TY - JOUR A1 - Nirmalananthan-Budau, Nithiya A1 - Behnke, Thomas A1 - Hoffmann, Katrin A1 - Kage, Daniel A1 - Gers-Panther, Charlotte F. A1 - Frank, Walter A1 - Müller, Thomas J. J. A1 - Resch-Genger, Ute T1 - Crystallization and Aggregation-Induced Emission in a Series of Pyrrolidinylvinylquinoxaline Derivatives N2 - Aggregation-induced emission (AIE) has been meanwhile observed for many dye classes and particularly for fluorophores containing propeller-like groups. Herein, we report on the AIE characteristics of a series of four hydrophobic pyrrolidinylvinylquinoxaline (PVQ) derivatives with phenyl, pyrrolyl, indolyl, and methoxythienyl substituents used to systematically vary the torsion angle between this substituent at the quinoxaline C2 position and the planar PVQ moiety. These molecules, which are accessible via four- or five-component one-pot syntheses, were spectroscopically studied in organic solvents and solvent−water mixtures, as dye aggregates, solids, and entrapped in polystyrene particles (PSP). Steady-state and time-resolved fluorescence measurements revealed a strong fluorescence enhancement for all dyes in ethanol−water mixtures of high water content, accompanying the formation of dye aggregates with sizes of a few hundred nm, overcoming polarity and H-bonding-induced fluorescence quenching of the chargetransfer-type emission of these PVQ dyes. The size and shape of these dye aggregates and the size of the AIE effect are controlled by the water content and the substituent-dependent torsion angle that influences the nucleation process and the packing of the molecules during aggregation. Staining of 1 μm-sized carboxy-functionalized PSP with the PVQ dyes resulted also in a considerable increase in the fluorescence quantum yield and lifetime, reflecting the combined influence of the restricted molecular motion and the reduced polarity of the dye microenvironment. KW - Spectroscopy KW - AIE KW - Aggregates KW - Nanoparticle PY - 2018 DO - https://doi.org/10.1021/acs.jpcc.8b01425 SN - 1932-7447 N1 - Geburtsname von Nirmalananthan-Budau, Nithiya: Nirmalananthan, N. - Birth name of Nirmalananthan-Budau, Nithiya: Nirmalananthan, N. VL - 122 IS - 20 SP - 11119 EP - 11127 PB - ACS Publications AN - OPUS4-45176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gradt, Thomas A1 - Schneider, Thomas A1 - Lingertat, J. A1 - Hathiramani, D. A1 - Junghanns, P. A1 - Aßmus, Kristin A1 - Schauer, F. T1 - Cryogenic vacuum tests of scaled down narrow support elements for the W7-X coil system KW - Wendelstein 7-X KW - Magnet system KW - Narrow support elements KW - Friction KW - MoS2 PY - 2009 DO - https://doi.org/10.1016/j.fusengdes.2008.11.075 SN - 0920-3796 VL - 84 IS - 2-6 SP - 840 EP - 843 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-19662 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Lingertat, J. A1 - Gradt, Thomas A1 - Hathiramani, D. A1 - Junghanns, P. A1 - Laux, M. A1 - Meine, Kerstin A1 - Schauer, F. A1 - Schneider, Thomas T1 - Tribological performance of MoS2 coatings in liquid helium and at high loads N2 - The main part of a narrow support element (NSE) of the W7-X superconducting coil system is an aluminium bronze pad, PVD coated on its spherical surface with MoS2, which slides against the flat surface of the stainless steel coil housing, coated with MoS2 spray. The operational requirements of the NSEs are: vacuum of p < 10-6 mbar, temperature T ~4 K, maximum load P ~1500 kN, typical displacement ≤5 mm, smooth sliding and no stick-slip events. The paper describes test results obtained with a downscaled NSE at T = 4.2 and 77 K. During the test the NSEs were submerged in liquid helium and nitrogen, respectively. Whereas the LN2 test ran smoothly for up to ~15,000 cycles, the test in LHe showed stick-slip from the very first cycle. The stick-slip disappeared after ~50 cycles. Post mortem analysis of the tested parts revealed that in case of LHe the sprayed MoS2 film was removed during the first 30-100 cycles by blistering and flaking. The reason for the loss of adhesion at LHe temperature is not known, several possible causes are under discussion. Further experiments under vacuum and at T ~4 K are being prepared which are expected to help in clarifying the issue. KW - Stellarator KW - Wendelstein 7-X KW - Mechanical structure KW - Narrow support elements KW - MoS2 KW - Lubrication KW - T=4K PY - 2009 DO - https://doi.org/10.1016/j.fusengdes.2009.01.069 SN - 0920-3796 VL - 84 IS - 7-11 SP - 1192 EP - 1196 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-19745 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Baytekin, H. Tarik A1 - Wirth, Thomas A1 - Gross, Thomas A1 - Sahre, Mario A1 - Unger, Wolfgang A1 - Theisen, J. A1 - Schmidt, M. T1 - Surface analytical characterization of micro-fluidic devices hot embossed in polymer wafers: Surface chemistry and wettability N2 - Recently, time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) instrumentation has been used to address areas of interest within micro-fluidic devices providing full access to the surface chemistry established at the bottom of micro-channels therein. After careful calibration, information on surface chemistry as obtained by ToF-SIMS or XPS can be interpreted in terms of wettability expressed as contact angles which are then characteristic for the inner walls of micro-channels. Standard contact angle measurement is not applicable in micro-channels. The approach has been demonstrated to be successful with two different micro-fluidic devices hot embossed into high-end quality poly(methyl methacrylate) (PMMA) or Polycarbonate wafers. A pre-selected surface chemistry at micro-channel walls can be established by plasma technologies but ageing and rinsing effects have to be under control. A combination of ToF-SIMS, XPS and contact angle measurement techniques has been demonstrated to provide the required information. Finally, it is shown by ToF-SIMS and XPS analysis that in the production of micro-fluidic parts during practical processing using hot embossing technologies, material originating from cover foils will reside on the polymer wafer's surface. Moreover, residues of releasing agents as silicone oil used during processing can be detected by ToF-SIMS. Both cover foil residues and silicones are issues of trouble shooting in micro-fluidics because they will change contact angles efficiently. KW - Micro-fluidic device KW - PMMA KW - Polycarbonate KW - Plasma treatment KW - Wettability KW - ToF-SIMS KW - XPS PY - 2010 DO - https://doi.org/10.1002/sia.3149 SN - 0142-2421 SN - 1096-9918 VL - 42 IS - 8 SP - 1417 EP - 1431 PB - Wiley CY - Chichester AN - OPUS4-21712 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Baytekin, H.T. A1 - Wirth, Thomas A1 - Gross, Thomas A1 - Treu, Dieter A1 - Sahre, Mario A1 - Theisen, J. A1 - Schmidt, M. A1 - Unger, Wolfgang T1 - Determination of wettability of surface-modified hot-embossed polycarbonate wafers used in microfluidic device fabrication via XPS and ToF-SIMS N2 - The wettability of the surfaces inside the microchannels of a microfluidic device is an important property considering a liquid flows through them. Contact angle measurements usually applied to test the wettability of surfaces cannot be used for an analysis of microchannel walls within microfluidic devices. A workaround is the use of surface analytical methods, which are able to reach points of interest in microchannels and may provide information on the surface chemistry established there. In calibrating these methods by using flat polymer wafers, where the contact angle can be measured as usual, data measured in real microchannels can be evaluated in terms of wetting properties. Reference wafers of bisphenol-A polycarbonate, a polymeric material that is often used in fluidic microdevice fabrication, were treated under different oxygen plasma conditions. The modified surfaces were characterized by using XPS, time of flight (ToF)-SIMS and atomic force microscope (AFM). Surface chemistry and surface topography have been correlated with contact angle measurements. In addition, effects of ageing or rinsing after plasma treatment have also been investigated. KW - Oxygen plasma KW - Polycarbonate KW - XPS KW - ToF-SIMS KW - Principal component analysis PY - 2008 DO - https://doi.org/10.1002/sia.2724 SN - 0142-2421 SN - 1096-9918 VL - 40 IS - 3-4 SP - 358 EP - 363 PB - Wiley CY - Chichester AN - OPUS4-17340 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gradt, Thomas A1 - Schneider, Thomas A1 - Lingertat, J. A1 - Hathiramani, D. T1 - MoS2-Schmierung für hochbelastete Stützelemente zwischen supraleitenden Magnetspulen T2 - 49. Tribologie-Fachtagung - Reibung, Schmierung und Verschleiß - Forschung und praktische Anwendungen CY - Göttingen, Deutschland DA - 2008-09-22 KW - Tribologie KW - Molybdändisulfid KW - Stick-Slip KW - Supraleitung KW - Kernfusion PY - 2008 SN - 978-3-00-025676-9 VL - I SP - 13/1 EP - 13/10 AN - OPUS4-18366 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gradt, Thomas A1 - Schneider, Thomas A1 - Lingertat, J. A1 - Hathiramani, D. A1 - Schauer, F. T1 - MoS2-Schmierung für hochbelastete Stützelemente zwischen supraleitenden Magnetspulen KW - Kernfusion KW - Supraleitende Magnete KW - Kryotribologie KW - Vakuumtribologie KW - Stick-Slip KW - MoS2 PY - 2009 SN - 0724-3472 VL - 56 IS - 5 SP - 24 EP - 28 PB - Expert Verlag CY - Renningen AN - OPUS4-20726 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kasch, Thomas A1 - Binder, Christian A1 - Herrmann, Peter A1 - Brock, Thomas A1 - Heise, J. ED - Rockland, U. T1 - Einfluss von Keramikbeschichtungen auf das Abbrandverhalten metallischer Werkstoffe in hochverdichtetem Sauerstoff N2 - Nach nationalen und internationalen Vorschriften müssen Armaturen und Anlagenteile für hoch verdichteten Sauerstoff ausbrennsicher sein. Diese Forderung kann technisch dadurch erreicht werden, dass sicherheitstechnisch geeignete nichtmetallische und metallische Werkstoffe verwendet werden. Für die Auswahl geeigneter metallischer Werkstoffe sind der Verwendungszweck der Armatur, die Betriebsbedingungen sowie werkstoffspezifische Parameter zu berücksichtigen. Einige metallische Werkstoffe besitzen gute Materialeigenschaften, lassen sich leicht be- bzw. verarbeiten und sind kostengünstig in der Beschaffung, dürfen aber aufgrund ihres ungünstigen Abbrandverhaltens in Sauerstoff nicht eingesetzt werden. Es besteht daher ein großes Interesse, den sicherheitstechnischen Beschränkungen dieser Werkstoffe durch geeignete Maßnahmen entgegenzuwirken. Eine mögliche Lösung stellt die Beschichtung dieser Werkstoffe beispielsweise mit Keramik dar, um den unmittelbaren Kontakt mit dem Sauerstoff zu verhindern. Um den Einfluss dieser Keramikschichten auf das Abbrandverhalten metallischer Werkstoffe zu untersuchen, wird die im Standard ASTM G124 [1] beschriebene Apparatur und das in der einschlägigen Literatur beschriebene Bewertungsverfahren verwendet. Die Ergebnisse zeigen, dass für keramikbeschichtete metallische Werkstoffe ein Abbrand erst bei höheren Sauerstoffdrücken erfolgt. T2 - 10. Kolloquium zu Fragen der chemischen und physikalischen Sicherheitstechnik CY - Berlin, Deutschland DA - 2004-06-17 PY - 2004 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-48462 SP - 25 EP - 27 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-4846 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromm, Arne A1 - Thomas, Maximilian A1 - Kannengießer, Thomas A1 - Gibmeier, J. A1 - Vollert, F. T1 - Assessment of the Solidification Cracking Susceptibility of Welding Consumables in the Varestraint Test by Means of an Extended Evaluation Methodology N2 - Various test methods are available for assessing the susceptibility of materials to solidification cracking during welding. In the widely used Varestraint test, the crack length is selected as a criterion as a function of the applied bending strain. Unfortunately, the crack length does not characterize the material behavior alone but depends to varying degrees on the individual test parameters used, which makes the interpretation of the results difficult. In addition, the crack length is not comparable under different test conditions. To overcome these disadvantages, we have developed a novel evaluation methodology that decouples the machine influence from the material behavior. The measured crack length is related to the maximum possible value specified by welding speed and deformation time. This relative crack length is calculated numerically, considering the orientation of the cracks. Experiments on two high-alloy martensitic welding consumables show that, in contrast to the conventional evaluation, a comparison of different welding parameters becomes possible. Furthermore, the strain rate proved to be a suitable crack criterion in agreement with Prokhorov's hot cracking model. KW - Welding KW - Solidification cracking KW - Varestraint test PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-545780 DO - https://doi.org/10.1002/adem.202101650 SN - 1438-1656 SP - 2101650 PB - Wiley online library AN - OPUS4-54578 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thomas, Maximilian A1 - Vollert, F. A1 - Weidemann, Jens A1 - Gibmeier, J. A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Surface- and volume-based investigation on influences of different Varestraint testing parameters and chemical compositions on solidification cracking in LTT filler metals N2 - The subject of this study is how, and to what extent, Varestraint/Transvarestraint test results are influenced by both testing parameters and characteristics of evaluation methods. Several different high-alloyed martensitic LTT (low Transformation temperature) filler materials, CrNi and CrMn type, were selected for examination due to their rather distinctive solidification cracking behaviour, which aroused interest after previous studies. First, the effects of different process parameter sets on the solidification cracking response were measured using standard approaches. Subsequently, microfocus X-ray computer tomography (μCT) scans were performed on the specimens. The results consistently show sub-surface cracking to significant yet varying extents. Different primary solidification types were found using wavelength dispersive X-ray (WDX) analysis conducted on filler metals with varying Cr/Ni equivalent ratios. This aspect is regarded as the main difference between the CrNiand CrMn-type materials in matters of cracking characteristics. Results show that when it comes to testing of modern highperformance alloys, one set of standard Varestraint testing parameters might not be equally suitable for all materials. Also, to properly accommodate different solidification types, sub-surface cracking has to be taken into account. KW - Solidification cracking KW - Varestraint testing KW - MVT KW - LTT filler metal KW - Microfocus X-ray computer tomography (μCT) PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-506039 DO - https://doi.org/10.1007/s40194-020-00895-2 VL - 64 SP - 913 EP - 923 PB - Springer Nature CY - Heidelberg, New York AN - OPUS4-50603 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kim, K.J. A1 - Kim, J.W. A1 - Moon, D.W. A1 - Wirth, Thomas A1 - Hodoroaba, Vasile-Dan A1 - Gross, Thomas A1 - Unger, Wolfgang A1 - Jordaan, W. A1 - Staden, M.v. A1 - Prins, S. A1 - Wang, H. A1 - Song, X. A1 - Zhang, L. A1 - Fujimoto, T. A1 - Kojima, I. T1 - Final report on key comparison K67 and parallel pilot study P108: measurement of composition of a thin Fe-Ni alloy film N2 - The Key Comparison K67 and the parallel Pilot Study P108 on quantitative analysis of thin alloy films have been completed in the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The aim of these inter-laboratory comparisons is to determine the degree of equivalence in the measurement capability of national metrology institutes (NMIs) and designated institutes (DIs) for the determination of the composition of thin alloy films. The measurand is expressed in atomic percent. A Fe-Ni alloy film with a certified composition was available for the participants of the inter-laboratory comparison. It has been used as a reference specimen to determine the relative sensitivity factors (RSF) of Fe and Ni for the different analytical methods used by the participants to determine the composition of the test sample. As was shown in the preceding Pilot Study P98, the degrees of equivalence in the measurement capabilities of the participants can be improved in that way. The composition of the reference specimen was certified by inductively coupled plasma mass spectrometry (ICP-MS) using the isotope dilution method. The in-depth and lateral homogeneity, determined in terms of elemental composition, of the certified reference sample and the unknown test sample were confirmed by secondary ion mass spectrometry (SIMS) using C60 primary ions by the leading laboratory. Five laboratories participated in the key comparison. Four of them used x-ray photoelectron spectroscopy (XPS) and one Auger electron spectroscopy (AES). One laboratory participated in the parallel P108 pilot study using electron probe micro analysis with an energy-dispersive spectrometer (ED EPMA) and XPS. KW - XPS KW - AES KW - EDX KW - Fe-Ni alloy film KW - Key comparison KW - CCQM PY - 2010 DO - https://doi.org/10.1088/0026-1394/47/1A/08011 SN - 0026-1394 SN - 1681-7575 VL - 47 IS - 1A SP - 08011-1 - 08011-15 PB - Inst. of Physics Publ. CY - Bristol AN - OPUS4-21045 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kim, K.J. A1 - Unger, Wolfgang A1 - Kim, J.W. A1 - Moon, D.W. A1 - Gross, Thomas A1 - Hodoroaba, Vasile-Dan A1 - Schmidt, Dieter A1 - Wirth, Thomas A1 - Jordaan, W. A1 - van Staden, M. A1 - Prins, S. A1 - Zhang, L. A1 - Fujimoto, T. A1 - Song, X.P. A1 - Wang, H. T1 - Inter-laboratory comparison: quantitative surface analysis of thin Fe-Ni alloy films N2 - An international interlaboratory comparison of the measurement capabilities of four National Metrology Institutes (NMIs) and one Designated Institute (DI) in the determination of the chemical composition of thin Fe-Ni alloy films was conducted via a key comparison (K-67) of the Surface Analysis Working Group of the Consultative Committee for Amount of Substance. This comparison was made using XPS (four laboratories) and AES (one laboratory) measurements. The uncertainty budget of the measured chemical composition of a thin alloy film was dominated by the uncertainty of the certified composition of a reference specimen which had been determined by inductively coupled plasma mass spectrometry using the isotope dilution method. Pilot study P-98 showed that the quantification using relative sensitivity factors (RSFs) of Fe and Ni derived from an alloy reference sample results in much more accurate result in comparison to an approach using RSFs derived from pure Fe and Ni films. The individual expanded uncertainties of the participants in the K-67 comparison were found to be between 2.88 and 3.40 atomic %. The uncertainty of the key comparison reference value (KCRV) calculated from individual standard deviations and a coverage factor (k) of 2 was 1.23 atomic %. KW - Quantification KW - Fe-Ni alloy KW - Uncertainty KW - Key comparison KW - Traceability PY - 2012 DO - https://doi.org/10.1002/sia.3795 SN - 0142-2421 SN - 1096-9918 VL - 44 IS - 2 SP - 192 EP - 199 PB - Wiley CY - Chichester AN - OPUS4-24505 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -