In-situ flowering of RGO with 3D distribution: Towards super-broadband microwave absorption and ultralight synergy in aramid honeycomb

The application of microwave absorption (MA) materials in realistic aerospace scenarios would be difficult without a reliable mechanical carrier. However, achieving broad effective absorption bandwidth (EAB) of the aramid honeycomb at low weight gain is still a significant challenge. Herein, we achieved rapid in-situ flowering of RGO with 3D distribution in honeycomb holes by optimizing the hydrophilic thermal (HDT) N2H4·H2O reduction process, making full use of the internal space of the honeycomb. The synergy of super-broadband MA and ultra-light in aramid honeycomb can be achieved by filling the 3D macro-dispersed flower-like RGO without other media. In the frequencies of 2–18 GHz, the minimum reflection loss (RLmin) of −48.38 dB was obtained in a 3% (w/w) RGO-filled honeycomb at 14.80 GHz, with a thickness of 5.2 mm. Moreover, the 3% (w/w) RGO-filled honeycomb composites achieve a broad EAB of 13.84 GHz at the thickness of 9.0 mm with only 3% increase in weight. Actual and simulated MA performance verifies the uniformity and reliability of the foamed RGO-filled honeycomb composites, where the power loss of the composites is mainly based on the conductive losses and multiple polarization from the macroscopic distribution of RGO. The electromagnetic parameters of the foamed RGO-filled honeycomb can precisely be controlled through the weight gain of GO impregnation. Compared to ordinary impregnated coatings with high weight gain, this study provides a simple and effective pathway for preparation of MA honeycomb structures with weight gain less than 4%, which have a significant potential in the field of aerospace stealth. [Display omitted] •Rapid in-situ reduction and foam filling of RGO in honeycomb holes at low hydrazine concentration was achieved.•RGO-filled honeycomb structure achieves a broad EAB of 13.84 GHz at the thickness of 9.0 mm with only 3% increase in weight.•The electromagnetic parameters of honeycomb composites can be precisely controlled.•Foamed RGO-filled honeycomb composites are expected to be used as aviation stealth materials.