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

Porous ceramics usually require high mechanical strength and maximized porosity simultaneously, while for conventional particle grading strategies, 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 a fine particle (d₅₀ = 5 μm) matrix. Following the extrusion and sintering process, tubular porous SiC ceramic supports with improved mechanical strength were successfully fabricated. The effects of coarse particles on the rheological properties of the ceramic paste and the macroscopic properties and microstructure of the SiC supports were systematically investigated. With an increase in the content of coarse SiC particles to 30 wt%, the pressure generated during extrusion decreased from 5.5±0.2 to 1.3±0.1 MPa. Notably, the bending strength of the tubular supports increased from 36.6±5.6 to 49.1±4.5 MPa when 20 wt% coarse powder was incorporated. The notably improved mechanical strength was attributed to the distribution of coarse particles that prolonged the route of crack deflection. Additionally, the optimized tubular supports had an average pore size of 1.2±0.1 μm, an open porosity of 45.1%±1.6%, and a water permeability of 7163±150 L/(m²·h·bar) as well as good alkali and acid corrosion resistance. Significantly, the strategy was proven to be feasible for the scale-up fabrication of 19-channel SiC tubular porous ceramic supports.