Rufei Chen,Wenyan Duan,Gong Wang,Bingshan Liu,Yantong Zhao,Shan Li
Wave-transmitting materials are a kind of multi-functional materials that protect the normal operation of communication and guidance systems of spacecraft in harsh environments. In this paper, we fabricate a broadband microwave transparent Si 3 N 4 -SiO 2 composite ceramic with excellent performance through digital light processing (DLP) 3D printing technology. The influences of sintering temperature on the weight increase rate, density, dimensional shrinkage, phase composition, microstructure, bending strength and dielectric properties of Si 3 N 4 -SiO 2 ceramic were all systematically studied. The strength of Si 3 N 4 -SiO 2 ceramic sintered at 1350 ℃ was 77 ± 5 MPa. The relative permittivity of the ceramic is within the range of less than 4, and the loss tangent can be below 0.003. The 3D printed Si 3 N 4 -SiO 2 ceramic material exhibited excellent wave-transparent performance.
In this study, Zn 8 B 3 H 3 O 14 nanosheets were synthesized through a one-step coprecipitation process and employed as both a boron source and substrate templates for the fabrication of boron nitride nanosheets (BNNSs), which were synthesized efficiently at low temperatures by the borate nitration method using ammonia as the nitrogen source. The thickness of the synthesized BNNSs ranged from 3 to 10 nm with a flake dimension of about 2.56 μm. The prepared BNNSs using this method realized 98.8% boron source utilization and single batch yields up to gram level. In addition, BNNSs/SiO 2 microwave-transparent composites were prepared to investigate the potential for large-scale applications of the BNNSs produced by using this method. The composites demonstrated a remarkable increase in bending strength and fracture toughness, reaching 122.02 MPa and 2.31 MPa·m 1/2 , respectively, with the addition of only 0.5 wt% BNNSs. Compared with SiO 2 without BNNSs, the fracture toughness of the composites is increased by 106%. A novel crack plugging strong toughening mechanism of BNNSs is proposed. Simultaneously, the composites exhibit exceptional microwave-transparent properties, with dielectric constants below 4 in the real part and below 0.03 in the imaginary part. Therefore, this study has successfully achieved the low-temperature and efficient synthesis of micron-scale BNNSs, laying the groundwork for their large-scale application.
Aircraft confronting harsh meteorological conditions and radar detection environments during high-altitude flights face significant risks, which can threaten flight safety. This study designs and fabricates a novel Jerusalem cross-inspired Frequency Selective Surface (FSS). Initially, rGO powder with an optimized reduction degree is synthesized as the conductive filler. Based on this, the rGO/WPU electrothermal coating is prepared using the spraying method, demonstrating excellent electrical conductivity and electrothermal performance. Subsequently, a New Jerusalem Pattern Structure (NJPS) is engineered on the coating surface. This patterned design notably improved microwave transmittance. Parameter optimization ensured superior wave transmission performance, with the underlying mechanism explained through antisymmetric surface current analysis. Laser-engraved NJPS samples are tested under both room-temperature and low-temperature conditions, confirming dual functionality: effective Joule heating and stable broadband transmission. Importantly, icing wind tunnel tests under simulated flight conditions verified the de-icing capability within 216s via interfacial water-film lubrication. This patterning strategy establishes a viable methodology for reconciling electrothermal de-icing and electromagnetic transparency on aircraft surfaces.
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