Microstructure and Wettability of Glass Solder on Al2O3 Ceramic and Its Joints Properties

Abstract

The borate glass 35B2O3–25SiO2–25Na2O-10ZnO3–5BaO (in wt.%) formed the basis for the glass system employed in this study. In air at various pressures and temperatures, 96 wt.% pure alumina ceramics (96 Al2O3) were brazed together using glass solder. At the same time, the wettability of the glass on the Al2O3 ceramics is researched at different temperatures and pressures. The results demonstrated that the contact angle of glass on Al2O3 ceramics was decreased with the temperature increasing, and attached 18 degrees as temperature was 580 °C with holding 120 mins. It was also concluded that the bubbles in the glass solder were changed from round to oval and the quantity was decreased with the pressure increasing. Furthermore, the thickness of the glass solder was decreased with the pressure and temperature. When the pressure was changed from 5 kPa to 20 kPa at 560 °C welding temperature, thickness of glass solder is decreased from 22.3 μm to 8.5 μm. Upon increasing the temperature at 10 Kpa, the thickness of glass solder was from 23.74 μm to 6.2 μm. The EDS analysis for Al2O3/glass/Al2O3 joints boned at 560 °C under 20 kPa and 580 °C under 10 kPa, respectively. The elements Si and O were observed in joint domain that penetrated into alumina ceramic layer forming the interface layer with ceramic substrate thoroughly.