Laboratoire Charles Coulomb UMR 5221 CNRS/UM2 (L2C)

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Passivation properties of Graphene Oxide

par Christelle EVE - publié le

Rigorously speaking, graphene refers to a single layer of sp2 carbon atoms covalently-bonded on a bidimensional hexagonal array, ie the elementary sublayer of graphite. Several effective techniques have been developed for preparing graphene and chemically derived graphene sheets : i) the costly bottom-up synthesis of large and high quality graphene single sheets [1], ii) solubilisation dispersion of graphene oxide in water [2], iii) solubilization of graphene intercalation compounds (GICs) in organic polar solvents [3]. The second class of graphene is highly dispersed in size and properties with a large number of defects due to the formation of oxygen-containing groups. On the other hand, the size of the flakes is smaller in the third method. The wet routes have nevertheless the advantage of being easily scalable for industrial applications concerning inks, coatings and composites but the deposition processes still need to be optimized. The L2C and its partners prepare aqueous graphene oxide inks, and develop processes to deposit thin layers on various surfaces and study their properties.

Graphene is especially highly impermeable to gases, and highly resistant to oxidation, and it is therefore expected to be a good candidate for passivation barriers [6]. However, some studies showed that even though graphene protects copper from thermal oxidation at low temperature and short term, a coating of graphene can promote galvanic corrosion over long time scales because of diffusion and trapping of oxidizing species under the graphene coating [7]. The origin of the oxidizing species agents is still in debate (diffusion of O2 and H2O molecules from the atmosphere through defects [7], trapping of oxygen retained in the grain boundaries of copper at the surface [8]…). However, the influence of the microstructure of graphene was not investigated so far and no detailed study of the oxidation kinetics in a controlled atmosphere was carried out. A setup and method based on coupled Raman/ photoluminescence spectroscopy was recently developed in our group for in situ studies of copper oxidation at controlled temperatures in a controlled atmosphere. This Master degree project will focus on the deposition of ultrathin films of graphene or graphene oxide (from a monolayer to 10 nm) on various copper-based materials (single crystals, copper foils, thin layers). The oxidation kinetics of the coated copper will then be investigated as a function of the thickness, structural (flake size, defects) and chemical (functionalization rate) properties of graphene, as well as the microstructure and oxygen content of the copper substrates. We are looking for a motivated Master 2 student in Physics or Physico-Chemistry. The student will be supervised by two “Soft Matter” physicists Christophe Blanc and Eric Anglaret. Usual stipends (for >2months internships) will be allocated.

[1] K.S. Novoselov et al, Science 306, 666-669 (2004)
[2] D.R. Dreyer et al, Chemical Society Reviews 39, 228-240 (2010)
[3] A. Pénicaud, C. Drummond, Accounts of chemical research 46, 129-137 (2012)
[4] G. Bepete et al, Nature Chemistry 9, 347 (2017)
[6] S. Chen et al, ACS nano 5, 1321-1327 (2011)
[7] M. Schriver, ACS nano 7, 5763-5768 (2013)

Contacts :
Dr Christophe Blanc
Laboratoire Charles Coulomb Bat 11, 1er étage
Tél : 0467143854
https://www.coulomb.univmontp2.
fr/perso/christophe.blanc
/

Pr Eric Anglaret
Laboratoire Charles Coulomb Bat 11, 3eme étage
Tél : 0467144638


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