FDU-12 cubic mesoporous silica as matrix for phase change materials using bismuth or stearic acid

Mesoporous silica nanocomposites are a promising class of shape-stabilized phase change materials with high heat of fusion. We report the first study on the possibility of using FDU-12 mesoporous silica, which contains cubic ordered mesopores, as matrix for stearic acid and bismuth. Shape-stabilized nanocomposites which exhibit no macroscopic segregation of the liquid phase upon phase transition due to intercapillary forces, were obtained at 70% mass fatty acid or 50% mass metal loading. The matrix and PCMs were characterized by X-ray diffraction, infrared spectroscopy, thermogravimetric analyses and differential scanning calorimetry coupled with optical microscopy. The shape-stabilized PCM containing stearic acid exhibits a heat of fusion of 100 J g−1 and two distinct melting/freezing transitions, which correspond to interparticle and nanoconfined acid phases. The bismuth containing sample has a reversible transition enthalpy of 21.9 J g−1 and a melting point decreased by 1.6 °C with respect to bulk. The metal PCM is confined in the interparticle space, as confirmed by electron microscopy analyses. Both samples have good thermal reliability, retaining their heat of fusion values after 50 heating–cooling cycles. FDU-12 is a promising matrix for obtaining both organic and inorganic shape-stabilized phase change materials.