A reverse particle grading strategy for design and fabrication of porous SiC ceramic supports with improved strength

Porous ceramics usually requires high mechanical strength and maximized porosity simultaneously, while for conventional particle grading strategy it is highly challenging to meet both demands. To this end, a reverse particle grading strategy was developed based on the linear packing model by unusually introducing coarse particles (d₅₀ = 16 μm) into fine particles (d₅₀ = 5 μm) matrix. Followed by the extrusion and sintering process, tubular porous SiC ceramic supports with improved mechanical strength were successfully fabricated. Effects of coarse particles on the rheology properties of the ceramic paste, and macroscopic properties and microstructure of SiC supports were systematically investigated. With the increasing content of coarse SiC particles to 30 wt%, the pressure generated in extrusion decreased from 5.5 ± 0.2 MPa to 1.3 ± 0.1 MPa. Notably, the bending strength of tubular supports increased from 36.6 ± 5.6 MPa to 49.1 ± 4.5 MPa when incorporating 20 wt% of coarse powders. The notable improved mechanical strength was attributed to the distribution of coarse particles that prolonged the route of crack deflection. Also, the optimized tubular supports showed an average pore size of 1.2 ± 0.1 μm and open porosity of 45.1 ± 1.6 % and water permeability of 7163 ± 150 L·m^-2·h^-1·bar^-1 and good alkali and acid corrosion resistances. Significantly, the strategy was proved to be feasible in the scale-up fabrication of 19-channel SiC tubular porous ceramic supports.