Preparation of nasal cavity-like SiC–Si3N4 foams with a hierarchical pore architecture

Abstract

Rigid SiC–Si₃N₄ foams with hierarchical porosity were prepared through protein-based gel-casting followed by radiant sintering in a modified spark plasma sintering (SPS) set-up. The porous bodies sintered at 1500–1700 °C for only 10 minutes achieved a compressive strength of 15–21 MPa while keeping a porosity of 60–70 vol%. Gradient porous structures, with pore sizes ranging between 1 to 100 μm, were intersected by the growth of hybrid SiC and Si₃N₄ nanowires inside the pores resulting in a nasal cavity-like appearance. Gas permeability at room temperature (25 °C) and 600 °C was evaluated. Darcian permeabilities and non-Darcian permeabilities of all the prepared foams at room temperature fell within (0.354–1.55) × 10⁻¹² m² and (1.60–6.33) × 10⁻⁸ m, respectively. Measurement of the Darcian and non-Darcian permeabilities at 600 °C were much higher, at 1.71 × 10⁻¹¹ m² and 2.68 × 10⁻⁷ m, respectively. The microstructure, stability, gas flow properties and the green synthesis route reveal the potential of these ceramic foams to be used as industrial PM filters for airborne pollutions.