3D Printing of Liquid‐Metal‐in‐Ceramic Metamaterials for High‐Efficient Microwave Absorption

Abstract This work reports a gallium indium alloy (EGaIn)‐doped SiBOC ceramic that possesses a unique liquid‐metal‐in‐ceramic feature. The low‐viscosity liquid nature of gallium‐based liquid metals (Ga‐LMs) and the reactive core‐shell structure provide possibilities for phase engineering inside polymer‐derived ceramics. As a demonstration, EGaIn nanoparticles (NPs) are directly mixed with a UV‐curable ceramic precursor (UV‐PBS) to obtain a resin suitable for digital light processing 3D‐printing. After pyrolysis at 800–1200 °C, SiBOC ceramics with uniformly distributed EGaIn NP domains (Si(GaIn)BOC) are obtained. EGaIn plays a key role in promoting carbonization and preventing crack formation during the polymer‐to‐ceramic process, resulting in an increase in both ceramic yield and mechanical strength. EGaIn NPs are also found to have a core‐shell structure (EGaIn@(GaxIn1‐ x )2O3@SiBOC) inside the SiBOC matrix, which significantly enhances the dielectric properties and improves the interfacial polarization. As a result, an excellent electromagnetic wave absorption performance is achieved across the C, X, and Ku bands, respectively. Through rational design, a novel metastructure design based on the Schwarz P minimal surface is proposed, which exhibits an ultrawide effective absorption band extending up to 11.36 GHz (within C‐Ku bands).