Boron nitride nanotube (BNNT) consists of boron and nitrogen atoms arranged in a hexagonal network. These light atoms and a symmetrical crystal structure gives rise to molecular fast lattice vibration (phonon). Moreover, the tubular nanostructure of BNNT also assists faster phonon propagation.
Phonon propagation dominates the thermal conductivity in electrically insulative fillers. Thus, theoretically BNNT shows the highest thermal conductivity among the insulative fillers, and it would be one of the promising candidates for thermal management applications.
As the number of tube-wall in BNNT is less, much higher thermal conductivity is expected due to lesser phonon scattering between walls. BNNT synthesized by Inductively Coupled Plasma (Plasma-BNNT) consists of mainly double walled nanotube, which is the least wall number of BNNT achievable in a scalable synthesis methodology.
In this study, the thermal conductivity of Plasma-BNNT was evaluated as its epoxy paste in the range of BNNT loading from 1 to 10 weight percentages, in order to comprehend the capability of BNNT for polymer composite applications. It was compared with laser-synthesized BNNT and other thermal conductive fillers. The results revealed that BNNTs showed the highest thermal conductivity in our study. Transmission electron microscope images indicated that the BNNT morphology and boron nitride nano-byproduct in BNNT synthesis would be key factors to obtain higher thermal conductivity.