Nanoparticles in lubrication KEM-31.5530 Nanoparticles, 3.5.2011Timo J. Hakala
Contents • Introduction to lubrication • Important lubricant properties • Nanoparticles in lubrication • Some examples
Lubrication regimes • Lubrication can be divided in three regimes • Boundary lubrication • Thin film lubrication • Mixed lubrication • Elastohydrodynamic lubrication • Hydrodynamic lubrication Coles J.M. Chang D.P. and Zauscher S. Molecular mechanisms of aqueous boundary by mucinous glycoproteins, Current Opinion in Colloid & Interface Science, 15, 2010, 406-416 Stachowiak, G.W. and Batchelor, A.W., Engineering Tribology, 3rd edition, USA, 2005, Elsevier Inc., 801 p.
Lubricants • Lubricants consist of base liquid and additives which improve the lubricating properties • Base liquids can be e.g. • Mineral oil • Synthetic oil • Emulsions and aqueous lubricants • Greases • Additives are used to improve specified properties of lubricant Stachowiak, G.W. and Batchelor, A.W., Engineering Tribology, 3rd edition, USA, 2005, Elsevier Inc., 801 p.
Additives in lubricants • Additives are used to improve the properties of lubricants • Wear and friction properties • Oxidation resistance • Control of corrosion • Control of contamination by reaction products (wear particles etc) • Control viscosity • Viscosity often temperature dependent • Reducing pour point • Inhibition of foam formation Stachowiak, G.W. and Batchelor, A.W., Engineering Tribology, 3rd edition, USA, 2005, Elsevier Inc., 801 p.
Traditional boundary lubrication additives • Can be divided into three groups • Adsoprtion or boundary additives • Anti-wear additives • Extreme pressure additives • Additives adsorb on the surface by chemisorption, physisorption or chemical reaction • e.g. formation of FeS Stachowiak, G.W. and Batchelor, A.W., Engineering Tribology, 3rd edition, USA, 2005, Elsevier Inc., 801 p. Holmberg, K. & Matthews, A. Coatings Tribology, Properties, Mechanisms, Techniques and Applications in Surface Engineering, 2nd ed., Elsevier, The Netherlands, 2009, 560p
Nanoparticles in boundary lubrication • In past few years the studies of nanoparticles in lubrication has increased significantly • The amount of different nanoparticles studied is great; • Oxides • Borates • Sulfides • Carbon nanoparticles Mosleh M., Atnafu N.D., Belk J.H. and Nobles O.M. Modification of sheet metal forming fluids with dispersed nanoparticles for improved lubrication, Wear, 2009, 267; 1220-1225
Hypothesis of mechanisms • There are some mechanisms presented in the literature for the friction and wear reduction • Formation of solid lubricant film • Rolling of the nanoparticles between moving surfaces • Reducing the asperity contacts by filling the valleys (smoothening the surface) • Shearing of trapped nanoparticles at the interface (no adhered film) • Hardening the contacting surfaces • Changing the viscosity of the lubricant Mosleh M., Atnafu N.D., Belk J.H. and Nobles O.M. Modification of sheet metal forming fluids with dispersed nanoparticles for improved lubrication, Wear, 2009, 267; 1220-1225 Chou C-C. and Lee S-H. Tribological behavior of nanodiamond-dispersed lubricants on carbon steels and aluminum alloy, Wear, 2010, 757-762 Cizaire L., Vacher B.,Mogne T.L., Martina J.M., Rapoport L., Margolinc A.,Tennec R. Mechanisms of ultra-low friction by hollow inorganic fullerene-like MoS2 nanoparticles, Surface and coating technology, 2002, 282-287
Copper nanoparticles • Reducing friction by forming a physical film on the surface • Smoothening the surface Y. Choi, C. Lee, Y. Hwang, M. Park, J. Lee, C. Choi b, M. Jung, Tribological behavior of copper nanoparticles as additives in oil , Current Applied Physics 9 (2009) e124–e127
TiO2 nanoparticles • Rolling effect between the moving surfaces Kao M-J. and Lin C-R. Evaluating the role of spherical titanium oxide nanoparticles in reducing friction between two pieces of cast iron, Journal of Alloys and Compounds, 483, 2009, 456–459
Decrease in coefficient of friction by ZrO2 nanoparticles • 20# is base oil • Reduction in coefficient of friction over 50% Ma S., Zheng S., Cao D. and Guo H. Anti-wear and friction performance of ZrO2 nanoparticles as lubricant additive, Particuology, 8, 2010, 468–472
Summary • There are some promising results of reducing wear and friction by adding the nanoparticles in oil • Concentrations of nanoparticles are usually 0.1 – 5 % • More nanoparticles will increase wear • Surfactants needed to avoid large aggregates • However, the mechanisms for wear and friction reduction are still unclear
Thank you! Timo J. Hakala firstname.lastname@example.org