TY - JOUR A1 - Kulla, Hannes A1 - Wilke, Manuel A1 - Fischer, Franziska A1 - Röllig, Mathias A1 - Maierhofer, Christiane A1 - Emmerling, Franziska T1 - Warming up for mechanosynthesis – temperature development in ball mills during synthesis N2 - We present a first direct measurement of the temperature during milling combined with in situ Raman spectroscopy monitoring. The data reveal a low temperature increase due to the mechanical impact and clear temperature increases as a consequence of the reaction heat. Based on the data, temperature rises as postulated in the magma plasma and hot spot theory can be excluded for soft matter milling syntheses. KW - Thermography KW - Milling KW - Mechanochemistry KW - Soft matter PY - 2017 DO - https://doi.org/10.1039/c6cc08950j SN - 1364-548X SN - 1359-7345 SN - 0009-241X VL - 53 IS - 10 SP - 1664 EP - 1667 AN - OPUS4-39251 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhou, Peng A1 - Ogle, Kevin A1 - Erning, Johann Wilhelm A1 - Hutchinson, Michael John A1 - Scully, John T1 - An in situ kinetic study of brass dezincification and corrosion N2 - The kinetics of the anodic dissolution of brass (CuZn42 and CuZn21Si3P) in synthetic tap water were investigated by atomic emission spectroelectrochemistry. Elemental Cu and Zn dissolution rates were measured in situ and in real time during galvanostatic dissolution. A complete mass/charge balance for the system yielded, as a function of applied current and a function of time, the quantity of Cu in the dezincification layer and the quantity of Cu and Zn in the oxide layer. In this way, a complete kinetic characterization of the fundamental chemical processes occurring during dezincification was realized for the first time. The oxide layer was composed primarily of Cu2O as indicated by grazing incidence XRD and Raman analysis. The soluble Cu oxidation product was determined to be Cu(II) by a mass/charge balance. Zn was oxidized to soluble Zn(II) leaving behind a trivial amount of solid Zn corrosion product on the surface. The kinetic analysis depicts a two-stage dissolution process of dezincification: a first stage of a rapid growth of the dezincified layer and a second stage where the growth of dezincified layer was much slower. The Cu2O layer grows continually during the exposure. KW - Dezincification KW - Spectroelectrochemistry KW - Brass PY - 2017 DO - https://doi.org/10.1016/j.electacta.2017.01.078 SN - 0013-4686 SN - 1873-3859 VL - 229 SP - 141 EP - 154 PB - Elsevier AN - OPUS4-39164 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yilmaz, M. A1 - Wollschläger, Nicole A1 - Esfahani, M. N. A1 - Österle, Werner A1 - Leblebici, Y. A1 - Alaca, B. E. T1 - Superplastic behavior of silica nanowires obtained by direct patterning of silsesquioxane-based precursors N2 - Silica nanowires spanning 10 μm-deep trenches are fabricated from different types of silsesquioxane-based precursors by direct e-beam patterning on silicon followed by release through deep reactive ion etching. Nanowire aspect ratios as large as 150 are achieved with a critical dimension of about 50 nm and nearly rectangular cross-sections. In situ bending tests are carried out inside a scanning electron microscope, where the etch depth of 10 mm provides sufficient space for deformation. Silica NWs are indeed observed to exhibit superplastic behavior without fracture with deflections reaching the full etch depth, about two orders of magnitude larger than the nanowire thickness. A large-deformation elastic bending model is utilized for predicting the deviation from the elastic behavior. The results of forty different tests indicate a critical stress level of 0.1–0.4 GPa for the onset of plasticity. The study hints at the possibility of fabricating silica nanowires in a monolithic Fashion through direct e-beam patterning of silsesquioxane-based resins. The fabrication technology is compatible with semiconductor manufacturing and provides silica nanowires with a very good structural integrity. KW - Silica nanowires KW - HSQ KW - Superplasticity KW - In situ bending tests PY - 2017 DO - https://doi.org/10.1088/1361-6528/aa5b80 SN - 0957-4484 SN - 1361-6528 VL - 28 IS - 11 SP - Article 115302, 1 EP - 10 AN - OPUS4-39166 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yilmaz, M. A1 - Kilinc, Y. A1 - Nadar, G. A1 - Tasdemir, Z. A1 - Wollschläger, Nicole A1 - Österle, Werner A1 - Leblebici, Y. A1 - Alaca, B. E. T1 - Top-down technique for scaling to nano in silicon MEMS N2 - Nanoscale building blocks impart added functionalities to microelectromechanical systems (MEMS). The integration of silicon nanowires with MEMS-based sensors leading to miniaturization with improved sensitivity and higher noise immunity is one example highlighting the advantages of this multiscale approach. The accelerated pace of research in this area gives rise to an urgent need for batch-compatible solutions for scaling to nano. To address this challenge, a monolithic fabrication approach of silicon nanowires with 10-lm-thick silicon-on-insulator (SOI) MEMS is developed in this work. A two-step Si etching approach is adopted, where the first step creates a shallow surface protrusion and the second step releases it in the form of a nanowire. It is during this second deep etching step that MEMS—with at least a 2-order-of-magnitude scale difference - is formed as well. The technique provides a pathway for preserving the lithographic resolution and transforming it into a very high mechanical precision in the assembly of micro- and nanoscales with an extreme topography. Validation of the success of integration is carried out via in situ actuation of MEMS inside an electron microscope loading the nanowire up to its fracture. The technique yields nanowires on the top surface of MEMS, thereby providing ease of access for the purposes of carrying out surface processes such as doping and contact formation as well as in situ observation. As the first study demonstrating such monolithic integration in thick SOI, the work presents a pathway for scaling down to nano for future MEMS combining multiple scales. KW - Nanowires KW - Silicon KW - Top-down KW - MEMS PY - 2017 DO - https://doi.org/10.1116/1.4978047 SN - 1071-1023 VL - 35 IS - 2 SP - 022001-1 EP - 022001-7 PB - America Vacuum Society AN - OPUS4-39370 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Müller, Jan P. A1 - Götschel, S. A1 - Maierhofer, Christiane A1 - Weiser, M. T1 - Determining the Material Parameters for the Reconstruction of Defects in Carbon Fiber Reinforced Polymers from Data Measured by Flash Thermography N2 - Flash thermography is a fast and reliable non-destructive testing method for the investigation of defects in carbon fiber reinforced polymer (CFRP) materials. In this paper numerical simulations of transient thermography data are presented, calculated for a quasi-isotropic flat bottom hole sample. They are compared to experimental data. These simulations are one important step towards the quantitative reconstruction of a flaw by assessing thermographic data. The applied numerical model is based on the finite-element method, extended by a semi-analytical treatment of the boundary of the sample, which is heated by the flash light. A crucial part for a reliable numerical model is the prior determination of the material parameters of the specimen as well as of the experimental parameters of the set-up. The material parameters in plane and in depth diffusivity are measured using laser line excitation. In addition, the absorption and heat transfer process of the first layers is investigated using an IR microscopic lens. The performance of the two distinct components of CFRP during heating – epoxy resin and carbon fibers – is examined. Finally, the material parameters are optimized by variation and comparison of the simulation results to the experimental data. The optimized parameters are compared to the measured ones and further methods to ensure precise material parameter measurements are discussed. T2 - 43rd Review of Progress in Quantitative Nondestructive Evaluation CY - Atlanta, GA, USA DA - 17.07.2016 KW - Aktive Thermografie KW - Thermische Diffusivität KW - Zerstörungsfreie Prüfung KW - Kohlenstofffaserverstärkter Kunststoff KW - CFK KW - Active thermography KW - Thermal diffusivity KW - Non-Destructive testing KW - Carbon fiber reinforced polymer KW - CFRP PY - 2017 SN - 978-0-7354-1474-7 DO - https://doi.org/10.1063/1.4974671 SN - 0094-243X VL - 1806 IS - 1 SP - UNSP 100006-1 EP - 11 PB - AIP Publishing CY - Melville, NY, USA AN - OPUS4-39332 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Madkour, Sherif A1 - Szymoniak, Paulina A1 - Heídari, M. A1 - von Klitzing, R. A1 - Schönhals, Andreas T1 - Unveiling the dynamics of self-assembled layers of thin films of poly(vinyl methyl ether) (PVME) by nanosized relaxation spectroscopy N2 - A combination of nanosized dielectric relaxation (BDS) and thermal spectroscopy (SHS) was utilized to characterize the dynamics of thin films of Poly(vinyl methyl ether) (PVME) (thicknesses: 7 nm – 160 nm). For the BDS measurements, a recently designed nano-structured electrode system is employed. A thin film is spin-coated on an ultra-flat highly conductive silicon wafer serving as the bottom electrode. As top electrode, a highly conductive wafer with non-conducting nanostructured SiO2 nano-spacers with heights of 35 nm or 70 nm is assembled on the bottom electrode. This procedure results in thin supported films with a free polymer/air interface. The BDS measurements show two relaxation processes, which are analyzed unambiguously for thicknesses smaller than 50 nm. The relaxation rates of both processes have different temperature dependencies. One process coincidences in its position and temperature dependence with the glassy dynamics of bulk PVME and is ascribed to the dynamic glass transition of a bulk-like layer in the middle of the film. The relaxation rates were found to be thickness independent as confirmed by SHS. Unexpectedly, the relaxation rates of the second process obey an Arrhenius-like temperature dependence. This process was not observed by SHS and was related to the constrained fluctuations in a layer, which is irreversibly adsorbed at the substrate with a heterogeneous structure. Its molecular fluctuations undergo a confinement effect resulting in the localization of the segmental dynamics. To our knowledge, this is the first report on the molecular dynamics of an adsorbed layer in thin films. KW - Broadband dielectric spectroscopy KW - AC-nanochip calorimetry KW - Nanostructured capacitors KW - Thin films PY - 2017 UR - http://pubs.acs.org/doi/pdf/10.1021/acsami.6b14404 DO - https://doi.org/10.1021/acsami.6b14404 SN - 1944-8244 VL - 9 IS - 8 SP - 7535 EP - 7546 PB - ACS Publications CY - Washington DC AN - OPUS4-39291 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fischer, Daniel A1 - Hertwig, Andreas A1 - Beck, Uwe A1 - Lohse, V. A1 - Negendank, D. A1 - Kormunda, M. A1 - Esser, N. T1 - Thin SnOx films for surface plasmon resonance enhanced ellipsometric gas sensing (SPREE) N2 - Background: Gas sensors are very important in several fields like gas monitoring, safety and environmental applications. In this approach, a new gas sensing concept is investigated which combines the powerful adsorption probability of metal oxide conductive sensors (MOS) with an optical ellipsometric readout. This concept Shows promising results to solve the problems of cross sensitivity of the MOS concept. Results: Undoped tin oxide (SnOx) and iron doped tin oxide (Fe:SnOx) thin add-on films were prepared by magnetron sputtering on the top of the actual surface plasmon resonance (SPR) sensing gold layer. The films were tested for their sensitivity to several gas species in the surface plasmon resonance enhanced (SPREE) gas measurement. It was found that the undoped tin oxide (SnOx) shows higher sensitivities to propane (C3H8) then to carbon monoxide (CO). By using Fe:SnOx, this relation is inverted. This behavior was explained by a change of the amount of binding sites for CO in the layer due to this iron doping. For hydrogen (H2) no such relation was found but the sensing ability was identical for both layer materials. This observation was related to a different sensing mechanism for H2 which is driven by the Diffusion into the layer instead of adsorption on the surface. Conclusion: The gas sensing selectivity can be enhanced by tuning the properties of the thin film overcoating. A relation of the binding sites in the doped and undoped SnOx films and the gas sensing abilities for CO and C3H8 was found. This could open the path for optimized gas sensing devices with different coated SPREE sensors. KW - Doped tin oxide KW - Ellipsometry KW - Gas sensing KW - Surface plasmon KW - Resonance KW - Thin films KW - Transparent conductive oxides PY - 2017 DO - https://doi.org/10.3762/bjnano.8.56 SN - 2190-4286 VL - 8 SP - 522 EP - 529 AN - OPUS4-39391 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Martins, M. S. S. A1 - Schartel, Bernhard A1 - Magalhães, F. D. A1 - Pereira, C. M. C. T1 - The effect of traditional flame retardants, nanoclays and carbon nanotubes in the fire performance of epoxy resin composites N2 - The effectiveness of distinct fillers, from micro to nano-size scaled, on the fire behaviour of an epoxy resin and its carbon fibre reinforced composites was assessed by cone calorimetry. The performance was compared not only regarding the reaction to fire performance, but also in terms of thermal stability, glass transition temperature and microstructure. Regarding the fire reaction behaviour of nanofilled epoxy resin, anionic nanoclays and thermally oxidized carbon nanotubes showed the best results, in agreement with more compact chars formed on the surface of the burning polymer. For carbon fibre reinforced composite plates, the cone calorimeter results of modified resin samples did not show significant improvements on the heat release rate curves. Poorly dispersed fillers in the resin additionally caused reductions on the glass transition temperature of the composite materials. KW - Epoxy resin KW - Carbon fibre reinforced composite KW - Nanoclays KW - Carbon nanotubes KW - Flame retardants PY - 2017 DO - https://doi.org/10.1002/fam.2370 SN - 1099-1018 SN - 0308-0501 VL - 41 IS - 2 SP - 111 EP - 130 PB - Wiley & Sons, Ltd. AN - OPUS4-39085 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Leng, Jing A1 - Kang, N. A1 - Wang, D.-Y. A1 - Wurm, Andreas A1 - Schick, C. A1 - Schönhals, Andreas T1 - Crystallization behavior of nanocomposites based on poly(L-lactide) and MgAl layered double hydroxides - Unbiased determination of the rigid amorphous phases due to the crystals and the nanofiller N2 - Semicrystalline polymers have to be described by a three phase model consisting of a mobile amorphous (MAF), a crystalline (CF), and a rigid amorphous fraction (RAF). For nanocomposites based on a semicrystalline polymer the RAF is due to both the crystallites (RAFcrystal) and the filler (RAFfiller). Polymer nanocomposite based on poly(L-lactide) and MgAl layered double hydroxide nanofiller were prepared. Due to the low crystallization rate of PLA ist crystallization can be suppressed by a high enough cooling rate, and the RAF is due only to the nanofiller. The MAF, CF, and RAF were estimated by Temperature Modulated DSC. For the first time CF, MAF, RAFcrystal, and RAFfiller could be estimated. It was found, that RAFfiller increases linearly with the concentration of the nanofiller for this system. Furthermore, RAFcrystal is only slightly influenced by the presence of the nanofiller. KW - Polymer based nanocomposites PY - 2017 DO - https://doi.org/10.1016/j.polymer.2016.11.065 SN - 0032-3861 SN - 1873-2291 VL - 108 SP - 257 EP - 264 PB - Elesevier AN - OPUS4-39052 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Höhm, S. A1 - Rosenfeld, A. A1 - Krüger, Jörg A1 - Bonse, Jörn T1 - Laser-induced periodic surface structures on zinc oxide crystals upon two-colour femtosecond double-pulse irradiation N2 - In order to study the temporally distributed energy deposition in the formation of laser-induced periodic surface structures (LIPSS) on single-crystalline zinc oxide (ZnO), two-colour double-fs-pulse experiments were performed. Parallel or cross-polarised double-pulse sequences at 400 and 800 nm wavelength were generated by a Mach–Zehnder interferometer, exhibiting inter-pulse delays up to a few picoseconds between the sub-ablation 50-fs-pulses. Twenty two-colour double-pulse sequences were collinearly focused by a spherical mirror to the sample surface. The resulting LIPSS periods and areas were analysed by scanning electron microscopy. The delay-dependence of these LIPSS characteristics shows a dissimilar behaviour when compared to the semiconductor silicon, the dielectric fused silica, or the metal titanium. A wavelength-dependent plasmonic mechanism is proposed to explain the delay-dependence of the LIPSS on ZnO when considering multi-photon excitation processes. Our results support the involvement of nonlinear processes for temporally overlapping pulses. These experiments extend previous two-colour studies on the indirect semiconductor silicon towards the direct wide band-gap semiconductor ZnO and further manifest the relevance of the ultrafast energy deposition for LIPSS formation. KW - Laser-induced periodic surface structures, LIPSS KW - Laser ablation KW - Surface plasmon polariton PY - 2017 DO - https://doi.org/10.1088/1402-4896/aa5578 SN - 1402-4896 SN - 0031-8949 VL - 92 IS - 3 SP - Article 034003, 1 EP - 7 PB - IOP CY - Bristol, UK AN - OPUS4-39082 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -