Effect of pure β-Si3N4 powder on microstructure and mechanical properties of porous Si3N4 ceramics

Porous Si3N4 ceramics were produced by the initial Si3N4 powder added different amounts of β-Si3N4 powder. The density, porosity and flexural strength were tested by the methods of Archimedes method and three-point bending measurements, respectively. Phase composition and microstructure of Si3N4 ceramics were studied by X-ray diffraction and scanning electron microscopy. Fibrous β-Si3N4 grains developed in the porous microstructure. The grain morphology and size were affected by adding different amounts of β-Si3N4 powder. Fibrous β-Si3N4 grains dispersed in the porous Si3N4 ceramics uniformly with the length of 4∼10μm, the average diameter of 0.6μm and average aspect ratio of 7 were obtained. Adding 3 mass% β-Si3N4 powder, porous Si3N4 ceramics with excellent properties were prepared.