▎ 摘　　要

A cost-effective method is essential for the applications of graphene platelets (GnPs) in polymer processing industry. Herein, a simple microwave expansion method was introduced to prepare graphene platelets (GnPs) of 11.7 +/- 4.3 nm in thickness. By controlling the concentration of nitric acid, the surface of GnPs was tuned to be hydrophilic without causing severe damage to their structural integrity; the modified GnPs had thickness of 4.6 +/- 2.1 nm, Raman I-D/I-G ratio of 0.09 and electrical conductivity of 570 S cm(-1). The platelets' high crystallinity before and after the surface modification was proved by TEM and SAED analysis. A percolation threshold of electrical conductivity was found to be 0.89 vol% for poly (vinyl alcohol)/modified GnP nanocomposites. The platelets at 0.5 vol% improved tensile strength by 91.1% and Young's modulus by 66.7% due to relatively uniform dispersion and strong interfacial interactions with the matrix.