Fabrication and microstructure characterization of continuously porous Si2N2O–Si3N4 ceramics

The microstructure of continuously porous Si2N2O–Si3N4 ceramics fabricated for use in environmental filters by a multi-pass extrusion process was investigated using SEM, XRD and TEM techniques. The matrix regions of the nitrided Si2N2O–Si3N4 porous bodies were composed of many Si3N4 particles and short Si2N2O fibers. However, in the continuously porous regions, many network type Si2N2O fibers, 200–420 nm in diameter, with a high aspect ratio were observed. After post-sintering of the nitrided bodies at 1800 °C, the diameter of the fibers increased to about 2–3 μm, while their length was shortened. The values of bending strength, relative density and hardness of the post-sintered Si2N2O–Si3N4 bodies were about 117.6 MPa, 73.6% and 616 Hv, respectively.