Silicon Nitride/Boron Nitride Composite by Combustion Synthesis

摘要

Machinable silicon nitride/ hexahedral boron nitride (Si_3N_4/h-BN) composites were in-situ synthesized in a nitrogen (N_2) atmosphere by means of combustion synthesis gas-solid reaction with silicon (Si) powder and ft-BN as raw materials. The effect of the volume fraction of h-SN on the machinable properties of Si_3N_4/BN composite was studied. The results show that Si powder was fully nitrified and no residual Si was found. Microstructures by a scanning electron microscopy (SEM) show Columnar crystals of β-Si_3N_4 are the main phase and acicular crystals of h-BN disperse β-Si_3N_4 intergranular. With the increasing of the volume content of h-BN, the machinability of the composite increases, but the bending strength of composite decreases firstly and then increases. The lowest bending strength is 84.96MPa at 25% volume fraction of h-BN.