Gelcasting of silicon carbide based on gelation of sodium alginate

A novel gel-casting process by sodium alginate gelation is presented. Solidified agent and chelator are added into sodium alginate solution simultaneously, thus the gelation between calcium ions and sodium alginate is avoided in this stage due to the chelate complex formed from the chelator and solidified agent (calcium salt). By adding hexanedioic acid, free calcium ions are released from the chelate complexes and react with sodium alginate, forming a three-dimensional network. Therefore, silicon carbide particles are held in this three-dimensional network and the slurry is consolidated. Green body with bending strength of ∼3 MPa, perfect surface and homogeneous microstructure has been produced by this process.