Abstract: A metal casting mold formed of a ceramic material. The mold is reusable and is formed of a crystalline ceramic whose coefficient of thermal expansion (in the range 0.degree. to 1000.degree. C.) is between about 0 and 15.times.10.sup.-7 /.degree.C./ The mold interior surface includes at least one projection extending towards the mold cavity. The projection is provided with a release (draft) angle of about 6.degree., tapering away from the base of the projection. Upon pouring, the molten metal surrounds at least a portion of the projection. Upon cooling within the mold, shrinkage of the metal casting against the tapered sides of the projection forces the casting along the projection, toward the latter's tapered end and away from the mold interior surface and thus partially out of the mold cavity. A method of making the ceramic mold of this invention is also disclosed.

Abstract: An improved method of modifying a honeycombed body having a multiplicity of open-ended cells extending therethrough between opposite face ends of the body to produce therein a multiplicity of flow paths for at least two and possibly three separate fluids. For accommodating two fluids, selected columns of cells within the honeycombed body are provided with openings near at least one face end for first fluid flow through one or two longitudinal, opposed boundary surfaces and through inner cell walls parallel to the cell axes while the open-ends of such columns on a face end perpendicular to the selected cell axes are sealed against fluid flow. Second fluid flow is through the unselected columns of cells parallel to and either in the direction of or counter to the first fluid flow. Specifically, the invention provides an improved method for sealing the selected columns of cells on face ends of the body.