Combining material extrusion and in-situ reaction bonding technique for fabricating light and strong hierarchical porous mullite-bonded SiC structures

Novel light and strong hierarchical porous mullite-bonded SiC structures with total porosity ranging from 68 % to 95 % were fabricated by combining material extrusion (MEX) and in-situ reaction bonding technique. These structures comprise three porosity families and wide porosity hierarchization over four orders of magnitude in length scales. The pore parameters were precisely controlled by the nozzle path and starch (as a poreforming agent) content. The sintering temperature effect on phase composition, porosity, sintering shrinkage, and mechanical properties was systematically investigated. As the SiC powders were sintered at 1550 °C, they were compactly bonded by mullite and cristobalite necks. The single filaments demonstrated a flexural strength of 74 MPa at a porosity of 35 %. The hierarchical porous mullite-bonded SiC lattice structure with a total porosity of 69 % was near-net-shape sintered and exhibited a compressive strength as high as 41 MPa. Such structures are highly promising for wide applications such as electromagnetic shielding, burners, membrane supports, porous burners, filters, thermal insulation , catalyst supports, etc.