Pore-size effects on thermal conductivity of SiO₂ quartz using non-equilibrium molecular dynamics simulations

Porous materials are commonly used to decrease or regulate thermal transport in insulating materials due to the very low thermal conductivity of the pores. More pores can achieve a better insulating effect; however, this can also be a shortcoming when the materials are directly involved in physical movement with friction, such as an interior wall of a cylinder in an automobile engine intended to prevent heat loss. Thus, it is important to clarify the mechanisms of the pore-dependent thermal properties of porous materials. In this study, the effects of the number and size of pores in silica quartz on thermal conductivity were investigated using nonequilibrium molecular dynamics simulations. The results revealed that the thermal conductivity of porous silica quartz decreased in all cases with an increase in the volume fraction of pores. A lower number of pores in the system showed higher thermal conductivity in the range of low volume fractions. We also showed that the interstitial distance between pores mostly governs thermal conduction at low volume fractions [Formula: see text] vol.%. Additionally, the mechanism of thermal conduction was assessed with respect to several theoretical models.