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, kR ≈ 6.26 W·m−1·K−1), a superior flexural strength (σL ≈ 29.4 MPa), and a relative high anisotropic ratio of TC (kR/kL = 4.1). The orientation dependence of the microstructure-property relations may offer a promising perspective for the fabrication of multifunctional ceramics.

Ultrastrong, biomorphic cellular silicon carbide (bio-SiC) ceramics were generated by the carbothermal reduction of gaseous SiO with a pyrolytic carbon template. The anisotropic wood tissue microstructure is replicated in the bio-SiC materials, in which almost fully dense cell walls are assembled by directional columnar SiC nanocrystalline structures that are 100–200 nm in diameter and 100–500 nm in length. The resulting bio-SiC ceramics exhibited high porosity (76%∼86%), superior flexural strength to other materials (σ|| ≈ 38.3 MPa), high thermal dissipation characteristics (k ⊥ ≈ 10.3 W·m–1·K–1 at room temperature), and high anisotropic thermal conductivity (k ⊥/k || , ∼1.6). The orientation dependence of the microstructure–property relations may offer a promising perspective for the fabrication of multifunctional ceramics and composites.

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Porous SiC ceramics were prepared by a new approach combination of carbothermal reduction and subsequent recrystallization sintering. Firstly, micro-sized SiC particles were used as the skeleton, and SiC spherical nanocrystals were in-situ synthesized by the vapor-solid reaction between carbon nanoparticles and silicon monoxide vapor. The shape and diameter of SiC nanocrystals are related to the pristine carbon nanoparticles, showing a shape memory effect. After recrystallization sintering, high purity α-SiC porous ceramics with tailored necking area were obtained by the evaporation-condensation of SiC nanocrystals. A linear relation was revealed between the flexural strength and the value of d/d 0 of porous recrystallized SiC (RSiC) ceramics (the neck diameter to coarse micron-sized grains diameter ratio). The necking area and d/d 0 value increased with the SiC nanocrystals content, due to the higher saturated vapor pressure resulted in high mass mobility to neck area of SiC nanoparticles. As a result, a remarkable value of d/d 0~9 9% and outstanding flexural strength of 75.7 MPa could be achieved for the porous RSiC ceramics with~42% porosity by adding 20 wt.% nano-sized SiC sintered at 1950°C for 2 h.