Plasma nanocoated carbon nanotubes for heat transfer nanofluids

Abstract

Multi-wall carbon nanotubes (CNTs) were plasma-treated using glow discharges of argon, oxygen andmethane/oxygen mixtures and then dispersed into a base fluid of water. It was found that proper plasmatreatments of CNTs using nanoscale plasma coatings significantly improve the dispersionand stabilize the suspension of CNTs in the base fluid. With 0.01 vol% addition ofplasma-treated CNTs, a 25% initial increase in thermal conductivity was achievedand a stabilized 20% increase was observed with the resulting nanofluids after 5days’ settling. It should particularly be pointed out that such a large increasein thermal conductivity was achieved when plasma-treated CNTs were stablydispersed in water without adding any dispersing agents or surfactants. Surfacemodification of the CNTs was confirmed by Raman spectroscopy and ultra-thin (∼2 nm) plasma nanocoatings were noted on the treated CNT surfaces by transmission electronmicroscopy (TEM).