Carbon nanowire modified Nextel 610/SiOC composites with gradient periodic structure for enhanced broadband electromagnetic-wave absorption performance at elevated temperatures

For electromagnetic wave absorbing ceramic matrix composites, it is crucial to control the loss mechanism to achieve stable high-temperature broadband absorption performance. In this work, multiscale structural design is utilized to enrich EMW loss mechanism, synergistically improving the EMW absorption capacity and bandwidth. Firstly, based on the tunability of the fiber preform, three-dimensional carbon fiber periodic units were constructed on an N610 fiber cloth. Then, the intrinsic electromagnetic properties of the N610 fibers were modified by introducing nanoscale absorption units, namely carbon nanowires. The carbon nanowires were diffusely distributed in transparent N610/SiOC composites by controlling the reaction conditions, forming a large number of heterogeneous interfaces and conductive networks. The carbon fiber and carbon nanowires, together with the notable conductivity difference with respect to the N610/SiOC composites, significantly enhance the polarization loss and conductive loss. Besides, the periodically arranged carbon fibers can trap the incident EMWs and reduce their transmission, promoting reflection, scattering, and absorption. The designed N610/SiOC composites exhibit superior EMW absorption performance from room temperature to 600 ℃, with a reflection loss less than −8 dB across the entire investigated band and an effective absorption bandwidth exceeding 10.7 GHz at 4–18 GHz. This innovative multiscale design approach, characterized by a discrete distribution of absorbing units with a high electronegativity difference, represents a fresh avenue for advancing the development of high-temperature and wide-band EMW-absorbing CMCs.