Polysilazane-based high-temperature adhesives for the joints of amorphous SiBON ceramic composites

Amorphous SiBON ceramic integrated the advantages of SiO2 and BN can be used as heat-resistant wave transparent composites in radome, and corrosive-resistant high strength materials in aeronautics and astro-nautics, while it is a great challenge to bind the amorphous SiBON ceramic to solve the problem on difficulty of fabrication of large-sized. In this work, we prepared four kinds of polysilazane-based high-temperature adhesives to join amorphous SiBON ceramic. The joining strength was tested and compared after heat treatment at tem-peratures ranging from 200 degrees C to 1100 degrees C at different atmospheres. Satisfactory shearing strength and toughness (the strength of joints could reach above 25 MPa in air until breakage of ceramic substrate and maximum strength of joints was above 7.5 MPa in Ar) were achieved at the binding interface without pressure applied during joining. The mechanism for the interfacial binding was proposed by analyzing microstructure and chemical compositions. A normal B2O3-SiO2-ZrO2 glass-ceramic interlayer was formed in the joint seam in air, and amorphous SiCN and C3N4 ceramics were generated in the sample in Ar, which reinforced the binding strength of the lap amorphous SiBON ceramic. It is significant to find modified heat-resistant organic adhesives for binding amorphous ceramics to produce high strength ceramic joints in both air and inert atmospheres to resolve the problems on poor processing performance difficulty of fabrication of large-sized of ceramics.