Microwave absorption and infrared stealth capabilities of hot-pressed Si₃N₄/CNT ceramics tailored by CNT content

Current research on radar and infrared dual stealth in dense Si₃N₄-based ceramic materials is limited. This study investigates the influence of carbon nanotubes (CNTs) on the composition, microstructure, electromagnetic wave absorption (EMA) capabilities, and infrared emissivity of hot-pressed Si₃N₄-based ceramics. The addition of CNTs resulted in the formation of numerous heterogeneous interfaces and the CNTs conductive network, initially enhancing the ceramics’ EMA capabilities before gradually decreasing. Si₃N₄-based ceramics loaded with 0.5 wt% and 1 wt% CNTs exhibited significant EMA capabilities, with a minimum refection loss of −60.95 dB at thickness of 7.49 mm. However, with an increase in CNT content, the increasing heterogeneous interfaces and pores in ceramics enhanced the absorption of the electromagnetic wave in the infrared band, resulting in a rise in total infrared emissivity from 0.584 to 0.679. To optimize radar and infrared stealth performance, a two-layered structure can be designed, with Si₃N₄ and Si₃N₄/CNT ceramics serving as the outermost and second layers, respectively. This study provides a way to design high density Si₃N₄-based ceramics with infrared and radar stealth.