A facile green chemistry route to porous silica foams

Porous inorganic silica foams are synthesized from waste ordinary glasses using a facile green chemistry route that involves a low-temperature hydrothermal ion-exchange reaction. The first step entails hydrothermal incorporation of water molecules and hydrogen ions within glass powders. Subsequent calcination of the product results in inorganic foams of uniform pore structure, with water vapor being the only by-product. The structure and properties of the inorganic foams, such as pore structure, pore size, density, porosity, strength, and thermal conductivity can be tuned by varying synthetic conditions such as reaction time and temperature. The synthesized inorganic foams are thermally stable up to 800 C with widely tunable porous structures on different length scales. The inorganic foams exhibit useful properties in terms of mechanical strength, thermal insulation and sound absorption, and appear promising for use as catalyst supports, impact absorbers, biomedical implants, and structural materials.