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Title: Impact of high energy ball milling on the nanostructure of magnetite–graphite and magnetite–graphite–molybdenum disulphide blends

Abstract

Different, partly complementary and partly redundant characterization methods were applied to study the transition of magnetite, graphite and MoS{sub 2} 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. - Highlights: • Characterization of microstructural changes induced by high energy ball milling • Assessment of the potential of different characterization methods • Impact of mechanical alloying on tribological performance revealed by tests • Preparation of an artificial third body resembling the one formed during braking.

Authors:
 [1]; ; ;  [1];  [2];  [3]; ; ;  [4]
  1. BAM Federal Institute for Materials Research and Testing, 12200 Berlin (Germany)
  2. Instituto de Geociências, UFRGS, P.O. Box 15001, 91501-970 Porto Alegre (Brazil)
  3. Instituto de Física, UFRGS, P.O. Box 15051, 91501-970 Porto Alegre (Brazil)
  4. Zoz Group, 57482 Wenden (Germany)
Publication Date:
OSTI Identifier:
22288686
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 86; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALLOYS; CRYSTALS; FRICTION; GRAIN SIZE; GRAPHITE; MAGNETITE; MILLING; MOLYBDENUM SULFIDES; NANOSTRUCTURES; POWDERS; RAMAN SPECTROSCOPY; RAW MATERIALS; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION; X-RAY PHOTOELECTRON SPECTROSCOPY

Citation Formats

Österle, W., E-mail: Werner.oesterle@bam.de, Orts-Gil, G., Gross, T., Deutsch, C., Hinrichs, R., Vasconcellos, M.A.Z., Zoz, H., Yigit, D., and Sun, X. Impact of high energy ball milling on the nanostructure of magnetite–graphite and magnetite–graphite–molybdenum disulphide blends. United States: N. p., 2013. Web. doi:10.1016/J.MATCHAR.2013.09.007.
Österle, W., E-mail: Werner.oesterle@bam.de, Orts-Gil, G., Gross, T., Deutsch, C., Hinrichs, R., Vasconcellos, M.A.Z., Zoz, H., Yigit, D., & Sun, X. Impact of high energy ball milling on the nanostructure of magnetite–graphite and magnetite–graphite–molybdenum disulphide blends. United States. doi:10.1016/J.MATCHAR.2013.09.007.
Österle, W., E-mail: Werner.oesterle@bam.de, Orts-Gil, G., Gross, T., Deutsch, C., Hinrichs, R., Vasconcellos, M.A.Z., Zoz, H., Yigit, D., and Sun, X. 2013. "Impact of high energy ball milling on the nanostructure of magnetite–graphite and magnetite–graphite–molybdenum disulphide blends". United States. doi:10.1016/J.MATCHAR.2013.09.007.
@article{osti_22288686,
title = {Impact of high energy ball milling on the nanostructure of magnetite–graphite and magnetite–graphite–molybdenum disulphide blends},
author = {Österle, W., E-mail: Werner.oesterle@bam.de and Orts-Gil, G. and Gross, T. and Deutsch, C. and Hinrichs, R. and Vasconcellos, M.A.Z. and Zoz, H. and Yigit, D. and Sun, X.},
abstractNote = {Different, partly complementary and partly redundant characterization methods were applied to study the transition of magnetite, graphite and MoS{sub 2} 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. - Highlights: • Characterization of microstructural changes induced by high energy ball milling • Assessment of the potential of different characterization methods • Impact of mechanical alloying on tribological performance revealed by tests • Preparation of an artificial third body resembling the one formed during braking.},
doi = {10.1016/J.MATCHAR.2013.09.007},
journal = {Materials Characterization},
number = ,
volume = 86,
place = {United States},
year = 2013,
month =
}
  • Two expanded graphites (EG), marked as EG-1 and EG-2, were prepared by rapid heating of expandable graphite to 600 and 1000 deg. C, respectively, and ball milled in a high-energy mill (planetary-type) under air atmosphere. The microstructure evolution of the ball-milled samples was characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). XRD analysis shows that the evolution degree of the average crystallite thickness along the c-axis (L{sub c}) of EG-2 is lower than that of EG-1 during the milling process. From the HRTEM images of the samples after 100 h ball-milling, slightly curved graphene planes canmore » be frequently observed both in the two EGs, however, EG-1 and EG-2 exhibit sharply curved graphene planes and smoothly curved graphene planes with high bending angles, respectively.« less
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  • Energy-band alignments for molybdenum disulphide (MoS{sub 2}) films on high-k dielectric oxides have been studied using photoemission spectroscopy. The valence band offset (VBO) at monolayer MoS{sub 2}/Al{sub 2}O{sub 3} (ZrO{sub 2}) interface was measured to be 3.31 eV (2.76 eV), while the conduction-band offset (CBO) was 3.56 eV (1.22 eV). For bulk MoS{sub 2}/Al{sub 2}O{sub 3} interface, both VBO and CBO increase by ∼0.3 eV, due to the upwards shift of Mo 4d{sub z{sup 2}} band. The symmetric change of VBO and CBO implies Fermi level pinning by interfacial states. Our finding ensures the practical application of both p-type and n-type MoS{sub 2} based complementarymore » metal-oxide semiconductor and other transistor devices using Al{sub 2}O{sub 3} and ZrO{sub 2} as gate materials.« less
  • The formation behavior of Y₂O₃ ceramic particles was studied by employing a very high energy ball milling (milling energy: ~165 kJ/g·hit, milling speed: 1000 rpm). Both the XRD and HRTEM studies revealed that the high impact strain energy generated during the milling caused a drastic phase transition from the original C-type cubic (space group Ia3, a=10.58 Å) to the metastable B-type monoclinic (space group C2/m, a=13.89 Å), finally followed by a partial solid-state amorphization. The cubic phase was difficult to be reduced down to smaller than 10 nm, while the monoclinic phase was stabilized at sizes smaller than 10 nmmore » with a mean crystallite size of 7.57 nm. Consequently, the existence of Y₂O₃ at a nanoscale smaller than 10 nm is possible by forming metastable monoclinic crystals, which are strain-induced. - Graphical abstract: The fig shows the solid-state phase formation of Y₂O₃ by very high energy input into the particles during milling: ordered body-centered cubic phase (space group Ia3, a=10.58 Å) nanocrystalline monoclinic phase (space group C2/m, a=13.89 Å) disordered monoclinic phase partial amorphous phase. The formation of Y₂O₃ smaller than 10 nm was strongly dependent on whether the phase transition from cubic to monoclinic occurred. Highlights: • This paper analyses very high energy milling behavior of coarse Y₂O₃ particles. • A drastic phase transition from cubic to monoclinic occurred with a partial amorphization. • An existence of Y₂O₃ smaller than 10 nm is possible by forming strain-induced monoclinic crystals.« less
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