DLP–printable hyperbranched polyborosilazane for microwave absorbing SiBCN(O) ceramic metastructure

This work introduces a novel digital light processing (DLP) printable SiBCN(O) ceramic precursor (UV-hPBSZ), derived through a straightforward aminolysis approach. The unique hyperbranched molecular structure of UV-hPBSZ leads to remarkable UV curing efficiency, excellent printability, satisfied ceramic yield, and consistent shrinkage ratio. UV-hPBSZ also exhibits superior resistance against cracking and collapse during the polymer-to-ceramic process, thus enabling the fabrication of intricate SiBCN(O) ceramic structures. Upon pyrolysis at 1200 °C, the resulting SiBCN(O) ceramic demonstrates outstanding electromagnetic wave (EMW) absorption performance, achieving full coverage in the X band (RL_min = -36.68 dB). To showcase the design flexibility, a distinctive metastructure is proposed and successfully fabricated using DLP printing technique. This SiBCN(O) metastructure absorber enables impressive EMW absorption in the Ku band (94.6 % coverage), attributed to surface resonance effects and multiple internal reflections. Moreover, SiBCN(O) ceramics exhibit excellent high-temperature stability, with less than a 1.63 % total mass change from room temperature to 1400 °C. UV-hPBSZ offers a simple but versatile way to control dielectric properties, which opens up new possibilities for multifunctional integrated EMW absorbers suitable for both ambient and high-temperature conditions.