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  4. Ab initio thermodynamics study of ambient gases reacting with amorphous carbon
 
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2019
Journal Article
Titel

Ab initio thermodynamics study of ambient gases reacting with amorphous carbon

Abstract
Amorphous carbon (a-C) occurs as a tribologically induced phase in diamond or diamond-like carbon coatings. The interaction of ambient gases (H2, N2, O2, H2O, CO2) with a-C of varying mass density is studied by means of ab initio thermodynamics simulations. Different scenarios such as moist air or pure gases are investigated under different pressure and temperature conditions. Equilibrium concentrations of chemisorbed and fragmented final states are found to only exhibit a minor dependence on the specific conditions of the gas phase reservoir. The differences in local structure of the a-C samples with varying mass density such as pore size and coordination and dangling bonds, as well as the competition among different gas molecules for a-C atoms as reactants, affect the equilibrium concent rations to a greater degree. The availability and reactivity of a-C atoms are thus found to mainly control the chemical composition of a-C interacting with ambient gases in thermodynamic equilibrium. Trends found in the analysis of chemical groups occurring in equilibrium can possibly be transferred to a more realistic nonequilibrium tribological scenario.
Author(s)
Held, A.
Fraunhofer-Institut für Werkstoffmechanik IWM
Moseler, M.
Fraunhofer-Institut für Werkstoffmechanik IWM
Zeitschrift
Physical Review. B
Funder
Deutsche Forschungsgemeinschaft DFG
DOI
10.1103/PhysRevB.99.054207
File(s)
N-538048.pdf (639.16 KB)
Language
English
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Fraunhofer-Institut für Werkstoffmechanik IWM
Tags
  • amorphous carbon

  • Atom

  • chemical analysis

  • dangling bonds

  • gases

  • pore size

  • thermodynamic

  • tribology

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