Effective dispersion of multi-wall carbon nano-tubes in hexadecane through physiochemical modification and decrease of supercooling

Prevention of supercooling is essential for phase change material (PCM) utilization. In this study, multi-wall carbon nano-tube (MWCNT) particles were dispersed in an organic liquid n-hexadecane used to decrease supercooling. Various surfactants were tested as additives to overcome the rapid aggregation and sedimentation of the nanoparticles in the organic liquid. Stable and homogenous dispersion was attained through surface modification of the MWCNT particles with strong acids H2SO4and HNO3, plus the addition of 1-decanol as a surfactant to the organic liquid. Thermal analysis of the n-hexadecane with well dispersed MWCNT particles at concentrations ranging from 0.1% to 10% w/w by differential scanning calorimeter (DSC) indicated that the supercooling of n-hexadecane was significantly decreased with the concentration of 0.1% and 0.5% but only slightly with the concentrations over 1.0%. It appears that well dispersed nanoparticles provided stable foreign nuclei of proper size to promote the heterogeneous nucleation process and accelerate crystallization process, thus the supercooling was significantly reduced. The obvious effects of MWCNT particles on the decrease of supercooling of n-hexadecane provide promising way of improving the performance of system energy efficiency in building cooling and heating applications.