Mechanical and dielectric properties of silicon nitride ceramics with high and hierarchical porosity

Silicone resin (SR) processed Si3N4 porous ceramics with high and hierarchical porosity were prepared by adding naphthalene as a pore-forming agent via pressureless sintering technique. The porosity of the obtained Si3N4 porous ceramics is 40 similar to 71% with pores sizes ranging 0.1 similar to 1.0 mu m, 5 similar to 30 mu m and 50 similar to 200 mu m, which is determined by the pyrolysis of SR, partial sintering of Si3N4, and the volatilization of naphthalene, respectively. The bending strength is 6.8 similar to 80 MPa and the dielectric constant is 2.29 similar to 4.84. The results suggest that the hierarchical structure is responsible for a low dielectric constant with excellent mechanical property of the Si3N4 porous ceramics, making this material a good candidate for electromagnetic radome application. (C) 2012 Elsevier Ltd. All rights reserved.