Graphite blending method for ceramic shrinkage control

Abstract

A method for green-to-fired shrinkage control in honeycomb ceramic article manufacture, including: measuring, prior to mixing, the particle size distribution properties of at least one fine particle size graphite pore former ingredient of a provided ceramic source batch mixture; calculating the expected shrinkage of the green body to the fired ceramic article based on the measured particle size distribution properties of the at least one fine particle graphite pore former; making the honeycomb ceramic article; measuring the shrinkage of the resulting fired honeycomb ceramic article; and adjusting the ceramic source batch mixture in a subsequent batch material schedule, as defined herein, wherein the adjusted ceramic source batch mixture provides finished honeycomb ceramic articles having controlled green-to-fired shrinkage.

What is claimed is: 
     
         1 . A method for green-to-fired shrinkage control in honeycomb ceramic article manufacture, comprising:
 measuring, prior to mixing, the particle size distribution properties of at least one fine particle graphite pore former ingredient of a provided ceramic source batch mixture;   calculating the expected shrinkage of the green body to the fired ceramic article based on the measured particle size distribution properties of the at least one fine particle graphite pore former;   making the honeycomb ceramic article comprising:
 preparing an extruded green body from the provided ceramic source batch mixture having the at least one fine particle graphite pore former having the measured particle size distribution properties; and 
 firing the extruded green body to form the honeycomb ceramic article; 
   measuring the shrinkage of the resulting fired honeycomb ceramic article; and   adjusting the ceramic source batch mixture in a subsequent batch material schedule according to:
 if the measured shrinkage is greater than about 0.15 relative % positive deviation from the calculated expected shrinkage, then subtract 0.5 wt % from the fine particle size graphite content; or 
 if the measured shrinkage is greater than about 0.15 relative % negative deviation from the calculated expected shrinkage then add 0.5 wt % to the fine particle size graphite content. 
   
     
     
         2 . The method of  claim 1  further comprising:
 extruding the adjusted batch mixture to form an extruded green body; and 
 firing the extruded green body to form the ceramic article having controlled shrinkage. 
 
     
     
         3 . The method of  claim 2  wherein the controlled shrinkage is less than about +0.15 relative % to about −0.15 relative % from the expected shrinkage. 
     
     
         4 . The method of  claim 1  wherein the measured shrinkage of the fired honeycomb ceramic article measures a change in at least one of: the diameter of the article, the major axis of the article, or a combination thereof. 
     
     
         5 . The method of  claim 1  wherein the at least one fine particle size graphite comprises a particle size distribution having a d50 of 3 to 5 microns, and a d90 less than 8 microns. 
     
     
         6 . The method of  claim 1  wherein calculating the expected shrinkage (dS) of the green body to the fired ceramic article is accomplished according to the formula:
     dS=dFG/A    
 
       where dS the expected shrinkage if the fine graphite is held constant, dFG is the change in the amount of the at least one fine particle size graphite in the batch mixture, and A is a scale factor which depends on the other batch components and the attributes of the fine particle size graphite selected. 
     
     
         7 . The method of  claim 1  wherein the provided ceramic source batch mixture has a shrinkage variability of from about +0.5% to about −0.5% from a nominal value over a production period of about 3 months to 2 years. 
     
     
         8 . The method of  claim 1  wherein the ceramic source batch mixture having the at least one fine particle size graphite pore former further includes at least one of:
 an aluminum oxide source; 
 a silica source; 
 a titanium oxide source; 
 a lanthanum oxide source; 
 a starch containing pore former; 
 a coarse graphite pore former; 
 and mixtures thereof. 
 
     
     
         9 . The method of  claim 1  further comprising:
 if the expected shrinkage is neither greater than positive 0.15 relative % or greater than negative 0.15 relative % of the penultimate calculated expected shrinkage, then use the penultimate batch sheet for the next batch material schedule. 
 
     
     
         10 . A method for green-to-fired shrinkage control in honeycomb ceramic article manufacture, comprising:
 determining the green-to-fired shrinkage of a green body when fired to a fired ceramic article, wherein the green body is prepared from a ceramic source batch mixture having the at least one fine particle graphite pore former having a measured particle size distribution;   comparing the determined green-to-fired shrinkage of the resulting fired ceramic article with an expected shrinkage in the fired ceramic, wherein the expected shrinkage of the fired ceramic has a positive deviation or negative deviation of less than 0.15 relative %;   adjusting the weight % of the at least one fine particle graphite pore former having the measured particle size distribution in the ceramic source batch mixture if the determined green-to-fired shrinkage is greater than the expected shrinkage; and   firing the green body to form the honeycomb ceramic article having controlled shrinkage.   
     
     
         11 . The method of  claim 10  wherein the controlled shrinkage of the honeycomb ceramic article is a shrinkage deviation of less than about 0.15 relative %. 
     
     
         12 . The method of  claim 10  wherein adjusting the weight % of the at least one fine particle graphite pore former comprises adding or subtracting graphite pore former from the batch schedule in an amount of about 0.5 weight % or more. 
     
     
         13 . The method of  claim 10  wherein the at least one fine particle graphite pore former comprises a mixture of two or more fine particle graphite pore formers having different measured particle size distributions. 
     
     
         14 . The method of  claim 10  wherein adjusting the weight % of the at least one fine particle graphite pore former in the source batch mixture is according to:
 if the expected shrinkage is more negative than about negative 0.15 relative %, then adding fine particle size graphite to the batch schedule; or 
 if the expected shrinkage is more positive than about positive 0.15 relative %, then subtracting fine particle size graphite from the batch schedule; and 
 if the expected shrinkage is less negative than about negative 0.15 relative % or less positive than about positive 0.15 relative %, then maintaining the fine particle size graphite content in the batch schedule at a constant level. 
 
     
     
         15 . The method of  claim 14  wherein the adjusting the weight % of the at least one fine particle graphite pore former comprises adding or subtracting graphite pore former from the batch schedule in an amount of about 0.5 weight % to about 2.5 weight %. 
     
     
         16 . The method of  claim 10  wherein the ceramic source batch mixture further comprises at least one coarse particle size graphite pore former.