Figure 6

Lubrication mechanism in (a) PEG steel-steel contact (b) 0.2 mg mL−1 rGO-PEG lubricated contact and (c) 1.0 mg mL−1 rGO-PEG lubricated contact.
Lubrication mechanism in (a) PEG steel-steel contact (b) 0.2 mg mL−1 rGO-PEG lubricated contact and (c) 1.0 mg mL−1 rGO-PEG lubricated contact.