Microwave absorption ceramics pyrolyzed from poly(dimethylsilylene)diacetylene‐modified hyperbranched polyborosilazane

Abstract Polymer‐derived ceramics (PDCs) are typically prepared as ceramic‐based microwave absorption materials by doping with high‐dielectric materials or transition metals, which may lead to the issue of uneven mixing. This study achieves uniform blending at the molecular level by using poly(dimethylsilylene)diacetylenes (PDSDA) to modify hyperbranched polyborosilazane (PBSZ). The alkynyl group and Si−H bonds crosslink to form a ceramic precursor, which is then pyrolyzed to prepare SiBCN ceramics with excellent microwave absorption performance and high temperature stability. The introduction of PDSDA significantly improved the ceramic yield, resulting in the in situ formation of more ordered carbon, SiC nanocrystals, and ceramic nanowires within the SiBCN ceramics. These nanophases are uniformly dispersed throughout the ceramic matrix, enhancing the ceramic's dielectric loss and microwave absorption properties. After pyrolyzed at 1400°C, the ceramic derived from the precursor with a PBSZ:PDSDA mass ratio of 10:1 exhibits excellent electromagnetic wave absorption properties, with a minimum reflection loss of −50.11 dB and a maximum effective absorption bandwidth of 3.11 GHz. Moreover, ceramics maintain excellent stability at 1500°C in both argon and air environments. This study fully exploits the designability of precursor molecules, providing a new approach for the preparation of microwave absorption materials from PDCs route.