Porous ceramic composite with dense surface

Claim 1

A method for making a self-supporting ceramic composite article having a porous core bearing a dense surface layer formed integrally with said core, comprising the steps of: (a) preparing a preform comprising a filler material and a parent metal distributed through said filler material and wherein the volume percent of parent metal is sufficient to form a volume of oxidation reaction product which exceeds the total spatial volume available within said preform; (b) melting said parent metal in the presence of an oxidant and reacting the resultant molten parent metal on contact therewith to form an oxidation reaction product; (c) transporting said molten parent metal within said oxidation reaction product towards said oxidant to continue forming oxidation reaction product within said preform thereby substantially filling said total spatial volume, and concurrently forming voids substantially throughout said preform which at least partially inversely replicate the geometry of said parent metal; (d) continuing said reaction for a time sufficient to transport molten parent metal through said oxidation reaction product towards said oxidant and to at least one surface of said preform to form a dense surface layer of oxidation reaction product on said at least one surface, said dense surface layer being substantially free of voids and (e) recovering said ceramic composite article.

Claim 2

A method for making a self-supporting ceramic composite article having a porous core bearing a dense surface layer formed integrally with said core, comprising the steps of: (a) preparing a preform comprising a filler material and a parent metal distributed through said filler material and wherein the volume percent of parent metal is sufficient to form a volume of oxidation reaction product which exceeds the total spatial volume available within said preform; (b) melting said parent metal in the presence of an oxidant and reacting the resultant molten parent metal on contact therewith to form an oxidation reaction product; (c) transporting said molten parent metal within said oxidation reaction product towards said oxidant to continue forming oxidation reaction product within said preform thereby substantially filling said total spatial volume, and concurrently forming voids substantially throughout said preform which at least partially inversely replicate the geometry of said parent metal; (d) continuing said reaction for a time sufficient to transport molten parent metal through said oxidation reaction product towards said oxidant and to at least one surface of said preform to form a dense surface layer of oxidation reaction product on said at least one surface, said dense surface layer being substantially free of voids and (e) recovering said ceramic composite article.

Claim 5

The method according to any of claims 1, 2 or 3 wherein said filler material is substantially nonreactive under the process conditions.

Claim 6

The method according to any of claims 1, 2 or 3 wherein said preform further comprises (i) a reactive filler, and (ii) a metallic compound reducible by said molten parent metal in an oxidation-reduction reaction, said parent metal being present in said preform in a stoichiometric excess over said metallic compound, said method further comprising the step of heating said preform to a reaction-effective temperature to initiate said oxidation-reduction reaction and in the absence of any substantial atmospheric oxidation of said parent metal prior thereto to form an oxidation-reduction product substantially throughout said preform.

Claim 7

The method according to any of claims 1, 2 or 3 wherein said preform comprises a generally shape-sustaining preform having a pore volume of at least about 5%.

Claim 11

The method of claim wherein said parent metal comprises aluminum and a dopant source associated therewith, said dopant source comprising a material selected from the group consisting of magnesium, zinc, silicon, germanium, tin, lead, boron, sodium, lithium, calcium, phosphorus, yttrium, the rear earth metals, and mixtures thereof.