Skip to main content
Log in

Frictional characteristics of molecular length ultra-thin boundary adsorbed films

  • Brief Notes and Discussions
  • Published:
Meccanica Aims and scope Submit manuscript

Abstract

The paper presents measurements of friction of any ultra-thin film entrained into the contact of a pair of very smooth specimen subjected to entrainment in a converging micro-wedge of a special-purpose micro-tribometer. An ultra-thin film is expected to form at the boundary solids through adsorption of boundary active molecules. Fluids with linear and branched molecules are used in the investigation. It is found that the frictional characteristics of these films can be adequately described through use of Eyring thermal activation energy and a potential energy barrier to sustain conjunctional sliding motion. The combined experimental measurement and the simple activation energy approach shows that the thin molecular adsorbed films act like hydro Langmuir–Blodgett layers, the formation and frictional characteristics of which are affected by the competing mechanisms of adsorption, forced molecular re-ordering and discrete-fashion drainage through the contact by the solvation effect. This process is a complex function of the contact sliding velocity as well as a defined Eyring activation density (packing density of the molecules within the conjunction). It is shown that the contribution of solvation to friction is in the form of energy expended to eject layers of lubricant out of the contact, which unlike the case of micro-scale hydrodynamic films, is not a function of the sliding velocity.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7

Similar content being viewed by others

Abbreviations

k B :

Boltzmann constant (0.008314 kJ/mol/K)

v :

Sliding velocity (m/s)

v 0 :

Characteristic velocity (m/s)

E :

Barrier height (kJ/mol)

P :

Contact pressure (Pa)

Q :

Process activation energy (kJ/mol)

T :

Contact temperature (K)

ϕ :

Shear stress activation volume (m3/mol)

τ :

Shear stress (Pa)

τ 0 :

Pressure dependent Eyring shear stress (Pa)

τ 1 :

Sliding velocity dependent Eyring shear stress (Pa)

θ :

Rate of change for friction at a given sliding velocity for constant applied load (−)

ξ :

Rate of change for friction at an applied load for constant sliding velocity (−)

Ω:

Pressure activation volume (m3/mol)

References

  1. Lifshitz EM (1956) The theory of molecular attractive forces between solids. Sov Phys JETP 2:94–110

    MathSciNet  Google Scholar 

  2. Gohar R, Rahnejat H (2008) Fundamentals of tribology. Imperial College Press, London

    Book  MATH  Google Scholar 

  3. Israelachvili J (1992) Intermolecular and surface forces, 2nd edn. Academic Press, New York

    Google Scholar 

  4. Attard P, Parker JL (1992) Oscillatory solvation forces: a comparison of theory and experiment. J Phys Chem 96(12):5086–5093

    Article  Google Scholar 

  5. Lim R, O’Shea SJ (2002) Solvation forces in branched molecular liquids. Phys Rev Lett 88(24):246101

    Article  ADS  Google Scholar 

  6. Tabor D, Winterton RHS (1968) Surface forces: direct measurement of normal and retarded van der Waals forces. Nature 219:1120–1121

    Article  ADS  Google Scholar 

  7. Horn RG, Israelachvili JN (1981) Direct measurement of structural forces between two surfaces in a nonpolar liquid. J Chem Phys 75(3):1400–1412

    Article  ADS  Google Scholar 

  8. Chan DYC, Horn RG (1985) The drainage of thin liquid films between solid surfaces. J Chem Phys 83(10):5311–5324

    Article  ADS  Google Scholar 

  9. Lim RYH, O’Shea SJ (2004) Discrete solvation layering in confined binary liquids. Langmuir 20(12):4916–4919

    Article  Google Scholar 

  10. Matsuoka H, Kato T (1997) An ultrathin liquid film lubrication theory—calculation method of solvation pressure and its application to the EHL problem. J Tribol 119:217–226

    Article  Google Scholar 

  11. Al-Samieh M, Rahnejat H (2001) Ultra-thin lubricating films under transient conditions. J Phys D Appl Phys 34:2610–2621

    Article  ADS  Google Scholar 

  12. Abd Al-Samieh MF, Rahnejat H (2001) Nano-lubricant film formation due to combined elastohydrodynamics and surface force action under isothermal conditions. Proc IMechE Part C J Mech Eng Sci 215:1019–1029

    Article  Google Scholar 

  13. Al-Samieh M, Rahnejat H (2002) Physics of lubricated impact of a sphere in a plate in a narrow continuum to gaps of molecular dimensions. J Phys D Appl Phys 35:2311–2326

    Article  ADS  Google Scholar 

  14. Chong WWF, Teodorescu M, Rahnejat H (2011) Effect of lubricant molecular rheology on formation and shear of ultra-thin surface films. J Phys D Appl Phys 44(16):165302

    Article  ADS  Google Scholar 

  15. Chong WWF, Teodorescu M, Rahnejat H (2012) Formation of ultra-thin bi-molecular boundary adsorbed films. J Phys D Appl Phys 45(11):115303

    Article  ADS  Google Scholar 

  16. Chong WWF, Teodorescu M, Rahnejat H (2012) Physio-chemical hydrodynamic mechanism underlying the formation of thin adsorbed boundary films. Faraday Discuss 156:123–136

    Article  Google Scholar 

  17. Mitchell DJ, Ninham BW, Pailthorpe BABA (1977) Hard sphere structural effects in colloid systems. Chem Phys Lett 51(2):257–260

    Article  ADS  Google Scholar 

  18. Henderson D, Lozada-Cassou M (1986) A simple theory for the force between spheres immersed in a fluid. J Colloid Interface Sci 114(1):180–183

    Article  Google Scholar 

  19. Israelachvili JN (1973) Thin-film studies using multiple-beam interferometry. J Colloid Interface Sci 44:259272

    Article  Google Scholar 

  20. Yoshizawa H, Chen YL, Israelachvili JN (1993) Fundamental mechanisms of interfacial friction. 1. Relation between adhesion and friction. J Phys Chem 97:41284140

    Google Scholar 

  21. Israelachvili JN, Tabor D (1993) Shear properties of molecular films. Nat Phys Sci 241:148149

    Google Scholar 

  22. Yoshizawa H, Chen YL, Israelachvili JN (1993) Recent advances in molecular understanding of adhesion, friction and lubrication. Wear 168:161–166

    Article  Google Scholar 

  23. Yoshizawa H, Israelachvili JN (1993) Fundamental mechanisms of interfacial friction. 2. Stickslip friction of spherical and chain molecules. J Phys Chem 97:1130011313

    Google Scholar 

  24. Xie G, Luo J, Guo D, Liu S (2010) Nanoconfined ionic liquids under electric fields. Appl Phys Lett 96:043112

    Article  ADS  Google Scholar 

  25. Xiao H, Guo D, Liu S, Pan G, Lu X (2011) Film thickness of ionic liquids under high contact pressures as a function of alkyl chain length. Tribol Lett 41:471–477

    Article  Google Scholar 

  26. Ku ISY, Choo JH, Reddyhoff T, Holmes AS, Spikes HA (2010) A novel tribometer for the measurement of friction in MEMS. Tribol Int 43:1087–1090

    Article  Google Scholar 

  27. Gavrilenko VP, Novikov Yu A, Rakov AV, Todua PA (2009) Measurement of thickness of native silicon dioxide with a scanning electron microscope. In: SPIE NanoScience Engineering, pp 740507–740507

  28. Ku ISY (2011) Lubrication of high sliding micromachines. Ph.D. thesis, Imperial College London

  29. Reddyhoff T, Ku ISY, Holmes AS, Spikes HA (2011) Friction modifier behaviour in lubricated MEMS devices. Tribol Lett 41:239–246

    Article  Google Scholar 

  30. Briscoe BJ, Evans DCB (1982) The shear properties of Langmuir–Blodgett layers. Proc R Soc Ser A Math Phys Sci 380(1779):389–407

    Article  ADS  Google Scholar 

  31. He M, Blum AS, Overney G, Overney RM (2002) Effect of interfacial liquid structuring on the coherence length in nanolubrication. Phys Rev Lett 88(15):154302

    Article  ADS  Google Scholar 

  32. Granick S, Demirel L, Cai LL, Peanasky J (1995) Soft matter in a tight spot: nanorheology of confined liquids and block copolymers. Isr J Chem 35:3276

    Article  Google Scholar 

  33. Lim R, O’Shea SJ (2002) Solvation forces in branched molecular liquids. Phys Rev Lett 88:246101

    Article  ADS  Google Scholar 

  34. Teodorescu M, Balakrishnan S, Rahnejat H (2006) Physics of ultra-thin surface films on molecularly smooth surfaces. Proc IMechE Part N J Nanoeng Nanosyst 220:7–19

    Google Scholar 

Download references

Acknowledgments

The authors acknowledge sponsorship provided by the EPSRC through Grant Nos. EP/D04099X and EP/L001624/1 (covering experimental work) along with the EPSRC ENCYCLOPAEDIC program Grant (covering theoretical work).

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to W. W. F. Chong.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Ku, I.S.Y., Chong, W.W.F., Reddyhoff, T. et al. Frictional characteristics of molecular length ultra-thin boundary adsorbed films. Meccanica 50, 1915–1922 (2015). https://doi.org/10.1007/s11012-015-0186-0

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11012-015-0186-0

Keywords

Navigation