Joule heating-driven ultrafast synthesis of high-entropy MAX phase as a robust electromagnetic wave absorber

MAX phases can benefit from high-entropy (HE) effects to enhance their electromagnetic (EM) wave absorption properties. This study introduces Joule heating-driven ultrafast synthesis (JHUS) for the first time to synthesize the novel HE-MAX phase (Ti_1/5Nb_1/5Ta_1/5Hf_1/5V_1/5)₂AlC at 1200°C in 20 s. The high-entropy effects, combined with the JHUS, lead to the formation of structural defects within the HE-MAX phase, such as lattice distortions, dislocations, and point defects. These structural defects play a crucial role in promoting dipole polarization. The high aspect ratio of the layered structure promotes electron transfer and interfacial polarization. These effects result in a significant improvement in EM wave absorption, with a minimum reflection loss of −46.07 dB at 2.7 mm and a 4.08 GHz absorption bandwidth at 1.5 mm. This study demonstrates an efficient and rapid method for synthesizing HE-MAX phases and explores the role of high-entropy engineering in optimizing their EM wave absorption.