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 degrees C reached 67.2 MPa. After pretreatment at 1500 degrees C, the high-temperature bonding strength of A7Z3 was greater than 50 MPa in the range of (room temperature) RT-1000 degrees C. After 40 thermal cycles between RT and 1500 degrees C, the bonding strength still reached 10 MPa. Physical bonding occurred at temperatures below 1000 degrees C, while chemical bonding dominated above 1000 degrees C based on the generation of Al5BO9 and mullite at the interfaces.