  Geopolymer has been considered as a green and low-carbon material with great
potential application due to its simple synthesis process, environmental
protection, excellent mechanical properties, good chemical resistance and
durability. In this work, the molecular dynamics simulation is employed to
investigate the effect of the size, content and distribution of carbon
nanotubes on the thermal conductivity of geopolymer nanocomposites, and the
microscopic mechanism is analyzed by the phonon density of states, phonon
participation ratio and spectral thermal conductivity, etc. The results show
that there is a significant size effect in geopolymer nanocomposites system due
to the carbon nanotubes. In addition, when the content of carbon nanotubes is
16.5%, the thermal conductivity in carbon nanotubes vertical axial direction
(4.85 W/(mk)) increases 125.6% compared with the system without carbon
nanotubes (2.15 W/(mk)). However, the thermal conductivity in carbon nanotubes
vertical axial direction (1.25 W/(mk)) decreases 41.9%, which is mainly due to
the interfacial thermal resistance and phonon scattering at the interfaces. The
above results provide theoretical guidance for the tunable thermal conductivity
in carbon nanotube-geopolymer nanocomposites.
