Synthesis of Si-C-N aligned nanofibers with preeminent electromagnetic wave absorption in ultra-broad band

As other one-dimensional materials, SiC-based nanofibers possess high temperature resistance and good electromagnetic wave absorption with the absorbing mechanism of polarization loss. To overcome the narrow effective absorbing broadband (EAB) and insufficient reflection coefficient (RC), a kind of Si-C-N aligned nanofiber rich in conducting networks and heterogeneous interfaces was designed to assemble the conductive loss and polarization loss in a proportion of 6 : 4. Synthesized via electrospinning combined with polymer-derived-ceramic methods, the prepared nanofibers showed good degree of orientation, a small diameter less than 300 nm and a multiphase structure containing SiC crystallites, Si3N4 crystallites, a carbon phase and an amorphous Si-O-C-N phase. The crystallization, chemical composition and absorbing performance of nanofibers heat-treated at 1300-1600 °C were investigated in detail. The Si-C-N aligned nanofibers with a small thickness of 2.3 mm prepared at 1300 °C represented prominent absorption that the minimum RC sank down to -54.24 dB at 17.84 GHz, while 3.0 mm-thick nanofibers heated at 1500 °C exhibited ultra-broad EAB that went up to 8.93 GHz (cover 9.07-18 GHz). With the thickness varying from 2.5 mm to 10 mm, EAB gradually shifted from high frequency to low frequency in the measured band of 2-18 GHz. The synergistic effect of conductive loss, polarization loss and good impedance matching contributed to the performed ultrawide EAB and strong absorption. The prepared Si-C-N nanofibers are considered promising candidates of high-temperature-stable absorbents under harsh conditions.