Multi-phase Engineering and Microstructural Modulation in Fe-C-N multiphase composite for efficient microwave absorption

To tackle the complex electromagnetic pollution from advances in radar and network technologies, a simple, low-cost, and efficient absorbing agent has been developed. By optimizing the high-temperature sintering of the melamine/reduced iron powder composite system, we successfully created a Fe-C-N multiphase composite material with multi-level structure and dielectric-magnetic loss properties. The gas produced by the decomposition of melamine at high temperatures fosters the formation of a pore structure. Additionally, controlling the heating temperature and holding time effectively manages the phase transition path, allowing for synergistic evolution of the microstructure and regulation of the microwave-absorbing properties. The analysis of SEM images and XRD results identifies the synergistic enhancement mechanism between the multi-level structure and multi-phase. This endows a reflection loss of -75.91   dB at 5.16   GHz for samples held at 700°C for 3   hours (thickness 4.4   mm), with a maximum bandwidth of 4.92   GHz (1.6   mm). It avoids the traditional multi-step process of carbon/nitrogen doping, effectively regulating the phase transition path and microstructure evolution. This provides a new approach to develop lightweight, broadband microwave absorbing materials.