Low-firing temperature method for producing Al2O3 bodies having enhanced chemical resistance

Abstract

The present invention includes a method for producing high-alumina bodies with superior chemical properties at reduced sintering temperatures. One form of the method includes the steps of providing an alumina powder precursor, adding about 2 wt. % magnesia powder precursor and about 2 wt. % titania powder precursor, mixing the resultant green powder precursor, pressing a green body from the green powder precursor, removing residual moisture and organic material from the green body, and firing the green body to about cone 13. The resulting high-alumina body has a substantially uniformly sized grain structure, is resistant to dissolution in molten aluminum, and has superior resistance to chemical attack over substantially the entire pH range.

What is claimed is:  
     
         1 . A method for producing high-alumina bodies at reduced sintering temperatures, comprising the steps of: 
 a) providing an alumina powder precursor;    b) adding about 1-10 wt. % magnesia powder precursor and 1-10 wt. % titania powder precursor to the alumina powder precursor to make a green powder precursor;    c) mixing the green powder precursor;    d) pressing a green body from the green powder precursor;    e) removing residual moisture and organic material from the green body; and    f) firing the green body to about cone  13 .    
     
     
         2 . The method of  claim 1  further comprising the step of between b) and d), adding a binder.  
     
     
         3 . The method of  claim 2  wherein the binder is an aqueous solution of about  3 % carboxymethylcellulose.  
     
     
         4 . The method of  claim 1  wherein the green body is fired in air.  
     
     
         5 . The method of  claim 1  wherein magnesia and titania are added in a substantially 50:50 ratio.  
     
     
         6 . The method of  claim 1  wherein magnesia and titania are added in a substantially  42 : 48  ratio.  
     
     
         7 . The method of  claim 1  wherein about 2 wt. % magnesia and about 2 wt. % titania are added.  
     
     
         8 . The method of  claim 1  wherein mixing is accomplished by wet ball milling with alumina media.  
     
     
         9 . The method of  claim 1  further comprising the step of between b) and d), adding a 3% aqueous solution of carboxymethylcellulose; wherein the green body is fired in air; wherein about 2 wt. % magnesia and about 2 wt. % titania are added in a substantially 42:48 ratio; and wherein mixing is accomplished by wet ball milling with alumina media.  
     
     
         10 . A method for producing high-alumina bodies having enhanced chemical stability at reduced sintering temperatures, comprising the steps of: 
 g) providing an alumina precursor;    h) adding about 1-10 wt. % magnesia precursor and 1-10 wt. % titania precursor to the alumina powder precursor;    i) mixing the alumina precursor;    j) forming the alumina precursor into a desired shape; and    k) firing the alumina shape to produce a substantially nonvitreous high alumina body.    
     
     
         11 . The method of  claim 10  wherein the high alumina body has a substantially uniform grain size.  
     
     
         12 . The method of  claim 10  wherein the alumina precursor is a powder and wherein the alumina precursor is formed into a desired shape by pressing.  
     
     
         13 . The method of  claim 10  wherein the alumina precursor is a slurry and wherein the alumina precursor is formed into a desired shape by casting.  
     
     
         14 . The method of  claim 10  wherein the alumina precursor is a slurry and wherein the alumina precursor is formed into a desired shape by spraying.  
     
     
         15 . The method of  claim 10  wherein the substantially non-vitreous high alumina body is part of a metal matrix composite.  
     
     
         16 . The method of  claim 15  wherein the metal matrix is aluminum.  
     
     
         17 . A high alumina body formed by the steps of: 
 aa) providing an alumina precursor;    bb) adding about 1-10 wt. % magnesia precursor and 1-10 wt. % titania precursor to the alumina powder precursor;    cc) mixing the alumina precursor;    dd) forming the alumina precursor into a desired shape; and    ee) firing the alumina shape to produce a substantially non-vitreous high alumina body.    
     
     
         18 . The body of  claim 17  further comprising the step of between bb) and dd), adding an approximately 3% aqueous solution of carboxymethylcellulose; wherein the green body is fired in air; wherein about 2 wt. % magnesia and about 2 wt. % titania are added in a substantially 42:48 ratio; and wherein mixing is accomplished by wet ball milling with alumina media.  
     
     
         19 . A chemically resistant high alumina body formed by the steps of: 
 gg) providing an alumina precursor;    hh) adding about 1-10 wt. % magnesia precursor and 1-10 wt. % titania precursor to the alumina powder precursor;    ii) mixing the alumina precursor;    jj) forming the alumina precursor into a desired shape; and    kk) firing the alumina shape to produce a substantially nonvitreous high alumina body.    
     
     
         20 . The body of  claim 19  further comprising the step of before ii) adding an approximately 3% aqueous solution of carboxymethylcellulose; wherein the high alumina is fired in air; wherein about 2wt. % magnesia and about 2 wt. % titania are added in a substantially 42:48 ratio; and wherein mixing is accomplished by wet ball milling with alumina media.