An experimental study on thermal conductivity enhancement of DI water-EG based ZnO(CuO)/graphene wrapped carbon nanotubes nanofluids

The present study describes a facile synthesis procedure for nanocomposites consisting of 1D carbon nanotubes, 2D graphene and metal-oxide nanoparticles (CuO, ZnO) referred as metal-oxide dispersed on graphene-wrapped carbon nanotubes (CuO/GC and ZnO/GC) nanocomposites. Moreover, nanofluids were prepared by dispersing the above composites and the thermal conductivity of these nanofluids has been measured. Initially, GC was synthesized by a chemical vapor deposition technique using the mixture of graphene oxide (GO) and MmNi3 as catalyst and further purified by removing catalyst impurities and amorphous carbon. Afterwards, synthesis of metal-oxide dispersed on GC nanocomposites has been done. The formation of nanocomposites has been confirmed by X-ray diffraction, scanning electron microscope, and transmission electron microscope. Further, nanofluids were prepared by dispersing nanocomposites (GC, CuO/GC, and ZnO/GC) in de-ionized (DI) water and ethylene glycol (EG) without any functionalization and surfactant. After confirming the stability of nanofluids by zeta potential analysis, thermal conductivity of these nanofluids was measured at different temperatures. GC, ZnO/GC and CuO/GC dispersed DI water based nanofluids show an enhancement of 22.6%, 24.1% and 26.0% for 0.015 vol. % at 50 °C, respectively. Further, an enhancement of 15.5%, 17.7% and 21.2% was observed for GC, ZnO/GC and CuO/GC dispersed EG based nanofluids for 0.015 vol. % at 50 °C, respectively.