Preparation of Boron Carbide Porous Ceramic by Gel-casting

Boron carbide (B₄C) preform was prepared via gel-casting with macromolecule agarose as a gel system and polyacrylic acid as a dispersant. The preform was sintered at 1 800-2 000℃ to obtain a porous B₄C ceramic. The results show that the maximum solid loading of B₄C slurry with a lower viscosity is 45% (in volume fraction) at pH value of 7.5 and dispersant content of 0.15% (in volume fraction). The open porosity decreases with increasing sintering temperature, and the open porosity is 100% at 1 800℃. The pore size distribution of porous ceramics presents a unimodal model with the average pore size of 1 μm. The flexural strength of B₄C porous ceramics is 60 MPa, which could be used for the subsequent reactive melt infiltration. The expected ZrC/ZrB₂ composite is obtained when Zr infiltrates into the porous B₄C ceramic. The microstructure of the composite is layered in the infiltration direction.