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

Abstract

In this study, B4C–SiO2 was employed as the joining material via a screen-printing method to join alumina (Al2O3) ceramics at 1000 °C in ambient air. Effects of mass ratios of B4C and SiO2 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 SiO2 was equal or greater than that of B4C, the interlayer of the brazed joints was defect-free and consisted of Al4B2O9 whiskers and calcium borosilicate glass based on microscopically electronic analyses. With the content of SiO2 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 B4C to SiO2 was 1:2. The current study demonstrated that the screen-printed B4C–SiO2 system could be a very beneficial approach to obtain high strength Al2O3 joints with defect-free interlayer at relatively low joining temperatures in air.