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Lecture

Galvanically generated cathodic potential to enable minimal tribochemical wear in sodium chloride and ionic liquid aqueous solution

Wednesday (22.02.2017)
11:45 - 12:10 Rohrersaal
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Friction and wear occurs in almost all technical systems and cause enormous economic and environmentally impact. The global challenge consists in the development of eco-friendly, sustainable and energy efficient lubricants (‘green’ tribology). Bridging the gap between concepts of superlubricity, wearless sliding and friction control on the microscopic and macroscopic level are the current challenges in this research field [1].

The theoretical approach of this work is based on electrochemical processes to adsorb surface-active anisotropic structured surfactants in sliding contacts. In contrast to our preliminary work [2] and current research by other groups on the microscale [3], electrochemical potentials were galvanically generated by adapted combination of two materials in a water-based electrolyte. Using this method no external electric potential is needed.

Tribological investigations using an oscillating ball-on-disc test revealed that the generated electric potentials can be utilized to reduce wear. It has been observed that the cathodic potential, which arises in an adapted galvanic cell, can be utilized to considerably reduce wear by using 1 molar NaCl (-86 %) and 1 % [C2mim][Cl] (-75 %) aqueous solution as electrolyte when compared to the non-polarized system. In contrast, the galvanic coupling of stainless steel 1RK91 with the more noble copper results in an anodic polarization of the stainless steel leading to excessive wear.

In conclusion, the formation of electric double-layers, tribochemical reactions, chemisorption and interfacial electro-kinetic effects are identified as the mechanisms for this behavior and have been discussed elsewhere [3-5]. In the ionic liquid solution, cations adsorb along the surface at negative potentials and arrange into ion/ion pair layers near the interface and form thin lubricant layers [5]. This arrangement is more pronounced at higher polarization and so it is possible to control friction and wear in this electroactive system.


References

[1] Nature Materials, 2010, 9, 8 – 10.

[2] Phys. Chem. Chem. Phys., 2015, 17, 10339.

[3] Chem. Commun., 2014, 50, 4368.

[4] Proc. Inst. Mech. Eng. N J. Nanoeng. Nanosyst., 2013, 227, 196.

[5] J. Phys. Condens. Matter, 2014, 26, 284115

 

Speaker:
Dr. Tobias Amann
Fraunhofer Institute for Mechanics of Materials
Additional Authors:
  • Dr. Andreas Kailer
    Fraunhofer Institute for Mechanics of Materials IWM
  • Natalie Oberle
    Fraunhofer Institute for Mechanics of Materials IWM
  • Felix Gatti
    University of Freiburg
  • Prof. Dr. Jürgen Rühe
    University of Freiburg