2021 Volume 35 Issue 3 Pages 83-89
Silica aerogels are low density silica gel with nanoporous structure and are famous as materials with the lowest thermal conductivity (below 0.02 W/(m∙K)) except for vacuum insulation panels. Silica aerogel-composite insulation materials with polymer sheets or nonwoven fabrics have been developed and commercially available. The standard method of thermal conductivity measurement has not yet been established for these materials, due to limited applicable methods for this low conductivity region and requirement of large sample size. We developed a silica aerogel composite sheet and compared its thermal conductivity measured by different methods. Heat flow meter (HFM) method showed almost the same value (0.016 W/((m∙K)) with guarded hot plate (GHP) method. Sandwiching thin sample (1.8 mm) with silicone sponge provided a thermal conductivity close to that obtained by stacking the samples. Effect of sample size on HFM method and comparison with hot wire method were also investigated.
