,45 m/s. Diese Zunahme war besonders ausgeprägt für verhältnismäßig kleine Entlastungsflächen (Durchmesser < 70 mm) bei geringen Ansprechdrücken (Polyethylenfolie), während für höhere Ansprechdrücke (Aluminiumfolie) der Einfluss der Turbulenz zurückging. Zur Ergänzung der Experimente wurden Simulationsrechnungen mit dem Computational Fluid Dynamics-Programm Fluent6 unternommen. Diese Rechnungen dienten der Validierung der den Programmen zugrunde liegenden Modelle im Hinblick auf ihre Anwendbarkeit zur Berechnung von Explosionsabläufen in technischen Anlagen. Es konnte eine realistische Wiedergabe der Druck-Zeit-Verläufe durch die Rechnungen erreicht werden. T2 - 7. Fachtagung Arbeits-, Anlagen- und Umweltsicherheit CY - Köthen, Deutschland DA - 2004-11-04 PY - 2004 SP - 15 Seiten (A 04) PB - VDI-Verl. CY - Halle AN - OPUS4-5069 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Scheid, Marc A1 - Geißler, Andreas A1 - Krause, Ulrich T1 - Experiments on the Influence of Turbulence on Vented Gas and Dust Explosions T2 - 5th International Symposium on Hazards, Prevention and Mitigation of Industrial Explosions (ISHPMIE) CY - Cracow, Poland DA - 2004-10-10 KW - Gas explosion KW - Dust explosion KW - Turbulence KW - Venting PY - 2004 SP - 176 EP - 187 PB - Central Mining Institute CY - Kattowitz AN - OPUS4-5074 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Hasenstab, Andreas A1 - Hillemeier, B. A1 - Krause, Martin ED - Bröker, F. T1 - Defect localisation in wood with low frequency ultrasonic echo technique T2 - 14th International Symposium on Nondestructive Testing of Wood CY - Eberswalde, Germany DA - 2005-05-02 PY - 2005 SN - 3-8322-3949-9 SP - 331 EP - 336 PB - Shaker CY - Aachen AN - OPUS4-11307 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Hasenstab, Andreas A1 - Krause, Martin A1 - Lutz, J. A1 - Hillemeier, B. A1 - Rieck, C. T1 - Niederfrequente Ultraschall-Echo-Verfahren und Bohrwiderstandsmessung zur Untersuchung von Holzbauteilen T2 - DGZfP Jahrestagung CY - Rostock, Deutschland DA - 2005-05-02 KW - ZfP an Holzbauteilen KW - Fehlstellen KW - Minderdicken KW - Ultraschallecho-Experimente an Probekörpern KW - Ultraschall-Echo KW - Fäulnis KW - Bauwesen PY - 2005 SN - 3-931381-64-1 N1 - Serientitel: Berichtsband / Deutsche Gesellschaft für zerstörungsfreie Prüfung e. V. – Series title: Berichtsband / Deutsche Gesellschaft für zerstörungsfreie Prüfung e. V. IS - 94-CD SP - 1(?) EP - 11(?) PB - DGZfP CY - Berlin AN - OPUS4-11960 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Hasenstab, Andreas A1 - Krause, Martin A1 - Hillger, w. A1 - Bühling, L. A1 - Ilse, D. A1 - Hillemeier, B. A1 - Rieck, C. T1 - Luftultraschall und Ultraschall-Echo-Technik an Holz T2 - DGZfP Jahrestagung CY - Rostock, Deutschland DA - 2005-05-02 KW - ZfP an Holzbauteilen KW - Fehlstellen KW - Minderdicken KW - Ultraschallecho-Experimente an Probekörpern KW - Ultraschall-Echo KW - Fäulnis KW - Bauwesen KW - Luftultraschall PY - 2005 SN - 3-931381-64-1 N1 - Serientitel: Berichtsband / Deutsche Gesellschaft für zerstörungsfreie Prüfung e. V. – Series title: Berichtsband / Deutsche Gesellschaft für zerstörungsfreie Prüfung e. V. IS - 94-CD SP - 1(?) EP - 15(?) PB - DGZfP CY - Berlin AN - OPUS4-11961 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Moritz, W. A1 - Krause, S. A1 - Roth, U. A1 - Klimm, D. A1 - Lippitz, Andreas T1 - Re-activation of an all solid state oxygen sensor N2 - The silicon based semiconductor structure Si/SiO2/Si3N4/LaF3/Pt can be used as a potentiometric oxygen sensor working at room temperature. A thermal re-activation can be applied to overcome the earlier disadvantage of an increase in response time with continuous use. Using the Pt gate electrode as a resistive heater, very short electrical high-power pulses can be applied. A heating time as short as 300 ns was sufficient for the re-activation of the sensor. This way, only the sensitive thin layer system LaF3/Pt was heated, and the whole sensor was at room temperature immediately after heating. Impedance spectroscopy, X-ray photoelectron spectroscopy (XPS) and quadruple mass spectrometric (QMS)–thermogravimetry (TG) were used to investigate the mechanism of deterioration in dynamic sensor behaviour and re-activation. The formation of hydrated carbonate and the desorption of CO2 and H2O have been shown to be the causes. KW - Chemical sensor KW - Thermal treatment KW - Activation KW - LaF3 KW - Pt PY - 2001 DO - https://doi.org/10.1016/S0003-2670(01)00993-X SN - 0003-2670 SN - 1873-4324 SN - 0378-4304 VL - 437 SP - 183 EP - 190 PB - Elsevier CY - Amsterdam AN - OPUS4-6836 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hasenstab, Andreas A1 - Krause, Martin A1 - Scheer, C. T1 - Zerstörungsfreie Integritätsprüfung von Holz mit dem Ultraschallecho-Verfahren T2 - Forschungskolloquium "Holzbau Forschung + Praxis" CY - Stuttgart, Deutschland DA - 2006-02-23 PY - 2006 SP - 33 EP - 40 PB - Technische Universität Stuttgart CY - Stuttgart AN - OPUS4-12242 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Scheid, Marc A1 - Geißler, Andreas A1 - Krause, Ulrich T1 - Experiments on the influence of pre-ignition turbulence on vented gas and dust explosions N2 - Experiments were performed on the influence of pre-ignition turbulence on the course of vented gas and dust explosions. A vertical cylindrical explosion chamber of approximately 100 l volume and a length-to-diameter ratio (l/d) of 4.7 consisting of a steel bottom segment and three glass sections connected by steel flanges was used to perform the experiments. Sixteen small fans evenly distributed within the chamber produced turbulent fluctuations from 0 to 0.45 m/s. A Laser-Doppler-anemometer (LDA) was used to measure the flow and turbulence fields. During the experiments the pressure and in the case of dust explosions the dust concentration were measured. In addition, the flame propagation was observed by a high-speed video camera. A propane/nitrogen/oxygen mixture was used for the gas explosion experiments, while the dust explosions were produced by a cornstarch/air mixture. It turned out that the reduced explosion pressure increased with increasing turbulence intensity. This effect was most pronounced for small vents with low activation pressures, e.g. for bursting disks made from polyethylene foil. In this case, the overpressure at an initial turbulence of 0.45 m/s was twice that for zero initial turbulence. KW - Gas explosions KW - Dust explosions KW - Turbulence KW - Venting PY - 2006 DO - https://doi.org/10.1016/j.jlp.2007.03.001 SN - 0950-4230 SN - 1873-3352 VL - 19 IS - 2-3 SP - 194 EP - 199 PB - Butterworth CY - Guildford, Surrey AN - OPUS4-11833 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Osterloh, Kurt A1 - Hasenstab, Andreas A1 - Ewert, Uwe A1 - Krause, Martin A1 - Goebbels, Jürgen T1 - Mobile radiographische Untersuchung von Holz und Bäumen T2 - DGZfP Jahrestagung CY - Rostock, Deutschland DA - 2005-05-02 KW - Digitale Radiographie KW - Mobiles Röntgen PY - 2005 SN - 3-931381-64-1 N1 - Serientitel: Berichtsband / Deutsche Gesellschaft für zerstörungsfreie Prüfung e. V. – Series title: Berichtsband / Deutsche Gesellschaft für zerstörungsfreie Prüfung e. V. IS - 94-CD SP - 1(?) EP - 8(?) PB - DGZfP CY - Berlin AN - OPUS4-11866 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Hasenstab, Andreas A1 - Krause, Martin A1 - Rieck, C. A1 - Hillemeier, B. T1 - Materialuntersuchung an Holz mit niederfrequenter Ultraschall-Echotechnik N2 - Kurzfassung Die Anwendung niederfrequenter Ultraschall-Echotechnik mit Longitudinal- und Transversalwellen für die Materialuntersuchung von Holzbauteilen wird beschrieben. Weiterhin wird der Einfluss der Holzfasern auf die Schallgeschwindigkeiten und Oberflächenwellen an Hand von Messergebnissen aufgezeigt. Die Leistungsfähigkeit des Ultraschall-Echoverfahrens an ungeschädigten Holzkörpern und Körpern mit eingebrachten Bohrungen in Faserrichtung (Kernfäulnissimulation) wird dargestellt. Es ist zudem möglich, bei koppelmittelfreier Ankopplung mit Transversalwellen indirekt Fäulnis von der ungeschädigten Bauteilseite aus zu orten. Als Referenzverfahren werden die Bohrwiderstandsmethode oder die Röntgendurchstrahlung eingesetzt. T2 - Jahrestagung Zerstörungsfreie Materialprüfung 2004 CY - Salzburg, Österreich DA - 2004-05-17 PY - 2004 UR - http://www.ndt.net/article/dgzfp04/papers/v87/v87.htm SN - 3-931381-55-2 SP - 1(?) EP - 9(?) PB - DGZfP CY - Berlin AN - OPUS4-5216 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Hasenstab, Andreas A1 - Osterloh, Kurt A1 - Robbel, Joachim A1 - Krause, Martin A1 - Ewert, Uwe A1 - Hillemeier, B. T1 - Mobile Röntgenblitzröhren zum Auffinden von Holzschäden N2 - In diesem Beitrag wird die Anwendung von Radiographiesystemen zum Auffinden von Holzschäden beschrieben. Die Anlage besteht aus einer mobilen Röntgenblitzröhre und einem digitalen Radiographiesystem mit Speicherfolie oder einem Flachdetektor. An Hand der durchgeführten Versuche an Laub- und Nadelbäumen sowie an Eichenbalken der Marienkirche der Lutherstadt- Wittenberg wird die Detektion innerer Schäden gezeigt. T2 - Jahrestagung Zerstörungsfreie Materialprüfung 2004 CY - Salzburg, Österreich DA - 2004-05-17 PY - 2004 UR - http://www.ndt.net/article/dgzfp04/papers/p15/p15.htm SN - 3-931381-55-2 SP - 1(?) EP - 8(?) PB - DGZfP CY - Berlin AN - OPUS4-5217 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Hasenstab, Andreas A1 - Krause, Martin T1 - Ultraschall-Echo-Technik zur Ortung von Minderdicken und Schäden in Holzbauteilen T2 - DGZfP-Fachtagung Bauwerksdiagnose "Praktische Anwendungen Zerstörungsfreier Prüfungen" CY - Berlin, Deutschland DA - 2006-02-22 KW - Zerstörungsfreie Prüfung KW - Holz KW - Ultraschallecho KW - ZfP an Holzbauteilen KW - Fehlstellen KW - Minderdicken KW - Ultraschall-Echo KW - Fäulnis KW - Bauwesen PY - 2006 SN - 3-931381-71-4 SP - 1(?) EP - 11(?) PB - DGZfP CY - Berlin AN - OPUS4-14233 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hasenstab, Andreas A1 - Krause, Martin A1 - Osterloh, Kurt T1 - Testing Of Wooden Construction Elements with Ultrasonic Echo Technique and X-Ray T2 - 9th European Conference on NDT CY - Berlin, Germany DA - 2006-09-25 KW - NDT of Wood PY - 2006 SN - 3-931381-86-2 SP - 1(?) EP - 8(?) PB - European Federation for Non-Destructive Testing CY - Berlin AN - OPUS4-14422 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krause, Christina A1 - Schönhals, Andreas T1 - Phase transitions and molecular mobility of a discotic liquid crystal under nanoscale confinement N2 - The phase behavior and the molecular dynamics of a pyrene-based discotic liquid crystal when confined in nanoporous aluminum membranes with different pore sizes is studied by broadband dielectric spectroscopy and differential scanning calorimetry. In confinement the two phase transitions between plastic crystalline and hexagonal ordered phase at lower and from the latter to an isotropic state at higher temperatures are also observed, but two different phase structures close to the wall and in the pore center are evidenced by two peaks in the heat flow for the first time. While the former peak is independent of the pore size, the depression of the phase transition temperatures of the latter ones can be described by the Gibbs–Thomson equation. With decreasing pore size for both phase transitions the transition enthalpies decrease. A critical pore size for phase transformation of about 20 nm is estimated from the pore size dependence of the transition enthalpies. Like for the bulk, an a-relaxation is also observed in confinement. At the phase transition its relaxation rates show a discontinuity from which a dielectric phase transition temperature can be extracted. For temperatures above and below the phase transition the temperature of the relaxation rate can be approximated by an Arrhenius equation. The pore size dependence of the estimated apparent activation energies is ascribed to the interplay between pore size and interaction effects. The cooperative nature of the underlying molecular dynamics is indicated by the occurrence of the well-known compensation law. PY - 2013 DO - https://doi.org/10.1021/jp406010d SN - 1932-7447 SN - 1089-5639 VL - 117 IS - 38 SP - 19712 EP - 19720 PB - Soc. CY - Washington, DC AN - OPUS4-29336 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 - 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 - Krause, Christina A1 - Zorn, R. A1 - Emmerling, Franziska A1 - Falkenhagen, Jana A1 - Frick, B. A1 - Huber, P. A1 - Schönhals, Andreas T1 - Vibrational density of states of triphenylene based discotic liquid crystals: dependence on the length of the alkyl chain N2 - The vibrational density of states of a series of homologous triphenylene-based discotic liquid crystals HATn (n = 5, 6, 8, 10, 12) depending on the length of the aliphatic side chain is investigated by means of inelastic neutron scattering. All studied materials have a plastic crystalline phase at low temperatures, followed by a hexagonally ordered liquid crystalline phase at higher temperatures and a quasi isotropic phase at the highest temperatures. The X-ray scattering pattern for the plastic crystalline phase of all materials shows a sharp Bragg reflection corresponding to the intercolumnar distance in the lower q-range and a peak at circa 17 nm-1 related to intracolumnar distances between the cores perpendicular to the columns as well as a broad amorphous halo related to the disordered structure of the methylene groups in the side chains in the higher q-range. The intercolumnar distance increases linearly with increasing chain length for the hexagonal columnar ordered liquid crystalline phase. A similar behaviour is assumed for the plastic crystalline phase. Besides n = 8 all materials under study exhibit a Boson peak. With increasing chain length, the frequency of the Boson peak decreases and its intensity increases. This can be explained by a self-organized confinement model. The peaks for n = 10, 12 are much narrower than for n = 5, 6 which might imply the transformation from a rigid system to a softer one with increasing chain length. Moreover the results can also be discussed in the framework of a transition from an uncorrelated to a correlated disorder with increasing n where n = 8 might be speculatively considered as a transitional state. KW - X-ray scattering KW - Neutron scattering KW - Differential scanning calorimetry PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-304789 DO - https://doi.org/10.1039/c3cp55303e SN - 1463-9076 SN - 1463-9084 VL - 16 IS - 16 SP - 7324 EP - 7333 PB - The Royal Soc. of Chemistry CY - Cambridge AN - OPUS4-30478 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krause, Christina A1 - Zorn, R. A1 - Frick, B. A1 - Schönhals, Andreas T1 - Thermal properties and vibrational density of states of a nanoconfined discotic liquid crystal N2 - Neutron scattering is employed to investigate the vibrational density of states (VDOS) of the discotic liquid crystal 2,3,6,7,10,11-hexakis[hexyloxy] triphenylene (HAT6) confined to the pores of alumina oxide membranes with different pore sizes. Additionally, the phase transitions were studied by differential scanning calorimetry. The transitions were observed down to the smallest pore size. The decrease of the transition enthalpies versus inverse pore size for both transitions implies an increase of the amount of disordered amorphous material. By extrapolation of its pore size dependence, a critical pore diameter for structure formation of 17 nm is estimated. Similar to the bulk, excess contributions to the VDOS (Boson peak) are also observed for confined HAT6. The Boson peak gains in intensity and shifts to lower frequencies with decreasing pore diameter. This is discussed in the framework of a softening of HAT6 induced by the confinement due to a less-developed plastic crystalline state inside the pores compared to the bulk. KW - Discotic liquid crystals KW - Confinement KW - Neutron scattering KW - Boson peak PY - 2014 DO - https://doi.org/10.1007/s00396-014-3247-3 SN - 0303-402X SN - 1435-1536 VL - 292 IS - 8 SP - 1949 EP - 1960 PB - Springer CY - Berlin AN - OPUS4-31254 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kityk, A.V. A1 - Busch, M. A1 - Rau, D. A1 - Calus, S. A1 - Cerclier, C.V. A1 - Lefort, R. A1 - Morineau, D. A1 - Grelet, E. A1 - Krause, Christina A1 - Schönhals, Andreas A1 - Frick, B. A1 - Huber, P. T1 - Thermotropic orientational order of discotic liquid crystals in nanochannels: an optical polarimetry study and a Landau-de Gennes analysis N2 - Optical polarimetry measurements of the orientational order of a discotic liquid crystal based on a pyrene derivative confined in parallelly aligned nanochannels of monolithic, mesoporous alumina, silica, and silicon as a function of temperature, channel radius (3–22 nm) and surface chemistry reveal a competition of radial and axial columnar orders. The evolution of the orientational order parameter of the confined systems is continuous, in contrast to the discontinuous transition in the bulk. For channel radii larger than 10 nm we suggest several, alternative defect structures, which are compatible both with the optical experiments on the collective molecular orientation presented here and with a translational, radial columnar order reported in previous diffraction studies. For smaller channel radii our observations can semi-quantitatively be described by a Landau–de Gennes model with a nematic shell of radially ordered columns (affected by elastic splay deformations) that coexists with an orientationally disordered, isotropic core. For these structures, the cylindrical phase boundaries are predicted to move from the channel walls to the channel centres upon cooling, and vice-versa upon heating, in accord with the pronounced cooling/heating hystereses observed and the scaling behavior of the transition temperatures with the channel diameter. The absence of experimental hints of a paranematic state is consistent with a biquadratic coupling of the splay deformations to the order parameter. PY - 2014 DO - https://doi.org/10.1039/c4sm00211c SN - 1744-683X VL - 10 IS - 25 SP - 4522 EP - 4534 PB - RSC Publ. CY - Cambridge AN - OPUS4-30866 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krause, Martin A1 - Milmann, Boris A1 - Feldmann, Rüdiger A1 - Friese, Martin A1 - Wöstmann, Jens A1 - Zoëga, Andreas A1 - Sodeikat, C. T1 - Thickness measurement & quality assurance of floor slabs & diaphragm walls T2 - Structural faults & repair 2010 - International conference and exhibition CY - Edinburgh, Scotland, UK DA - 2010-06-15 KW - Ultrasonic echo KW - Radar KW - Impact-echo KW - Synthetic aperture focusing technique (SAFT) KW - Compaction faults PY - 2010 SN - 0-947644-67-9 SP - 1 EP - 9 PB - Engineering Technics Press CY - Edinburgh, Scotland AN - OPUS4-22897 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hasenstab, Andreas A1 - Krause, Martin A1 - Hillemeier, B. A1 - Rieck, C. T1 - Ultraschallecho-Messungen an Holz N2 - In der Praxis kann Fäulnis in Holzkonstruktionen ein großes Problem darstellen. Ein Fäulnisbefall kann zu einer Schädigung in der Gesamtkonstruktion führen. Zusammen mit der TU Berlin wurden an der Bundesanstalt für Materialforschung und -prüfung (BAM) Versuche mit Ultraschallecho zur Detektion von Bauteilrückwänden und verdeckten Hohlstellen durchgeführt. Hierbei werden Sender und Empfänger auf einer Bauteilseite angekoppelt, was eine große Anwendungsvielfalt ermöglicht. Im Rahmen der Versuche an der BAM wurden zylindrische Longitudinalwellenprüfköpfe in Zweikopftechnik mit 100 kHz angeregt und an den Probekörpern mit verschiedenen Koppelmitteln angekoppelt. Die Messergebnisse wurden graphisch als B-Bilder dargestellt und ausgewertet. Dabei zeigte sich, dass die Rückwand der fehlerfreien Probekörper klar geortet wird und eingebrachte Hohlstellen besonders gut detektiert werden können. KW - Zerstörungsfreie Prüfung KW - Ultraschallecho KW - Holz PY - 2006 DO - https://doi.org/10.1007/s00107-006-0124-x SN - 0018-3768 VL - 64 SP - 475 EP - 481 PB - Springer CY - Berlin AN - OPUS4-23056 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Feldmann, Rüdiger A1 - Zoёga, Andreas A1 - Milmann, Boris A1 - Krause, Martin T1 - Ortung tiefliegender Bewehrung durch Ultraschall mit bildgebender Phasenauswertung N2 - Die Ortung von schlaffer Bewehrung in Beton erfolgt routinemäßig mit bildgebenden Radar- oder Wirbelstromverfahren. Die Anwendung dieser Verfahren ist aber begrenzt, wenn es sich um die Ortung tiefliegender Bewehrung (ab ca. 30 cm) oder um jungen Beton handelt. Grund ist die Schwächung der Radarpulse durch oberflächennahe Bewehrung oder durch die Betonfeuchte. Das bildgebende Ultraschallechoverfahren bietet den Vorteil, dass die Ultraschallpulse in diesen Fällen eine wesentlich höhere Eindringtiefe erreichen. Im vorliegenden Beitrag wird eine Fallstudie vorgestellt, bei der mehrlagig eingebrachte Bewehrungseisen in einer nur einseitig zugänglichen 60 cm dicken Betonplatte geortet werden sollten, um eine Kernbohrung ohne Verkanten der Bohrkrone durchzuführen. Zur Ortung der Bewehrung wurde das Ultraschallechoverfahren mitScherwellen der Mittenfrequenz 50 kHz mit einem automatisch arbeitenden Bauwerksscanner eingesetzt. Aus den flächig aufgenommenen Messdaten wurde mit der Rekonstruktionsrechnung nach dem Prinzip der synthetischen Apertur (SAFT, Synthetic Aperture Focusing Technique) die Position der Bewehrungseisen bildhaft ortsgenau dargestellt. Dies gelingt mit einer Auswertungsoption, bei der die Phase der reflektierten Ultraschallpulse ermittelt und farbcodiert dargestellt wird (Phasenauswertung). Damit lassen sich Reflexionen der Bewehrung eindeutig von eventuellen Fehlstellen oder Rückwandechos unterscheiden. T2 - Fachtagung Bauwerksdiagnose 2014 CY - Berlin, Germany DA - 13.02.2014 KW - Ultraschallecho-Verfahren KW - SAFT KW - Bewehrung KW - Beton KW - Abbildungsverfahren PY - 2014 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-351056 UR - https://www.ndt.net/?id=15885 SN - 1435-4934 VL - 19 IS - 8 SP - 1 EP - 11 PB - NDT.net CY - Kirchwald AN - OPUS4-35105 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krause, Christina A1 - Zorn, R. A1 - Frick, B. A1 - Schönhals, Andreas T1 - Quasi- and inelastic neutron scattering to investigate the molecular dynamics of discotic molecules in the bulk N2 - In- and quasielastic neutron scattering is employed to investigate both the vibrational density of states and the molecular dynamics of two homologous discotic liquid crystals (DLC) with different length of the alkyl side chain based on a triphenylene derivate. For both compounds characteristic low frequency excess contributions to the vibrational density of states are found. Therefore it is concluded that these liquid crystals show a glass-like behaviour. Elastic scans further show that in these materials a rich molecular dynamics takes place. T2 - QENS/WINS 2014 - 11th International Conference on Quasielastic Neutron Scattering and 6th International Workshop on Inelastic Neutron Spectrometers CY - Autrans, France DA - 2014-05-11 PY - 2015 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-325477 DO - https://doi.org/10.1051/epjconf/20158302017 SN - 2100-014X VL - 83 SP - 02017-1 EP - 02017-4 PB - EDP Sciences CY - Les Ulis AN - OPUS4-32547 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Calus, S. A1 - Kityk, A.V. A1 - Borowik, L. A1 - Lefort, R. A1 - Morineau, D. A1 - Krause, Christina A1 - Schönhals, Andreas A1 - Busch, M. A1 - Huber, P. T1 - High-resolution dielectric study reveals pore-size-dependent orientational order of a discotic liquid crystal confined in tubular nanopores N2 - We report a high-resolution dielectric study on a pyrene-based discotic liquid crystal (DLC) in the bulk state and confined in parallel tubular nanopores of monolithic silica and alumina membranes. The positive dielectric anisotropy of the DLC molecule at low frequencies (in the quasistatic case) allows us to explore the thermotropic collective orientational order. A face-on arrangement of the molecular discs on the pore walls and a corresponding radial arrangement of the molecules is found. In contrast to the bulk, the isotropic-to-columnar transition of the confined DLC is continuous, shifts with decreasing pore diameter to lower temperatures, and exhibits a pronounced hysteresis between cooling and heating. These findings corroborate conclusions from previous neutron and x-ray-scattering experiments as well as optical birefringence measurements. Our study also indicates that the relative simple dielectric technique presented here is a quite efficient method in order to study the thermotropic orientational order of DLC-based nanocomposites. PY - 2015 DO - https://doi.org/10.1103/PhysRevE.92.012503 SN - 1539-3755 SN - 1063-651X VL - 92 IS - 1 SP - 012503-1 EP - 012503-6 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-33813 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 - 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 - GEN A1 - Taffe, Alexander A1 - Maierhofer, Christiane A1 - Krause, Martin A1 - Gardei, André A1 - Niederleithinger, Ernst A1 - Hasenstab, Andreas A1 - Hemmleb, Matthias A1 - Wiggenhauser, Herbert A1 - Borchardt, Kerstin T1 - ZfPBau-Kompendium 2004 N2 - Dieses Kompendium ist ein kurzgefasster Abriss, ein Leitfaden und auch ein Handbuch der für den Einsatz im Bauwesen geeigneten zerstörungsfreien Prüfverfahren. In strenger, stets gleicher Gliederung wird jede der mehr als 100 Untersuchungsmethoden in einem eigenen Geräteblatt beschrieben. Hinzu kommen Querverweise zu alternativen Prüfmethoden sowie zahlreiche Hinweise auf einschlägige Fachliteratur und zu bekannt gewordenen Geräteherstellern, Lieferanten und Dienstleistern. PY - 2007 N1 - Das "ZfPBau-Kompendium 2004" war eine Datenbank, die von 2007 bis 2015 im Internet verfügbar war; sie wurde ersatzlos vom Netz genommen, als sie nicht mehr aktuell war – The "ZfPBau-Kompendium 2004" was a database that was accessible on the internet from 2007 to 2015; it was deleted without replacement when it wasn't up-to-date anymore PB - Bundesanstalt für Materialforschung und -prüfung CY - Berlin AN - OPUS4-1497 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sieg, H. A1 - Krause, B.-C. A1 - Kästner, Claudia A1 - Böhmert, L. A1 - Lichtenstein, D. A1 - Tentschert, J. A1 - Jungnickel, H. A1 - Laux, P. A1 - Braeuning, A. A1 - Fessard, V. A1 - Thünemann, Andreas A1 - Luch, A. A1 - Lampen, A. T1 - Cellular Effects of In Vitro-Digested Aluminum Nanomaterials on Human Intestinal Cells N2 - Aluminum (Al) can be taken up from food, packaging, or the environment and thus reaches the human gastrointestinal tract. Its toxic potential after oral uptake is still discussed. The fate of different solid and ionic Al species during the passage through the digestive tract is the focus of this research, as well as the cellular effects caused by these different Al species. The present study combines the physicochemical processing of three recently studied Al species (metallic Al0, mineral Al2O3, and soluble AlCl3) in artificial digestion fluids with in vitro cell systems for the human intestinal barrier. Inductively coupled plasma mass spectrometry (ICP-MS) and small-angle X-ray scattering (SAXS) methods were used to characterize the Al species in the artificial digestion fluids and in cell culture medium for proliferating and differentiated intestinal Caco-2 cells. Cytotoxicity testing and cellular impedance measurements were applied to address the effects of digested Al species on cell viability and cell proliferation. Microarray-based transcriptome analyses and quantitative real-time PCR were conducted to obtain a deeper insight into cellular mechanisms of action and generated indications for cellular oxidative stress and an influence on xenobiotic metabolism, connected with alterations in associated signaling pathways. These cellular responses, which were predominantly caused by formerly ionic Al species and only at very high concentrations, were not impacted by artificial digestion. A two-directional conversion of Al between ionic species and solid particles occurred throughout all segments of the gastrointestinal tract, as evidenced by the presence of nanoscaled particles. Nevertheless, this presence did not increase the toxicity of the respective Al species. KW - SAXS KW - Small-angle X-ray scattering KW - Nanoparticle PY - 2020 DO - https://doi.org/10.1021/acsanm.9b02354 VL - 3 IS - 3 SP - 2246 EP - 2256 PB - American Chemical Society AN - OPUS4-50632 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sieg, H. A1 - Lehmann, C. A1 - Kästner, Claudia A1 - Krause, B. A1 - Burel, A. A1 - Chevance, S. A1 - Böhmert, L. A1 - Lichtenstein, D. A1 - Tentschert, J. A1 - Bräuning, A. A1 - Laux, A. A1 - Thünemann, Andreas A1 - Loipis, I. E. A1 - Fessard, V. A1 - Luch, A. A1 - Lampen, A. T1 - Effects of Al-, Ti- and Zn-containing nanomaterials on cell lines in vitro N2 - Among the different tested endpoints, Al- and Ticontaining nanomaterials did notshowany toxicity in intestinal cell lines in vitro. Nevertheless, this absence of effect was not due to an absence of exposure, since particle-specific uptake was reported. Metal particle uptake over a long time period might therefore be relevant for risk assessment of aluminum- and titanium-containing food products. T2 - 52nd Congress of the European-Societies-of-Toxicology (EUROTOX) CY - Seville, Spain DA - 04.09.2017 KW - Nanoparticles PY - 2017 DO - https://doi.org/10.1016/j.toxlet.2016.06.1954 SN - 0378-4274 VL - 258 SP - S272 PB - Elsevier Ltd. AN - OPUS4-40939 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Juling, S. A1 - Niedzwiecka, A. A1 - Böhmert, L. A1 - Lichtenstein, D. A1 - Selve, S. A1 - Braeuning, A. A1 - Thünemann, Andreas A1 - Krause, E. A1 - Lampen, A. T1 - Protein Corona Analysis of Silver Nanoparticles Links to Their Cellular Effects N2 - The breadth of applications of nanoparticles and the access to food-associated consumer products containing nanosized materials lead to oral human exposure to such particles. In biological fluids nanoparticles dynamically interact with biomolecules and form a protein corona. Knowledge about the protein corona is of great interest for understanding the molecular effects of particles as well as their fate inside the human body. We used a mass spectrometry-based toxicoproteomics approach to elucidate mechanisms of toxicity of silver nanoparticles and to comprehensively characterize the protein corona formed around silver nanoparticles in Caco-2 human intestinal epithelial cells. Results were compared with respect to the cellular function of proteins either affected by exposure to nanoparticles or present in the protein corona. A transcriptomic data set was included in the analyses in order to obtain a combined multiomics view of nanoparticle-affected cellular processes. A relationship between corona proteins and the proteomic or transcriptomic responses was revealed, showing that differentially regulated proteins or transcripts were engaged in the same cellular signaling pathways. Protein corona analyses of nanoparticles in cells might therefore help in obtaining information about the molecular consequences of nanoparticle treatment. KW - Silver nanoparticles KW - Protein KW - Small-angle X-ray scattering KW - SAXS PY - 2017 DO - https://doi.org/10.1021/acs.jproteome.7b00412 SN - 1535-3893 SN - 1535-3907 VL - 16 IS - 11 SP - 4020 EP - 4034 PB - Americal Chemical Society AN - OPUS4-42688 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sieg, H. A1 - Kästner, Claudia A1 - Krause, B. A1 - Meyer, T. A1 - Burel, A. A1 - Böhmert, L. A1 - Lichtenstein, D. A1 - Jungnickel, H. A1 - Tentschert, J. A1 - Laux, P. A1 - Braeuning, A. A1 - Estreal-Lopis, I. A1 - Gauffre, F. A1 - Fessard, V. A1 - Meijer, J. A1 - Luch, A. A1 - Thünemann, Andreas A1 - Lampen, A. T1 - Impact of an artificial digestion procedure on aluminum-containing nanomaterials N2 - Aluminum has gathered toxicological Attention based on relevant human exposure and its suspected hazardous potential. Nanoparticles from food supplements or Food contact materials may reach the human gastrointestinal tract. Here, we monitored the physicochemical fate of aluminum containing nanoparticles and aluminum ions when passaging an in vitro model of the human gastrointestinal tract. Smallangle X-ray scattering (SAXS), transmission electron microscopy (TEM), ion beam microscopy (IBM), secondary ion beam mass spectrometry (TOF-SIMS), and inductively coupled plasma mass spectrometry (ICP-MS) in the singleparticle mode were employed to characterize two aluminumcontaining nanomaterials with different particle core materials (Al0, γAl2O3) and soluble AlCl3. Particle size and shape remained unchanged in saliva, whereas strong Agglomeration of both aluminum nanoparticle species was observed at low pH in gastric fluid together with an increased ion release. The levels of free aluminum ions decreased in intestinal fluid and the particles deagglomerated, thus liberating primary particles again. Dissolution of nanoparticles was limited and substantial changes of their shape and size were not detected. The amounts of particle-associated phosphorus, chlorine, potassium, and calcium increased in intestinal fluid, as compared to nanoparticles in standard dispersion. Interestingly, nanoparticles were found in the intestinal fluid after addition of ionic aluminum. We provide a comprehensive characterization of the fate of aluminum nanoparticles in simulated gastrointestinal fluids, demonstrating that orally ingested nanoparticles probably reach the intestinal epithelium. The balance between dissolution and de novo complex formation should be considered when evaluating nanotoxicological experiments. KW - Small-angle X-ray scattering KW - SAXS KW - Nanoparticle PY - 2017 DO - https://doi.org/10.1021/acs.langmuir.7b02729 SN - 1520-5827 SN - 0743-7463 VL - 33 IS - 40 SP - 10726 EP - 10735 PB - Americal Chemical Society AN - OPUS4-42438 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krause, B. A1 - Meyer, T. A1 - Sieg, H. A1 - Kästner, Claudia A1 - Reichardt, P. A1 - Tentschert, J. A1 - Jungnickel, H. A1 - Estrela-Lopis, I. A1 - Burel, A. A1 - Chevance, S. A1 - Gauffre, F. A1 - Jalili, P. A1 - Meijer, J. A1 - Böhmert, L. A1 - Braeuning, A. A1 - Thünemann, Andreas A1 - Emmerling, Franziska A1 - Fessard, V. A1 - Laux, P. A1 - Lampen, A. A1 - Luch, A. T1 - Characterization of aluminum, aluminum oxide and titanium dioxide nanomaterials using a combination of methods for particle surface and size analysis N2 - The application of appropriate analytical techniques is essential for nanomaterial (NM) characterization. In this study, we compared different analytical techniques for NM analysis. Regarding possible adverse health effects, ionic and particulate NM effects have to be taken into account. As NMs behave quite differently in physiological media, special attention was paid to techniques which are able to determine the biosolubility and complexation behavior of NMs. Representative NMs of similar size were selected: aluminum (Al0) and aluminum oxide (Al2O3), to compare the behavior of metal and metal oxides. In addition, titanium dioxide (TiO2) was investigated. Characterization techniques such as dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) were evaluated with respect to their suitability for fast characterization of nanoparticle dispersions regarding a particle's hydrodynamic diameter and size distribution. By application of inductively coupled plasma mass spectrometry in the single particle mode (SP-ICP-MS), individual nanoparticles were quantified and characterized regarding their size. SP-ICP-MS measurements were correlated with the information gained using other characterization techniques, i.e. transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The particle surface as an important descriptor of NMs was analyzed by X-ray diffraction (XRD). NM impurities and their co-localization with biomolecules were determined by ion beam microscopy (IBM) and confocal Raman microscopy (CRM). We conclude advantages and disadvantages of the different techniques applied and suggest options for their complementation. Thus, this paper may serve as a practical guide to particle characterization techniques. KW - Small-angle X-ray scattering KW - SAXS PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-447057 DO - https://doi.org/10.1039/C8RA00205C SN - 2046-2069 VL - 8 IS - 26 SP - 14377 EP - 14388 PB - The Royal Society of Chemistry AN - OPUS4-44705 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sieg, H. A1 - Braeuning, C. A1 - Kunz, B. M. A1 - Daher, H. A1 - Kästner, C. A1 - Krause, B.-C. A1 - Meyer, T. A1 - Jalili, P. A1 - Kogeveen, K. A1 - Böhmert, L. A1 - Lichtenstein, D. A1 - Burel, A. A1 - Chevance, S. A1 - Jungnickel, H. A1 - Tentschert, J. A1 - Laux, P. A1 - Braeuning, A. A1 - Gauffre, F. A1 - Fessard, V. A1 - Meijer, J. A1 - Estrela-Lopis, I. A1 - Thünemann, Andreas A1 - Luch, A. A1 - Lampen, A. T1 - Uptake and molecular impact of aluminum-containing nanomaterials on human intestinal caco-2 cells N2 - Aluminum (Al) is one of the most common elements in the earth crust and increasingly used in food, consumer products and packaging. Its hazard potential for humans is still not completely understood. Besides the metallic form, Al also exists as mineral, including the insoluble oxide, and in soluble ionic forms. Representatives of these three species, namely a metallic and an oxidic species of Al-containing nanoparticles and soluble aluminum chloride, were applied to human intestinal cell lines as models for the intestinal barrier. We characterized physicochemical particle parameters, protein corona composition, ion release and cellular uptake. Different in vitro assays were performed to determine potential effects and molecular modes of Action related to the individual chemical species. For a deeper insight into signaling processes, microarray transcriptome analyses followed by bioinformatic data analysis were employed. The particulate Al species showed different solubility in biological media. Metallic Al nanoparticles released more ions than Al2O3 nanoparticles, while AlCl3 showed a mixture of dissolved and agglomerated particulate entities in biological media. The protein corona composition differed between both nanoparticle species. Cellular uptake, investigated in transwell experiments, occurred predominantly in particulate form, whereas ionic Al was not taken up by intestinal cell lines. Transcellular transport was not observed. None of the Al species showed cytotoxic effects up to 200 mg Al/mL. The transcriptome analysis indicated mainly effects on oxidative stress pathways, xenobiotic metabolism and metal homeostasis. We have shown for the first time that intestinal cellular uptake of Al occurs preferably in the particle form, while toxicological effects appear to be ion-related. KW - Small-angle x-ray scattering KW - SAXS KW - Nanopatricle PY - 2018 DO - https://doi.org/10.1080/17435390.2018.1504999 SN - 1743-5390 VL - 12 IS - 9 SP - 992 EP - 1013 PB - Taylor & Francis AN - OPUS4-47432 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -