Reduced strain refractory ceramic composite and method of making

Abstract

A composition is disclosed comprising a fine zircon component having a median particle size of less than 5 μm, a medium zircon component having a median particle size of from 5 μm to 15 μm, and a sintering aid, wherein the composition, after firing, has a strain rate of less than about 1×10 −6 /hr. A method for making a green body comprising contacting a fine zircon component having a median particle size of less than 5 μm, a medium zircon component having a median particle size of from 5 μm to 15 μm, and a sintering aid, and then forming the mixture into a desired shape is disclosed.

1 . (canceled) 
   
   
       2 . The ceramic article of  claim 13 , wherein the composition further comprises a coarse zircon component having a median particle size of greater than 15 μm. 
   
   
       3 . (canceled) 
   
   
       4 . The ceramic article of  claim 13 , wherein the sintering aid comprises a titanium containing compound. 
   
   
       5 . (canceled) 
   
   
       6 . The ceramic article of  claim 13 , wherein the sintering aid is from greater than 0 wt. % to about 1 wt. % of the composition. 
   
   
       7 . The ceramic article of  claim 13 , wherein the sintering aid is from greater than 0 wt. % to about 0.5 wt. % of the composition. 
   
   
       8 . The ceramic article of  claim 13 , wherein the fine zircon component comprises from greater than 10 wt. % to about 60 wt. % of the composition. 
   
   
       9 . The ceramic article of  claim 13 , wherein the fine zircon component comprises from about 40 wt. % to about 60 wt. % of the composition. 
   
   
       10 . The ceramic article of  claim 13 , wherein the fine zircon component has a median particle size of from about 0.1 μm to about 2 μm and the coarse zircon component has a median particle size of from 15 μm to about 25 μm. 
   
   
       11 . The ceramic article of  claim 13 , wherein the fine zircon component has median particle size of from about 0.1 μm to about 2 μm and comprises from about 40 wt. % to about 60 wt. % of the composition; wherein coarse zircon component has a median particle size of from 15 μm to about 25 μm; and wherein the sintering aid comprises from greater than 0 wt. % to about 0.5 wt. % of the composition and comprises a titanium containing compound. 
   
   
       12 . (canceled) 
   
   
       13 . A ceramic article made by forming and firing a green body, the green body having a composition comprising:
 a) a fine zircon component having a median particle size of less than 5 μm;   b) a medium zircon component having a median particle size of from 5 μm to 15 μm; and   c) a sintering aid;   wherein the ceramic article has a strain rate of less than about 1×10 −6 /hr.   
   
   
       14 . The ceramic article of  claim 13 , having a bulk density of greater than about 4.25 g/cc. 
   
   
       15 . The ceramic article of  claim 13 , wherein the ceramic article is in the form of an isopipe. 
   
   
       16 . (canceled) 
   
   
       17 . A method for making a green body comprising:
 a) contacting a fine zircon component having a median particle size of less than 5 μm, a medium zircon component having a median particle size of from 5 μm to 15 μm, and a sintering aid to form a mixture; and then   b) forming the mixture into a desired shape.   
   
   
       18 . The method of  claim 17 , wherein step a) further comprises contacting with a coarse zircon component having a median particle size of greater than 15 μm. 
   
   
       19 . The ceramic article of  claim 13 , wherein the sintering aid comprises at least one oxide or salt of titanium, iron, calcium, yttrium, niobium, neodymium, or a combination thereof. 
   
   
       20 . The ceramic article of  claim 13 , wherein the forming comprises an isostatic pressing process. 
   
   
       21 . The ceramic article of  claim 13 , wherein the firing comprises firing the desired shape at a time and temperature sufficient to form an article having a strain rate of less than about 1×10 −6 /hr. 
   
   
       22 . The method of  claim 17 , further comprising, in step a), contacting at least one of the fine zircon component, the medium zircon component, or the sintering aid with at least one of methyl cellulose, water, glycerol, or a combination thereof. 
   
   
       23 . A green body made by the method of  claim 17 . 
   
   
       24 . An article made by the method of  claim 21 . 
   
   
       25 . The ceramic article of  claim 13 , wherein the medium zircon component comprises from about 20 wt. % to about 60 wt. % of the composition. 
   
   
       26 . (canceled) 
   
   
       27 . The ceramic article of  claim 13 , wherein the medium zircon component comprises from about 10 wt. % to about 60 wt. % of the composition; and
 the fine zircon component comprises from greater than 10 wt. % to about 60 wt. % of the composition   
   
   
       28 . A fusion draw process for making glass sheets using the isopipe according to  claim 15 .