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Compared with optical black, few attempts have focused on achieving broadband microwave blackbodies. In this study, all‐ceramic metamaterial microwave blackbodies are created by integrating a graded Gyroid shellular (GGS) metastructure design with additive manufacturing of polymer‐derived SiOC (PDCs‐SiOC) ceramics encapsulated by Si3N4 (SiOC@Si3N4). Hardly influenced by the destructive interference effect, as‐fabricated GGS‐structured SiOC@Si3N4 microwave blackbodies demonstrate a broadband microwave absorption (MA) above 83.6% (91.3% on average) across the entire X‐Ku band and encompassing higher frequencies above 18 GHz as well, together with the temperature insensitivity from room temperature to 500 °C. Based on the flexible electromagnetic tunability of PDCs‐SiOC, exceptional structural scalability is experimentally validated for metal‐doped modified CuSiOC and CoSiOC substrates with the same GGS metastructures, retaining high‐efficiency MA capability. Furthermore, attachment of perfectly reflecting metal backplanes further enhances the MA performance, with an ultrawide MA exceeding 67.9% (89.1% on average) achievable at 2.95–18 GHz for CoSiOC substrate. Meanwhile, the GGS‐structured SiOC@Si3N4 metamaterials possess additional multifunctional properties, such as good noise reduction performance as well as ultrahigh wear resistance. As a proof of concept, this study provides important guidance on achieving multifunctional coupling broadband MA characteristics by fully tapping the application potential of existing materials. [ABSTRACT FROM AUTHOR]

This article reports a novel method for three‐dimensional (3D) printing of continuous fibers into ceramics to improve the mechanical properties of printed ceramics, which is difficult in other 3D printing technologies. The ceramics were derived by pyrolysis of thermoplastic ceramic precursor feedstocks, which were prepared by two methods. One is homogeneously mixing thermoplastic resins and ceramic precursors. The feedstocks prepared by this method exhibit good thermoplastic properties and can be extruded into filaments. Ceramics were obtained by heating the feedstocks to 1100°C in argon atmosphere. The ceramics were amorphous and remained stable during 1100‐1300°C; at 1400°C they decomposed into β–SiC with simultaneous volatile gas generation. Above 1400°C, their quality decreased significantly due to cracking of ceramic skeletons. The other method is directly heating, extruding and printing the ceramic precursor. The precursors showed good printability and complex ceramic structures were printed with continuous carbon fibers inside. The continuous carbon fibers improved the flexural strength of pyrolytic ceramics, which is about 7.6 times better than that of the ceramics without fibers. The novel method unravels the potential of 3D printing of continuous fibers into ceramics with complex lightweight structures to improve the strength. [ABSTRACT FROM AUTHOR]

The study investigates the effect of carbon nanotubes on chloride penetration in nano-modified mortars and reports on the physical, electrical, and mechanical performance of the material. Mortars were artificially corroded and their surface electrical surface conductivity as well as flexural and compressive strength were measured. The influence of variable nanotube concentration in accelerated corrosion damage was evaluated. Nanotube concentration was found to significantly affect the permeability of the mortars; improvements in flexural and compressive response of mortars exposed to salt spray fog, compared to virgin specimens, were rationalized upon decreases in the apparent porosity of the materials due to filling of the pores with sodium chloride. Electrical resistivity was found to increase up to two orders of magnitude with respect to the surface value; above the percolation threshold, the property impressively increased up to five orders of magnitude. [ABSTRACT FROM AUTHOR]