Phase-separation-enabled hollow silicon carbide composite nanofibers with multiscale interfaces for electromagnetic wave absorption over a wide temperature range

Silicon carbide (SiC) nanofibers are attractive for electromagnetic wave (EMW) absorption in harsh environments, but the controllable construction of hollow architectures and the enhancement of dielectric loss remain challenging. Herein, phase-separation-enabled hollow SiC composite nanofibers with multiscale interfacial structures were developed to address these issues. By combining phase-field simulations with experiments, liquid-liquid phase separation was identified as the key factor governing radial compositional segregation and hollow-fiber formation, enabling controllable regulation of the phase constitution, defect density, and interfacial structure through the precursor ratio. The hollow architecture, together with the resulting multiscale interfaces and abundant defects, synergistically enhanced dielectric loss and improved impedance matching. At a PVP/PSN mass ratio of 2:1, the sample obtains a minimum reflection loss of -56.11 dB at 1.53 mm, while the 1:1 hollow fiber delivered the broadest effective absorption bandwidth of 4.96 GHz at 1.39 mm. After incorporation into an AlPO4 matrix, the optimized fibers enabled stable EMW absorption from 298 to 873 K, with a maximum effective absorption bandwidth of 4.08 GHz in the X-band. This work demonstrates a controllable route for constructing hollow silicon carbide-based fibrous absorbers and provides insight into multiscale interfacial design for EMW absorption over a wide temperature range.