Integration of Pore Confinement and Hydrogen-Bond Influence on the Crystallization Behavior of C18 PCMs in Mesoporous Silica for Form-Stable Phase Change Materials

We report herein the integration of pore confinement and hydrogen-bond influence on the crystallization behavior of C18 PCMs PCM in mesoporous silica. Mesoporous silica nanoparticles with 2.74 nm pores are employed as supporting material. To evaluate the effect of the internal/external surfaces of silica on the crystallization behavior of C18 PCM, three kinds of PCMs with various functional terminals including stearic acid (SA), octodecane (OCC), and octadecanol (OCO) were employed, and the effects of various mass fractions of PCMs were comprehensively investigated as well. It is remarkable that the complete filling of the available nanosized pore volume and newly formed hydrogen bonds (H-O center dot center dot center dot O) are bound to result in the formation of the mesomorphic or amorphous phase of PCM; thus, no enthalpy can be evidenced by the DSC data. In addition, it turns out that the composite PCMs obtain at least a 2-fold increase over neat PCM in the thermal conductivity, due to the introduction of silica supporting material. The resulting three stabilized composites all exhibit favorable chemical compatibility, high thermal stability, improved thermal conductivity, and excellent thermal reliability, which are prerequisites for the storage and release of latent heat in PCMs.