Preparation of chemically functionalized graphene with excellent dispersibility and tribological properties as lubricant additives by microwave-assisted ball milling

Abstract

Despite being regarded as one of the most promising lubricant additives, poor dispersion remains a huge obstacle for graphene applications. To solve this problem, the traditional method is to modify graphene with chemical functionalization under harsh conditions. The present investigation prepared modified reduced graphene oxide by the traditional method (MRGO-1) and microwave-assisted ball milling (MRGO-2). The chemical and structural features of MRGO-1 and MRGO-2 are examined by SEM, TEM, XRD, Raman, FTIR, and TGA analyses. The results indicate the microwave-assisted ball milling enables MRGO-2 to be more efficiently dispersed and functionalized than MRGO-1. MRGO-1 and MRGO-2 were introduced into poly alpha-olefin oil (PAO6) as lubricant additives, and the dispersion and tribological performances were tested. Compared with MRGO-1, the dispersion stability of MRGO-2 is increased by 73.8%. Due to its excellent dispersion performance, MRGO-2 can consistently maintain a low friction coefficient during the friction process, and the average friction coefficient is 49.01% lower than that of MRGO-1. Furthermore, the EDS on the worn area demonstrates the most efficient transfer of MRGO-2 on the friction contact interfaces. Finally, the reasons for the improvement in dispersion stability and tribological properties of graphene by microwave-assisted ball milling are explained.