Bonding of silicon nitride ceramic by ultrafast high temperature sintering

Silicon nitride, Si3N4 is one of the advanced ceramics that is widely used in engineering industries due to its attractive properties such as high temperature stability and hardness. Due to the difficulty in fabricating complex shaped and large size components, the application of Si3N4 has been restricted. Joining of Si3N4 parts is required to widen its application. In this study, ultrafast high sintering (UHS) will be used to carry out the joining process. UHS has been proven to sinter ceramics in a short amount of time, but little study has been done on using UHS to join ceramics. Comparing UHS and conventional sintering method, UHS is a much faster process. In conventional sintering, thermal degradation of the substrate may happen, which might contaminate the samples. This project provides a systematic study on bonding of Si3N4 by UHS and characterizes its joint strength. The adhesive consists of yttria, silica, alumina and Si3N4 and was prepared by UHS at different temperatures. Archimedes method was used to measure the density of the adhesive. Wettability testing was carried out to analyze the contact angle between the adhesive and Si3N4 substrate. Si3N4 was joined using the suitable set of parameters by UHS in argon atmosphere. Shear stress testing was used to evaluate the mechanical properties of the bonded Si3N4, and scanning electron microscope was used to analyze the fracture surface of the sample. According to Archimedes method, at 1500°C, the adhesive has the highest density. Wettability test shows that all the adhesive sintered at 1500 °C except B4 (0% Si3N4) have good wettability. Hence, the joining of Si3N4 with adhesive B1 to B3 was carried out at 1500°C. The shear testing shows that the adhesive with a molar percentage 30% of Si3N4 has the highest shear stress (97.7 MPa). Therefore, UHS has demonstrated its capability to form a bond with Si3N4 with promising results.Bachelor of Engineering (Materials Engineering