Anisotropic, biomorphic cellular Si₃N₄ ceramics with directional well-aligned nanowhisker arrays based on wood-mimetic architectures

Inspired by the transport behavior of water and ions through the aligned channels in trees, we demonstrate a facile, scalable approach for constructing biomorphic cellular Si₃N₄ ceramic frameworks with well-aligned nanowhisker arrays on the surface of directionally aligned microchannel alignments. Through a facile Y(NO₃)₃ solution infiltration into wood-derived carbon preforms and subsequent heat treatment, we can faultlessly duplicate the anisotropic wood architectures into free-standing bulk porous Si₃N₄ ceramics. Firstly, α-Si₃N₄ microchannels were synthesized on the surface of C_B-templates via carbothermal reduction nitridation (CRN). And then, homogeneous distributed Y-Si-O-N liquid phase on the walls of microchannel facilitated the anisotropic β-Si₃N₄ grain growth to form nanowhisker arrays. The dense aligned microchannels with low-tortuosity enable excellent load carrying capacity and thermal conduction through the entire materials. As a result, the porous Si₃N₄ ceramics exhibited an outstanding thermal conductivity (TC, k_R ≈ 6.26 W·m^-1·K^-1), a superior flexural strength (σ_L ≈ 29.4 MPa), and a relative high anisotropic ratio of TC (k_R/k_L = 4.1). The orientation dependence of the microstructure-property relations may offer a promising perspective for the fabrication of multifunctional ceramics.