Abstract
Porous liquid-phase-sintered SiC (L-SiC) ceramics were successfully fabricated by hot press sintering (HP) at 1800 °C in argon, using Al2O3 and Y2O3 as oxide additions. By varying the starting coarse SiC particle size, the relationships between pore microstructures and flexural strength as well as gas permeability of porous L-SiC were examined. All the as-sintered samples possessed homogeneous interconnected pores. The porosity of porous L-SiC decreased from 34.0% to 25.9%, and the peak pore size increased from 1.1 to 3.8 μm as the coarse SiC particle sizes increased. The flexural strengths of porous L-SiC ceramics at room temperature and 1000 °C were as high as 104.3 ± 7.3 MPa and 78.8 ± 5.1 MPa, respectively, though there was a decrease in accordance with their increasing pore sizes and particle sizes. Moreover, their gas permeability increased from 1.4 × 10−14 m2 to 4.6 × 10−14 m2 with the increase of pore size in spite of their decreased porosity.
Highlights
Porous SiC ceramics have been wildly investigated because of their excellent flexural strength, superior chemical and thermal stability, outstanding thermal conductivity, low thermal expansion coefficient, large specific surface area, excellent corrosion resistance, and so on [1,2,3,4,5]
The particle size of coarse SiC powder was changed to control the microstructures of experiment, the particle size of coarse SiC powder was changed to control the microstructures of prepared porous liquid-phase-sintered SiC (L-SiC) ceramics
The microstructure and morphology of porous L-SiC ceramics were observed with a scanning electron microscopy (SEM, Phenom ProX, Phenom-World, Eindhoven, The Netherlands), and pore size distribution was measured using mercury intrusion porosimetry
Summary
Porous SiC ceramics have been wildly investigated because of their excellent flexural strength, superior chemical and thermal stability, outstanding thermal conductivity, low thermal expansion coefficient, large specific surface area, excellent corrosion resistance, and so on [1,2,3,4,5]. There are various studies on the fabrication methods of porous SiC ceramics, including the recrystallization [9], foaming-gel casting [4,10,11,12], gelation-freezing [13,14,15], in-situ reaction [16,17], sacrificing template [18], and sol-gel methods [19,20] In these fabrication methods, most of the reported porous SiC ceramics were solid-state sintered because of their better heat stability and corrosion resistance as a result of clear grain boundaries and the strong bonding interface between SiC grains [4,10,11,12,14,15].
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