Bottom-up synthesis of few-layered graphene powders and their applications as efficient lubricating and electromagnetic shielding additives

The unique properties of graphene powders strongly depend on their morphologies and synthetic routes. Herein, a general bottom-up approach of synthesizing graphene powders was developed via pyrolysis of self-polymerized compounds of small aromatic molecules with bis-amino groups onto NaCl microcrystals. The key properties of graphene powders including the thickness of graphene layers, surface area and electronic conductivity can be effectively modulated by adjusting mass ratios of monomer and NaCl, and pyrolysis temperature. Typical graphene powders prepared using m-phenylenediamine as precursor with various mass ratios of NaCl at 1500 celcius process a high specific surface area up to 545 m2 g-1, high powder conductivity (up to 1351 S m-1 at 20 MPa) and the thickness <3.0 nm. Attributed to these specific properties, the graphene powders exhibit outstanding performance as lubrication enhancing and electromagnetic shielding additives, demonstrating their practical application prospect wherein graphene powders can significantly enhance the friction-reduction and anti-wear capacities of the base oil with significant wear volume loss of 47.0% and friction coefficient reduction of 15.5% respectively at few amount addition of graphene (0.3 wt%), while only 20 wt% incorporation also demonstrates high average electromagnetic shielding effect of up to 86.4 dB in the electromagnetic waves range of 8-18 GHz.