Ceramizable phenolic adhesive modified by different inorganic particles: A comparative study of thermal stability, bonding strength and bonding mechanism

In this work, two ceramizable phenolic adhesives were prepared using ZrSi2 particles or ZrSi2/B4C mix particles as the inorganic fillers. The thermal stability, bonding strength, microstructure and phase composition of the adhesives were investigated by TGA, shear strength of Al2O3 joints, SEM, EDS, XRD and XPS. The results show that these two adhesives have different bonding performances and ceramicization evolutions above 600 °C in air due to the addition of the second phase particles B4C. The bonding strength of ZrSi2/B4C modified phenolic adhesive after treatment at 1200 ℃ can be as high as 36.6 MPa, while the bonding strength of ZrSi2 modified phenolic adhesive under the same conditions is only 17.5 MPa. B4C undergoes oxidation reaction before ZrSi2, and the oxidation product B2O3 liquid phase not only reacts with ZrSi2 to form oxidation-resistant ZrB2, but also can dissolve the high temperatures defects of the adhesive and chemically bond with the Al2O3 substrates at the interface.