In situ synthesised aluminium borate hollow whiskers reinforced aluminium phosphate wave-transparent ceramics

As one of the wave-transparent ceramic materials, aluminium phosphate ceramics has excellent electrical and thermal properties. However, its application in aerospace is often limited due to insufficient mechanical performance. Al₅BO₉ hollow whiskers are introduced into AlPO₄ ceramics via in situ synthesis. The mechanical of the material was significantly enhanced by introducing in situ hollow whiskers and optimising whisker distribution. This work explains the formation mechanism of whisker hollow structures using Frank's capillary equilibrium theory. Subsequently, the mass transfer process of boron oxide is discussed through the periodic bond chain theory, leading to the in situ synthesis of hollow whisker clusters with wall thickness and tube diameter of approximately 700 nm from an AlPO₄ matrix. The enhanced composite exhibited excellent mechanical performance, with a flexural strength of 347 MPa, representing a 61.17 % improvement in mechanical strength compared with AlPO₄ ceramics enhanced by external Al₅BO₉ whiskers, while maintaining the intrinsic dielectric properties of aluminium phosphate. In conclusion, this study proposes a high-strength and wave-transparent Al₅BO₉/AlPO₄ composite material.