Processing of silica foam using steam heating and its characterization

Silica foams with 50–86 vol.% porosity have been developed through steam-heating route using slurries containing ovalbumin as binder, as well as sucrose and colloidal silica as additives. On steam-heating, only 1 h is required for drying of as-cast foams, as the cell-walls being restrained from shrinking by intra-cellular gas pressure, and simultaneously strengthened by ovalbumin protein coagulation, show minimum damage. Scanning electron microscopic studies of sintered foams have shown near-spherical pores with size distribution having mean of ≈250–300 μm. These pores appear interconnected through finer pores of ≈15–25 μm size along their walls. Solid loading, binder and sucrose concentrations of slurries for optimum viscosity have been obtained through rheological studies to tailor desirable pore content and size distributions in the sintered foams. Youngʹs moduli and compressive strengths are found to be in the ranges of 14.4–544 MPa and 0.3–8.6 MPa, respectively for sintered foams having ≈55–90 vol.% porosity content.