Fei Li

Although 3D printing enables the flexible manufacturing of ceramic components, the fabrication of complex, large-span ceramic structures usually requires additional supports, leading to high production costs, low efficiency, and increased defect rates. Herein, an ultraviolet (UV)-based in situ photocuring-assisted direct ink writing (DIW) method was developed for shaping alumina-filled photocurable slurries into preceramic composites, which were subsequently debound and sintered into alumina ceramics. The effects of the slurry composition and processing parameters on curing depth and printing accuracy were systematically investigated, and the mechanical properties of the cured and sintered samples were compared. The results showed that the curing depth decreased with increasing photoinitiator and alumina powder content but increased with prolonged UV irradiation time. Due to the increase in viscosity with the increase in alumina content, the flowability of the slurry before solidification decreases, and the printing accuracy increases. The cured composites exhibited good mechanical integrity. After debinding and sintering, the bending modulus and bending strength increased from approximately 125 MPa and 5 MPa for the cured composites to about 200 GPa and 38 MPa for the sintered ceramics, respectively. The linear shrinkage of the sintered sample was around 20%. Using the optimized slurry, various unsupported structures—including discs, solid rectangles, triangular frames, L-shaped brackets, and a 12.5 cm high vase—were successfully printed without any supports. All printed structures exhibited good continuity and integrity, demonstrating the proposed method as a promising route toward the low-cost and efficient manufacturing of alumina ceramic components.

Covalent organic framework materials (COFs) are promising for pollutant adsorption owing to their high specific surface area, tunable pores and functional designability, but their microcrystalline powder form leads to poor mechanical strength and processability, limiting practical applications. This study presents a mild, eco-friendly strategy using polysulfonamide fiber (PSA) with excellent mechanical and thermal stability as the core matrix, and room-temperature-synthesized sulfonic acid-functionalized TFP-DABA-COFs as the shell layer. Via coaxial wet spinning, core–shell structured PSA-COF composite fibers were fabricated without harsh solvothermal conditions, improving COF dispersion and interfacial bonding. Characterizations revealed the fibers possessed favorable comprehensive properties: fracture strength of 14.97 MPa, elongation at break of 32.84%, specific surface area of 8 m²/g, and hierarchical porous structures dominated by micropores, with enhanced hydrophilicity beneficial to aqueous adsorption. Adsorption experiments on woven fabrics showed 93.6% methylene blue removal in 40 min and 98.9% in 120 min, following the quasi-second-order kinetics, indicating chemisorption (electrostatic attraction) as the main mechanism. This work provides a mild, green approach to prepare PSA-COFs core–shell fibers, effectively solving the formability and processing issues of COFs.