Structural design and simulation of ultra-broadband TiCxN1-x fibers/Si3N4 high-temperature microwave absorbing composites

Currently, high-temperature ceramic-based microwave-absorbing composites face limitations such as a limited range of material systems and narrow effective absorption bandwidth, which hinder their further application in electromagnetic wave absorption field under high-temperature environments. Herein, guided by electromagnetic simulation, a lightweight (1.61 g/cm3), ultra-broadband (32.45 GHz) high-temperature (800 °C) meta-structure TiCxN1-x fibers/Si3N4 microwave-absorbing composite was prepared by combining material composition and structural design with the quick gel casting process (20 min). Density functional theory calculations confirmed the presence of strong interfacial bonding (− 1.77 J/m2) between TiCxN1-x fibers and the matrix. After introducing only 4 wt% TiCxN1-x fibers, the flexural strength and fracture toughness of the composite sample increased by 56.24% and 111.48%, respectively. Moreover, the sample exhibited superior electromagnetic wave absorption performance in the Ku-band at 800 °C compared to room temperature. Based on the electromagnetic parameters of the sample introducing 4 wt% TiCxN1-x fibers and the results of electromagnetic simulation calculations, a sample with a trapezoidal pyramidal meta-structure of 180 mm × 180 mm was designed and fabricated. An ultra-wideband (8.25 ~ 40 GHz, X, Ku, K, and Ka) effective absorption for electromagnetic wave in the 2 ~ 40 GHz frequency range was achieved, which is in good agreement with the electromagnetic simulation results. This study offers a fresh approach to designing lightweight, ultra-wideband, structural–functional integrated ceramic-based microwave absorbing composites for high-temperature environments.