Preparation and tribological properties of eco-friendly as-exfoliated graphene in grease

The exfoliation for few layers of graphene was prospective for scale output due to low cost and processable advantages. However, the massive production had some obstacles such as high pollution with organics and harmful elements and use of rare metal. Herein, we developed a facile and eco-friendly expansion-reduction exfoliation method to prepare graphene from graphene oxide (GO) with aid of oxalic acid(H2C2O4). The as-exfoliated graphene nanosheets possessed a 10-layered thickness and large lateral size of approximately 0.5 mu m. As a prospective application, the as-exfoliated graphene nanosheets were conducted as additive in the grease for the sake of antifriction and antiwear. The results showed that the friction reduction and wear resistant properties were improved by 35.8% and 32.8%, respectively. The friction reducing mechanism of graphene in grease was proposed due to forming a protective film.