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  • Österle, Werner (14)
  • Gradt, Thomas (6)
  • Häusler, Ines (5)
  • Orts Gil, Guillermo (5)
  • Dmitriev, A.I. (4)
  • Hodoroaba, Vasile-Dan (3)
  • Unger, Wolfgang (3)
  • Deutsch, Cornelius (2)
  • Dörfel, Ilona (2)
  • Natte, Kishore (2)
  • Ortel, Erik (2)
  • Rades, Steffi (2)
  • Schneider, Thomas (2)
  • Sun, X. (2)
  • Wetzel, B. (2)
  • Yigit, D. (2)
  • Zhang, G. (2)
  • Andersen, I. H. (1)
  • Arakawa, T. (1)
  • Azevedo, César Roberto de Farias (1)
  • Brown, S. C. (1)
  • Brückner, A. (1)
  • Burchett, W. W. (1)
  • Chan, C. (1)
  • Coleman, V. A. (1)
  • Dietrich, Paul (1)
  • Dmitriev, A. I. (1)
  • Giovannozzi, A. (1)
  • Girod, Matthias (1)
  • Gross, Thomas (1)
  • Grulke, E. A. (1)
  • Hammouri, Basem (1)
  • Herrmann, J. (1)
  • Hinrichs, R. (1)
  • Holzweber, Markus (1)
  • Jämting, Å. K. (1)
  • Kalbe, Henryk (1)
  • Kim, Y. H. (1)
  • Kollmer, F. (1)
  • Kumagai, K. (1)
  • Lambert, J. W. (1)
  • Maaßdorf, A. (1)
  • Malcher, M. (1)
  • Maskos, M. (1)
  • Morales Guzman, Pablo Israel (1)
  • Narbey, S. (1)
  • Nikonov, A. Y. (1)
  • Oswald, F. (1)
  • Paul, D. (1)
  • Peplinski, Burkhard (1)
  • Reinstädt, Philipp (1)
  • Ren, H. (1)
  • Rodrigues, A.C.P. (1)
  • Rooch, Heidemarie (1)
  • Rossi, A. (1)
  • Schmidt, M. (1)
  • Schwegler-Berry, D. (1)
  • Senoner, Mathias (1)
  • Song, N. W. (1)
  • Stefaniak, A. B. (1)
  • Stromberg, A. J. (1)
  • Theiler, Geraldine (1)
  • Thiermann, Raphael (1)
  • Thünemann, Andreas F. (1)
  • Vasconcellos, M.A.Z. (1)
  • Weihnacht, V. (1)
  • Wollenschläger, Nicole (1)
  • Wolter, Christian (1)
  • Yamamoto, K. (1)
  • Yashiki, K. (1)
  • Zeigmeister, U. (1)
  • Zheng, J. (1)
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Erscheinungsjahr

  • 2018 (1)
  • 2017 (2)
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  • 2015 (3)
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  • 2013 (5)

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  • Zeitschriftenartikel (14) (entfernen)

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  • Englisch (13)
  • Deutsch (1)

Referierte Publikation

  • ja (14) (entfernen)

Schlagworte

  • Ball milling (3)
  • Pin-on-disc test (2)
  • Raman spectroscopy (2)
  • TEM (2)
  • Third body (2)
  • Transmission electron microscopy (2)
  • Tribofilm (2)
  • AES (1)
  • Automotive braking (1)
  • BAM-L200 (1)
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Organisationseinheit der BAM

  • 6 Materialschutz und Oberflächentechnik (14) (entfernen)

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On the role of surface composition and curvature on biointerface formation and colloidal stability of nanoparticles in a protein-rich model system (2013)
Orts Gil, Guillermo ; Natte, Kishore ; Thiermann, Raphael ; Girod, Matthias ; Rades, Steffi ; Kalbe, Henryk ; Thünemann, Andreas F. ; Maskos, M. ; Österle, Werner
The need for a better understanding of nanoparticle–protein interactions and the mechanisms governing the resulting colloidal stability has been emphasised in recent years. In the present contribution, the short and long term colloidal stability of silica nanoparticles (SNPs) and silica–poly(ethylene glycol) nanohybrids (Sil–PEG) have been scrutinised in a protein model system. Well-defined silica nanoparticles are rapidly covered by bovine serum albumin (BSA) and form small clusters after 20 min while large agglomerates are detected after 10 h depending on both particle size and nanoparticle–protein ratio. Oppositely, Sil–PEG hybrids present suppressive protein adsorption and enhanced short and long term colloidal stability in protein solution. No critical agglomeration was found for either system in the absence of protein, proving that instability found for SNPs must arise as a consequence of protein adsorption and not to high ionic environment. Analysis of the small angle X-ray scattering (SAXS) structure factor indicates a short-range attractive potential between particles in the silica-BSA system, which is in good agreement with a protein bridging agglomeration mechanism. The results presented here point out the importance of the nanoparticle surface properties on the ability to adsorb proteins and how the induced or depressed adsorption may potentially drive the resulting colloidal stability.
Size and shape distributions of primary crystallites in titania aggregates (2017)
Grulke, E. A. ; Yamamoto, K. ; Kumagai, K. ; Häusler, Ines ; Österle, Werner ; Ortel, Erik ; Hodoroaba, Vasile-Dan ; Brown, S. C. ; Chan, C. ; Zheng, J. ; Yamamoto, K. ; Yashiki, K. ; Song, N. W. ; Kim, Y. H. ; Stefaniak, A. B. ; Schwegler-Berry, D. ; Coleman, V. A. ; Jämting, Å. K. ; Herrmann, J. ; Arakawa, T. ; Burchett, W. W. ; Lambert, J. W. ; Stromberg, A. J.
The primary crystallite size of titania powder relates to its properties in a number of applications. Transmission electron microscopy was used in this interlaboratory comparison (ILC) to measure primary crystallite size and shape distributions for a commercial aggregated titania powder. Data of four size descriptors and two shape descriptors were evaluated across nine laboratories. Data repeatability and reproducibility was evaluated by analysis of variance. One-third of the laboratory pairs had similar size descriptor data, but 83% of the pairs had similar aspect ratio data. Scale descriptor distributions were generally unimodal and were well-described by lognormal reference models. Shape descriptor distributions were multi-modal but data visualization plots demonstrated that the Weibull distribution was preferred to the normal distribution. For the equivalent circular diameter size descriptor, measurement uncertainties of the lognormal distribution scale and width parameters were 9.5% and 22%, respectively. For the aspect ratio shape descriptor, the measurement uncertainties of the Weibull distribution scale and width parameters were 7.0% and 26%, respectively. Both measurement uncertainty estimates and data visualizations should be used to analyze size and shape distributions of particles on the nanoscale.
Impact of copper nanoparticles on tribofilm formation determined by pin-on-disc tests with powder supply: Addition of artificial third body consisting of Fe3O4, Cu and graphite (2017)
Rodrigues, A.C.P. ; Österle, Werner ; Gradt, Thomas ; Azevedo, César Roberto de Farias
Copper, magnetite and graphite particles were mixed in order to observe their impact on the coefficient of friction (CoF) during pin-on-disc tests and on the tribofilm formation after testing. Pure magnetite powder provided a value of CoF of 0.4. Magnetite-copper mixtures tested at 400 °C revealed lower CoF values (~0.4) than those at room temperature (~0.6). Magnetite-graphite and magnetite-graphite-copper mixtures presented lower CoF values (~0.3). All systems formed a magnetite-based tribofilm and patches of metallic copper were found on the tribosurfaces of the mixtures containing copper. Carbon layers and graphite nanoinclusions were observed in the graphite mixtures. The incorporation of zirconia particles, a by-product of ball milling mixing, prevented the selective transfer of graphite and copper to the tribosurfaces of some of the samples.
Comprehensive characterization of ball-milled powders simulating a tribofilm system (2016)
Häusler, Ines ; Dörfel, Ilona ; Peplinski, Burkhard ; Dietrich, Paul ; Unger, Wolfgang ; Österle, Werner
A model system was used to simulate the properties of tribofilms which form during automotive braking. The model system was prepared by ball milling of a blend of 70 vol.% iron oxides, 15 vol.% molybdenum disulfide and 15 vol.% graphite. The resulting mixture was characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and various transmission electron microscopic (TEM) methods, including energy dispersive X-ray spectroscopy (EDXS), high resolution investigations (HRTEM) with corresponding simulation of the HRTEM images, diffraction methods such as scanning nano-beam electron diffraction (SNBED) and selected area electron diffraction (SAED). It could be shown that the ball milling caused a reduction of the grain size of the initial components to the nanometer range. Sometimes even amorphization or partial break-down of the crystal structure was observed for MoS2 and graphite. Moreover, chemical reactions lead to a formation of surface coverings of the nanoparticles by amorphous material, molybdenum oxides, and iron sulfates as derived from XPS.
In-depth structural and chemical characterization of engineered TiO2 films (2016)
Ortel, Erik ; Häusler, Ines ; Österle, Werner ; Narbey, S. ; Oswald, F. ; Andersen, I. H. ; Holzweber, Markus ; Unger, Wolfgang ; Hodoroaba, Vasile-Dan
Analytical routines for a comprehensive in-depth morphological, structural, and chemical characterization of functionalized TiO2 films by using different state-of-the-art analytical techniques are presented and discussed with the main objective to identify potential reference TiO2 coating parameters able to be certified at a later stage. TiO2 films fabricated by two different synthetic procedures as representative for two main large-scale applications were selected: (i) pulsed d.c. magnetron sputtering for photocatalytic applications and (ii) screen printing from preformed anatase nanoparticles. The screen-printed films were further loaded with a sensitizing dye for application as a dye-sensitized solar cell. Film properties such as microstructure and crystallographic texture of pulsed d.c. magnetron sputtering synthesized films were systematically studied by means of scanning nanobeam electron diffraction in a transmission electron microscope and the surface and inner morphology by scanning electron microscopy. The dye distribution over the depth of screen-printed TiO2 layers was analyzed before and after dye-loading by means of energy dispersive X-ray spectroscopy at scanning electronmicroscope, Auger electron spectroscopy and time-of-flight secondary ion mass spectrometry. The long-term goal of the present study is the improvement of quality of the TiO2 film parameters as measured by using different types of reference TiO2 coatings having specific parameters certified.
Exploring the beneficial role of tribofilms formed from an epoxy-based hybrid nanocomposite (2015)
Österle, Werner ; Dmitriev, A.I. ; Gradt, Thomas ; Häusler, Ines ; Hammouri, Basem ; Morales Guzman, Pablo Israel ; Wetzel, B. ; Yigit, D. ; Zhang, G.
The composition and nanostructure of a beneficial tribofilm formed during sliding of a hybrid nanocomposite against steel were characterized comprehensively. A similar nanostructure was produced by high energy ball milling of the three identified tribofilm constituents: silica, hematite and graphite. By supplying powders to a pin-on-disc test it has been shown that neither silica, nor hematite, nor a mixture of both provide the low coefficient of friction (COF) observed for the hybrid composite. Only if graphite was blended with the oxides, the low COF was obtained. Thus, a film of finely dispersed stable inorganic wear products containing 15 vol% graphite provides low friction and wear in the considered case.
Potential of different nickel coatings for optimizing the sliding behavior of electrical connectors (2018)
Österle, Werner ; Dörfel, Ilona ; Wollenschläger, Nicole ; Gradt, Thomas ; Wolter, Christian ; Reinstädt, Philipp ; Zeigmeister, U. ; Dmitriev, A. I. ; Nikonov, A. Y.
The potential of several nickel coatings was investigated by reciprocating sliding tests against copper thus simulating the plug-socket system of an electrical connector.
Multi-parametric reference nanomaterials for toxicology: state of the art, future challenges and potential candidates (2013)
Orts Gil, Guillermo ; Natte, Kishore ; Österle, Werner
A major requirement for the validation of methods assessing the risk associated with engineered nanoparticles (ENPs) is the use of reference materials (RMs). In the present contribution we review available RMs, ongoing projects and characterisation trends in the field. The conclusion is that actual approaches to RMs mostly deal with metrological considerations about single properties of the ENPs, typically their primary size, which can hardly be representative of nanoparticles characteristics in real testing media and therefore, not valid for reliable and comparable toxicological studies. As an alternative, we discussed the convenience and feasibility of establishing multi-parametric RMs for a series of ENPs, focusing on silica nanoparticles (SNPs). As a future perspective, the need to develop RMs based on hybrid nanoparticles is also discussed.
Tribological screening tests for the selection of raw materials for automotive brake pad formulations (2014)
Österle, Werner ; Deutsch, Cornelius ; Gradt, Thomas ; Orts Gil, Guillermo ; Schneider, Thomas ; Dmitriev, A.I.
A modified pin-on-disc test was applied to determine tribological properties of typical brake pad constituents. Ball-milling of these ingredients together with iron oxide and graphite provided model materials displaying the main features of real third bodies. Solid lubricants like graphite affected the friction and wear behaviour of Fe3O4 powders considerably whereas further addition of hard nanoparticles induced only minor effects. This was corroborated by comparison with modelling results. MoS2 played a dual role. Depending on special conditions, this ingredient either reduced or increased friction. The latter could be explained, after nanoscopic characterization, by oxidation and destruction of the wear-protecting tribofilm.
Impact of high energy ball milling on the nanostructure of magnetite-graphite and magnetite-graphite-molybdenum disulphide blends (2013)
Österle, Werner ; Orts Gil, Guillermo ; Gross, Thomas ; Deutsch, Cornelius ; Hinrichs, R. ; Vasconcellos, M.A.Z. ; Zoz, H. ; Yigit, D. ; Sun, X.
Different, partly complementary and partly redundant characterization methods were applied to study the transition of magnetite, graphite and MoS2 powders to mechanically alloyed nanostructures. The applied methods were: Transmission electron microscopy (TEM), Mössbauer spectroscopy (MS), Raman spectroscopy (RS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The main objective was to prepare a model material providing the essential features of a typical tribofilm forming during automotive braking, and to assess the impact of different constituents on sliding behaviour and friction level. Irrespective of the initial grain size, the raw materials were transferred to a nanocrystalline structure and mixed on a nanoscopic scale during high energy ball milling. Whereas magnetite remained almost unchanged, graphite and molybdenum disulphide were transformed to a nanocrystalline and highly disordered structure. The observed increase of the coefficient of friction was attributed to a loss of lubricity of the latter ingredient due to this transformation and subsequent oxidation.
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