Thermal conductivity of monolithic assemblies of SBA-15 ordered mesoporous silica particles

• Monoliths have been prepared from self-assembly of SBA-15 (not)aggregated particles.
• After a heat treatment at 300 °C monoliths exhibit the highest SBET and pore volume.
• Thermal conductivity of SBA-15 monoliths ranges from 32 to 46 mW m−1 K−1.
• Mechanism of heat transfer differs when organic template fills internal porosity.
• Thermal conductivity depends on the inter aggregate macroporosity.

The thermal conductivity of ordered mesoporous silicas SBA-15 type made up of primary micron size rod-shaped particles, with different states of aggregation and processed as monoliths without any binder has been studied. In particular, the influence of the post-synthesis thermal treatment of materials on the structural and textural characteristics and on the effective thermal conductivity was investigated. Thermal conductivity results were compared with observations by electronic microscopy and to the physicochemical data (X-ray diffraction, nitrogen adsorption/desorption volumetric measurements, 29Si and 13C solid-state NMR). It was observed that the elimination of the surfactant on the one hand, and the dehydroxylation of the silica network on the other hand, are partly responsible for variations in thermal conductivity. Thermal conductivity values in the range of 32–46 mW m−1 K−1 was also found dependent on the morphology of particle aggregates that strongly impacts the macroporosity. Good thermal stability of the silica mesostructures was also observed up to 900 °C with low thermal conductivity of about 46 mW m−1 K−1. These properties make these materials very promising for thermal insulation applications over a large temperature range (room temperature up to 900 °C).

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