Effect of Surface Modifications and Their Reaction Conditions on Multi-Walled Carbon Nanotubes for Thermal Conductive Composite Material

Thermally conductive composite materials were fabricated using Al2O3 and surface-modified MWCNTs on an ETDS matrix. The MWCNT surfaces were modified using a solution containing H2O2 and H2SO4/HNO3 and examined at various reaction times. After surface modification, the ratios of the functional groups introduced were compared. The changes in MWCNT morphology and thermal conductivity were also investigated for various reaction times. It was observed from the results that the MWCNTs exposed to 1 h acid treatment had the highest thermal conductivity without any decrease in their length. Based on the optimum oxidization of MWCNTs, further surface modification was performed using APTES, a silane coupling agent, using two different reactions. After the reaction, large particle aggregations were observed on the amine-terminated MWCNTs, which reacted with a mixture of EtOH and DI water. These agglomerates did not re-disperse after long-time sonication. However, the silanol-terminated MWCNTs were easily dispersed in EtOH via sonication, and their composite materials had outstanding thermal conductivities. Moreover, more amount of MWCNTs were processable using the same Al2O3 and ETDS concentrations, which also led to enhanced thermal conductivities compared to the other surface modification methods.