Solid-Gas Reaction during Sintering of Si3N4 Ceramics (Part 6)

Effect of Si3N4/SiO2/BN packing powder and Si3N4/SiO2 powder compacts, which produce SiO gas atmosphere upon heating were investigated for suppressing mass loss in Si3N4 ceramics during sintering in 0.1MPa N2 atmosphere. As a result, packing powder with larger SiO2 particles effectively suppressed the generation of SiO gas according to mass loss reaction from the samples. Upon sintering with Si3N4/SiO2/BN packing powder and Si3N4/SiO2 powder compacts, a surface porous layer with several hundreds micrometer thick which generated under the condition of Si3N4/BN mixed powder bed or without powder bed at long soaking time in 0.1MPa N2, was not observed at all. The cross-sectional morphologies under this experimental condition were comparable to those under 1MPa N2.