以酚醛树脂为基体,加入B4c作为改性填料制备出高温粘结剂,并对si3N4陶瓷进行粘接。在300~800℃温度范围内对Si3N4陶瓷粘接试样进行热处理,并测试了不同温度热处理后的室温剪切强度。结果表明,经过700~800℃热处理后,粘结剂表现出较为理想的粘接性能,剪切强度测试结果为Si3N4陶瓷基体破坏。利用扫描电镜研究了粘接试样的断面形貌及胶层结构特征。研究表明,在高温热处理过程中,B4C改性填料发生了复杂的物理、化学变化,通过B4C与树脂挥发分之间的改性反应,有效提高了酚醛树脂热解后的残炭值,进而改善了粘接胶层结构的高温稳定性;纤维状物质的形成与B2O3颗粒的细化,有助于提高粘接胶层的连接强度。
High-temperature adhesive was prepared using phenol-formaldehyde resin (PF) as matrix and boron carbide (B4C) as modifier, silicon nitride (Si3N4) ceramics were bonded by the adhesive, and the bonded specimens were heat-treated within 300--800℃ subsequently. The adhesive properties of the high-temperature adhesive were tested. The results indicate that the adhesive has outstanding high-temperature bonding properties for Si3N4 at high temperature. The failure of bonded joints treated at 700 and 800 ℃ were due to the broken of Si3N4 matrix. The micro-morphologies at bonding interfaces were also investigated by SEM. It is shown that complex physical and chemical changes occurred during the heat-treatment process. By means of the modification reaction between B4C and the volatiles of PF resin, the value of carbon residue was prompted effectively; and the formation of fibers and the nanocrystallization of B2O3 benefit the achievement of satisfactory high-temperature bonding properties.