Fabrication of micron-scale honeycomb Si₃N₄ ceramics via ionotropic gelation technique

Unidirectionally-aligned silicon green bodies were prepared via ionotropic gelation reaction between sodium alginate and Ca²⁺. Then micron-scale Si₃N₄ honeycomb ceramics were obtained via direct nitridation of silicon during sintering. The influences of concentration of sodium alginate and content of silicon on the size of the pores were analyzed. The morphology and phase composition of green bodies and sintered bodies were determined by scanning electron microscopy and X-ray diffraction, respectively. The results show that the honeycomb ceramics with unidirectionally-aligned pores with the sizes of 20-60 μm and a porosity of 72.5% were fabricated under the optimized processing conditions.