The preparation and performance analysis of zirconium-modified aluminum phosphate-based high-temperature (RT–1500 °C) resistant adhesive for joining alumina in extreme environment

High-temperature-resistant adhesive is a critical material in the aerospace field. The zirconium-modified aluminum phosphate-based adhesive developed in this work had the advantage of adjustable thermal expansibility, achieving a high matching of CTE with alumina. The introduction of zirconium can significantly improve the thermal stability of the adhesive matrix, and the Zr/Al ratio substantially affects the various reaction processes inside the adhesive, especially the types of zirconium-containing compounds. Only when the mass ratio of zirconium hydroxide to aluminum hydroxide was 3:7, most of the zirconium-containing compounds in A7Z3 adhesive were ZrO₂, which was the key reason it had the highest CTE. The room-temperature bonding strength of A7Z3 after heat treatment at 1500℃ reached 67.2 MPa. After pre-treatment at 1500℃, the high-temperature bonding strength of A7Z3 was above 50 MPa in the range of RT-1000℃. After 40 thermal cycles between RT and 1500℃, the bonding strength still reached 10 MPa. Physical bonding worked at temperatures below 1000℃, while chemical bonding dominated above 1000℃ based on the generation of Al₅BO₉ and mullite on the interfaces.