Preparation of Si3N4-based ceramic skin-core sandwich structures via Digital Light Processing (DLP) 3D printing

The synergistic optimization of broadband electromagnetic wave transmission and high mechanical strength is a key challenge in radome fabrication. This challenge was addressed through a dual-approach: compositional optimization by doping silicon dioxide (SiO 2 ) into a Silicon nitride (Si 3 N 4 ) matrix, and structural design via an innovative skin-core sandwich architecture with a porous core. High-precision fabrication of this structure was realized using Digital Light Processing (DLP) 3D printing technology, and the slurry formulation and modification process were systematically optimized. A composite modification protocol, comprising stearic acid (SA) dry milling (20 h) and subsequent KH560 wet milling (20 h), was demonstrated to yield a slurry with a solid loading of 47 vol%, a viscosity of 8.87 Pa s (at a shear rate of 30 s −1 ), and a maximum curing depth of 89 μm. During printing, a curing depth of 65 μm was utilized. A layer thickness equivalent to one-third of this curing depth was selected, which resulted in green bodies characterized by excellent interlayer bonding and an absence of visible layer lines. After sintering, the obtained Si 3 N 4 ceramic sandwich structure exhibited outstanding comprehensive properties. Flexural strengths of 300.19 MPa and 36.15 MPa were measured for the skin and the porous core, respectively. Over the frequency range of 7-15 GHz, the average values of relative dielectric constants of 4.25 and 2.73 were recorded, with the corresponding average dielectric loss tangents of 0.0186 and 0.0054, thereby confirming that the core was successfully designed for low permittivity and low loss. Consequently, an. effective technical pathway for the design and fabrication of high-performance radome components is provided by this study.