Investigation of transmittance and thermal conductivity properties of silica gels for application as transparent heat insulation materials

In several applications, silica gels are widely applied as solid phases in chromatography, paint thickeners, filters or molecular sieves. New studies investigate the possible application of silica gels as transparent heat insulation materials (TIMs) at low and elevated temperatures. This study investigates the thermal insulation properties and favorable conditions for silica gels for using as TIMs. To this end, silica sol was gelled and the resulting silica gel was aged before it was either hydrothermally treated or fired. The thermal conductivity was measured with the hot disk method at room temperature. The lowest thermal conductivity was achieved by a hydrothermal treatment performed at 150 °C and 5-h dwell time. The best results for the simultaneous optimization of the transmittance and thermal conductivity were as well reached by a hydrothermal treatment at 150 °C with 5-h dwell time. Firing of silica gels did not improve the thermal insulation properties.