Fabrication and multifunctional applications of wood-derived Si3N4 ceramics with the morphology of whalebone

Si 3 N 4 ceramics with multiple aperture sizes demonstrate significant potential in high-temperature filtration applications. The bio-template method is an effective strategy for fabricating porous ceramics with complex structures. Herein, we successfully utilized nitrogen gas and SiO vapor to perform carbothermal reduction nitridation reactions with carbonized wood, resulting in a biomimetic, anisotropic, high-strength, hydrophobic, high-temperature resistant, and high-purity porous Si 3 N 4 ceramic. During the preparation process, the surface layer of the carbon template is initially converted into α-Si 3 N 4 . Subsequently, with the assistance of sintering aid Y 2 O 3 , α-Si 3 N 4 undergoes a dissolution-precipitation mechanism to form β-Si 3 N 4 whiskers. This process exposes the inner carbon layer, enabling it to react with the gas phase and ensuring complete transformation into Si 3 N 4 . Unlike other preparation methods, this ceramic inherits the highly ordered honeycomb structure of natural wood while self-assembling whalebone-like β-Si 3 N 4 nanowhisker arrays on elongated channel walls, achieving an exceptional flexural strength value of 32.7 MPa. Furthermore, this lightweight ceramic not only holds promise for oil-water separation but also exhibits outstanding thermal conductivity (7.6 W m −1  K −1 ) and excellent gas permeability ( k 1  = 0.20 × 10 −12  m 2 , k 2  = 1.84 × 10 −8  m) due to its longitudinally aligned microchannels. This ceramic achieves ultra-high filtration efficiency (99 %) for PM 0.5 particles, attributed to the arrangement of whalebone-like whiskers that effectively capture smoke particles and promote nucleation on the whiskers. This work provides a foundation for designing and developing biomimetic structured porous ceramics with multifunctional properties.