TY - JOUR A1 - Zhang, G. A1 - Österle, Werner A1 - Jim, B. A1 - Häusler, Ines A1 - Hesse, Rene A1 - Wetzel, B. T1 - The role of surface topography in the evolving microstructure and functionality of tribofilms of an epoxy-based nanocomposite JF - Wear N2 - The topographic effect of steel counterface, finished by mechanical grinding with Ra ranging from 0.01 to 0.95 µm, on the structure and functionality of the tribofilm of a hybrid nanocomposite, i.e. epoxy matrix filled with monodisperse silica nanoparticles, carbon fibers and graphite, was systematically investigated. The nanostructure of the tribofilm was comprehensively characterized by using combined focused ion beam and transmission electron microscope analyses. It was identified that oxidation of the steel surface, release, compaction and tribosintering of silica nanoparticles and deposition of an epoxy-like degradation product as well as fragmentation of carbon fibers are main mechanisms determining the structure and functionality of the tribofilm. The size of roughness grooves determines the type and size class of wear particles to be trapped at the surface. An optimum groove size leading to a maximum of surface coverage with a nanostructured tribofilm formed mainly from released silica nanoparticles was identified. KW - hybrid nanocomposite KW - tribological performance KW - topographic effect KW - tribofilm KW - nanostructure PY - 2016 DO - https://doi.org/10.1016/j.wear.2016.06.012 VL - 364-365 SP - 48 EP - 56 PB - Elsevier B.V. AN - OPUS4-37937 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Dmitriev, A.I. A1 - Österle, Werner T1 - Sliding simulations with variable amounts of copper and graphite mixed with magnetite T2 - Proceedings EuroBrake 2016 N2 - Copper is one of the most important components in brake pads and its amount can reach up to 14%. In spite of a number of positive features copper usage in brake pad formulations has recently become the subject of considerable discussions, primarily due to concerns about potential risks related to environmental impacts of copper particles. So, for developing new pad formulations with possible replacements of copper content, it is very important to understand the functionality of copper additions to brake friction materials. In the paper theoretical investigation of the role of copper as a pad ingredient was carried out on the basis of modelling by the method of movable cellular automata (MCA). Our previous studies show that copper as a constituent of the tribofilm formed during braking provides smooth sliding by forming a granular layer of mechanically mixed materials from the friction layers. In the present study the concentration of copper particles in a Fe3O4-matrix was varied systematically in the range 5.5-28 vol. % and compared to mixtures with the same amount of graphite nanoparticles. The sliding simulations were performed while assuming material properties at 500°C in order to assess the beneficial role of copper during severe braking conditions corresponding to fading cycles during dynamometer testing. T2 - EuroBrake 2016 CY - Milano, Italy DA - 13.06.2016 KW - Movable cellular automata KW - Copper KW - Sliding simulation KW - Third body KW - Tribofilm PY - 2016 UR - www.eurobrake.net VL - EB2016-SVM-054 SP - 1 EP - 7 PB - FISITA AN - OPUS4-37938 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Dmitriev, A.I. A1 - Nikonov, A.Y. A1 - Österle, Werner T1 - Multiscale modeling of low friction sliding behavior of a hybrid epoxy-matrix nanocomposite T2 - Procedia Structural Integrity N2 - The method of movable cellular automata (MCA) and method of molecular dynamics (MD) were applied to simulate the friction and sliding behavior of model-tribofilms formed from a nanocomposite consisting of an epoxy matrix, 10 vol % micron-sized carbon fibers and 5 vol. % silica nanoparticles. Whereas MCA considered the tribofilm as an agglomerate of silica nanoparticles released from the composite and mixed with graphite particles, MD simulated the sliding behavior of an amorphous silica layer supported by stiff crystalline substrates on both sides. The MCA model provided reasonable quantitative results which corroborate experimental findings at moderate stressing conditions. The very low coefficient of friction observed experimentally under severe stressing conditions was not explained by this model. This could be attributed to the lack of mechanical data at the high temperature expected under these conditions. Although based on a simpler assumption of the tribofilm composition, MD-modelling could be easily applied to the expected high flash temperature and was able to predict friction reduction and smooth sliding under these conditions. T2 - 21st European Conference on Fracture ECF21 CY - Catania, Italy DA - 20.06.2016 KW - Silica nanoparticle KW - Hybrid composite KW - Tribofilm KW - Molecular dynamics KW - Movable cellular automata PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-379402 DO - https://doi.org/10.1016/j.prostr.2016.06.294 VL - 2 SP - 2347 EP - 2354 PB - Elsevier Ltd. AN - OPUS4-37940 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Qi, H. A1 - Zhang, G. A1 - Wetzel, B. A1 - Wang, T. A1 - Wang, Q. A1 - Österle, Werner T1 - Exploring the influence of counterpart materials on tribological behaviors of epoxy composites JF - Tribology International N2 - The dependence of the friction and wear of epoxy (EP) composites materials on counterpart materials, such as standard bearing steel, medium carbon steel and chrome-plating (Cr), was investigated. The conventional composite filled with short carbon fiber (SCF) and graphite shows the highest tribological performance when rubbing against Cr, whereas, the hybrid nanocomposite (EP filled with SCF, graphite and silica nanoparticles) exhibits the lowest friction and wear when sliding against the standard bearing steel. The role of nanoparticles in the tribological performance is distinctly different when sliding against with various counterpart materials. It is demonstrated that counterpart materials exert an important influence on material transfer, tribo-oxidation and mechanical mixing of wear products, resulting in the different formation mechanisms of transfer film. KW - Counterpart materials KW - Transfer film KW - Epoxy composites KW - Nanoparticles PY - 2016 DO - https://doi.org/10.1016/j.triboint.2016.08.015 VL - 103 SP - 566 EP - 573 PB - Elsevier Ltd. AN - OPUS4-37941 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Orts-Gil, G. A1 - Österle, Werner ED - Tantra, R. T1 - Reference nanomaterials T2 - Nanomaterial Characterization N2 - This chapter reviews relevant aspects of the still less explored field of RNMs. In the first part, definition of RMs according to different metrological levels was presented as well as the general strategy on their development. In the second part, the importance of RNMs in material science and nanotoxicology is explained and considerations on the use of silica nano-objects as potential future reference material was discussed. Overall, several points should be highlighted from this chapter: Definition of a reference material depends on the level of standardization. Certified reference material represents the highest level of traceability. Different types of reference materials, standard materials and certified reference materials are available, as shown in Table 3.1. The preparation of nano-objects with well-defined mechanical properties is still an unsolved issue and thus needs further R&D activities. Nevertheless, amorphous silica seems to be a promising candidate for reaching this objective. Traceable properties of nanomaterials are still limited to few cases such as primary particle size and thickness measurements of very thin films. In general, developed RMs are monoparametric thus, only one characteristic of the nano-objects is reported. In nanotoxicology, the challenge is in the development of suitable RNM that bears similarities to the measurements made on the sample analysed. KW - Reference material KW - Certified reference material KW - Nanostructure PY - 2016 SN - 9781118753590 SP - 49 EP - 61 PB - Wiley & Sons, Ltd. ET - 1 AN - OPUS4-37943 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wolter, Christian A1 - Österle, Werner A1 - Gradt, Thomas T1 - Metal sulphides as friction stabilisers under variable humidity T2 - Reibung, Schmierung und Verschleiß N2 - Neben Kohlenstoff werden Metallsulfide in jeder Standardrezeptur für Bremsbeläge als Reibungsstabilisatoren verwendet. Um deren Wirkung zu untersuchen, wurden verschiedene Pulvermischungen in einer Stift-Scheibe-Anordnung tribologisch beansprucht, um künstliche dritte Körper zu erzeugen und zu testen, deren definierte Zusammensetzungen aus drei wichtigen Bestandteilen einer realen Reibschicht bestehen: Magnetit, Graphit und div. Metallsulfide. N2 - Besides carbon, metal sulphides are used in every standard brake pad formulation as friction stabilisers. In order to investigate their impact, various powder mixtures were tribologically stressed in a pin-on-disc device in order to produce and test artificial third bodies. containing the three main components of a real friction film, namely magnetite, graphite and a metal sulphide of interest. Since the sliding behaviour is influenced by the relative humidity the powder mixtures are tested at low, medium and high moisture levels. The tests revealed that the presence of graphite dominates the friction behaviour as well as the humidity sensitivity. The powders were prepared by either manual mixing or high energy ball-milling. Interestingly, all ball-milled blends provided coefficients of friction within the desired range for braking, which was attributed to the effect of zirconia particles from wear debris of the milling balls. The zirconia particles prevent the formation of solid lubricant films on the surfaces and support a homogeneous mixture of all constituents of the powder. Optimum brake performance is gained by an optimum combination of solid lubricants and abrasives. T2 - 57. Tribologie-Fachtagung CY - Göttingen, Germany DA - 26.09.2016 KW - Friction KW - Metal sulphides KW - Brake pad formulation PY - 2016 SN - 978-3-9817451-1-5 SP - 1.5/1 EP - 1.5/6 AN - OPUS4-37838 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhao, F. A1 - Li, G. A1 - Österle, Werner A1 - Häusler, Ines A1 - Zhang, G. A1 - Wang, T. A1 - Wang, Q. T1 - Tribological investigations of glass fiber reinforced epoxy composites under oil lubrication conditions JF - Tribology International N2 - The tribological performance of short glass fibers (SGF),solid lubricants and silica nanoparticles filled epoxy (EP) composites was investigated under oil lubrication conditions. It is demonstrated that the addition of SGF greatly reduces the friction and wear of EP. However, further addition of solid lubricants and silica nanoparticles does not change obviously the friction and wear. It is identified that the high tribological performance of SGF reinforced EP is related to the high load carrying capacity and abrasion resistance of SGF. The nanostructure of the tribofilm was comprehensively characterized. It is deemed that the tribofilm plays an important role in the tribological performance by avoiding the direct rubbing of the sliding pairs exposed to boundary and mixed lubrication conditions. KW - Reinforced epoxy composites KW - Short glass fiber KW - Oil lubrication KW - Tribofilm PY - 2016 DO - https://doi.org/10.1016/j.triboint.2016.07.002 SN - 0301-679X VL - 103 SP - 208 EP - 217 PB - Elsevier Ltd. AN - OPUS4-38145 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Dmitriev, A. I. A1 - Österle, Werner T1 - Sliding simulation of automotive brake primary contact with variable amounts of copper and graphite nanoparticles T2 - ADVANCED MATERIALS WITH HIERARCHICAL STRUCTURE FOR NEW TECHNOLOGIES AND RELIABLE STRUCTURES 2016 N2 - Copper is one of the most important components in brake pads and its amount can reach up to 14%. In spite of a number of positive features copper usage in brake pad formulations has recently become the subject of considerable discussions, primarily due to concerns about potential risks related to environmental impacts of copper particles. So, for developing new pad formulations with possible replacements of copper content, it is very important to understand the functionality of copper additions to brake friction materials. In the paper theoretical investigation of the role of copper as a pad ingredient was carried out on the basis of modelling by the method of movable cellular automata (MCA). In the study the concentration of copper particles in a Fe3O4-matrix was varied. The sliding simulations were performed while assuming material properties at 500 degrees C in order to assess the beneficial role of copper during severe braking conditions corresponding to fading cycles during dynamometer testing. T2 - International Conference on Advanced Materials with Hierarchical Structure for New Technologies and Reliable Structures CY - Tomsk, Russia DA - 19.09.2016 KW - Polymer matrix composite KW - Silica nanoparticles KW - Friction KW - Wear PY - 2016 DO - https://doi.org/10.1063/1.4966337 VL - 1783 SP - 020044-1 EP - 020044-4 AN - OPUS4-38933 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Nikonov, A. Y.. A1 - Dmitriev, A. I. A1 - Österle, Werner T1 - Molecular dynamics study of slip mechanisms of nickel with amorphous-like Ni-P coating T2 - ADVANCED MATERIALS WITH HIERARCHICAL STRUCTURE FOR NEW TECHNOLOGIES AND RELIABLE STRUCTURES 2016 N2 - In the paper by using molecular dynamics method we investigate behavior of nickel-phosphorus compound in amorphous-like state under conditions of shear loading at the constant velocity. Samples with an amorphous layer of pure nickel and nickel-phosphorus compound were considered. The analysis showed that forces of shear resistance in the sample with an amorphous layer containing phosphorus in about 3 times less than the sample with a layer of pure nickel. Thus, it was shown that nickel-phosphorous coating in amorphous-like state may exhibit low friction properties, and, therefore, serve as the solid lubricant material. T2 - International Conference on Advanced Materials with Hierarchical Structure for New Technologies and Reliable Structures CY - Tomsk, Russia DA - 19.09.2016 KW - Local structural transformations KW - Lattice PY - 2016 DO - https://doi.org/10.1063/1.4966457 VL - 1783 SP - 020164-1 EP - 020164-4 AN - OPUS4-38932 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dmitriev, A. I. A1 - Häusler, Ines A1 - Wetzel, B. A1 - Zhang, G. A1 - Österle, Werner T1 - Modeling of the stress-strain behavior of an epoxy-based nanocomposite filled with silica nanoparticles JF - Materials and Design N2 - The method of movable cellular automata (MCA) was applied to simulate the stress-strain behavior of a nano composite consisting of an epoxy matrix and 6 vol. % silica nano particles. The size of the elements used for modelling was fixed at 10 nm, corresponding approximately to the diameter of the filler particles. Since not only the stress-strain response of the two constituents but also debonding of neighboring particles and granular flow was taken into account, plastic deformation as well as crack initiation and propagation could be simulated with the model. Modelling results were compared with tensile test results of both, pure epoxy as well as the epoxy-6 vol. % SiO2 composite. Since assuming bulk properties of the two constituents did not yield satisfactory results, slight modifications of the nanoparticle response functions and nanostructures were tested numerically. Finally, it was observed that only the assumption of slightly increased strength properties of the epoxy yielded good correlation between experimental and modelling results. This was attributed to an increased cross linking of the epoxy caused by the presence of silica nano particles. KW - Nanocomposite KW - Polymer matrix composite KW - Stress-strain behavior KW - Modeling KW - Computational mechanics PY - 2016 DO - https://doi.org/http://dx.doi.org/10.1016/j.matdes.2015.10.038 SN - 0264-1275 VL - 89 SP - 950 EP - 956 PB - Elsevier AN - OPUS4-35596 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dmitriev, A. I. A1 - Österle, Werner ED - Österle, Werner ED - Zhang, G. T1 - The role of solid lubricants for brake friction materials JF - Lubricants special issue "tribofilms and solid lubrication" N2 - This review article comprises of three parts. Firstly, reports of brake manufacturers on the beneficial impact of solid lubricants for pad formulations are surveyed. Secondly, since tribofilms were identified to play a crucial role in friction stabilization and wear reduction, the knowledge about tribofilm structures formed during automotive braking was reviewed comprehensively. Finally, a model for simulating the sliding behavior of tribofilms is suggested and a review on modelling efforts with different model structures related to real tribofilms will be presented. Although the variety of friction composites involved in commercial brake systems is very broad, striking similarities were observed in respect to tribofilm nanostructures. Thus a generalization of the tribofilm nanostructure is suggested and prerequisites for smooth sliding performance and minimal wear rates have been identified. A minimum of 13 vol.% of soft inclusions embedded in an iron oxide based tribofilm is crucial for obtaining the desired properties. As long as the solid lubricants or their reaction products are softer than magnetite, the main constituent of the tribofilm, the model predicts smooth sliding and a minimum of wear. KW - Solid lubricant KW - Friction KW - Automotive braking KW - Tribofilm KW - Sliding simulation KW - MCA-modeling PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-355973 UR - www.mdpi.com/journal/lubricants DO - https://doi.org/10.3390/lubricants4010005 SN - 2075-4442 VL - 4 IS - 1 SP - 5 EP - 26 PB - MDPI CY - Basel, Switzerland AN - OPUS4-35597 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Dmitriev, A. I. A1 - Wetzel, B. A1 - Zhang, G. A1 - Häusler, Ines A1 - Jim, B.C. T1 - The role of carbon fibers and silica nanoparticles on friction and wear reduction of an advanced polymer matrix composite JF - Materials and design N2 - Excellent tribological properties of an advanced polymer matrix composite were obtained by a combination of micro- and nano-sized fillers. Surface features and the nanostructure of tribofilms were characterized by advanced microscopic techniques, and correlated with the macroscopic behavior in terms of wear rate and friction evolution. A model based on movable cellular automata was applied for obtaining a better understanding of the sliding behavior of the nanostructured tribofilms. The failure of the conventional composite without silica nanoparticles could be attributed to severe oxidational wear after degradation of an initially formed polymer transfer film. The hybrid composite preserves its antiwear and antifriction properties because flash temperatures at micron-sized carbon fibers, lead to polymer degradation and subsequent release of nanoparticles. It has been shown that the released particles are mixed with other wear products and form stable films at the disc surface thus preventing further severe oxidational wear. Furthermore, the released wear product also is embedding carbon fibers at the composite surface thus preventing fiber fragmentation and subsequent third body abrasion. With nanoscale modelling we were able to show that low friction and wear can be expected if the nanostructured silica films contain at least 10 vol.% of a soft ingredient. KW - Carbon fibers KW - Silica nanoparticles KW - Hybrid composite KW - Tribological properties KW - Tribofilm KW - Sliding simulation PY - 2016 DO - https://doi.org/10.1016/j.matdes.2015.12.175 SN - 0264-1275 VL - 93 SP - 474 EP - 484 PB - Elsevier AN - OPUS4-35598 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tasdemir, Z. A1 - Wollschläger, Nicole A1 - Österle, Werner A1 - Leblebici, Y. A1 - Alaca, B. E. T1 - A deep etching mechanism for trench-bridging silicon nanowires JF - Nanotechnology N2 - Introducing a single silicon nanowire with a known orientation and dimensions to a specific layout location constitutes a major challenge. The challenge becomes even more formidable, if one chooses to realize the task in a monolithic fashion with an extreme topography, a characteristic of microsystems. The need for such a monolithic integration is fueled by the recent surge in the use of silicon nanowires as functional building blocks in various electromechanical and optoelectronic applications. This challenge is addressed in this work by introducing a top-down, silicon-on-insulator technology. The technology provides a pathway for obtaining well-controlled silicon nanowires along with microstructures up to a three-order-of-magnitude scale difference. A two-step etching process is developed, where the first shallow etch defines a nanoscale protrusion on the wafer surface. After applying a conformal protection on the protrusion, a deep etch step is carried out forming the surrounding microscale features. A minimum nanowire cross-section of 35 nm by 168 nm is demonstrated in the presence of an etch depth of 10 m. All cross-sectional features are characterized via transmission electron microscopy and linked to specific process steps. The technology allows control on all dimensional aspects along with the exact location and orientation of the silicon nanowire. KW - Silicon nanowire KW - Deep reactive ion etching KW - Transmission electron microscopy PY - 2016 DO - https://doi.org/10.1088/0957-4484/27/9/095303 SN - 0957-4484 SN - 1361-6528 VL - 27 IS - 9 SP - 095303-1 EP - 095303-8 PB - IOP Publishing AN - OPUS4-35789 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Häusler, Ines A1 - Dörfel, Ilona A1 - Peplinski, Burkhard A1 - Dietrich, Paul A1 - Unger, Wolfgang A1 - Österle, Werner T1 - Comprehensive characterization of ball-milled powders simulating a tribofilm system JF - Materials characterization N2 - 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. KW - Tribofilm model system KW - Ball milling KW - X-ray powder diffraction KW - Transmission electron microscopy PY - 2016 DO - https://doi.org/10.1016/j.matchar.2015.11.024 SN - 1044-5803 SN - 1873-4189 VL - 111 SP - 183 EP - 192 PB - Elsevier CY - New York, NY AN - OPUS4-35051 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Senoner, Mathias A1 - Maaßdorf, A. A1 - Rooch, Heidemarie A1 - Österle, Werner A1 - Malcher, M. A1 - Schmidt, M. A1 - Kollmer, F. A1 - Paul, D. A1 - Hodoroaba, Vasile-Dan A1 - Rades, Steffi A1 - Unger, Wolfgang T1 - Lateral resolution of nanoscaled images delivered by surface-analytical instruments: application of the BAM-L200 certified reference material and related ISO standards JF - Analytical and bioanalytical chemistry N2 - The certified reference material BAM-L200, a nanoscale stripe pattern for length calibration and specification of lateral resolution, is described. BAM-L200 is prepared from a cross-sectioned epitaxially grown layer stack of AlxGa1–xAs and InxGa1–xAs on a GaAs substrate. The surface of BAM-L200 provides a flat pattern with stripe widths ranging down to 1 nm. Calibration distances, grating periods and stripe widths have been certified by TEM with traceability to the length unit. The combination of gratings, isolated narrow stripes and sharp edges of wide stripes offers plenty of options for the determination of lateral resolution, sharpness and calibration of length scale at selected settings of imaging surface-analytical instruments. The feasibility of the reference material for an analysis of the lateral resolution is demonstrated in detail by evaluation of ToF-SIMS, AES and EDX images. Other applications developed in the community are summarized, too. BAM-L200 fully supports the implementation of the revised International Standard ISO 18516 (in preparation) which is based on knowledge outlined in the Technical Report ISO/TR 19319:2013. KW - AES KW - BAM-L200 KW - CRM KW - EDX KW - Imaging KW - Lateral resolution KW - Sharpness KW - Standardisation KW - STXM KW - ToF-SIMS KW - XPEEM KW - XPS KW - Certified reference material KW - Imaging surface analysis PY - 2015 DO - https://doi.org/10.1007/s00216-014-8135-7 SN - 1618-2642 SN - 1618-2650 VL - 407 IS - 11 SP - 3211 EP - 3217 PB - Springer CY - Berlin AN - OPUS4-33033 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Dmitriev, A.I. A1 - Gradt, Thomas A1 - Häusler, Ines A1 - Hammouri, Basem A1 - Morales Guzman, Pablo Israel A1 - Wetzel, B. A1 - Yigit, D. A1 - Zhang, G. T1 - Exploring the beneficial role of tribofilms formed from an epoxy-based hybrid nanocomposite JF - Tribology International N2 - 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. KW - TEM KW - Nanocomposite KW - Tribofilm KW - Ball milling KW - Pin-on-disc test PY - 2015 DO - https://doi.org/10.1016/j.triboint.2015.03.006 SN - 0301-679X VL - 88 SP - 126 EP - 134 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-33035 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wollschläger, Nicole A1 - Österle, Werner A1 - Häusler, Ines A1 - Stewart, M. T1 - Ga+ implantation in a PZT film during focused ion beam micro-machining JF - Physica status solidi C N2 - The objective of the present work was to study the impact of Focused Ion Beam (FIB) machining parameters on the thickness of the damaged layer within a thin film PZT. Therefore, different Ga+- ion doses and ion energies were applied to a standard PZT film (80/20 lead zirconium titanate) under two beam incidence angles (90° and 1°). The thicknesses of the corresponding Ga+-implanted layers were then determined by cross-sectional TEM in combination with energy dispersive spectroscopic (EDS) line-scans and correlated with polarisation hysteresis loops. The results show a decrease of Ga+-implanted layer thickness with decreasing inclination angle, whereas ion energy and ion dose could be correlated with gallium concentration in the implanted layers.. Under the most unfavorable conditions the depth of the affected zone was 26 nm, it was only 2 nm for the most favorable conditions. KW - PZT KW - Focused ion beam KW - Gallium implantation KW - Polarisation-electric field loop PY - 2015 DO - https://doi.org/10.1002/pssc.201400096 SN - 1610-1634 SN - 1862-6351 SN - 1610-1642 VL - 12 IS - 3 SP - 314 EP - 317 PB - Wiley-VCH CY - Berlin AN - OPUS4-32872 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Giovannozzi, A. A1 - Gradt, Thomas A1 - Häusler, Ines A1 - Rossi, A. A1 - Wetzel, B. A1 - Zhang, G. A1 - Dmitriev, A.I. T1 - Exploring the potential of Raman spectroscopy for the identification of silicone oil residue and wear scar characterization for the assessment of tribofilm functionality JF - Tribology International N2 - We applied a combination of Raman spectroscopy (RS) and cross-sectional transmission electron microscopy (X-TEM) to identify silicone oil residues and tribofilms at steel disc surfaces after tribological testing. Neither chemical cleaning nor mechanical removal of a 50 µm thick surface layer produced a surface without any silicone residue. Nevertheless, long-term tribological properties are not affected due to silicone degradation which has been proved by Raman spectroscopy. Excellent anti-wear and anti-friction properties of a nanocomposite at severe stressing conditions correlated with the formation of a silica-based tribofilm containing amorphous and graphite-like carbon nanoparticles. Since reliable carbon quantification by analytical TEM is difficult, RS is a useful complementary method for carbon identification at wear scars. KW - Raman spectroscopy KW - Cross-sectional TEM KW - Silicone oil residue KW - Tribofilm PY - 2015 DO - https://doi.org/10.1016/j.triboint.2015.04.046 SN - 0301-679X VL - 90 SP - 481 EP - 490 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-33421 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, G. A1 - Wetzel, B. A1 - Jim, B. A1 - Österle, Werner T1 - Impact of counterface topography on the formation mechanisms of nanostructured tribofilm of PEEK hybrid nanocomposites JF - Tribology International N2 - The effect of steel counterface topography on the formation mechanisms of nanostructured tribofilms of polyetheretherketone (PEEK) hybrid nanocomposites was studied. Three types of surface finishes with mean roughness Ra ranging from nano- to micro-scale were investigated. Tribo-sintering of nanopartides, oxidation of counterface steel and compaction of wear debris are identified to be competing factors dominating the formation and function of the tribofilms. Counterface topography played an important role on the competing factors, and thereby influenced significantly the final structure, the load-carrying capability and the lubrication performance of the tribofilms. It was disclosed that a thin tribofilm, which mainly consists of silica nanoparticles and which forms on the counterface with a submicron roughness, benefits best the tribological performance of the composites KW - Surface topography KW - Nanocomposite KW - Tribology KW - Tribofilm PY - 2015 DO - https://doi.org/10.1016/j.triboint.2014.11.015 SN - 0301-679X VL - 83 SP - 156 EP - 165 PB - Butterworth-Heinemann CY - Oxford AN - OPUS4-34612 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pontes Rodrigues, A. C. A1 - Nunes Ribeiro, P. J. A1 - Österle, Werner A1 - de Farias Azevedo, C. R. T1 - Failure analysis as a tool to optimize the design of a ring on disc tribotest investigating the role of surface roughness JF - Engineering failure analysis N2 - The influence of the surface roughness of pearlitic grey cast iron discs on the formation of tribofilms and the evolution of the friction coefficient during a ring on disc tribotest with the addition of magnetite and magnetite–graphite nanopowders as interfacial media was investigated. The roughness parameters of the cast iron discs were varied by electro discharge machining (EDM) and grinding processes, producing four distinct surface roughness conditions. The evolution of the friction coefficient, however, did not reach the steady state for most of the samples and the role of the surface roughness on the friction coefficient could not be identified. Focused ion beam (FIB) microscopy on the cast iron discs was carried out to investigate the microstructure of the discs near the tribosurface. These results showed that the EDM process not only varied the surface roughness, but also changed the microstructure of the cast iron discs, promoting the incipient fusion of the cast iron surface, with the formation of ridges and casting defects (pores). As a result, a layer of rapidly solidified metal with a dendritic microstructure was formed near to the surface of the EDMed discs. KW - Ring-on disc tribotest KW - Surface roughness KW - EDM-processing KW - Rapid solification PY - 2015 DO - https://doi.org/10.1016/j.engfailanal.2015.03.011 SN - 1350-6307 SN - 1873-1961 VL - 56 SP - 131 EP - 141 PB - Elsevier Science Publ. CY - Oxford AN - OPUS4-34623 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -