Relating Tribological Performance and Tribofilm Formation to the Adsorption Strength of Surface-Active Precursors
- 66 Downloads
Abstract
Mechanochemical reactions induced by external stress provide a unique approach for in situ synthesis of carbon tribofilms that can improve friction and wear performance. In this work, we studied how tribofilm formation and tribological performance might be related to the adsorption strength of three additives in polyalphaolefin (PAO4) as base oil, viz., cyclopropanecarboxylic acid (CPCa), cyclopropanemethanol (CPMA), and 1-cyclopropylethanol (CPEA) as characterized by two different surface-active groups –COOH and –OH. Tribo-testing results reveal that addition of 2.5 wt% CPCa to PAO4 gave the lowest friction coefficient and wear volume. FTIR and Raman analysis demonstrate substantial tribofilm formation only in the case when CPCa was used as the oil additive, not CPMA or CPEA, in spite of the fact that all three additives contain the same metastable cyclopropane ring. Thermogravimetric analysis and molecular dynamics simulations indicate the stronger adsorption of CPCa on the iron oxide surface compared with CPMA and CPEA. Weak adsorption of the latter molecules results in their desorption from the surface due to flash heating during tribotesting before they have the chance to participate in mechanochemical reactions required for tribofilm formation. The stronger binding of CPCa to the steel surface is a necessary condition for this type of surface mechanochemistry and appears critical to the efficient formation of carbon-containing tribofilms under our tribo-testing conditions.
Keywords
Carbon tribofilm Adsorption strength TribochemistryNotes
Acknowledgements
The authors would like to thank the support from the US National Science Foundation (Grant No. CMMI-1662606). We thank Valvoline for providing PAO lubricants and Prof. Seong H. Kim for critical reading of this manuscript. This work made use of the Keck-II Facility of Northwestern University’s NUANCE Center, which has received support from the Keck Foundation, the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the Materials Research Center (NSF DMR-1121262), the McCormick Research Catalyst Awards Fund, Grant No. 10038293, and the International Institute for Nanotechnology (IIN) at Northwestern University. We would like to thank Dr. Xinqi Chen for his help in conducting FTIR spectroscopy. Hongxing Wu and Qiang Ma would also like to acknowledge the scholarship support from China Scholarship Council (CSC, Nos. 201606280181 and 201806280152 respectively). This research was supported in part through the computational resources and staff contributions provided for the Quest high performance computing facility at Northwestern University, which is jointly supported by the Office of the Provost, the Office for Research, and Northwestern University Information Technology.
References
- 1.Hickenboth, C.R., Moore, J.S., White, S.R., Sottos, N.R., Baudry, J., Wilson, S.R.: Biasing reaction pathways with mechanical force. Nature 446(7134), 423 (2007)CrossRefGoogle Scholar
- 2.Ribas-Arino, J., Marx, D.: Covalent mechanochemistry: theoretical concepts and computational tools with applications to molecular nanomechanics. Chem. Rev. 112(10), 5412–5487 (2012)CrossRefGoogle Scholar
- 3.Yeon, J., He, X., Martini, A., Kim, S.H.: Mechanochemistry at solid surfaces: polymerization of adsorbed molecules by mechanical shear at tribological interfaces. ACS Appl. Mater. Interfaces 9(3), 3142–3148 (2017)CrossRefGoogle Scholar
- 4.Tysoe, W.: On stress-induced tribochemical reaction rates. Tribol. Lett. 65(2), 48 (2017)CrossRefGoogle Scholar
- 5.Zhang, J., Spikes, H.: On the mechanism of ZDDP antiwear film formation. Tribol. Lett. 63(2), 24 (2016)CrossRefGoogle Scholar
- 6.Gosvami, N., Bares, J., Mangolini, F., Konicek, A., Yablon, D., Carpick, R.: Mechanisms of antiwear tribofilm growth revealed in situ by single-asperity sliding contacts. Science 348(6230), 102–106 (2015)CrossRefGoogle Scholar
- 7.He, X., Kim, S.H.: Mechanochemistry of physisorbed molecules at tribological interfaces: molecular structure dependence of tribochemical polymerization. Langmuir 33(11), 2717–2724 (2017)CrossRefGoogle Scholar
- 8.He, X., Barthel, A.J., Kim, S.H.: Tribochemical synthesis of nano-lubricant films from adsorbed molecules at sliding solid interface: tribo-polymers from α-pinene, pinane, and n-decane. Surf. Sci. 648, 352–359 (2016)CrossRefGoogle Scholar
- 9.He, X., Kim, S.H.: Surface chemistry dependence of mechanochemical reaction of adsorbed molecules-an experimental study on tribopolymerization of α-pinene on metal, metal oxide, and carbon surfaces. Langmuir 34(7), 2432–2440 (2018)CrossRefGoogle Scholar
- 10.Khajeh, A., He, X., Yeon, J., Kim, S.H., Martini, A.: Mechanochemical association reaction of interfacial molecules driven by shear. Langmuir 34(21), 5971–5977 (2018)CrossRefGoogle Scholar
- 11.Do, J.-L., Friščić, T.: Mechanochemistry: a force of synthesis. ACS Central Sci. 3(1), 13–19 (2016).CrossRefGoogle Scholar
- 12.Andersen, J.M., Mack, J.: Decoupling the Arrhenius equation via mechanochemistry. Chem. Sci. 8(8), 5447–5453 (2017)CrossRefGoogle Scholar
- 13.Johnson, B., Wu, H., Desanker, M., Pickens, D., Chung, Y.-W., Wang, Q.J.: Direct formation of lubricious and wear-protective carbon films from phosphorus-and sulfur-free oil-soluble additives. Tribol. Lett. 66(1), 2 (2018)CrossRefGoogle Scholar
- 14.Lenhardt, J.M., Ong, M.T., Choe, R., Evenhuis, C.R., Martinez, T.J., Craig, S.L.: Trapping a diradical transition state by mechanochemical polymer extension. Science 329(5995), 1057–1060 (2010)CrossRefGoogle Scholar
- 15.Wang, J., Kouznetsova, T.B., Craig, S.L.: Single-molecule observation of a mechanically activated cis-to-trans cyclopropane isomerization. J. Am. Chem. Soc. 138(33), 10410–10412 (2016)CrossRefGoogle Scholar
- 16.Jahanmir, S., Beltzer, M.: Effect of additive molecular structure on friction coefficient and adsorption. J. Tribol. 108(1), 109–116 (1986)CrossRefGoogle Scholar
- 17.Simič, R., Kalin, M., Kovač, J., Jakša, G.: Adsorption of alcohols and fatty acids onto hydrogenated (aC: H) DLC coatings. Appl. Surf. Sci. 363, 466–476 (2016)CrossRefGoogle Scholar
- 18.Fursey, A.: Oxide films on mild steel. Nature 207(4998), 747 (1965)CrossRefGoogle Scholar
- 19.Plimpton, S.: Fast parallel algorithms for short-range molecular dynamics. JCoPh 117(1), 1–19 (1995)Google Scholar
- 20.Van Duin, A.C., Dasgupta, S., Lorant, F., Goddard, W.A.: ReaxFF: a reactive force field for hydrocarbons. J. Phys. Chem. A 105(41), 9396–9409 (2001)CrossRefGoogle Scholar
- 21.Kyung, S.Y., Hyunwook, K., Chenyu, Z., Vasenkov, A.V., Van Duin, A.C.T.: Development and validation of a ReaxFF reactive force field for Fe/Al/Ni alloys: molecular dynamics study of elastic constants, diffusion, and segregation. J. Phys. Chem. A 116(49), 12163–12174 (2012).CrossRefGoogle Scholar
- 22.Obaidur, R., Van Duin, A.C.T., Goddard, W.A., Doren, D.J.: Development of a ReaxFF reactive force field for glycine and application to solvent effect and tautomerization. J. Phys. Chem. B 115(2), 249–261 (2011)CrossRefGoogle Scholar
- 23.Stukowski, A.: Visualization and analysis of atomistic simulation data with OVITO–the open visualization tool. Modell. Simul. Mater. Sci. Eng. 18(1), 015012 (2009)CrossRefGoogle Scholar
- 24.Wu, H., Khan, A.M., Johnson, B.A., Sasikumar, K., Chung, Y.-W., Wang, Q.J.: Formation and nature of carbon-containing tribofilms. ACS Appl. Mater. Interfaces 11(17), 16139–16146 (2019)CrossRefGoogle Scholar
- 25.Barthel, A.J., Combs, D.R., Kim, S.H.: Synthesis of polymeric lubricating films directly at the sliding interface via mechanochemical reactions of allyl alcohols adsorbed from the vapor phase. RSC Adv. 4(50), 26081–26086 (2014)CrossRefGoogle Scholar
- 26.Martin, R., Kim, M., Franklin, A., Bian, Y., Weaver, J.F. Adsorption and oxidation of propane and cyclopropane on IrO 2 (110). PCCP 20(46), 29264–29273 (2018).CrossRefGoogle Scholar
- 27.Javahery, G., Petrie, S., Wang, J., Bohme, D.K.: A theoretical study on the cyclopropane adsorption onto the copper surfaces by density functional theory and quantum chemical molecular dynamics methods. J. Mol. Catal. A 220(2), 189–198 (2004)CrossRefGoogle Scholar
- 28.Hoffmann, F.M., Felter, T.E., Weinberg, W.H.: The orientation and symmetry of adsorbed cyclopropane on Ru(001) measured by off specular high resolution electron energy loss spectroscopy and angular resolved photoelectron spectroscopy. J. Chem. Phys. 76(7), 3799–3808 (1982)CrossRefGoogle Scholar