Microstructural properties and heat transfer characteristics of in-situ modified silica aerogels prepared with different organosilanes

Conducting an in-situ modification during the sol-gel reactions, without any post gelation-modification, offers a cost-effective and time-saving strategy in the production of silica aerogels. Therefore, in this study, in-situ modified silica aerogels were synthesized as potential thermal insulation materials via a two-step sol-gel process under ambient pressure. Different organosilanes having methyl (SA-MTMS), ethyl (SA-MTES), vinyl (SA-VTMS), epoxide (SA-GLYMO), and methacrylate functional (SA-MEMO) groups were used as silica sources. According to the selected precursor, the change in the heat transfer properties were investigated both by thermal conductivity measurements and by theoretical models. SA-MTMS possessed the lowest density (92 kg / m 3 ) and high thermal stability (up to 700 degrees C). Despite the existence of bulk organic groups in its structure, the SA-GLYMO had the highest specific surface area (531 m 2 / g) . Regardless of their morphology, all samples have exhibited similar insulation performances ( lambda= 42-47 mW/mK). However, the prominent heat transfer mechanisms were directly affected by the bulk density and the underlying microstructure. For low-density samples, gas-contributed thermal conductivities were the key contributor to the total thermal conductivity whereas solid thermal conduction was the dominant mechanism in high-density samples. The coupling thermal conductivity term was also crucial as the total conductivity would have been significantly underestimated without it. (c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

In-situ modified silica aerogels were synthesized as potential thermal insulation materials via a two-step sol-gel process under ambient pressure. Different organosilanes were used as silica sources, and the heat transfer properties were investigated through thermal conductivity measurements and theoretical models. The study revealed that the density and microstructure of the samples directly affected the heat transfer mechanisms.