Silica aerogel/polyvinyl alcohol (PVA) insulation composites with preserved aerogel pores using interfaces between the superhydrophobic aerogel and hydrophilic PVA solution

A fabrication method was designed for thermal insulation composites by applying the thermal characteristics of silica aerogels with preservation of pores in the aerogel to achieve extremely low thermal conductivity of the composites. A new process was proposed to generate interfaces between superhydrophobic silica aerogels and a hydrophilic polyvinyl alcohol (PVA) solution and to fabricate the silica aerogel/PVA composite forcibly while PVA is precipitated over the interfaces by making the solvent vaporize at a slow rate during stirring. Well-preserved aerogel pores were observed in the PVA-coated composites using an electron microscope and a low thermal conductivity of 0.022 W/m K was achieved, which is only 11% of the thermal conductivity of PVA. The measured thermal conductivity of the aerogel/PVA composite was lower than that predicted by the Mori-Tanaka method (MTM) with the perfect interface assumption due to the effect of phonon scattering at the incomplete interfaces.