Abstract: An article has at its surface a nonmetallic ceramic form of a cation reactive with phosphate ion to form a ceramic phosphate, such as an oxide of a cation selected from the group consisting of beryllium, aluminum, iron, magnesium, calcium, thorium, barium, zirconium, zinc, silicon, and mixtures thereof. A source of reactive phosphate ions, such as concentrated phosphoric acid or monoaluminum phosphate, is applied to the surface of the article. The surface of the article is thereafter heated to cause the nonmetallic ceramic form of the cation and the source of the reactive phosphate ions to react together, producing a phosphate-bonded hard layer at the surface of the article.

Abstract: A ceramic composition for the repair of porous ceramic bodies comprises a ceramic material having cations which are reactive with phosphate ions, a source of reactive phosphate ions, and filler. An aqueous slurry of the ceramic composition is prepared and applied to the damaged region of a porous ceramic body. The slurry mixture is dried within the damaged region of the porous ceramic body and heated to bind the mixture together and to bond the mixture to the porous ceramic body within the damaged region. The method of the invention allows for the in situ repair of ceramic materials without removing them from their supporting structure and can be used in the repair of ceramic tiles for spacecraft and aircraft.

Abstract: A surface of a porous ceramic body is protected by binding ceramic particles entirely within the subsurface porosity of the body adjacent to the surface but not present as a separately identifiable surface layer. To produce such a protective layer, a slurry of a mixture of a ceramic powder and a silica-containing binding agent is first prepared. The slurry is impregnated into the surface of the body so that all of the slurry enters the porosity of the body and substantially none of the slurry resides on the surface. The slurry is dried in place, and the residual solids are fired to bind the ceramic powder to the interior walls of the porosity. Drying and firing can be accomplished at intermediate temperatures of about 700-1000.degree. F. using heat lamps, so that the surface protection can be accomplished without removing the ceramic body from a larger structure.

Abstract: A surface of a porous ceramic body is protected by binding ceramic particles entirely within the subsurface porosity of the body adjacent to the surface but not present as a separately identifiable surface layer. To produce such a protective layer, a slurry of a mixture of a ceramic powder and a silica-containing binding agent is first prepared. The slurry is impregnated into the surface of the body so that all of the slurry enters the porosity of the body and substantially none of the slurry resides on the surface. The slurry is dried in place, and the residual solids are fired to bind the ceramic powder to the interior walls of the porosity. Drying and firing can be accomplished at intermediate temperatures of about 700.degree.-1000.degree. F. using heat lamps, so that the surface protection can be accomplished without removing the ceramic body from a larger structure.