Method of Making Ceramic Articles with Multiple Distinct Regions of Distinct Density

Abstract

A method for producing ceramic articles with multiple distinct regions of density by blending pore formers of different types or amounts with ceramic particles to create multiple pore former/ceramic particle mixtures. The mixtures are placed in a divided die cavity, divider removed and subjected to compaction under pressure to produce a compacted billet. The compacted billet is thermally processed to volatilize organics from the billet and sinter the billet, creating a cohesive billet of ceramic having two or more regions of density.

1 . A method for producing a ceramic article having multiple distinct regions of density, the method comprising:
 blending a first pore former with a first ceramic powder to create a first powder mixture;   blending a second pore former with a second ceramic powder to create a second powder mixture;   placing first and second powder mixtures into separate cavities within a divided die cavity;   applying a compaction pressure to the first and second powder mixtures, thereby producing a compacted billet comprising adjacent portions of the first and second powder mixtures;   heating the compacted billet to a first temperature sufficient to volatilize organics including first and second pore formers from the compacted billet;   heating the compacted billet to a second temperature sufficient to densify the billet and produce the ceramic article with multiple distinct regions of density.   
     
     
         2 . The method of  claim 1  further comprising the step of adding a pressing aid to at least one of the first and second powder mixtures. 
     
     
         3 . The method of  claim 2  wherein the pressing aid comprises an aqueous acrylic emulsion binder. 
     
     
         4 . The method of  claim 1  wherein at least one of the first and second ceramic powders comprise a lead zirconate titanate (PZT) powder. 
     
     
         5 . The method of  claim 4  wherein the lead zirconate titanate (PZT) powder consists of approximately Pb 0..99 (Zr 0.95 Ti 0.05 ) 0.98 Nb 0.02 O 3 . 
     
     
         6 . The method of  claim 5  wherein the lead zirconate titanate powder comprises an average particle size of approximately five microns. 
     
     
         7 . The method of  claim 1  wherein the first pore former comprises polymethylmethacrylate. 
     
     
         8 . The method of  claim 7  wherein the first powder mixture comprises approximately 0.1 weight percent polymethylmethacrylate. 
     
     
         9 . The method of  claim 1  wherein the second pore former comprises microcrystalline cellulose. 
     
     
         10 . The method of  claim 9  wherein the second powder mixture comprises approximately 1.2 weight percent microcrystalline cellulose. 
     
     
         11 . The method of  claim 1  further comprising the steps of providing a die cavity divider and removing the die cavity divider prior to the step of applying the compaction pressure. 
     
     
         12 . The method of  claim 1  wherein the steps of heating to a first temperature and heating to a second temperature are performed as a single step. 
     
     
         13 - 22 . (canceled)