Joining silicon nitride ceramics with ZrSi2-SiC composite filler by spark plasma sintering

A novel ZrSi2 + 10 wt% SiC composite filler was employed to join silicon nitride (Si3N4) ceramics by spark plasma sintering (SPS) method at temperatures ranging from 1200 degrees C to 1400 degrees C in Ar atmosphere. Results of XRD analyses showed that the interlayer was composed of SiC, ZrSi2, t-ZrO2, m-ZrO2, and SiO2 phase. Results of electronic microscopy examinations showed that a layer of ZrO2 with a thickness of about 3 mu m was formed at the interface between the interlayer and the substrate when the joint was joined at 1400 degrees C. The optimal shear strength of 114.2 +/- 3.6 MPa was obtained at a relatively low temperature of 1400 degrees C for 10 min. The use of ZrSi2, which exhibits excellent mechanical properties and oxidation resistance, could potentially provide the mechanically robust joints of Si3N4 ceramics to be applied in oxidative environments at elevated temperatures.