Characterization and properties of rapid fabrication of network porous Si3N4 ceramics

A porous silicon nitride ceramic, composed of network intercrossed elongated β-Si3N4 rods, was rapidly synthesized in one step, i.e. direct solid deposition based on the combustion of falling Si powder in nitrogen flow. Compared with the methods reported in the literature, this method is characterized by the advantages such as fast and easy process, large output, low energy consumption and cost, environmental friendly and high purity. The as-received product consists of β-Si3N4 (73.22 wt%) and α-Si3N4 (26.78 wt%). The bulk density is 1.88 g/cm3 with porosity up to 46.27%. In view of its properties, the bending strength is 146.84 MPa, the fracture toughness is 2.37 MPa m1/2 and the modulus of rupture at 1400 °C is 49.40 MPa. These combining its network structure can be a promising candidate used as ceramic membrane to purify the non-ferrous molten metals at high temperature.