Page 186 - Handbook of Surface Improvement and Modification

11.1 Methods and mechanisms of improvement of the coefficient of friction 181

cient; addition of thickener which probably lubricated surface, decreased it; and cross-
24
linker and filler substantially decreased coefficient of friction. The relationship was
found between film softness and its coefficient of friction (the higher the softness the
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higher the coefficient of friction).
Effects of substrate surface roughness and nano-/micro-particle (titanium dioxide)
25
additive size on friction and wear in lubricated sliding was studied. The macroscopic
25
wear experiments were complemented by atomistic simulation. There was an optimal
particle size that would minimize friction and wear for a given surface roughness (parti-
25
cles after dispersion should be smaller than the average surface roughness). This finding
supported an accepted mechanism suggesting that particles fill valleys of the sliding sur-
faces. Some very small particles formed agglomerates and this did not help in decreasing
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of the friction coefficient.
A combination of graphene wrapped around nanodiamond particles can reduce fric-
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tion to near zero, causing macroscale superlubricity. A dramatic reduction in friction on

Figure 11.23. Schematic of a graphene nanoscroll (center) and TEM images of graphene surrounding nanodia-
monds. Brown circles emphasize the lattice of the diamond core. [Adapted, by permission, from Sealy, C, Nano-
today, 10, 4, 412-3, 2015.]