Construction of EG/SiOC@C porous structure by direct ink writing and in-situ vapor self - Deposition to enhance microwave absorption

In this work, expanded graphite (EG) was dispersed inside modified polysiloxane resin and successfully printed various cellular structures with span feature via ultraviolet-thermal field co-assisted direct ink writing. The carbon-rich layer was in-situ deposited in the designed porous structure surface by no gas flow pyrolysis process. The characterization of Raman and X-ray photoelectron spectroscopy indicate that the deposited cladding structure possessed amounts of sp2-C, and mainly bonds to the matrix in the manner of Si–C. The presence of cladding structure played a vital role in enhancing the electric conductivity and interface polarization, resulting in excellent microwave absorption performance. The addition of expanded graphite also improved the dielectric property by reinforcing the internal interfacial polarization and achieving a good impedance matching. Finally, the structure reached a minimum reflection loss of −59.31 dB at the thickness of 2.8 mm, and a broadband absorption of 4.2 GHz in the X-band (8.2–12.4 GHz) at 3.1 mm, covering the whole X band. The novelty strategy of controlling the surface state by pyrolysis vapor self-deposition can open a new avenue to tailor the functional characteristic of materials, especially on the assist of direct ink writing which can easy realize complex structural geometry on-demand.