Reconstructed Hierarchical Pore Structure of Porous SiC Ceramics Using Micro-X-Ray Computed Tomography

Porous ceramics prepared by freeze casting are strongly appealing for filtration, separation, heat insulation, energy storage, and bioengineering. Herein, a unidirectionally freeze-casting process is effectively adopted to fabricate porous silicon carbide (SiC) ceramics. The freezing rates of 0.29, 1.59, and 22.80 degrees C min(-1) are presented at the bottom, which are simulated by finite-element analysis. The pore structure characterize is systematically investigated through the 3D-reconstructed micro-X-Ray computed tomography. Porous SiC ceramics with reasonable densification present the layer-stacked texture and the hierarchical interconnected porous structure. The pore sizes are in the range of 30-40 mu m. With the decreasing of freezing temperatures, the pore sizes reduce, while the number of channels increases. After sublimation of the fine ice crystals, there are a large number of channels (5-10 mu m). The open porosities decrease from 82.3% to 78.2%, and a maximum compressive strength of 1.97 MPa is obtained. The pore size distribution is bimodal at the top and bottom of porous ceramics. The surface of porous SiC ceramics with obviously lamellar structure is connected.

Automated summary

Freeze casting is used to prepare porous ceramics with applications in filtration, separation, insulation, energy storage, and bioengineering. In this study, porous silicon carbide ceramics are fabricated using a unidirectional freeze-casting process. The pore structure is investigated through micro-X-Ray computed tomography and the resulting ceramics exhibit a layered and interconnected porous structure. The pore sizes decrease and the number of channels increase with decreasing freezing temperatures. The ceramics have a maximum compressive strength of 1.97 MPa and a bimodal pore size distribution.