posted on 2015-08-26, 00:00authored byNavid Sakhavand, Rouzbeh Shahsavari
Although
boron nitride nanotubes (BNNT) and hexagonal-BN (hBN)
are superb one-dimensional (1D) and 2D thermal conductors respectively,
bringing this quality into 3D remains elusive. Here, we focus on pillared
boron nitride (PBN) as a class of 3D BN allotropes and demonstrate
how the junctions, pillar length and pillar distance control phonon
scattering in PBN and impart tailorable
thermal conductivity in 3D. Using reverse nonequilibrium molecular
dynamics simulations, our results indicate that although a clear phonon
scattering at the junctions accounts for the lower thermal conductivity
of PBN compared to its parent BNNT and hBN allotropes, it acts as
an effective design tool and provides 3D thermo-mutable features that
are absent in the parent structures. Propelled by the junction spacing,
while one geometrical parameter, e.g., pillar length, controls the
thermal transport along the out-of-plane direction of PBN, the other
parameter, e.g., pillar distance, dictates the gross cross-sectional
area, which is key for design of 3D thermal management systems. Furthermore,
the junctions have a more pronounced effect in creating a Kapitza
effect in the out-of-plane direction, due to the change in dimensionality
of the phonon transport. This work is the first report on thermo-mutable
properties of hybrid BN allotropes and can potentially impact thermal
management of other hybrid 3D BN architectures.