TY - JOUR A1 - Österle, Werner A1 - Orts Gil, Guillermo A1 - Gross, Thomas A1 - Deutsch, Cornelius A1 - Hinrichs, R. A1 - Vasconcellos, M.A.Z. A1 - Zoz, H. A1 - Yigit, D. A1 - Sun, X. T1 - Impact of high energy ball milling on the nanostructure of magnetite-graphite and magnetite-graphite-molybdenum disulphide blends N2 - 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. KW - Ball milling KW - Mössbauer spectroscopy KW - Raman spectroscopy KW - Transmission electron microscopy KW - X-ray diffraction KW - X-ray photoelectron spectroscopy PY - 2013 U6 - https://doi.org/10.1016/j.matchar.2013.09.007 SN - 1044-5803 SN - 1873-4189 VL - 86 SP - 28 EP - 38 PB - Elsevier Inc. CY - New York, NY AN - OPUS4-29697 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 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 U6 - 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 - CONF A1 - Österle, Werner A1 - Deutsch, Cornelius A1 - Dörfel, Ilona A1 - Gradt, Thomas A1 - Häusler, Ines A1 - Orts-Gil, G. A1 - Prietzel, C. A1 - Schneider, Thomas T1 - Final outcome of a fundamental research project on tribofilms formed during automotive braking, Part 1: Experimental studies N2 - In order to obtain a better understanding of the role of tribofilms during automotive braking, their structures were investigated and the essential features identified. Next, different ingredient combinations were studied by preparing some model materials with simpler compositions than real tribofilms. A test method was developed for verifying the tribological properties of the model materials and for comparison with results obtained with numerical sliding simulations of such structures. Prerequisites of good brake Performance properties were identified. Although the coefficient of friction could be varied in a wide ränge, smooth sliding conditions could only be achieved with values smaller than 0.4. Tests with artificial third body powders turned out to be useful as screening method for the selection of raw materials for brake pad formulations. T2 - EuroBrake 2014 CY - Lille, France DA - 13.05.2014 KW - Tribofilm KW - Third body KW - Pad ingredients KW - Ball milling KW - Pin-on-disc test PY - 2014 SN - 978-0-9572076-4-6 SP - 1 EP - 8 PB - FISITA CY - London AN - OPUS4-35039 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 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 U6 - 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 -