PREPARATION OF POROUS Si₃N₄ NANOCOMPOSITES BY GELCASTING

The porous Si₃N₄ ceramics with a high strength, uniform structure and a relative high porosity were obtained by adding a little amount of nano carbon in slurry by gelcasting and two step sintering. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Energy dispersive X-ray spectroscopy (EDS), Archimedes and three-point bending methods were employed to characterize and analyze the microstructures and basic mechanical performances of porous Si₃N₄ ceramics.The results show that the strength of sintered porous Si₃N₄ ceramics reaches 100 MPa and its porosity is more than 60% under proper technical conditions. SEM shows that the pores are formed by pillar β-Si₃N₄, and XRD and EDS show that SiC were formed. The pillar β-Si₃N₄ structure, uniform porous distribution and formative SiC particles are the main reasons for good mechanical performances.