In the study, researchers from Penn State University, US, compared carbon morphology, surface chemistry and graphitic structure to determine the factors that contribute to increased thermal conductivity. Nanoscale carbons were shown as being effective in boosting heat transfer. Moreover they can be rendered hydrophilic to form a water-based suspension. To measure the thermal conductivity, a new parallel plate cell was also designed and fabricated to circumvent problems associated with traditional hot wire techniques.

Through comparisons between nascent and functionalized forms of these MWNTs, interfacial (molecular) ordering was shown to be the major factor responsible for thermal conductivity enhancement. Surface oxygen groups facilitate hydrogen bonding with water molecules in close proximity. This bonding accelerates heat transfer between the nanocarbon and surrounding fluid, accounting for the observed increase in thermal conductivity. The next steps include testing other fluid combinations and tailoring the nanocarbon morphologies and surface chemistries to achieve enhanced interaction with the carrier fluid.