785680.fig.007a
(a)
785680.fig.007b
(b)
785680.fig.007c
(c)
Figure 7: Schematic diagram showing separation effect of nanoparticles during rubbing lubricated (a) pure water without nanoparticle; (b) the water with a trace amount of nanoparticles; (c) the water with an appropriate amount of nanoparticles.