Porous Si3N4 fabrication via volume-controlled foaming and their sound absorption properties

Highly porous Si3N4 ceramics were fabricated via a volume-controlled mechanical foaming method. Slurries were fully filled in closed containers after foaming, thus porosity was controlled by adjusting the ratio of solid content and volume of foamed slurries. Pore size could also be controlled in this work by changing solid content of slurries. Porous Si3N4 ceramics with porosity varied from 70 to 90% were obtained after foaming and sintering. The as-obtained porosity of porous Si3N4 ceramics was in well consistence with evaluated porosity before experiments. These highly porous Si3N4 ceramics showed fine compressive strength ranging from 6.7 MPa to 59.9 MPa. Sound absorption characteristics of porous Si3N4 ceramics were investigated, both porosity and pore size had important effects on sound absorption coefficient.