Deformation and tribology of multi-walled hollow nanoparticles

Multi-walled hollow: nanoparticles made from tungsten disulphide (WS2) show exceptional tribological performance as additives to liquid lubricants due to effective transfer of low shear strength material onto the sliding surf aces. Using a scaling approach based on continuum elasticity theory for she lls and pairwise summation of van der Waals interactions? we show that van der Waals interactions cause strong adhesion to the substrate which favors release of delaminated layers onto the surfaces. For large and thin nanopar ticles, van der Waals adhesion can cause considerable deformation and subse quent delamination. For the thick WS2 nanoparticles, deformation due to van der Waals interactions remains small and che main mechanism for delaminati on is pressure which in fact leads to collapse beyond a critical value. We also discuss the effect of shear flow on deformation and rolling on the sub strate.