▎ 摘　　要

Ultralow friction coefficient in reduced graphene oxide (rGO) nanofluid was observed at high pressure lubrication conditions. High pressure Raman spectroscopic studies of graphene oxide (GO) and rGO in a hydrostatic pressure medium in diamond anvil cell (DAC) showed an increase in G-band linewidth in GO but this value was decreased in rGO at same pressure range due to the defect relaxation in sp(2) networks. Moreover, loss of recovery of G band linewidth in decompression cycles was clearly noticed in both the samples but it was significantly higher in GO due to the irreversible sp(3) into sp(2) planar phase. (C) 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.