Direct bonding of AlN and graphite by spark plasma sintering

AlN powders were simultaneously sintered and bonded to isotropic graphite disks at temperatures of 1800 and 1900°C under 30 MPa by spark plasma sintering (SPS). The effects of temperature and Y2O3 additive content on the bonding strength were investigated. The bonding mechanism is proposed as follows: as the temperature increases, a molten Al–Y–O phase forms and flows into the open pores of graphite. As the material cools, a Al2Y4O9 phase forms, resulting in a physical bond between the graphite and AlN. The bonding strength of AlN/graphite increased with an increase of temperature and Y2O3 content. When 10 mass % Y2O3 was used as a sintering additive, the bonding strength of AlN/graphite reached 19 MPa at 1900°C.