Foaming of Recyclable Clays into Energy-EfficientLow-Cost Thermal Insulators

Thermal insulators are crucial to reduce the high energy demands and greenhouse emissions in the construction sector. However, the fabrication of insulating materials that are cost-effective, fire resistant, and environmental-friendly remains a major challenge. In this work, we present a room-temperature processing route to fabricate porous insulators using foams made from recyclable clays that can be locally resourced at very low costs. Foams containing either pure Kaolin or a Kaolin-based clay mixture are produced through mechanical frothing or an in-situ gas-generating reaction. Surface modification of the clay particles using a cationic amphiphilic molecule leads to particle-stabilized foams that are sufficiently strong to withstand the high capillary stresses developed during water evaporation. Self-supporting insulators with up to 90% porosity and thermal conductivities as low as 0.13 W/mK can thus be obtained by simple casting and drying at ambient temperature in an ultralow energy process. Such ma...