Abstract
The present study describes a novel synthesis procedure for a hybrid nanostructure consisting of multiwalled carbon nanotubes (MWNT), hydrogen exfoliated graphene (HEG) and silver nanoparticles. Moreover, synthesis of nanofluids using the above hybrid material and their heat transfer properties are discussed. The hybrid structure of MWNT and HEG (MWNT-HEG) has been synthesized by a simple mixing of MWNT and graphite oxide (GO) followed by exfoliation of this mixture in hydrogen atmosphere. The sample has been characterized with different experimental techniques. After surface functionalization, this hybrid material is decorated with silver nanoparticles (Ag/(MWNT-HEG)) and dispersed in ethylene glycol (EG) without any surfactant. The thermal conductivity and convective heat transfer properties are measured for different volume fractions. An enhancement of ∼8% in thermal conductivity is obtained for a volume fraction of 0.04% at 25°C. The convective heat transfer coefficient of these nanofluids is determined using an in-house fabricated setup. The enhancement in heat transfer coefficient is about 570% for 0.005% volume fraction at the entrance of the pipe for Re = 250.
Highlights
Apart from the 3D bulk allotropes, carbon has nanoallotropes such as 0D fullerene, 1D carbon nanotubes (CNT) and 2D graphene
In our previous study we have shown an enhancement in thermal conductivity of 2% for a volume fraction of 0.08% at 30◦C, using functionalized multiwalled nanotube and functionalized hydrogen induced graphene (f-multiwalled carbon nanotubes (MWNT)+fHEG) hybrid material.[17]
A hybrid nanostructure containing silver nanoparticles, multi walled carbon nanotubes and hydrogen exfoliated graphene has been successfully synthesized by hydrogen exfoliation followed by chemical reduction techniques
Summary
Apart from the 3D bulk allotropes (graphite & diamond), carbon has nanoallotropes such as 0D fullerene, 1D carbon nanotubes (CNT) and 2D graphene. One can tune the properties of a hybrid material by varying the composition of individual constituents In this aspect CNTgraphene hybrid material has been synthesized by different techniques for different applications.[6,7,8,9] Studies suggest that CNT can act like pillars in between the graphene sheets, which avoid the stacking of graphene sheets and increase the total surface area. This indirectly enhances other properties like electrical conductivity, thermal conductivity and mechanical strength. The thermal conductivity of these nanofluids has been studied for different volume fractions at different temperatures
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