TY - JOUR A1 - Braun, Ulrike A1 - Lorenz, Edelgard A1 - Weimann, Christiane A1 - Sturm, Heinz A1 - Karimov, I. A1 - Ettl, J. A1 - Meier, R. A1 - Wohlgemuth, W. A. A1 - Berger, H. A1 - Wildgruber, M. T1 - Mechanic and surface properties of central-venous port catheters after removal: A comparison of polyurethane and Silicon rubber materials N2 - Central venous port devices made of two different polymeric materials, thermoplastic polyurethane (TPU)and silicone rubber (SiR), were compared due their material properties. Both naïve catheters as well as catheters after removal from patients were investigated. In lab experiments the influence of various chemo-therapeutic solutions on material properties was investigated, where as the samples after removal were compared according to the implanted time inpatient. The macroscopic,mechanical performance was assessed with dynamic, specially adapted tests for elasticity. The degradation status of the materials was determined with common tools of polymer characterisation, such as infrared spectroscopy, molecular weight measurements and various methods of thermal analysis. The surface morphology was an alysed using scanning electron microscopy. A correlation between material properties and clinical performance was proposed. The surface morphology and chemical composition of the polyurethane catheter materials can potentially result in increased susceptibility of the catheter to bloodstream infections and thrombotic complications. The higher mechanic failure,especially with increasing implantation time of the silicone catheters is related to the lower mechanical performance compared to the polyurethane material as well as loss of barium sulphate filler particles near the surface of the catheter. This results in preformed microscopic notches, which act as predetermined sites of fracture. KW - Thermoplastic polyurethane (TPU) KW - Silicone rubber (SiR) KW - Catheters KW - Central venous access port KW - Complication KW - Structure propertyrelationship KW - Mechanical testing PY - 2016 DO - https://doi.org/10.1016/j.jmbbm.2016.08.002 SN - 1751-6161 SN - 1878-0180 VL - 64 SP - 281 EP - 291 PB - Elsevier Ltd. AN - OPUS4-37178 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Munz, Martin A1 - Sturm, Heinz A1 - Schulz, Eckhard A1 - Hinrichsen, G. T1 - The scanning force microscope as a tool for the detection of local mechanical properties within the interphase of fibre reinforced polymers N2 - Scanning force microscopy (SFM) has been used to assess the local mechanical properties of fibre-reinforced polymers. Using a sinusoidal displacement modulation (DM) and lock-in technique the method allows to characterize local viscoelastic properties with a high lateral resolution. The simultaneous measurement of the local electrical conductivity is proposed which facilitates the interpretation of the mechanical data. The investigation of cross-sections perpendicular to the axis of carbon fibres embedded in PPS delivers some information about the change in local stiffness within the interfacial region. As a first approach, assuming a single-exponential decrease in local stiffness along a radial line from fibre to polymer we find characteristic decay lengths which are distributed in a range between 20 and 80nm. Further, a modified DM-mode is proposed which is expected to provide a contrast enhancement of the signal which is related to local stiffness. This can be achieved by installing an additional feedback loop which keeps constant the amplitude of dynamic indentation (CDI-mode). KW - Polymer-matrix composites (PMC´s) KW - Interface/interphase KW - SFM/AFM KW - Surface properties KW - Nondestructive testing PY - 1998 DO - https://doi.org/10.1016/S1359-835X(98)00077-3 SN - 1359-835X VL - 29 SP - 1251 EP - 1259 PB - Elsevier CY - Oxford AN - OPUS4-1294 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Sturm, Heinz A1 - Geuss, Markus A1 - Schulz, Eckhard ED - Konsta, A. T1 - Scanning force microscopy investigations on electroactive polymer films N2 - The authors present investigations on a PVDF (polyvinylidenefluoride) film supplied with top and bottom Au electrodes, which is analysed using a SFM and a contactless optical sensor to measure the sample strain with respect to applied fields. T2 - 10th IEEE International Symposium on Electrets (ISE) CY - Delphi, Greece DA - 1999-09-22 PY - 1999 SN - 0-7803-5025-1 DO - https://doi.org/10.1109/ISE.1999.832086 SP - 465 EP - 468 PB - IEEE Operations Center CY - Piscataway, NJ AN - OPUS4-6862 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - AFM cantilevers as mechanical sensors T2 - Nano-Seminar am NanoSYD-Institut der süddänischen Universität in Sonderborg CY - Sonderborg, Denmark DA - 2008-12-02 PY - 2008 AN - OPUS4-18266 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Solomun, Tihomir A1 - Schimanski, A. A1 - Sturm, Heinz A1 - Illenberger, E. T1 - Reactions of amide group with fluorine as revealed with surface analytics N2 - Thin polyamide-6 films were exposed to fluorine gas and analysed with photoelectron and infrared spectroscopies. Fluorine cleaves the amide C–N bond resulting in the formation of the –COOH and –NF2 terminal groups. This is evident from large shifts in the N1s binding energy (+5 eV) and C=O stretching frequency (~80 cm-1), appearance of ester oxygen in the XPS spectra, as well as by the 19F nmr spectra of volatile products consistent with a terminal NF2 group. KW - Gasfluorierung KW - Polyamid-6 KW - XPS KW - IR KW - -COOH und NF2-Gruppen PY - 2004 UR - http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232004%23996109995%23499295%23FLA%23&_cdi=5231&_pubType=J&_auth=y&_acct=C000049503&_version=1&_urlVersion=0&_userid=963821&md5=baea8e0df63660c666921ef377c00e40 SN - 0009-2614 SN - 1873-4448 VL - 378 SP - 312 EP - 316 PB - North-Holland Publ. Co. CY - Amsterdam AN - OPUS4-3439 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Solomun, Tihomir A1 - Seitz, H. A1 - Sturm, Heinz T1 - DNA damage by low-energy electron impact: dependence on guanine content KW - DNA oligonucleotide KW - Low energy electrons KW - Secondary electrons KW - Damage KW - Guanine content PY - 2009 DO - https://doi.org/10.1021/jp905263x SN - 1520-6106 SN - 1089-5647 VL - 113 IS - 34 SP - 11557 EP - 11559 PB - Soc. CY - Washington, DC AN - OPUS4-20704 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Nichtlinearität und Hysterese von AFM-Piezos T2 - 24th Intern. TopoMetrix-Workshop: Aktuelle Entwicklungen in der Nanotechnologie und Rastersondenmikroskopie, Humboldt-Universität CY - Berlin, Germany DA - 1998-03-12 PY - 1998 AN - OPUS4-6462 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Lithography on Polymers using a Scanning Force Microscope (SFM) and a Environmental Scanning Electron Microscope (ESEM) T2 - Seminar International PhD Program CY - Berlin, Germany DA - 2004-04-30 PY - 2004 AN - OPUS4-3504 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Rastersondenverfahren T2 - BAM, DGM Fachausschuss "Gefüge und Eigenschaften von Polymerwerkstoffen" CY - Berlin, Germany DA - 2003-12-05 PY - 2003 AN - OPUS4-4099 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Dynamics of phase transitions in polymer thin films upon single femtosecond laser pulse irradiation T2 - Second International Conference on Photo-Induced Phase Transitions Cooperative, non-linear and functional properties CY - Rennes, France DA - 2005-05-24 PY - 2005 AN - OPUS4-7430 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sturm, Heinz A1 - Schulz, Eckhard T1 - Atomic force microscopy with simultaneous AC conductivity contrast for the analysis of carbon fibre surfaces KW - Carbon fibre KW - Surface analysis KW - Conductivity microscopy KW - Scanning force microscopy KW - Scanning tunneling microscopy KW - Fiber surfaces PY - 1996 SN - 1359-835X VL - 27 IS - 9 SP - 677 EP - 684 PB - Elsevier CY - Oxford AN - OPUS4-6849 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Munz, Martin A1 - Sturm, Heinz A1 - Schulz, Eckhard T1 - Zuverlässigkeit von Polymer-Werkstoffen - Interphasen nanoskopisch betrachtet T2 - 3. Workshop "Rasterkraftmikroskopie in der Werkstoffwissenschaft" CY - Berlin, BAM, Deutschland DA - 2002-02-28 PY - 2002 SP - 14 AN - OPUS4-1831 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Lithographie, Manipulation und Analyse in ESEM und AFM T2 - Evaluierungsmeeting eines zukünftigen DFG-Forscherverbundes zum Thema "Nanoröhren und -drähte" CY - Halle (Saale), Germany DA - 2003-01-17 PY - 2003 AN - OPUS4-2915 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Atomic force microscopy with simultaneous AC conductivity contrast for the analysis of carbon fibre surfaces T2 - IPCM (Interfacial Phenomena in Composite Materials) CY - Eindhoven, Netherlands DA - 1995-09-10 PY - 1995 AN - OPUS4-6385 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dümichen, Erik A1 - Javdanitehran, M. A1 - Erdmann, Maren A1 - Trappe, Volker A1 - Sturm, Heinz A1 - Braun, Ulrike A1 - Ziegmann, G. T1 - Analyzing the network formation and curing kinetics of epoxy resins by in situ near-infrared measurements with variable heating rates N2 - Near-infrared spectroscopy (NIR) turned out to be well suited for analyzing the degree of cure for epoxy systems. In contrast to dynamic scanning calorimetry (DSC), where the released heat of reaction determines the degree of epoxy conversion indirectly, NIR spectroscopy is able to determine the conversion directly by analyzing structural changes. Therefore, a new heatable NIR cell was equipped with an integrated thermocouple, which enables the real sample temperature to be controlled and monitored in situ during epoxy curing. Dynamic scans at different heating rates were used for kinetic modelling, to define kinetic parameters and to predict real curing processes. The kinetic models and their parameters were validated with an isothermal and a more complex multi-step curing scenario. Two available commercial epoxy systems based on DGEBA were used with an anhydride and with an amine hardener. NIR results were compared with DSC data. The simulated conversion predicted with a model fitted on the basis of NIR and DSC dynamic scans showed good agreement with the conversion measured in the isothermal curing validation test. Due to the proven reliability of NIR in measuring the reaction progress of curing, it can be considered a versatile measurement system for in situ monitoring of component production in the automotive, aerospace and wind energy sectors. KW - Epoxy resins KW - Curing kinetics KW - Near-infrared spectroscopy KW - DSC PY - 2015 DO - https://doi.org/10.1016/j.tca.2015.08.008 SN - 0040-6031 SN - 1872-762X VL - 616 SP - 49 EP - 60 PB - Elsevier CY - Amsterdam AN - OPUS4-34187 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz A1 - Kovalev, Alexander T1 - Nanotribologie an explosionsfähigen Kristallen N2 - Energetische Materialien enthalten gespeicherte chemische Energie. Diese potentielle Energie kann bei Zündung schlagartig als Strahlungsenergie und Druckerhöhung freigesetzt werden. Nanoskalige Komponenten erhöhen zusätzlich die innere Energie des Materials um den Beitrag der Oberflächenenergie und verbessern die chemische Umsetzung durch bessere Durchmischung. Die hot-spot-Theorie zur Zündung von Explosivstoffen kombiniert mechanische Stimulation und einer dabei zu erreichenden Schwellwert-Energie mit der Temperatur. Wird die Energie zum exothermen Bindungsbruch etwa beim Reibvorgang erreicht entsteht auf der molekularen Skala ein hot-spot. Der Stoff explodiert, wenn der hot-spot ausreichend lange besteht, sich verstärkt und nicht durch Energiedissipation (Festkörperschallausbreitung, Wärmediffusion) verzehrt wird. Rasterkraftmikroskopie (AFM – atomic force microscopy) dient nicht nur zur bildgebenden Vermessung der Topographie und der mechanischen Eigenschaften, sondern kann auch zur gezielten Veränderung der Oberflächen verwendet werden. Solche lithographischen Verfahren bedienen sich im AFM-Kontaktmodus (Scratching Lithography) direkt der Reibung, im hochfrequenten intermittierenden Kontaktverfahren realisiert man einen vibrierenden Kontaktes (Dynamic Plowing Lithography), der beim Eindringen in eigenen Indentationseindruck reibt. In beiden Fällen überträgt man durch Kombination einer Scherbewegung mit einer Variation des Kontaktdrucks Energie auf die Oberfläche, was nachweislich zum chemischen Bindungsbruch z.B. auf Polymeroberflächen führt. Zwei kristalline Explosivstoffe werden untersucht und sowohl dissipative Effekte als auch die Generierung eines hot-spots demonstriert. N2 - Using nanoscale components increase the internal energy by the contribution of surface energy and improve the progress of the chemical reaction. The hot-spot theory of ignition describes the conversion of mechanical energy of friction or impact into heat, leading to exothermal decomposition of the explosive. Thus, it is evident that ignition should be studied on the nanoscale and atomic force microscopy (AFM) provides one of the best solutions to study such behavior. AFM, often used to map a topography image and local mechanical properties on a surface, can also be utilized for carrying lithography, namely scratching lithography or dynamic plowing lithography. In both cases shear stress combined with a variation of contact pressure transfers sufficient energy into the surface to break chemical bonds. Two crystalline explosives are investigated and dissipative processes as well as hot-spot generation are described. During the nanotribological test, the in-situ restructuring of molecular layers under ambient conditions was observed and recorded. T2 - 54. Tribologie-Fachtagung - Reibung, Schmierung und Verschleiß - Forschung und praktische Anwendungen CY - Göttingen, Germany DA - 30.09.2013 KW - Energetische Kristalle KW - Hot spot Theorie PY - 2013 SN - 978-3-00-022603-8 IS - Paper 39 SP - 39/1 EP - 39/11 AN - OPUS4-29457 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Der dynamische Reibkontrast als eine Methode zur Charakterisierung von Polymeroberflächen in der Rasterkraftmikroskopie T2 - Frühjahrstagung der DPG, FA: Polymerphysik CY - Münster, Germany DA - 1997-03-17 PY - 1997 AN - OPUS4-6415 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heyde, M. A1 - Sturm, Heinz A1 - Rademann, K. T1 - New application for the calibration of scanning probe microscopy piezos KW - Scanning probe microscope KW - Piezoelectric translator KW - Calibration KW - Height Calibration KW - Force-Microscopy PY - 1999 SN - 0142-2421 SN - 1096-9918 VL - 27 IS - 5-6 SP - 291 EP - 295 PB - Wiley CY - Chichester AN - OPUS4-6858 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Nanoröhren und -drähte - Lithographie, Manipulation und Analyse in ESEM und AFM T2 - Vorbereitungstreffen zum DFG Schwerpunkt "Nanodrähte und Nanoröhren" CY - Halle (Saale), Deutschland DA - 2003-01-17 PY - 2003 CY - Halle AN - OPUS4-2130 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Studies of wear on materials by SPM T2 - First Workshop on Scanning Probe Microscopy CY - São Carlos, Brazil DA - 1997-10-10 PY - 1997 AN - OPUS4-6421 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fichera, Mario Augusto A1 - Braun, Ulrike A1 - Schartel, Bernhard A1 - Sturm, Heinz A1 - Knoll, Uta A1 - Jäger, Christian T1 - Solid-state NMR investigations of the pyrolysis and thermo-oxidative decomposition products of a polystyrene/red phosphorus/magnesium hydroxide system N2 - Thermal, thermo-oxidative and fire residues of high impact polystyrene/magnesium hydroxide/red phosphorus (HIPS/Mg(OH)2/Pr) are investigated by solid-state NMR and compared with the results for the binary subsystem Mg(OH)2/Pr. The influences of oxygen, nitrogen and temperature are discussed. For a thermal decomposition and pyrolysis during combustion, the main pyrolysis of HIPS takes place while the remaining residue is a rather intact polymer, with a major share of the embedded Pr still present. Subsequently, mainly amorphous phosphates and a slight amount of crystalline Mg3(PO4)2 and Mg2P2O7 are formed at the highest temperatures. Only with increasing mass loss does the remaining polystyrene structure decompose and graphitic structures occur. The influence of oxygen on the decomposition mechanism is most obvious for the binary system Mg(OH)2/Pr. Pr vanishes more rapidly and crystalline, oxygen-rich magnesium phosphates are formed. In HIPS/Mg(OH)2/Pr systems the polymer acts as a barrier to reaction by the embedded particles, so that major characteristics of an anaerobic decomposition are found. Significant amounts of phosphorus are retained in the condensed phase through a reaction of Pr with Mg(OH)2 to mostly amorphous phosphates. This formation of amorphous inorganic magnesium phosphates can act as an additional physical barrier. This study outlines some advanced approaches for controlling the condensed-phase mechanisms of phosphorus and underlines that solid-state NMR is a most powerful tool for investigating the organic and inorganic residues. KW - HIPS KW - Red phosphorus KW - Magnesium hydroxide KW - Solid-state NMR KW - Flame retarded polymers PY - 2007 SN - 0165-2370 SN - 1873-250X VL - 78 IS - 2 SP - 378 EP - 386 PB - Elsevier CY - Amsterdam AN - OPUS4-14517 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -