Ceramic heating elements

Abstract

New methods are provided or manufacture ceramic resistive igniter elements that include sintering of the elements in the absence of substantially elevated pressures. Ceramic igniters also are provided that are obtainable from fabrication methods of the invention.

1 . A resistive ceramic heating element comprising: 
 prior to sintering, one or more ceramic materials having a mean particle size of 2.5 microns or less.    
     
     
         2 . The heating element of  claim 1  wherein the heating element comprises prior to sintering one or more metal oxides having a mean particle size of 2.5 microns or less.  
     
     
         3 . The ceramic heating element of  claim 1  wherein the heating element comprises prior to sintering alumina having a mean particle size of 2.5 microns or less.  
     
     
         4 . The heating element of  claim 1  wherein the one or more ceramic materials have a mean particle size of 2 microns or less.  
     
     
         5 . The heating element of  claim 1  wherein the one or more ceramic materials have a mean particle size of 1.5 microns or less.  
     
     
         6 . A method for producing a resistive heating element, comprising: 
 treating a ceramic composition at a first pressure; and thereafter    treating the ceramic composition at a second pressure that is greater than the first pressure to thereby densify the ceramic composition.    
     
     
         7 . The method of  claim 6  wherein prior to treatment at the first pressure the ceramic composition comprises one or more ceramic materials having a mean particle size of 2.5 microns or less.  
     
     
         8 . The method of  claim 6  wherein prior to treatment at the first pressure the ceramic composition the ceramic composition comprises one or more metal oxides having a mean particle size of 2.5 microns or less.  
     
     
         9 . The method of  claim 6  wherein prior to treatment at the first pressure the ceramic composition comprises alumina having a mean particle size of 2.5 microns or less.  
     
     
         10 . The method of  claim 6  wherein the first and second pressures differ by at least 1000 psi.  
     
     
         11 . The method of  claim 6  wherein the second pressure is about 5000 psi or less.  
     
     
         12 . The method of  claim 6  wherein the first pressure is about 1000 psi or less.  
     
     
         13 . The method of  claim 6  wherein the first pressure is about 250 psi or less.  
     
     
         14 . The method of  claim 6  wherein the first and second pressures are applied as a gas phase sintering process.  
     
     
         15 . The method of  claim 6  wherein the ceramic igniter element is formed of a composition that has less than 10 volume percent silicon carbide.  
     
     
         16 . The method of  claim 6  wherein the ceramic element comprises two or more regions of differing resistivity.  
     
     
         17 . The method of  claim 6  wherein the ceramic element comprises three or more regions of differing resistivity.  
     
     
         18 . A ceramic igniter element obtainable by the method of  claim 6 .  
     
     
         19 . A method of igniting gaseous fuel, comprising applying an electric current across an igniter of  claim 18 .  
     
     
         20 . A heating apparatus comprising an igniter of  claim 18.