Microstructure, thermal, and mechanical properties of hierarchical porous silicon carbide made by direct ink writing

Abstract

Hierarchical porous silicon carbide (SiC) ceramics were fabricated by combining particle-stabilized emulsions and three-dimensional (3D) printing. Direct ink writing (DIW) was used as the 3D printing technique. The formulation for successful printing is discussed in relation to the rheology of the emulsions. The SiC emulsions were able to be printed with a lower storage modulus (G′) and apparent yield shear stress (τ_y) than previously reported SiC ink pastes. The printed and sintered porous SiC ceramics possess a total porosity of 73.7% with an average pore size within the filaments of 2.2 µm in diameter. A hierarchical pore structure that contains pore sizes of about 250 µm, around 1–10 µm and smaller than 0.5 µm can be observed in the microstructure and pore size distribution. The mechanical properties showed a good strength-to-density ratio, and the thermal conductivity was reduced to 4.9 W/m·K. This study provides a new reliable approach for fabricating hierarchical porous SiC ceramics with low thermal conductivity.