PURPOSE: To improve the porosity by mixing and stirring a specific silicate slurry with an aluminate slurry, foaming and gelatinizing the mixture, providing a porous hydrogel, removing the soda content according to the leaching, then drying the resultant hydrogel and burning the dried hydrogel.
CONSTITUTION: Na2SiO3 is mixed with ferritic powder having 1-50μm particle diameter, a surfactant, Al powder and water to prepare a silicate slurry. On the other hand, NaAlO2 is mixed with ferritic powder, a surfactant and water to prepare an aluminate slurry. The silicate slurry is then mixed with the aluminate slurry at a ratio within the range of (1/0.6) to (1/1.6) to provide a slurry having a composition of 5-20wt.% Na2SiO3, 5-20wt.% NaAlO2, 65-75wt.% ferritic powder, 0.05-0.15wt.% surfactant, 0.04-0.3% Al powder and 5-25wt.% water. The obtained slurry is then cast, foamed and gelatinized to afford a porous hydrogel, which is then washed, dried and subsequently burned at a high temperature to provide the objective porous ferritic wave absorber having 40-80wt.% porosity, ≥80wt.% closed cell content and 100-800μm pore diameter.
TODA YUKIO
ITO TOYOHITO
SUGAWA AKIHIKO
HAYASHI TOSHIKATSU
