Monazite based blanket coatings for thermal protection systems

Abstract

Monazite or xenotime-based blanket coatings that stiffen ceramic fabrics without causing embrittlement at temperatures of at least as high as 2400° F. are provided. Methods for making the coatings are also provided. The methods comprise the synthesis of high purity, monazite and xenotime powders with the stoichiometric ratio of metal to phosphorous of about 1:1.

What is claimed is:  
     
         1 . A ceramic composite having high temperature stability, comprising: 
 a first ceramic material selected from the group consisting of monazites and xenotimes and having a stoichiometric ratio between a metal of the first ceramic material and a phosphate of the first ceramic material of about 1:1;    a second ceramic material combined with said first ceramic material to form the ceramic composite; and    one of said first and second ceramic materials forming a ceramic matrix with the other of said ceramic materials embedded in said ceramic matrix;    
     
     
         2 . The ceramic composite of  claim 1  wherein the metal of the first ceramic material is selected from the group consisting of lanthanum, cerium, yttrium, and combinations thereof.  
     
     
         3 . The ceramic composite of  claim 1  wherein the coating composition further comprises an inert powder.  
     
     
         4 . The ceramic composite of  claim 3  wherein the inert powder is Al 2 O 3 , zirconia, YAG, mullite, or compositions thereof.  
     
     
         5 . The ceramic composite of  claim 1  wherein the coating composition further comprises SiC additives.  
     
     
         6 . The blanket according to  claim 1 , wherein the monazite or xenotime is synthesized by forming a precipitate from an aqueous solution comprising a lanthanide salt and a phosphate, washing the precipitate with water, and washing the precipitate with an organic base with a pH of greater than about 12.  
     
     
         7 . The blanket according to  claim 6 , wherein the organic base is tetramethylammonium hydroxide.  
     
     
         8 . An insulating blanket having high temperature stability, comprising: 
 a ceramic fabric including ceramic fibers; and    a coating on the fibers of a first ceramic material selected from the group consisting of monazites and xenotimes and having a stoichiometric ratio between a metal of the first ceramic material and a phosphate of the first ceramic material of about 1:1.    
     
     
         9 . The blanket according to  claim 8 , wherein the monazite or xenotime is synthesized by forming a precipitate from an aqueous solution comprising a lanthanide salt and a phosphate, washing the precipitate with water, and washing the precipitate with an organic base with a pH of greater than about 12.  
     
     
         10 . The blanket according to  claim 9 , wherein the organic base is tetramethylammonium hydroxide.  
     
     
         11 . The blanket according to  claim 8 , wherein the coating further comprises a SIC additive.  
     
     
         12 . The blanket according to  claim 8 , wherein the coating further comprises an inert powder.  
     
     
         13 . The blanket according to  claim 8 , wherein the inert powder is Al 2 O 3 , zirconia, YAG, mullite, or compositions thereof.  
     
     
         14 . The blanket according to  claim 8 , wherein the metal further comprises lanthanum, cerium, yttrium, or combinations thereof.  
     
     
         15 . A mobile platform comprising: 
 a body having an area to be exposed to temperatures of at least about 2000 degrees Fahrenheit; and    an insulating blanket covering the area and having 
 a ceramic fabric including ceramic fibers; and  
 a coating on the fibers of a first ceramic material selected from the group consisting of monazites and xenotimes and having a stoichiometric ratio between a metal of the first ceramic material and a phosphate of the first ceramic material of about 1:1.  
   
     
     
         16 . The mobile platform according to  claim 15 , further comprising a re-entry vehicle.  
     
     
         17 . The mobile platform according to  claim 15 , wherein the monazite or xenotime is synthesized by forming a precipitate from an aqueous solution comprising a lanthanide salt and a phosphate, washing the precipitate with water, and washing the precipitate with an organic base with a pH of greater than about 12.  
     
     
         18 . The mobile platform according to  claim 17 , wherein the organic base is tetramethylammonium hydroxide.  
     
     
         19 . The mobile platform according to  claim 15 , wherein the coating further comprises a SIC additive.  
     
     
         20 . The mobile platform according to  claim 15 , wherein the coating further comprises an inert powder.  
     
     
         21 . The mobile platform according to  claim 15 , wherein the inert powder is Al 2 O 3 , zirconia, YAG, mullite, or compositions thereof.  
     
     
         22 . The mobile platform according to  claim 15 , wherein the metal further comprises lanthanum, cerium, yttrium, or combinations thereof.