Alkali activated ceramic foams have been produced by using metakaolin and/or diatomite as aluminosilicate source, an aqueous sodium silicate solution as alkali activator and Na2SiF6 as a catalyst that promotes the gelification of the entire system. Two different techniques of direct foaming have been coupled, one based on chemical reactions with gas production and the other one based on a mechanical foaming. Then, other levels of hierarchical porosity (nanometric and macrometric scale) have been added to the produced expanded ceramic systems. This approach allows to tailor the chemical–physical properties and density of the resulted hybrid foams. The produced foams have been mechanically, chemically, physically and morphologically characterized. Moreover, their acoustic and thermal properties, in terms of thermal stability and conductivity, and also their fire behavior have been investigated
