Stacking-Fault Engineering in SiC Nanowire Aerogels for Efficient Microwave Absorption.

Microwave absorbers that combine low density, high efficiency, and thermal robustness are highly desirable for aerospace and other extreme environment applications yet are challenging to achieve simultaneously with conventional carbonaceous or magnetic materials. Here, we report an all-ceramic SiC nanowire aerogel (SiC NWA) with highly efficient microwave absorption achieved through controlled heat treatment in an argon atmosphere. By regulating the stacking fault density in SiC nanowires without introducing any secondary phase, the dielectric response and impedance matching of the aerogel can be simultaneously tuned. Heat treatment progressively reduces the density of stacking faults associated with the 2H-SiC segments insertion in the 3C-SiC matrix, thereby suppressing excessive dielectric response and driving the absorber from a severely mismatched state toward a near-optimally matched one. As a result, the optimized aerogel achieves a minimum reflection loss of -64.1 dB and an effective absorption bandwidth of 4.2 GHz, fully covering the X-band. It also possesses an ultralow density of 10 mg·cm-3 and excellent thermal stability in air up to 1200 °C while retaining efficient room-temperature microwave absorption after butane-flame ablation. This work demonstrates an ultralight, thermally stable, and highly efficient all-ceramic SiC nanowire aerogel with strong potential for microwave absorption applications involving thermal exposure.