Refractory composition and process for forming article therefrom

Abstract

A refractory composition and processes for manufacture are provided where the compositions possess improved refractory alkali resistance and superior handling properties. Compositions and processes for their manufacture may include a plurality of ceramic particles and a binder sintered to the particles wherein the binder includes crystalline aluminum orthophosphate distributed as the result of an in situ reaction of aluminum metaphosphate with alumina. Kits provided according to the invention provide materials for use in manufacture of a composition where the kit includes aluminum metaphosphate and a nonfacile additive.

1 . A refractory composition comprising:
 a plurality of aggregate ceramic particles; and   a binder sintered to said plurality of aggregate ceramic particles, said binder comprising crystalline aluminum orthophosphate distributed in said binder as the result of reaction of aluminum metaphosphate with alumina.   
     
     
         2 . The composition of  claim 1  wherein said plurality of aggregate ceramic particles comprise bauxite particles. 
     
     
         3 . The composition of  claim 1  wherein said plurality of aggregate ceramic particles includes at least one of silicon carbide, fumed silica, or mullite. 
     
     
         4 . The composition of  claim 1  wherein said crystalline aluminum orthophosphate has a crystal structure of berlinite. 
     
     
         5 . The composition of  claim 1  wherein said crystalline aluminum orthophosphate is devoid of an amorphous glass phase. 
     
     
         6 . The composition of  claim 1  further comprising steel fiber filler. 
     
     
         7 . The composition of  claim 1  further comprising a nonfacile additive of calcium aluminate cement, sodium silicate, polyphosphate, or organic salts. 
     
     
         8 . The composition of  claim 1  wherein the composition has a density greater than or equal to 90% of theoretical and a cold crush strength of greater than 100 N/mm 2 . 
     
     
         9 . A process of forming a refractory article comprising:
 mixing aluminum metaphosphate particulate with Al 2-x MO 3  in the presence of less than 10 slurry weight percent of water or an organic solvent to form a mixture;   heating said mixture to a temperature and for a time sufficient to induce the reaction
   Al(PO 3 ) 3 +Al 2-x MO 3 →Al Al 2-x MPO 4   (II)
 
   where M is Sb, Bi, B, Cr (III), Er, Gd (III), In (III), Ni (III), Rh (III), Sm (III), Sc (III), Tb (III), Ti (III), W (III), V (III), Yb (III), or Y (III); and x is a number between 0 and 2, inclusive.   
     
     
         10 . The process of  claim 9  wherein the temperature is greater than 800° Celsius. 
     
     
         11 . The process of  claim 9  further comprising mixing a plurality of aggregate particles with said aluminum metaphosphate particulate and Al 2-x MO 3 . 
     
     
         12 . The process of  claim 9  further comprising adding at least one additive of calcium aluminate cement, sodium silicate, or polyphosphate to said mixture prior to said heating. 
     
     
         13 . The process of  claim 9  further comprising pouring said mixture into a mold having a shape complementary to the article and allowing the mixture to dry to form a piece of greenware; and heating the greenware to induce said reaction. 
     
     
         14 . The process of  claim 13  wherein said mold is a plaster mold. 
     
     
         15 . The process of  claim 9  further comprising embedding steel fibers within the mixture. 
     
     
         16 . A kit for producing a refractory binder comprising aluminum metaphosphate and a nonfacile additive together with instructions to combine aluminum metaphosphate with alumina and less than 10 slurry percent water or organic solvent for casting and then firing at a temperature above 800° Celsius. to form aluminum orthophosphate as a continuous binder matrix phase. 
     
     
         17 . The kit of  claim 16  further comprising a facile additive. 
     
     
         18 . The kit of  claim 16  wherein said nonfacile additive comprises calcium aluminate cement. 
     
     
         19 . The kit of  claim 16  wherein said nonfacile additive comprises sodium silicate. 
     
     
         20 . The kit of  claim 16  wherein said nonfacile additive comprises sodium polyphosphates. 
     
     
         21 . The kit of  claim 16  further comprising steel fiber filler.