Porous CaSiO 3 ceramics were prepared via a solid-state reaction method using CaCO 3 and SiO 2 as raw materials and active carbon as a pore-forming agent. The results indicated that porous CaSiO 3 ceramics could be obtained under a low sintering temperature of 1320 °C. The addition of active carbon significantly affected the volume density, microstructure, pore size distribution and mechanical strength of porous CaSiO 3 ceramics. With the increase of active carbon content, the volume density decreased, meanwhile the pore size and porosity increased gradually. Besides, the three-point bending tests demonstrated that the mechanical strength was decreased with increasing active carbon content. However, all the porous ceramics still exhibited high mechanical strength. These results implied that the increase of active carbon content not only enlarged the pore size and enhanced the porosity, but also kept a remarkable mechanical strength of porous CaSiO 3 ceramics. Therefore, these rationally designed CaSiO 3 porous ceramics will be a highly potential material in various applications due to its high mechanical strength, low sintering temperature and narrow pore size distribution.
Porous gelcasted and solid-state-sintered SiC (S-SiC) ceramics with significantly improved connectivity were successfully prepared through the synergistic pore-forming mechanism of direct foaming and particle packing, using fine (D 50 = 0.5 μm) and coarse (D 50 = 5.0 μm) graded SiC powders as the main raw materials. As the proportion of coarse SiC powder increased, the viscosities of aqueous SiC-B 4 C-C slurries sharply decreased, which thus flourished foaming and enlarged bubble-derived-pore diameter in porous S-SiC ceramics, accompanied with the increased amount and size of window. Moreover, abundant particle-packing pores in struts of bubble-derived pores were also formed and even interconnected with each other at 60 wt% of coarse SiC powder. Besides, there was a remarkable increase in porosity from 61.0% to 81.7% and accordingly a significant decline in density from 1.24 g cm −3 to 0.58 g cm −3 as the content of coarse SiC powder increased. The optimized multiple pore microstructures resulted in an amazing nitrogen gas permeability of 1.78×10 −11 m 2 under the condition of an excellent compressive strength of 10.8 ± 2.7 MPa.
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