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Title: Electron microscopic evidence for a tribologically induced phase transformation as the origin of wear in diamond

Tribological testing of a coarse-grained diamond layer, deposited by plasma-enhanced chemical vapor deposition, was performed on a ring-on-ring tribometer with a diamond counterpart. The origin of the wear of diamond and of the low friction coefficient of 0.15 was studied by analyzing the microstructure of worn and unworn regions by transmission and scanning electron microscopy. In the worn regions, the formation of an amorphous carbon layer with a thickness below 100 nm is observed. Electron energy loss spectroscopy of the C-K ionization edge reveals the transition from sp{sup 3}-hybridized C-atoms in crystalline diamond to a high fraction of sp{sup 2}-hybridized C-atoms in the tribo-induced amorphous C-layer within a transition region of less than 5 nm thickness. The mechanically induced phase transformation from diamond to the amorphous phase is found to be highly anisotropic which is clearly seen at a grain boundary, where the thickness of the amorphous layer above the two differently oriented grains abruptly changes.
Authors:
; ; ;  [1] ; ;  [2] ;  [2] ;  [3]
  1. Laboratory for Electron Microscopy, Karlsruhe Institute of Technology (KIT), Engesserstr. 7, D-76131 Karlsruhe (Germany)
  2. Fraunhofer Institute for Mechanics of Materials IWM, Wöhlerstr. 11, D-79108 Freiburg (Germany)
  3. (KIT), Kaiserstr. 12, D-76131 Karlsruhe (Germany)
Publication Date:
OSTI Identifier:
22278062
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 6; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE; AMORPHOUS STATE; ANISOTROPY; CHEMICAL VAPOR DEPOSITION; DIAMONDS; ENERGY-LOSS SPECTROSCOPY; FRICTION FACTOR; GRAIN BOUNDARIES; LAYERS; MATERIALS TESTING; PHASE TRANSFORMATIONS; SCANNING ELECTRON MICROSCOPY; THICKNESS; TRIBOLOGY; WEAR