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  • 1
    Article
    Article
    Language: English
    In: Advanced Engineering Materials, December 2010, Vol.12(12), pp.B657-B657
    Keywords: Engineering;
    ISSN: 1438-1656
    E-ISSN: 1527-2648
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  • 2
    Language: English
    In: Carbon, August, 2013, Vol.60, p.366(13)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.carbon.2013.04.049 Byline: Matthias M.L. Arras, Christoph Schillai, Thomas F. Keller, Robert Schulze, Klaus D. Jandt Abstract: Aligned multi-wall carbon nanotube (MWCNT)/polymer composite films were created in a one-step process. 5wt% MWCNT/semi-crystalline polymer composite films of approximately 100nm thickness were obtained by melt-drawing. The matrix polymers were isotactic polypropylene (iPP), poly(1-butene) (PB-1) and high density polyethylene (HDPE). Transmission electron microscopy (TEM) investigations revealed an exceptionally high degree of local MWCNT alignment with an angular deviation of 〈10[degrees] (HDPE) and 〈20[degrees] (iPP and PB-1) parallel to the films' drawing direction for a broad range of drawing velocities. For HDPE, the lamellar polymer-crystals at the interface between the MWCNT and the polymer film were identified as the nano-hybrid shish-kebab morphology by selected area electron diffraction. Based on the direct visualization of the MWCNT disentanglement process in the TEM, a polymer physics-based model for the unraveling of MWCNT entanglements, a source of aligned MWCNTs, is proposed that explains differences in MWCNT alignment encountered for different matrix polymers. The melt-drawing mediated MWCNT alignment provides both an innovative approach for the fabrication of applicable MWCNT containing films and a versatile tool for studying the interface in MWCNT/polymer composites. Article History: Received 19 October 2012; Accepted 13 April 2013
    Keywords: Butylene -- Analysis ; Nanotubes -- Analysis ; Polyethylene -- Analysis
    ISSN: 0008-6223
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Applied Physics Letters, 25 July 2016, Vol.109(4)
    Description: We report on the quantitative determination of the transient surface temperature of Pt(110) upon nanosecond laser pulse heating. We find excellent agreement between heat transport theory and the experimentally determined transient surface temperature as obtained from time-resolved X-ray diffraction on timescales from hundred nanoseconds to milliseconds. Exact knowledge of the surface temperature's temporal evolution after laser excitation is crucial for future pump-probe experiments at synchrotron storage rings and X-ray free electron lasers.
    Keywords: Nanoscale Science And Technology
    ISSN: 0003-6951
    E-ISSN: 1077-3118
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  • 4
    Language: English
    In: Langmuir : the ACS journal of surfaces and colloids, 20 March 2012, Vol.28(11), pp.5257-66
    Description: The nanostructure of thermally annealed thin films of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends on hydrophobic and hydrophilic substrates was studied to unravel the relationship between the substrate properties and the phase structure of polymer blends in confined geometry. Indeed, the nature of the employed substrates was found to affect the extent of phase separation, the PCBM aggregation state and the texture of the whole system. In particular, annealing below the melting temperature of the polymer yielded the formation of PCBM nanometric crystallites on the hydrophobic substrates, while mostly amorphous microscopic aggregates were formed on the hydrophilic ones. Moreover, while an enhanced in-plane orientation of P3HT lamellae was promoted on hydrophobic substrates, a markedly tilted geometry was produced on the hydrophilic ones. The observed effects were interpreted in terms of a simple model connecting the interface free energy for the blend films to the different polymer chain mobility and diffusion velocity of PCBM molecules on the different substrates.
    Keywords: Nanostructures ; Butyric Acid -- Chemistry
    ISSN: 07437463
    E-ISSN: 1520-5827
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  • 5
    Language: English
    In: Advanced Functional Materials, 20 June 2012, Vol.22(12), pp.2617-2623
    Description: Using fibrinogen (Fg) protein as a probe molecule, mapping using accumulated probe trajectories (MAPT) is performed on nanostructured melt‐drawn high‐density poly(ethylene) (HDPE) films composed of well‐oriented crystalline patches separated by amorphous regions. The spatially grouped molecular trajectories allow for identification of regions with distinct surface properties (i.e., crystalline vs. amorphous) while simultaneously determining the characteristic dynamic protein behavior within those regions. In the presence of solution with a sufficiently high Fg concentration, discrete patches of a dense, ordered protein layer form (presumably on crystalline HDPE regions), leading to a dramatic rise in the surface residence time (by more than two orders of magnitude) of molecules incorporated into the film. Within this ordered Fg layer, individual molecules exhibit slow anisotropic lateral diffusion; the mobility is restricted by the nanostructure boundaries of the underlying HDPE. On HDPE films at low Fg surface coverage, or on films that have been rendered hydrophilic with Ar plasma, short surface residence times and fast, isotropic diffusion are observed. These results demonstrate the ability of spatially resolved single‐molecule tracking to provide mechanistic information about biomolecule‐surface interactions in a highly heterogeneous environment. are shown. At high surface coverage of fibrinogen, an ordered protein layer forms that restricts diffusion in the direction perpendicular to the drawing direction and increases protein surface residence time. Several examples of the elongated protein occupancy regions that are observed as a result of this restriction are shown.
    Keywords: Surface Nanostructures ; Super‐Resolution Mapping ; High‐Density PolyEthylene Hdpe ; Anisotropic Diffusion ; Polymer Biointerfaces
    ISSN: 1616-301X
    E-ISSN: 1616-3028
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  • 6
    Language: English
    In: Journal of Materials Science, 2018, Vol.53(14), pp.10411-10422
    Description: (100) Oriented niobium (Nb) crystals annealed in the vacuum conditions close to that used in mass production of 1.3 GHz superconducting radio frequency cavities for linear accelerators and treated in nitrogen at a partial pressure of 0.04 mbar at temperatures of 800 and 900 °C have been studied. The surfaces of the nitrogen-treated samples were investigated by means of various surface-sensitive techniques, including grazing-incidence X-ray diffraction, X-ray photoemission spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy in planar view and on cross-sections prepared by a focused ion beam. The appearance of a dense layer of epitaxial rectangular precipitates has been observed for the Niobium nitrided at 900 °C. Increased nitrogen concentration in the near-surface region was detected by glow-discharge optical-emission spectroscopy, focused ion-beam cross-sectional images and X-ray photoelectron spectroscopy. Crystalline phases of NbO and β-Nb 2 N were identified by X-ray diffraction. This information was confirmed by X-ray photoelectron measurements, which in addition revealed the presence of Nb 2 O 5 , NbON, NbN, and NbN x O y components on the surface. These results establish the near-surface Nb phase composition after high-temperature nitrogen treatment, which is important for obtaining a better understanding of the improved RF cavity performance.
    Keywords: Epitaxy ; X-Ray Spectroscopy ; Superconductors ; X-Ray Diffraction;
    ISSN: 0022-2461
    E-ISSN: 1573-4803
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  • 7
    Language: English
    In: Macromolecules, 03/11/2014, Vol.47(5), pp.1705-1714
    Description: Thin film surface nanostructures of semicrystalline diblock copolymer are promising for the fabrication of photonic crystals and bioanalytical devices because they might be tailorable by controlled crystallization. One approach to systematically control polymer crystallization is a self-nucleation experiment. The self-nucleation experiment for block copolymers has only been reported for the bulk and so far not for thin films. Considering the versatility of a tailorable surface nanostructure, it is promising to apply the controlled crystallization of a bulk self-nucleation experiment to thin films of a diblock copolymer. In the current study we tested the hypothesis that within two self-nucleation experiments, i.e., in the bulk and thin film, the calorimetric bulk properties of a polybutadiene-block-poly(ethylene oxide) can be correlated to the resulting thin film surface nanostructures and to understand as well as predict their formation. The calorimetric bulk properties measured by differential scanning calorimetry in the bulk self-nucleation experiment were correlated to surface nanostructures measured by atomic force microscopy of the thin film self-nucleation experiment samples. In analogy to the bulk self-nucleation experiment, we introduced a crystalline standard for the thin film self-nucleation experiment where the crystalline lamellae consisted of once-folded chains. Annealing the thin film crystalline standard promoted the thickening of crystalline lamellae on the film surface which is explained by the formation of less folded chain crystals that obtain higher melting temperatures. The crystalline lamellae thickness was steplessly variable within the range of 8-16 nm. In analogy to the Hoffman-Weeks and Gibbs-Thomson plots, we derived a function which can be used to predict the lamellae thickness as a function of the annealing temperature. Bulk and thin film self-nucleation experiments were successfully related, since thin film surface nanostructures were consistently correlated to calorimetric results. We established the dual self-nucleation experiment as a powerful tool to predictably tailor thin film nanostructures in the range of several nanometers.
    Keywords: Nanostructure ; Thin-Coatings ; Controlled-Crystallisation ; Plant-Control-Systems ; Machine-Control ; System-Monitoring ; Polymer-Crystallisation ; Calorimetry ; Photonic-Crystals ; Lamella:Lamina ; Block-Copolymers ; Polybutadiene ; Ethylene-Oxide ; Scanning-Force-Microscopy ; Copolymer ; Melting-Temperature ; Annealing-Temperature ; Nanostruktur ; Dünnfilm ; Gesteuerte Kristallisation ; Anlagensteuerung ; Maschinenregelung ; Systemüberwachung ; Polymerkristallisation ; Kalorimetrie ; Photonischer Kristall ; Lamelle ; Blockcopolymer ; Polybutadien ; Ethylenoxid ; Atomkraftmikroskopie ; Copolymer ; Schmelztemperatur ; Glühtemperatur ; Chemistry;
    ISSN: 0024-9297
    E-ISSN: 1520-5835
    Source: American Chemical Society (via CrossRef)
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  • 8
    Language: English
    In: Carbon, August 2013, Vol.60, pp.366-378
    Description: Aligned multi-wall carbon nanotube (MWCNT)/polymer composite films were created in a one-step process. 5 wt% MWCNT/semi-crystalline polymer composite films of approximately thickness were obtained by melt-drawing. The matrix polymers were isotactic polypropylene (iPP), poly(1-butene) (PB-1) and high density polyethylene (HDPE). Transmission electron microscopy (TEM) investigations revealed an exceptionally high degree of local MWCNT alignment with an angular deviation of (HDPE) and (iPP and PB-1) parallel to the films’ drawing direction for a broad range of drawing velocities. For HDPE, the lamellar polymer-crystals at the interface between the MWCNT and the polymer film were identified as the nano-hybrid shish-kebab morphology by selected area electron diffraction. Based on the direct visualization of the MWCNT disentanglement process in the TEM, a polymer physics-based model for the unraveling of MWCNT entanglements, a source of aligned MWCNTs, is proposed that explains differences in MWCNT alignment encountered for different matrix polymers. The melt-drawing mediated MWCNT alignment provides both an innovative approach for the fabrication of applicable MWCNT containing films and a versatile tool for studying the interface in MWCNT/polymer composites.
    Keywords: Chemistry
    ISSN: 0008-6223
    E-ISSN: 1873-3891
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  • 9
    Language: English
    In: Langmuir : the ACS journal of surfaces and colloids, 21 December 2010, Vol.26(24), pp.18893-901
    Description: We report a templating effect of uniaxially oriented melt-drawn polyethylene (MD-PE) films on α-helical poly(L-lysine)/poly(styrenesulfonate) (α-PLL/PSS) complexes deposited by the layer-by-layer (LBL) method. The melt-drawing process induced an MD-PE fiber texture consisting of nanoscale lamellar crystals embedded in amorphous regions on the MD-PE film surface whereby the common crystallographic c axis is the PE molecular chain direction parallel to the uniaxial melt-drawing direction. The MD-PE film and the α-PLL/PSS deposit were analyzed by atomic force microscopy (AFM) and in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) using polarized light as a complementary method. Both methods revealed that α-PLL/PSS complexes adsorbed at the MD-PE surface were anisotropic and preferentially oriented perpendicular to the crystallographic c direction of the MD-PE film. Quantitatively, from AFM image analysis and ATR-FTIR dichroism of the amide II band of the α-PLL, mean cone opening angles of 12-18° for both rodlike α-PLL and the anisotropic α-PLL/PSS complexes with respect to the PE lamellae width direction were obtained. A model for the preferred alignment of α-PLL along the protruding PE lamellae is discussed, which is based on possible hydrophobic driving forces for the minimization of surface free energy at molecular and supermolecular topographic steps of the PE surface followed by electrostatic interactions between the interconnecting PSS and the α-PLL during layer-by-layer adsorption. This study elucidates the requirements and mechanisms involved in orienting biomolecules and may open up a path for designing templates to induce directed protein adsorption and cell growth by oriented polypeptide- or protein-modified PE surfaces.
    Keywords: Molecular Conformation ; Nanostructures -- Chemistry ; Polyethylene -- Chemistry ; Polylysine -- Chemistry
    ISSN: 07437463
    E-ISSN: 1520-5827
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  • 10
    Language: English
    In: Nano letters, 10 January 2018, Vol.18(1), pp.101-108
    Description: We report on a growth study of self-catalyzed GaAs nanowires based on time-resolved in situ X-ray structure characterization during molecular-beam-epitaxy in combination with ex situ scanning-electron-microscopy. We reveal the evolution of nanowire radius and polytypism and distinguish radial growth processes responsible for tapering and side-wall growth. We interpret our results using a model for diameter self-stabilization processes during growth of self-catalyzed GaAs nanowires including the shape of the liquid Ga-droplet and its evolution during growth.
    Keywords: Nanowires ; Growth ; in Situ X-Ray Diffraction ; Molecular Beam Epitaxy ; Polytypism ; Self-Catalyzed ; Tapering
    ISSN: 15306984
    E-ISSN: 1530-6992
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