Polymer-derived SiOC reinforced with core-shell nanophase structure of ZrB/ZrO for excellent and stable high-temperature microwave absorption (up to 900 °C).

Microwave absorbing materials for high-temperature harsh environments are highly desirable for aerodynamically heated parts and engine combustion induced hot spots of aircrafts. This study reports ceramic composites with excellent and stable high-temperature microwave absorption in air, which are made of polymer-derived SiOC reinforced with core-shell nanophase structure of ZrB/ZrO. The fabricated ceramic composites have a crystallized t-ZrO interface between ZrB and SiOC domains. The ceramic composites exhibit stable dielectric properties, which are relatively insensitive to temperature change from room temperature to 900 °C. The return loss exceeds - 10 dB, especially between 28 and 40 GHz, at the elevated temperatures. The stable high-temperature electromagnetic (EM) absorption properties are attributed to the stable dielectric and electrical properties induced by the core-shell nanophase structure of ZrB/ZrO. Crystallized t-ZrO serve as nanoscale dielectric interfaces between ZrB and SiOC, which are favorable for EM wave introduction for enhancing polarization loss and absorption. Existence of t-ZrO interface also changes the temperature-dependent DC conductivity of ZrB/SiOC ceramic composites when compared to that of ZrB and SiOC alone. Experimental results from thermomechanical, jet flow, thermal shock, and water vapor tests demonstrate that the developed ceramic composites have high stability in harsh environments, and can be used as high-temperature wide-band microwave absorbing structural materials.