BN/Si3N4 nanocomposite with high strength and good machinability

BN/Si3N4 nanocomposite was prepared using BN/Si3N4 powder obtained by nitriding Si3N4/NH4HB4O7 mixture in ammonia gas as the starting powder. Microstructural investigations by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that BN particles were homogeneously distributed within the matrix grains as well as at the matrix grain boundaries, and the growth of Si3N4 matrix grain was significantly retarded by BN particles. The BN/Si3N4 nanocomposite showed a higher strength than the conventional BN/Si3N4 microcomposite due to the formation of fine and homogeneous microstructure in it. BN/Si3N4 nanocomposite with a BN content of 20 vol% and above showed excellent machinability, because of the formation of weak BN/Si3N4 interfaces and the cleavage behavior of BN particles.