US Patent 7138084 Refractory articles

A filter for molten metal is an open-pored porous material comprising particles of refractory material embedded in and bonded together by a carbon matrix bonding material. The filter can be made by forming a porous article from refractory particles, e.g. refractory oxide, carbide or graphite, and a carbon-rich binder, e.g. tar, pitch or an organic (preferably aromatic) polymer that degrades to form carbon on pyrolysis, and then firing the porous article to generate the carbon matrix in which the refractory particles are embedded. The porous article is preferably made by coating a reticulated polyurethane foam with binder and refractory particles, and firing at preferably no higher than 800° C.