High-temperature performance of boron carbide modified phenol-formaldehyde resin bond to silicon carbide ceramic

A high temperature adhesive was prepared using phenol -formaldehyde resin ( PF) as the matrix and boron carbide (B₄C) particles as the modifier，with which silicon carbide ( SiC) ceramics were bonded. The mechanical property of the adhesive was tested at room temperature af ter being heat-treated in the temperature range from 300℃ to 800℃respectively. The result s indicate that an out standing shearing st rength over 20 MPa could be achieved for SiC ceramics after treatment at 700～800℃. The micro-morphologies at bonding interfaces were investigated by SEM and EDAX，and the main volatiles originating f rom pyrolysis were investigated by pyrolysis gas chromatography-mass spectroscopy. A compact and stable st ructure can be achieved through the modifying reaction between B₄C and volatiles such as CO. The reaction product B₂O₃ being melt at high temperature possesses satisfactory wet tability and adhesive capacity，which can close and mend the shrinkage lacunas. B₂O₃ also combines with active groups in the resin matrix，which can be responsible for the improvement of the bonding cement stability and adhesive st rength at high temperature.