Effect of acid treatments and surfactant on MWCNTs nanofluids: structural, morphological and thermal conductivity

This study discussed the effect of using three acid treatment methods (Method A, Method B and Method C) to introduce the surface oxygen functional group (SOFG) on multi-walled carbon nanotubes (MWCNTs) for structural, morphological and thermal conductivity performance. The SOFG on the MWCNTs has been characterized by Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy and Field Emission Scanning Electron Microscopy (FESEM). The result shows that the modification with acid treatment significantly affects the degree of defects and surface group functionality of surface oxidized MWCNTs from method B. The preparation of nanofluids using MWCNTs in water based fluids produced from method B (MWCNT-MB) was prepared using two different parameters: with and without polyvinylpyrrolidone (PVP) as surfactant with variable setting of carbon particle concentration from 0.1 wt.% to 1.0 wt.%, and the amount of PVP is 10% of carbon particles at different temperatures (6°C, 25°C, 40°C). The thermal conductivity performance of nanofluids proved that the surface oxidized MWCNTs with PVP enhanced thermal conductivity compared to the nanofluid containing MWCNTs without PVP due to the stability and homogenization of nanoparticles. These promising properties of MWCNTs in water-based fluids would enable the nanofluids to be utilized in heat transfer fluid and cooling applications.