1D CNT-Expanded 3D Carbon Foam/Si 3 N 4 Sandwich Heterostructure: Utilizing the Polarization Compensation Effect for Keeping Stable Electromagnetic Absorption Performance at Elevated Temperature.

Modern electromagnetic (EM) absorbing materials (EAMs) are experiencing a revolution triggered by advanced information technology. Simultaneously, the diverse harsh EM application scenarios entail a more stringent appeal of practicability to EAMs, especially under high-temperature conditions. Therefore, exploring EAMs with both excellent absorbing performance and practicability at elevated temperatures is necessary. Herein, a novel 3D porous carbon foam/carbon nanotubes@Si 3 N 4 (CF/CNTs@Si 3 N 4 ) heterostructure was constructed by the chemical vapor infiltration process. The optimally grown 1D CNTs embedded in 3D CF/Si 3 N 4 are utilized to provide abundant nanointerface coupling effects to compensate for the excessive increase in the conductive loss during rising temperature to realize a self-adjustment in response to high temperature. A high-efficiency EM absorption over a wide temperature range from 25 to 480 °C was achieved (with a ≥90% absorbing ratio covering the whole X-band). In addition, the Si 3 N 4 coating can improve the thermal stability of the carbon matrix and maintain the tailored inner structure. Multiple investigations into other environmental adaptabilities also exhibited the application perspective of such a heterostructure. This work points out a new strategy for preparing designable, efficient, and high-temperature applicable EAMs, promoting the diverse development of electronic devices.