Gaseous thermal conductivity studies on mesoporous silica particles based on a bimodal-pore distribution model

Abstract

The bimodal-pore distributed features of mesoporous silica particles have great effects on their thermal conductivity variations. In this paper, a simplified bimodal-pore distribution model is proposed to depict the variation in thermal conductivity of mesoporous silica particles (such as MCM-41 and SBA-15) at nitrogen pressure. The model is analytically described by a parallel connection of the gas heat conduction in pores and the two different apertures, and the scaling factor F is added to consider the gas-solid coupling effect. To verify the correctness of the proposed model, the microstructure parameters of mesoporous silica particle samples are measured by the Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and the nitrogen adsorption method, and the thermal conductivity is further measured via the transient hot-strip method in a nitrogen atmosphere of 0–15 MPa. The results show that the theoretical model yields a good agreement with the experimental data, and hence can be used to study the effect of bimodal-pore distributed features on the thermal conductivity of mesoporous materials.