Preparation Of High Temperature Resistant Adhesives And Their Bonding Properties For SiC Composites

In recent years,the development of high temperature resistant adhesives has made the adhesion technology applied in the field of aerospace.SiC ceramic matrix composites can be used for heat resistant structural components in the aerospace field.However,it is very difficult to directly prepare large and complex structural components due to their high processing cost and long preparation cycle due to their brittleness characteristics,which limits their application and development to a great extent.Therefore,the preferred preparation technique for large size complex SiC ceramic matrix composite structural components is to manufacture separate components and then further assemble and connect them.Adhesive bonding is a very cost-effective and reliable method of bonding.However,it is difficult for existing adhesives to meet the connection requirements of SiC ceramic matrix composites.Therefore,this topic developed two kinds of efficient adhesives are phosphate hybrid phenolic resin high resistant adhesive and modified silicate high temperature resistant adhesive for bonding SiC ceramic matrix composites.In this paper,using phosphate resin as matrix,Al₂O₃ as curing agent,ZrO₂,Ti and Y₂O₃powder as heat resistant filler,by introducing phenolic resin,a kind of phosphate hybrid phenolic resin high temperature resistant adhesive PA-PF was prepared.The surface of SiC ceramic matrix composites was sealed with phenolic resin before bonding,and the bonding process was optimized.The tensile shear strength can reach 16.8 MPa at room temperature,and it can still reach 6.1 MPa at room temperature after calcination at 1800℃.The structure of the adhesive was characterized by SEM,FT IR,XRD and TG-MS-IR,indicating that the addition of phenolic resin filled the gap of phosphate network skeleton,and the adhesive structure became dense after high temperature treatment,which significantly improved the continuity of the adhesive system.Using Ni₂SiO₄,Ti,ZrO₂ and Sipowder modified sodium silicate resin as matrix,Al and Zn O powder mixed as curing agent,a modified silicate high-temperature adhesive SA-AN was developed.After calcination at 600℃,the tensile shear strength of SA-an was 18.7 MPa.Compared with the traditional silicate adhesive,That’s a 65.5%increase.When calcined at900℃,it is 17.9 MPa,which is 94.6%higher than that of traditional silicate adhesive SA-A.Even after calcination at 1200℃,a mixed fracture pattern of substrate damage of SiC ceramic matrix composites appears,indicating effective adhesion at this temperature.The structure of the adhesive and the interfacial reaction between the adhesive and SiC substrate were characterized by SEM,FT IR,XRD,TG-DSC and TEM.The results show that the adhesive SA-AN can be transformed into Al-Ni-rich intermetallic compound reinforced ceramic composite at high temperature.The thermal stress between the adhesive and the SiC ceramic matrix composite was effectively alleviated by the diffusion reaction layer.Due to the formation of intermetallic compounds and interfacial reactions,the mechanical properties and heat resistance of the joint are greatly improved.