Alumina joints brazed by screen-printed B4C–SiO2 in air

In this study, B 4 C–SiO 2 was employed as the joining material via a screen-printing method to join alumina (Al 2 O 3 ) ceramics at 1000 °C in ambient air. Effects of mass ratios of B 4 C and SiO 2 ranging from 1:0.5 to 1:2.5 on the composition, microstructure, and mechanical properties of the joints were investigated. When the content of SiO 2 was equal or greater than that of B 4 C, the interlayer of the brazed joints was defect-free and consisted of Al 4 B 2 O 9 whiskers and calcium borosilicate glass based on microscopically electronic analyses. With the content of SiO 2 increased, the shear strength of the joints increased first and then decreased. The average shear strength of the joint reached the maximum value of 110 ± 19 MPa when the mass ratio of B 4 C to SiO 2 was 1:2. The current study demonstrated that the screen-printed B 4 C–SiO 2 system could be a very beneficial approach to obtain high strength Al 2 O 3 joints with defect-free interlayer at relatively low joining temperatures in air.