Evaluation of Microwave Absorption Performance of Annealed Cr₂AlC at Different Temperatures

Abstract

Cr2AlC (CAC) has attracted increasing attention due to high conductivity and excellent oxidation resistance, which is useful for high-temperature microwave absorption. However, systematic research on microwave absorption performance of CAC at high temperatures is still lacking. In this work, CAC was synthesized by salt bath method followed by annealing at 500-950ºC. Effects of various annealing temperatures on compositions and electromagnetic properties were studied. Results revealed slight oxidation of CAC at annealing temperature of 500ºC, with formation of small amounts of Al2O3 and Cr2O3 on the surface. Increase in annealing temperature to 950ºC generated Al2O3 and Cr2O3 components in CAC. CAC annealed at 500ºC showed better microwave absorption properties than annealed at 950ºC and pure CAC. Effective absorption bandwidth (Reflection loss, RL< -10 dB) of CAC annealed at 500ºC was estimated to 2.3 GHz (9.7-12.0 GHz), and RLmin was -28.1 dB with thickness of 2.0 mm. The reason for this had to do with appropriate micro-oxidation, which could increase the permittivity of CAC and enhance dielectric loss capability for electromagnetic waves. In sum, these findings look promising to have referential significance for the application and promotion of CAC in the field of high temperature microwave absorption.

Rational Design of a Core–Shelled Ti3AlC2@La2Zr2O7 Composite for High-Temperature Broadband Microwave Absorption

“…). − Typical MAX phases include Ti 3 SiC 2 , Ti 3 AlC 2 (TAC), Cr 2 AlC, etc., with the coexistence of three bonding species (metallic, ionic, and covalent bonds), which result in a large number of unpaired defects and a considerable dipole polarization. , However, oxidation of the MAX phase at high temperatures may lead to phase decomposition and effective complex permittivity deterioration. Guo et al observed that Cr 2 AlC powders severely oxidized at elevated temperatures, with poor microwave absorption (MA) performance (EAB= 0) at 1–5 mm . Liu et al studied annealed Ti 3 SiC 2 powder at 500–700 °C and found a significant decrement in effective complex permittivity due to the reduction of highly conductive phases and the weakening of polarization relaxation .…”

“…Guo et al observed that Cr 2 AlC powders severely oxidized at elevated temperatures, with poor microwave absorption (MA) performance (EAB= 0) at 1−5 mm. 16 Liu et al studied annealed Ti 3 SiC 2 powder at 500−700 °C and found a significant decrement in effective complex permittivity due to the reduction of highly conductive phases and the weakening of polarization relaxation. 17 To solve the oxidation of the MAX phase, antioxidant ceramics have been widely used to enhance the stability of the MAX phase.…”