Abstract
Hexagonal boron nitride nanosheets (h-BNNSs), with a crystal lattice structure similar to graphene by over 98%, exhibit good lubrication properties as lubricant additives. However, the poor dispersibility in solvents has limited their wide practical applications as lubricant additives. In the present report, water dispersible Pebax functionalized h-BNNSs (Pebax-BNNSs) have been prepared through a one-step solvent-free mechanical exfoliation process which relies on a simple exfoliation of h-BN layers by shearing force in molten Pebax at 200 °C. In this process, Pebax molecules can synchronously react with the dangling bonds formed during the exfoliation process to achieve in situ functionalization of h-BNNSs. The reciprocating friction tests demonstrate that the as-obtained Pebax-BNNSs possess excellent antifriction and antiwear performance as water-based lubricant additive with a low concentration of 0.3 mg/mL under atmospheric condition. The friction coefficients can be <0.01, achieving superlubrication. Further systematical investigations on the wear traces, wear debris, and counter balls propose a “dispersion-compensation-filling repairment” friction mechanism. All these results demonstrate that h-BNNSs can achieve superlubrication as water-based lubricant additives via facile surface modification, making them very promising candidates as lubricant additives in practical applications.
Highlights
Friction and wear remain the primary modes of mechanical energy dissipation in many mechanical, electromechanical, and biological systems, resulting in unwanted wastage of resources and energy[1] as well as 80% of machinery component failure.[2]
The FESEM characterization was performed on the surfaces of the wear scars to explore the friction mechanism of the Pebax-BNNS/ water dispersion as a lubricant
The wear track with a width of about 470 μm can be observed for the friction condition under dry friction, and a lot of wear debris accumulated on both sides of the track (Fig. S6a)
Summary
Friction and wear remain the primary modes of mechanical energy dissipation in many mechanical, electromechanical, and biological systems, resulting in unwanted wastage of resources and energy[1] as well as 80% of machinery component failure.[2]. The Raman spectrum (Fig. 2g) of the original h-BN shows a band at 1366 cm−1, extremely closing to 1365.8 cm−1 for typical h-BN, which can be attributed to the E2g vibration mode of h-BN.[27,28] Different from the original h-BN, a slight redshift of 12 cm−1 can be observed in the Raman spectrum of the as-obtained products This result suggests that h-BN has been exfoliated to a few layered nanosheet predominant products since this feature can reduce the interlayer interactions and shorten the B–N bonds.[29] Another reason may be that the exfoliated h-BNNSs have been functionalized by Pebax, and the introduction of Pebax molecules cause the weakness and redshift of the Raman spectrum. The friction coefficients are basically consistent in the steady-state npj 2D Materials and Applications (2019) 28
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