Synthesis and electromagnetic wave absorption performances of a novel (Mo0.25Cr0.25Ti0.25V0.25)3AlC2 high-entropy MAX phase

Abstract

• A new two-step solid state reaction process was proposed to synthesize single-phase high-entropy MAX phases. • A novel (Mo 0.25 Cr 0.25 Ti 0.25 V 0.25 ) 3 AlC 2 high-entropy MAX phase was successfully prepared. Investigations on electromagnetic (EM) wave absorption properties and effects of oxidation on EM wave absorption performances of (Mo 0.25 Cr 0.25 Ti 0.25 V 0.25 ) 3 AlC 2 were conducted for the first time. • (Mo 0.25 Cr 0.25 Ti 0.25 V 0.25 ) 3 AlC 2 powders exhibit excellent EM wave absorption properties, whose minimum reflection loss value can reach -45.80 dB (at 1.7 mm thickness) and maximum effective absorption bandwidth is 3.60 GHz (at 1.5 mm thickness). • After oxidation at 400-800°C, (Mo 0.25 Cr 0.25 Ti 0.25 V 0.25 ) 3 AlC 2 can retain good EM wave absorption properties in a certain frequency range. Herein, a novel kind of high-entropy MAX phases, (Mo 0.25 Cr 0.25 Ti 0.25 V 0.25 ) 3 AlC 2 powders were successfully synthesized by a newly proposed two-step solid state reaction process. The oxidation experiments demonstrate that the oxidation products of Al 2 Mo 3 O 12 and rutile TiO 2 are formed at about 600 and 800 ℃, respectively. Besides, the dielectric and electromagnetic (EM) wave absorption properties of (Mo 0.25 Cr 0.25 Ti 0.25 V 0.25 ) 3 AlC 2 powders and those after oxidation at different temperatures were also examined. The results show that the as-synthesized (Mo 0.25 Cr 0.25 Ti 0.25 V 0.25 ) 3 AlC 2 powders possess excellent EM wave absorption performances with the minimum reflection loss ( RL ) of -45.80 dB (at 1.7 mm thickness) and the maximum effective absorption bandwidth ( E AB ) of 3.6 GHz (at 1.5 mm thickness). After oxidation at 400-800 ℃, due to the coupling of conductivity loss and polarization loss, (Mo 0.25 Cr 0.25 Ti 0.25 V 0.25 ) 3 AlC 2 powders can retain good EM wave absorption properties in a certain frequency range. In this paper, the effects of oxidation on EM wave absorption properties of high-entropy MAX phases were systematically investigated for the first time. This work manifests that high-entropy MAX phases are promising EM wave absorbing candidates and can maintain good EM wave absorption performances after oxidation.