TY - CONF A1 - Sturm, Heinz T1 - Bilayer polymer/oxide coating for electroluminescent organic semiconductors T2 - E-MRS 2011 Spring Meeting; IUMRS ICAM 20011 & E-MRS / MRS Bilateral Conference on Energy CY - Nice, France DA - 2011-05-09 PY - 2011 AN - OPUS4-23667 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sturm, Heinz A1 - Schulz, Eckhard T1 - Rasterkraftmikroskopie mit lokalem Leitfähigkeitskontrast zur Oberflächenanalyse von Kohlefaseroberflächen und plasmapolymerisierten dünnen Schichten PY - 1995 SN - 0340-3815 VL - 28 SP - 51 EP - 58 PB - Remy CY - Münster, Westf. AN - OPUS4-6847 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Leitfähigkeitskontrast auf Kohlefaseroberflächen und atomare Auslösung auf HOPG T2 - 6th International Workshop "Frontiers in SPM" CY - Saarbrücken, Germany DA - 1995-09-20 PY - 1995 AN - OPUS4-6387 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Dynamic Plowing Lithography of Polymer Surfaces T2 - Workshop "Scanning Probe Microscopy in the New Millennium" CY - Faure, South Africa DA - 2001-02-26 PY - 2001 AN - OPUS4-7512 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kovalev, Alexander A1 - Sturm, Heinz T1 - In situ direct observation of adsorption and desorption on a single crystal of 2,4,6-trinitrophenol (TNP) N2 - For the first time, we report the direct observation of the nanoscale adsorption and desorption of 2,4,6-trinitrophenol (TNP) molecules on the crystal surface during atomic force microscopy scanning. Our results reveal the position instability of TNP molecules at the border of molecular layers under normal ambient conditions. The observed phenomena are of great interest for exploring the origin of hot-spot generation on the surface of energetic materials. On the basis of the explored properties of TNP crystal, a plausible mechanism of hot-spot formation upon weak initiation at the nanoscale is proposed. KW - Nanoscale adsorption and desorption KW - 2,4,6-trinitrophenol (TNP) KW - Instability of TNP KW - Mechanism of hot-spot formation PY - 2012 DO - https://doi.org/10.1021/cg300366m SN - 1528-7483 VL - 12 IS - 7 SP - 3557 EP - 3564 PB - American Chemical Society CY - Washington, DC, USA AN - OPUS4-26734 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sturm, Heinz A1 - Schartel, Bernhard A1 - Weiß, André A1 - Braun, Ulrike T1 - SEM/EDX: Advanced investigation of structured fire residues and residue formation N2 - Heterogeneous, gradual or structured morphology of fire residues plays an important role in fire retardancy of polymers. A scanning electron microscope with an attached energy dispersive X-ray spectrometer (SEM/EDX) is highlighted as a powerful tool for the advanced characterization of such complex fire residues, since it offers high resolution in combination with both good depth of field and analysis of chemical composition. Two examples are presented: First, comprehensive SEM/EDX investigation on a complex structured fire residue of glass fibre reinforced polyamide 6,6 (PA 66-GF) flame retarded by diethylaluminium phosphinate, melamine polyphosphate and some zinc borate. A multilayered surface crust (thickness ~ 24 µm) covers a rather hollow area stabilized by GF glued together. The resulting efficient thermal insulation results in self-extinguishing before pyrolysis is completed, even under forced-flaming combustion. Second, sophisticated, quasi online SEM/EDX imaging of the formation of residual protection layer in layered silicate epoxy resin nanocomposites (LSEC). Burning specimens were quenched in liquid nitrogen for subsequent analyses. Different zones were distinguished in the condensed phase characterized by distinct processes such as melting and ablation of organic material, as well as agglomeration, depletion, exfoliation and reorientation of the LS. KW - Fire residue KW - SEM/EDX KW - Fire retardancy KW - PA 66 KW - Layered silicate KW - Diethylaluminium phosphinate PY - 2012 DO - https://doi.org/10.1016/j.polymertesting.2012.03.005 SN - 0142-9418 VL - 31 IS - 5 SP - 606 EP - 619 PB - Elsevier CY - Amsterdam AN - OPUS4-25802 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sturm, Heinz T1 - Scanning force microscopy experiments probing micromechanical properties on polymer surfaces using harmonically modulated friction techniques - I. Principles of operation N2 - Applying a high-frequency lateral vibration between the sample surface and the tip of a scanning force microscope (SFM), a harmonically modulated lateral (friction) force image can be obtained using lock-in techniques. The principles of operation are explained, in particular the dramatic decrease of image artefacts generally caused by topography cross-talk and laser beam interference. Flat interfaces between the two immiscible polymers, poly(methyl methacrylate) (PMMA) and polystyrene (PS), are prepared on a sodium chloride single crystal from the melt. These samples are used to evaluate the appropriate model for the tip-sample interaction geometry. The relationship between frictional and normal force does not follow Amonton's law. This shows that a single-asperity interaction between the tip and sample surface can be considered. Using the new technique, local measurements of shear strength and Young's modulus can be performed. KW - Atomic-scale friction KW - Nanotribology KW - Tip PY - 1999 DO - https://doi.org/10.1002/masy.19991470124 SN - 1022-1360 SN - 0258-0322 SN - 1521-3900 VL - 147 SP - 249 EP - 258 PB - Wiley-VCH Verl. CY - Weinheim, Germany AN - OPUS4-6855 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Sturm, Heinz T1 - Friction-induced explosive reactions N2 - The motivation to examine the influence of friction on surfaces of energetic materials (EM) has diverse backgrounds. On the one hand the very old hot spot theory predicts, that the size of such hot spot could be in the range of a molecule. The initiation of an EM could start by mechanical excitation, i.e. friction, and continues driven by an exothermal chemical reaction. Following such phenomena on the molecular scale with an imaging method such as AFM should enable us to separate several steps of ignition, if there are any. The experiments showed that HMX mainly undergoes a plastic deformation without further consequences. TNP however showed self healing in the wear track after scratching and simultaneously the destruction of a crystal edge outside the wear track. Additionally nanoparticles appear, tribologists call this "third body formation", which are proven to have a different chemical composition as the original TNP. The self healing effect on the surface is verified with experiments on self diffusion of TNP molecules to and fro the free edges of the crystal. The conclusion is that the formation of a hot spot can be shown to consist of several subsequent steps, separated temporally and locally. The goal to excite the thermal decomposition of a whole TNP crystal (nanoexplosion) was yet not reached due to unfavourable conditions related to thermal conductivity and build-up of pressure. T2 - Role of Third Bodies in Tribology, Colloquium of 5.1 CY - BAM, Berlin, Germany DA - 09.06.2016 KW - AFM KW - Energetic material KW - Hot spot KW - Friction PY - 2016 AN - OPUS4-36433 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dümichen, Erik A1 - Braun, Ulrike A1 - Sturm, Heinz A1 - Kraemer, R. A1 - Deglmann, P. A1 - Gaan, S. A1 - Senz, R. T1 - A new molecular understanding of the thermal degradation of PA 66 doped with metal oxides: Experiment and computation N2 - The thermal molecular degradation of polyamide 66 (PA 66) doped with (partially supported) metal oxide particles (Fe2O3, ZnO, Al2O3) was investigated qualitatively and quantitatively using common analysis techniques like thermogravimetry coupled with IR-spectroscopic evolved gas analysis (TGA-FTIR). Using pyrolysis coupled with gas chromatography mass spectrometry (Py-GC-MS), qualitative conclusions were drawn about the complex hydrocarbon products. However, the combination of TGA with solid-phase extraction, followed by thermal desorption gas chromatography mass spectrometry (TED-GC-MS), allows qualitative and even semi-quantitative conclusions about the decomposition pathway of PA 66 in the presence of various metal oxide particles. The investigations under inert conditions showed that the presence of metal particles increases the rate of decarboxylation and deamination reactions, as well as the formation rate of cyclopentanone and pyridine derivatives. These species are a consequence of various condensation reactions. The condensation reactions release a large amount of water, thus triggering the hydrolysis of PA 66. Molecular thermal degradation mechanisms were developed for the main decomposition as well as for the condensation reactions and supported by quantum chemical calculations. The catalytic effect of the metal oxides in PA 66 increases in the following order: PA 66 = PA 66 – Al2O3 < PA 66 – Fe2O3 < PA 66 – ZnO. KW - PA 66 KW - Metal oxide particles KW - Thermal degradation KW - Solid-phase extraction KW - Molecular modeling PY - 2015 DO - https://doi.org/10.1016/j.polymdegradstab.2015.07.011 SN - 0141-3910 SN - 1873-2321 VL - 120 SP - 340 EP - 356 PB - Elsevier Ltd. CY - London AN - OPUS4-33806 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -