  The thermal transport properties of porous silicon and nano-hybrid "porous
silicon/water" systems are presented here. The thermal conductivity was
evaluated with equilibrium molecular dynamics technique for porous systems made
of spherical voids or water-filled cavities. We revealed large thermal
conductivity enhancement in the nano-hybrid systems as compared to their dry
porous counterparts, which cannot be captured by effective media theory. This
rise of thermal conductivity is related to the increases of the specific
surface of the liquid/solid interface. We demonstrated that significant
difference for more than two folds of thermal conductivity of pristine porous
silicon and "porous silicon liquid/composite" is due to the liquid density
fluctuation close to "solid/liquid interface" (layering effect). This effect is
getting more important for the high specific surface of the interfacial area.
Specifically, the enhancement of the effective thermal conductivity is 50 % for
specific surface area of 0.3 (1/nm), and it increases further upon the increase
of the surface to volume ratio. Our study provides valuable insights into the
thermal properties of hybrid liquid/solid nanocomposites and about the
importance of confined liquids within nanoporous materials.
