Silicone based nanofluids containing functionalized graphene nanosheets

The work presents a method to prepare stable nanofluids containing functionalized graphene nanosheets (FG–silicone oil nanofluids). FG was produced by using a two-step method with 3-glycidoxypropyltrimethoxysilane (KH-570) as functionalization modifier. The nanofluids were prepared by dispersing FG in silicone oil without any surfactant with the assistance of ultrasonication. The functionalization modifier rendered FG to have a good compatibility with silicone oil. Fourier transform infrared spectroscopy, atomic force microscopy, Raman spectroscopy, UV–vis spectroscopy and X-ray diffraction were used to characterize the structures and morphology of FG powder. The results showed that the average thickness of FG nanosheets ranges from 1.1 nm to 2.3 nm. Thermal conductivity of FG–silicone oil nanofluids depended strongly both on temperature and on the weight fraction and increased with the increment in loading. Thermal conductivity of FG–silicone oil nanofluids showed an enhancement of about 5.74% at 20 °C with the weight fraction of 0.07%, while the enhancement ratio was up to 18.9% at 60 °C. The electrical conductivity of nanofluids was also measured and increased with loading.