by Dr. Nitya Nand Gosvami, IIT Delhi

Abstract:

Tribology of sliding surfaces are of great importance for various engineering applications including gears, bearings, automotive engine components, hard disk read/write mechanisms and micro- & nano-electromechanical systems etc. A lack of fundamental insight of tribological processes hinders the advancement of such technologies. Macroscopic contacts often involve interactions between nanoscale asperities owing to the surface roughness of the components. Observing and understanding the nanoscale mechanisms at play is inhibited by the hidden nature of the buried interface. Recent advances in novel experimental methods based on atomic force microscopy (AFM) are enabling such interactions to be studied with unprecedented resolution and insight.

I will discuss the development and application of a novel in situ experimental approach using AFM for investigating the nanoscale tribological properties of lubricant additives. The technique allows measurements of friction as well as direct imaging of the sliding interface between two sliding surfaces in single-asperity as well as in multi-asperity contact geometry. Using this technique, I will present results on zinc dialkyldithiophosphate (ZDDP) lubricant additives, used nearly universally in automotive engine oils. The unrivaled wear protection of ZDDPs via formation of a protective film makes them essential to lubricant performance. The growth mechanisms of such films are still poorly understood, particularly for lightweight alloys due to the complexity of the macroscopic multi-asperity sliding interfaces. Greater understanding of the formation of these films is essential to enable rational design of more environmentally-friendly and energy-efficient engine oil formulations. I’ll also discuss recent investigations of tribology of 2D materials where we demonstrate self-generation of lubricious graphene based tribochemical films on silica glass which reduces scratch induced surface damage. Finally, in situ nanotribology of WS₂ monolayer, which are excellent solid lubricants, will be discussed where role of defects, ageing and morphology of the monolayer plays and important role on friction and wear behaviour.

 

References:

[1]          H. Rai et al., Appl. Surf. Sci., vol. 605, p. 154783, 2022.

[2]          S. Sahoo, O. P. Khatri, N. A. Krishnan, and N. N. Gosvami, ACS Appl. Nano Mater., vol. 5, no. 4, pp. 4812–4822, 2022.

[3]          P. Mittal, H. Rai, S. Kumari, O. P. Khatri, and N. N. Gosvami, Appl. Surf. Sci., vol. 595, p. 153520, 2022.

[4] S. Kasimuthumaniyan, N. N. Gosvami, and N. A. Krishnan, Ceram. Int., vol 47, no. 15, p. 20821-20843, 2021.

[5]          P. Mittal, Y. Maithani, J. P. Singh, and N. N. Gosvami, Tribol. Int., p. 106419, 2020.

[6]          N. N. Gosvami, J. Ma, and R. W. Carpick, Tribol. Lett., vol. 66, no. 4, p. 154, 2018.

[7]          N. N. Gosvami, J. A. Bares, F. Mangolini, A. R. Konicek, D. G. Yablon, and R. W. Carpick, Science, vol. 348, no. 6230, pp. 102–106, 2015.