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X‐ray photoelectron spectroscopy and tribology studies of annealed fullerene‐like WS 2 nanoparticles
Author(s) -
Späth B.,
Kopnov F.,
Cohen H.,
Zak A.,
Moshkovich A.,
Rapoport L.,
Jägermann W.,
Tenne R.
Publication year - 2008
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200779531
Subject(s) - x ray photoelectron spectroscopy , fullerene , annealing (glass) , nanoparticle , materials science , carbonization , molecule , stoichiometry , chemical engineering , spectroscopy , analytical chemistry (journal) , nanotechnology , chemistry , organic chemistry , scanning electron microscope , composite material , physics , quantum mechanics , engineering
The time dependent chemical changes occurring at the surface of inorganic fullerene‐like (IF) nanoparticles of WS 2 were investigated using X‐ray photoelectron spectroscopy (XPS) and compared to those of bulk powder, 2H‐WS 2 . It was possible to follow the long term surface oxidation and carbonization occurring at defects on the outermost surface (0001) molecular layers of the inorganic fullerene‐like nanoparticles. Vacuum annealing was shown to remove most of these contaminants and bring the surface close to its pristine stoichiometric composition. In accordance with previous measurements, further evidence was obtained for the existence of water molecules, which were entrapped in the hollow core and interstitial defects of the fullerene‐like nanoparticles during the synthesis. These water molecules were also shown to be removable by the vacuum annealing process. Chemically resolved electrical measurements (CREM) in the XPS showed that the IF samples had become less p‐type after the vacuum annealing. Finally, tribological measurements showed that the vacuum annealed IF samples performed better as an oil additive than the non‐annealed IF samples and the 2H‐WS 2 powder. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)