Preparation and properties of Si_3N_4/BN ceramic composites

摘要

Using Si and BN powders as raw materials, silicon nitride/hexagonal boron nitride (Si_3N_4/BN) ceramic composites were fabricated at a relatively low temperature by using the reaction bonding technology. The density and the nitridation rate, as well as the dimensional changes of the specimens before and after nitridation were discussed based on weight and dimension measurements. Phase analysis by X-ray diffraction (XRD) indicated that BN could promote the nitridation process of silicon powder. Morphologies of the fracture surfaces revealed the fracture mode for Si_3N_4/BN ceramic composites to be intergranular. The flexural strength and Young's modulus decreased with the increasing BN content. The ceramic composites showed good machinability with BN addition.