Si_3N_4SiC(N) nanocomposites infklunece of SiC(N) nanoprecipitates on the microstructure

摘要

The influence of nanometric second phases (SiCN-or SiC) introduced into a Si_3N_4 matrix on both the sintering stage and the microstructural development is studied by comparing Si_3N_4/SiC(N) nanocomposites to Si_3N_4 monoliths, all of them being hot pressed with sintering aids (Y_2O_3, Al_2O_3). Whatever the nature of the second phase, the presence of nanosized SiC particles limits the Densification and increases the α to β phase transformation. For a constant SiC content (20 wt 1/00), During the first steps of hot pressing, the inhibition of densification is more important in the case of SiC nanoparticle addition, compared to SiC issued from SiCN nanopowder.