Boosting Electromagnetic Wave Absorbing Capacity of Al₂O₃ Coating Through In Situ Generating Nano TiO_1.81 From Ti₂AlC MAX Phases

The narrow electromagnetic wave absorption bandwidth (EAB) of current dielectric loss type materials is desired to be optimized. Here, this study inventes one TiO_1.81/Al₂O₃ coating owning almost twice of the widest EAB reported among all the dielectric loss type materials. The fabrication process is composed of the supersonic atmospheric plasma spraying (SAPS) of Ti₂AlC/Al₂O₃ powders and following oxidation at 950 °C for 2 h in air. The occurred in situ double decomposition mechanism transformed Ti₂AlC (45 µm) into O-vacancy-defected TiO_1.81 (30 nm) and Al₂O₃ (200–500 nm). The interfacial polarization contribution is significantly enhanced due to the appearance of a huge amount of nano hetero-interfaces. The continuous outward diffusion of Ti and Al elements further endows the coating self-protective capacity through the formation of covered TiO_1.81 and Al₂O₃. As Ti₂AlC is one of 90 MAX phases, this work supports one wide window for fabricating wide EAB of coatings used in high temperatures.