High-strength and wave-transmitting Si3N4–Si2N2O-BN composites prepared using selective laser sintering

Abstract

In this study, high-strength and wave-transmission silicon nitride (Si3N4) composites were successfully developed via selective laser sintering (SLS) with cold isostatic pressing (CIP) after debinding and before final sintering, and the optimal moulding process parameters for the SLS Si3N4 ceramics were determined. The effects of the sintering aids and secondary CIP on the bulk density, porosity, flexural strength, fracture toughness, and wave-transmitting properties of the Si3N4 composites were studied. The results showed that the increased CIP pressure was beneficial to the densification of SLS Si3N4 ceramics and improved their mechanical properties. However, the wave-transmitting performance decreased as the CIP pressure increased. The Si3N4 ceramics prepared by the moulding of sample S11 were more in line with the performance requirements of the radomes. To obtain good comprehensive performance, an additional 3% of interparticle Y2O3 was added to the pre-printed mixed powder of granulated Si3N4 particles and resin and the secondary CIP pressure was adjusted to 280 MPa. After sintering, the bending strength, fracture toughness, and dielectric constant of the Si3N4 ceramics were 651 MPa, 6.0 MPa m1/2, and 3.48 respectively. This study provides an important method for preparing of Si3N4 composite radomes using SLS process.