TY - JOUR A1 - Bonse, Jörn A1 - Baudach, Steffen A1 - Kautek, Wolfgang A1 - Geuss, Markus A1 - Sturm, Heinz T1 - The precision of the femtosecond-pulse laser ablation of TiN films on silicon N2 - Ti:sapphire laser pulses of 130 fs and 800 nm were focused on 3.2-7m-thick TiN films by a 60-mm focal length lens in air. The morphology of the ablated areas generated by laser pulses at a fluence slightly above the ablation threshold was characterized in dependence on the pulse number by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The cavity profiles, depths, diameters, and volumes were quantitatively evaluated by AFM. The polarization state of the laser light is discussed as a further parameter, in addition to fluence and pulse number, that influences and controls the ablation precision of these materials. It was observed that circularly polarized radiation enhances the average ablation rates and reduces the roughness in the cavities by a factor of 2-3 as compared to linearly polarized radiation of the same incident laser fluence. Special attention was paid to the interfacial region between the coating and substrate. Ultrashort-pulse laser drilling into the Si substrate revealed the generation of columnar features which even may surmount the original coating under laser conditions. T2 - 5th International Conference on Laser Ablation ; COLA '99 CY - Göttingen, Germany DA - 1999-07-19 KW - Laser ablation KW - Picosecond PY - 1999 DO - https://doi.org/10.1007/s003390051425 SN - 0947-8396 VL - 69 IS - 7 SP - S399 EP - S402 PB - Springer CY - Berlin AN - OPUS4-778 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hartmann, S A1 - Sturm, Heinz A1 - Blaudeck, T A1 - Hoelck, O A1 - Hermann, S A1 - Schulz, SE A1 - Wunderle, B. T1 - Experimental and computational studies on the role of surface functional groups in the mechanical behavior of interfaces between single-walled carbon nanotubes and metals N2 - To study the mechanical interface behavior of single-walled carbon nanotubes (CNTs) embedded in a noble metal, we performed CNT-metal pull-out tests with in situ scanning electron microscope experiments. Molecular dynamics (MD) simulations were conducted to predict force-displacement data during pull-out, providing critical forces for failure of the system. In MD simulations, we focused on the influence of carboxylic surface functional groups (SFGs) covalently linked to the CNT. Experimentally obtained maximum forces between 10 and 102 nN in palladium and gold matrices and simulated achievable pulling forces agree very well. The dominant failure mode in the experiment is CNT rupture, although several pull-out failures were also observed. We explain the huge scatter of experimental values with varying embedding length and SFG surface density. From simulation, we found that SFGs act as small anchors in the metal matrix and significantly enhance the maximum forces. This interface reinforcement can lead to tensile stresses sufficiently high to initiate CNT rupture. To qualify the existence of carboxylic SFGs on our CNT material, we performed analytical investigation by means of fluorescence labeling of surface species and discuss the results. With this contribution, we focus on a synergy between computational and experimental approaches involving MD simulations, nano scale testing, and analytics (1) to predict to a good degree of accuracy maximum pull-out forces of single-walled CNTs embedded in a noble metal matrix and (2) to provide valuable input to understand the underlying mechanisms of failure with focus on SFGs. This is of fundamental interest for the design of future mechanical sensors incorporating piezoresistive single-walled CNTs as the sensing element. KW - Oxygen-containing functionalities KW - Molecular-dynamics KW - Structural characterization KW - Reinforced composites KW - Raman spectroscopy KW - Shear strength KW - Polymer matrix KW - Pull-out KW - Simulation KW - Purification PY - 2016 DO - https://doi.org/10.1007/s10853-015-9142-6 SN - 0022-2461 SN - 1573-4803 VL - 51 IS - 3 SP - 1217 EP - 1233 AN - OPUS4-35795 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sturm, Heinz A1 - Schulz, Eckhard T1 - Local AC current contrast on carbon fiber surfaces imaged by scanning force microscopy N2 - After a delamination process in a C-fiber reinforced polymer composite, the identification of the polymer residue of poly-(phenylene sulphide) on carbon fiber surfaces gives important information on the composite failure mechanism. Using scanning force microscopy (SFM) in its lateral force imaging mode or with the stiffness imaging mode, it is almost impossible to distinguish the two composite components owing to a very low material-based contrast of the local friction and compliance. The new technique using contrast based on a local AC current measurement allows a clear identification of the conducting carbon fiber and the non-conducting polymer coverage. KW - Matrix adhesion KW - Films KW - Photoconduction KW - Composites PY - 1995 DO - https://doi.org/10.1002/actp.1995.010460505 SN - 0323-7648 SN - 1521-4044 VL - 46 IS - 5 SP - 379 EP - 384 PB - Wiley-VCH Verl. CY - Weinheim, Germany AN - OPUS4-6848 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Munz, Martin A1 - Schulz, Eckhard A1 - Sturm, Heinz T1 - Reliability of polymer materials - the nanoscopic view on interphases T2 - Kick-off Meeting zu einem gemeinsamen DAAD-Projekt mit der Universidad Pais Vasco (UVP), Dept. of Chemical and Environmental Engineering, Industrial Engineering School (EITI), Materials and Technologies Group CY - San Sebastián, Spain DA - 2002-08-08 PY - 2002 SP - 1(?) EP - 12(?) AN - OPUS4-1832 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - SFM-Nanomechanics - Constant Dynamic Indentation- and Harmonically Modulated Friction Force- Microscopy T2 - Workshop: Rastersondenmikroskopie in Forschung und Industrie an der GH Wuppertal CY - Wuppertal, Germany DA - 1999-03-11 PY - 1999 AN - OPUS4-6495 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Physical properties of nanometer sized particles characterised by Scanning Probe Microscopy Techniques T2 - 2nd German Brazilian Workshop on Applied Surface Science CY - Templin, Germany DA - 1998-09-21 PY - 1998 AN - OPUS4-6454 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Heyde, M. A1 - Sturm, Heinz T1 - A new application of scanning probe microscopy piezos T2 - Raster-Sonden-Mikroskopien und organische Materialien VII CY - Berlin, Germany DA - 1998-10-07 PY - 1998 AN - OPUS4-6466 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Barthel, Anne-Kathrin A1 - Wachtendorf, Volker A1 - Sturm, Heinz A1 - Meyer-Plath, Asmus ED - Reichert, T. T1 - Irradiation-induced surface changes on CNT-filled polymeric materials N2 - The present study examines weathering-related degradation mechanisms of CNT-containing polymers and discusses whether and under what conditions degradation might lead to the release of nanoscale components. For this purpose, the study used accelerated artificial aging. The photodegradation of composites based polycarbonate containing multi-walled CNTs of type "Baytubes C150P" was studied under irradiation with a Xenon-arc irradiation device (λ-cut-off at 290 nm). Resulting surface modifications were evaluated with complementary chemical and microscopic characterization techniques. At sufficiently high radiation dose, a significant degradation of the matrix was observed for some of the polymers under examination which led to entangled networks of uncovered CNT at the composite surface. By investigation of potential exposure mechanisms of CNTs in polymer composites, the present work contributes to the risk assessment of CNT-containing products. T2 - 6th European weathering symposium Natural and artificial ageing of polymers CY - Bratislava, Slovak Republic DA - 11.09.2013 PY - 2013 SN - 978-3-9813136-8-0 N1 - Serientitel: CEEES Publication – Series title: CEEES Publication IS - 16 SP - 295 EP - 308 AN - OPUS4-31161 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Solomun, Tihomir A1 - Sturm, Heinz A1 - Wellhausen, R. A1 - Seitz, H. T1 - Interaction of a single-stranded DNA-binding protein g5p with DNA oligonucleotides immobilised on a gold surface N2 - We report surface plasmon resonance (spr) and confocal fluorescence results concerning the interaction of a gene-5-protein (g5p) with single-stranded DNA oligonucleotides (dT25) tethered to a gold surface. The spr data show that a highly stable g5p–ssDNA complex is readily formed on a gold surface with koff = 1.7 × 10-3 s-1. The extent of the complexion indicated involvement of the cooperative protein–protein interactions within the binding to DNA. In the experiments where dT25 coexist with g5p in the solution, the fluorescence data show that g5p also mediates the binding between the non-complementary oligonucleotides in the solution and those immobilised on the surface. KW - Single stranded DNA KW - g5p protein PY - 2012 DO - https://doi.org/10.1016/j.cplett.2012.03.017 SN - 0009-2614 SN - 1873-4448 VL - 533 SP - 92 EP - 94 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-26525 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Solomun, Tihomir A1 - Schimanski, A. A1 - Sturm, Heinz A1 - Mix, Renate A1 - Illenberger, E. T1 - Surface Modification of Polyamides by Direct Fluorination N2 - Bulk samples and thin films of polyamides (PA6 and PA12) were exposed to fluorine (1 - 10 vol.-% F2 in N2) and analysed with photoelectron (XPS) and infrared spectroscopy. Fluorination affects both, the amide and the hydrocarbon parts of the polymers. However, only the carbon atom next to the carbonyl is readily fluorinated. Chemical modification of the amide group is apparent in a large binding energy shift (+5 eV) of the N1s level and the appearance of a CO band at 1734 cm-1. It is concluded that the amide C-N bond is cleaved in the fluorination process and that COOH and NF2 end groups are formed. This conclusion is corroborated by the appearance of ester oxygen in the XPS and by the 19F NMR spectra of the volatile products that show fluorine signals chemically shifted about 200 ppm towards lower field as compared with the CHF environment. KW - Gasfluorierung KW - IR KW - XPS KW - AFM KW - NF2-Gruppe PY - 2004 UR - http://www.e-polymers.org SN - 1618-7229 IS - 8 SP - 1 EP - 16 PB - De Gruyter CY - [S.l.] AN - OPUS4-3425 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Fertigung und Charakterisierung von Kalibrierproben T2 - 1. Treffen im Verbundprojekt Entwicklung und Optimierung von Prüfmethoden zur quantitativen Bestimmung elastischer Eigenschaften in nanoskaligen Dimensionen mit Rastersondenmikroskopie, IZPF CY - Saarbrücken, Germany DA - 2002-09-04 PY - 2002 AN - OPUS4-6526 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Scanning Force Microscopy (SFM) with additional mechanical and electrical materials contrasts T2 - Seminar of the Department of Materials and Interfaces, Weizmann Institute of Science CY - Rehovot, Israel DA - 1997-02-16 PY - 1997 AN - OPUS4-6412 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Solomun, Tihomir A1 - Mix, Renate A1 - Sturm, Heinz T1 - Immobilization of silanized DNA on glass: influence of the silane tether on the DNA hybridization N2 - Two trifunctional (trimethoxy and triethoxy) and one difunctional (methyldimethoxy) 3-mercaptopropyl-alkoxysilanes were covalently tethered to thiolated DNA oligonucleotides in solution. After deposition as microarrays onto glass, the immobilized DNA probes were tested for hybridization ability by a florescence-based method. The results demonstrate a large enhancement in the fluorescence signal when the functionality of the silane tether is reduced from three to two. An XPS analyses revealed that this is not due to a higher DNA surface density. FTIR spectra of the spin-coated silanes showed that the trifunctional silanes form branched and cyclic siloxane moieties, whereas the difunctional silane generates predominantly short straight siloxane chains. Therefore, the propensity of trifunctional silanes to form more complex networks leads to conformations of the bound DNA which are less favorable for the specific interaction with the complementary strand. The data implicate that further significant improvements in the DNA hybridization ability are possible by adroit choice of the silane system. KW - Silanized DNA KW - DNA immobilization KW - DNA hybridization KW - Fluorescence imaging KW - FTIRS KW - XPS PY - 2010 DO - https://doi.org/10.1021/am100263t SN - 1944-8244 SN - 0013-936X SN - 1944-8252 VL - 2 IS - 8 SP - 2171 EP - 2174 PB - ACS Publ. CY - Washington, DC, USA AN - OPUS4-22614 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Trappe, Volker A1 - Hickmann, Stefan A1 - Sturm, Heinz T1 - Bestimmung des Zwischenfaserbruchversagens in textilverstärktem Glasfaserkunststoff mittels der Röntgenrefrationstopografie N2 - Moderne Leichtbaustrukturen (Luftfahrt, Eisenbahn, Automotive) aus Faserverbundwerkstoffen (FVW) sind hohen mechanischen und klimatischen Beanspruchungen ausgesetzt. Aussagen über die Lebensdauer und Funktionssicherheit der FVW-Bauteile können eher aus Untersuchungen der mikromechanischen Eigenschaften gewonnen werden als aus der globalen Festigkeit. Die Röntgenrefraktionstopografie ist ein Verfahren zur zerstörungsfreien Bestimmung von inneren Oberflächen in Werkstoffen. Angewendet auf FVW lassen sich Aussagen über die Faserorientierungen, die Fertigungsqualität sowie über Faser-Matrix-Ablösungen und Matrixrisse infolge mechanischer Beanspruchung gewinnen. Nachfolgend wird ein neues Verfahren zur Bestimmung des Zwischenfaserbruchversagens am komplexen Laminat vorgestellt. Hierbei wird das Röntgenrefraktionsverfahren "online“ bei Zug-Belastung der Probe angewendet. KW - Zerstörungsfreie Prüfung KW - Röntgenstreuung KW - Faserverbundwerkstoffe KW - Mikrorissbildung KW - Glasfaserverstärkter Kunststoff PY - 2008 SN - 0025-5300 VL - 50 IS - 10 SP - 615 EP - 622 PB - Hanser CY - München AN - OPUS4-18282 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -