Abstract
Recent studies have reported that adding nanoparticles to graphene enables macroscale superlubricity to be achieved. This study focuses on the role of nanoparticles in achieving superlubricity. First, because graphene nanoscrolls can be formed with nanoparticles as seeds under shear force, the applied load (or shear force) is adjusted to manipulate the formation of graphene nanoscrolls and to reveal the relationship between graphene-nanoscroll formation and superlubricating performance. Second, the load-carrying role of spherical nano-SiO2 particles during the friction process is verified by comparison with an elaborately designed fullerene that possesses a hollow-structured graphene nanoscroll. Results indicate that the incorporated nano-SiO2 particles have two roles in promoting the formation of graphene nanoscrolls and exhibiting load-carrying capacity to support macroscale forces for achieving macroscale superlubricity. Finally, macroscale superlubricity (friction coefficient: 0.006–0.008) can be achieved under a properly tuned applied load (2.0 N) using a simple material system in which a graphene/nano-SiO2 particle composite coating slides against a steel counterpart ball without a decorated diamond-like carbon film. The approach described in this study could be of significance in engineering.
Highlights
Superlubricity refers to a state in which the friction coefficient between two contacting surfaces is less than 0.01 or even close to zero and represents an ideal state sought after by many tribologists [1, 2]
The friction coefficients of pure graphene and graphene/nano-SiO2 particles composite coatings under a low applied load of 0.5 N were shown to be 0.09–0.11 and 0.06–0.07, respectively, which indicates that the addition of nano-SiO2 particles into graphene nanosheets is favorable to reducing friction even at a low contact pressure
Because the formation of graphene nanoscrolls at an increased load is essential for achieving macroscale superlubricity of the as prepared graphene/ nano-SiO2 particle composite coating, it can be inferred that the superlubricating graphene/nano-SiO2 particle composite coating could be applicable to instrumental components working under harsh conditions
Summary
Superlubricity refers to a state in which the friction coefficient between two contacting surfaces is less than 0.01 or even close to zero and represents an ideal state sought after by many tribologists [1, 2]. If a steel ball can be employed as a universal counterpart of superlubricating graphene/ nanoparticle composites, the as simplified tribo-system would help in better understanding the lubrication mechanism and macroscale superlubricity performance of nanocomposites and promote the application of the system. In this manner, the exploration of superlubricity in relation to the indispensable structural factors (e.g., nanoparticles and counterpart ball of the tribo-pair) of friction-reducing graphene/nanoparticle composites will shed light on reducing the friction and wear of mechanical moving parts [32, 33]. Focusing on the roles and the structural parameters of the nanoparticles, this study reports the macroscale tribological properties of graphene/nano-SiO2 particle composite coatings upon sliding against steel balls in terms of superlubricating material design and the practical use of superlubricity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
