The present study investigates the dispersion stability, viscosity, shear stress, and thermal conductivity of multiwalled carbon nanotubes in the presence of gum arabic (MWCNT-GA) as well as functionalized MWCNT with cysteine (MWCNT-Cys) and silver (MWCNT-Ag). To realize good dispersibility and high thermal enhancement, MWCNT were first functionalized by cysteine and then silver ions covalently attached through the thiol group of cysteine. This efficient technique of using a combination of functional silver and cysteine based on MWCNT was developed to enhance the thermal conductivity of the MWCNT suspension. At every sequential step of modification, chemical functionalization was investigated by Fourier transform infrared and Raman spectroscopy. Transmission electron microscope imaging confirmed distribution of silver nanoparticles on the MWCNT surface. Viscosity, shear stress, and thermal conductivity behavior of MWCNT-GA/water, MWCNT-Cys, and MWCNT-Ag/water suspensions were studied under various temperatures and weight concentrations. For the enhancement of thermal conductivity, the results suggest that the covalent functionalization by Ag is more effective than noncovalent functionalization.
