In this work, discarded soda-lime glasses (from glass bottles) and recycled polystyrene (PS) spheres (d50 < 300 µm) were successfully converted into vitrocrystalline foams for thermal insulation applications. Physical and chemical properties of the selected and prepared raw materials (wastes) were characterized. Batches containing well mixed glass powder (d50 < 5 µm), PS spheres (10 - 80 vol.%) and PVA (8 vol.% ) were obtained and uniaxially pressed at 20 MPa. The obtained powder compacts were dried in air for 24 h and then fired at different temperatures (850 to 900 °C, 10 °C/min) for 30 min. Vitrocrystalline foams with interconned cells sizes between 86 and 815 µm, homogeneously distributed in a crack free matrix, were characterized from the point of view of their typical physical, chemical, morphological and mechanical properties. The results showed that it is possible to obtain vitrocrystalline foams with porosities up to 89% and compressive strength varying from 4 to 25 MPa.

In this work, ceramic shell (mullite source), an industrial solid waste from the lost-wax casting process, after crushing and milling steps, was used and evaluated as an alternative raw material source for the production of cellular ceramics for high temperature applications (> 1400 °C). The obtained ceramic shell powder, with particle size distribution (d50 < 2 µm) suitable for the production of ceramic foams, was characterized from the point of view of their physical, chemical, morphological and crystallographic properties. Samples were prepared and obtained by direct foaming and gelcasting routes, dried at room temperature and then fired in two steps (650 °C/2 h and 1550 °C/2 h), and cooled in the furnace to room temperature. The effects of solids loading (35 and 42 vol. %) and stirring velocity (500 and 2000 rpm) on the cellular structure (pore size distribution and porosity) and mechanical properties of the produced ceramic shell foam samples were evaluated. The results showed that it is possible to obtain ceramic foams based on mullite-zirconite, with pore sizes between 100 and 900 µm, porosities up to 77% and compressive strength varying from 3 to 20 MPa.