Surface protection of porous ceramic bodies

A method of protecting the surface of a porous ceramic body, comprising the steps of:

• furnishing a body made of a mass of fired fibers of a first ceramic material and having porosity extending through at least a portion of the body adjacent to a first surface of the body;
• preparing a slurry of a mixture comprising
• a ceramic powder made of a second ceramic material, and
• a binding agent comprising silica particles;
• impregnating the slurry into the first surface of the body so that substantially all of the slurry enters the porosity of the body and substantially none of the slurry resides on the first surface;
• drying the slurry in place within the porosity of the body to leave a mixture of ceramic powder and binding agent within the porosity;
• and
• firing the mixture of ceramic powder and binding agent to cause the binding agent to bind the ceramic powder to the interior of the porosity of the body, so that substantially none of the second ceramic material and silica-containing binding agent lies on the first surface.

A method for the in situ application of surface protecting material to insulative ceramic tiles having porosity extending through at least a portion of the tile adjacent an outer surface thereof, said method comprising the steps of:

• applying a slurry comprising a mixture of a ceramic powder and a binding agent comprising silica particles to the outer surface of an insulative ceramic tile affixed to a surface of an aircraft or spacecraft such that the slurry enters the porosity of the tiles and substantially none of the slurry resides on the outer surface of the tile;
• drying the slurry in place within the porosity of the tile to leave a mixture of ceramic powder and binding agent within the porosity;
• and
• heating the slurry to cause the binding agent to bind the ceramic powder to the interior of the porosity of the tile.

A method of protecting the surface of a porous ceramic body, comprising the steps of:

• furnishing a body made of a first ceramic material and having porosity extending through at least a portion of the body adjacent to a first surface of the body;
• applying to the first surface of the body a slurry comprising a ceramic powder made of a second ceramic material and a binding agent comprising silica particles so that substantially all of the slurry enters the porosity of the body and substantially none of the slurry resides on the first surface;
• drying the slurry in place within the porosity of the body to leave a mixture of ceramic powder and binding agent within the porosity;
• and
• firing the mixture of ceramic powder and binding agent to cause the binding agent to bind the ceramic powder to the interior of the porosity of the body, so that substantially none of the second ceramic material and silica-containing binding agent lies on the first surface.