THE STRUCTURE CHANGEMENT AND MODIFYING MECHANISM OF B_4C ADDITIVES IN PHENOL-FORMALDEHYDE RESIN FOR BONDING GRAPHITE AT HIGH TEMPERRATURE

High temperature adhesives (HTAs) for bonding graphite were prepared using phenol formaldehyde resin(PF) as matrix and boron carbide (B 4C) was additive to modify the performance of the adhesive. Graphite materials were bonded by the above adhesive. The bonded graphite samples were heat treated at 200 ℃, 800 ℃ and 1 500 ℃, respectivety. Test results showed that the bonded graphite samples had satisfactory strength. Scanning electron micrograph (SEM) and X ray diffraction (XRD) were used to analyze the structural change and the compositions of the adhesive treated at different temperatures. The modification mechanism of B 4C additives to phenol formaldehyde resin was also discussed.