Surfactant-free ionic liquid-based nanofluids with remarkable thermal conductivity enhancement at very low loading of graphene

Abstract

We report for the first time the preparation of highly stable graphene (GE)-based nanofluids with ionic liquid as base fluids (ionic liquid-based nanofluids (Ionanofluids)) without any surfactant and the subsequent investigations on their thermal conductivity, specific heat, and viscosity. The microstructure of the GE and MWCNTs are observed by transmission electron microscope. Thermal conductivity (TC), specific heat, and viscosity of these Ionanofluids were measured for different weight fractions and at varying temperatures, demonstrating that the Ionanofluids exhibit considerably higher TC and lower viscosity than that of their base fluids without significant specific heat decrease. An enhancement in TC by about 15.5% and 18.6% has been achieved at 25 °C and 65 °C respectively for the GE-based nanofluid at mass fraction of as low as 0.06%, which is larger than that of the MWCNT-dispersed nanofluid at the same loading. When the temperature rises, the TC and specific heat of the Ionanofluid increase clearly, while the viscosity decreases sharply. Moreover, the viscosity of the prepared Ionanofluids is lower than that of the base fluid. All these advantages of this new kind of Ionanofluid make it an ideal fluid for heat transfer and thermal storage.

Investigation on the use of graphene oxide as novel surfactant to stabilize weakly charged graphene nanoplatelets

“…It is generally known that the major limitation towards successful application of carbon nanostructures in vast technological domain is associated to its poor dispersion in both aqueous medium and organic solvents [32][33][34]. Several approaches have been studied for the production of stable aqueous suspension of carbon nanotubes (CNT) as well as other carbon allotropes for instance [35][36][37][38][39][40]. Chemical functionalization on nanotube and graphene surfaces via the use highly concentrated acid is a widely adopted technique to increase their solubility [41][42][43][44].…”

Effect of volume concentration and temperature on viscosity and surface tension of graphene–water nanofluid for heat transfer applications

“…Kole et al [23] investigated the effects of particle loading (0.041-0.395 vol%) and temperature (10 and 70°C) on the viscosity of graphene-ethylene glycol-water (70: 30) nanofluids. The results showed that the viscosity of the nanofluid enhanced nearly by 100 % with that of the base fluid, at a loading of 0.395 vol%.…”

“…No obvious change has been observed in the value of the viscosity due to the addition of nanoparticles, and a maximum enhancement of about 5 % for surface tension was obtained at a concentration of 1 g/l at 21°C. Wang et al [30] measured the viscosity of ionic liquid-based nanofluids with graphene and multiwalled carbon nanotubes as suspensions for a temperature range of 25-75°C at very low mass percentages of 0.03 and 0.06 %. A viscosity decrement of 81.32 and 78.66 % was observed for a volume concentration of 0.03 % of graphene and MWCNT nanoparticles, respectively, when the temperature increased from 25 to 75°C.…”

Study on the Thermal Conductivity Characteristics of Graphene Prepared by the Planetary Ball Mill

“…The nano-sized powders of copper [3], copper oxide [4], titanium oxide [5], aluminum oxide [6], and carbon nanotube (CNT) [7][8][9], the heat conductivities of which are higher than general fluids are prepared and dispersed into such fluid to achieve an improved efficiency of heat conductivity. Recently, the graphene (GN) [10][11][12][13][14][15] of high heat conductivity has been focused upon as one of the nano-sized particles that can be added to such nano-fluids.…”