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

Abstract

Abstract 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 CB-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 (σL ≈ 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.

Keywords

• silicon nitride
• anisotropic
• carbothermal reduction nitridation (CRN)
• wood
• nanowhisker arrays