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 adhesives are critical materials in the aerospace field. The zirconium-modified aluminum phosphate-based adhesives developed in this work had the advantage of adjustable thermal expansibility, achieving a high matching of coefficient of thermal expansion (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. Most of the zirconium-containing compounds in the A7Z3 adhesive were ZrO₂ only when the mass ratio of zirconium hydroxide to aluminum hydroxide was 3 : 7, which was the key reason why it had the highest CTE. The room-temperature bonding strength of A7Z3 after heat treatment at 1500 °C reached 67.2 MPa. After pretreatment at 1500 °C, the high-temperature bonding strength of A7Z3 was greater than 50 MPa in the range of (room temperature) RT–1000 °C. After 40 thermal cycles between RT and 1500 °C, the bonding strength still reached 10 MPa. Physical bonding occurred at temperatures below 1000 °C, while chemical bonding dominated above 1000 °C based on the generation of Al₅BO₉ and mullite at the interfaces.