INFLUENCE OF HEAT TREATMENT ON THE CONDUCTIVITY OF GRAPHITE JOINT BONDED BY HIGH TEMPERATURE ADHESIVE

High temperature adhesives were prepared with phenol formaldehyde resin as matrix and B 4C powders as additives. The graphite samples bonded by the above adhesives were heat treated at different temperatures ranged from 200?℃ to 1?500?℃. Subsequently their conduct electricity was tested. The structure of the joint was also characterized by means of XRD and SEM. The results showed that the heat treatment temperature had critical influence on the joints' conduct electivity. The specific resistance reach its maximum value when the graphite joints were treated at 200?℃ because of the non conduct character of phenol formaldehyde resin. But the specific resistance of the joint decreased rapidly with increasing of heat treatment temperature below 1?000?℃. With the treatment temperatures rising higher than 1?000?℃, the graphite joints showed satisfing conductivity performance with specific resistance decreased slowly. Additionally, the boron carbide also had important influenced on the electrical conductivity of the joint due to its semi conductor and graphitzation effect.