High Temperature Amorphous Composition Based on Aluminum Phosphate

Abstract

A composition providing thermal, corrosion, and oxidation protection at high temperatures is based on a synthetic aluminum phosphate, in which the molar content of aluminum is greater than phosphorus. The composition is annealed and is metastable at temperatures up to 1400° C.

1 . A method for protecting a substrate from corrosion and oxidation at elevated temperatures, said method comprising the steps of applying a precursor solution to said substrate, said precursor solution comprising phosphorus pentoxide and an aluminum salt, wherein the ratio of aluminum to phosphorus is greater than one to one, and thereafter drying annealing said solution on said substrate. 
     
     
         2 . A metastable material comprising an aluminum phosphate composition having the formula Al 1+x PO 4+3x/2 , wherein x is about 0 to about 1.5, said composition having structural components absorbing radiation in the infra red spectrum at about 795 cm −1  to about 850 cm −1 , said components present at temperatures of at least about 1000° C. 
     
     
         3 . The material of  claim 2  wherein x is about 0. 
     
     
         4 . The material of  claim 3  wherein x is about 0.1 to about 1.0. 
     
     
         5 . The material of  claim 4  wherein said material is substantially amorphous. 
     
     
         6 . The material of  claim 4  wherein said material is metastable at temperatures at least about 1200° C. 
     
     
         7 . The material of  claim 4  further including crystalline particles. 
     
     
         8 . The material of  claim 7  wherein said crystalline particles are ErPO 4 . 
     
     
         9 . An aluminum phosphate product having Al—O—Al structural moieties absorbing radiation in the infra red spectrum at about 795 cm −1  to about 850 cm −1 , said product obtainable by mixing an alcoholic solution of phosphorus pentoxide with a solution of an aluminum salt, and heating the admixture. 
     
     
         10 . The product of  claim 9  wherein said product is substantially amorphous. 
     
     
         11 . The product of  claim 9  further including crystalline particles. 
     
     
         12 . The product of  claim 11  wherein said particles are crystalline ErPO 4  inclusions prepared by incorporating an erbium salt with said aluminum salt solution. 
     
     
         13 . The product of  claim 9  further including metal oxide particles, said particles selected from the group consisting of Group IIIA and IIIB-VIB metal oxides, said particles in an amount sufficient to modify the thermal expansion coefficient of said product.